35  5,763,670  36  The  amount  of  organic  nitrogen  compound  that may  be  present  in the  reaction  product  fluid  for  scavenging  the  phosphorus  acidic  compounds  present  in the  hydrofonnyla- tion  reaction  product  fluids  of the  this  invention  is  typically  sufficient  to  provide  a  concentration  of at least  about  0.0001  moles  of free  organic  nitrogen  compound  per liter  of reac› tion  product  fluid.  In  general  the ratio  of  organic  nitrogen  compound  to total  organophosphite  ligand  (whether  bound  with  rhodium  or  present  as free  organophosphite)  is  at  least  about  0.1:1  and even  more  preferably  at least  about  0.5:1.  The upper  limit  on the  amount  of  organic  nitrogen  com- Optionally,  an  organic  nitrogen  compound  may  be  added  to the  hydrofonnylation  reaction  product  fluid  to  scavenge  the  acidic  hydrolysis  byproducts  formed  upon  hydrolysis  of  the  organophosphite  ligand.  as  taught,  for  example,  in U.S.  Pat  No. 4,567  306.  Such  organic  nitrogen  compounds  may  be used  to  react  with and  to  neutralize  the acidic  compounds  by  forming  conversion  product  salts  therewith,  thereby  preventing  the  rhodium  from  complexing  with  the  acidic  hydrolysis  byproducts  and thus  helping  to  protect  the activ› ity of  the  metal,  e.g.,  rhodium,  catalyst  while  it is  present  in  the  reaction  zone  under  hydroformylation  conditions.  The  choice  of the  organic  nitrogen  compound  for this  function  is,  in  part,  dictated  by the  desirability  of  using  a  basic  material  that is  soluble  in the  reaction  medium  and does  not tend  to  catalyze  the  formation  of  aldols  and other  condensation  products  at a  significant  rate or  to  unduly  react  with  the  product  aldehyde.  lliustrative  of  suitable  organic  nitrogen  compounds  include  those  permissible  organic  nitrogen  compounds  described  in  Kirk-Othmer,  Encyclopedia  of  Chemical  Technology,  Fourth  Edition,  1996,  the  pertinent  portions  of  which  are  incoiporated  herein  by  reference.  Preferred  organic  nitrogen  compounds  useful  for scav- enging  the  phosphorus  acidic  compounds  present  in the  hydrofonnylation  reaction  product  fluids  of the  this inven› tion are  heterocyclic  compounds  selected  from  the  group  consisting  of  diazoles,  triazoles.  diazines  and  triazines,  such  as  those  disclosed  and  employed  in  copending  U.S. patent  application  Ser. No.  08n56.789.  filed  on an  even  date  herewith.  the  disclosure  of  which  is  incoipOrated  herein  by  reference.  For  example,  benzimidazole  and  benztriazole  are  preferred  candidates  for such  use.  Preferred  buffer  systems  are  phosphate  buffers  and citrate  buffers,  e.g.  monobasic  phosphate/dibasic  phosphates  of an  alkali  metal  and  citrates  of an  alkali  metal.  More  preferred  are  buffer  systems  consisting  of  mixtures  of the  monobasic  phosphate  and the  dibasic  phosphate  of  sodium  or  potas› silun.  The  aqueous  buffer  solutions  employable  in this  invention  may  comprise  any  suitable  buffer  mixture  containing  salts of  oxyacids.  the  nature  and  proportions  of  which  in the  mixture,  are such  that the  pH of  their  aqueous  solutions  may  range  from  3  to 9.  preferably  from  4 to  8  and more  preferably  from  4.5 to  7.5.  In  this  context  suitable  buffer  systems  may  include  mixtures  of  anions  selected  from  the  group  consisting  of  phosphate.  carbonate,  citrate  and borate  compounds  and  cations  selected  from  the group  consisting  of  ammonium  and  alkali  metals,  e.g.  sodium,  potassium  and  the  like.  Such  buffer  systems  and/or  methods  for their  preparation  are well  known  in the  art.  lliustrative  organic  nitrogen  compounds  include  e.g.,  trialkylarnines,  such  as  triethylamine,  tri-n-propylamine,  tri› n-butylarnine,  tri-iso-butylarnine.  tri-iso-propylarnine.  tri-n› hexylarnine,  tri-n-octylarnine,  dimethyl-iso-propylarnine.  dimethyl-hexadecylarnine,  methyl-di-n-octylarnine.  and the  like. as  well as  substituted  derivatives  thereof  containing  one  or  more  noninterfering  substituents  such as  hydroxy  groups.  for  example  triethanolarnine.  N-methyl-di-ethanolamine,  tris-(3-hydroxypropyl)-amine.  and the  like.  Heterocyclic  amines  can also  be used  such  as  pyridine.  picolines.  lutidines.  collidines,  N-methylpiperidine.  N-methylmorpholine.  N-2’-hydroxyethylmorpholine,  quinoline.  iso-quinoline,  quinoxaline.  acridien,  quinuclidine.  as well  as,  diazoles,  triazole.  diazine  and  triazine  compounds,  and the  like. Also  suitable  for  possible  use  are  aromatic  tertiary  amines,  such  as  N.N› dimethylaniline.  N.N-diethylaniline.  N,N-dimethyl-p› toluidine.  N-methyldiphenylamine.  N ,N  - dimethylbenzylamine,  N,N-dimethyl-1-naphthylarnine.  and  the like.  Compounds  containing  two or  more  amino  groups.  such  as  N,N.N’  .N’-tetramethylethylene  diarnine  and trieth› ylene  diamine  (i.e.  1.4-diazabicyclo-[2.2.2]-octane)  can also  be  mentioned.  Such  organic  nitrogen  compounds  may  contain  from  2 to  30  carbon  atoms,  and  preferably  from  2 to 24  carbon  atoms.  Primary  amines  should  be  excluded  from  use as  said  organic  nitrogen  compounds.  Preferred  organic  nitrogen  compounds  should  have  a  distribution  coefficient  that favors  solubility  in  the  organic  phase:  In  general  more  preferred  organic  nitro- gen  compounds  useful  for  scavenging  the  phosphorus  acidic  compounds  present  in the  hydrofonnylation  reaction  prod› uct fluid  of this  invention  include  those  having  a  pKa value  within–3  of the  pH  of the  aqueous  buffer  solution  employed.  Most  preferably  the pKa  value  of the  organic  nitrogen  compound  will be  essentially  about  the same  as the  pH of  the  aqueous  buffer  solution  employed.  Of  course  it  is to  be  understood  that while  it  may be  preferred  to  employ  only  one such  organic  nitrogen  compound  at a time  in any  given  hydrofonnylation  process.  if  desired,  mixtures  of two  or  more  different  organic  nitrogen  compounds  may  also be  employed  in any  given  processes.  Moreover.  success  in  removing  phosphorus  acidic  com› pounds  from  the  reaction  product  fluid  may be  determined  by  measuring  the rate  degradation  (consumption)  of the  organopolyphosphite  ligand  present  in the  hydroformylation  reaction  medium.  In  addition  as  the  neutralization  and  extraction  of  phosphorus  acidic  compounds  into the  aqueous  buffer  solution  proceeds,  the pH  of the  buffer  solution  will  decrease  and  become  more  and more  acidic.  When  the buffer  solution  reaches  an  unacceptable  acidity  level  it  may simply  be  replaced  with  a  new buffer  solution.  Typically  maximum  aqueous  buffer  solution  concentra› tions  are only  governed  by  practical  considerations.  As  noted.  treatment  conditions  such  as  temperature,  pressure  and  contact  time  may  also vary  greatly  and any  suitable  combination  of such  conditions  may be  employed  herein.  In  general  liquid  temperatures  ranging  from  about  20°  C.  to  about  80°  C. and  preferably  from  about  25°  C. to  about  60°  C.  should  be  suitable  for most  instances.  although  lower  or  higher  temperatures  could  be  employed  if  desired.  Normally  the  treatment  is  carried  out under  pressures  ranging  from  ambient  to  reaction  pressures  and the  contact  time may  vary  from  a  matter  of  seconds  or  minutes  to a few  hours  or  more.  Thus  it  is to  be  understood  that  the  metal› organopolyphosphite  ligand  complex  catalyst  containing  reaction  product  fluid  to be  treated  with the  aqueous  buffer  solution  may  contain  in  addition  to the  catalyst  complex  and  its  organic  solvent.  aldehyde  product.  free  phosphite  ligand.  unreacted  olefin.  and any  other  ingredient  or  additive  con› sistent  with  the  reaction  medium  of the  hydroformylation  process  from  which  said  reaction  product  fluids  are  derived.  aqueous  buffer  solution  just before  said  catalyst  containing  residue  is to  re-enter  the  reaction  zone. 