NO824396L - PROCEDURE FOR HYDROGENOLYSE OF CARBOXYLIC ACID ESTES. - Google Patents

Description

This invention relates to the hydrogenolysis of carboxylic acid esters.

Hydrogenolysis of carboxylic acid esters is described in a number of places in the literature. Typical of such a reaction is that the -G0-0 link in the ester group is split so that the acid part of the ester group is reduced to an alcohol, while the alcohol part is released as free alcohol according to the following equation:

where R, and each are, for example, alkyl radicals.

According to page 129 onwards in the book "Catalytic Hydro-genation in Organic Synthesis" by M. Freifelden, published by John

■Wiley and Sons Inc; (1978), is the chosen catalyst for this . reaction indicated to be barium-activated copper chromite. Typical reaction conditions include the use of temperatures in the range from 250°C and pressures in the range of 225-250 atmospheres (about 22.81 MPa to about 25.35 MPa). Although a good yield of alcohol is often obtained during, application of this technique for

hydrogenolysis of an ester, the temperature required will

for conversion of the ester to alcohol, could also lead to side reactions. For example, the resulting alcohol may undergo further hydrogenolysis to hydrocarbon or may react with starting material to form a high molecular weight ester that is more difficult to hydrogenolyse.

Besides these side reactions, copper-chromite catalysts suffer other disadvantages when operating on a commercial scale. In particular, the use of copper chromite catalysts is environmentally harmful and necessitates the use of special and expensive handling methods due to the toxicity of chromium. Furthermore, it is difficult to produce successive portions of copper chromite with reproducible catalyst activity.

US patent 2079414 describes a method for the catalytic hydrogenation of esters using such catalysts as molten copper oxide, either fully or partially reduced, which can be activated with oxide activators such as manganese oxide, zinc oxide, magnesium oxide or chromium oxide. Particularly recommended catalysts are those comprising copper oxide activated with chromium oxide, e.g. copper chromite. According to page 3, right column from line 57: "When operating in the vapor phase, it is preferred to use temperatures in the range from 300°C to 400°C". It is also stated that: "The best conversions to alcohols are achieved at the highest pressures that can be achieved in the available equipment and at the lowest temperatures that can be reconciled with achieving a practical reaction rate" (page 4, right column, from line 2). The examples describe batch reactions, and in all cases

the pressure is 2500 psia or higher (17250 kPa or higher), while the temperature is in all cases 250°C or higher; in most : cases it exceeds 300°C. A limitation of the method is that methyl esters cannot be used, because methanol, which would be a hydrogenation product from a methyl ester, is subject to gas decomposition (see page 5, right column, from line 5.8). -Similar considerations also seem to prevent the application of the method to esters of formic acid, since the formic acid part

will also tend to form.methanol.

Further description of the use of chromites as catalysts for the hydrogenation of esters can be found in US patent 2109844

Example 4 in US patent 3197418 describes - production of

a copper-zinc catalyst that can be used in liquid-phase hydrogenation of oils and fats at pressures above 120 kg/cm2

(11776 kPa) and at a temperature of 320°C.

US patent 2241417 describes the preparation of higher aliphatics. alcohols by liquid phase hydrogenation of glycerides' in the presence of copper-containing catalysts at a temperature from 200°C to 400°C and pressure from 60 to 500 atmospheres (5884 to 49033 kPa).

Hydrogenolysis of esters to saturated hydrocarbons, using catalysts which have as essential constituents an indium or rhodium component and a halogen component, is described in US patent 4067900.

Catalytic hydrogenolysis of formate esters present

in oxo reaction products using Ni catalysts,

is described in East German patent 92440 (see Chem. Abs.., 124069j , vol. 78 (1973), page 439). Other references to hydrogenation

of formate includes an article by E. Lederle, Anales Real

Soc. Spain. Fart. y Quim. (Madrid) 57B., pp. 473-5 (1961). Also West German patent 902375 describes the production of methanol by hydrogenation of alkyl formates at pressures from 20 to 50 atmospheres (1961 to 4903 kPa) using copper chromite catalysts; and there is a faint suggestion that zinc oxide may be incorporated into the catalyst.

Catalytic cleavage of formic acid esters is described in British patent 1277077. According to this proposal, a hydrogenation catalyst containing copper and nickel is used, but it is stated that the formyl radical is dehydrogenated during the reaction and appears as carbon monoxide.

The production of ethylene glycol by hydrogenolysis is proposed in some places, including US Patent 4113662, which describes the hydrogenation of esters to alcohols at temperatures from 150°C to 450°C and pressures of 500-10,000 psig (3450-69000 kPa) using catalysts which includes cobalt, zinc and copper. Examples IV, V and VIII describe comparative experiments using polyglycolide and methylglycolate with Cu-Zn oxides as catalyst at 250°C and at a pressure of at least 2800 psig (19421 kPa), i.e. conditions under which the ester (polyglycolide or methylglycolate) is in liquid state. US Patent 2305104

describes the hydrogenation of alkyl glycolates using catalysts containing Zn, Cr and Cu to form ethylene glycol. Vapor phase hydrogenation of oxalate esters at temperatures from 150°C to 300°C for the production of ethylene glycol is described in US patent 4112145; and in this method one copper chromite or copper-zinc chromite catalyst is used,

and the oxalate ester is required to have a sulfur content of less than 0.4 ppm.

It would be desirable to find a method for carrying out the hydrogenolysis of esters with insignificant formation of by-products or of heavier components ("heavies"), which can be carried out under mild conditions.

It would also be desirable to provide a method for carrying out the hydrogenolysis of formate esters and of methyl esters without significant degradation of the methanol product during the course of the reaction.

It would also be desirable to provide a hydrogenolysis process using a simple catalyst that can be produced with reproducible catalyst activity.

The present invention thus aims to provide an improved method for carrying out the hydrogenolysis of esters, which can be carried out under mild conditions. ..The invention further aims to provide a method for carrying out the hydrogenolysis of formate esters, for

■ to give high yields of methanol at high conversions.

It also aims to provide a method, for

•production of ethanol by hydrogenolysis of acetate esters with

■high yield and at high conversions under mild conditions.

Furthermore, the invention aims to provide an improved method for the production of ethylene glycol by

starting with oxalic acid esters or from glycolic acid esters using catalytic hydrogenolysis under mild conditions.

The invention also aims at providing new hydrogenolysis routes to diols such as ethylene glycol, 1,2-propanediol, 1,4-butanediol and 1,6-hexanediol, by starting from diesters of dicarboxylic acids or monoesters of hydroxycarboxylic acids.

Furthermore, the invention aims to provide a method for producing hydrogenolysis of methyl esters and of formate esters under mild conditions, so that cleavage of

significant amounts of methanol product are essentially avoided under the reaction conditions used.

It is also an object of the invention to provide an improved process for the production of 1,4-butanediol by hydrogenolysis of butyrolactone.

According to the present invention is provided

a process for the production of hydrogenolysis of a

■carboxylic acid ester, which comprises bringing a vaporous mixture containing the ester and hydrogen into contact with a catalyst

sator which comprises a reduced mixture of copper oxide and zinc oxide at a temperature in the range from approx. 75°C up to approx. 3.00°C

2

and at a pressure in the range from.ca. 0.1 kg/cm absolute (approx. 9.8 kPa) up to approx. 100 kg/cm absolute (approx. 9813.kPa).

The ester can be virtually any volatile ester. Among esters which may be mentioned are the esters of mono-, di- and polycarboxylic acids which may be derived from mono-, di- or polyols.

Examples of suitable esters include those having the general formula: ■ as well as those having the general formula:

In the above general examples, n and p each mean a whole number, preferably one. whole number from 1 to approx. 5, e.g. 1, 2 or 3, and R, R', R" and R'" each mean an optionally substituted, saturated or unsaturated, cyclic or acyclic hydrocarbon radical, where one or more carbon atoms can be replaced by heteroatoms such as nitrogen , oxygen or phosphorus. ■ Examples of possible substituents on the radicals R, R1 , R" and R 1,1 include oxygen atoms as well as hydroxy and alkoxy groups. Preferably R, R', R" and R1" each contain from 1 to about . 12 carbon atoms. Typically, R, R', R" and R are selected from alkyl-, alkenyl-, alkoxyalkyl-, hydroxyalkyl-, aryl-, aralkyl-, alkyl-aryl-, alkoxyaryl-, hydroxyaryl-, cycloalkyl- , alkylcycloalkyl, alkoxycycloalkyl, hydroxycycloalkyl and cycloalkyl-alkyl radicals.

Such esters may be derived from the following acids:

formic acid,

acetic acid,

propionic acid,

n- and iso-butyric acid,

n- and iso-valeric acid,

caproic acid,

caprylic acid, capric acid, 2-ethylhexanoic acid,

glycolic acid,

pyruvic acid, cyclohexane-carboxylic acid,

benzoic acid,

o-, m- and p-toluene acid,•

o-, m- and p-methoxybenzoic acid,

naphtho-2-oic acid,

cinnamic acid,

oxalic acid, malonic acid,

succinic acid,

glutaric acid,

adipic acid,

maleic acid

fumaric acid, acrylic acid,

'methacrylic acid, α- or 3-crotonic acid, acetylene dicarboxylic acid,

methoxyacetic acid,

f eny acetic acid,

vanillic acid, terephthalic acid,

o-salicylic acid,

lactic acid,

citric acid, Y-hydroxybutyric acid, furancarboxylic acid, and the like.

Preferably, the acid contains from 1 to approx. 12 carbon • atoms.

Suitable mono-, di- or poly parts can be selected from:

methanol,

ethanol,

n- or iso-propanol,

n-, iso-, sec- or t-butanol,

pentan-1- or -2-ol,

.2-methyl-butan-2-, -3- or -4-ol,

hexariols, heptanols,

octanols (e.g. 2-ethylhexanol), cetyl alcohol, lauryl alcohol, furfuryl alcohol, ethylene glycol, 1,2- or 1,3-propylene glycol,

1,4-butanediol, • 1, 6-hexahdiol, glycerol, allyl alcohol,

vinyl alcohol,

phenol,

o-, m- or p- cresol, benzyl alcohol,

phenylethyl alcohol,

ethylene glycol monomethyl ether,

ethylene glycol monoethyl ether, cyclohexanol,

mono-, di- and tri-ethanolamine, and the like.

Preferably, the mono-, di- or polyol does not contain more than approx. 12 carbon atoms.

As examples of special esters can be mentioned: alkyl formates (eg methyl-, ethyl-, n- and iso-propyl, n-, iso-, sec- and t-butyl formates);

alkyl acetates (eg methyl, ethyl, n- and iso-propyl, and ri-, iso-, sec- and t-butyl acetates);

cycloalkyl acetates (eg cyclohexyl acetate);

alkyl propionates (eg n-propyl propionate);

alkyl-n-butyrates (eg, n-buty1-n-butyrate);

alkyl isobutyrates (eg, isobutyl isobutyrate);

alkyl n-valerates (eg n-amyl valerate);

alkyl iso-valerates (eg methyl iso-valerate);

alkyl caproates (eg ethyl caproate); alkyl caprylates (eg methyl caprylate);

alkyl caprates (eg ethyl caprate);

alkyl 2-ethylhexanoates (eg 2-ethylhexyl-2-ethylhexanoate);

vinyl acetate;

allyl acetate j

alkyl alkoxy acetates (eg methyl methoxy acetate);

alkyl glycolates (eg methyl and ethyl glycolates);

dialkyl oxalates (eg, dimethyl, diethyl and di-n-butyl oxalates);

dialkyl succinates (eg dimethyl and diethyl succinates);

dialkyl adipates (eg, dimethyl and diethyl adipates);

ethylene glycol mono- and di-carboxylates (eg ethylene glycol diformate, • ethylene glycol mono- and di-acetates, ethylene glycol di-n-butyrate, ethylene oxalate, ethylene glycol glycolate);

monocarboxylic acid esters of furfuryl alcohol (eg, furfuryl acetate);

alkyl esters of aromatic acids (e.g. methyl benzoate,

' ethyl benzoate, methyl o-toluate, methyl naphth-2-oate, methyl phenyl acetate, ethyl phenyl acetate);

phenyl esters of monocarboxylic acids (eg, phenyl acetate);

benzyl esters of monocarboxylic acids (eg benzyl acetate);

dialkyl maleates (eg, dimethyl maleate, diethyl maleate);

dialkyl fumarates (eg, dimethyl fumarate, diethyl fumarate); dialkyl esters of acetylene dicarboxylic acid (eg, dimethyl acetylene dicarboxylate);

dialkyl malonates (eg diethyl malonate); . alkyl glycolates' (eg methyl glycolate, ethyl glycolate);

alkyl lactates (eg, ethyl lactate);

alkylpyruvates (eg, ethylpyruvate);

alkyl cyclohexane carboxylates (eg methyl cyclohexane carboxylate);

lactones (eg Y_butyrolactone); and such.

The vaporous mixture which is to be brought into contact with the catalyst in the method according to the invention contains, in addition to the ester, hydrogen either alone or mixed with other gases (preferably gases which are inert to the ester and the catalyst). The gaseous mixtures containing hydrogen include inert gases such as nitrogen or carbon monoxide.

The term "hydrogen-containing gas" as used here includes both approximately pure hydrogen gas and gaseous mixtures containing hydrogen.

The hydrogenolysis process according to the present invention is carried out at eh temperature between approx. 75°C and approx. 300°C, although in many cases the preferred temperature can lie in the range from approx. 150 C to approx. 200 C, e.g. with alkyl formates, and in most cases it is typically between approx. 180°C and approx. 240°C. In some cases, a lower range may be preferred; for example with t-butyl formate, the preferred temperature range is from approx. 130°C to approx. 190°C. The total pressure is between approx. 0.1 kg/cm absolute (approx. 9.8 kPa) and approx. 100 kg/cm absolute (approx. 9813 kPa), preferably no more than approx. 50 kg/cm 2absolute (approx. 4906 kPa),

2

and even more preferably between approx. 5 kg/cm absolute

(approx. 491 kPa) and approx. 25 kg/cm<2>absolute (approx. 2453 kPa).

The mixture of CuO and ZnO, before reduction, preferably contains from approx. 5 to approx. 95% by weight, typically from approx. 10 to approx.

70% by weight, CuO and from approx. 95 to approx. 5% by weight, typically from approx.

90 to approx. 30 wt% ZnO. The mixture can thus, for example, contain from approx. 20 to approx. 40% by weight CuO and from approx. 60 to approx. 80% by weight ZnO-. A preferred mixture contains, for example, from approx. 30 tii approx. 36% by weight CuO and from approx. 62 to approx. 68 wt% ZnO. Other particularly preferred mixtures comprise from approx. 65 to approx. 85% by weight CuO and from approx. 35 to approx. 15% by weight ZnO, for example mixtures, containing from approx. 68 to approx. 75% by weight CuO and from approx. 32 to approx. 25 wt% ZnO. The hydrogenolysis catalyst may contain smaller amounts of other materials such as carbon, sodium, titanium, zirconium, manganese, silicon dioxide, diatomaceous soil, diatomaceous earth and aluminum oxide. Such other materials usually do not comprise more than approx. 20% by weight calculated (except for carbon) as oxide. As for sodium, it's the best that it does not exceed approx.' 0.5 by weight, calculated as oxide.

Other preferred catalysts thus include mixtures containing from approx. 40 to approx. 50% by weight of each of CuO and ZnO and from 0 to approx. 20% by weight aluminum oxide. However, the catalyst is preferably substantially free of other metals, in particular of metals of group VIII in the periodic table such as Fe, Cd., Ni, Ru, Rh, Pd, Os, Ir and Pt, as well as metals from group VIB such as Cr, Mo and W,, the metals Tc, Ag, Re, Au and Cd, and also'elements with atomic number 80 and higher, e.g. Hg and Pb. The term "almost free" is to be understood as meaning that the catalyst does not contain more than approx. 0.1% by weight (ie no more than approx. 1000 ppm), and preferably no more than approx. 250 ppm, of the element in question. The catalyst can be prepared by any of the methods known in the art for preparing a composite body of copper oxide and zinc oxide. The catalyst can be prepared by fixing the separate oxides, by co-precipitation of the oxalates, nitrates, carbonates or acetates, followed by calcination. The coprecipitation method is preferred. In general, the mixture of CuO and ZnO is reduced with hydrogen or carbon monoxide at a temperature in the range between approx. 160°C

and approx.: 250°C for several hours, preferably for 8 to 24 hours, before bringing it into contact with the vaporous mixture containing

ester and hydrogen." If the catalyst is used in a pre-reduced form, the time required for reduction can be reduced accordingly.

The mixture of CuO and ZnO is reduced before it is used as a catalyst in the hydrogenolysis step. Hydrogen or CO, or mixtures thereof, are generally mixed with a diluting gas such as steam, nitrogen or combustion gas, to maintain the temperature in the catalyst layer and to remove heat of reduction.

Reduction of the mixture of CuO and ZnO is complete when no more hydrogen or carbon monoxide reacts, as shown by analysis of the inlet and outlet gas. When hydrogen is used, the mixture is completely reduced when the total amount of water formed during the reduction is equal to the stoichiometric amount of water that would be formed when a given amount of copper oxide is reduced to copper. This value is approx. 0.079 kg of water per kg of catalyst for a mixture containing 35% by weight of CuO.

An inert support material can be incorporated into the catalyst mixture for hydrogenolysis. The catalyst is generally formed into pellets, tablets or any other suitable form before use by conventional methods.

It is appropriate that the mixtures of CuO and ZnO have a

2 internal, surface area of from approx. 25- to approx. 50 m per gram. The internal surface area can be determined by the well-known BET method.

The method according to the invention is most conveniently carried out in a continuous manner, although semi-continuous or batch operation can also be used. In the preferred method of continuous operation, an ester or a mixture of esters, a hydrogen-containing gas and possibly a carrier gas such as nitrogen can be brought together and brought into contact under the desired pressure in . vapor phase with the catalyst. The reaction zone is suitably an elongated, tubular reactor where the catalyst is placed.

In the hydrogenolysis process according to the invention, the primary reaction observed with many esters is that indicated in equation (I) above. A monocarboxylic acid ester gives then-, in this case, a mixture of alcohols, one derived from the carboxylic acid part and one derived from the alcohol part. Esters of dicarboxylic acids and those derived from polyols give di- and polyols, respectively. Thus, for example, dialkyl oxalates ..ethylene glycol and the corresponding alkyl alcohol. However, in some cases the products include hydrocarbons derived either from the carboxylic acid moiety or from the alcohol moiety or from both. Probably the alcohols are formed first, but they are then rapidly hydrogenated to the corresponding hydrocarbon, under the reaction conditions used. Under normal operating conditions, alcohols are the main products when alkyl esters of aliphatic acids are used as starting materials. However, when esters of aromatic acids, such as benzoic acid, or of aromatic alcohols, such as benzyl alcohol, are used, the main product derived is from the aromatic acid part, or from the aromatic alcohol part, as the case may be fits, usually the corresponding hydrocarbon.

An alcohol that is formed as a primary product can in some cases undergo further reaction. For example, hydrogenolysis can. of diethyl maleate or of diethyl succinate do not give 1,4-butanediol as one might expect as the primary product, but tetrahydrofuran. In hydrogenolysis of t-butyl acetate, the observed products contain not only t-butyl alcohol, but also isobutene, probably formed by dehydration of t-butanol under the reaction conditions used.

The alcohol and/or hydrocarbon product or products (if they can be liquefied) from the hydrogenolysis reaction can be separated from the hydrogen by condensation, and excess hydrogen can be compressed and returned to the reaction zone. The crude alcohol or hydrocarbon product can be used in this form. or can be further purified in the usual way such as by fractional distillation. Optionally, any unconverted portion of the ester or ester mixture can be separated from the reaction product and returned to the reaction zone and preferably mixed with fresh feed gases before introduction into the reaction zone.

When carrying out the method according to the invention, the partial pressure of the ester can vary within wide limits, e.g. from approx. 0.05 kg/cm 2 (4.9 kPa) or less up to approx. 10 kg/cm<2>(981 kPa) or more. Care must be taken, however, that the temperature of the vapor mixture in contact with the catalyst is at all times above the dew point of the ester under the prevailing pressure conditions.

The vaporous mixture preferably contains at least an amount of hydrogen corresponding to the stoichiometric amount of hydrogen required for hydrogenolysis. Usually, an excess of hydrogen in relation to the stoichiometric quantity will be present. In this case, excess hydrogen that remains after recycling the product can be recycled to the catalytic reaction zone. As will be apparent from equation (I) above, 2 moles of hydrogen are required for hydrogenolysis of each carboxylic acid ester group present in the ester molecule. If the ester contains non-aromatic unsaturation (e.g. carbon-carbon double or triple bonds), such unsaturated bonds may also undergo hydrogenation under the hydrogenolysis conditions used. The stoichiometric quantity of hydrogen which is necessary for the reduction of 1 mol of an unsaturated mono-ester can thus correspond to 3, 4 or more mols of hydrogen.

Diesters require 4 moles of hydrogen per mole diester, if it is -saturated, for hydrogenolysis; non-aromatic, unsaturated diesters may require 5 or more moles of hydrogen for the hydrogenolysis of 1 mole of diester. Triesters and higher polyesters will require 6 or more moles of hydrogen, depending on the number of ester groups and non-aromatic unsaturated bonds, per moles for hydrogenolysis.

The molar ratio hydrogen:ester in the vaporous mixture can vary within wide limits, e.g. from approx. 2:1 to approx. 100:1' or more for a monoester or from approx. 4:1 to approx. 100:1 or more for a diester. This ratio will depend, at least to a certain extent, on the volatility, on the ester used as well as on the number of ester groups in the ester material to be reduced. Typically, the hydrogen:ester molar ratio is at least approx. 25:1. -.

Although the method according to the invention can be applied to carboxylic acid esters in general, the best results are obtained with esters which boil at temperatures of no more than about 300°C at atmospheric pressure. Although it is possible to use esters which have even higher boiling point, the use of higher-boiling materials will limit the partial pressure of the ester that can be used in the vaporous mixture and thus limit the rate of hydrogenolysis. If very high-boiling esters are used,

• the extent of the reaction will be reduced accordingly.

Certain esters can undergo thermal decomposition at temperatures up to 300°C and possibly at temperatures below their boiling point at atmospheric pressure. When such esters are used, the temperature during the hydrogenolysis should not be so high that any significant thermal decomposition of the ester takes place.

In general, it is preferred to use monocarboxylic acid esters, preferably aliphatic monocarboxylic acid esters of aliphatic alcohols, containing from 2 to approx. 20 carbon atoms, or dicarboxylic acid diesters, preferably aliphatic dicarboxylic acid diesters, containing from 4 to approx. 16 carbon atoms..

According to a particularly preferred embodiment of the invention, a method for the production of ethylene glycol is provided, which comprises hydrogenolysis of an oxalic acid ester by bringing a vaporous mixture containing the ester and hydrogen into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide .at a temperature in the range from approx.'75°C up to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm 2 absolute (approx. 9.8 kPa) up

2

to approx. 100 kg/cm absolute (about 9813 kPa), and the resulting ethylene glycol is recovered. In the hydrogenolysis of oxalic acid esters, it is preferred to use temperatures from approx. 180°C to about 240°C; and preferred working pressure varies from approx. 5 kg/cm2 absolute (approx. 491 kPa) up to approx. 35 kg/cm<2>absolute (about 3435 kPa) .

According to another preferred embodiment of the invention, a method for the production of methanol is provided, which comprises hydrogenolysis of a formic acid ester by bringing a vaporous mixture containing the ester and hydrogen into contact with one catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm 2 absolute (approx. 9.8 kPa) up to approx. 100 kg/cm<2>absolute (about 9813 kPa), and the resulting methanol is recovered.

In the hydrogenolysis of formic acid esters. for the production of methanol

■the temperature preferably varies from approx. 130°C to approx. 220°C, e.g. from approx. 150°C to approx. 190°C, and the pressure preferably varies from approx. 5 kg/cm<2>absolute (approx. 491 kPa) to approx. 35 kg/

2

cm absolute (approx. 3435 kPa). ■

According to a further embodiment of the present invention, a method for the production of ethanol is provided, which comprises hydrogenolysis of an acetic acid. ester in that a vaporous mixture containing the ester and hydrogen is brought into contact with a 'catalyst' comprising a reduced mixture of copper oxide and zinc oxide at a temperature in the range from about 75°C up to about 300°C and at a pressure in the range from approx. 0.1 kg/cm2absolute (approx. 9.8 kPa) up to approx.

100 kg/cm 2 absolute (about 9813 kPa), and the resulting ethanol is recovered. In the hydrogenolysis of acetic acid esters for the production of ethanol, the temperature varies from approx. 180°C to approx. 240°C

2

and the pressure from approx. 5 kg/cm absolute (approx. 491 kPa) to approx.

2

35 kg/cm absolute (approx. 34 3 5 kPa) .

The invention further provides a method for the production of 1,4-butanediol and/or tetrahydrofuran, which comprises carrying out hydrogenolysis of an ester of an acid selected from maleic acid, fumaric acid, acetylene dicarboxylic acid and succinic acid, in that a vaporous mixture containing the ester and hydrogen is brought into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide at a temperature in the range from approx. 75°C to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm2 - absolute (approx. 9.8 kPa) up to approx. 100 kg/cm 2 absolute (about 9813 kPa), and the resulting 1,4-butanediol and/or tetrahydrofuran is recovered. When producing 1,4-butanediol and/or tetrahydrofuran by such a method, it is preferred that the temperature is between approx. 180°C and approx. 240°C, while the preferred pressure range is from approx. 5 kg/cm 2 absolute (approx. 491 kPa) up to approx. 35 kg/cm 2absolute (approx. 3435 kPa).

According to the invention, a method for the production of ethylene glycol is also provided, which comprises carrying out hydrogenolysis of a glycol acid ester by bringing a vaporous mixture containing the ester and hydrogen into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide at a temperature in - the area from approx. 75°C up to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm absolute (approx. 9.8 kPa) up to approx. 100 kg/cm 2 absolute (approx. 9813 kPa), and the resulting ethylene glycol is recovered. In the hydrogenolysis of glycolic acid esters for the production of ethylene glycol, it is preferred to work with from approx. 180°C to approx. 240°C and applying pressure from approx. 5 kg/cm<2>absol' utt (approx. 491 kPa) up to approx. 35 kg/cm<2>absolute (approx. 3435 kPa). Furthermore, one method for the production of 1,4-butanediol is provided, which comprises hydrogenolysis of butyrolactone by bringing a vaporous mixture containing butyrolactone and hydrogen into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300°C and at

2

pressure in the area from approx. 0.1 kg/cm absolute (approx. 9.8 kPa) up

2

to approx. 100 kg/cm absolute (about 9813 kPa), and the resulting 1,4-butanediol is recovered. In the hydrogenolysis of butyrolactone, it is preferred to use a temperature in the range from approx. 180°C to approx. 240°C and a pressure in the range from approx. 5 kg/cm- absolute (approx. 491 kPa) up to approx. 45'kg/cm 2 absolute (about 4416 kPa).

The best yields of 1,4-butanediol are generally obtained towards the higher part of the pressure range, for example when the pressure is in the range from approx. 25 kg/cm 2 absolute (approx. 2453 kPa) up to approx.

2

45 kg/cm absolute (approx. 4416 kPa).

In each case, recovery of the hydrogenolysis products can be carried out in the usual way, e.g. by condensation, possibly followed by fractional distillation under normal, reduced or elevated pressure.

The invention will be further illustrated in the following. examples.•

Example. 1

n-Butyl butyrate was pumped at a rate of 3.8 ml/hour more

an electrically heated gas/liquid mixing device to which hydrogen was also supplied at a controlled rate and pressure. It

resulting vaporous mixture was passed through an insulated, electrically heated line to a preheated coil before being passed through a tubular reactor packed with 146 ml of a powdered catalyst; • Both the tubular reactor and pre-heating coil were immersed in a molten salt bath heated to 174°C. The vaporous mixture exiting the reactor was passed through a water-cooled cooler, and the resulting condensate was collected in a water-cooled collection device. The outlet gas pressure was regulated to

10.55 kg/cm 2absolute (1035 kPa). The non-condensable gases were then passed through a downward valve, the gas flow rate being monitored downstream from this valve in a wet gas meter. A gas flow rate of 46.4 liters/hour (measured at atmospheric pressure) was maintained. during the experiment.

The liquid condensate was analyzed by gas chromatography using a 2 meter stainless steel column (6 mm outer diameter) packed with polyethylene glycol (nominal molecular weight 20,000) on "Chromosorb PAW", a helium gas flow rate of 30 ml/minute and a flame ionization detector. The instrument was equipped with a chart recorder with a peak integrator and was calibrated using a mixture of n-butanol and n-butyl butyrate of known composition. The condensate was shown to contain a mixture of 99.62 wt% butanol and 0.28 wt% n-butyl butyrate, corresponding to a 99.7% conversion with near-100% selectivity.

The catalyst used in this example was introduced into the reactor as a co-precipitated mixture of CuO and ZnO containing 33+3% CuO and 65±3% ZnO with a particle size in the range 1.2 mm to 2.4 mm and an internal surface area of approx. 45 m<2>

per gram. It was pre-reduced in the reactor using a 5 volume l H 2 in N 2 gas mixture at 200°C for 17 hours followed by pure hydrogen at 200°C for 8 hours, the gas flow rate in each case being approx. 20 litres/hour (measured at atmospheric pressure using the wet gas meter), and gas-

the pressure was 10.55 kg/cm absolute (1035 kPa). After this preliminary reduction, the catalyst was kept in a hydrogen-containing atmosphere at all times.

Example. 2

The procedure in Example 1 was repeated during use

of ethyl acetate instead of n-butyl butyrate, at a feed rate of 7.4 ml/hour and a hydrogen flow rate of

41.9 litres/hour (measured at atmospheric pressure using the wet gas meter) . In this experiment, the salt bath temperature was 185°C, and

2 outlet gas pressure was 10.55 kg/cm absolute (1035 kPa). The liquid condensate was shown to contain a minor amount of ethyl acetate, a major amount of ethanol and traces of n-butanol. The observed conversion of ethanol was 97.1%, and the selectivity of

ethanol was approx. 95%.

Example 3

When the method according to example 2 was repeated at a salt bath temperature of 203°C, with a gas flow rate of

160.4 litres/hour and a flow rate for supplied liquid

(ethyl acetate) of 34.8 ral/hour, with both ethyl acetate and ethanol identified in the liquid condensate, but essentially no n-butanol was formed. The conversion of the ester was

.82.6%, and the selectivity to ethanol was approx. 100%

Example 4

The procedure of Example 1 was repeated using isopropyl formate, which was fed at a rate of 23.4 ml/hour, and. a gas flow rate of 35.1 liters/hour (as measured at atmospheric pressure with the wet gas meter). The salt bath temperature was 185°C, and the outlet gas pressure was 10.55 kg/cm<2>absolute (1035 kPa). The liquid condensate was analyzed and. shown to contain as main components, besides smaller trace amounts of acetone and butanol, methanol and isopropyl alcohol. The conversion of the ester starting material was approximately 100%, and the selectivity to methanol was approx. 99%.

Example 5

The procedure of Example 1 was repeated using methyl acetate instead of n-butyl butyrate at a flow rate of 75 ml/hour and a hydrogen flow rate of 115.2 liters/hour (measured at atmospheric pressure). In this experiment, the salt bath temperature was 194°C, and the outlet gas pressure was

2 .9.49 kg/cm absolute (935 kPa). The liquid condensate was shown to contain 55.7 wt% methyl acetate, 10.02 wt% ethyl acetate, 15.24 wt% ethanol and 18.95 wt% methanol. The observed conversion to ethanol was 52.4 mol%.

Example 6

The procedure of Example 5 was repeated at a salt-bath temperature of 217 C and with an outlet gas pressure of 8.86 kg/cm<2>absolute (868 kPa), with a gas flow rate of

225 litres/hour, and with a flow rate of supplied liquid (methyl acetate) at 75 ml/hour. The liquid condensate was found to contain 19.31 wt% methyl acetate, 11.19 wt% ethyl acetate, 35.64 wt% ethanol and 31.96 wt% methanol. The observed conversion to ethanol was 72.40 mol%.

Example 7-

The procedure according to example 1 was repeated during use. of sec-butyl acetate instead of n-butyl butyrate at a feed rate of 118 ral/hour and a hydrogen flow rate of 143.9 liters/hour (measured at atmospheric pressure). In this experiment, the salt bath temperature was 203°C, and the outlet gas pressure was 10.55 kg/cm absolute (1035 kPa). The liquid condensate was shown to contain 6.0% by weight ethyl acetate, 20.6% by weight ethanol,

40.1% by weight sec-butyl acetate and 33.3% by weight sec-butanol. The observed conversion to ethanol was 59.9 mol%, and the selectivity to ethanol and sec-butanol was approximately 100%.

Example 8

Di-n-butyl oxalate was pumped at a rate of 15.4 ml/hour into an electrically heated gas/liquid mixture assembly to which hydrogen was also supplied at a controlled rate and pressure via an electrically heated line. The resulting vaporous mixture was passed through an insulated, electrically heated line to a hand-held heating coil before being passed through a stainless steel tubular reactor packed with 15 ml of a crushed catalyst. Both the tubular reactor and the pre-heating coil were immersed in a molten salt bath. The temperature of the salt bath was regulated until the temperature of the vaporous mixture, as detected by means of a thermocouple placed immediately upstream of the catalyst layer, was 24.0°C. The vaporous mixture coming from the reactor was passed through a water-cooled cooler and then through a number 2 cooled cooler through which the coolant was passed at -15°C. The resulting condensate was collected in a refrigerated collection device which was also kept at -15°C. The outlet gas pressure was regulated to 15.5 kg/cm 2 absolute (1518 kPa). The non-condensed gases were then passed through a downward-directed valve, the gas flow rate being monitored downstream from this valve in a wet gas meter. A gas flow rate of 156.6 liters/hour (measured at atmospheric pressure) was maintained during the experiment. The liquid volume rate for the di-n-butyl oxalate was 1.03 hour^.

The liquid condensate was analyzed by gas chromatography using a 2 meter stainless steel column (6 mm outside diameter) packed with polyethylene glycol (nominal molecular weight 20,000) on Chromosorb PAW, a helium gas flow rate of ' 30 ml/minute and a thermal conductivity detector.

Our instrument equipped with a chart recorder with a peak integrator and was calibrated using a mixture of ethanol, n-butahol, ethyl glycolate, n-butyl glycolate, ethylene glycol

and di-n-butyl oxalate of known composition. The condensate was shown to contain a mixture of 0.60 wt% ethanol, 31.37 wt% n-butanol, 0.1 wt% ethyl glycolate, 0.7 wt% n-butyl glycolate, 15.88 wt% ethylene glycol and 70 .15% by weight of n-butyl oxalate, corresponding to a 27.5% conversion with 93.0% selectivity to ethylene glycol

The catalyst used in this example was introduced

in the reactor which. a co-precipitated mixture of GuO and ZnO containing 33^3% CuO dg 65±.3% ZnO with a particle size in the range from 1.2 mm to 2.4 mm and an internal surface area of approx.

45. m 2 per gram. This was pre-reduced in the reactor below

using a 5% by volume N2 gas mixture at 200°C i

16 hours followed by pure hydrogen at 200°C for 16 hours, the gas flow rate in each case being approx. 20 litres/hour (measured at atmospheric pressure) and the gas pressure was 15.5 kg/cm<2>absolute (1518 kPa). After this pre-reduction step, the catalyst was kept in a hydrogen-containing atmosphere at all times. E xample - 9 The procedure according to example 8 was repeated using di-n-butyl oxalate at a feed rate of 30.6 ml/hour and a hydrogen flow rate of 284 liters/hour (measured at atmospheric pressure). The liquid condensate was shown to contain 0.25% by weight ethanol, 1-4.62% by weight n-butanol, 0.50% by weight n-butyl glycolate. 10.19% by weight ethylene glycol and 75.73% by weight di-n-butyl oxalate. The observed conversion to ethylene glycol was 21.5%,

and the selectivity to ethylene glycol was 94.7%.

Example 10

The procedure of Example 8 was repeated using diethyl succinate at a feed rate of 15.4 ral/

2

hour. The reactor pressure was 15.5 kg/cm absolute (1518 kPa) and the inlet temperature was 242°C. The gas flow rate was 157.8 liters/hour (measured at atmospheric pressure). The liquid volume rate was 1.03 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 32.2% conversion of diethyl succinate

/ with a selectivity of 85.0% to tetrahydrofuran and 14.0% to n-butanol.

Example 11,

The procedure according to Example 8 was repeated using diethyl maleate at a feed rate of

16.9 ml/hour. •The reactor pressure. was 15.1 kg/cm 2 absolute (1484 kPa), and the inlet temperature was 222°C. The gas flow rate was 156.6 liters/hour (measured at atmospheric pressure). The fluid volume rate was 1.13 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 22.2% conversion of diethyl maleate to tetrahydrofuran and n-butanol with a selectivity of 87.0% to tetrahydrofuran and 12.7% to n-butanol and a 15.6% conversion to. diethyl succinate.

Example 12

The procedure according to example 8 was repeated using cyclohexyl acetate at a feed rate of

2 17.3 ml/hour. The reactor pressure was 15.5 kg/cm absolute (1518 kPa), and the inlet temperature was 229°C. The gas flow rate was 157.2 liters/hour (measured at atmospheric pressure). The liquid volume rate was 1.15 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 92.8% conversion of cyclohexyl acetate.

Example 13

The procedure according to Example 8 was repeated using benzyl acetate at a feed rate of

2 47.8 ml/hour. The reactor pressure was 16.9 kg/cm absolute (1656 kPa), and the inlet temperature was 235°C'. The gas flow rate was 466.2 liters/hour (measured at atmospheric pressure). The liquid volume rate was 3.19 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 58.7% conversion of benzyl acetate with a selectivity of 98.5% to toluene.

Example, 14

The procedure according to Example 8 was repeated using methyl benzoate at a feed rate of

2

15.4 ml/hour. The reactor pressure was 15.5 kg/cm absolute (1518 kPa), and the inlet temperature was 220°C. The gas flow rate was 156.6 liters/hour (measured at atmospheric pressure). The liquid volume rate was 1.03 per hour.

The condensate separated into two layers, and no accurate analysis was attempted. However, gas chromatography showed that the main products were toluene and methanol. It was estimated that approx. 40% conversion of methyl benzoate had taken place, with only approx. 1% selectivity to benzyl alcohol.

Example 15

The procedure according to example 8' was repeated using ethyl phenyl acetate at a feed rate of

16.7 ml/hour. The reactor pressure was 15.5 kg/cm 2' absolute (1518 kPa), and the inlet temperature was 215°C. The gas flow rate was 157.8 liters/hour (measured at atmospheric pressure). The liquid volume rate was 1.11 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 46.7% conversion of ethyl phenylacetate with a selectivity of approx. 100% to ethanol, 27.0% to ethylbenzene and 72.9% to phenylethanol.

Example 16

The procedure according to Example 8 was repeated using ethylene glycol diacetate at a feed rate of 16.8 ml/hour. The reactor pressure was 28.0 kg/cm 2 absolute (2746 kPa), and the inlet temperature was 197°C. The gas flow rate was 240 litres/hour (measured at atmospheric pressure). The liquid volume rate was 1.12 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 13.0% conversion of ethylene glycol diacetate, with a selectivity of 87.7% to ethanol, 12.2% to ethyl acetate and 100% to ethylene glycol monoacetate.

Example 17

The procedure of Example 8 was repeated using ethyl lactate at a feed rate of 15.9 ml/hour. The reactor pressure was 16.4 kg/cm 2 absolute

(1608 kPa), and the inlet temperature was 234°C. Our gas flow rate 156.6 litres/hour (measured at atmospheric pressure). The liquid volume rate was 1.06 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to 34.7% conversion of ethyl lactate with a selectivity of 97.7% to 1,2-propanediol and 2.3% to n-propanol.

Example 1, 8

The procedure according to example 8 was repeated using dimethyl adipate at a feed rate of

2

16.7 ml/hour. The reactor pressure was 29.5 kg/cm absolute (2898 kPa), and the inlet temperature was 233°C. The gas flow rate was 240 litres/hour (measured at atmospheric pressure). The liquid volume rate was 1.11 per hour.

Gas chromatographic analysis showed that the condensate contained:

The condensate also contained some other unidentified compounds.

This corresponds to a 23.0% conversion of dimethyl adipate with a selectivity of approx. 100% to methanol and' approx. 95% to 1,6-hexanediol.

Example 19

The procedure according to Example 8 was repeated using t-butyl acetate at a feed rate of

.18.3 ml/hour. The reactor pressure was 26.7 kg/cm 2 absolute

(2622 kPa), and the inlet temperature was 200°C. The gas flow rate was 156.6 liters/hour (measured at atmospheric pressure). The liquid-volume rate was 1.22 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to 56.5% conversion of t-butyl acetate... Although the selectivity to ethanol and t-butanol appears to be high, accurate assessment of the selectivity was difficult because some

t-butanol underwent dehydration to isobutene which was detected as product but not collected.

Example 20

The procedure according to Example 8 was repeated using methyl methoxyacetate at a feed rate of 17.3 ml/hour. The reactor pressure was 29 kg/cm<2>absolute (2850 kPa), and the inlet temperature was 217°C. The gas flow rate was 157.2 liters/hour (measured at atmospheric pressure). The liquid-volume rate was 1.15 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 77.6% conversion of methyl methoxyacetate with a selectivity of 2.0% to ethanol, 93.2% to methoxyethanol

and 4.6% to methoxyethyl methoxyacetate.

Example 21

The procedure of Example 8 was repeated using methyl cyclohexane carboxylate at a feed rate of 16.0 ml/hour. The reactor pressure. was 14.8 kg/cm2 absolute (1449 kPa), and the inlet temperature was 217°C. The gas flow rate was 156.0 liters/hour (measured at atmospheric pressure). Our fluid volume rate 1.07 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 57.8% conversion with a selectivity of approx. 100% to methanol and cyclohexanemethanol.

Example 22

The procedure of Example 8 was repeated using ybutyrolactone at a feed rate of

2

16.2 ml/hour. The reactor pressure was 28.8 kg/cm absolute (2829 kPa), and the inlet temperature vaf. 22 6°C. The gas flow rate was 156.0 liters/hour (measured at atmospheric pressure). The liquid volume rate was 1.08 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 4 7.6% conversion of γ-butyrolactone with a selectivity of 53.2% to tetrahydrofuran, 41.8% to 1,4-butanediol and 5.0% to n-butanol.

Example . 23

The procedure of Example 8 was repeated using γ-butyrolactone at a feed rate of

16.0 ml/hour. The reactor pressure was 15.5 kg/cm 2 absolute (1518 kPa), and the inlet temperature was 215°C. The gas flow rate was 450 liters/hour (measured at atmospheric pressure). The liquid-volume rate was 1.07 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 9.4% conversion of Y-butyrolactone with a selectivity of 97.4% to 1,4-butanediol.

Example 2 4

The procedure of Example 8 was repeated using Y-butyrolactone at a feed rate of

2

15.4 ml/hour. The reactor pressure was 28.5. kg/cm absolute (2794.kPa), and the inlet temperature was 217°C. The gas flow rate was 450 liters/hour (measured at atmospheric pressure). The liquid volume rate was 1.03 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 16.1% conversion of γ-butyrolactone with a selectivity of 98.4% to 1,4-butanediol.

Example 2 5

The procedure according to example 8 was repeated using t-butyl formate at a feed rate of

64.1 ml/hour. The reactor pressure was 14.4 kg/cm 2. absolute

(1414 kPa), and the inlet temperature was 170°C. The gas flow rate was 155.4 liters/hour (measured at atmospheric pressure). The liquid volume velocity was 4.27 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 99% conversion of t-butyl formate. Exact determination of the selectivity was not attempted. Isobutene was also detected as a product, and this was probably formed by dehydration of t-butanol.

Example 2 6

The procedure according to Example 8 was repeated using phenyl acetate at a feed rate of

17.1 ml/hour. Our reactor pressure was 29.0 kg/cm 2 absolute (2850 kPa), and the inlet temperature was 222°C. The gas flow rate was 156.0 liters/hour (measured at atmospheric pressure). The liquid volume velocity was 1.14 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 40.9% conversion of phenylacetate with a selectivity of approx. 100% to phenol, 64.9% to ethanol and 35.1%-

to ethyl acetate.

Example 27

The procedure according to example. 8 was repeated using methyl formate at a feed rate of 60.0 ml/hr. The reactor pressure was 8.6 kg/cm<2>absolute (842 kPa). and the inlet temperature was 194°C. The gas flow rate was 540 liters/hour (measured at atmospheric pressure). liquid volume

the speed was 4.0 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 99.7% conversion of methyl formate with a selectivity of 99.0% to methanol.

Example 2 8

The procedure according to example 8 was repeated using methyl formate at a feed rate of

2

180 ml/hour. The reactor pressure was 8.4 kg/cm absolute (828 kPa), and the inlet temperature was 200°C. The gas flow rate was 540 liters/hour (measured at atmospheric pressure). The liquid-volume rate was 12.0 per hour.

Gas chromatographic analysis showed that the condensate contained:

This corresponds to a 76.9% conversion of methyl formate with a selectivity of 99.2% to methanol.

Example 2 9

The procedure of Example 8 was repeated using a mixture containing 75 mol% methyl glycolate and 25 mol% methanol at a feed rate of 10.0 ml/hour.

2 The reactor pressure was 28.1 kg/cm absolute (2760 kPa), and the inlet temperature was 210°C. The gas flow rate was 155.4 liters/hour (measured at atmospheric pressure). The liquid volume velocity was 0.67 per hour.

Gas chromatographic analysis showed that the condensate contained a mixture of methanol, methyl glycolate and ethylene glycol.

Calculations showed a 13.7% conversion of methyl glycolate with a selectivity of approx. 98.0% to ethylene glycol.

Example 30

Using a procedure similar to that described in Example 8, but with a catalyst volume of 50 ml, the hydrogenolysis of ethyl acetate was investigated using a crushed catalyst comprising a reduced mixture of 71.5% CuO and 18.5 % ZnO. With a liquid supply rate of 21.7 ml/hour, corresponding to a volume rate of 0.43 per hour, and a 5 mol%

2 ethyl acetate in hydrogen feed mixture, at 11.6 kg/em absolute (1138 kPa) and 150°C a conversion of 65/1% was observed with approximately quantitative formation of ethanol. Under the same pressure and flow conditions at 200°C, the observed conversion was 90.6%, also with approximately quantitative formation of ethanol.

Example 31

When Example 30 was repeated using a catalyst comprising a reduced mixture of 44.3% CuO, 46.3% ZnO and 9.4% Al 2 O 3 , the conversion at 150°C was 48.9%, and at 200°C was the 84.2%, in each case with approximately quantitative formation of ethanol.

Claims (77)

.1. Process for producing hydrogenolysis of a carboxylic acid ester, which comprises bringing a mixture containing the ester and hydrogen into contact with a hydrogenolysis catalyst at an elevated temperature, characterized in that a vaporous mixture comprising the ester and hydrogen is brought into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm 2 absolute (approx. 9.8 kPa) up to approx. 100 kg/cm <2> absolute (approx. 9813 kPa).. 2. Method according to claim 1, characterized 2 in that the pressure is in the range from approx. 0.1 kg/cm absolute (approx. 9.8 kPa) to approx. 50 kg/cm <2> (approx., 4906 kPa). 3. Method according to claim 1 or 2, characterized in that the pressure is in the range from approx. 5 kg/cm <2> 2 absolute (approx. 491 kPa) to approx. 25 kg/cm absolute (approx. 2453 kPa). 4. Method according to one of claims 1 to 3, characterized by . that the temperature is in the range from approx. 180°C to approx. 240°C. 5. Method according to one of claims 1 to 4, characterized in that the carboxylic acid ester is selected from esters with the general formula: R (C00R1) n and (R' 1 'C00) R1 ' 1 P where n and p each mean a whole number from 1 to approx. 5, and R, R <1> , R <1> ' and R" <1> each mean an optionally substituted, saturated or unsaturated, cyclic or acyclic hydrocarbon radical, where one or more carbon atoms may be replaced by heteroatoms selected from nitrogen, oxygen and phosphorus. 6. Method according to claim 5, characterized in that each of R, R', R <1> ' and R'' <1> contains from 1 to approx. 12 carbon atoms. 7. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of formic acid, and methanol is a hydrogenolysis product. 8. Method according to claim 7, characterized in that the carboxylic acid ester is selected from methyl formate, isopropyl formate and t-butyl formate. 9. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of acetic acid, and ethanol is a hydrogenolysis product. 10. Method according to claim 9, characterized in that the at-carboxylic acid ester is selected from methyl acetate, ethyl acetate, sec-butyl acetate, t-butyl acetate, phenyl acetate, cyclohexyl acetate and benzyl acetate. .11. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of butyric acid, and n-butanol is a hydrogenolysis product. 12. Method according to claim 11, characterized in that the carboxylic acid ester is n-butyl butyrate. 13. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of oxalic acid, and ethylene glycol is a hydrogenolysis product. 14. Process according to claim 13, characterized in that the carboxylic acid ester is di-n-butyl oxalate. 15. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is a. ester of an acid selected from maleic acid, fumaric acid, acetylene dicarboxylic acid and succinic acid, and the hydrogenolysis gives 1,4-butanediolO g/or tetrahydrofuran. 16. Process according to claim 15', characterized in that the carboxylic acid ester is diethyl succinate or diethyl maleate. 17. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is a ester of phenylacetic acid, and 2-phenylethanol is a hydrogenolysis product. 18.. Method according to claim 17, characterized in that the carboxylic acid ester is ethyl phenyl acetate. 19. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of lactic acid, and 1,2-propanediol is a hydrogenolysis product4 20. Method according to claim 19, characterized in that the carboxylic acid ester is ethyl lactate. 21. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of adipic acid, and 1,6-hexanediol is a hydrogenolysis product. 22. Method according to claim 21, characterized in that the carboxylic acid ester is dimethyl adipate. .23. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is a lactone, and a diol is a hydrogenolysis product. 24. Method according to claim 23, characterized in that the carboxylic acid ester is γ-butyrolactone, and 1,4-butanediol is a hydrogenolysis product. 25. Method according to one of claims 1 to 6, characterized in that the carboxylic acid ester is an ester of glycolic acid, and ethylene glycol is a hydrogenolysis product. 2 6, Process according to claim 25, characterized in that the carboxylic acid ester is methyl glycolate. 27. Method according to one of claims 1 to 26, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a., mixture which before reduction comprised from approx. 10 to approx. 70% by weight CuO and approx. 90, to approx. 30 wt% ZnO. 28. Method according to claim 27, characterized in that the mixture comprises from approx. 20 to approx. 40% by weight CuO and from approx. 60 to 80% by weight ZnO. 29. Method according to one of claims 1 to 26, characterized in that the catalyst comprises a reduced•mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprised from approx. 65 to approx. 85% by weight CuO and approx. 15 to approx. 35 wt% ZnO. 30. Process for the production of ethylene glycol comprising hydrogenolysis of an oxalic acid ester in that a mixture containing end the ester and hydrogen are brought into contact with a hydrogenolysis catalyst. at an elevated temperature, characterized in that a vaporous mixture comprising the ester and hydrogen is brought into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature of about advised from approx. 75°C up to approx. 300°C and at a pressure in the range 2 from approx. 0.1 kg/cm absolute (approx. 9.8 kPa) up to approx. 100 kg/cm absolute (approx. 9813 kPa), and the resulting ethylene glycol is recovered. 31. Method according to claim 30, characterized in that ■ the pressure is in the range from approx. 0.1 kg/cm <2> absolute (approx.' 9.8 kPa) .to approx..50 kg/cm <2> absolute (approx. 4906 kPa) . 32. Method according to claim 30 or '31, characterized in that the pressure is in the range from approx. 5 kg/cm 2 absolute (approx. 491 kPa) to approx. 35 kg/cm 2absolute (approx. 3435 kPa). 33. Method according to one of claims 30 to 32, characterized in that the temperature is in the range from approx. 180°C to approx. 240<Q>C, 34. Method according to one of claims 30 to 33, characterized in that the carboxylic acid ester is di-n-butyl oxalate. 35. Method according to one of claims 30 to 34, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 10 to approx. 70% by weight CuO and approx. 90. to approx. 30.wt%.ZnO. 36.. Method according to claim 35, characterized in that the mixture comprises from approx. 20 to approx. 40 wt% CuO and from approx. 60 to 80 wt% ZnO. 37. Method according to one of claims 30 to 34, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises approx. 65 to approx. 85% by weight CuO and approx. 15 to approx. 35 wt% ZnO. 38. Process for the production of methanol, characterized in that a vaporous mixture containing a formic acid ester and hydrogen is brought into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm absolute (approx. 9.8 kPa) up to approx. 100 kg/cm 2 absolute (about 9813 kPa), and the resulting methanol is recovered. 39. Method according to claim 38, characterized in that the pressure is in the range from approx. 0.1 kg/cm 2absolute (approx. 9.8 kPa) to approx. 50 kg/cm <2> absolute (approx. 4906 kPa). 40. Method according to claim 38 or 39, characterized in that the pressure is in the range from approx. 5 kg/cm <2> absolute (approx. 491 kPa). to approx.-35 kg/cm 2 absolute (approx. 3435 kPa) . 41. Method according to one of claims 38 to 40, characterized in that the temperature is in the range from approx. 130°C to approx. 220°C. 42., Method according to one of claims 38 to 41, characterized in that the formic acid ester is selected from methyl formate, isopropyl formate and t-butyl formate: 43. •Procedure according to one of claims 38 to 42, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide. derived .from a mixture which before reduction comprises from approx. 10' to approx. 70% by weight CuO and approx. 90 to approx. 30 wt% ZnO. 44. Method according to claim 43, characterized in that the mixture comprises from approx. 20 to approx. 40% by weight CuO and from approx. 60 to 80 wt% ZnO. .45. Method according to one of claims 38 to 42, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 65 to approx. 85% by weight CuO and approx. 15 to approx. 35 wt% ZnO. 46. Process for producing ethanol, characterized in that a vaporous mixture containing an acetic acid ester and hydrogen is brought into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm2 absolute ■ 2 (approx. 9.8 kPa) up to approx. 100 kg/cm absolute (approx. 9813 kPa), and resulting ethanol is recovered. 47. Method according to claim 46, characterized in that the pressure is in the range from approx. • 0.1 kg/cm2absolute (approx. 9.8 kPa) to approx. 50 kg/cm2 absolute (approx. 4906 kPa). 48. Method according to claim 46 or 47, characterized in that the pressure is in the range from approx. 5 kg/cm2 absolute (approx. 491 kPa) to c. 35 kg/cm 2 absolute (approx. 3435 kPa)'. .49. Method according to one of claims 46 to 48, characterized in that the temperature is in the range from approx. 180°C to approx. 240°C. 50. Method according to one of claims 4 6 to 49, characterized in that the acetic acid ester is selected from methyl acetate, ethyl acetate, sec-butyl acetate and t-butyl acetate. 51. Method according to one of claims 46 to 50, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 10 to approx. 70% by weight CuO and approx. 90 to approx. 30 wt% ZnO. 52. Method according to claim 51, characterized in that the mixture comprises from approx. 20 to approx. 40 wt% CuO bg from approx. 60 to 80% by weight ZnO.. 53. Method according to one of claims 4 6 to 50, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 65 to approx. 85% by weight CuO and approx. 15 to approx. 35 wt% ZnO. 54. Process for the production of 1,4-butanediol and/or tetrahydrofuran, characterized in that a vaporous mixture containing an ester of an acid selected from maleic acid, fumaric acid, acetylene dicarboxylic acid and succinic acid and hydrogen is brought into contact with a catalyst which includes a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300°C and at a pressure in the range from approx. 0.1 kg/cm <2> absolute (approx. - 9.8 kPa) up to approx. 2 100 kg/cm absolute (about 9813 kPa), and the resulting 1,4-butanediol and/or tetrahydrofuran are recovered. 55. Method according to claim 54, characterized 2 in that the pressure is in the range from approx. 0.1 kg/cm absolute (approx. 9.8 kPa) to approx. 50 kg/cm <2> absolute (approx. 4906 kPa) . 56.. Method according to claim 54 or 55, character-. in that the pressure is in the range from approx. 5 kg/cm2 absolute (approx. 491 kPa) to approx. 35 kg/cm 2 absolute (approx. 3435 kPa). 57. - Method according to one of claims 54 to 56, characterized in that the temperature is in the range from approx. 180°C to approx. 240°C. 58. Method according to one of claims 54 to 57, characterized in that the ester is diethyl maleate. 59. Method according to one of claims 54 to 58, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 10 to approx. 70% by weight CuO and approx. 90 to approx. 30 wt% ZnO. 60. Method according to claim 59, characterized in that the mixture comprises from approx. 20 to approx. 40% by weight CuO and from approx. 60 to 80 wt% ZnO. 61. Method according to one of claims 54 to 58, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 65 to approx. 85% by weight CuO and approx. 15" to about 35 wt% ZnO. 62. Process for producing ethylene glycol, characterized in that a vaporous mixture containing a glycolic acid ester and hydrogen is brought into contact with a catalyst comprising, a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300 C and at a pressure in the range from approx. 0.1 kg/cm <2> absolute (approx. 9.8 kPa) up to approx. 100 kg/cm <2> absolute (approx. 9813 kPa), and the resulting ethylene glycol is recovered. 63. Method according to claim 62, characterized in that the pressure is in the range from approx. 0.1 kg/cm 2absolute (approx. 9.8 kPa) to approx. 50 kg/cm 2 absolute (approx. 4906 kPa). ' 64. Method according to claim 62 or 63, characterized in that the pressure is in the range from. about. 5 kg/cm <2> absolute (approx. 491 kPa) to approx. 35 kg/cm 2 absolute (approx. 34'35 kPa). 65. Method according to one of claims 62 to 64, characterized in that the temperature is in the range from approx. 180°C to approx. 240°C. 66. Method according to one of claims 62 to 65, characterized in that the glycolic acid ester is methyl glycolate. 67. Method according to one of claims 62 to 66, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 10 to approx. 70% by weight CuO and approx. 90 to approx. 30 wt% ZnO. 68. Method according to claim 67, characterized in that the mixture comprises from approx. 20 to approx. 40% by weight CuO and from approx. 60 to 80 wt% ZnO. 69. Method according to one of claims 62 to 66, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from > a mixture which before reduction comprises from approx. 65 to approx. 85% by weight CuO and approx. 15 to approx. 35 wt% ZnO. 70. Process for the production of .1,4-butanediol, characterized in that a vaporous mixture containing butyrolactone and hydrogen is brought into contact with a catalyst comprising a reduced mixture of copper oxide and zinc oxide, at a temperature in the range from approx. 75°C up to approx. 300 C and at a pressure in the range from approx..0.1 kg/cm 2 absolute (approx. 9.8 kPa) up to approx. 100 kg/cm <2> absolute (about 9813 kPa), and the resulting 1,4-butanediol is recovered. 71. Method according to claim 70, characterized in that the pressure is in the range from approx. 0.1 kg/cm 2 absolute 2 (approx. 9.8 kPa) to approx. 50 kg/cm absolute (approx. 4906 kPa). . 72. Method according to claim 70 or 71, character is in that the pressure is in the range from approx. 5 kg/cm <2> absolute (approx. 491 kPa) to approx. 45 kg/cm 2absolute (approx. 4416 kPa). 73. Method according to one of claims 70 to 72. characterized by the temperature being in the range from approx. 180°C to approx. 240°C. 74. Method according to one of claims 70 to 73, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 10 to approx. 70 weight CuO and approx. 90 to approx. 30 wt in ZnO. 75. Method according to claim 74, characterized by. that the mixture comprises from approx. 20 to approx. 40-weight CuO and from approx. 60 to 80 wt% ZnO. 76. Method according to one of claims 70 to 73, characterized in that the catalyst comprises a reduced mixture of copper oxide and zinc oxide derived from a mixture which before reduction comprises from approx. 65 to approx. 85 wt in CuO and approx. 15 to approx. 35 wt in ZnO. 77. Product from a method according to one of claims 1 to 76.