CA1064968A - Alcohol separation - Google Patents

Abstract

ALCOHOL SEPARATION

ABSTRACT OF THE DISCLOSURE
The process involves the separation of product form a liquid homogeneous mixture obtained from the reaction of oxides of carbon (e.g. CO) and H2 in a solvent solution containing a rhodium carbonyl complex catalyst. The solution stability of the catalyst is enhanced by volatilizing the product from the mixture while simultaneously maintaining the mixture in contact with CO gas.

S P E C I F I C A T I O N

1.

Description

g6~

This invention i~ concerned with the recovery of product from a homogeneous mixture containing a rhodium carbonyl complex catalyst. More particularly, this invention relates to the separation of the alcohol products of the reaction between oxides of carbon and hydrogen in a homogeneous liquid-phase containing a -rhodium carbonyl complex.
There are described in Belgium Patent No.
793 ,086 , published June 20, 1973 and U.S. patent application No. 3,957,857, filed April 18, 1974 processes involving the high pressure reaction of oxides of carbon and hydrogen in the presence of a rhodium carbonyl eomplex catalyst. It has been pointed out in U.S. patent No. 3,9S7,857 that a preferred rhodium carbonyl complex catalyst is a rhodium carbonyl cluster. The nature of that catalyst under the conditions of the reaction or as it is provided to the reaction can be characterized by its lnfrared spectrum. However, such catalysts requently take another structure at temperatures and pressures lower than those used in the reaction.
In a pre~erred embodiment of those processes7 the reaction is conducted as a homogeneous liquid phase, which means that the catalyst and the alcohol products formed from the reaction are in a solution.
The solution typically requires the presence of a solvent mainly to keep the catalyst in solution before and after the reaction. Since the main and the most valuable products of those processes are high boiling alkane polyol~ such , 2 , ~6496~
as ethylene glycol, ~lycerine and 1~2-propylene glycol, and ~he secondary, and less valuable products are alkanols such as meth~nol, ethanol, etc., ~ather severe changes are required fr~m the conditions of the reaction to those employed in the separation of product. And, since the most desired process is a continuous one, it is necessary to be able to recycle the catalyst to the reaction after the product has been removed.
However, rhodium carbonyl complexes vary in structure based e.g., upon the temperature, solvent, ligand, counter ion, and carbon monoxide and hydrogen pressure employed, such that a complex which may be extremely stable in a solutlon at one temperature could precipita~e out of the solution at another temperature. In the case of large scale processes, catalyst losses are not usually tolerated. In the case of the processes of the above-mentioned U.S. patents, rhodium losses in the order of, e.g., about O~lZ by weight on a per pass basis would be sufficient to make the process uneconomical. On the open market, rhodium metal is priced in the neighborhood of about 715 U.S. dollars per troy ounce. ~hus, the commercialization of these processes requires avoidance of a loss of ~n ~mount of rhodium metal which causes the cost of the products produced to be greater than that of the same products produced by other c~mpetitive processes.

~. ....

~ ~ 6 ~9~i~
There is described herein a process for the re-covery of the alcohol products produced by these rhodium catalyzed reactions which reduces catalyst instability durlng that phase of a con~inuous proces~. By the terms "instsbillty" and "unstablei', when referring to the catalys~, it is mean~ t~at it is reduced to a condition where it becomes, or ~s, insoluble in the solution from which the produc~ is being recovered.
The process of this invention involves the separatLon of product from a liquid homogeneous mixture obtained from the reaction of oxides of carbon and hydrogen in a solvent solution containing a rhod~um carbonyl complex cataly~t in a manner which minimlzes catalyst in-stability. Thi8 i8 accompli~hed by the s~mple expedient of contacting the mixture with carbon monoxide gas while simultaneou~ly volat~lizing product from ~he mixture.
m e term "contacting", as used above, means a physical touching of the mixture and carbo~ monox~de gas as illustrated by pro~iding the ~a~ a~ the sur~ace of the mixture, or bubbllng the ga~ through the mi~ture, and the like.
The typ~cal solution (i.e., liquid homogeneous mixture~ which i8 to be treated in accordance with this invention will contain the products of the react~on, such as ethylene glycol J glycerine, propylene glycol, methanol, ethanol, propanol, ethylene glycol monoformste, methyl formate, ethyl formate, and the like, the cataly8t in the form o a rhodium carbonyl complex and a ~olvent for the catalyst which iB nn~tually compatlble wlth the products of the react~on. T~ae amount of p~oduct ~n the solution can vary grea~y, from about 1 to abou~ 75 weigh~ percent of the solution. The solven~ c~n be pr sent in a broad range, such as from about 25 to abou'c 99 weight percent of the solutlonO The catalyst concen~ration can ~rary greatly, from a~out 1 x 10 6 weight perCeTIt, or even le~, to about 30 we~ght percent, based on its rhodium metal content.
10 However, the c~mposition of the liguid homogeneous mlxture being treated according to thi~ inventi~ i8 not narrowly cr~tic~l. All that is required i~ any amount o reaction product to be recovered, and any amoun~ o e~ rhodium carbonyl complex ~olvated by a sol~ent.
The rhodium carbonyl comple~c preseslt ~n the ~olutiorl toes not ha~e to have the ~tructure of the rhodium car~ l complex which caaly~ed the reaction be~ween the CO ant H2. In those ca~e~ ~ere the rho~ium carb~yl compl~x acting a~ ~ c~a~ haB the ~truct:ure:

2~ ~

., ._ . . ,, .. __ , ... . . .. .

r -2..
L~bl2 ~C~) 3~J

S~

~i4968 the rhodium carbonyl complex which exists in the homo-geneous mixture mny be ~n anion of the structure:

~c~

, .. . _ ., . . . ._ .. _ Rh6(CO) lS, ' ' or it may be the anion of lower rhodium con~aining com-pounds, from monorhodium carbonyl and up. All that is required.for the process of this in~ention is tha~ the rhodium compound contain -CO bonded to rhodium and be in solution`.
me solubilization of the rhodium carbonyl complex is typically dependent upon the solvent used to effect the h~mogeneous mixture. m~ desired solvent is any liquid material which dissolves or keeps in 801u~ion the compo~ent~ of the homogeneous mixture ~aken ~r~m the reactor. It must be solution compatible with the reaction products and the rhodium carbonyl complex.
Illustrative solvent~ which are generally suit-able in maki~g the h~mogeneo~s mlxture, include, for example~ ~aturated and aromatic hydrocarbons, e.g., hexane? octane, dodecane, naphtha, decalin, tetrahydro-naph~halene$ kerosene, mineral oll, cyclohexane, cyclo- , hep~ane, alkylcycloalk~ne, benzene, toluene, xylene, 6.

naphthalen, alkylnaphthalene, etc.; ethers such as tetra-hydrofuran, tetrahydropyran, diethyl ether, l,2-dimethoxy-benzene, 1,2-ethoxybenzene~ ~he mono- and dialkyl ~thers of ethylene glyco}, of propylene glycol, o~ butylene glycol, of diethylene glycol, of dipropylene glycol~ of triethylene glycol, of tetraethylene glycol, of dibutylene glycol,-of oxyethyleneoxypropylene glycol e~c.; carboxylic ac~ds such as acetic acid, propionic acid, butyric acid, caproic acid, stearic a~id, benzoic acid, cyclohexanecarboxylic acld, etc.; alkanols such as methanol, ethanol, propanol, isobutanol, 2-ethylhexanol, etc.; ketones such as acetone, methyl ethyl ketone, cyclohexanone, cyclopentanone, etc.;
esters such as methyl acetate, ethyl acet~te, propyl acetate, butyl acetate, methyl propionate, ethyl butyrate methyl laurate, etc.; water ; anhydride~ such as phthalic anhydride, acetic anhydride etc.; gamma-butyrolactone, delta-~alerolac~one, and others. Tetrahydrofuran, dioxane7 and the mono and dialkyl ether~ of triethylene and tetraethylene glyco~ gEmma-butyrolactone and delta-v~lerolactone are gener~lly preerred solvents.
Because ~he rhodium carbonyl complexes are typ~cally ionic, they can be associa~ed with a counter~ion. The counter-ion may be rhodium per se, hydrogenj ammonia, any monovalent or polyvalent metal, a~d a broad range of organic compounds, such as those c~aracterized hereinafter as ligands.

' ~ ~ ~ 49 ~3 The mono~alent or polyvalent metal counter~ion may include lithi~, sodium, potassiumj rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium, radium, ~candium, yttrium, the rare earth metals (especially, e.g., cerium, praseodymium, and europium), titanium, zirconium~ hafnium, manganese, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, pallad~um~ platinum, copper, silver, gold, boron, aluminum, gallium, indium and thallium.
The organic counter-ions may result from "c~mplexing" organic compounds with the ~hodium carbonyl ions or by ionically associating with them.
The term "complex" means a coordination compound ormed by the union o~ one or more electronically rich molecules or atoms capable of independent existence with one or more electronically poor molecules or atoms, each of which iq also capable of independent - existence. The rhodiu~ carbonyl complexes may be associations of organic ligands wi~h rhodlum carbonyl solution~. The complex may. al90 be formed fram the reaction of ~0 and H2 with the rhodium carbo~yl solution.
Organic llgands wh~ch ~re ~uitable in the practice of the lnvention contain at least one nitrogen atcm (hereinafter called Lewis base ni~rogen a~am) and/or at least one oxygen atom (hereafter called Lewis base oxygen a~om), said at~ms posæessing a pair of electrons ~' .

1~6~L96~3 available for the formation of coordinate bonds with rhodium. Desirably, the organic ligand contains at least two Lewis base nitrogen at~ms, or at least two Lewis base oxygen atoms, or at lea~t one Lewis base nitrogen a~om plus at least one Lewis ba~e ~xygen atom, said atoms possessing a pair of elec~rons available for the formh-tions of coordinate bonds with rhodium, and said organic lig~nd forming w~th r~odium per se a chelate structure.
In suitable embod~ments the organic ligands co~tain from 2 and upwsrds to 4 Lewis base atoms~ preferably from 2 to

3 such atoms, and more preferably 2 Lewis base atoms.
These organi~ ligands are said to be multidentate or poly-dentate~ that is to say, such ligands are bidentate, tridentate, or quadriden~ate, depending on whether 2, 3 or 4 Lewis base atoms are involved in the formations of complexed ~tructures with rhodium.
Organic ligands which c~n~ain at least one Lewis base nitrogen atom will ofte~times here~naftar be re-ferred to as "organic nltrogen ligand~ hose ligands which contain at least one Lewis base oxygen at~m will otentimes be re~erred to as "organic oxygen ligands";
and those;which contain at lea~t one Lew~s base nitrogen atom plus at least one ~ewis ba~e oxygen atam will oftentimes be re~erred to as "organic aza~oxa ligands".
Suitable organic nitrogen ligands most generally contain carbon, hydrogen, and nitrogen at~ms. Suitable .

96~0 69~9~

organic oxygen ligands most generally contain carbon, hydro-gen, and oxygen atoms. Suitable organic aza-oxa ligands most generally contain carbon, hydrogen, oxygen, and ni~xogen atoms. The carbon a~o~s can be acyclic and/or cyclic such as àliphatic, cycloaliphatic, arom~tic (including fused and bridg d~ carbon atoms, and the like. Preferably, the orgsnic ligands contain fram 2 to 20 carbon atoms. The ni~rogen atoms can be in the form of imino (~N=), amino (~N-), nitrilo ~N-), etc. Desirably, ~he Lewis base 10 nitrogen atoms are in the form of imino nitrogen and/or amino nitrogen The oxygen atoms can be i~ the form of groups such as hydroxyl (aliphatic or phenolic), carboxyl O O
" i- "
(-COH), carbonyloxy (-CO-), oxy (-O-), carbonyl (-C-), etc., all of said groups containing Lewis base oxygen atom~. In ~his respect, it i~ the "hydroxyl" oxygen in O O
Il ~
the -COH group and the "oxy" oxygen in the ~CO- group that are the Lewis b~se atoms. The orRanic ligands may also con~ain other at~ms and/or grOUp8 9uch as aLkyl, cyclo-alkyl, aryl, c~loro, thiaalkyl, trialkyl~ilyl, and the like.
Ill~strative organic nitrogen ligand~ include ~or instance, N,N,N',N',~tetramethylethylenediamine, N,N,N',N'-tetraethyle~hylenediamine, N,N,N',N'-tetra-propylethylenediamine, N,N,N',N'-tetramethylmethylenediamine, 10.

~ 5)64968 N,N,N',N'-tetraethylmethylenedis~ine, ~,~,N',N'-tetraiso-butylmethylenediamine, piperazine, N-methylpiperazine, N-ethylpiperazine, 2-methyl-~-methylpiperazine, 2,2'-dipyridyl, methy1-substituted 2p2'-dipyridyl, ethyl-substi~uted 2,2'-dipyridyl, 1,4-diazabicycloE2.2.2]octa~e, methyl-substituted 1,4-diszabicyclo~2.~.2]octane 7 purine, 2-amino-pyridine, 2-(dime~hylamine~ pyridine, 1,10-phenanthroline, me~hyl-substituted 1,10-phenanthroline, 2 -(dimethylamino)~6-methoxy-quinoline, 7-chloro-1,10-phenanthroline, 4- triethylsilyl-2,2'-dipyridyl, 5-~thiapentyl~-1,10-phenanthroline, and the like.
Illustrative organic oxygen ligands include by way o illustration~, glycolic acid, methoxyacetic acid, ethoxyacetic acid, tiglycolic acid, thiodiglycolic acid, diether ether, tetrahydrofuran, dioxane, tetrahydropyran, pyrocatechol, citric acid, 2-methoxy ethanol, 2-ethoxy-ethanol, 2-n-propoxyethanol, 2-n-butylethnnol~ 1,2,3-tri-hydroxybenzene, 1,2,4-trihydroxybenzene, 2,3-dihydroxy-naphthalene, cyclohexane-1l2-diol, oxetane, 1,2-dimethoxy-benzene, 1,2-tiethoxybenzene, methyl acetate, ethanol, 1,2-dimethoxyethane, 1,2-die~hoxy~thane, 1,2-di-n-propoxy-ethane, l,2-di-n-butoxyethane, pantane-2,4-d~one, hexane-2,4-dione, heptane~3,5-dione, octane-2,4-dione, l~phenyl-butane-1,3-dioDe, 3-methylpentane-2,4-dione; the mono- and dialkyl ethers of propylene glycol, of diethylene glycol of dipropylene glycol; and the like.
Illustrative organic aza-oxa ligands include, for example, ethanol~m~ne, dieth~nolamine, i~opropanolamine, 11.

106491~
di-n-propanolamine,~N,N-dimethylglycine, N,N-diethylglycine, iminodiacetic acid, N-methyliminodiacetic acid, N-methyl-diethanolamine, 2-hydroxypyridine, methyl-substituted 2-hydroxypyridine, picolinic acid9 methyl-substituted picolinic acid, nitrilotriacetic acid, 2,5-dicarboxypiperazine, N-(2-hydroxyethyl) ~minodiacetic acid, ethylenediaminete~raacetic acid, 2,6-dicarboxypyridine, 8-hydroxyquinoline, 2-carboxy-quinoline, cyclo~exane-1,2-diamine-N,N~N',N'-te~raacetic acid, the tetramethyl ester of ethylenediaminetetraacetic acid, and the like.
Other organic co~nter-~ons are formed by ionic asso-ciation ~ith the rhodium carbonyl cluster ions. They are from organic compounds which possess Lewis base nitrogen atams and typically are c~mposed of carbon, hydrogen and nitrogen. Illustrative of such compound~ are, e.~., piperidine, 2-methylpiperidine, 3-methylpiperidine, pyridine, 2-methylpyridine, 4-ethylpiperidine, triethyl-amine, benzyltr~methyl ammonlum acetate and orma~e~ tri-n-butylamine, dibutylamine, methylamine, dodecylamine, morpholine, aniline, benzylamine, octadecylamine, naphthylamine, cyclohexylamine, and the like.
me manner of 8eparating the reaction product(s) from the h~mogeneous mixture may include distillation a~d gas stripping. The separation may be effected at subatmospheric, atmospheric and superatmospheric pressure conditions and the te~per~ture at which ~eparation i3 effected is lower than tha~ which causes the available CO

~ ~ 6 49 6 ~

to react with product~ ~olvent and/or available hydrogen.
The pres~ures used may range from about 0.001 to about 1000 atmospheres of pre~ure. The temperature may range from a~out 50C. to about 300C., more desirably from about 75C.
to about 250C " and ~os~ desirably from about 100C. to about 200C.
: Thi~ inYention inc1udes the presence of C0 gas in con~act wi~h the homogeneous mix~ure during separation of re~ction product. The carbon monoxide gas may be added ~o the a~moephere above 8 liquid body or ~llm of the homogeneous mixture undergoing product separation by distillation (e.g., by conventional distillation or by thin-fllm evaporation). The umount o CO gas added to the atmosphere over the liquid body or ilm should be suf~icient to reduce the amount of rhodium lo~t from the mixture w~en C0 is not used. In the case of t~in film evaporation, the CO gas can be ~upplied a~ impringing str~am on the ~ilm ~o - as to act as a ~ripping gas as well. In addit~on, or alternatively, the C0 ~as can be bubbled through ~he liqui~
body ~o increase the rate at which C0 is dissolved therein.
By increasing ~he amount of the C0 ga~ and/or i~s stream velocity, the gas can be u~ed to strip pro~uc~ rom the mixture to increase the rate o~ reco~ery of the product over di~tillation alone or to mainta~n the rate of recovery at lower temperatures and/or higher pre8sure8. The C0 may be mixed with hydrogen gas without adversely afEec~in~ the stabilization of the rhodium containing cataly~t.
13.

~6496~

EX~MPLE I
The procedure in this Example, the runs of which are characterized in Table I below, in~ol~es charglng the ~olutions to be treated to a 100 ml.
3-necked reaction-flask equipped with a water condenser, a therm~meter and a rubber ~yr~nge cap Qr sampling.
me condenser was connec~ed ~o a manometer a~d vacuum pump a~d the prescure in the flask was ad,~usted with a nitrogen bleed into the flask when necessary. The ~lask was 10 equipped with a gas delivery sparge to a nozzle, all o which open to the bottom of the flask BO as to be covered by any sQlution which is added to the flask. me gases added were carbon monoxide or nitrogen, as indicated in Table I below, and they were fed at a rate sufficien~c to provide constant bubbli~g of the gases. ~hrough the liquid in which the sparge was i~ne~sed. mere was no efort to deterrnine carbon morto~clde and ni~rogen sparge rate~ in these runs. me flask waa i~nersed in a con-stant t~mpera~ure bath ~e~ a~ 150C. and the solutiorl 20 in the flask was sampled at intervsls and analyzed by atomic absorption spectro~copy.

1~, ~1[164968 ;~ o C~ o o ~ oo ~ , ~ _ h ' g ' ~
a) ~ ~ o 3 ~
O~
O ~ _I ~1 ~ o I ~D O ~1 ¢
a) ~ ~ O Oo C~ ,o ~o ~ o u~ q ~u ,S: ~ ~ ~`I OOD ~ I ~ V: ~ O
~ o ~ ~
~ . ~ ~
# ~ Cl ' ~ C.) ~ CO
~:: C al O
~i-3 o o ~3o o o ~; o -~3 ~ o co ~ ~ o u~
al ."
.~ ~ ~ ~ o o a~ ~ ~ O
o '~ ~ ~ ~ ~ . o o o o o o o o ,~ ~ ~ ~ o ,~ oo . oO O Oc~
~3 o ~ ~ ~ ~ ~ ~ ~ ~ o ~Q
~1 ,Q '4~
~ d n ~ ~ ~ o u ,c~ I~
c~ t~ : ~ ~ ~ . ;
~ . O .. . . , . ,~
ul ~ ~ ~ a ~ O O c~

O '~
P d) O C: ' ~ 0,~
c~ ~o o o o c) ~ 8 ~

. ~ ~ ~o~ tn 9 ~ ~ o ,~ o~
. ~ -~ ~d .n , .

' 1C~6~96!3 E~MPLE II
, In the runs set forth in Table II of this Exampie, ~he ca~alyst ~olution i8 added to a 100 ml.
rocker~bomb equipped with a gla~s liner. The bomb wa~ flu~hed wi~h the d2s~red ga~ mixture, either carbon mo~oxide wi~h or without hydrogen, or nitrogen and pressurized to the de~red pres~ure a~ indicated ~n Table II. me bomb wa8 thereafter ~lowly heated ~ver a period of ~bout two hours to the react~on temper~ture set orth in Table II and then ventet to maintain the de8ired pre~ure in the bomb. The bomb wa~ constantly rocked under the ~peci~ied conditions Po~ 24 hours, th~n cooled ~nd ~he c~ntent8 were ~nalyzed or rhodium. In Table II below, the control runs u~ed nitrogen rather than carbon monoxide and when a c~rbon monoxlde run iB iDdicated in Table II at les~
than 10.0% ~arbon monoxide the difference i8 made up by ~ddition of hydrogen gns. me ~hodium v~lue~ ~xpre3~ed in Table II were tho8e analyz~d a~ter the 24 hours period of each run.
It can be ~een ~rom T~ble II ~hat when a h~gher preBsure i8 employed, ~here i~ an overall average incre~se of 1032 parts per million (ppm) by weight of rhodium found over that o~tained at a~mospheric pre~8u~e. 0~ the other hand, when the temperature ~8 increas0d, there i~ an overall ~verage 10~8 of 2064 parts per ~6~9~;~

million of weight of rhodlum from that obtained at the lower temperature~ There appears to be no difference ~hoq~, of dny significance, in the re~ult~ of ~he run~
of Table II where 43% carborl monoxide i~ used instead of 100% carborl monoxide. T~e ave~age difference was only an increase of 102 part~ per million of weight favoring th~ hi~her c~rbon mono~ide corlcen~r~tion.
1~ rhodium 8~1ution treated in ~xample II
~on~ained initially 2430 parts per million o:E rhodium, 526 p~rt~ per million o ce~ium, 5673 parts per million of 2-hydroxypyridine and t~e ~ol~rent WBE~ tetrsglyme.
All parts are ~y w01ght.

Ru~ No Prea~ur~ ~ % ca Outtpem*
50 psig 125 100 2431 A~mospheric 125 100 2405 3 50 p~ig 17S lO0 2~94

4 Atmospheric 175 100 145 7 S S0 p~ig 125 46 2399 6 Atmo3pheric 125 43 2333 7 50 p81g 175 43 1928 8 Atmospheric 175 43 18~5 Control 25 150 N2 (100%) 2047 Control 25 150 N2 (100%) 2103 * Rhodi~ml foulld in ~olution after run in parts by weight.

17.

:

, E;496~3 96~û

The 8till u3et ln t~s example w~ designed to operat~ co~ti~ sly i~ order ~o more closely approxima~e commercial operation. The still included a kettle which waY a 500 ml 3-necked fl~8k, in which one neck contained a gas sparge tube, another ~eck conta ned ~ thermometer and the third neck cont~ined a distillation column. At t~e top of the column was a distillation head equipped with a cond~nser and rece~Ying ~lask or product recovery.
m e top o ~he condenser was connected ~o ~wo Dry Ice~ -aceto~ cooled traps located in series to collect anyp~oduct which W~8 not condensed due to en~rainment o~
the ~p~ ga~. In the ~ide o the kettle was a with-drawal tu~e containitlg a ~opcock used to remove the stripped rhodium ~olu~ion con~inuous1y and to ~erve as a s~mple poi~t ~or an~ly~is. The distillation colun~ wa~
a 12" hi8~ Pyrex3~ ~lass cylinder having ~ de ~me~ra~
stopcock controlled ~eed tube approximately hal~-way up the column. Feeding was from a graduated flask to the distillation column. The interior o~ the distillation column was packèd with standard stRinless steeL 312 pro-truded packi~g and ~he outside o th~ distill~tion column was wrapped w~th ele~trlc~l wlre which was used to control the temperature o ~he column through the appllcation of ~n electricaL current. In opera~ing the equipment, the flask (kettle) temperature was maintained at 140C. and the bead temperature at the top o~ the column was 70 to 90C. m e overall temperature of the distillation column 18.

~ ~ 6 49 6 8 wa~ m~intained be~wee~ 100-~30C. for optimum refluxing.
e solutions treated i~ this exdmple were fed from the gradua~ed ~lask through the feed tube, into the distillation column and finally into the ke~tle at a rate of 200m1 per hour. m e initial solution charged conta~ned 1.1 weight per cent methanol, 5.1 weight per:~ent ethylene glycol, .3 weight percent other products, 657 ppm by weight of solution of bi~riphenylphosphine ~minium ion, 620 ppm by weight of 4-phen~lpyridine, 610 ppm of rhodium, and the rem~inder was tetr~glyme.
In the f~rst pass, carbon monoxide was ~ed at a rate of 10 liters per hour and the mean residQnce time in the still was 60 minutes. The rhodium loss determined by analysis ater ~illing up ~he still and operating for one hour averaged 8 weight % per hour over five hours of operation. Thi~ ~8 the equivalent o rhodium loss of .067 weight % for a 30 second residence t~le, a residence time whieh is more characteristic o commercial conditions.
During this run~ .6% o~ the feed was ~aken overhead and collected, demonstrating ~he sparge rate o C0 was very low.
All of the liquid materlal was recombined from the overhead and the ket~le, and re~introduced to the still. A second pass wa~ e~ected using a carbon monoxide sparge rate of 20 liters per hour. The rhodium 108s avereged 7% per hour providing es3entially 19.

96~0 ~ ~ 6 ~ ~ 8 the 8~me r~odium 10~3 a~ indica~ed above for a 30 second residence time. Thi8 g~me procedure was repeated again for ~ third pass using nitrogen in~tead as the sparge gas and at a ~p~rge rate o 20 li~ere per hour. In thi8 last ease, the rhodlum 1088 a~eraged 3g weigh~ % per h~ur over flve hour8 co~tinuwu8 ope~atio~ which would be equivalent to about .32 welght % logs for 30 second : re3ide~ t~me.

20.

, . .

Claims (4)

WHAT IS CLAIMED IS:

1. The process of separating products obtained from the reaction of oxide of carbon and hydrogen in a homogeneous liquid phase mixture containing a rhodium carbonyl complex catalyst which comprises volatilizing said products from the mixture while simultaneously maintaining the mixture in contact with carbon monoxide gas.

2. The process of claim 1 wherein the carbon monoxide gas is provided at the surface of said mixture while volatilizing products therefrom.

3. The process of claim 1 wherein the carbon monoxide gas is bubbled through the mixture while volatilizing products therefrom.

4. The process of claim 1 wherein products volatilized from the liquid homogeneous mixture are alcohols selected from the group consisting of ethylene glycol, propylene glycol, glycerine, methanol and mixtures thereof.

21.