text:
|Publication number
|Publication type
|Application number
|Publication date
|Apr 6, 1993
|Filing date
|Mar 2, 1992
|Priority date
|May 25, 1988
|Fee status
|Publication number
|Stacey I. Zones, Dennis L. Holtermann, Robert A. Innes
|Original Assignee
|Chevron Research And Technology Company
|Export Citation
|BiBTeX, EndNote, RefMan
|Patent Citations (7), Referenced by (34), Classifications (22), Legal Events (3)
|External Links: USPTO, USPTO Assignment, Espacenet
This application is a continuation of application Ser. No. 198,414, filed May 25, 1988 now abandoned.
Natural and synthetic zeolitic crystalline aluminosilicates are useful as catalysts and adsorbents. These aluminosilicates have distinct crystal structures which are demonstrated by X-ray diffraction. The crystal structure defines cavities and pores which are characteristic of the different species. The adsorptive and catalytic properties of each crystalline aluminosilicate are determined in part by the dimensions of its pores and cavities. Thus, the utility of a particular zeolite in a particular application depends at least partly on its crystal structure.
Because of their unique molecular sieving characteristics, as well as their catalytic properties, crystalline aluminosilicates are especially useful in such applications as gas drying and separation and hydrocarbon conversion. Although many different crystalline aluminosilicates and silicates have been disclosed, there is a continuing need for new zeolites and silicates with desirable properties for gas separation and drying, hydrocarbon and chemical conversions, and other applications.
Crystalline aluminosilicates are usually prepared from aqueous reaction mixtures containing alkali or alkaline earth metal oxides, silica, and alumina. "Nitrogenous zeolites" have been prepared from reaction mixtures containing an organic templating agent, usually a nitrogen-containing organic cation. By varying the synthesis conditions and the composition of the reaction mixture, different zeolites can be formed using the same templating agent. Use of N,N,N-trimethyl cyclopentylammonium iodide in the preparation of Zeolite SSZ-15 molecular sieve is disclosed in U.S. Pat. No. 4,610,854; use of 1-azoniaspiro[4.4]nonyl bromide and N,N,N-trimethyl neopentylammonium iodide in the preparation of a molecular sieve termed "Losod" is disclosed in Helv. Chim. Acta (1974), Vol. 57, page 1533 (W. Sieber and W. M. Meier); use of quinuclidinium compounds to prepare a zeolite termed "NU-3" is disclosed in European Patent Publication No. 40016; use of 1,4-di(1-azoniabicyclo[2.2.2.]octane) lower alkyl compounds in the preparation of Zeolite SSZ-16 molecular sieve is disclosed in U.S. Pat. No. 4,508,837; use of N,N,N-trialkyl-1-adamantamine in the preparation of zeolite SSZ-13 molecular sieve is disclosed in U.S. Pat. No. 4,544,538.
We have prepared a family of crystalline aluminosilicate molecular sieves with unique properties, referred to herein as "Zeolite SSZ-28", or simply "SSZ-28", and have found a highly effective method for preparing SSZ-28.
SSZ-28 has a mole ratio of an oxide selected from silicon oxide, germanium oxide, and mixtures thereof to an oxide selected from aluminum oxide, gallium oxide, iron oxide, boron oxide and mixtures thereof in the range of 20 to less than 50, and having the X-ray diffraction lines of Table 1 below. Novel zeolite SSZ-28 has essentially the same X-ray diffraction pattern as ZSM-58, described in U.S. Pat. No. 4,665,264. In the present invention the aluminum content is higher than previously described.
As has been shown before, aluminum can be a crystallization inhibitor during the synthesis of pentasil zeolites. Sand and co-workers have shown that crystallization rates for ZSM-5 are lowered by increasing aluminum content (Zeolites 1983, page 155). For some pentasil zeolites sufficient quantities of aluminum prevent crystallization entirely, establishing a lower boundary for SiO2 /Al2 O3 values. In other instances a boundary can be reached because a different zeolite is obtained at a certain SiO2 /Al2 O3 ratio. The zeolite further has a composition, as synthesized and in the anhydrous state, in terms of mole ratios of oxides as follows: (0.1 to 2.0)Q2 O:(0.1 to 2.0)M2 O:W2 O3 :(20 to less than 50)YO2 wherein M is an alkali metal cation, W is selected from aluminum, gallium, iron, boron and mixtures thereof, Y is selected from silicon, germanium and mixtures thereof, and Q is an N,N-dimethyl-tropinium cation or a N,N-dimethyl-3-azonium bicyclo[3.2.2]nonane cation. SSZ-28 zeolites can have a YO2 :W2 O3 mole ratio in the range of 20 to less than 50 (ZSM-58 is made of SiO2 /Al2 O3 >50). As prepared, the silica:alumina mole ratio is typically in the range of 30:1 to about 45:1. Higher mole ratios can be obtained by treating the zeolite with chelating agents or acids to extract aluminum from the zeolite lattice. The silica:alumina mole ratio can also be increased by using silicon and carbon halides and other similar compounds. Preferably, SSZ-28 is an aluminosilicate wherein W is aluminum and Y is silicon.
Our invention also involves a method for preparing SSZ-28 zeolites, comprising preparing an aqueous mixture containing sources of an N,N-dimethyl-tropinium, or N,N-dimethyl-3-azonium bicyclo[3.2.2]nonane cation, an oxide selected from aluminum oxide, preferably the aluminum oxide source provides aluminum oxide which is in a covalently dispersed form on silica, i.e., the aluminum atoms are covalently bonded through oxygen atoms to silicon; gallium oxide; iron oxide; boron oxide and mixtures thereof, and an oxide selected from silicon oxide; germanium oxide and mixtures thereof, and having a composition, in terms of mole ratios of oxides, falling within the following ranges: YO2 /W2 O3, 20:1 to less than 50:1; and Q2 O/YO2 0.05:1 to 0.50:1; wherein Y is selected from silicon, germanium, and mixtures thereof, W is selected from aluminum, gallium, iron, boron and mixtures thereof, and Q is an N,N-dimethyl-tropinium, or N,N-dimethyl-3-azonium bicyclo[3.2.2]nonane cation; maintaining the mixture at a temperature of at least 100� C. until the crystals of said zeolite are formed; and recovering said crystals. The preferred aluminum source seems to slow down the formation of other zeolite-type impurities.
SSZ-28 zeolites, as synthesized, have a crystalline structure whose X-ray powder diffraction pattern shows the following characteristic lines:
TABLE 1______________________________________2θ d/n Int. I/Io______________________________________ 7.72 11.45 1511.42 7.75 1515.02 6.79 3514.40 6.15 915.46 5.73 6517.18 5.16 10018.33 4.84 4418.92 4.69 6219.73 4.50 4426.28 3.39 6826.58 3.35 4426.93 3.31 32______________________________________
Typical SSZ-28 aluminosilicate zeolites have the X-ray diffraction pattern of Tables 2-5.
The X-ray powder diffraction patterns were determined by standard techniques. The radiation was the K-alpha/doublet of copper and a scintillation counter spectrometer with a strip-chart pen recorder was used. The peak heights I and the positions, as a function of 2θ where θ is the Bragg angle, were read from the spectrometer chart. From these measured values, the relative intensities, 100I/Io, where Io is the intensity of the strongest line or peak, and d, the interplanar spacing in Angstroms corresponding to the recorded lines, can be calculated. The X-ray diffraction pattern of Table 1 is characteristic of SSZ-28 zeolites. The zeolite produced by exchanging the metal or other cations present in the zeolite with various other cations yields substantially the same diffraction pattern although there can be minor shifts in interplanar spacing and minor variations in relative intensity. Minor variations in the diffraction pattern can also result from variations in the organic compound used in the preparation and from variations in the silica-to-alumina mole ratio from sample to sample. Calcination can also cause minor shifts in the X-ray diffraction pattern. Notwithstanding these minor perturbations, the basic crystal lattice structure remains unchanged.
After calcination the SSZ-28 zeolites have a crystalline structure whose X-ray powder diffraction pattern shows the following characteristic lines as indicated in Table 2 below:
TABLE 2______________________________________2θ d/n Int. I/Io______________________________________6.56 13.50 71*7.79 11.35 10011.45 7.73 8112.92 6.85 9014.47 6.12 8715.52 5.71 7117.25 5.14 9518.41 4.82 6218.92 4.69 7619.86 4.47 4726.30 3.38 10026.62 3.34 5726.95 3.30 52______________________________________ *Can have greatly varied intensity
SSZ-28 zeolites can be suitably prepared from an aqueous solution containing sources of an alkali metal oxide, N,N-dimethyl-tropinium, or N,N-dimethyl-3-azonium bicyclo[3.2.2]nonane cation, an oxide of aluminum and preferably wherein the aluminum oxide source provides aluminum oxide which is in a covalently dispersed form on silica; gallium; iron; boron and mixtures thereof, and an oxide of silicon or germanium, or mixture of the two. The reaction mixture should have a composition in terms of mole ratios falling within the following ranges:
______________________________________ Broad Preferred______________________________________YO2 /W2 O3 20-less 30-45 than 50OH- /YO2 0.10-0.45 0.20-0.40Q/YO2 0.05-0.50 0.10-0.20M+ /YO2 0.05-0.30 0.15-0.30H2 O/YO2 20-300 25-60Q/Q + M+ 0.25-0.75 0.33-0.67______________________________________
wherein Q is an N,N-dimethyl-tropinium or an N,N-dimethyl-3-aza bicyclo[3.2.2]nonane cation, Y is silicon, germanium or both, and W is aluminum, gallium, iron, boron or mixtures thereof. M is an alkali metal, preferably sodium or potassium. The organic cation compound which acts as a source of the quaternary ammonium ion employed can provide hydroxide ion. Anions which are associated with the organic cation are those which are not detrimental to the formation of the zeolite.
Representative of the anions include halogen, e.g., fluoride, chloride, bromide and iodide, hydroxide, acetate, sulfate, carboxylate, etc. Hydroxide is the most preferred anion.
The reaction mixture is prepared using standard zeolitic preparation techniques.
As typical sources of aluminum oxide for preparing SSZ-28, we have found that providing aluminum oxide to a zeolite synthesis mixture wherein the aluminum oxide is in a covalently dispersed form on silica allows zeolites with increased aluminum content to be crystallized. In one approach zeolites of pentasil structure and lower SiO2 /Al2 O3 values (approximately 10) can be used as aluminum oxide sources or feedstocks for the synthesis. These zeolites are recrystallized to a new structure in the presence of the Cation Component Q defined above. Mordenite and ferrierite zeolites constitute two such useful sources of aluminum oxide or feedstocks. These latter zeolites have also been used in the crystallization of ZSM-5 and ZSM-11 (U.S. Pat. No. 4,503,024). Another approach wherein the aluminum is in a covalently dispersed form on silica is to use an alumina coated silica sol such as that manufactured by Nalco Chem. Co. under the product name 1SJ612 (26% SiO2, 4% Al2 O3).
Typical sources of silicon oxide include silicates, silica hydrogel, silicic acid, colloidal silica, fumed silicas, tetraalkyl orthosilicates, and silica hydroxides. Gallium, iron, boron and germanium can be added in forms corresponding to their aluminum and silicon counterparts. Salts, particularly alkali metal halides such as sodium chloride, can be added to or formed in the reaction mixture. They are disclosed in the literature as aiding the crystallization of zeolites while preventing silica occlusion in the lattice.
The reaction mixture is maintained at an elevated temperature until the crystals of the zeolite are formed. The temperatures during the hydrothermal crystallization step are typically maintained from about 140� C. to about 200� C., preferably from about 160� C. to about 180� C. and most preferably from about 170� C. to about 180� C. The crystallization period is typically greater than 1 day and preferably from about 5 days to about 10 days.
The hydrothermal crystallization is conducted under pressure and usually in an autoclave so that the reaction mixture is subject to autogenous pressure. The reaction mixture can be stirred during crystallization.
Once the zeolite crystals have formed, the solid product is separated from the reaction mixture by standard mechanical separation techniques such as filtration. The crystals are water-washed and then dried, e.g., at 90� C. to 150� C. for from 8 to 24 hours, to obtain the as synthesized, SSZ-28 zeolite crystals. The drying step can be performed at atmospheric or subatmospheric pressures.
During the hydrothermal crystallization step, the SSZ-28 crystals can be allowed to nucleate spontaneously from the reaction mixture. The reaction mixture can also be seeded with SSZ-28 crystals both to direct, and accelerate the crystallization, as well as to minimize the formation of undesired aluminosilicate contaminants. If the reaction mixture is seeded with SSZ-28 crystals, the concentration of the organic compound can be greatly reduced or eliminated, but it is preferred to have some organic compound present, e.g., an alcohol.
The synthetic SSZ-28 zeolites can be used as synthesized or can be thermally treated (calcined). Usually, it is desirable to remove the alkali metal cation by ion exchange and replace it with hydrogen, ammonium, or any desired metal ion. The zeolite can be leached with chelating agents, e.g., EDTA or dilute acid solutions, to increase the silica:alumina mole ratio. The zeolite can also be steamed; steaming helps stabilize the crystalline lattice to attack from acids. The zeolite can be used in intimate combination with hydrogenating components, such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noble metal, such as palladium or platinum, for those applications in which a hydrogenation-dehydrogenation function is desired. Typical replacing cations can include metal cations, e.g., rare earth, Group IIA and Group VIII metals, as well as their mixtures. Of the replacing metallic cations, cations of metals such as rare earth, Mn, Ca, Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, Fe and Co are particularly preferred.
The hydrogen, ammonium, and metal components can be exchanged into the zeolite. The zeolite can also be impregnated with the metals, or, the metals can be physically intimately admixed with the zeolite using standard methods known to the art. And, the metals can be occluded in the crystal lattice by having the desired metals present as ions in the reaction mixture from which the SSZ-28 zeolite is prepared.
Typical ion exchange techniques involve contacting the synthetic zeolite with a solution containing a salt of the desired replacing cation or cations. Although a wide variety of salts can be employed, chlorides and other halides, nitrates, and sulfates are particularly preferred. Representative ion exchange techniques are disclosed in a wide variety of patents including U.S. Pat. Nos. 3,140,249; 3,140,251; and 3,140,253. Ion exchange can take place either before or after the zeolite is calcined.
Following contact with the salt solution of the desired replacing cation, the zeolite is typically washed with water and dried at temperatures ranging from 65� C. to about 315� C. After washing, the zeolite can be calcined in air or inert gas at temperatures ranging from about 200� C. to 820� C. for periods of time ranging from 1 to 48 hours, or more, to produce a catalytically active product especially useful in hydrocarbon conversion processes.
Regardless of the cations present in the synthesized form of the zeolite, the spatial arrangement of the atoms which form the basic crystal lattice of the zeolite remains essentially unchanged. The exchange of cations has little, if any, effect on the zeolite lattice structures.
The SSZ-28 aluminosilicate can be formed into a wide variety of physical shapes. Generally speaking, the zeolite can be in the form of a powder, a granule, or a molded product, such as extrudate having particle size sufficient to pass through a 2-mesh (Tyler) screen and be retained on a 400-mesh (Tyler) screen. In cases where the catalyst is molded, such as by extrusion with an organic binder, the aluminosilicate can be extruded before drying, or, dried or partially dried and then extruded. The zeolite can be composited with other materials resistant to the temperatures and other conditions employed in organic conversion processes. Such matrix materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and metal oxides. The latter may occur naturally or may be in the form of gelatinous precipitates, sols, or gels, including mixtures of silica and metal oxides. Use of an active material in conjunction with the synthetic zeolite, i.e., combined with it, tends to improve the conversion and selectivity of the catalyst in certain organic conversion processes. Inactive materials can suitably serve as diluents to control the amount of conversion in a given process so that products can be obtained economically without using other means for controlling the rate of reaction. Frequently, zeolite materials have been incorporated into naturally occurring clays, e.g., bentonite and kaolin. These materials, i.e., clays, oxides, etc., function, in part, as binders for the catalyst. It is desirable to provide a catalyst having good crush strength, because in petroleum refining the catalyst is often subjected to rough handling. This tends to break the catalyst down into powders which cause problems in processing.
Naturally occurring clays which can be composited with the synthetic zeolites of this invention include the montmorillonite and kaolin families, which families include the sub-bentonites and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite, or anauxite. Fibrous clays such as sepiolite and attapulgite can also be used as supports. Such clays can be used in the raw state as originally mined or can be initially subjected to calcination, acid treatment or chemical modification.
In addition to the foregoing materials, the SSZ-28 zeolites can be composited with porous matrix materials and mixtures of matrix materials such as silica, alumina, titania, magnesia, silica:alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, titania-zirconia as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. The matrix can be in the form of a cogel.
The SSZ-28 zeolites can also be composited with other zeolites such as synthetic and natural faujasites (e.g., X and Y), erionites, and mordenites. They can also be composited with purely synthetic zeolites such as those of the ZSM series. The combination of zeolites can also be composited in a porous inorganic matrix.
SSZ-28 zeolites are useful in hydrocarbon conversion reactions. Hydrocarbon conversion reactions are chemical and catalytic processes in which carbon containing compounds are changed to different carbon containing compounds. Examples of hydrocarbon conversion reactions include catalytic cracking, hydrocracking, and olefin and aromatics formation reactions, including formation from oxygenates. The catalysts are useful in other petroleum refining and hydrocarbon conversion reactions such as isomerizing n-paraffins and naphthenes, polymerizing and oligomerizing olefinic or acetylenic compounds such as isobutylene and butene-1, reforming, alkylating, isomerizing polyalkyl substituted aromatics (e.g., meta xylene), and disproportionating aromatics (e.g., toluene) to provide mixtures of benzene, xylenes and higher methylbenzenes.
SSZ-28 zeolites can be used in processing hydrocarbonaceous feedstocks. Hydrocarbonaceous feedstocks contain carbon compounds and can be from many different sources, such as virgin petroleum fractions, recycle petroleum fractions, shale oil, liquefied coal, tar sand oil, and, in general, can be any carbon containing fluid susceptible to zeolitic catalytic reactions. Depending on the type of processing the hydrocarbonaceous feed is to undergo, the feed can contain metal or be free of metals, it can also have high or low nitrogen or sulfur impurities. It can be appreciated, however, that in general processing will be more efficient (and the catalyst more active) the lower the metal, nitrogen, and sulfur content of the feedstock.
The conversion of hydrocarbonaceous feeds can take place in any convenient mode, for example, in fluidized bed, moving bed, or fixed bed reactors depending on the types of process desired. The formulation of the catalyst particles will vary depending on the conversion process and method of operation.
Other reactions which can be performed using the catalyst of this invention containing a metal, e.g., platinum, include hydrogenation-dehydrogenation reactions, denitrogenation and desulfurization reactions.
SSZ-28 can be used in hydrocarbon conversion reactions with active or inactive supports, with organic or inorganic binders, and with and without added metals. These reactions are well known to the art, as are the reaction conditions.
SSZ-28 can be used to dewax hydrocarbonaceous feeds by selectively removing straight chain paraffins. The catalytic dewaxing conditions are dependent in large measure on the feed used and upon the desired pour point. Generally, the temperature will be between about 200� C. and about 475� C., preferably between about 250� C. and about 450� C. The pressure is typically between about 15 psig and about 3000 psig, preferably between about 200 psig and 3000 psig. The liquid hourly space velocity (LHSV) preferably will be from 0.1 to 20, preferably between about 0.2 and about 10.
Hydrogen is preferably present in the reaction zone during the catalytic dewaxing process. The hydrogen to feed ratio is typically between about 500 and about 30,000 SCF/bbl (standard cubic feet per barrel), preferably about 1000 to about 20,000 SCF/bbl. Generally, hydrogen will be separated from the product and recycled to the reaction zone. Typical feedstocks include light gas oil, heavy gas oils and reduced crudes boiling about 350� F.
The SSZ-28 hydrodewaxing catalyst may optionally contain a hydrogenation component of the type commonly employed in dewaxing catalysts. The hydrogenation component may be selected from the group of hydrogenation catalysts consisting of one or more metals of Group VIB and Group VIII, including the salts, complexes and solutions containing such metals. The preferred hydrogenation catalyst is at least one of the group of metals, salts and complexes selected from the group consisting of at least one of platinum, palladium, rhodium, iridium and mixtures thereof or at least one from the group consisting of nickel, molybdenum, cobalt, tungsten, titanium, chromium and mixtures thereof. Reference to the catalytically active metal or metals is intended to encompass such metal or metals in the elemental state or in some form such as an oxide, sulfide, halide, carboxylate and the like.
The hydrogenation component is present in an effective amount to provide an effective hydrodewaxing catalyst preferably in the range of from about 0.05 to 5% by weight.
SSZ-28 can be used to convert light straight run naphthas and similar mixtures to highly aromatic mixtures. Thus, normal and slightly branched chained hydrocarbons, preferably having a boiling range above about 40� C. and less than about 200� C., can be converted to products having a substantially higher octane aromatics content by contacting the hydrocarbon feed with the zeolite at a temperature in the range of from about 400� C. to 600� C., preferably 480� C.-550� C. at pressures ranging from atmospheric to 10 bar, and liquid hourly space velocities (LHSV) ranging from 0.1 to 15.
The conversion catalyst preferably contains a Group VIII metal compound to have sufficient activity for commercial use. By Group VIII metal compound as used herein is meant the metal itself or a compound thereof. The Group VIII noble metals and their compounds, platinum, palladium, and iridium, or combinations thereof can be used. Rhenium or tin or a mixture thereof may also be used in conjunction with the Group VIII metal compound and preferably a noble metal compound. The most preferred metal is platinum. The amount of Group VIII metal present in the conversion catalyst should be within the normal range of use in reforming catalysts, from about 0.05 to 2.0 weight percent, preferably 0.2 to 0.8 weight percent.
The zeolite/Group VIII metal conversion catalyst can be used without a binder or matrix. The preferred inorganic matrix, where one is used, is a silica-based binder such as Cab-O-Sil or Ludox. Other matrices such as magnesia and titania can be used. The preferred inorganic matrix is nonacidic. Alumina binders can also be used especially when it is desirable to have some acidity in the matrix.
It is critical to the selective production of aromatics in useful quantities that the conversion catalyst be substantially free of acidity, for example by poisoning the zeolite with a basic metal, e.g., alkali metal, compound. The zeolite is usually prepared from mixtures containing alkali metal hydroxides and thus have alkali metal contents of about 1-2 weight percent. These high levels of alkali metal, usually sodium or potassium, are unacceptable for many catalytic applications because they greatly deactivate the catalyst for cracking reactions. Usually, the alkali metal is removed to low levels by ion-exchange with hydrogen or ammonium ions. By alkali metal compound as used herein is meant elemental or ionic alkali metals or their basic compounds. Surprisingly, unless the zeolite itself is substantially free of acidity, the basic compound is required in the present process to direct the synthetic reactions to aromatics production.
The amount of alkali metal necessary to render the zeolite substantially free of acidity can be calculated using standard techniques based on the aluminum content of the zeolite. Under normal circumstances, the zeolite as prepared and without ion-exchange will contain sufficient alkali metal to neutralize the acidity of the catalyst. If a zeolite free of alkali metal is the starting material, alkali metal ions can be ion exchanged into the zeolite to substantially eliminate the acidity of the zeolite. An alkali metal content of about 100%, or greater, of the acid sites calculated on a molar basis is sufficient.
Where the basic metal content is less than 100% of the acid sites on a molar basis, the test described in U.S. Pat. No. 4,347,394 which patent is incorporated totally herein by reference, can be used to determine if the zeolite is substantially free of acidity.
The preferred alkali metals are sodium and potassium. The zeolite itself can be substantially free of acidity only at very high silica:alumina mol ratios; by "zeolite consisting essentially of silica" is meant a zeolite which is substantially free of acidity without base poisoning.
Hydrocarbon cracking stocks can be catalytically cracked in the absence of hydrogen using SSZ-28 at liquid hourly space velocities from 0.5 to 50, temperatures from about 260� F. to 1625� F. and pressures from subatmospheric to several hundred atmospheres, typically from about atmospheric to about 5 atmospheres.
For this purpose, the SSZ-28 catalyst can be composited with mixtures of inorganic oxide supports as well as traditional cracking catalyst.
The catalyst may be employed in conjunction with traditional cracking catalysts, e.g., any aluminosilicate heretofore employed as a component in cracking catalysts. Representative of the zeolitic aluminosilicates disclosed heretofore as employable as component parts of cracking catalysts are Zeolite Y (including steam stabilized chemically modified, e.g., ultra-stable Y), Zeolite X, Zeolite beta (U.S. Pat. No. 3,308,069), Zeolite ZK-20 (U.S. Pat. No. 3,445,727), Zeolite ZSM-3 (U.S. Pat. No. 3,415,736), faujasite, LZ-10 (U.K. Pat. 2,014,970, Jun. 9, 1982), ZSM-5-type zeolites, e.g., ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, crystalline silicates such as silicalite (U.S. Pat. No. 4,061,724), erionite, mordenite, offretite, chabazite, FU-1-type zeolite, NU-type zeolites, LZ-210-type zeolite and mixtures thereof. Traditional cracking catalysts containing amounts of Na2 O less than about one percent by weight are generally preferred. The relative amounts of the SSZ-28 component and traditional cracking component, if any, will depend at least in part, on the selected hydrocarbon feedstock and on the desired product distribution to be obtained therefrom, but in all instances an effective amount of SSZ-28 is employed. When a traditional cracking catalyst (TC) component is employed the relative weight ratio of the TC to the SSZ-28 is generally between about 1:10 and about 500:1, desirably between about 1:10 and about 200:1, preferably between about 1:2 and about 50:1, and most preferably is between about 1:1 and about 20:1.
The cracking catalysts are typically employed with an inorganic oxide matrix component which may be any of the inorganic oxide matrix components which have been employed heretofore in the formulation of FCC catalysts including: amorphous catalytic inorganic oxides, e.g., catalytically active silica-aluminas, clays, silicas, aluminas, silica-aluminas, silica-zirconias, silica-magnesias, alumina-borias, alumina-titanias and the like and mixtures thereof. The traditional cracking component and SSZ-28 may be mixed separately with the matrix component and then mixed or the TC component and SSZ-28 may be mixed and then formed with the matrix component.
The mixture of a traditional cracking catalyst and SSZ-28 may be carried out in any manner which results in the coincident presence of such in contact with the crude oil feedstock under catalytic cracking conditions. For example, a catalyst may be employed containing the traditional cracking catalyst and a SSZ-28 in single catalyst particles or SSZ-28 with or without a matrix component may be added as a discrete component to a traditional cracking catalyst.
SSZ-28 is especially useful as a catalyst in a process for isomerizing one or more xylene isomers in a C8 aromatic feed to obtain ortho-, meta- and para-xylene in a ratio approaching the equilibrium value. In particular, xylene isomerization is used in conjunction with a separation process to manufacture para-xylene. For example, a portion of the para-xylene in a mixed C8 aromatics stream may be recovered by crystallization and centrifugation. The mother liquor from the crystallizer is then reacted under xylene isomerization conditions to restore ortho-, meta-, and para-xylenes to a near equilibrium ratio. At the same time, part of the ethylbenzene in the mother liquor is converted to xylenes or to products which are easily separated by distillation. The isomerate is blended with fresh feed and the combined stream is distilled to removed heavy and light by-products. The resultant C8 aromatics stream is then sent to the crystallizer to repeat the cycle.
Xylene isomerization catalysts are judged on their ability to produce a near equilibrium mixture of xylenes and convert ethylbenzene with very little net loss of xylenes. The SSZ-28 type zeolites are especially effective in this regard. Accordingly, an additional aspect of the present invention is to provide a hydrocarbon conversion process which comprises contacting a C8 aromatic stream containing one or more xylene isomers or ethylbenzene or a mixture thereof, under isomerization conditions with a catalyst comprising SSZ-28.
The SSZ-28 may conveniently be used as an aggregate in the form of pellets or extrudates. An inorganic oxide binder such as gamma alumina or silica may be employed to provide attrition resistance.
In the vapor phase, suitable isomerization conditions include a temperature in the range 500�-1100� F., preferably 600�-1050� F., a pressure in the range 0.5-50 atm abs, preferably 1-5 atm abs, and a weight hourly space velocity (WHSV) of 0.1 to 100, preferably 0.5 to 50. Optionally, isomerization in the vapor phase is conducted in the presence of 3.0 to 30.0 moles of hydrogen per mole of alkylbenzene. If hydrogen is used the catalyst should comprise 0.1 to 2.0 wt % of a hydrogenation/dehydrogenation component selected from Group VIII of the Periodic Table, especially platinum, palladium, or nickel. By Group VIII metal component is meant the metals and their compounds such as oxides and sulfides.
In the liquid phase, suitable isomerization conditions include a temperature in the range 100�-700� F., a pressure in the range 1-200 atm abs, and a WHSV in the range 0.5-50. Optionally, the isomerization feed may contain 10 to 90 wt % of a diluent such as toluene, trimethylbenzenes, naphthenes or paraffins.
SSZ-28 can also be used to oligomerize straight and branched chain olefins having from about 2 to 21 and preferably 2-5 carbon atoms. The oligomers which are the products of the process are medium to heavy olefins which are useful for both fuels, i.e., gasoline or a gasoline blending stock and chemicals.
The oligomerization process comprises contacting the olefin feedstock in the gaseous state phase with SSZ-28 at a temperature of from about 450� F. to about 1200� F., a WHSV of from about 0.2 to about 50 and a hydrocarbon partial pressure of from about 0.1 to about 50 atmospheres.
Also, temperatures below about 450� F. may be used to oligomerize the feedstock, when the feedstock is in the liquid phase when contacting the zeolite catalyst. Thus, when the olefin feedstock contacts the zeolite catalyst in the liquid phase, temperatures of from about 50� F. to about 450� F., and preferably from 80� to 400� F. may be used and a WHSV of from about 0.05 to 20 and preferably 0.1 to 10. It will be appreciated that the pressures employed must be sufficient to maintain the system in the liquid phase. As is known in the art, the pressure will be a function of the number of carbon atoms of the feed olefin and the temperature. Suitable pressures include from about 0 psig to about 3000 psig.
The zeolite can have the original cations associated therewith replaced by a wide variety of other cations according to techniques well known in the art. Typical cations would include hydrogen, ammonium and metal cations including mixtures of the same. Of the replacing metallic cations, particular preference is given to cations of metals such as rare earth metals, manganese, calcium, as well as metals of Group II of the Periodic Table, e.g., zinc, and Group VIII of the Periodic Table, e.g., nickel. One of the prime requisites is that the zeolite have a fairly low aromatization activity, i.e., in which the amount of aromatics produced is not more than about 20% by weight. This is accomplished by using a zeolite with controlled acid activity [alpha value] of from about 0.1 to about 120, preferably from about 0.1 to about 100, as measured by its ability to crack n-hexane.
Alpha value are defined by a standard test known in the art, e.g., as shown in U.S. Pat. No. 3,960,978 which is incorporated totally herein by reference. If required, such zeolites may be obtained by steaming, by use in a conversion process or by any other method which may occur to one skilled in this art.
SSZ-28 can be used to convert light gas C2 -C6 paraffins and/or olefins to higher molecular weight hydrocarbons including aromatic compounds. Operating temperatures of 100� C.-700� C., operating pressures of 0 to 1000 psig and space velocities of 0.5-40 hr-1 WHSV (weight hourly space velocity) can be used to convert the C2 -C6 paraffin and/or olefins to aromatic compounds. Preferably, the zeolite will contain a catalyst metal or metal oxide wherein said metal is selected from the group consisting of Group IB, IIB, VIII and IIIA of the Periodic Table, and most preferably gallium or zinc and in the range of from about 0.05 to 5% by weight.
SSZ-28 can be used to condense lower aliphatic alcohols having 1 to 8 carbon atoms to a gasoline boiling point hydrocarbon product comprising mixed aliphatic and aromatic hydrocarbon. The condensation reaction proceeds at a temperature of about 500� F. to 1000� F., a pressure of about 0.5 to 1000 psig and a space velocity of about 0.5 to 50 WHSV. The process disclosed in U.S. Pat. No. 3,984,107 more specifically describes the process conditions used in this process, which patent is incorporated totally herein by reference.
The catalyst may be in the hydrogen form or may be base exchanged or impregnated to contain ammonium or a metal cation complement, preferably in the range of from about 0.05 to 5% by weight. The metal cations that may be present include any of the metals of the Groups I through VIII of the Periodic Table. However, in the case of Group IA metals the cation content should in no case be so large as to effectively inactivate the catalyst.
The conversion of methanol to low molecular weight olefins (C2 -C5) is a desirable process. SSZ-28 can be used to convert methanol to olefins. A methanol feedstock comprises any liquid or gaseous feedstock containing methanol.
The process of methanol conversion conditions comprise a temperature in the range of from about 550� F. to about 850� F., preferably from about 650� F. to about 700� F., at a space velocity of grams of methanol per gram of SSZ-28 per hour of from about 0.1 g/g/hr to about 10 g/g/hr, preferably from about 0.5 g/g/hr to about 2 g/g/hr, and at a pressure of about 1 atmosphere or higher.
SSZ-28 can also be used as an adsorbent, as a filler in paper, paint, and toothpastes, and as a water-softening agent in detergents.
The following Examples illustrate the preparation of SSZ-28.
The N-methyl-tropine quaternary ammonium cation template is conveniently prepared by dissolving tropine (Aldrich Chem. Co.) in a chilled ethyl acetate solution and adding methyl iodide in a dropwise manner. The product falls out of solution and in high yield in a matter of a few hours. It can be recrystallized before use in the next step. The vacuum-dried iodide salt was then ion-exchanged with ion-exchange resin AG 1�8 (in molar excess) to the hydroxide form. The exchange was performed over a column or more preferably by overnight stirring of the resin beads and the iodide salt in an aqueous solution designed to give about a 0.5 molar solution of the organic hydroxide, i.e., N,N-dimethyl-tropinium hydroxide. (Template 1)
5 grams (40 mM) of 3-azabicyclo[3.2.2]nonane were dissolved in 100 ml of methanol. 8 grams of potassium bicarbonate were added and the solution was stirred at room temperature. 15 grams of methyl iodide were added dropwise and the reaction was stirred overnight. The reaction is concentrated to dryness and the remaining solids are treated with chloroform and then filtered. The filtrate is concentrated by removal of chloroform and the solid residue is triturated with tetrahydrofuran, filtered and washed with diethyl ether. This product is the N,N,-dimethyl-3-azonium bicyclo[3.2.2]nonane iodide salt. This product is then ion-exchanged by the method in Example 1 to give the hydroxide compound (Template 2).
4.5 Grams of a 0.67M solution of Template 1 in its hydroxide form were mixed with 6 ml H2 O and 0.103 gms of KOH (solid). After dissolution 2.36 gms of Ludox AS-30 colloidal silica (30% SiO2) were added with stirring using a magnetic stir bar. Finally 0.78 gms of Nalco 1SJ612 alumina on silica (30% solids, 4% Al2 O3 overall) was added. The reactants were loaded into a Parr 4745 reactor, sealed and loaded onto a rotating spit in a Blue M oven. The reactor was rotated at 30 RPM while being heated at 175� C. for 6 days. The product after filtration, washing with distilled water, drying in air and then at 100� C. was the crystalline material designated SSZ-28. The X-ray diffraction pattern of the as-made material is tabulated in Table 3 below.
TABLE 3______________________________________ 100 �2θ d/n I/Io______________________________________7.77 11.38 328.65 10.22 511.46 7.72 1612.88 6.87 18 Sh13.08 6.77 4214.44 6.13 1115.52 5.71 10017.24 5.14 9718.41 4.819 4718.97 4.678 6619.62 4.525 18 Sh19.81 4.482 4721.57 4.120 2622.37 3.974 1323.06 3.857 1323.30 3.818 2923.50 3.786 16 Sh24.95 3.569 825.88 3.443 1826.27 3.392 6626.35 3.382 63 Sh26.66 3.344 3926.98 3.305 37______________________________________ Sh = shoulder
4.35 Grams of a 0.69M solution of Template 1 were mixed with 0.60 gms 50% RbOH and 0.78 gms; Nalco 1SJ612 alumina on silica (30% solids, 4% Al2 O3 overall), and 5 ml H2 O. After thorough mixing 2.36 gms of Ludox AS-30 was blended in as silica source. The reaction mixture was heated in the teflon cup of a Parr 4745 reactor at 160� C. at 30 RPM for 6 days. Workup as in Example 2 produced crystalline SSZ-28.
4.75 Grams of a 0.69M solution of Template 1 was mixed with 2.6 ml of H2 O, 0.06 gms of NaOH(s), 0.21 gms of NaY zeolite (SK-40), and finally 0.76 gms of Cabosil M5. The mixture was heated at 160� C. for 6 days with agitation. The crystalline product was SSZ-28 and has a SiO2 /Al2 O3 ratio of 37. XRD is shown in Table 4.
TABLE 4______________________________________ 100 �2θ d/n I/Io______________________________________6.56 13.47 267.74 11.42 228.63 10.25 511.43 7.74 1312.85 6.89 14 Sh13.05 6.78 10014.42 6.14 815.47 5.73 8617.18 5.16 8718.33 4.830 3918.89 4.698 5419.63 4.522 3819.77 4.491 4521.50 4.133 2322.32 3.983 1523.03 3.862 1223.28 3.821 2523.46 3.792 16 Sh24.92 3.573 825.87 3.444 1926.23 3.397 8726.62 3.349 3226.96 3.307 2928.29 3.155 1729.25 3.053 1629.43 3.035 11 Sh29.84 2.994 15______________________________________ Sh = shoulder
A zeolite reaction solution was made up from mixing, in sequence, 4.4 gms of Template 1 solution (0.57M) to 8 ml H2 O with 0.19 gms of NaOH. 4.42 gms of Ludox AS-30 was stirred in. Lastly, 2.19 gms of Nalco 1SJ612 colloidal silica-alumina was mixed into the solution. The reaction was run as zeolite reactions in previous examples with a tumbling rate of 30 RPM, and 8 days of heating at 170� C. The product, after the usual work-up, was zeolite SSZ-28. Analysis showed the SiO2 /Al2 O3 ratio to be 42.
A zeolite reaction solution was made up as in Example 6 and in the same order to mixing. In this example, H2 O was reduced to 7 ml, NaOH was increased to 0.24 gm., 4.00 gms of Ludox AS-30 and 2.55 gms of Nalco 1SJ612 colloidal silica-alumina were used. In addition, 50 mg of product from Example 6 were added as seed crystals. The crystallization was run as in Example 6 but for only 6 days. The product was once again SSZ-28 and the ratio of SiO2 /Al2 O3 was 36.
The same reaction was prepared as in Example 7 except Template 2 was then used instead of Template 1. The same molar quantity was employed. The zeolite synthesis was carried out as in Example 7 but at 175� C. The product is also SSZ-28.
The crystalline products of Examples 3-8 were subjected to calcination as follows. The samples were heated in a muffle furnace from room temperature up to 540� C. at a steadily increasing rate over a 7-hour period. The samples were maintained at 540� C. for four more hours and then taken up to 600� C. for an additional four hours. A 50/50 mixture of air and nitrogen was passed over the zeolites at a rate of 20 standard cubic feet per minute during heating. Representative X-ray diffraction data for the calcined product of Example 5 appears in Table 5.
TABLE 5______________________________________ 100 �2θ d/n I/Io______________________________________6.69 13.21 1007.93 11.15 718.77 10.08 411.59 7.63 3513.00 6.81 30 Sh13.19 6.71 6014.58 6.08 2215.20 5.83 815.66 5.66 6117.38 5.10 4518.50 4.796 2119.07 4.654 2919.75 4.495 2019.92 4.457 1721.68 4.099 1122.59 3.936 523.15 3.842 923.50 3.786 1323.62 3.767 10 Sh25.10 3.548 526.04 3.422 11 Sh26.35 3.382 4726.50 3.363 27 Sh26.84 3.322 2427.17 3.282 1928.45 3.137 929.38 3.040 1329.63 3.015 7 Sh30.02 2.977 9______________________________________ Sh = shoulder
It can be seen in Table 5 that the line at 2θ=6.69 is now the strongest line in the pattern. Not all calcined samples of SSZ-28 show this.
Ion-exchange of the calcined SSZ-28 materials from Example 9 was carried out using NH4 NO3 to convert the zeolites from their M+ form to NH4 + and then eventually H+ form. Typically the same mass of NH4 NO3 as zeolite was slurried into H2 O at a ratio of 50/1 H2 O to zeolite. The exchange solution was heated at 100� C. for two hours and then filtered. This process was repeated four times. Finally, after the last exchange the zeolite was washed several times with H2 O and dried. A repeat calcination as in Example 9 was carried out but without the final treatment at 600� C. This produces the H+ form of SSZ-28 zeolite.
The product of Example 5, after sequential treatment as in Examples 9 and then 10, was subjected to a surface area and pore size distribution analysis using N2 as adsorbate and via the BET method. The surface area of the zeolitic material was 450 m2 /gm and the micropore volume was 0.15 cc/gm.
A catalytic sample of HSSZ-28 was prepared by using the product of Example 7 and subjecting it to the treatments described in Examples 9 and 10. This material was then used for the conversion of methanol to hydrocarbon products. 0.5 gms of HSSZ-28 was loaded as a powder into a 1/4 in. reactor with a bed of alundum on either side. The catalyst was heated to 800� F. in helium and then the temperature was reduced to 650� F. Methanol was introduced at a rate of 1.3 cc/hr. through the catalyst bed. Methanol was entirely converted at short reaction times but appeared in the product as the catalyst fouled. The products formed from methanol are given in Table 6 as determined by Gas Chromatograph after 10 minutes on stream.
TABLE 6______________________________________Hydrocarbon Product Area %______________________________________METHANE 5.4ETHYLENE 8.7ETHANE 1.6PROPYLENE 29.5PROPANE 19.1METHANOL 0.0DIMETHYL ETHER 0.0BUTENES 7.3BUTANES 14.1PENTENES 2.4PENTANES 7.4HEXENES <0.5HEXANES <0.5BENZENE <0.1TOLUENE 4.6______________________________________
Using the product of Example 7 and converting it to the catalytic form as in Examples 9 and 10, HSSZ-28 was produced with SiO2 /Al2 O3 =35. The powder was pelletized at approximately 12,000 lbs on a Carver press and then broken up to 25-45 mesh. The catalyst chips (0.50 gms) were loaded into a 1/4 in. reactor as described in Example 12 and a 50/50 feed of hexane and 3 methyl pentane was run to determine a constraint index at 800� F. At 10 minutes on stream the conversion was 12% and the constraint index was calculated to be 4.
SSZ-28 was prepared as in Example 7 and treated as in Examples 9, and 10. The acid form of the zeolite was then neutralized by refluxing overnight with dilute KOH. After washing and drying the zeolite, it was calcined following the procedure of Example 9, excluding the 600� C. heating step. The KOH treatment is repeated a second time with subsequent washing, drying and calcination. The K-exchanged zeolite is impregnated via the incipient wetness technique with 0.8 wt % Pt and calcined in the usual manner for reforming catalysts. The catalyst is then evaluated using a light straight run feed. Reactor conditions are given in Table 7 below:
TABLE 7______________________________________100 PSIG2 LHSV3 H2 /HC890� F.COMPOSITION, WT % FEED PRODUCT______________________________________C4 - 0.0 13.5Total C5 5.4 7.4iC6 12.0 14.0nC6 17.4 12.7Benzene 0.7 4.5iC7 15.4 13.8nC7 15.4 7.2Toluene 2.2 10.6iC8 + 11.5 4.3nC8 + 4.5 1.3C8 + Aromatics 1.3 6.9LV % 100 83.9RON 60.8 72.5______________________________________
A sample of zeolite H+ SSZ-28 prepared according to Examples 6, 9 and 10 was tested for xylene isomerization activity as follows. The pure zeolite powder was formed into pellets using a hydraulic press. The pellets were crushed and sieved to obtain 20-40 mesh granules which were then calcined for four hours at 1000� F. One gram of the calcined material was then charged to a 3/16-inch I.D. tubular microreactor heated by an electric furnance. The catalyst bed was heated to 800� F. in flowing helium. The helium was then replaced with a mixed xylene feed. The feed composition and reactor effluent were analyzed by gas chromatography. Table 8 below shows that the zeolite H+ SSZ-28 produced a near equilibrium mixture of xylenes. Better than 30% ethylbenzene conversion was obtained with less than six percent loss of xylenes.
TABLE 8______________________________________XYLENE ISOMERIZATION OVER ZEOLITE H+ SSZ-28______________________________________Temperature, �F. 800WHSV 5.6Pressure, psig 25Composition, Wt % Feed ProductsNon-aromatics 1.4 2.1Benzene 0.0 3.2Toluene 1.3 4.5Ethylbenzene 9.7 6.3P-xylene 9.5 19.1M-xylene 53.1 42.8O-xylene 22.9 18.7Heavy aromatics 2.1 3.2Percent EB Conversion 35Percent Xylene Loss 5.6P-xylene % approach 102to equilibrium______________________________________
SSZ-28 powder from Example 7 and treated according to Examples 9 and 10, was impregnated with palladium as follows.
Three grams of the product of Examples 7, 9 and 10 was vacuum-dried at 600� F. Sufficient Pd(NH3)4 (NO3)2 dissolved in 3 ml H2 O was impregnated into the H+ SSZ-28 to give 0.5 wt % loading of Pd. The catalyst was heated at 100� C. in a closed system overnight. The solids are then heated slowly up to 900� F. over several hours and held there for 3 hours.
The palladium-impregnated powder was formed into tablets which were crushed and sieved to obtain 20-40 mesh granules for testing in a microreactor. The granular catalyst was activated by calcination in air at 250� F. to 900� F. over a period of eight hours followed by reduction of the palladium in flowing hydrogen at 900� F. The catalyst was tested as described in the previous example except that the xylene isomerization process was carried out at 150 psig in the presence of hydrogen.
The reaction conditions and results are shown in Table 9. As in the previous example, SSZ-28 was shown to produce a near equilibrium mixture of xylenes with only a small net xylene loss at better than 30% ethylbenzene conversion. The presence of hydrogen and a hydrogenation catalyst (i.e., Pd) was found to inhibit catalyst fouling and greatly increase run length compared to the previous example. Also, the start of run temperature was reduced by 150� F.
TABLE 9______________________________________Xylene isomerization over Palladium-Impregnated SSZ-28______________________________________Temperature, �F. 650WHSV of xylene feed 5Pressure, psig 150H2 /xylene molar ratio 10Composition, Wt. % Feed ProductsNon-aromatics 1.4 3.3Benzene 0.0 1.7Toluene 1.3 3.9Ethylbenzene 9.7 6.5P-xylene 9.5 18.4M-xylene 53.1 42.8O-xylene 22.9 18.0Heavy aromatics 2.1 5.3Percent EB Conversion 33Percent Xylene Loss 7.3P-xylene % approach to 97equilibrium______________________________________
|Cited Patent
|Filing date
|Publication date
|Nov 16, 1977
|Sep 26, 1978
|Mobil Oil Corporation
|Hydrocarbon conversion with crystalline zeolite ZSM-34
|Mar 8, 1982
|Jan 24, 1984
|Mobil Oil Corporation
|Activation of zeolites
|May 5, 1983
|Jun 11, 1985
|Hoechst Aktiengesellschaft
|Process for the production of a crystalline aluminosilicate zeolite
|Feb 26, 1985
|Jun 3, 1986
|Mobil Oil Corporation
|Synthesis of crystalline silicate ZSM-5 with an alkyltropinium compound promoter
|Oct 29, 1982
|Sep 9, 1986
|Chevron Research Company
|Zeolite SSZ-15 and process for preparing the same
|May 9, 1986
|May 12, 1987
|Mobil Oil Corporation
|Catalytic conversion
|May 9, 1986
|Oct 6, 1987
|Mobil Oil Corporation
|Crystalline silicate ZSM-58 and process for its preparation using a methyltropinium cation
|Citing Patent
|Filing date
|Publication date
|Dec 10, 1992
|Feb 8, 1994
|Mobil Oil Corp.
|Gallium-containing zeolite MCM-22
|Sep 16, 1993
|Jan 17, 1995
|Mobil Oil Corp.
|Gallium-containing zeolite MCM-22
|Dec 1, 1994
|Aug 15, 1995
|Mobil Oil Corp.
|Synthesis of porous crystalline MCM-58
|Feb 24, 1994
|Nov 7, 1995
|Jia; Meng-Dong
|Ceramic-zeolite composite membranes and use for separation of vapor/gas mixtures
|Sep 14, 1994
|Apr 30, 1996
|California Institute Of Technology
|Zeolite CIT-1
|Sep 11, 1996
|Jul 28, 1998
|Chevron U.S.A. Inc.
|Preparation of zeolites using organic template and amine
|Mar 9, 1998
|Feb 29, 2000
|Indian Petrochemicals Corp. Ltd.
|Process for the preparation of a molecular sieve adsorbent for selectively adsorbing nitrogen from a gaseous mixture
|Mar 9, 1998
|Jul 11, 2000
|Indian Petrochemical Corporation Limited
|Process for the preparation of a molecular sieve adsorbent for selectively adsorbing oxygen from a gaseous mixture
|Mar 9, 1998
|Jul 18, 2000
|Indian Petrochemical Corp. Ltd.
|Process for the preparation of a molecular sieve adsorbent for selectively adsorbing methane from a gaseous mixture
|Dec 17, 1997
|Dec 5, 2000
|Chevron U.S.A. Inc.
|Zeolite SSZ-47
|Jul 28, 1999
|Jul 3, 2001
|Chevron U.S.A. Inc.
|Zeolite SSZ-52
|Nov 30, 2000
|Feb 19, 2002
|Chevron U.S.A., Inc.
|Zeolite SSZ-47
|Feb 21, 2001
|Apr 30, 2002
|Chevron U.S.A. Inc.
|Zeolite SSZ-52
|Feb 29, 2000
|May 21, 2002
|Chevron U.S.A. Inc.
|Synthesis of alkybenzenes and synlubes from Fischer-Tropsch products
|Jul 7, 2000
|Aug 27, 2002
|Chevrontexaco Corporation
|Ethylene manufacture by use of molecular redistribution on feedstock C3-5 components
|Jul 24, 2000
|Sep 24, 2002
|Chevron U.S.A. Inc.
|Methods for optimizing fischer-tropsch synthesis
|Jul 24, 2000
|Oct 29, 2002
|Chevron U.S.A. Inc.
|Methods for optimizing Fischer-Tropsch synthesis of hydrocarbons in the distillate fuel and/or lube base oil ranges
|Oct 26, 2000
|Dec 31, 2002
|Chevron U.S.A. Inc.
|Purification of p-xylene using composite mixed matrix membranes
|Nov 30, 2000
|Apr 1, 2003
|Chevron U.S.A. Inc.
|Hydrocarbon conversion with zeolite SSZ-47
|Jun 23, 2000
|May 20, 2003
|Chevron U.S.A. Inc.
|Conversion of refinery C5 paraffins into C4 and C6 paraffins
|Jun 20, 2002
|Nov 18, 2003
|Chevron U.S.A. Inc.
|Methods for optimizing fischer-tropsch synthesis of hydrocarbons in the distillate fuel and/or lube base oil ranges
|Dec 18, 2002
|Jun 29, 2004
|Chevron U.S.A. Inc.
|Crosslinked and crosslinkable hollow fiber mixed matrix membrane and method of making same
|May 28, 2002
|Oct 19, 2004
|Chevron U.S.A. Inc.
|Use of microchannel reactors in combinatorial chemistry
|May 14, 2013
|Chevron U.S.A. Inc.
|Reduction of oxides of nitrogen in a gas stream using molecular sieve SSZ-28
|Nov 8, 2013
|Aug 4, 2015
|Exxonmobil Research And Engineering Company
|Selectivation of adsorbents for gas separation
|Nov 8, 2013
|Oct 27, 2015
|Exxonmobil Research And Engineering Company
|DDR type zeolites with stabilized adsorption
|Nov 8, 2013
|Jun 14, 2016
|Exxonmobil Research And Engineering Company
|Synthesis of ZSM-58 crystals with improved morphology
|Nov 8, 2013
|Jun 12, 2014
|Exxonmobil Research And Engineering Company
|Ddr type zeolites with stabilized adsorption
|Mar 30, 2012
|Mar 19, 2014
|Reduction of oxides of nitrogen in a gas stream using molecular sieve SSZ-28
|Mar 30, 2012
|Jun 8, 2016
|Dec 17, 1997
|Jul 9, 1998
|Chevron U.S.A. Inc.
|Zeolite ssz-47
|Dec 22, 1999
|Jun 29, 2000
|Consejo Superior De Investigaciones Cientificas
|Itq-7 zeolite
|Jun 20, 2000
|Feb 8, 2001
|Chevron U.S.A. Inc.
|Zeolite ssz-52
|Mar 30, 2012
|Feb 14, 2013
|Chevron U.S.A. Inc.
|Reduction of oxides of nitrogen in a gas stream using molecular sieve ssz-28
|U.S. Classification
|502/62, 423/718, 423/326, 423/710, 423/704, 502/60, 423/706, 502/61
|International Classification
|Cooperative Classification
|European Classification
|Sep 27, 1996
|Fee payment
Year of fee payment: 4
|Sep 28, 2000
|Fee payment
Year of fee payment: 8
|Sep 29, 2004
|Fee payment
Year of fee payment: 12


text:
I want to know the disadvantages of
In many sites, I have read that using
scanf might cause buffer overflows. What is the reason for this? Are there any other drawbacks with
We started with Q&A. Technical documentation is next, and we need your help.
Whether you're a beginner or an experienced developer, you can contribute.
I want to know the disadvantages of
In many sites, I have read that using
The problems with scanf are (at a minimum):
I very much prefer using
Then you can complain to the user, or allocate more space for the rest of the line (continuously if necessary until you have enough space). In either case, there's no risk of buffer overflow.
Once you've read the line in, you know that you're positioned at the next line so there's no problem there. You can then
Here's a snippet of code which I frequently use to ensure no buffer overflow when asking the user for information.
It could be easily adjusted to use a file other than standard input if necessary and you could also have it allocate its own buffer (and keep increasing it until it's big enough) before giving that back to the caller (although the caller would then be responsible for freeing it, of course).
A test run:
Most of the answers so far seem to focus on the string buffer overflow issue. In reality, the format specifiers that can be used with
One can argue that these
The real problem with
So, to summarize the above, the problem with
P.S. The above in intended to be about the entire family of
From the comp.lang.c FAQ: Why does everyone say not to use scanf? What should I use instead?
Yes, you are right. There is a major security flaw in
clearly the the buffer
It is very hard to get
As an example, what paxdiablo is doing in his function to read can be done with something like:
The above will read a line, store the first 10 non-newline characters in
One of the other problems with
the above cannot be used safely in case of an overflow. Even for the first case, reading a string is much more simpler to do with
Problems I have with the
If you know your input is always going to be well-formed with fixed-length strings and numerical values that don't flirt with overflow, then
Many answers here discuss the potential overflow issues of using
An example of its use:
See here. Disadvantages to this approach is that it is a relatively recent addition to the POSIX specification and it is not specified in the C specification at all, so it remains rather unportable for now.
There is one big problem with
Hell, even this is "fine":
It's worse than
Sure, there are some format-specifier checkers out there, but, those are not perfect and well, they are not part of the language or the standard library.
The advantage of
One of the biggest disadvantages seems to be purely the reputation it's earned amongst the uninitiated; as with many useful features of C we should be well informed before we use it. The key is to realise that as with the rest of C, it seems succinct and idiomatic, but that can be subtly misleading. This is pervasive in C; it's easy for beginners to write code that they think makes sense and might even work for them initially, but doesn't make sense and can fail catastrophically.
For example, the uninitiated commonly expect that the
What would any response to this question be without mentioning it's lack of safety and risk of buffer overflows? As we've already covered, C isn't a safe language, and will allow us to cut corners, possibly to apply an optimisation at the expense of correctness or more likely because we're lazy programmers. Thus, when we know the system will never receive a string larger than a fixed number of bytes, we're given the ability to declare an array that size and forego bounds checking. I don't really see this as a down-fall; it's an option. Again, reading the manual is strongly advised and would reveal this option to us.
Lazy programmers aren't the only ones stung by
Inexperienced programmers aren't forced to consider the success of the operation. Suppose the user enters something entirely non-numeric when we've told
Much like
It's no easier to use
A slight adaptation, by separating the two format delegates and we see some success here:

subset: commoncrawl


text:
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You are a fan of post tech p9 ? Come to discover the best forums post tech p9 on the internet and share your experience with a community fan of post tech p9 . You can also build a forum post tech p9 and create your online discussion.
This is a forum for the Honda Silver Wing. Please feel free and join and post messages and pictures for your Silver Wing Touring Scooter.
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A Harry Potter RPG, set in 2028. Harry Potter is dead. So is Lord Voldemort. Fate now lies in your hands.
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Biker-Haven is a refuge for a true brotherhood of bikers that ride all brands of motorcycles, to come and exchange ideas, talk tech, visit with old friends, make new friends, share experi
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Polarize Play-By-Post is a forum in which members can participate in forum-based games. Anyone is welcome!
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Ace Combat: Legends is dedicated to all things Ace Combat, with an emphasis on Play-by-Post RPGs centered on the arcade flight combat video game series.
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Has your Spartan got a story? Your Elite got a history? Share it here in our Halo database! Here you can post stories and create tales and vent your creativity of the Halo Universe!
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The government often earns a failing grade for small-business contracting
When it comes to awarding contracts to small businesses, the government struggles to reach any of the annual goals it strives for. The Small Business Administration's most recent small-business procurement score card for fiscal 2008 shows that the government achieved only one of its contracting goals last year: It spent 6.76 percent of its prime-contract dollars with small, disadvantaged businesses, topping the goal of 5 percent.
However, the government fell short of its goals in the other categories and the overall goal of 23 percent of total contract spending. Even though agencies spent $93.3 billion with small companies — an increase of nearly $10 billion since 2007 — that dollar amount represented only 21.5 percent of total contract spending. And that overall percentage was down by nearly a percentage point from the previous year.
Seven of the 24 agencies that SBA tracks failed to reach more than one goal, while two of them — the Office of Personnel Management and the U.S. Agency for International Development — missed all of the goals. The General Services Administration was the only agency to achieve all the goals.
SBA rates the agencies with a green, yellow or red score based on the contracts they awarded to small businesses overall and specifically to small, disadvantaged businesses; small businesses in Historically Underutilized Business Zones; woman-owned small businesses; and businesses owned by service-disabled veterans.
About the Author
Matthew Weigelt is a freelance journalist who writes about acquisition and procurement.
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The latest version of the Defense Department-wide Enterprise Service Management Framework places more emphasis on managing IT risk.
Despite GSA's efforts to accelerate the FedRAMP approval process, the lack of agency reciprocity puts the program's central goals at risk.
Got some early-career colleagues who are doing great things in federal IT? Nominate them for FCW's 2016 Rising Star awards.
The agency software inventories required under the draft category management policy will be treasure maps that lead to efficient, effective, streamlined buying and unprecedented savings.
As experts warned of the "dire" threats posed by outdated federal technology, lawmakers grilled top feds, debated workforce issues and inched closer to backing a $3.1 billion fix-it fund.
The agency is making strides in developing and deploying border technologies but still has some weaknesses.
Agencies have spent almost $23 billion on legacy IT over the past three years, according to reports to Congress. Is a revolving fund the answer?
The United Kingdom will go live with its governmentwide digital identity platform, GOV.UK Verify, in the coming days. The U.S. government will need a little more time.
What contracting officer representatives really think is needed to fix contract management.
We are a samll minority business trying to survive in this ecomomy. How would we go about getting ivolved with SBA?Randy Drake DRAKE COMM PRODUCTS 33 Comac Loop Ronkonkoma, NY. 11779 Certified WBE
These "goals" are one of the main reasons the Government is so inefficient. As an engineer trying to get facilities built or repaired, when these goals are imposed on our Contracting group, we end up spending a lot more time and money to meet some goal with the end result often being an inferior product as well. Add to that all these other bureaucrats time (and money) spent on counting well the goals were met.
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Item girl Rakhi Sawant's shocking reaction on the controversial show, ÁIB Knockout has left everyone stunned. Her reply about the show is something very bizarre and out of the world. When Rakhi was asked to comment about AIB Roast, she said that Karan Johar, Ranveer Singh who is participating on ...read more
Rakhi Sawant News
Numerous B-town celebrities expressed their views on the most recent hot topic, the 'AIB' roast: 1.Rakhi Sawant: Rakhi Sawant's mouth is something that is difficult to keep shut. How could the drama queen remain silent when there is so much controver...read more
Rakhi Sawant has always been in controversy for one or the other reason. She once stirred up news, when she fought for the rights of the fellow residents of her residential society. But this time she is on cloud number 9 as she has been appointed as the chairperson of Disputes Settlement Committe...read more
The singer Mika Singh was returning from Bangkok by a private airline. He landed at the Mumbai International airport on Wednesday. The customs department detained him as they found he was carrying more currency on him than that is permissible according to the FEMA (Foreign Exchange Manageme...read more
The sixth season of "Bigg Boss" is being telecasted on television and this reality show which follows the footsteps of "Big Brother" has completed 1½ months of its run on television, for this season. The 6th season comes with the tagline "alag che". This season is also hosted by...read more
Rakhi Sawant made her mark in the music album called "Pardesiya" and since then she tried every gimmick to stay put in the industry. She has pulled down every actor and actress of the film industry to grab some attention for her indelicate comments from the media. She has also got herself to do a...read more
The big-mouthed Rakhi Sawant is well known not only by the regular people but by the top shot celebrities of Bollywood as well. She has also appeared on the couch for an interview with Karan Johar in one of his episodes of Koffee with Karan. Rakhi is famous for her antics and is known as a...read more
Yash Chopra was a legend. His contribution to the Hindi film industry cannot be described in words. His movies speak billion words about his splendid and extravaganza work. Bollywood is a big term and without Yash Chopra's contribution, Hindi film industry won't have reached the level that it is ...read more
It may sound as a big joke but it is true that item girl Rakhi Sawant accused Aamir Khan of stealing the concept of 'Satyamev Jayate', which according was her concept. Rakhi is of the opinion that her talk show titled 'Rakhi Ka Insaaf' is the original concept and &...read more
For keeping yourself hot and boiling, nothing is more appropriate than making headlines. There are some Bollywood personas ever so keen to hove the focus of limelight under theirs gripping belt. With the failure of other options to fame and glory, they don't mind resorting to the most awfu...read more


text: Here's Halo's newest character. Evan Narcisse7/22/14 10:38amFiled to: halohalo nightfallhalo 5halo 5 guardianskotakucorexboxxbox one322EditInvite manuallyPromoteDismissUndismissHideShare to KinjaToggle Conversation toolsGo to permalink Here's Halo's newest character. Played by actor Mike Colter, Agent Locke will be showing up in the live-action Halo: Nightfall series being produced by Ridley Scott. The character will then appear in next year's Halo 5: Guardians. Variety has more details. Reply32 repliesLeave a reply


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Operations Coordinator, Communications Department
Carnegie Corporation of New York seeks to hire a seasoned Operations Coordinator to support the work of its Communications Department.
Talent Booker
Responsibilities: Bustle.com is seeking a booking editor to coordinate talent for various special projects including Bustle's "Extra Sharp" talk sh...
Advertising Sales Coordinator
Leading Technology magazine and online publisher is seeking a full-time Advertising Sales Coordinator for its media group.
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The energy of a newsroom. The pace of a trading floor. The buzz of a recent tech breakthrough. We work hard, and we work fast - while keeping up th...
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An independent, non-profit research organization that promotes policies to improve energy efficiency and reduce air pollution in transportation sector
Contracts and Licensing Assistant
W.W. Norton is seeking a Contracts and Licensing Assistant for its Contracts department.
Assistant Designer-Random House Children's Books
Company: Penguin Random House US Requisition ID: 707 The Random House Children's Books art team is seeking a highly motivated, creative indi...
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The U.S. Chamber of Commerce Foundation is seeking a live events content producer to change the way it develops, produces, and markets events.
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Public Info Officer should have strong knowledge of the Bronx, police issues and crime and past experience as a journalist covering these subjects.
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He/She will identify, foster &maintain strong relationships with advertising agencies & clients to sell targeted advertising across MNI's portfolio
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He/She will identify, foster and maintain strong relationships with advertising agencies &clients, to sell targeted advertising across MNI's portfolio
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Overall Function: Reporting into the Senior Manager of Creative & Member Services, the Direct Mail Copywriter plays a key role on the Development-M...
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Position: Digital Marketing Coordinator Reports to: Director, Audience Development Direct reports: none Job Description: FierceMarkets, a Questex L...
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PCOM is currently seeking a Web Content Specialist to work in the Office of Marketing and Communications.
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The Manager will oversee the Evaluation Reporting team and is responsible for timely delivery of the final work product to the hospitality client.
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Photo Albums for Quinceanera and Sweet 16
Beautiful Photo Albums for memories you will treasure forever.
Click on individual photos for product information or to order.
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Beautifully decorated Bible with gilded pages contains both the Old Testament and the New Testament. Choose from a lovely selection of co Click here
For Your Quinceanera or Sweet 16
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If you would like to read what our customers say about us, read some of our testimonials.
The Last Doll
|The Quinceanera Doll, also known as the Last Doll, is one of the traditions of the Quinceanera c


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My af is due tomorrow or wednesday. I tested yesterday during the day with a FRER and got a very light second line. I will test one more time in the morning. Anyone else?
Anyone testing in the morning?
Comments (9)
Make me feel better and let it sink in lol!
Xavier 3-29-08, Parker 2-28-10, Logan 2-3-12
Life is now complete! Loving every minute with my 3 boys!!
Xavier 3-29-08, Parker 2-28-10, Logan 2-3-12
Life is now complete! Loving every minute with my 3 boys!!
@NikiS0806 Yea I need one more test to really help me to realize it's real. I am pretty sure it will be positive again. The line yesterday was pink. It came up within a minute and was light but defintely there. @Julie I would wait a couple more days. It may still be too early. Sending lots of baby dust to you. The good thing is you probably still have a chance for a Feb baby if you aren't pregnant yet. Good Luck to everyone!
sweetcalig..congrats on the BFP be sure to let us know in the morning what your test says...i'm still hoping AF doesn't show her face tomorrow or this week..i'm going to retest on Wed if she hasn't made her appearance by then..it's so crazy though i've had a little bit of morning sickness
mwlbledsoe...thank you so much! I really appreciate that. I am crossing my fingers for you. Let me know when you do decide to test. And morning sickness...yuck. I never really have had it with any of my girls but have really been feeling it a bit lately. Good Luck to you and I hope that eases up.
I took another today, 10 dpo.. BFN. I was not actually TTC so if it's not happening, I'm totally ok w/it, I was actually hoping for Aug-Sept 2012 baby.. so I get to wait a little more to see if AF shows. Good luck to everyone! :)
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Morgantown, W.Va. (November 9, 2010) - The top riders of each class of the 2010 Can-Am Grand National Cross Country Series will be honored at the annual GNCC Awards Banquet. This year, the banquet will return to Lakeview Resort in Morgantown, W.Va. The top 10 ATV racers in each class will be honored on Friday, December 10 and the top 10 bike racers in each class will be awarded Saturday, December 11. The top 5 riders in each class get contingency awards.
The banquet will feature an array of Specialty Awards as well, including Rider of the Year, the Rough and Ready Pit Crew Award and the "Bad Ass" Award. Attendees are asked to nominate Rough and Ready Pit Crew and Bad Ass Award contenders by attaching a letter to their banquet form. The best letters will be read at the banquet.
The cost of the banquet is $33 for adults, $20 for children ages six to 10 and under five get in free. The celebrations will begin at 5:30 p.m. each day for Happy Hour and seating, and dinner will commence at 6:00 p.m. Advance registrations are required.
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I have a Chevrolet Express 3500, make 2000, mileage about 164000, engine size 5.7 L. I don't know why odometer display 9's digit only. I switched to Trip mode the Odometer works good. I tried to read trouble code form OBD II, but there are no trouble code. Anyone know this problem, please let me know
Monday, August 27th, 2007 AT 8:25 PM


text: AdChoices Terms of Use Privacy Policy Hide VIDEO Entertainment and Celebrities The Craziest Female Celebrity Meltdowns The Craziest Female Celebrity Meltdowns AskMen Editors April 23, 2013 Share Tweet 0 Shares In the world of Hollywood there have been many notable celebrity meltdowns, it's almost a daily occurrence, check out the top 10 craziest celebrity breakdowns and which ones never recovered. Comments Share your opinion Your name More Like This Basics Demystifying Bras, One Strap At A Time Read More Thrive How To Climb Your Way To A Killer Bod Read More Basics How To Make Your Own Wire Stripper Using Just Two Household Objects Read More Thrive Want To Burn 1,000 Calories In An Hour? Join The Godfather Of All Bootcamps Read More Thrive You'll Never Be The Hulk, But You Can Learn To Be Like Hawkeye Read More Basics A Sneakerhead's Guide To Lacing Up Your Kicks With Style Read More Around the Web Special Features Guy Gear The Best Watches Under $500 Read More Special Feature The Ultimate Guide To Hooking Up Online Read More


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On June 30 2008 (sent by arzhelpetrol) 9671 Views
unknown - 31/07
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POA, New York, United States
Fighting the good fight for good language with the most effective weapon there is: ridicule. Photographs on our wall of shame document trespasses against clarity, inadvertent blunders, and of course the ineffable grocer's apostrophe. Come for the pics, stay for the comments.
the truth lies in the details... magnify them!


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Pete Petrisko Goes All Bauhaus With Shake Some Dust
Pete Petrisko can't seem to shake this place.
The longtime downtown Phoenix creative type/former gallery owner/performance artist, who was recently reported dead by azcentral.com, moved to Tucson a few months back. However, he's been making frequent trips back to the Valley for on-location shoots for his new video project, Shake Some Dust. (According to Petrisko, the phrase is also 1930s slang for "to start moving.")
Petrisko, whose binary-chaos.net vidcast scored a New Times' Best of Phoenix award in 2009, started this endeavor a few months ago with his gal pal Rikki Lee. Some of the videos are straight-up music based while others feature artsy portrayals of the RPM Orchestra, a Bauhaus-like performance art/sound collage project founded and headed by Petrisko.
To see some more visual goodness, head over to www.vimeo.com/shakesomedust.
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Somebody please help I downloaded Ubuntu and I burned using Magic Iso.
I know a big amount about computers and a bit about linux.
Please help and if you need any information just ask.
Now on to the problem.
When I installed Ubuntu a few errors came up in the beginning but nothing big so it went on. Everything installed great. The background picture showed up I installed put my time keyboard and all of that. Then...I go to sign in. So I put my username and password in. I hit enter and I hear the sound..but ...after 2 seconds the screen screws up like when the cable on the T.V. skips and you see all the wierd colors. Then it goes back an askes me for my username and pass again!..ive wiped and reinstalled again and again. Ive tried multiple things. Please help!!


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Book your room at Crown Inn Hebden Bridge
Get an overview of this hotelRiverfront inn with free breakfast and restaurant
Situated on a river, this inn is 2.6 mi (4.2 km) from Gibson Mill and within 6 mi (10 km) of Stoodley Pike Monument and Gaddings Dam. Eureka The National Children's Museum and Bronte Parsonage Museum are also within 9 mi (15 km).
Property Features
A restaurant, a bar/lounge, and tour/ticket assistance are available at this smoke-free inn. Free breakfast and free WiFi in public areas are also provided.
Room Amenities
All 8 individually decorated rooms feature free WiFi and DVD players. For a bit of entertainment, guests will find LCD TVs with digital channels, and other amenities include premium bedding and coffee makers.Would you like to give us feedback? Share it! Opens in a new window
Crown Inn Hebden Bridge10 Crown Street Hebden Bridge England HX7 8EH
Hotel Amenities
Hotel Amenities
The inn offers a restaurant. A bar/lounge is on site where guests can unwind with a drink. A complimentary breakfast is offered each morning. Public areas are equipped with complimentary high-speed wireless Internet access.
Crown Inn Hebden Bridge is a smoke-free property.
- Bar/lounge
- Free breakfast
- Free WiFi
- Luggage storage
- Number of floors - 2
- Restaurant
- Smoke-free property
- Total number of rooms - 8
- Tours/ticket assistance
Available in all rooms: Free WiFi
Available in some public areas: Free WiFi
Room Amenities
- Coffee/tea maker
- Daily housekeeping
- Designer toiletries
- Digital TV service
- DVD player
- Free WiFi
- Hair dryer (on request)
- Individually decorated
- Individually furnished
- Phone
- Premium bedding
- Private bathroom
- Shower/tub combination
Where to Eat
A complimentary breakfast is served each morning between 8 AM and 10:30 AM.
Onsite venue - This restaurant specializes in international cuisine and serves lunch and dinner. Guests can enjoy drinks at the bar. A children's menu is available.
Nearby Things to Do
The recreational activities listed below are available either on site or nearby; fees may apply.
- Golfing nearby
- Mountain biking nearby
Hotel Policies
Check-in time starts at 2 PM
Check-in time ends at 9:30 PM
Check-out time is noon
Payment types
- Pets allowed
- Dogs only
- 1 per room
You need to know
Extra-person charges may apply and vary depending on hotel policy.
Government-issued photo identification and a credit card or cash deposit are required at check-in for incidental charges.
Special requests are subject to availability upon check-in and may incur additional charges. Special requests cannot be guaranteed.
- No onsite parking is available.
Hotel Name
- Crown Hebden Bridge
- Crown Inn Hebden Bridge
- Bar Place Hotel Hebden Bridge
- Crown Inn Hebden Bridge West Yorkshire
National Rating
This establishment has received its official star rating from VisitEngland, the National Tourist Board for England.


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I am chemist working in the field of computational drug design and development, especially chemoinformatics, QSAR and structural bioinformatics. Currently working in the join project between Structural Chemogenomics Laboratory and Chemoinformatics Laboratory (University of Strasbourg, Strasbourg, France). Other professional intersts: data mining, systems pharmacology, computational ADMETox.
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