41  5,744,650  42  Illustrative  of  suitable  organic  nitrogen  compounds  useful  for  scavenging  the  phosphorus  acidic  compounds  include  those  permissible  organic  nitrogen  compounds  described  in  Kirk-Othmer.  Encyclopedia  of  Chemical  Technology.  Fourth  Edition.  1996.  the  pertinent  portions  of  which  are  incorporated  herein  by  reference.  Optionally,  an  organic  nitrogen  compound  may  be  added  to the  hydroformylation  reaction  product  fluid  to  scavenge  the  acidic  hydrolysis  byproducts  formed  upon  hydrolysis  of  the  organopolyphosphite  ligand,  as  taught,  for  example.  in  U.S.  Pat.  No.  4,567  306,  and  copending  U.S.  patent  appli› cation  Ser.  Nos.  (08n56,501)  and  (08n53.505).  referred  to  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  herein.  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› sium.  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.  Illustrative  organic  nitrogen  compounds  include  e.g .•  trialkylamines,  such  as  triethylamine,  tri-n-propylamine,  tri› n-butylamine,  tri-iso-butylamine,  tri-iso-propylamine,  tri-n› hexylamine.  tri-n-octylamine,  dimethyl-iso-propylamine,  dimethyl-hexadecylamine,  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  triethanolamine,  N-methyl-di-ethanolarnine.  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› t o l  u id  in e,  N-methyldiphenylamine,  N ,N› dimethylbenzylamine,  $^{N,N-dimethyl-1-naphthylamine. }$and  the like.  Compounds  containing  two  or  more  amino  groups,  such  as  N,N.N’  .N’-tetramethylethylene  diamine  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  hydroformylation  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.  herein.  Such  organic  nitrogen  compounds  may  be  used  to  react  with  and  to  neutralize  the  acidic  compounds  by  form› ing  conversion  product  salts  therewith,  thereby  preventing  the  rhodium  from  complexing  with  the  acidic  hydrolysis  byproducts  and  thus  helping  to  protect  the  activity  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.  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.  liquid  catalyst  recycle  hydroformylation  process  that  has  been  removed  from  the  reaction  zone  at any  time  prior  to or  after  separation  of the  aldehyde  product  therefrom.  More  preferably  said  aqueous  buffer  treatment  involves  treating  all  or  part  of the  reaction  product  fluid  obtained  after  distillation  of as  much  of the  aldehyde  product  desired,  e.g.  prior  to or  during  the  recycling  of said  reaction  product  fluid  to the  reaction  zone.  For  instance,  a  preferred  mode  would  be to  continuously  pass  all or  part  (e.g.  a  slip  stream)  of the  recycled  reaction  product  fluid  that  is  being  recycled  to the  reaction  zone  through  a  liquid  extractor  containing  the  aqueous  buffer  solution  just  before  said  catalyst  containing  residue  is to  re-enter  the  reaction  zone. 