aqueous buffer solution just before said catalyst containing residue is to re-enter the reaction zone. 

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. 

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 15 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. 

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. 

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. 

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. 

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. 

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. 

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. 

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. 

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. 

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- 

