Method for separating a water soluble noble metal catalyst from a noble metal catalyzed hydroformylation reaction

A method for separating a water soluble Group VIII noble metal catalyst from the crude reaction product of a noble metal-catalyzed hydroformylation reaction run in aqueous solution, in an aqueous emulsion or as an aqueous suspension, the crude reaction product including an aqueous phase containing a water soluble Group VIII noble metal-ligand complex catalyst, and an organic phase containing unreacted olefin feed and an organic hydroformylation reaction product, which comprises: (a) contacting the crude reaction product with a hydrophobic membrane capable of allowing a substantial portion of the unreacted olefin feed and the organic hydroformylation reaction product to pass therethrough while retaining a substantial portion of the water soluble Group VIII noble metal-ligand complex catalyst; (b) removing unreacted olefin feed and organic hydroformylation reaction product which passes through the hydrophobic membrane as permeate; and (c) retaining the water soluble Group VIII noble metal-ligand complex catalyst as retentate.

This invention relates to a method for separating water soluble Group VIII 
noble metal-ligand complex catalysts from the crude reaction product of a 
noble metal-catalyzed hydroformylation reaction by contacting the crude 
reaction product to a hydrophobic membrane whereby the water soluble Group 
VIII noble metal-ligand complex catalysts are retained by the membrane as 
retentate, and the unreacted olefin feed and the hydroformylation reaction 
product are passed through the membrane as permeate. 
BACKGROUND OF THE INVENTION 
Hydroformylation reactions involve the preparation of oxygenated organic 
compounds by the reaction of carbon monoxide and hydrogen (synthesis gas) 
with carbon compounds containing olefinic unsaturation. The reaction is 
typically performed in the presence of a carbonylation catalyst and 
results in the formation of compounds, for example, aldehydes, which have 
one or more carbon atoms in their molecular structure than the starting 
olefinic feedstock. By way of example, higher alcohols may be produced in 
the so-called oxo process by hydroformylation of commercial C.sub.6 
-C.sub.12 olefin fractions to an aldehyde-containing oxonation product, 
which on hydrogenation yields the corresponding C.sub.7 -C13 saturated 
alcohols. The oxo process is the commercial application of the 
hydroformylation reaction for making higher aldehydes and alcohols from 
olefins. The crude product of the hydroformylation reaction will contain 
catalyst, aldehydes, alcohols, unreacted olefin feed, synthesis gas and 
by-products. 
A variety of transition metals catalyze the hydroformylation reaction, but 
only cobalt and rhodium carbonyl complexes are used in commercial oxo 
plants. The reaction is highly exothermic; the heat release is ca 125 
kj/mol (30 kcal/mol). The position of the formyl group in the aldehyde 
product depends upon the olefin type, the catalyst, the solvent, and the 
reaction conditions. Reaction conditions have some effect and, with an 
unmodified cobalt catalyst, the yield of straight chain product from a 
linear olefin is favored by higher carbon monoxide partial pressure. In 
the hydroformylation of terminal olefinic hydrocarbons, the use of a 
catalyst containing selected complexing ligands, e.g., tertiary 
phosphines, results in the predominant formation of the normal isomer. 
In commercial operation, the aldehyde product is usually used as an 
intermediate which is converted by hydrogenation to an alcohol or by 
aldolization and hydrogenation to a higher alcohol. The 
aldol-hydrogenation route is used primarily for the manufacture of 
2-ethylhexanol from propylene via n-butyraldehyde. 
The hydroformylation reaction is catalyzed homogeneously by carbonyls of 
Group VIII metals but there are significant differences in their relative 
activities. Roelen, using a cobalt catalyst, discovered hydroformylation 
in 1938. Dicobalt octacarbonyl, CO.sub.2 (CO).sub.8, which either is 
introduced directly or formed in situ, is the primary conventional oxo 
catalyst precursor. using an unmodified cobalt catalyst, the ratio of 
linear to branched aldehyde is relatively low. 
Much oxo research in the past 25 years has been directed to improving 
reaction selectivity to the linear product. Introduction of an 
organophosphine ligand to form a complex, e.g., CO.sub.2 (CO).sub.6 
[P(n-C.sub.4 H.sub.9).sub.3 ].sub.2, significantly improves the 
selectivity to the straightchain alcohol. 
Recent developments of low pressure rhodium catalyst systems have been the 
subject of a considerable body of patent art and literature, and 
rhodium-triphenyl phosphine systems have been widely, and successfully, 
used commercially for the hydroformylation of propylene feedstocks to 
produce butyraldehyde. 
The first commercial oxo process to employ a rhodium-modified catalyst was 
developed by Union Carbide, Davy Powergas, and Johnson Matthey. In this 
application, the complexed rhodium catalyst is dissolved in excess ligand 
and the reaction is run at relatively low pressures and temperatures as 
compared to a conventional oxo process. The ratio of normal to iso isomers 
is high relative to conventional oxo processes and so is favored as a 
process for the production of n-butyraldehyde. 
A recent process commercialization has been that of Rhone-Poulenc and 
Ruhrchemie which produces butyraldehyde from propylene but the ligand is a 
sulfonated triphenylphosphine and is utilized as a water soluble sodium 
salt. Turnover rates are less than in the all-organic system, but the 
normal to iso ratios are high and the catalyst may be separated easily 
from the reaction product by separation of the aqueous layer containing 
the catalyst and the organic layer which constitutes the product. 
In the formation of linear aldehydes using a ligand-modified 
rhodium-catalyzed homogenous process, the reactor comprises the rhodium 
complex catalyst, excess triphenylphosphine and a mixture of product 
aldehydes and condensation by-products. The product aldehyde may be 
recovered from the mixture by volatilization directly from the reactor or 
by distillation in a subsequent step. The catalyst either remains in or is 
recycled to the reactor. However, the complex catalyst and 
triphenylphosphine ligand are slowly deactivated and eventually the spent 
catalyst is removed for recovery of rhodium and reconversion to the active 
catalyst. This process, although effective for lower molecular weight 
aldehyde production, is not favored for higher molecular weight aldehydes 
which are higher boiling, as distillation temperatures needed for aldehyde 
recovery are higher and catalyst deactivation is accelerated. 
The aqueous ligand system is also very effective for propylene but higher 
molecular weight olefin feeds are not sufficiently soluble in the aqueous 
catalyst medium to allow acceptable rates of aldehyde formation. Thus, 
although separation of the higher molecular weight aldehyde should be more 
facile than the all-organic system, the slow rates preclude commercial 
acceptability. 
In some cases, such as where the products of the reaction are relatively 
high boiling or where the olefin feed is not sufficiently soluble in water 
to permit satisfactory reaction rates, neither the process where the 
products are removed from the catalyst by distillation or stripping nor 
where the products are decanted from an aqueous catalyst solution may be 
utilized successfully. In such cases, it may be advantageous to utilize an 
aqueous medium to contain the catalyst and add a surfactant to enhance 
phase contacting so as to improve rate and selectivity to the desired 
products. This type of process is called "Phase Transfer Catalysis." 
However, when the surfactant is added, some carry-over of the noble metal 
into the organic phase at the conclusion of the process often results. 
The present inventors have discovered that when they satisfactorily 
hydroformylated olefins in the presence of water soluble Group VIII noble 
metal-ligand complex catalysts using an aqueous-organic medium enhanced by 
surfactants, the catalyst can be recovered quantitatively from a crude 
reaction product which includes both an aqueous phase and an organic phase 
by employing membrane separation either internal or external to the 
hydroformylation reactor. 
It has been known to use membranes to separate catalysts from an aqueous 
solution. An example is set forth in European Patent No. 0 263 953, 
published on Aug. 29, 1986 (assigned to Ruhrchemie Aktiengesellschaft), 
which discloses a process for separating rhodium complex compounds, which 
contain water-soluble organic phosphines as ligands, from aqueous 
solutions in which excess phosphine ligand and, if necessary, other 
components are also dissolved, and is characterized by the fact that the 
aqueous solution is subjected to a membrane separation process. According 
to this process, volatile organic substances are separated from the 
solution prior to conducting the membrane separation process. A typical 
membrane for use in this process is a cellulose acetate membrane. This 
process only involves the separation of watersoluble ligands and noble 
metal catalyst from an aqueous solution. As such, this separation process 
does not pertain to the separation of a water soluble noble metal catalyst 
and a water soluble ligand from an organic-aqueous emulsion, dispersion or 
suspension produced from the hydroformylation process. 
Another patent which utilizes cellulose acetate, silicone rubber, 
polyolefin or polyamide membranes in the separation of catalysts from high 
boiling byproducts of the hydroformylation reaction is Great Britain 
Patent No. 1312076, granted on May 15, 1970. According to this patent the 
aldehydes produced during the hydroformylation process are continuously 
withdrawn as an overhead vapor stream. The liquid stream containing the 
heavy by-products with the catalyst is passed over a membrane wherein 
approximately 78-94.3% of the catalyst is retained and the heavy 
by-products permeated. This is an unacceptably low level of catalyst 
retention which is overcome by the process of the present invention. 
In like manner, Great Britain Patent No. 1432561, granted on Mar. 27, 1972, 
(assigned to Imperial Chemical Industries Ltd.) discloses a process for 
the hydroformylation of olefins which comprises reacting an olefin at 
elevated temperature and pressure with CO and H.sub.2 in the presence of a 
compound of a group VIII metal and a biphyllic ligand of a trivalent P, As 
or Sb to give a crude liquid hydroformylation product containing an 
aldehyde and/or an alcohol, separating the aldehyde and/or alcohol from 
the crude product and leaving a liquid, bringing the liquid after 
separation of the Group VIII metal compound and free from aldehyde and 
alcohol under reverse osmosis conditions into contact with one side of a 
silicone rubber semi-permeable membrane in which the polymer chains have 
been at least partly crosslinked by gamma radiation whereby the liquid 
retained by the membrane contains a higher concentration of Group VIII 
metal compounds and/or biphyllic ligand than the original liquid. 
In the article by Gosser et al., entitled "Reverse Osmosis in Homogeneous 
Catalysis," Journal of Molecular Catalysis, Vol. 2 (1977), pp. 253-263, a 
selectively permeable polyimide membrane was used to separate soluble 
transition metal complexes from reaction mixtures by reverse osmosis. For 
example, separation of cobalt and rhodium complexes from hydroformylation 
products of 1-pentene. That is, a solution of 0.50 grams of 
RhH(CO)(PPh.sub.3).sub.3 in 40 ml of benzene and 10 ml of 1-pentene was 
stirred at 50.degree. C. with a CO/H.sub.2 mixture at ca. 4 atm pressure 
until no further pressure drop occurred. The pentene was completely 
converted to aldehydes according to proton nmr analysis. The solution was 
permeated through a polyimide membrane under 68 atm nitrogen pressure. The 
permeate (4.5 g passed in 2 min.) showed only 9% of the original rhodium 
concentration by X-ray fluorescence. 
The permeation rate of rhodium as set forth above, i.e., 9%, is considered 
unacceptable. The rhodium catalyst should be retained in an amount of 
greater than 99.5% to be a commercially feasible process. 
Another example of the use of membranes to separate metal catalysts from 
hydroformylation products is set forth in Dutch Patent No. 8700881, 
published on Nov. 1, 1988. The method disclosed therein relates to one 
which improves the efficiency of membrane separation of hydroformylation 
products from expensive organometallic catalyst containing reaction 
mixtures. In Dutch Patent No. 8700881 a polydimethylsiloxane membrane 
having a thickness of 7 microns applied to a Teflon.RTM. support was used 
in the separation of a reaction mixture containing C.sub.9 -C.sub.15 
alcohols, a homogeneous catalyst system comprising an organometallic 
complex of a transition metal from Group VIII or VIIA or Va of the 
Periodic Table, e.g., a tricarbonyl(triphenylphosphine) cobalt catalyst, 
and 40% low-viscosity lubricating oil (an antiswelling or de-swelling 
agent). At a flow of 133 kg/m.sup.2 -day, the cobalt contents in the feed, 
retentate, and permeate were 600, 910, and 18 ppm, versus 840, 1930, and 
160 ppm, respectively, for a mixture without the deswelling agent. This 
process is directed to the separation of product from a reaction mixture 
containing a homogeneous catalyst system by means of a membrane, whereas 
the present invention is directed to a heterogeneous catalyst system 
comprising both an organic and an aqueous layer. The ligands disclosed in 
Dutch Patent No. 8700881 are all organic soluble ligands, e.g., 
triphenylphosphine, tri-n-alkylphosphine or acetyl acetonate, whereas 
those used in the present invention are water soluble ligands. Critical to 
the process of Dutch Patent No. 8700881 is the addition of a de-swelling 
agent to the reaction mixture which assists in the separation of the 
products from the reaction mixture. 
Each of the aforementioned processes for removing metal catalysts from 
crude hydroformylation reaction products are both costly in terms of 
unrecovered catalyst and, as such, would require further expensive 
treatment of the streams to recover catalyst. 
The present invention provides a ligand and membrane combination which 
allows for the retention of over 99% of the noble metal catalyst from the 
hydroformylation reaction product which is passed over the membrane. 
Moreover, the hydrophobic membrane used in accordance with the process of 
the present invention remains thermally and hydrolytically stable during 
separation. 
The present inventors have been able to demonstrate that an 
aqueous-organic-catalyst mixture can be separated from the crude 
hydroformylation product mixture using a hydrophobic membrane and a 
perstracting organic solvent. This novel process permits the organic 
products to permeate through the membrane, while retaining the rhodium 
catalyst and all other water soluble components. 
The present invention also provides many additional advantages which shall 
become apparent as described below. 
SUMMARY OF THE INVENTION 
The present invention relates primarily to a process wherein an aqueous 
emulsion, suspension or dispersion of a crude reaction product comprising 
a water soluble Group VIII noble metal-ligand complex catalyst, unreacted 
olefin feed and a hydroformylation reaction product is contacted with or 
passed over a hydrophobic membrane capable of retaining the water soluble 
rhodium-ligand complex catalyst as retentate and permitting the unreacted 
olefin feed and organic hydroformylation reaction product comprising 
higher aldehydes and higher alcohols to permeate therethrough. Optionally, 
the aqueous emulsion, suspension or dispersion is first settled before 
delivering the organic phase, i.e., the hydroformylation reaction product 
with smaller amounts of the water soluble Group VIII noble metal-ligand 
complex catalyst, to the membrane for separation. It is also optional to 
add a surfactant to the noble metal-catalyzed hydroformylation reaction. 
Typical olefins used in the aforementioned hydroformylation process are 
C.sub.4 to C.sub.20, preferably C.sub.6 to C.sub.16. 
The following is a preferred method for separating a water soluble noble 
metal catalyst from the crude reaction product of a noble metal-catalyzed 
hydroformylation reaction run in aqueous solution, in an aqueous emulsion 
or as an aqueous suspension. The crude reaction product includes an 
aqueous phase containing a water soluble Group VIII noble metal-ligand 
complex catalyst, and an organic phase containing unreacted olefin feed 
and an organic hydroformylation reaction product. The method comprises the 
following steps: (a) contacting the crude reaction product with a 
hydrophobic membrane capable of allowing a substantial portion of the 
unreacted olefin feed and the organic hydroformylation reaction product to 
pass therethrough while retaining a substantial portion of the water 
soluble Group VIII noble metal ligand complex catalyst; (b) removing 
unreacted olefin feed and organic hydroformylation reaction product which 
pass through the hydrophobic membrane as permeate; and (c) retaining the 
water soluble Group VIII noble metal-ligand complex catalyst as retentate 
in an amount of about 99% or greater. 
The noble metal-catalyzed hydroformylation reaction preferably includes the 
steps of: reacting an olefin with hydrogen and carbon monoxide in the 
presence of a water soluble Group VIII noble metal-ligand complex 
catalyst, at a temperature in the range between about 80.degree. to 
125.degree. C. to produce an aldehyde having a normal aldehyde to isomeric 
aldehyde ratio in the range of between about 0.5:1 to about 80:1. 
The ligand is preferably at least one compound selected from the group 
consisting of: Na-p-(diphenylphosphino)benzoate, 
Na-m-(diphenylphosphino)benzenesulfonate, tri-(sodium 
m-sulfophenyl)-phosphine, and Na-p-diphenylphosphino benzene sulfonic 
acid. 
The surfactant is preferably at least one compound selected from the group 
consisting of cetyltrimethylammonium bromide, sodium laurate, sodium 
stearate, linear dodecylbenzene sulfonate, and Na-p-toluenesulfonic acid. 
The hydrophobic membrane is preferably one membrane selected from the group 
consisting of: a high density polyethylene crosslinked membrane, a natural 
latex rubber membrane, a polyvinylidene difluoride membrane, a 
polychlorotrifluoroethylene membrane, a polytetrafluoroethylene membrane, 
a crosslinked bromobutyl rubber membrane, and a crosslinked copolymer of 
isobutylene and p-bromomethyl styrene. 
A further object of the present invention is a method for producing higher 
aldehydes and higher alcohols which comprises: (a) hydroformylating an 
olefinic feedstock with synthesis gas in the presence of a water soluble 
Group VIII noble metal-ligand complex catalyst to form a crude reaction 
product comprised of an organic phase containing higher aldehydes, higher 
alcohols and secondary products and an aqueous phase containing a water 
soluble Group VIII noble metal-ligand complex catalyst; (b) removing the 
water soluble noble metal catalyst from the crude reaction product by 
feeding the crude reaction product to a membrane separator which comprises 
a hydrophobic membrane capable of allowing a substantial portion of the 
hydroformylation product, i.e., higher aldehydes, higher alcohols and 
secondary products, and unreacted olefin feed to pass therethrough while 
retaining a substantial portion of the water soluble Group VIII noble 
metal-ligand complex catalyst; (c) recovering the higher aldehydes, higher 
alcohols and secondary products as permeate; (d) retaining the water 
soluble Group VIII noble metal-ligand complex catalyst as retentate; and 
(e) recycling the retained water soluble Group VIII noble metal-ligand 
complex catalyst to the hydroformylation step (a). 
Optionally, the aforementioned method includes the additional step wherein 
the crude reaction product is separated into an aqueous layer and an 
organic layer before it is fed to the membrane separator. The organic 
layer is thereafter fed to the membrane separator and the aqueous layer 
and retentate from the membrane separator are recycled to the 
hydroformylation reactor. 
The noble metal-catalyzed hydroformylation reaction typically involves the 
reacting of a linear .alpha.-olefin with carbon monoxide, and hydrogen in 
the presence of a water soluble Group VIII noble metal-ligand complex 
catalyst, at a temperature in the range between about 80.degree. to 
125.degree. C. and a pressure of 1 to 100 atmospheres to produce an 
aldehyde having a normal to iso ratio in the range of between about 0.5:1 
to about 80:1. 
Other and further objects, advantages and features of the present invention 
will be understood by reference to the following specification in 
conjunction with the annexed drawings, wherein like parts have been given 
like numbers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hydroformylation is a process of converting olefins to a product of one or 
more additional carbon numbers by the addition of carbon monoxide and 
hydrogen to the double bond(s) of the olefin in the presence of a catalyst 
at elevated temperatures and pressures. A typical hydroformylation process 
is demonstrated below: 
##STR1## 
At a temperature of 100.degree. C. and a pressure of 68.03 kg (150 lbs.) 
the normal to iso ratio using rhodium as the catalyst may be below 1 or 
even as high as 100, depending on the ligand, ratio of ligand to rhodium, 
etc. When cobalt is used as the catalyst and is not modified by a ligand, 
the normal to iso ratio is below 3 at most. 
Another method for catalytic hydroformylation of olefins, using a 
conventional approach is set forth in U.S. Pat. No. 4,399,312 (Russell et 
al.), which issued on Aug. 16, 1983. The hydroformylation method discussed 
in the above-mentioned patent involves the reacting together, at elevated 
temperature and pressure, of an olefin, H.sub.2 and CO in the presence of 
a catalyst comprising a water soluble complex of a noble metal and an 
amphiphilic reactant in a reaction medium comprising an aqueous phase and 
an organic phase. The organic phase includes a highly reactive olefin, 
e.g., C.sub.3 -C.sub.20, and a solvent. The noble metal catalyst is 
typically Pt, Rh, Ru or Pd. The aqueous phase preferably contains a 
water-soluble phosphine in complex combination with a complex or catalytic 
precursor of the noble metal, e.g., sulfonated or carboxylated triaryl 
phosphines. The amphiphilic reagent is typically an anionic, nonionic or 
cationic surfactant or phase transfer agent such as a complex ammonium 
salt or a polyoxyethylene nonionic surfactant. The preferred ratio of 
aqueous phase to organic phase is 0.33:1 to 5:1, the ratio of H.sub.2 to 
CO is 1:1 to 5:1, the content of precious metal in the aqueous phase is 
100-500 ppm and the ratio of amphiphilic reagent to precious metal is up 
to 100:1 on a molar basis. It is preferable that the reaction be carried 
out at 300-10,000 kPa, especially 300-3,000 kPa and at a temperature in 
the range between about 40-150.degree. C. 
The present invention can best be described by referring to the attached 
drawings, wherein FIG. 1 is a schematic representation of a membrane 
separator 1 comprising a hydrophobic membrane 3. Membrane separator 1 is 
preferably used to separate a water soluble Group VIII noble metal-ligand 
complex catalyst from a crude reaction product of a noble metal-catalyzed 
hydroformylation reaction run in aqueous solution, in an aqueous emulsion 
or as an aqueous suspension. The crude reaction product typically includes 
an aqueous phase containing a water soluble Group VIII noble metal-ligand 
complex catalyst, and an organic phase containing unreacted olefin feed 
and an organic hydroformylation reaction product. Separation occurs by 
contacting the crude reaction product with hydrophobic membrane 3 which is 
capable of allowing a substantial portion of the unreacted olefin feed and 
organic hydroformylation reaction product to pass therethrough while 
retaining a substantial portion of the water soluble Group VIII noble 
metal-ligand complex catalyst. The unreacted olefin feed and organic 
hydroformylation reaction product which pass through hydrophobic membrane 
3 as permeate are then removed from membrane separator 1 for further 
downstream treatment. The retentate which comprises water soluble Group 
VIII noble metal-ligand complex catalyst and some of the organic phase 
constituents is recycled to the hydroformylation reactor. 
The organic hydroformylation reaction product and unreacted olefin feed are 
permeated, either by perstraction or pervaporation, through hydrophobic 
membrane 3 which retains the water-soluble catalyst quantitatively. 
The preferred water soluble ligand is one compound selected from the group 
consisting of: Na-p-(diphenylphosphino)benzoate, 
Na-m-(diphenylphosphino)benzenesulfonate, tri-(sodium 
m-sulfophenyl)-phosphine, and Na-p-diphenylphosphino benzene sulfonic 
acid. And the preferred water soluble noble metal catalyst is rhodium. The 
noble metal-catalyzed hydroformylation reaction according to the present 
invention preferably involves the reacting of an olefin with hydrogen and 
carbon monoxide (synthesis gas) in the presence of a water soluble Group 
VIII noble metal-ligand complex catalyst, at a temperature in the range 
between about 80 to 125.degree. C. to produce an aldehyde having a normal 
to iso ratio in the range of between about 0.5:1 to about 80:1. 
Optionally, a surfactant may be added to the noble metal-catalyzed 
hydroformylation reaction. The surfactant is preferably one compound 
selected from the group consisting of cetyltrimethyla-mmonium bromide, 
sodium laurate, sodium stearate, linear dodecylbenzene sulfonate (sodium 
salt), and p-toluenesulfonic acid (sodium salt). 
Hydrophobic membrane 3 is preferably selected from the group consisting of: 
a high density polyethylene crosslinked membrane, a natural latex rubber 
membrane, a polyvinylidene difluoride membrane, a 
polychlorotrifluoroethylene membrane, a polytetrafluoroethylene membrane, 
a bromobutyl rubber crosslinked with hexamethylene diamine, and a 
copolymer of isobutylene and p-bromomethyl styrene crosslinked with 
hexamethylene diamine. 
The method for producing higher aldehydes and higher alcohols according to 
the present invention can best be described by referring to FIG. 2, 
wherein an olefin feedstock is hydroformylated with synthesis gas in the 
presence of a water soluble Group VIII noble metal-ligand complex catalyst 
in hydroformylation reactor loop comprising vessel 10, pump 16 and 
separator 18 to form a crude reaction product. The crude reaction product 
is typically comprised of an emulsion of the organic phase containing 
unreacted olefin feed and organic hydroformylation reaction product and an 
aqueous phase containing a water soluble Group VIII noble metal-ligand 
complex catalyst. This emulsion of the organic phase and aqueous phase is 
sent to membrane separator 18 by pumping means 16 for the purpose of 
removing the water soluble noble metal catalyst from the crude reaction 
product. Membrane separator 18 includes a hydrophobic membrane 20 which is 
capable of allowing a substantial portion of the hydroformylation reaction 
product and unreacted olefin feed to pass from reactant chamber 22 through 
membrane 20 and into sweep chamber 24, while retaining a substantial 
portion of the water soluble Group VIII noble metal-ligand complex 
catalyst within reactant chamber 22. The hydroformylation reaction product 
and the unreacted olefin feed which pass through membrane 20 are swept 
away by means of an organic sweep solvent which can be supplied via 
reactor vessel 26 and pumping means 28. 
Hydrophobic membrane 20 is substantially impermeable to water soluble Group 
VIII noble metal-ligand complex catalyst which are retained as retentate 
in reactant chamber 22 and thereafter recycled to reaction vessel 10 via 
pump means 23 for further reaction with the olefinic feedstock. Pump means 
23 is also capable of removing the permeate from sweep chamber 24 and 
thereafter sending the permeate for further downstream treatment. 
As shown in FIG. 3, the crude reaction product can optionally be separated 
into an aqueous layer and a organic layer before it is fed to membrane 
separator 18. This separation takes place in a settler or other 
conventional settling tank 30, Wherein organic layer 32 rises to the top 
and aqueous layer 34 settles to the bottom of settler 30. Aqueous layer 34 
is recycled to hydroformylation reactor vessel 10 and organic layer 32 is 
fed to membrane separator 18, wherein water soluble Group VIII noble 
metal-ligand complex catalyst are retained as retentate and unreacted 
olefin feed and organic hydroformylation reaction product pass through 
hydrophobic membrane 20 as permeate. The retentate is recycled to reactor 
vessel 10 to be again used in the hydroformylation process. 
EXAMPLES 1-2 
Using an analytical balance, 0.122 grams (2.74.times.10.sup.-4 moles) of 
rhodium acetate dimer containing 0.0551 grams (5.35.times.10.sup.-4 g 
atom) of rhodium was weighed into a 1 dram vial and transferred to the 
nitrogen dry box for catalyst preparation. Next 1.47 grams 
(5.34.times.10.sup.-3 moles) of diphenylphosphinobenzoic acid and 70 grams 
of 1N NaHCO.sub.3 were weighed into a 125 ml Erlenmeyer flask and heated 
to approximately 75.degree. C. with magnetic stirring to effect solution 
of the diphenylphosphinobenzoic acid. The resulting clear and colorless 
liquid was cooled to room temperature and the rhodium acetate dimer was 
added. A cloudy orange liquid with orange solids resulted. Finally, 2.0 
grams (5.49.times.10.sup.-3 moles) of cetyltrimethylammonium bromide 
(Example 1) was added. A cloudy orange emulsion resulted with fine orange 
solids. In Example 2, 2.0 grams (5.49.times.10.sup.-3 moles) of lauric 
acid was used in place of the cetyltrimethylammonium bromide. 
Into a 500 ml Erlenmeyer flask equipped with a magnetic stirring bar were 
weighed 179.0 grams (1.28 moles) of decene-1 and 10.6 grams (0.047 mole) 
of hexadecane. The clear and colorless liquid was deaerated with nitrogen 
for fifteen minutes with stirring. 
The membrane reactor was assembled and the membrane to be tested, 9 cm in 
diameter, sandwiched by two pieces of Goretex.RTM. (0.2 micron 
Teflon.RTM.) also 9 cm in diameter, was mounted in place and the membrane 
reactor unit was purged with nitrogen. Next the system was evacuated with 
a vacuum. The catalyst solution was drawn with vacuum to the catalyst side 
of the membrane and then the decene/hexadecane solution was added to the 
same side. Finally, the hexene/hexadecane/squalane solution was drawn with 
vacuum into the sweep side of the unit to act as the perstracting solvent. 
The hexadecane was employed as an internal standard. 
Both the catalyst solution and sweep solution were circulated at a rate of 
about 1,000 cc/minute. The contents of the membrane reactor unit were 
pressurized to 6.9.times.10.sup.5 N/m.sup.2 (100 psi) pressure with a 
50/50 mixture of hydrogen/carbon monoxide, then heated to about 80.degree. 
C. in thirty minutes. At 77.degree. C., the hydrogen/carbon monoxide 
pressure was increased to 1.03.times.10.sup.6 N/m.sup.2 (150 psi) 
operating pressure and the supply of hydrogen/carbon monoxide kept 
constant throughout the run. 
At the conclusion of the run, the clear and colorless liquid on the sweep 
side was analyzed for rhodium. The catalyst solution on standing separated 
into two phases, i.e., clear and colorless upper phase and a yellow-brown 
lower aqueous phase. The results of the two examples were as follows. 
Example 1 used a high density polyethylene membrane crosslinked by 
radiation (1.05 mils) wherein only 0.086 ppm of rhodium were detected in 
the permeate, i.e., 0.02%. In Example 2 a natural latex rubber membrane 
demonstrated less than 0.011 ppm rhodium in the permeate, i.e., 0.002%. 
EXAMPLE 3 
A membrane reactor was assembled with a 9 cm HALARG (i.e., a 
chlorotrifluoroethylene and ethylene copolymer) membrane sandwiched 
between two pieces of Goretex.RTM. (0.2 micron Teflon.RTM.) also 9 cm in 
diameter. The HALAR.RTM. membrane was mounted in place and the membrane 
reactor was purged with nitrogen. Next the system was evacuated with a 
vacuum. The catalyst solution was drawn with vacuum to the catalyst side 
of the membrane and then a decene/hexadecane solution was added to the 
same side. Finally, the hexene/hexadecane/squalane solution was drawn with 
vacuum into the sweep side of the unit. 
Both the catalyst solution and sweep solution were circulated at a rate of 
about 1,000 cc/minute. The contents of the membrane reactor unit were 
pressurized to 6.9.times.10.sup.5 N/m.sup.2 (100 psi) pressure with a 
50/50 mixture of hydrogen/carbon monoxide then heated to about 80.degree. 
C. for thirty minutes. At 77.degree. C., the hydrogen/carbon monoxide 
pressure was increased to 1.03.times.10.sup.6 N/m.sup.2 (150 psi) 
operating pressure and the supply of hydrogen/carbon monoxide kept 
constant throughout the run. 
At the conclusion of the run, the clear and colorless liquid on the sweep 
side was analyzed for rhodium. The catalyst solution on standing separated 
into two phases, i.e., a clear and colorless upper phase and a 
yellow-brown lower aqueous phase. The HALAR.RTM. membrane permitted only 
0.13 ppm of rhodium to permeate therethrough, i.e., less than 0.03%. 
It is anticipated that halogenated polymers, as a class, will be 
advantageous in this type of membrane reactor application. It also appears 
that hydroformylation reaction products which included a water soluble 
ligand, such as p-diphenylphosphinobenzoic acid, exhibit satisfactory 
normal to iso ratios based upon aldehydes, as well as satisfactory 
turnover number. 
EXAMPLES 4-10 
In the following examples the present inventors attempted to select a 
polymer from which a membrane could be prepared which would retain at 
least 99% of the water-soluble ligated rhodium complex used in the oxo 
conversion of olefin to aldehyde and at the same time allow high 
permeation rates of the aldehyde product. Furthermore, the present 
inventors attempted to demonstrate that such a membrane system would 
perform successfully with a variety of water-soluble ligands and 
surfactant combinations. Among the ligands utilized were the sodium salts 
of p-diphenylphosphino benzoic acid, p-diphenylphosphino sulfonic acid and 
tri-Na-m-sulfophenyl phosphine. The present inventors prepared membranes 
from bromobutyl rubber, and a copolymer of isobutylene and p-bromomethyl 
styrene since they are stable hydrocarbons, hydrophobic, and easily 
crosslinked. 
The present inventors determined that the degree of crosslinking was 
critical to the membrane's stability, rate of aldehyde permeation and 
rhodium retention. To optimize the degree of crosslinking the present 
inventors crosslinked the polymers varying the important parameters of 
temperature, time and crosslinking agent stoichiometry and then conducted 
swelling experiments to determine the relative degree of crosslinking. For 
example, the polymers are soluble in toluene before crosslinking and 
insoluble after crosslinking. once the best conditions for crosslinking 
were chosen based on the swelling data, a membrane and backing was tested 
for long term solvent stability by extraction with boiling cyclohexane in 
a Soxhlet extractor. The ideal membrane should have zero weight loss. If 
the membrane had a low solubility in the extraction test it was then 
tested in the membrane separator unit for aldehyde permeation and rhodium 
retention. 
A typical swelling test was conducted wherein the copolymer of isobutylene 
and p-bromomethyl styrene was first dissolved in toluene. Next various 
proportions of the crosslinking agent 1,6-hexane diamine was added and the 
mixture thoroughly mixed. The resultant viscous polymer solutions were 
poured into small widemouth jars and the samples were allowed to weather 
overnight. After weathering, the polymer samples were heated for various 
times at various temperatures. Finally, toluene was added and the 
crosslinked polymers were allowed to soak overnight at room temperature. 
The polymer was then removed from the toluene, patted dry with a paper 
towel and weighed to determine the weight gain. 
The membrane for evaluation in the membrane separator was prepared as 
follows. Into a 250 ml wide mouth jar equipped with a magnetic stirring 
bar was added 34.17 grams of the copolymer of isobutylene and 
p-bromomethyl styrene together with 104.13 grams of toluene. The 25% 
solution was stirred magnetically until all the polymer dissolved. After 
stirring two days, with occasional warming to about 50.degree. C., the 
polymer dissolved completely resulting in a clear yellow viscous liquid. 
An aliquot or 49.2 grams of the 25% polymer solution containing 12.3 grams 
of polymer which contained 0.02704 grams or 2.2% bromine was transferred 
to a 100 ml wide mouth jar. To this solution was added 0.49 grams of 
1,6-hexane diamine dissolved in about 0.6 grams of toluene. After thorough 
hand mixing, the clear viscous yellow liquid was transferred to a 
centrifuge tube and centrifuged for 20 minutes at 10,000 rpm. Next three 
membranes were cast on Teflon@sheets 9x9 inches about 2.2 mil thickness, 
0.2 micron pore size and 80% porosity. The cast membranes were allowed to 
weather overnight in a nitrogen purge box then heated for 2 hours at 
1250C. The cast membranes were examined for weight loss by extraction with 
refluxing cyclohexane. 
Seven comparative runs were conducted to demonstrate the utility of two 
different ligands, two different membranes and three different 
surfactants. These runs were conducted in an aqueous emulsion using 
water-soluble phosphine ligands as described in Table I below. The 
decene-1 was hydroformylated in a stirred autoclave before transfer to the 
membrane separator. The data is summarized in Table 1 below. 
TABLE 1 
______________________________________ 
Thick- 
ness Run 
Run Mem- in P/Rh Time 
No. brane Microns Ligand Ratio Surfactant 
Hours 
______________________________________ 
1 A 48.5 DPPBA 27 Na Laurate 
69 
2 A 43.9 DPPBA 9 Na Laurate 
89 
3 A 29.6 DPPBA 18 LABS 93 
4 A 65.5 DPPBA 9 SPTSA 57 
5 A 25.7 TPPTS 21 None 79 
6 B 25 DPPBA 18 Na Laurate 
88 
7 B 55.7 DPPBA 18 Na Laurate 
93 
______________________________________ 
Notes: 
(1) Membrane A is a copolymer of isobutylene and pbromomethyl styrene 
crosslinked with hexamethylene diamine. 
(2) Membrane B is bromobutyl rubber crosslinked with hexamethylene 
diamine. 
(3) DPPBA is diphenylphosphinobenzoic acid, sodium salt. 
(4) TPPTS is triNa-m-sulfophenyl phosphine. 
(5) LABS is linear dodecylbenzene sulfonate, sodium salt. 
(6) SPTSA is ptoluenesulfonic acid, sodium salt. 
Permeation 
Permeation 
Run ppm Rh % Rh Rate Rate 
No. Sweep Lost* kg/m.sup.2 /day 
kg/m.sup.2 /.mu./day 
______________________________________ 
1 0.23 0.5 18 863 
2 0.25 0.4 11 485 
3 0.39 1.0 11 328 
4 0.14 0.6 9 590 
5 0.53 0.3 27 696 
6 0.27 0.7 12 312 
7 0.21 0.6 11 625 
______________________________________ 
*Percent of rhodium lost is calculated as follows: 100 .times. (grams of 
aldehyde produced/grams of aldehyde permeated) .times. (grams of rhodium 
permeated/grams of rhodium fed). 
EXAMPLE 11 
2 grams of lauric acid, as surfactant, were added to an aqueous solution 
which included sodium p-diphenyl phosphino benzoate (i.e., Ph.sub.2 
p(P--C.sub.6 H.sub.4 COONa)), dissolved at approximately 70.degree. C. 
with stirring under nitrogen in 70 grams of 1N NaHCO.sub.3 solution. The 
resulting clear solution was then introduced through a Hoke bomb to a 1 
liter autoclave. To this solution, a mixture which comprised 179.23 grams 
of 1-decene, 9.93 grams of hexadecane as an internal standard, 1.24E-01 
grams of rhodium acetate dimer (i.e., RhII.sub.2 (OOCCH.sub.3).sub.4) and 
10 grams of i-PrOH as co-solvent were introduced through the Hoke bomb 
under a carbon monoxide/hydrogen pressure. 
The autoclave was pressurized with a mixture of CO/H.sub.2 in a ratio of 
1:1 and at a pressure of 6.9.times.10.sup.5 N/m.sup.2 (100 psi) at room 
temperature. The contents were then heated to 80.degree. C. while the 
pressure was maintained at 1.03.times.10.sup.6 N/m.sup.2 (150 psi). The 
reaction was monitored by periodic gas chromatographic analysis of the 
organic layer. At the conclusion of the run the mixture was cooled and 
removed from the autoclave. After settling, the layers were separated and 
the substantially organic layer transferred to the membrane separator. 
The membrane formed by the crosslinking of isobutylene and p-bromomethyl 
styrene with hexamethylene diamine and casting on Teflon.RTM. was mounted 
in the membrane reactor unit between two 100 mesh stainless steel screens. 
The polymer thickness was 48.5 microns, with two 53.3 micron sheets of 
Teflon.RTM. on the outer surface. To the evacuated catalyst side of the 
membrane reactor unit was added the reactor product. To the evacuated 
sweep side of the membrane reactor unit was added the following deaerated 
solution: 306.0 grams (3.64 mole) hexene-1 and 23.0 grams of hexadecane. A 
mixture of hydrogen/carbon monoxide gas (51/49) was pressured to the 
reactor unit to approximately 7.6.times.10.sup.5 N/m.sup.2 (110 psi) and 
the contents were heated at 80-85.degree. C. for 69 hours. The catalyst 
side and sweep side were circulated at 400cc/minute during this heating 
period. Samples were withdrawn from both sides of the membrane separator 
periodically and the compositions analyzed by gas chromatography. 
The results are displayed in FIG. 4 which is typical and given for 
illustrative purposes only. At the conclusion of the run, the sweep side 
of the reactor was calculated to contain 52.17 grams of undecyl aldehyde 
which represent an overall permeation rate of the aldehyde of 17.8 
kg/m.sup.2 /day or 863 kg/.mu./m.sup.2 /day. The sweep side also contained 
3.92 grams of heptyl aldehydes formed by the permeation of hexene-1 to the 
catalyst side of the separator, hydroformylation and then returned as the 
aldehyde. The final hexene-1 and undecyl aldehyde mixture on the sweep 
side was analyzed for rhodium and found to contain 0.23 ppm indicating 
that about 99.5% of the rhodium would be retained if all the aldehyde had 
permeated. 
These results clearly show that the concept of using a hydrophobic membrane 
to contain a water-soluble catalyst is applicable so long as the membrane 
is both thermally stable and insoluble in the reaction media and the water 
soluble catalyst remains in a ligated state in the aqueous solution. The 
phenomenon was demonstrated with a carboxylate ligand and a sulfonate 
ligand, and with carboxylate and sulfonate surfactants. Good results were 
obtained independent of permeation rate of the aldehyde through the 
membrane. 
While we have shown and described several embodiments in accordance with 
our invention, it is to be clearly understood that the same are 
susceptible to numerous changes apparent to one skilled in the art. 
Therefore, we do not wish to be limited to the details shown and described 
but intend to show all changes and modifications which come within the 
scope of the appended claims.