CA1244478A - Ruthenium-promoted cobalt catalysts for the dealkoxyhydroxymethylation of acetals to form glycol ethers - Google Patents

Abstract

ABSTRACT

The ruthenium-cobalt carbonyl metal cluster catalyst Co2Ru(CO)11 effectively catalyzes the dealkoxyhydroxymethylation of aldehyde acetals to form glycol monoethers. Methylal, for example, may be reacted with syngas, i.e., CO and H2, in the presence of this ruthenium-cobalt cluster catalyst to form the monomethyl ether of ethylene glycol. Cycloalkyl and aryl-acetals, as well as alkyl-acetals of various aldehydes, as well as their aldehyde precursors, may likewise be reacted with syngas in the presence of this metal cluster to form the corresponding glycol monoether.

Description

4~7~3 BACKGROUND OF THE INVENTION

SCOPE OF THE INVENTION

This invention relatés to the dealkoxyhydroxymethylation of acetals.
More particularly, it relates to a novel process for the dealkoxyhydroxymethylation of certain dialkyl-, dicycloalkyl-, or diaryl-aldehyde acetals by reacting said ace~als with syngas, i.e., hydrogen and carbon monoxide, in the presence of a catalyst comprising a ruthenium carbonyl-promoted cobalt carbonyl metal cluster to form the corresponding glycol monoethers. The acetals described herein may be added directly or formed in situ from the corresponding aldehyde and slcohol precurors.

The glycol ethers described herein encompass known classes of compounds having various uses, as for example as jet fuel additives, cleaners, coatings solvents, intermediates in the production of certain diphthalates, and the like.

DESCRIPTION OF THE PRIOR ART

One current well-known method of manufacturing ethylene glycol monoethers such as monoalkyl ethers consists of reacting ethylene oxide with the alcohol corresponding to the desired alkyl ether, employing various known catalyst systems.

LS3l7A -2-1.2~'7~

Alternatively, the cobalt-catalyzed reaction of aldehydes or their dialkyl acetals with syngas, i.e., a carbon monoxide-hydrogen mixture, to form the corresponding glycol ether is also described in the art. Thus, for example, a method of making ethylene glycol ethers is described in U.S. Patent No. 2,525,793 which employs cobalt oxide to catalyze the reaction of methylal with syngas to provide a reaction mixture which, after hydrogenation over nickel, gives relatively uneconomical conversions on the order of 25-33~.

Numerous attempts have been made to obtain more practical yields of glycol ethers from aldehydes or their dialkylacetals. A number of promoters have been used in conjunction with various cobalt catalysts in an effort to improve reaction rates and product yields. ~.S.
Patent 4,062,898, for example, discloses a ruthenium chloride-promoted cobalt iodide catalyst which hydrocarbonylates formaldehyde dimethylacetal (methylal) to ethylene glycol monomethyl ether (EGMME) in yields of 10% or less. The reaction temperature required is 185C at 20 atm. or above. A second method, described in ~e~ Kokai Tokkyo Koho 81 83,432 (1981) uses substantial quantities of 2,4,6- collidine or similar aromatic amines to promote the cobalt carbonyl-catalyzed hydrocarbonylation of methylal in benzene as a solvent. The reaction of methylal with highly pressurized syngas in this process at 190C for 10 hours gave 44% selectivity to EGMME at 98% conversion. A further patent, Euro. Pat. Appln. EP 34,374 (1981) uses both iodine and triphenyl or tricyclohexylphosphine together with RuC13 H20 to promote the Co(Ac)2 4H20 - catalyzed hydrocarbonylation of methylal using 3000 psig of syngas, and temperatures of between 150 and 175C to obtain results nearly comparable to those of the Japanese.

More recently, Knifton has found that cobalt carbonyl promoted with a Group VIB donor ligand catslyzes the hydrocarbonylation of an aldehyde in an alcohol to make ethylene glycol monoethers; U.S. 4,308,403. Yields of ethylene glycol monobutyl ether ~EGMBE) as high as 61% were reported in this patent. A cyclopentadienyl-ligated cobalt catalyst is also effecti~e for these reactions giving glycol ethers in up to 54% yield;
U.S. 4,317,943.

Propylene glycol monoalkyl ethers are formed by contacting high pressure mixtures of carbon monoxide and hydrogen with either an acetal or an aldehyde and an alcohol using a cobalt catalyst promoted with a tin- or germanium-containing compound; U.S. 4,356,327. Yields o~ glycol ethers up to 31% were reported in this patent. Ethylene glycol ethers were also formed from a formaldehyde acetal or formaldehyde and an alcohol using tin or germanium promoters for cobalt carbonyl; U.S. 4,357,477. The highest glycol ether yield (EGMP,E) was 53~ in this case.

Further, propylene glycol monoalkyl ethers were formed by hydrocarbonylation of acetaldehyde acetals or acetaldehyde and alcohols usin~ rhodium, ruthenium or nickel compounds to promote either cobalt carbonyls or cobalt compounds having group V ligand systems attached.
Glycol ether yields up to 28% were realized when these promoters were used; Knifton, ~.S. 4,390,734 (1983).

~ ~14 4 47 ~3 Thus, the use of various promoters for the cobalt-catalyzed hydrocarbonylation of aldehydes or acetals has resulted in glycol ether yields of from 10-61%, depending on the glycol ether produced. The highest reported yield of EGMME is 44~, of EGMBE iB 61% and propylene glycol monethyl ether, PGMEE is 28~.

SU~M~RY OF THE INVENTION

In accordance with the present invention, there is provided an improved process for the reaction of certain dialkyl-, dicycloalkyl-, or diaryl-aldehyde acetals or their aldehyde-alcohol precursors with syngas in the presence of the ruthenium carbonyl-promoted cobalt carbonyl catalyst Co2Ru(CO)l1, to form the corresponding glycol monoethers. This reaction, which may best be described as the dealkoxyhydroxy~etbylation of an acetal formed separately or in situ by thP known reaction of ~n aldehyde with an alcohol, may be depicted by the following general reaction scheme.

LS317A _5_ : ` ' ~R1 ~ ORl R CH ~ CO ~ 2H2 ~ R CH ~ R2~H
oR2 \ CH20H
wherein R is selected from hydrogen, alkyl, cycloalkyl and aryl and Rl an~ R2, which may ~e the same or different, comprise any orgsnic moieties which are inert to the conditions of the reaction, and are selected from ~he groups consi~ting of: !

a) a straight or b~anched chain alkyl.group having from l to about 20 carbon atoms, such &S methyl, ethyl, propyl, i80propyl, n-butyl, t-butyl, 2-ethylhexyl, dodecyl, snd the like;

b) a substituted or unsubstituted cycloalkyl group having from 5 ~o ~bout 20 carbon atoms, æuch as cyclopeotyl, cyclohexyl, cycloheptyl, 3-methylcyclopentyl, 3-butyl cyclohexyl, cyclooctyl, adamantyl, decalyl, cyclooctyl, ada~antyl, decalyl, 3-phenylcycloheptyl ~od the like; and c) a substituted or unsubstituted aryl group having from 6 to about 20 c~rbon stom~ such ~s benzyl, phenyl, naphthyl, fluoroanthryl, tetralyl, tolyl, ethylphenyl, cumyl, ~nisyl, chlorophenyl, and the like.

It will be understood that when Rl and R2 in the foregoing reaction scheme are different, the resulting products will actually be mixtures of the corresponding ethers and alcohols. Also, as described in detail below, Rl and R2 may be joi~ed by one or more bridging atoms to form a cyclic compound.

This process, provides an improvement over the methods of the prior art in that the instant catalysts do not require the added presence of the iodide, amines, or phosphine promoters such as are dificlosed in the prior art, and thus is less costly and easier to prepare and recover.
Moreover, these novel catalysts permit the reaction to be carried out under more mild conditions of time and temperature than those of the prior art, yet most surprisingly provide rates and selectivities of desired product over those obtained by the use of cobalt carbonyl alone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
.

The novel homogenous catalyst of this invention consists of the metal cluster Co2Ru(CO)ll. This catalyst may be prepared by the method disclosed by Roland et al., Angew. Chem. Int. Ed. Engl., 20, 679 (1981).

The acetal dealkoxyhydroxymethylation reaction with syngas utilizing the ruthenium-cobalt carbonyl metal cluster catalyst may conveniently be conducted in a generally known manner whereby the desired acetal is reacted with syngas under elevated temperature and pressures for given periods of time, during which period the reaction mixture is efficiently stirred. In this reaction, the volume ratio of carbon monoxide to ~IL~ 78 hydrogen in the syngas desir~bly is in the range of ~rom about 1:3 to 3:1, and more preferably 1:2 to 2:1. Following rapid cooling, the reaction product is then recovered from the mixture in a routine manner.

In contrast to the prior art reaction conditions described above, the ruthenium-cobalt carbonyl metal cluster, Co2Ru~CO)ll, advantageously permits the use of mild operating conditions. Thus, tem~eratures in the range of from about 100 to 200C, snd preferably about 125 to 175C, pressures of from about 500 to 5000 psi, and preferably about 1000 to 3000 psi, may satisfactorily be employed.

The ratio of the weight of catalyst mixture e~ployed, to the weight of acetal, is desirably in the range of from about .001:0.1, and preferably .005:.05 in a batch reaction.

In a further embodiment of this invention, it has been found that highly advantageous effects may also be obtained in this dealkoxyhydroxymethylation process by the addition of solvents in combination with the catalyst system of this invention.

The solvents which may be advantageously used comprise any polar or non-polar organic solvents which are inert to the conditions of the reaction. lncluded amongst these solvents are C1 12 ~lcohols, prefersbly those corresponding to the alkyl group of the ~cetal, such as methanol, ethanol, butanol, 3-ethyl-2-hexanol and the like; ethers which will not cleave under the conditions of the reaction, such as glyme, diglyme, diphenyl ether and the like; aromatics and substituted aromatics such as ;2~

benzene, toluene, xylene, chlorobenzene, dichloroben2ene, anisole, and the like.

The solvents may constitute anywhere from O to 90 volume percent of the reaction mixture, and preferably 20 to 80 percent.

In still a further embodiment of this process, it has been found that when the reaction is carried out in an excess of an alcohol solvent, wherein the ratio of acetal to alcohol solvent is in the range of fro~
about 1:2 to 1:20, and preferably 1:5 to 1:10, and wherein the R group of the alcohol used is different than the R1 and/or R2 substituents on the acetal starting material, these different R groups of the alcohol will, in the course of the reaction, replace the Rl and/or R2 groups on the acetal in a substitution reaction, thereby resulting in a glycol monoether in which the R group of the ether moiety corresponds to the R
group of the alcohol solvent.

This reaction may be illustrated by the following equation:

oRl / OR~

RCH + ~0 + 2H2+R OH -~RCH + R OH ~ R20H
OR~ ~ H2H

wherein R, Rl, and R2 are as defined above, and R8 is a different alkyl, cycloalkyl, or aryl group than Rl and/or R2, and having from 1 to about 20 carbon atoms.

Depending upon the length of time the reaction is allowed to continue, intermediate mixtures of higher and lower molecular weight ~ubstituents on the acetal corresponding to both those of the Rl and/or R2 groups and those of the solvent will be found in the reaction mixture.

The acetal starting materials employed in this invention have the aforedescribed general formula, namely / OR
RCH

\ oR2 wherein R, Rl and R2 are as defined above. These acetals can be prepared in a known manner, separately or in situ, as for example as described in E.V. Dehmlav and J. Schmidt, ~etrahedron Letters, p.95-6 (1976) B.S. Bal and H.W. Pinnick, ~. Org. Chem. V44 (21), p. 3727-8(1979) D.W. Hall, ~.S.
Patent 3,492,356, Jan. 27 (1970), by the reaction of an aldehyde such as formaldehyde an alcohol, or mixture of alcohols, of the general formula RlON or R20H, where again R1 and R2 are as defined above, form the corresponding acetal. Hereinafter, when the acetal is referred to, it will be understood that the corresponding precursors, i.e., the desired aldehyde and alcohol, are also intended to be included.

`` ~2'~7~3 As also mentioned above, the R1 and R2 s~bstituents of the resulting acetal may be joined by one or more bridging atoms to form such cyclic compounds as ''---C~2 --CH~!~ ~ O---CH2 CH2 RCH I RC ~ ~ 2 O ~ CN ~ O - CH '` O - CH2 - CH2 ~ O--CH2~ 0--CX2~
RCH CX2, RC ~ CH2 ~ O CH ~ ~ O - CX2 ~
and the like, wherein R is as defined above, and X is selected from the group consisting of alkyl, aralkyl, aryl and cycloalkyl groups having from l to about 20 carbon atoms.

It is essential, in selecting the acetal starting material, that it not contain any substituents which are reactive under the conditions of the dealkoxyhydroxymethylation process of this invention. In other words, the R, R1 and R2 groups should not, for example, contain or comprise such reactive moieties as phosphine, arsine, amino, sulfido or carbonyl groups, acetal moieties, or olefins or acetylenic triple bonds. Other like groups will be recognized or readily determined by those skilled in the art as resulting in products other than the desired monoethers.

When, for example, formaldehyde acetals are dealkoxyhydroxymethylated with syngas in accordance with the process of this invention, there is obtained the corresponding ethylene glycol monoether in which the ether moiety will correspond to the organic moieties of the acetal starting material. Also formed ln lesser amounts is the trialkoxyethane of the general formula 7~

~ORl \ ORl , together with the alcohol R OH, which may be recycled to form additional acetal starting material. Again, as above, if the R groups of the acetal are differentt a mixture of corresponding R-substituted compounds will result.

As shown below, the selectivities for the desired monoether over the trialkoxy by-product are in the ratio of from about 3:1 to as much as 10:1 or more.

In a preferred embodiment of this invention, the starting materials are preferably symmetrical acetals where the R groups are lower alkyl groups of 1 to 4 carbon atoms, thereby forming the corresponding ethylene glycol mono-lower alkyl ethers such as the monomethyl ether, the monoethyl ether, the monobutyl ether, and the like.

Alternatively, the ~cetal may contain such Rl and R2 groups as naphthyl and phenyl. In the case of naphthyl, the reaction of the resulting formaldehyde acetal with syngas will provide 2-(2-naphthyloxy) ethanol, a known sedative, which in turn may be oxidized to the corresponding

2-naphthyloxyacetic acid, a plant growth hormone.

7~3 Likewise, the dealkoxyhydroxymethylation of the formaldehyde acetal, wherein R1 and ~2 are phenyl, will produce 2-phenoxy-ethanol, a topical antiseptic, which when oxidized, results in phenoxyacetic acid, a fungicide. Similarly, the formaldehyde scetal wherein Rl and R2 are 2, 4, 5-trichlorophenyl will yield, in accordance with this process, 2, 4, 5-trichlorophenoxyacetic acid, an herbicide. In a likt manner, when R1 and R are p-nonylphenyl p-nonylphenoxyacetic acid, a corrosion inhibitor and antifoaming agent in gasoline and cutting oils will be formed.

Each of these aforedescribed products may be recovered routinely by methods well known in the art.

The invention will now be illustrated by, but is not intended to be limited to, the following examples.

EXAMPI~S

Examples 1-~

A series of runs was carried out in which the following geDeral procedure was employed, using as the catalyst Co2Ru(CO)11 as well as mixtures of Co2(CO)8 and Ru3(CO)12, or Co2(CO)8 alone for comparative purposes:

To a 3~0 ml stainless steel autoclave equipped with a magnedrive stirrer was charged: methylal, solvent, and catalyst. Carbon monoxide and hydrogen were admitted and the reaction mixture was rapidly heated to the desired temperature. The mixture was stirred for the designated time at " ~Z'~7 !3 reaction temperature after which the reactor was cooled by immersion in an ice bath. When the contents reached 25C, the final pressure was recorded. After venting the gas, the liquid was analyzed by GLPC.

The results are reported in Table I below. The specific reaction conditions~ amounts, and solvent are as described in footnote la) in this table.

~ l~z~47~3 .o q~

d ~ c~ , o ~t oo o :~ ~Y;

~1 ~J
x ~

.,., ~ ~_ 3 r~ ~ D ,_ ~ o ~~: ~ X o ~ u~ ~ ~ ~ ~_ o w ~ ~ ~ .a qC~I
~ ,~ ~ ~
,, ~! ~ ~ D O ~ ~ C~
~ ~ r~ ~ o ~J
-- ^ ~ 0 4 _ ~'J C`l ~ ~ ~'1 ~ ~ o X C~ ~ D o ~`J ~ X
1: O ~ ,c~
~ _ :~ ~ d ~ ~ o ~ ~ ~ X o ~ ooooo~ o~o ~ + :~ ~
~ ~ ~ V
_ ~ o c~ ~ ~o v~
O ou~o~oo o ~ X~
P~ o a~ 0 0 11 11 ~_ r-1 ~o J u~
~ _. O
c~ o~ f3 ~ A c:
~O~ ~ O
_~ U~ U~ ~ ~ ~ o o O
C~

~1 ~ ~ ~ ~ ~ In ~ r~

~Z~47~3 Example 8 To a 110 ml. rocking autoclave are charged Co2Ru(CO)11, (0.75 ~oles);
methylal (70.6 mmoles); and o-dichlorobenzeneg (23.55 gms). After flushing thoroughly with 1/2 (CO:H2) syngas, 800 psig of C0 is admitted, then hydrogen to a total pressure of 2400 p6ig. The autoclave is rocked at 150C for 3 hours, then cooled, the product remoYed and analyzed by standardizing GLPC. A high yield of ethylene glycol monomethyl ether is obtained.

Example 9 Using the procedures of Example 8, but substituting diethoxymethane for methylal, a good yield of ethylene glycol monoethyl ether is obtained.

Example 10 Using the procedures of Example 8, but substituting dibutoxymethane for methylal, an excellent yield of ethylene glycol monobutyl ether is obtained.

Example 11 Using the procedures of Example 8, but substituting 0.4 ~moles of paraformaldehyde for methylal, and 25 grams of butanol for o-dichlorobenzene, a good yield of ethylene glycol monobuCyl ether is obtained.

3L2'~4478 E,xample 12 Using the procedure of example 8 but substituting diethoxyethane for methylal, propylene glycol monoethyl ether is the major reaction product.

Example 13 To a 110 ml. rocking autoclave is charged Co2Ru(C0)11 (0.75 mmoles~;
methylal (27 mmole), butanol (18.5 ml.), and mesitylene as an internal standard. Carbon monoxide, 800 psig, is added and hydrogen added to a total pressure of 3200 psig. The mixture is rocked at 150C for six hours, cooled and analyzed by standardized glpc. A good yield of the monobutylether of ethylene glycol is produced.

Claims (14)

What we claim is:

1. Process for the dealkoxyhydroxymethylation of an aldehyde acetal of the formula wherein R is selected from hydrogen, alkyl, cycloalkyl and aryl and R1 and R2, which may be same or different, are selected from the group consisting of alkyl, cycloalkyl, and aryl moieties having from 1 to about 20 carbon atoms, and wherein R1 and R2, taken together, may be joined by one or more bridging atoms to form a cyclic acetal, which comprises reacting said acetal, which has been formed separately or in situ, with syngas in the presence of a catalytically effective amount of a catalyst comprising the complex Co2Ru(CO)11 to form the corresponding glycol monoether.

2. Process of claim 1 wherein the temperature is in the range of from about 100 to 200°C.

3. Process of claim 1 wherein the pressure is in the range of from about 500 to 5000 psi.

4. Process of claim 1 further comprising carrying out the reaction in the presence of an inert organic solvent.

5. Process of claim 4 wherein the inert organic solvent is a chlorinated aromatic solvent.

6. Process of claim 5 wherein the chlorinated aromatic solvent is chlorobenzene or dichlorobenzene.

7. Process of claim 1 wherein R1 and R2 are alkyl groups having from 1 to about 20 carbon atoms.

8. Process of claim 7 wherein the alkyl groups are lower alkyl.

9. Process of claim 1 wherein the weight ratio of catalyst to acetal is in the range of from about .001 to 0.1.

10. Process of claim 1 wherein R is hydrogen, and the product is an ethylene glycol monoether.

11. Process of claim 1 wherein R is methyl, and the product is a propylene glycol monoether.

12. Process of claim 1 wherein R is ethyl, and the product is a butylene glycol monoether.

13. Process of claim 1 further comprising carrying out the reaction in the presence of an excess of an alcohol solvent of the formula wherein R8 is an alkyl, cycloalkyl, or aryl group having from 1 to about 20 carbon atoms, and wherein R8 is different than either the R1 or R2 group of the acetal starting material, or both, to form a glycol ether of the formula wherein R8 is as defined above.

14. The process of claim 13 wherein R8 is lower alkyl.