5  US 6,908,603 B2  6  As used herein, the terms "solution of zeolite seed" and  "zeolite initiator" shall include any aqueous solution con› taining silica, alumina and soda that either allows a zeolite  Y  crystallization process that would not occur in the absence  of the seed material or shortens significantly the zeolite  Y  crystallization process that would occur in the absence of the  seed material. Again, the zeolite  Y  seed solution as described  above does not contain crystalline zeolite  Y.  A  solution of matured seeds which has become clouded or  gelled can be made clear by adding additional sodium  silicate solution, the amount of sodium silicate solution  being effective to assure that the previously clouded or  gelled solution will maintain its clarity when aged for 48  hours or longer without cooling. In this case, the sodium  silicate enriched seed mixture is optionally, but preferably,  heated and then permitted to age at ambient temperature.  Heating after addition of sodium silicate is preferred because  clarification will take place in a shorter time.  In an alternative method of forming a microsphere with a  reduced reactive alumina content, the process of acid leach› ing a metakaolin as described in EP 068,817 can be used.  According to the process as described therein, a method of  manufacturing a crystalline zeolite of the ZSM family  comprises the initial step of treating an aluminosilicate such  as metakaolin with a strong acid at a temperature and for a  time sufficient to extract at least part of the aluminum oxide  content of the aluminosilicate and increase the molar ratio of  SiO$_{2}$ :Al$_{2}$O$_{3 }$ in the aluminosilicate to a value not less than  10:1. The acid used preferably has a  pKa  value not greater  The initial microspheres are made by spray drying a feed  mixture containing hydrated kaolin, metakaolin, or kaolin  calcined through the characteristic exothermic reaction and  optionally colloidal silica and/or silica sol and/or sodium  silicate binder. Mixtures of the kaolin forms can also be  used. Enhancing the silica level in the preformed micro› sphere by including silica-rich components or using more  silicate binder increases the overall reactive  Si0$_{2}$/Al$_{2}$0$_{3 }$ ratio, resulting in an increased level of crystallized  ZSM-5.  If a silicate binder is used such as sodium silicate, and if  desired, sodium in the microspheres can be washed out at  low pH, e.g., pH of 3. The spray dried microspheres are  washed and then calcined to form precursor porous micro› spheres in which any of the hydrous kaolin and metakaolin  is converted to spinel or mullite. The amount of metakaolin  present in the calcined precursor microspheres needs to be  minimized, i.e. less than 10%, to provide the desired reactive  SiO$_{2}$/Al$_{2}$O$_{3 }$ ratio and allow formation of ZSM-5 crystals.  Typically, the calcined precursor microspheres will have a  BET surface area of less than 200 m $^{2}$/g.  Preparation of zeolite  Y  seed solution While it is useful to  use crystallized zeolite  Y  seeds in this invention, the zeolite  Y  seed solution is most usefully obtained by processes  disclosed in U.S. Pat. No. 4,493,902 and U.S. Pat. No.  4,631,262, the entire contents of which are herein incorpo› rated by reference. As disclosed in U.S. Pat. No. 4,631,262,  appropriate quantities of sodium silicate, sodium aluminate  and sodium hydroxide are mixed, preferably in a controlled  manner, hereinafter described, heating the resulting mixture  for a time sufficient for the seeds to mature but insufficient  for cloudiness to occur, and thereafter adding to the matured  solution a portion of the sodium silicate reactant that would  normally be included in the reaction slurry including the  porous microspheres of calcined kaolin. The sodium silicate  added to the matured seed solution is preferably at ambient  temperature when it is added to the solution. The amount of  sodium silicate solution added to the solution of matured  clear seeds is effective to result in a seed solution which will  maintain its clarity when aged for 48 hours or longer  (without cooling). In effect, enrichment of a clear solution of  matured seeds with sodium silicate functions to quench the  undesirable reaction(s) that may take place and which would  result in undesired cloudiness. The seed solution is amor› phous and does not exhibit any detectable crystallinity by  x-ray diffraction.  Preparation of the fluid cracking additive catalyst, in  accordance with this invention, involves an initial step of  preparing microspheres comprising hydrous kaolin,  metakaolin, kaolin calcined undergone through characteris› tic exothermic reaction, or mixtures of the kaolin forms.  Optionally, colloidal silica, silica sol or sodium silicate  binder can be added. The microspheres are calcined to  convert any hydrous kaolin and metakaolin that may be  present to spinel and/or mullite. In case where hydrous  kaolin and metakaolin are not present, high calcination  temperature may not be required.  It is important that the  microspheres prior to crystallization contain only a mini› mum of reactive alumina. Accordingly, the calcined micro- spheres will have a metakaolin content that is less than 10  wt. %. Preferably the metakaolin content in the calcined  microspheres is less than 5 wt.%. Spinel and mullite contain  little reactive alumina, which is determined by the amount of  alumina solublized in a 1/1 hydrochloric acid/water solution  following a thirty-minute digestion at 115°  C.  The precursor microspheres, having a minimum of reac› tive alumina achieved either by high temperature calcination  of kaolin or acid leaching of metakaolin, are reacted with  zeolite  Y  seed solution and an alkaline sodium silicate  solution. The zeolite  Y  seed solution is one intended for use  in initiating crystallization of synthetic crystalline zeolite of  the Y-type. ZSM-5 seeds are not used in the reaction.  than 2 and most preferably has a  pKa  value of less than 0.  Suitable acids include hydrochloric acid, sulphuric acid,  nitric acid, and orthophosphoric acid. The acid should be  used at a concentration of at least 2M, preferably at least SM,  and most preferably at least 7M. The optimum acid concen› tration depends upon the weight ratio of acid solution to dry  aluminosilicate and upon the type of acid used and thus the  nature of the aluminum salt formed and its solubility in the  acid solution. The weight ratio of acid solution to dry  aluminosilicate is preferably at least 5:1. The acid treatment  is preferably performed at a temperature in the range of from  50°  C. to 120°  C. for at least 1 hour, and under conditions  such that the molar ratio of SiO$_{2}$ :Al$_{2}$ O$_{3 }$ in the acid-treated  aluminosilicate is in the range 10---200: 1. Usually, after the  acid treatment the molar ratio of  Si0$_{2}$:Al$_{2}$0$_{3 }$ in the alumi› nosilicate is in the range 10-50: 1.  FIG. 1 is  an  XRD  pattern of an as crystallized  ZSM-5- containing microsphere formed by the process of this inven› tion.  microspheres is achieved by minimizing the amount of the  reactive alumina in the kaolin microsphere by calcination at  elevated temperatures. Mixing the calcined kaolin micro› spheres with a silica source and a seed solution used for  in-situ FCC Y synthesis and heating results in growth of  ZSM-5 crystals on the microsphere. The in-situ ZSM-5 has  use as an FCC additive and catalyst for fine chemical  processes such as organic compound manufacture.  BRIEF DESCRIPTION OF  IBE  DRAWING  DETAILED DESCRIPTION OF  IBE  INVENTION 