GB1563232A - Homogeneous liquid phase process for making alkane polyols - Google Patents

Description

(54) HOMOGENEOUS LIQUID PHASE PROCESS FOR MAKING ALKANE POLYOLS (71) We, UNION CARBIDE CORPORATION, a corporation organized and existing under the laws of the State of New York, United States of America, of 270 Park Avenue, New York, State of New York 10017, United States of America, (assignee of LEONARD KAPLAN and WELLINGTON EPLER WALKER), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the manufacture of alkane polyols and in particular is concerned with a manufacture, as the most valuable component, of ethylene glycol.

The process of this invention constitutes an improvement of the process described and claimed in U.S. Patent 3,833,634, which is equivalent to U.K. Patents 1,424,007 and 1,424,008 and the process described in U.K. Patent Specification No. 1,477,391.

The process described in the aforementioned patent and patent applications involves the reaction of hydrogen and oxides of carbon in the presence of a rhodium carbonyl complex catalyst for the production of the aforementioned alkane polyols.

There is described in copending application No. 53258/75 (Serial No. 1 537 850) a process for making the aforementioned alkane polyols utilizing the rhodium carbonyl complex catalysts as described in the previously mentioned patent and patent application where the reaction is effected in a homogeneous liquid phase mixture using tetramethylene sulfone as the prime solvent for effecting the reaction. The patent application speaks of certain distinct advantages accruing from the use of such a solvent, the most important one of which is that such solvents help to avert the loss of catalyst during the reaction.

U.S. Patent 3,833,634 and U.K. Patent Specification No. 1,477,391 describe the same homogeneous liquid phase process utilizing, in a specific instance, tetraglyme as the solvent. Tetraglyme is an accepted abbreviation for the chemical dimethyl ether of tetraethylene glycol.

It has been determined, quite unexpectedly, that by using a mixture of tetraglyme and a sulfolane, as herein after defined it is possible to obtain higher rates of formation of the alkane polyol, and one is able to operate, if desired, the process more conveniently and at higher temperatures than is possible from operating the same process utilizing instead only tetraglyme or sulfolane as the solvent.

The use of this solvent mixture in a homogeneous liquid phase reaction provides, at essentially any of the operative temperatures and pressures, higher rates of ethylene glycol formation than would be obtainable from the use of either one of the solvents under the same temperature and pressure conditions, assuming that all other ingredients including promoters are the same. In addition, the use of this solvent mixture in such a reaction allows one to take advantage of the fact that as the temperature of the reaction is increased one is able to enhance the rate constant of alkane polyol formation. A further advantage is that this mixture lessens, when used in the reaction, the potential adverse effects which result from the use of a sulfolane at temperatures where, when used alone as a solvent, its instability adversely affects catalyst activity.

According to the present invention there is provided a homogeneous liquid phase process of producing alkane polyols by the reaction of carbon monoxide with hydrogen in the presence of a rhodium catalyst in which rhodium is complexed with carbon monoxide to provide a rhodium carbonyl complex at a temperature between 100"C to 375"C and at a pressure between 500 psia to 50,000 psia, said reaction being effected in a solvent mixture of an amount of tetraglyme and a sulfolane, as hereinafter defined, which under conditions whereby such solvent mixture is essentially inert, the rate of formation of such alkane polyol is greater than would be obtained by effecting said reaction under equal conditions using either tetraglyme or sulfolane as the solvent.

The ratio of tetraglyme and sulfolane, as hereinafter defined, that one employs in the solvent mixture providing the homogeneous liquid phase reaction mixture is predicated upon the conditions of the reaction.

Preferably the process of the invention is carried out at a pressure from 1000 psia to 50,000 psia.

This ratio of tetraglyme and sulfolane, hereinafter be referred to as the solvent ratio", may range from 1 to 20 to 20 to 1, determined on a volume basis. However, it is to be emphasized that in any reaction system, such factors as the ratio of carbon monoxide to hydrogen, temperature and pressure selected, concentrations of added components such as catalysts and promoters, the nature of the promoter, play a role in determining what solvent ratio is most effective. In one system the volume ratio of tetraglyme to sulfolane may be optimum at a value of 1 whereas in another the optimum solvent ratio is 2. This statement is made to emphasize the point that when selecting the appropriate solvent ratio one will be required to explore in a number of experiments in a given reaction system a number of ratios such that the optimum solvent ratios can be determined.

The term sulfolane as used herein and in the claims is intended to cover tetramethylene sulfone and substituted tetramethylene sulfone which provide essentially the same advantages as a result of their solvent characteristics as tetramethylene sulfone.

Illustrative of substituted sulfolanes which are of a kind that may be suitable as a cosolvent with tetraglyme in the practice of this invention are those which are characterized by the following formula:

wherein each of Rl through R, is independently selected from hydrogen; hydroxyl; straight or branched chain alkyl, preferably having from 1 to 12 carbon atoms, most preferably 1 to 6 carbon atoms in the alkyl chain, such as methyl, ethyl, isopropyl, butyl, octyl and dodecyl; a cycloaliphatic group including the monocyclic and bicyclic groups such as cyclopentyl, cyclohexyl and bicyclo [2.2.1] heptyl; or an aryl, alkylaryl, or aralkyl group such as phenyl, naphthyl, xylyl, tolyl, benzyl and beta-phenylethyl; an ether of the formula tO--R") wherein R" may be aryl or lower alkyl having from 1 to 12 carbon atoms, preferably 1 to 4 carbon atoms in the alkyl chain; an alkylene or polyalkylene ether of the formula (OCnH2n)OR00 wherein n has an average value of from 1 to about 4, x has an average value of from 1 to about 150, preferably 1 to about 20, most preferably 1 to about 4, and R00 may be hydrogen or alkyl having from 1 to 6 carbon atoms in the alkyl chain, such as poly(oxyethylene), poly(oxypropylene), poly(oxyethylene-oxypropylene), alkylene and polyalkylene glycols and lower alkyl ethers thereof; a carboxylate group of the formula:

wherein y may have any value between 0 and 12, m and m may be zero or one provided that when either m or m" is one the other is zero, and R""" may be a lower alkyl group having from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms, or aryl; provided that not all of the R~s's are hydrogen.

Preferably the sulfolane used in the practice of the present invention is tetramethylene sulfone, i.e., tetrahydrothiophene-1,1-dioxide. In those instances where it may be desirable to use a substituted sulfolane those substituted in the 3 or 3,4 positions of the sulfolane ring are preferred.

The rhodium carbonyl complexes suitable for use in the practice of the present invention are those wherein the complex is at least one of (1) rhodium in complex combination with carbon monoxide, (2) rhodium in complex combination with carbon monoxide and hydrogen. (3) rhodium in complex combination with carbon monoxide and at least one Lewis base, (4) rhodium in complex combination with carbon monoxide, hydrogen and at least one Lewis base, and (5) mixtures thereof.

Moreover, the rhodium carbonyl complexes of this invention may be in the form of rhodium carbonyl clusters. P. Chini, in a review article entitled "The Closed Metal Carbonyl Clusters" published in Review (1968). Inorganica Chimica Acta, pages 3050, states that a metal cluster compound is a "a finite group of metal atoms which are held together entirely, mainly, or at least to a significant extent, by bonds directly between the metal atoms even though some non-metal atoms may be asso ciated intimately with the "cluster". The rhodium carbonyl cluster compounds of this invention contain rhodium bonded to rhodium or rhodium bonded to another metal, such as cobalt, and/or iridium. The preferred rhodium carbonyl cluster com pounds of this invention are those which contain rhodium-rhodium bonds. These compounds desirably contain carbon and oxygen in the form of carbonyl (4O), in which the carbonyl may be "terminal", "edge-bridging", and/or "face-bridging".

They may also contain hydrogen and carbon in forms other than carbonyl. The following are illustrative of what is believed to be the structure of two distinct rhodium carbonyl clusters and both are suitable for use in this invention.

The structures of the rhodium carbonyl clusters may be ascertained by X-ray crystal diffraction, nuclear magnetic resonance (NMR) spectra, or infrared spectra as disclosed in the article entitled "Synthesis and Properties of the Derivatives of the [Rh12(CO),0] 2- Anion" by P. Chini and S. Martinengo; appearing in Inorganica Chimica Acta, 3:2 pp299-302, June (1969). Of particular analytical utility in the present invention is the use of infrared spectroscopy which allows for characterization of the particular rhodium carbonyl complex present during the operation of the process of the present invention.

The rhodium carbonyl complex is, as characterized above, a rhodium containing compound in which the rhodium is complexed with CO. This can be achieved with just carbon monoxide or in addition to the carbon monoxide there may be included hydrogen and/or organic or inorganic Lewis base promoters to create the complex.

In the last case, "complex" means a coordination compound formed by the union of one or more electronically rich molecules or atoms capable of independent existence with one or more electronically poor molecules or atoms, each of which is also capable of independent existence. The precise role of these Lewis bases in the reaction of the present invention is not fully appreciated at present. They may be functioning as ligands and/or forming counter-ions under the reaction conditions of the present process or they may be functioning just merely as Lewis bases and neutralizing or tying up a molecular species which if allowed to remain "free" or in its non-basebound state would adversely affect the productivity of the present invention.

Organic Lewis bases which are suitable in the practice of the present invention contain at least one Lewis base oxygen atom and/or one Lewis base nitrogen atom said atoms possessing a pair of electrons available for the formation of coordinate bonds.

In suitable embodiments the organic Lewis bases contain from 1 and upwards to 4 Lewis base atoms, preferably from 1 to 3 such atoms, and most preferably 1 or 2 Lewis base atoms. These organic Lewis bases are said to be multidentate or polydenate, that is to say, they are bidentate, tridentate, or quadridentate, depending on whether 2, 3 or 4 Lewis base atoms are involved.

Those organic Lewis bases which contain at least one Lewis base nitrogen atom plus at least one Lewis base oxygen atom will oftentimes hereinafter be referred to as "organic aza-oxa" Lewis bases.

Suitable organic nitrogen Lewis bases ("aza" only) most generally contain carbon, hydrogen, and nitrogen atoms. Suitable organic oxygen Lewis bases mast generally contain carbon, hydrogen, and oxygen atoms. Suitable organic aza-oxa Lewis bases most generally contain carbon, hydrogen, oxygen, and nitrogen atoms.

The carbon atoms can be acyclic and/or cyclic such as aliphatic, cycloaliphatic and aromatic (including fused and bridged) carbon atoms. Preferably, the organic Lewis bases contain from 2 to 60, most preferably 2 to 40 carbon atoms. The nitrogen atoms can be in the form of imino (-N=), amino

nitrilo (we), etc. Desirably, the Lewis base nitrogen atoms are in the form of imino nitrogen and/or amino nitrogen. The oxygen atoms can be in the form of groups such as hydroxyl (aliphatic or phenolic),

0 0 0 II II carboxyl (*COH), carbonyloxy (-CO-), oxy (-0-), carbonyl (4), etc., all of said groups containing Lewis base oxygen atoms. In this respect, it is the "hydroxyl" oxygen in the

group and the "oxy" oxygen in the

group that are acting as the Lewis base atoms. The organic Lewis bases may also contain other atoms and/or groups such as alkyl, cycloalkyl, aryl, chloro, trialkylsilyl, and the like.

Illustrative organic oxygen Lewis bases include, by way of illustrations, glycolic acid, methoxyacetic acid, ethoxyacetic acid, diglycolic acid, diethyl ether, tetrahydro furan, dioxane, tetrahydropyran, pyrocatechol, citric acid, 2 - methoxyethanol, 2 ethoxyethanol, 2 - n - propoxyethanol, 2 - n - butylethanol, 1,2,3 - trihydroxybenzene, 1,2,4 - trihydroxybenzene, 2,3 - dihydroxynaphthalene, cyclohexane - 1,2 - diol, oxetane, 1,2 - dimethoxybenzene, 1,2 - diethoxybenzene, methyl acetate, ethanol, 1,2 dimethoxyethane, 1,2 - diethoxyethane, 1,2 - di - n - propoxyethane, 1,2 - di butoxyethane, pentane - 2,4 - di one, hexane - 2,4 - dione, heptane - 3,5 - dione, octane2,4 - dione, 1 - phenylbutane - 1,3 - dione, 3 - methylpentane - 2,4 - dione; and the mono- and dialkyl ethers of propylene glycol, of diethylene glycol, and of dipropylene glycol.

Illustrative organic aza-oxa Lewis bases include, for example, the alkanolamines, such as, ethanolamine, diethanolamine, isopropanolamine and di - n - propanolamine N,N - dimethyiglycine, N,N - diethylglycine; iminodiacetic acid, N - methyliminodiacetic acid; N - methyldiethanolamine; 2 - hydroxypyridine, 2,4 - dihydroxypyridine, 2 - methoxypyridine, 2,6 - dimethoxypyridine, 2 - ethoxypyridine; lower alkyl substituted hydroxypyridines, such as 4 - methyl - 2 - hydroxypyridine and 4methyl - 2,6 - dihydroxypyridine; morpholine, substituted morpholines, such as 4methylmorpholine, 4 - phenylmorpholine; picolinic acid, methyl-substituted picolinic acid; nitrilotriacetic acid, 2,5 - dicarboxypiperazine, N - (2 - hydroxyethyl) iminodiacetic acid, ethylenediaminetetraacetic acid; 2,6 - dicarboxypyridine; 8 - hydroxyquinoline, 2 - carboxyquinoline, cyclohexane - 1,2 - diamine - N,N,N',N' - tetraacetic acid and the tetramethyl ester of ethylene diamine-tetraacetic acid.

Illustrative of the Lewis base nitrogen ("aza") containing compounds suitable for use in the practice of the present invention are ammonia and the amines. Any primary, secondary, or tertiary amine is suitable in the practice of the present invention.

This includes the mono-, di-, tri-, and polyamines and those compounds in which the Lewis base nitrogen forms part of a ring structure as in pyridine, quinoline, pyrimidine, morpholine and hexamethylene tetraamine. In addition any compound capable of yielding an amino nitrogen under the reaction conditions of the present invention is suitable, as in the case of an amide, such as formamide and urea, or an oxime. Further illustrative of these Lewis base nitrogen compounds are aliphatic amines such as methylamine, ethylamine, n-propylamine, isopropylamine, octylamine, dodecylamine, dimethylamine, diethylamine, diisoamylamine, methylethylamine, diisobutylamine, trimethylamine, methyldiethylamine, triisobutylamine and tridecylamine; aliphatic and aromatic di- and polyamines such as as 1,2 - ethanediamine, 1,3 - propanediamine, N,N,N'N' - tetramethylenediamine, N,N,N',N' - tetraethylethylenediamine, N,N,N'N'tetra - n - propylethylenediamine, N,N,N',N' - tetrabutylethylenediamine, ophenylenediamine, m - phenylenediamine, p - phenylenediamine, p - tolylenediamine, o - tolidene, N,N,N',N' - tetramethyl - p - phenylenediamine and N,N,N',N' - tetraethyl - 4,4' - biphenyldiamine; aromatic amines such as aniline, 1 - naphthylamine, 2naphthylamine, p - toluidine, o-3-xylidine, p - 2 - xylidine, benzylamine, diphenylamine, dimethylaniline, diethylaniline, N - phenyl - 1 - naphthylamine and bis - (1,8)dimethylaminonaphthalene; alicyclic amines such as cyclohexylamine and dicyclohexylamine; heterocyclic amines such as piperidine; substituted piperidines such as 2 - methylpiperidine, 3 - methylpiperidine, 4 - ethylpiperidine, and 3 - phenyl; piperidine; pyridine; substituted pyridines such as 2 - methylpyridine, 2 - phenylpyridine, 2 - methyl - 4 - ethylpyridine, 2,4,6 - trimethylpyridine, 2 - dodecylpyridine, 2 - chloropyridine, and 2 - (dimethylamino)pyridine; quinoline; substituted quinolines, such as 2 - (dimethylamino) - 6 - methoxyquinoline; 4,5 - phenanthroline; 1,8phenanthroline; 1,5 - phenanthroline; piperazine; substituted piperazines such as Nmethylpiperazine, N - ethylpiperazine, 2,N - dimethylpiperazine; 2,2' - dipyridyl, methyl-substituted 2,2' - dipyridyl; ethyl-substituted 2,2' - dipyridyl; 4 - triethylsilyl - (2,' - dipyridyl; 1,4 - diazabicyclo [2.2.2] octane, methyl substituted 1,4 - diazabicyclo [2.2.2] octane and purine.

Illustrative of the inorganic Lewis bases useful in the practice of the present invention are ammonia, hydroxides and halides, such as chloride, bromide, iodide, or fluoride; or mixtures thereof.

Any of the above Lewis bases may be provided to the reaction in compound form or as ligands which are in complex combination with the rhodium carbonyl compound initially charged to the reactor.

The precise role of the rhodium carbonyl complexes, such as the rhodium carbonyl clusters characterized previously, in the reaction of hydrogen with carbon monoxide to produce polyhydric alcohols is not fully appreciated at present Under the reaction conditions of the present process the carbonyl complexes are believed to be anionic in their active forms. Rhodium carbonyl anions are known to be involved in the following set of reactions as indicated by S. Martinengo and P. Chini, in Gazz.

Chim. Ital., 102, 344 (1972) and the references cited therein.

(I) [Rh2(col34 IRhll (ro)]2 h DRh6lco)15] [Rh6(co)1]' [Rh (Co)3 S Co [R(co)15]2 . (oo) Co [Rh7(C0116] 4Q[Rh4lC0)11] [Rh(U))L ] * electron Infrared spectra under reaction conditions of the present process have shown both the Rh(CO)4- and [Rh12(CO),,e] 2- anions to be present at various concentrations at different times of the reaction. Therefore the set of reactions and equilibria shown in I above may represent the active rhodium carbonyl species responsible for polyhydric alcohol formation or may be merely symptomatic of some further intermediate transitory rhodium carbonyl structure which serves to convert the carbon monoxide and hydrogen to the polyhydric alcohol.

Assuming the active catalytic species is a rhodium carbonyl complex anion, or the formation of the active species under reaction conditions is directly dependent on the existence of these anions, allows one to better explain, in terms of reaction rates, productivity and catalyst stability, the role the sulfone solvents, particularly the tetra methylene sulfones, play in the reaction whereby hydrogen and carbon monoxide are converted to the polyhydric alcohol. It is believed that the sulfones enhance the reactivity of these rhodium carbonyl complex anions because a "naked", reactive anion is produced. Naked rhodium carbonyl anions are believed to be produced under the reaction conditions of the present process because the sulfone solvent decreases any tendency of the rhodium carbonyl anions to ion pair, the rhodium carbonyl anions are not strongly solvated, nor is the rhodium strongly complexed by the solvent all of which tend to produce an anion having a higher degree of reactivity under the reaction conditions employed.

The novel process is suitably effected over a wide superatmospheric pressure range of from about 800 psia to about 50,000 psia. Pressures as high as 50,000 psia, and higher can be employed but with no apparent advantages attendant thereto which offset the unattractive plant investment outlay required for such high pressure equipment.

In one embodiment of this invention the upper pressure limitation is approxi mately 16,000 psia. Effecting the present process below about 16,000 psia, especially below about 13,000 psia, and preferably at pressures below about 8000 psia, results in cost advantages which are associated with low pressure equipment requirements.

However, when practicing the present invention at pressures below about 12,000 psia, the rate of desired product formation is quite slow and in order to obtain a faster reaction rate and/or higher conversions to the desired product there is provided to the reaction a promoter which may be a salt and/or an organic Lewis base nitrogen compound. In those instances where the Lewis base nitrogen compound is contained as a ligand in the rhodium carbonyl complex charged to the reactor or where anion of the salt promoter charged to the reactor is a rhodium carbonyl complex such as cesium triacontacarbonylrhodate, it may not be necessary to add to the reaction any additional amounts of these promoters. A suitable pressure range for effecting the reaction in the presence of these promoters is from 1000 psia to 16,000 psia, preferably from 4000 to 16,000 psia.

Suitable salts useful in the practice of the present invention at pressures below about 16,000 psia include any organic or inorganic salt which does not adversely affect the production of polyhydric alcohols. Experimental work completed to date indicates that any salt will show this promoter effect under some, but not all, glycol-producing conditions. Illustrative of the salts useful in the practice of the present invention are the ammonium salts and the salts of the metals of Group I and Group II of the Periodic Table (Handbook of Chemistry and Physics - 50th Edition) for instance the halide, hydroxide, alkoxide, phenoxide and carboxylate salts such as sodium fluoride, cesium fluoride, cesium pyridinolate, cesium formate, cesium acetate, cesium benzoate, cesium p - methylsulfonyl benzoate (CH3SO2C6H4COO)Cs, rubidium acetate, magnesium acetate, strontium acetate, ammonium formate and ammonium benzoate. Preferred are the cesium and ammonium carboxylate salts, most preferably their formate, benzoate and para-lower alkyl sulfonyl benzoate salts.

Also useful in the practice of the present invention are organic salts of the following formula:

quaternary ammonium salts

bis (triorgano phosphine)iminium salts wherein R1 through Re in formulas (II) and (III) above are any organic radicals which do not adversely affect the production of polyhydric alcohols by reacting oxides of carbon with hydrogen in the presence of the aforedefined rhodium carbonyl complex, such as a straight or branched chain alkyl group, having from 1 to 20 carbon atoms in the alkyl chain, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, octyl, 2-ethyl- hexyl and dodecyl; or a cycloaliphatic group including the monocyclic and bicyclio groups cyclopentyl, cyclohexyl, and bicyclo[2.2.1] heptyl groups or an aryl, alkylaryl, or aralkyl group such as phenyl, naphthyl, xylyl, tolyl, t-butylphenyl, benzyl, beta phenylethyl and 3-phenylpropyl; or a functionally substituted alkyl such as beta hydroxyethyl, ethoxymethyl, ethoxyethyl and phenoxyethyl; or a polyalkylene ether group of the formula -(-CnH2nO)x-OR wherein n has an average value from 1 to 4, x has an average value from 2 to about 150, and R may be hydrogen or alkyl of 1 to about 12 carbon atoms. Illustrative of such polyalkylene ether groups are poly (oxyethylene), poly(oxypropylene), poly ( oxyethyleneoxypropylene) and poly ( oxy- ethyleneoxybutylene, Y in formulas II and III above may be any anion which does not adversely affect the production of polyhydric alcohols in the practice of the present invention such as hydroxide; a halide, for instance fluoride, chloride, bromide and iodide; a carboxylate group, such as formate, acetate, propionate and benzoate; an alkoxide group such as methoxide or ethoxide; phenoxide group; a functionally substituted alkoxide or phenoxide group such as methoxyoxide, ethoxyethoxide and phenoxyethoxide; a pyridinolate or quinolate group; and others. Preferably Y in formulas II and III, above, is a carboxylate, most preferably formate, acetate and benzoate.

A suitable method for preparing the bis(triorgano phosphine)iminium salts is disclosed in an article by Appel, R. and Hanas, A. appearing in Z. Anorg. u. Allg.

Chem., 311, 290, (1961).

Other organic salts useful in the practice of the present invention include the quatemized heterocylic amine salts such as the pyridinium, piperidinium, morpho linium and quinolinium salts, e.g., N - ethylpyridinium fluoride, N - methyl morpholinium benzoate, N - phenylpiperidinium hydroxide and N,N' - dimethyl - 2,2 bipyridinium acetate.

In one of the embodiments of the present invention, the anion of the above salt promoters may be any of the rhodium carbonyl anions. Suitable rhodium carbonyl anions include [Rh6(CO)l5]2-; [Rh(CO)1Y] wherein Y may be halogen such as chlorine, bromine, or iodine, [Rh6(CO)l5(COOR")] wherein R" is lower alkyl or aryl such as methyl, ethyl, or phenyl; [Rh6(CO)14]2-; [Rh7(CO)1]'; and [Rhl2(CO)so]2~ Under reaction conditions where a salt promoter is employed the salt is desirably added with the intial charge of reactants in amounts of from about 0.5 to about 2.0 moles, preferably from about 0.8 to about 1.6 moles, and most preferably from about 0.9 to 1.4 moles of salt for every five atoms of rhodium present in the reaction mixture.

The Lewis base nitrogen promoters may be any of the Lewis base nitrogen or organic aza-oxa Lewis base compounds defined above. Preferably the Lewis base nitrogen promoters are gamines. This also includes those compounds where the nitrogen is part of a heterocyclic ring such as the pyridines, pyrimidines, piperidines, morpholines, quinolines and the like. Illustrative of these preferred Lewis base promoters are pyridine, 2,4,6 - trimethylpyridine, 4 - dimethylaminopyridine, 4 - tridecylpyridine, isobutylamine, triethylamone, N - methylpiperidine, N - methylmorpholine, bis- (1,8)dimethylaminonaphthalene, 1,4 - diazabicyclo - [2.2.2] octane, and quinuclidine.

Under reaction conditions where a Lewis base nitrogen compound is used as a promoter it is preferably used in amounts from about 0.02 to about 2 equivalents of promoter, most preferably from about 0.1 to about 1 equivalent of promoter, for every mole of rhodium in the reaction mixture. The number of equivalents of promoter is equal to the number of moles of promoter times the number of nitrogen atoms in each molecule.

Mixtures of the above salt and amine low pressure promoters may be used in the practice of the present invention.

The salt and/or Lewis base nitrogen low pressure promoters may be added to the reaction in compound form or there may be added to the reactor any substance capable of generating the salt and/or the amine promoter in situ either prior to or during the reaction conditions of the present invention.

For instance an amide such as formamide, urea, and the like or an oxime may be added to the reactor in place of the amine promoter.

Another and preferred group of low pressure promoters include the trialkanol- amine borates, preferably those having the formula:

wherein Ra, Rb, and Ro may be at least one of hydrogen or lower alkyl having from 1 to 12 carbon atoms in the alkyl chain. Most preferably the trialkanolamine borates useful in the practice of the present invention are triethanolamine borate and triiso propanolamine borate.

The quantity of catalyst employed is not narrowly critical and can vary over a wide range. In general, the novel process is desirably conducted in the presence of a catalytically effective quantity of the active rhodium species which gives a suitable and reasonable reaction rate. Reaction proceeds when employing as little as about 1 X 10' weight percent, and even lesser amounts, of rhodium metal based on the total weight of reaction mixture. The upper concentration limit can be quite high, e.g., about thirty weight percent rhodium, and higher, and the realistic upper limit in practicing the invention appears to be dictated and controlled more by economics in view of the exceedingly high cost of rhodium metal and rhodium compounds. Depending on various factors such as the promoter of choice, the partial pressures of hydrogen and oxides of carbon, the total operative pressure of the system, the operative temperature, the choice of the organic co-diluent, and other considerations, a catalyst concentration of from about 1 X 10-5 to about 5 weight percent rhodium (contained in the complex catalyst) based on the total weight of reaction mixture, is generally desirable in the practice of the invention.

The process of the invention is conducted at a temperature in the range of from 1000C to 3750C. At the lower end of the temperature range, and lower, the rate of reaction to desired product becomes markedly slow. At the upper temperature range, and beyond, signs of some catalyst instability are noted. Notwithstanding this factor, reaction continues and polyhydric alcohols and/or their derivatives are produced.

Additionally, one should take notice of the equilibrium reaction for forming ethylene glycol: 2 CO + 3H2 = HOCH2CH2OH At relatively high temperatures the equilibrium increasingly favors the left hand side of the equation. To drive the reaction to the formation of increased quantities of ethylene glycol, higher partial pressures of carbon monoxide and hydrogen are required.

Processes based on correspondingly higher operative pressures, however, do not represent preferred embodiments of the invention in view of the high investment costs associated with erecting chemical plants which utilize high pressure utilities and the necessity of fabricating equipment capable of withstanding such enormous pressures.

Preferred operative temperatures are between 150"C and 3200 C, and most preferably from 2100C to 300"C.

The novel process is effected for a period of time sufficient to produce the desired alkane polyol(s). In general, the residence time can vary from minutes to several hours, e.g., from a few minutes to approximately 24 hours, and longer. It is readily appreciated that the residence period will be influenced to a significant extent by the reaction temperature, the concentration and choice of the catalyst, the total gas pressure and the partial pressure exerted by its components, the concentration and other factors. The synthesis of the desired product(s) by the reaction of hydrogen with carbon monoxide is suitably conducted under operative conditions which give reasonable reaction rates.

The relative amounts of carbon monoxide and hydrogen which are initially present in the reaction mixture can be varied over a wide range. In general, the mole ratio of CO:H2 is in the range of from 20:1 to 1:20, suitably from 10:1 to 1:10, and preferably from 5:1 to 1:5.

It is to be understood, however, that molar ratios outside the aforestated broad range may be employed. Substances or reaction mixtures which give rise to the formation of carbon monoxide and hydrogen under the reaction conditions may be employed instead of mixtures comprising carbon monoxide and hydrogen which are used in preferred embodiments in the practice of the invention. For instance, polyhydric alcohols are obtained by using mixtures containing carbon dioxide and hydrogen.

Mixtures of carbon dioxide, carbon monoxide and hydrogen can also be employed. If desired, the reaction mixture can comprise steam and carbon monoxide.

The novel process can be executed in a batch, semi-continuous, or continuous fashion. The reaction can be conducted in a single reaction zone or a plurality of reaction zones, in series or in parallel, or it may be conducted intermittently or continuously in an elongated tubular zone or series of such zones. The material of construction should be such that it is inert during the reaction and the fabrication of the equipment should be able to withstand the reaction temperature and pressure.

The reaction zone can be fitted with internal and/or external heat exchanger(s) to thus control undue temperature fluctuations, or to prevent any possible "run-away" reaction temperatures due to the exothermic nature of the reaction. In preferred embodiments of the invention, agitation means to vary the degree of mixing of the reaction mixture can be suitably employed. Mixing induced by vibration, shaker,, stirrer, rotation, oscillation, ultrasonics, etc., are all illustrative of the types of agitation means which are contemplated. Such means are available and well-known to the art. The catalyst may be initially introduced into the reaction zone batchwise, or it may be continuously or intermittently introduced into such zone during the course of the synthesis reaction. Means to introduce and/or adjust the reactants, either intermittently or continuously, into the reaction zone during the course of the reaction can be conveniently utilized in the novel process especially to maintain the desired molar ratios of and the partial pressures exerted by the reactants.

As intiniated previously, the operative conditions can be adjusted to optimize the conversion of the desired product and/or the economics of the novel process. In a continuous process, for instance, when it is preferred to operate at relatively low conversions, it is generally desirable to recirculate unreacted synthesis gas with/ without make-up carbon monoxide and hydrogen to the reaction. Recovery of the desired product can be achieved by methods well-known in the art such as by dis tillation, fractionation, extraction, and the like. A fraction comprising rhodium catalyst, generally contained in byproducts and/or normally liquid organic diluent, can be recycled to the reaction zone, if desired. All or a portion of such fraction can be removed for recovery of the rhodium values or regeneration to the active catalyst and can be intermittently added to the recycle stream or directly to the reaction zone.

The active forms of the rhodium carbonyl clusters may be prepared by various techniques. They can be preformed and then introduced into the reaction zone.

Alternatively, any the host of rhodium-containing substances as well as any of the low pressures promoters can be introduced into the reaction zone and, under the operative conditions of the process (which of course includes hydrogen and carbon monoxide), the active rhodium carbonyl cluster can be generated in situ. Illustrative of rhodium-containing substances which can be conveniently introduced or placed in the synthesis zone include, for example, rhodium oxide (Rh2O3), tetrarhodium dodeca carbonyl, dirhodium octacarbonyl, hexarhodium hexadecacarbonyl (Rh(CO)l6), rhodium(II) formate, rhodium(II) acetate, rhodium(II) propionate, rhodium(II) butyrate, rhodium(II) valerate, rhodium(III) naphthenate, rhodium dicarbonyl acetylacetonate, rhodium tri(acetylacetonate), rhodium trihydroxide, indenyl-rhodium dicarbonyl, rhodium dicarbonyl (1 - phenylbutane - 1,3 - dione), tris(hexane - 2,4 dionato)rhodium(III), tris(heptane - 2,4 - dionato)rhodium(III), tris - (1 - phenylbutane - 1,3 - dionato)rhodium(III), tris(3 - methylpentane- 2,4 - dinato)rhodium (III), tris(l - cyclohexylbutane - 1,5 - dionato)rhodium(III), triacontacarbonyl rhodium salts and rhodium-containing compounds deposited on porous supports or carriers capable of providing rhodium carbonyls in solution, and others.

The preparation of the rhodium carbonyl complex compounds can be conveniently carried out in the solvent mixture. Tetrarhodium dodecacarbonyl, though of limited solubility, can be added to the solvent in a finely divided form. Any of several of the rhodium-containing compounds illustrated previously can be employed in lieu of tetrarhodium dodecacarbonyl. The organic Lewis bases such as pyridine, or other promoters, such as aforedefined salt promoters, can also be added thereto. The rhodium carbonyl complex or cluster forming reaction can be effected under a carbon monoxide pressure, with or without H2, of about 1 to 15 atmospheres, and higher, using a temperature of about 30"C. to about 100"C., for a period of time ranging from minutes to a few days, generally from about 30 minutes to about 24 hours. The resulting rhodium carbonyl complex contained in the solvent mixture is catalytically active in this process.

In preparing the aforesaid complexes, one can suitably employ from about .01 to about 25 moles salt or Lewis base nitrogen promoters per mole of rhodium (contained in the rhodium compound used as a rhodium source). Ratios outside this stated range can be employed especially when it is desirable to use diluent quantities of the low pressure promoters.

The equipment arrangement and procedure which provides the capability for determining the existence of anionic rhodium carbonyl complexes or clusters having defined infrared spectrum characteristics, during the course of the manufacture of polyhydric alcohols from carbon monoxide and hydrogen, pursuant to this invention is disclosed and schematically depicted in U.K. Patent Specification No. 1,477,391, the disclosure of which is incorporated herein by reference.

A particularly desirable infrared cell constructure is described in copending U.S.

Patent 3,886,364, issued May 27, 1975 and its disclosure of a preferred cell constructure is incorporated herein by reference.

The reaction of the present invention is conducted in what is believed to be a homogeneous liquid phase, which means that the catalyst, the reaction products and the promoter if present are in solution. Though the reaction to produce alcohols is essentially homogeneous, there may be small amounts of insoluble catalyst particles depending on the reaction conditions employed.

The ~following examples are merely illustrative and are not presented as a definition of the limits of the invention.

The sulfolane used in the following examples is the unsubstituted tetramethylene sulfone and was purified prior to use according to the method disclosed by E. N.

Arnert and C. F. Douty, reported in the Journal of the American Chemical Society, 86, 409 (1964).

Other materials used in the following examples possessed the following characteristics: cesium benzoate (recrystallized from H2O, Analysis -- Found: C, 32.62; H, 1.90. Calcd. for C7H,O2Cs: C, 33.10; H, 1.98). Triisopropanolamine borate (mp.

155 157.5 ); p-MeSO2C EI4.CO2Cs; cesium para methylsulfonylbenzoate (recrystallized from H,O, Analysis -- Found: C, 28.26; H, 2.05. Calcd. for C,H,O,SCs: C, 28.90; H, 2.13).

In the examples below, the following procedure was employed: A 150 ml. capacity stainless steel reactor capable of withstanding pressures up to 7,000 atmospheres was charged with a premix of 75 cubic centimeters (cc) of a specified solvent mixture, a specified amount of rhodium in the form of rhodium dicarbonylacetylacetonate, and specified amounts of one or more of an amine promoter, a borate promoter, and salt promoter. The reactor was sealed and charged with a gaseous mixture containing equal molar amounts of carbon monoxide and hydrogen to a pressure as specified below. Heat was applied to the reactor and its contents; when the temperature of the mixture inside the reactor reached 1900C, as measured by a suitably placed thermocouple, an additional adjustment of carbon monoxide and hydrogen (H2:CO= 1:1 mole ratio) was made to bring the pressure back to 8000 psig. The temperatures and pressures were maintained as indicated in the table.

After the reaction was terminated, the vessel and its contents were cooled to room temperature, the excess gas vented and the reaction product mixture was removed.

Analysis of the reaction product mixture was made by gas chromatographic analysis using a Hewlett Packard FM model 810 Research Chromatograph.

Analysis of the product mixture in terms of ethylene glycol and methanol, are shown in the tables, as well as the rhodium recovery, based on the total rhodium charged to the reactor.

Rhodium recovery was determined by atomic absorption analysis of the contents of the reactor after the venting of the unreacted gases at the end of the reaction. A further analysis was run on a "wash" of the reactor. The wash of the reactor consisted of charging to the reactor 100 cc of the solvent used for that experiment, and bringing the reactor and its contents to a temperature of 1600C and a pressure of 14,000 to 15,000 psig with carbon monoxide and hydrogen and maintaining these conditions for a period of 30 minutes. The reactor was then cooled and the unreacted gases vented and an atomic absorption analysis for rhodium was run on the reactor's contents.

The rhodium recovery values may be characterized as the percent rhodium based on the total rhodium charged to the reactor that is soluble or suspended in the reaction mixture and the wash after the specified reaction time.

Examples 1, 6, 7, 12, 16, 18, 23, 24, 27 and 32 are not examples of the invention and are included for comparative purposes only.

EXAMPLES Sulfolane/ m.moles Example Tetraglyme Pressure, Temps., of No. Ratio (V/V) psi C Rh Promoters Added and Amount, m.moles 1 100/0 8000 240 3 cesium benzoate, 0.65 2 76/24 8000 240 3 cesium benzoate, 0.65 3 54/46 8000 240 3 cesium benzoate, 0.65 4 36/64 8000 240 3 cesium benzoate, 0.65 5 17/83 8000 240 3 cesium benzoate, 0.65 6 0/100 8000 240 3 cesium benzoate, 0.65 7 100/0 8000 240 3 pyridine, 0.63 8 76/24 8000 240 3 pyridine, 0.63 9 54/46 8000 240 3 pyridine, 0.63 10 36/64 8000 240 3 pyridine, 0.63 11 17/83 8000 240 3 pyridine, 0.63 12 100/0 8000 260 3 ethylenedimorpholine, 7.0 13 76/24 8000 260 3 ethylenedimorpholine, 7.0 14 50/50 8000 260 3 ethylenedimorpholine, 7.0 15 24/76 8000 260 3 ethylenedimorpholine, 7.0 16 100/0 8000 240 3 N-methylmorpholine, 5.0 17 76/24 8000 240 3 N-methylmorpholine, 5.0 18 100/0 8000 260 3 cesium formate, 0.65; triisoproparolamine borate, 2.5 19 76/24 8000 260 3 cesium formate, 0.65; triisoproparolamine borate, 2.5 20 50/50 8000 260 3 cesium formate, 0.65; triisoproparolamine borate, 2.5 21 50/50 15000 240 3 cesium benzoate, 0.65; triisoproparolamine borate, 2.5 22 13/87 15000 240 3 cesium benzoate, 0.65; triisoproparolamine borate, 2.5 23 0/100 15000 240 3 cesium benzoate, 0.65; triisoproparolamine borate, 2.5 EXAMPLES (Continued) Sulfolane/ m.moles Examples Tetraglyme Pressure, Temp., of No. Ratio (V/V) psi C Rh Promoters Added and Amount, m.moles 24 100/0 15000 260 3 ethylenedimorpholine, 7.0 25 50/50 15000 260 3 ethylenedimorpholine, 7.0 26 24/76 15000 260 3 cesium benzoate, 0.75; pyridine, 1.25 27 0/100 15000 260 1.5 cesium benzoate, 0.375; pyridine, 1.25 28 50/50 15000 270 1.5 cesium benzoate, 0.375; pyridine, 1.25 29 24/76 15000 270 1.5 cesium benzoate, 0.375; pyridine, 1.25 30 50/50 15000 280 1.5 cesium benzoate, 0.375; pyridine, 1.25 31 24/76 15000 280 1.5 cesium benzoate, 0.375; pyridine, 1.25 32 0/100 12500 250 6 cesium benzoate, 1.5; pyridine, 2.5 33 24/76 12500 250 6 cesium benzoate, 1.5; pyridine, 2.5 34 24/76 12500 260 3 cesium benzoate, 0.75; pyridine, 1.25 35 50/50 12500 260 3 cesium benzoate, 0.75; pyridine, 1.25 36 24/76 12500 270 1.5 cesium benzoate, 0.375; pyridine, 1.25 37 50/50 12500 270 1.5 cesium benzoate, 0.375; pyridine, 1.25 38 60/40 12500 270 1.5 cesium benzoate, 0.375; pyridine, 1.25 39 24/76 12500 270 3 cesium f-methylsulfonylbenzoate, 0.75; triisoproparolamine borate, 2.5 40 50/50 12500 270 3 cesium f-methylsulfonylbenzoate, 0.75; triisoproparolamine borate, 2.5 EXAMPLES (Continued) Ethylene Rh Recovery, % Gas Uptake Time of Example Methanol, Glycol, No. M hr-1(g) M hr-1(g) Reactor Wash (CO+H2), psi Reaction, hr 1 0.31(3.0) 0.23(4.2) 74 6 2800 4.0 2 0.29(2.8) 0.22(4.0) 74 10 3250 4.0 3 0.31(3.0) 0.28(5.2) 74 11 2950 4.0 4 0.34(3.3) 0.26(4.9) 68 20 2850 4.0 5 0.36(3.5) 0.26(4.9) 62 21 3150 4.0 6 0.23(2.2) 0.16(2.9) 27 52 2100 4.0 7 0.29(2.8) 0.24(4.5) 77 6 3000 4.0 8 0.27(2.6) 0.35(6.5) 71 6 3750 4.0 9 0.28(2.7) 0.29(5.3) 62 10 3500 4.0 10 0.27(2.6) 0.28(5.2) 54 5 2850 4.0 11 0.27(2.6) 0.13(2.4) 33 0 1700 4.0 12 0.54(5.2) 0.38(7.1) 81 6 5600 4.0 13 0.57(5.5) 0.38(7.1) 68 7 6500 4.0 14 0.62(6.0) 0.41(7.7) 67 8 6000 4.0 15 0.25(2.4) 0.06(1.1) 11 4 2050 4.0 16 0.37(3.6) 0.29(5.3) 80 4 4300 4.0 17 0.32(3.1) 0.31(5.7) 74 8 4200 4.0 18 0.47(4.5) 0.32(6.0) 77 10 4100 4.0 19 0.57(5.5) 0.35(6.5) 77 6 4600 4.0 20 0.60(5.8) 0.39(7.2) 53 12 5600 4.0 21 1.1 (1.7) 2.1 (6.3) 102 6 6250 0.65 22 1.6 (4.7) 2.0(11.7) 82 5 8200 1.25 23 1.6 (3.6) 1.4 (6.2) 69 8 6100 0.96 EXAMPLES (Continued) Ethylene Rh Recovery, % Example Methanol, Glycol, Gas Uptake Time of No. M hr-1(g) M hr-1(g) Reactor Wash (CO+H2), psi Reaction, hr 24 3.1 (4.1) 2.9 (7.4) 107 6 6000 0.55 25 2.7 (5.4) 3.7(14.2) 91 6 7300 0.83 26 3.1 (3.7) 4.9(11.4) 83 6 7800 1.00 27 1.7 (3.7) 2.0 (8.4) 70 14 6000 0.45 28 2.7 (4.3) 3.2(10.6) 80 6 6000 0.67 29 2.9 (2.5) 4.1 (6.9) 76 7 4050 0.36 30 4.3 (5.9) 4.4(11.8) 76 16 6400 0.58 31 4.3 (5.8) 2.7 (9.4) 39 25 6000 0.76 32 3.1 (6.5) 2.4 (9.8) 78 11 6000 0.88 33 5.8 (8.0) 3.4 (9.2) 85 6 6150 0.58 34 3.0 (5.7) 2.6 (9.9) 92 5 6000 0.80 35 2.9 (5.5) 2.7 (9.8) 98 6 6000 0.77 36 0.35(3.5) 0.25(5.3) 19 36 4000 4.18 37 1.7 (3.8) 1.7 (7.3) 81 13 4000 0.95 38 2.0 (4.0) 1.7 (6.8) 78 17 4000 0.85 39 2.4 (6.3) 1.9 (9.8) 29 41 6000 1.08 40 2.0 (5.5) 1.7 (8.9) 44 16 6000 1.16 NOTES TO THE EXAMPLES: The following examples illustrate that a mixture of sulfolane and tetraglyme leads to a higher rate than does a pure solvent: 1-27 & 32-33.

The following examples illustrate that a mixture of sulfolane and tetraglyme leads to a higher rate than does either pure solvent: 1-6.

The following examples illustrate the increase in sulfolane content necessary to achieve good recovery of Rh with increasing temperature: 12-15 vs. 1-11 26-27 vs. 28-29 vs. 30-31, 32-33 vs. 34-35 vs. 36-38.

The following examples illustrate the increase in pressure necessary to achieve good recovery of Rh as temperature increases at constant solvent ratio: (1-15, 18,20) vs. 34-40 vs. 28-31.

Summary: Rh recovery, and hence rate to glycol, is determined by the three way interactive effect of solvent ratio, pressure, and temperature.

In order that the Rh remain in solution as the temperature is in creased, and consequently produce glycol at a higher rate, it is necessary that the sulfolane/tetraglyme ratio be increased or the "solvent ratio" be decreased; this is a more stringent necessity at lower pressure. As the temperature is increased, or pressure decreased, a point will be reached at which high recovery of Rh cannot be brought about by a change in solvent ratio.

Claims (15)

WHAT WE CLAIM IS:

1. A homogeneous liquid phase process of producing alkane polyols by the reaction of carbon monoxide with hydrogen in the presence of a rhodium catalyst in which rhodium is complexed with carbon monoxide to provide a rhodium carbonyl complex at a temperature between 100"C to 3750C and at a pressure between 500 psia to 50,000 psia, said reaction being effected in a solvent mixture of an amount of tetraglyme and a sulfolane, as hereinbefore defined, which under conditions whereby such solvent mixture is essentially inert, the rate of formation of such alkane polyol is greater than would be obtained by effecting said reaction under equal conditions using either tetraglyme or sulfolane as the solvent.

2. A process as claimed in claim 1 which is carried out at a pressure of 1,000 psia to 50,000 psia.

3. A process as claimed in claim 1 or 2 in which the ratio of tetraglyme to sulfolane is from 1 to 20 to 20 to 1 determined on a volume basis.

4. A process as claimed in claim 4 in which the sulfolane is substituted in the 3 or 3 and 4 positions of the sulfolane ring.

5. A process as claimed in any one of claims 1 to 4 in which the reaction mixture includes a reaction promoter which is a salt.

6. A process as claimed in claim 5 in which the salt is an ammonium salt or a salt of a metal of group I or II of the Periodic Table.

7. A process as claimed in claim 6 in which the salt is a cesium or ammonium carboxylate.

8. A process as claimed in claim 5, 6 or 7 in which the reaction pressure is 1,000 to 16,000 psia.

9. A process as claimed in claim 8 in which the reaction pressure is 4,000 to 16,000 psia.

10. A process as claimed in any one of claims 1 to 9 in which the reaction temperature is 1500 to 3200C.

11. A process as claimed in claim 10 in which the reaction temperature is 210 to 3000C.

12. A process as claimed in any one of claims 1 to 11 in which the ratio of CO:H2 in the reaction mixture is in the range from 10:1 to 1:10.

13. A process as claimed in claim 12 in which the ratio of CO:H2 is from 5:1 to 1:5.

14. A process as claimed in claim 1 and substantially as hereinbefore described with reference to any one of the Examples.

15. Alkane polyols whenever produced by a process as claimed in any one of claims 1 to 14.