Process for the preparation of ethylene glycol

PFENNlNQ. MAAS

MEINIQ - LEMKE - SPOTT

• CHLEISSHEIMERSTR 299 • 000 MONKS 40

PF 5O-O1-1512 A

Atlantic Richfield Company, Los Angeles, California, V.St.A.

Process for the preparation of ethylene glycol

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In DT-OS 27 21 734 is a method of oxidative carbonylation of an alcohol. Oxygen and carbon monoxide in the presence of a particular catalyst system for the preparation of oxalic acid esters described. Oxalic acid esters are used commercially as solvents and as starting materials for dyes and in the production of pharmaceuticals, but there is no reference in the literature to the possibility of converting oxalic acid esters in the vapor phase into the industrially valuable ethylene glycol.

An efficient process of vapor phase hydrogenation of oxalic acid esters for producing ethylene glycol has now been found. The process of the present invention is directed to the production of ethylene glycol by hydrogenating oxalic acid esters at elevated temperatures and at relatively low hydrogen pressures in the presence of a hydrogenation catalyst, for example, a copper-zinc chromite catalyst, a copper-alumina catalyst, or other mixed copper and metal oxide catalysts. Hydrogenation catalysts and supported catalysts containing them and mixtures thereof, which are suitable as catalysts for the hydrogenation of oxalic acid esters in the vapor phase to obtain high yields of ethylene glycol.

For the preparation of alcohols and glycols by hydrogenating certain esters of monobasic and higher dibasic acids in the liquid phase and of esters of hydroxyacetic acid in the vapor phase, a number of processes are already known.

In a paper by H. Adkins in R. Adams et al, Organic Reactions, Vol. VIII, Chap. 1, John Wiley and Sons, Inc., New York, 1954, pp. 1-27, there is provided a general mechanism for the liquid phase hydrogenation of esters to alcohols, mentioning that diethyl oxalate in the liquid phase provides a good yield of ethylene glycol , but only if it is carried out at a pressure which is much higher than in the liquid phase hydrogenation customary pressures, ie higher than 280 atmospheres.

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US Pat. No. 2,305,104 discloses a process for the vapor-phase hydrogenation of alkyl esters of hydroxyacetic acid, wherein a reaction zone charged with a double catalyst is at temperatures between 150 and 300 ^eC and pressures of 10 to 1000 atmospheres or more are used.

GB 55524O and 575 380 describe processes for the catalytic vapor-phase hydrogenation of hydroxyacetic acid and its derivatives (esters) or an ester of glycolic acid at temperatures of 150 to 300 ⁰C and pressures of 10 to 10OO atmospheres indicated for the production of ethylene glycol.

Ethylene glycol is an important commercial product used in fluids for use in antifreeze and antifreeze fluids, in hydraulic fluids, in the manufacture of alkyd resins, solvents and polyester fibers.

The invention relates to a process for preparing ethylene glycol by catalytic vapor-phase hydrogenation of oxalic acid esters, in particular oxalic acid dialkyl esters, for example oxalic acid dimethyl, diethyl, dipropyl and dibutyl esters, wherein the oxalic acid ester is passed along with hydrogen at elevated temperatures and relatively low hydrogen pressure at the desired flow rates in a pressure reactor via a suitable hydrogenation catalyst. By using an oxalic acid ester feedstock which has been substantially desulfurized, side reactions are kept to a minimum under the operating conditions of the present invention and the activity of the hydrogenation catalyst is greatly enhanced because sulfur impurities very rapidly cause losses of catalytic activity and hence low levels of combustion Yields of ethylene glycol.

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The object of the invention is primarily to provide a process for the production of ethylene glycol in high yield and high degree of conversion of the reactants by catalytic hydrogenation of an oxalic acid ester.

It is another object of the invention to provide a process in which virtually sulfur-free oxalic acid esters are hydrogenated in the vapor phase at temperatures and pressures to ethylene glycol, in which the activity of the hydrogenation catalyst and the yield are highest.

Finally, the objects of the invention include new optimum operating conditions for the catalytic vapor-phase hydrogenation of an oxalic acid ester to ethylene glycol.

These objects are achieved by the invention according to which ethylene glycol is prepared from an oxalic acid ester such as diethyl oxalate by subjecting a substantially sulfur-free oxalic acid ester to vapor phase catalytic hydrogenation at elevated temperature and relatively low hydrogen pressure to produce ethylene glycol in addition to the corresponding alcohol.

The reaction can be represented by the following schematic equation:

OO ROCCOR + 4H₂ HIGH₂CH₂OH + 2R0H

Oxalic ethylene alcohol

acid-glycol

ester

Where R is an optionally substituted alkyl or aralkyl group which may contain other substituents,

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for example, alkoxy, amino, carboxy and cyano groups which do not interfere with the reaction of the present invention. The alcohol formed by the hydrogenation of the oxalic acid ester in addition to the desired ethylene glycol can be separated from the reaction mixture without difficulty and converted by the oxidative carbonylation, for example according to the above-mentioned DT-OS, again in an oxalic acid ester.

The vapor phase catalytic hydrogenation process of the invention may be carried out in any suitable reactor, for example a tubular reactor, wherein an oxalic acid ester to be hydrogenated, which is heated to vapor or gaseous state, together with hydrogen at the desired pressures and temperatures via a hydrogenation catalyst which may be in the form of a packed bed, a fluidized bed or a moving bed. Since vapor phase hydrogenation reactions are generally exothermic, cooling means may be employed in and / or outside the reactor to maintain the temperature within the desired range. The vaporous reaction products leaving the hydrogenation reactor can be recovered by any known method, for example by condensation, and then subjected to fractional distillation to separate the ethylene glycol and alcohol from unreacted material and by-products. The reaction is generally carried out in a cyclic or continuous mode, and appropriate recycling of excess or unreacted hydrogen or oxalic acid ester can be employed.

The oxalic acid esters which can be used in the process according to the invention correspond to the general formula

OO ROCCOR,

wherein R has the meaning given above. The preferred in the hydrogenation process for the preparation of IHhvjl cnglykol

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Esters used are those in which R represents an alkyl group having 1 to 8 carbon atoms, for example, oxalic acid dimethyl, diethyl, dibutyl and di-amyl esters. The esters are preheated and evaporated, as determined by their vapor pressure, to ensure that virtually all of the ester is in the vapor state when passed over the catalyst bed along with hydrogen. The catalyst bed is maintained at a temperature at which condensation of the oxalic acid ester or ethylene glycol formed is prevented. Temperature and pressure of the reaction are chosen so that the reaction products emerging from the reaction zone are present in the gas phase.

In the hydrogenation of oxalic acid esters, hydrogen is generally used in excess of the stoichiometrically required amount for the topping of the oxalic acid ester in ethylene glycol and the corresponding alcohol. The preferred molar ratio of hydrogen to oxalic acid ester entering the reaction section is 30: 1. Higher or lower ratios of hydrogen to oxalic acid ester may also be employed in the process as long as the ester is in the vapor state and the hydrogen is used in at least the stoichiometric amount of 4: 1.

The hydrogenation catalysts that can be used in the process of this invention are described in the literature, and any known hydrogenation catalyst or mixture of such catalysts suitable for the topping of esters in alcohols can be used. Thus, one can use catalysts which are described together with their preparation in US Pat. Nos. 2,094,611, 2,305,104 and 3,374,184. In general, hydrogenation catalysts containing copper in elemental form or in combination with oxygen, as well as other hydrogenation metal oxides used in conjunction with copper, can be used.

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iff

be used with or without carrier. Particularly preferred catalysts are the copper-zinc chromite or copper chromite catalysts, which may be reinforced with barium or sodium hydroxide and reduced in hydrogen. Examples of hydrogenation catalysts other than those mentioned above for the purpose of the present invention include zinc Z copper Z cadmium Z chromite, copper ammonium chromate, zinc chromium oxide, Raney nickel, nickel on kieselguhr and chromites of manganese and magnesium. Other suitable catalysts are compositions containing tin, silver, cadmium, zinc or platinum, as well as chromium oxides of these metals. Many suitable hydrogenation catalysts are commercially available, for example, the copper-zinc chromite catalyst (Girdler T-359), copper barium chromite (Harshaw Cu 11O7) catalysts, and the sodium hydroxide-reinforced copper chromite catalyst (Houdry 536 CP).

The hydrogenation catalysts can be prepared by any suitable methods, for example by precipitation or fusion. The preferred copper chromite and copper-zinc chromite catalysts are precipitated catalysts and can be prepared by the method set forth in British Pat. No. 575,380 and then reduced to hydrogen. For example, a copper chromium hydrogenation catalyst can be prepared by neutralizing 1 mole of chromium trioxide and 1 mole of cupric nitrate trihydrate in aqueous ammonium carbonate to pH 7. The precipitate is washed and dried and then at 400⁰C calcined. The calcined catalyst is then made to particle sizes corresponding to mesh apertures of 2057 to 1204 microns or 2057 to 500 microns, and in hydrogen, for example, 17 hours at 200^eC reduced.

The gas-phase hydrogenation catalysts used in the process according to the invention can lose activity or be degraded in a short time, which is due to a number of different

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Factors and conditions that need to be limited, combated or eliminated in order to increase the cost-effectiveness of the process. In such reactions, catalyst poisoning and consequent loss of catalyst activity is apparently due to uncontrolled or erroneous distribution of the heat of reaction, causing hydrogenolysis of the ethylene glycol formed and other chemical-type factors, for example, in the hydrogenation of diethyl oxalate, the formation of copper salts (oxalates and Glycolates), 2-ethoxyethanol, ethyl glycolate and polymeric esters, for example, polyglycolates or polymeric ethylene oxalate which, when deposited on the catalyst surface, reduce the hydrogenation activity of the catalyst. Oxalic acid esters themselves polymerize neither in the preheater nor in the reactor nor on the catalyst surface. Other factors include catalyst poisons, such as sulfur or halogen compounds, which may come into contact with the introduced hydrogen or oxalic acid ester to be hydrogenated with the catalyst, for example, hydrogen sulfide and organic sulfates, as well as a combination of the above factors and other causes. The amount of by-products formed in the reaction is generally indicative of catalyst degradation.

Hydrogenolysis and the concomitant byproduct formation on the catalyst surface as well as poisoning and deterioration of the catalyst by substances contained in the charge and loss of catalyst activity are reduced to a minimum by the measures of the method according to the invention. Hydrogenation catalyst activity can be significantly enhanced by a number of variables, namely, (1) prereduction of the hydrogenation catalyst, particularly a copper-containing catalyst, to reduce or prevent oxidation of the oxalate, increase hydrogenation activity of the catalyst, (2) remove sulfur from the oxalic acid ester to be introduced , preferably up to

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(3) using a substantially sulfur and halogen-free hydrogen, (4) using a catalyst bed which is diluted or mixed with inert carriers such as tabular alumina, silica and glass beads, whereby the distribution of the heat of reaction improved and localized overheating in the bed can be reduced or avoided, thereby limiting the extent of hydrogenolysis, and (5) purifying the reaction catalyst system from time to time, if necessary, with hydrogen during an interruption of the operation of decomposing impurities, especially cupric oxalate, which may have accumulated on the catalyst surface. The purification with hydrogen can be carried out at reaction temperatures (catalyst bed temperatures) and reaction pressures and generally takes 5 to 20 hours to complete.

The prereduction of the hydrogenation catalysts, such as copper chromite or Kupferζinkchromit, carried out for the substantial reduction of copper compounds, such as copper oxide, to metallic copper. It is most conveniently effected with hydrogen in a suitable apparatus. The specific reduction measures used are well known and may vary from catalyst to catalyst. Hydrogen reductions generally occur at a temperature of from 100 to 450⁰C carried out with hydrogen pressures of 0.01 to 10 atmospheres. All copper oxides formed in the reaction are rapidly reduced to metallic copper in the presence of hydrogen.

Sulfur may usually be present in the form of an organic sulfate such as ethyl hydrogen sulfate, diethyl sulfate and di-n-butyl sulfate as an impurity in the corresponding oxalic acid dialkyl ester to be hydrogenated. Since such sulfur, which may be present in the oxalic acid ester in amounts up to 700 ppm, will rapidly poison the hydrogenation catalyst, particularly copper chromite, it must be removed from the feed oxalate as much as possible, preferably to levels less than

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0.4 ρ {πη. An example of a convenient method of reducing the sulfur content of diethyl oxalate is by treating the ester with sodium ethoxide (sodium ethylate) at a temperature of 80 ° C and optionally thereafter neutralizing any unreacted sodium ethoxide with acetic acid and distilling the oxalate solution to leave the nonvolatile sodium sulfate formed , To avoid the possible formation of mixed esters and other side reactions, sodium methylate and sodium butylate may also be used in the same way for the treatment of the respective oxalic acid dialkyl ester.

Hydrogen sulfide and / or hydrogen chloride, which can be an impurity in the hydrogen feed and cause catalyst poisoning, can be completely or substantially removed by any of the conventional gas scrubbing systems. Convenient methods are to pass the gas through a bed of a mixture of Fe₂O₃ with fly ash or through a bed of CuO / ZnO. *

In carrying out the process according to the invention, a virtually sulfur-free, vaporized oxalic acid ester is generally used together with virtually sulfur-free hydrogen via a prereduced hydrogenation catalyst maintained at a reaction (catalyst bed) temperature of 150 to 300 ° C., preferably between 200 and 230 ° C. at a hydrogen pressure of 1 to 70 atmospheres, preferably 10 to 33 atmospheres, and a rate of flow (the volumes of gaseous calibration of oxalic acid ester and hydrogen calculated at ordinary temperature and pressure per hour over one volume of the hydrogenation catalyst bed) from 3OO to 20,000 hours'¹, preferably 8000 to 15,000 hours "¹, guided. The liquid hourly rate of oxalic acid ester (calculated as the volume of liquid of the ester per unit volume of hydrogenation catalyst) passed over the catalyst in vapor form

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is, is in the inventive method Ο, ΟΟ1 to 5.0 hour ", preferably 1.0 to 3.5 hours

The invention is further illustrated by the following examples.

In all of these examples, the hydrogenation experiments are carried out in a straight tubular reactor having an inner diameter of 25 mm and a length of 91 cm, which is provided with a heating mantle to bring the catalyst bed to the reaction temperature. A hydrogenation catalyst bed (100 ml) (with or without inert diluent) is placed in the center of the reaction tube and held in position with glass wool plugs. A metal spiral passage for the distribution and circulation of vapors is placed at the top of the catalyst bed. To evaporate the oxalic acid ester and preheat the hydrogen prior to entering the hydrogenation reactor, a glass tube filled with glass beads is used. The gaseous products and by-products leaving the reactor are introduced into a straight water-cooled tube cooler and then into a liquid-gas separator, the reaction products being purified by gas-liquid chromatography (glc) and NMR spectra on ethylene glycol. Alcohol, unreacted oxalic acid ester and by-products were analyzed. The ethylene glycol and the corresponding alcohol can then be separated from the condensate by fractional distillation.

example 1

The hydrogenation reactor is charged with 100 ml of a copper-zinc chromite catalyst (Girdler T-359) prereduced at 213 ° C with 1 atmosphere of hydrogen without inert diluent. 260 ppm sulfur containing diethyl oxalate and hydrogen are preheated to 190 ° C., thereby evaporating the diethyl oxalate. The gaseous mixture of vaporized oxalate and hydrogen is added to the

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Reactor and over the catalyst of 215 ⁰C under a hydrogen pressure of 70 atmospheres at a flow rate (SV) of about 4900 hours and a liquid and hourly throughput rate (LHSV) of 0.3 hour passed. The release of heat of reaction is noted. The reaction is continued for a total of 9 hours and fluid samples are taken continuously. Gas-liquid chromatography of the liquid product samples yields 11.7 to 18.9 weight percent ethylene glycol, 44.5 to 62.7 weight percent ethanol and 6.4 to 30.9 weight percent unreacted diethyl oxalate besides 9.7 to 22.6 weight percent undetermined by-products. Analysis of the catalyst reveals the presence of 0.14 weight percent sulfur versus 0.09 weight percent sulfur on the catalyst before use, and the presence of copper oxalate.

Example 2

The procedure described in Example 1 is repeated using a prereduced barium-reinforced copper chromite catalyst (Harshaw Cu 1107). The reaction is continued for a total of 18 hours and samples of liquid product are taken continuously. Analysis of these samples gives 5.0 to 12 weight percent ethylene glycol, 21 to 42 weight percent ethanol, and 29.1 to 40.9 weight percent unreacted diethyl oxalate. The deterioration of the catalyst is in turn caused by the sulfur content of the diethyl oxalate feed. The theoretical yield of ethylene glycol and the corresponding ethanol by catalytic hydrogenation of diethyl oxalate using stoichiometric amounts of the reactants is 40 and 60 weight percent, respectively.

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Example 3

The hydrogenation reactor is filled with 50 ml of one at 225 ⁰C is charged with 70 liters per hour of hydrogen at atmospheric pressure in 4.5 hours of prereduced sodium hydroxide-reinforced copper chromite catalyst prepared according to Example 4 of U.S. Patent 3,374,184 (commercially available as Houdry 536 CP catalyst). The catalyst is mixed in the ratio of 50 ml to 50 ml with tabular alumina having a particle size corresponding to screen openings of 2057 to 1204 microns. Diethyl oxalate is desulfurized by reaction with sodium ethoxide at 80 ° C, followed by neutralization of the unreacted ethoxide with acetic acid and distillation of diethyl oxalate to a sulfur content of 17 ppm, together with hydrogen to 200 ⁰C preheated and into the reactor and over the catalyst at a temperature of 215 "C under a hydrogen pressure of 3.15 atmospheres with an SV, based on the volume of the catalyst bed of 100 ml of 500 hours and a LHSV of diethyl oxalate of 0.5 The release of heat of reaction is observed which travels down the bed from the beginning of the experiment when the gaseous mixture of diethyl oxalate and hydrogen contacts the catalyst bed. Liquid samples are withdrawn every 15 minutes, and the reaction is carried out for 10 hours, at which time the catalyst activity apparently decreases as a result of sulfur poisoning. The gas-liquid chromatography of the samples taken shows yields of 20 to 37.5 weight percent ethylene glycol, 30 to 34 weight percent ethanol and 100 percent conversion of diethyl oxalate. The diluted with inert alumina catalyst reduces the intensity of the released heat of reaction and limits the extent of hydrogenolysis.

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Example 4

The procedure described in Example 3 is repeated using a catalyst of the same type operating at 2OOO for 17 hours under 1 atmosphere of hydrogen ⁰C, and from diethyl oxalate which has been desulfurized to a sulfur content of less than 0.2 ppm with sodium ethoxide as described in Example 3. Prior to preheating and mixing with the vaporized diethyl oxalate, the feed hydrogen is passed through a sulfide scrubber containing a mixture of Fe₃O₃ and contains flyash. The reaction conditions are as follows: temperature of catalyst bed 200⁰C, 31.5 atmospheres hydrogen pressure, steam flow rate 3000 hours and LHSV O, 2 to 0.5 hour. The hydrogenation is continued for 95 hours, after which the catalyst appears unimpaired, which results from a stable position of the released heat of reaction less than 1/3 of the catalyst bed length and the consistently high selectivity to ethylene glycol with 100 percent conversion of diethyl oxalate. Samples of the condensed liquid reaction product are taken every 15 minutes and analyzed by gas-liquid chromatography. These analyzes of the samples provide 36.2 to 40 weight percent ethylene glycol, water concentrations of 0.6 to 1.7 weight percent, 0 weight percent diethyl oxalate (100 percent conversion of diethyl oxalate), and trace amounts of ethyl glycolate and diethylene glycol.

Example 5

The hydrogenation reactor is charged with 53 ml of copper chromite catalyst having a particle size corresponding to mesh sizes of 2Ο57 to 1204 microns diluted with 50 ml of tabular alumina having the same particle size. The catalyst is prepared by neutralizing a solution of 1 mole of chromium trioxide and 1 mole of cupric nitrate trihydrate in 2 liters of room temperature water with a solution of ammonium carbonate to one

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pH of 7 produced. The precipitate is washed and dried and at a temperature of 400⁰C calcined and brought by milling and sieving to a particle size corresponding to sieve openings of 2057 to 1204 microns. The catalyst is then hydrogenated at 2OO for 54 hours under 1 atmosphere of hydrogen⁰C completely reduced. By treatment with sodium ethoxide to a sulfur content of less than 0. 4 ppm desulfurized diethyl oxalate and hydrogen become 2OO⁰C preheated to evaporate the diethyl oxalate. The mixture containing the vaporized diethyl oxalate and hydrogen is introduced into the reactor and over the catalyst at 220 ° C⁰C under a hydrogen pressure of 31.5 atmospheres with a throughput speed of 10 000 hours and a LHSV of 1.5 hours The reaction is continued for 460 hours, with only a slight deterioration of the catalyst is observed, only after 110 hours Using the catalyst, one can observe the formation of trace amounts of nonselective by-products, ie, 2-ethoxyethanol, ethyl glycolate, and diethyl ether. Liquid samples of the reaction product are taken every 30 minutes and analyzed by gas-liquid chromatography. Analyzes of the samples provide greater than 95 percent selectivity to ethylene glycol at 100 percent conversion of diethyl oxalate and yields of 36.8 to 39.6 weight percent ethylene glycol, 0.83 to 1.58 weight percent water, 0 weight percent unreacted diethyl oxalate and trace amounts of 2-ethoxyethanol, ethyl glycolate and diethyl ether, and ethanol as the remainder.

Example 6

The hydrogenation reactor is charged with the mixture of copper chromite catalyst and aluminum oxide described in Example 5 in the amount also indicated there. Diethyl oxalate with a sulfur content of less than 0.2 ppm and hydrogen are used to evaporate the diethyl oxalate to 200⁰C

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heated. The gas mixture oxalate / hydrogen is introduced into the reactor and at 232⁰C (temperature of the catalyst bed) under a hydrogen pressure of 14 atmospheres with an SV of 120OO hours "¹ and a LHSV of 1.8 hours "¹ passed over the catalyst, wherein the diethyl oxalate feed is about 2.8 mole percent. The reaction is continued for 14 hours and samples of the condensed reaction product are taken every 15 minutes. The analysis of the liquid samples gives on average 34% by weight of ethylene glycol oil, 52% by weight of ethanol, 3% by weight of water, 0% by weight of diethyl oxalate and trace amounts of ethyl glycolate.

Example 7

The reactor is treated with the mixture of copper chromite and Al described in Example 5₂O₃ in the amount specified there. Di-n-butyloxalate with a sulfur content of less than 0.4 ppm and hydrogen become 200⁰C is heated, and the gaseous mixture of oxalate and hydrogen is introduced into the reactor and at a temperature of 230 ⁰C under 31.5 atmospheres of hydrogen pressure with an SV of 12 0OO hour "and a LHSV of 2.0 hour" passed over the catalyst bed. During the reaction, the release of heat of reaction is observed, bringing the temperature to about 255⁰C increased. The reaction is continued for 12 hours and samples of the condensed liquid product are removed every 15 minutes. Gas-liquid chromatography of the samples taken gives 24.6 to 27.3 weight percent ethylene glycol, 59.3 to 71.5 weight percent butanol, 0.95 to 1.76 weight percent water and traces of ethanol and butyl glycolate upon conversion of the di -n-butyloxalate of .100%.

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Example 8

The procedure described in Example 7 is repeated using the same prereduced catalyst. Reaction conditions: temperature of the catalyst bed 230 "C, 14 atmospheres hydrogen pressure, steam SV 12000 hour", LHSV 0.3 hour ", di-n-butyloxalate concentration 2.9 mol%, an exothermic reaction is carried out, the hydrogenation is continued for 1 hour, and fluid samples are taken every 15 minutes. The gas-liquid chromatographic analysis of the samples of the reaction product gives 22.5 to 2fi / 2 weight percent ethylene glycol, 53 ils € 3.5 weight percent butanol, 1j3S to 1, B1 weight percent water, J, O to 2 weight percent ethanol and Ό% by weight of unreacted inmethyl oxalate. i) The "theoretical yield of ethylene glycol and butanol of the catalytic hydrogenation of di-n-butyloxalate using stoichiometric amounts of the reactants is 2.9.5% by weight of ethylene glycol and 70.0% by weight of butanol.

Example 9

The reactor is charged with the same amount and type of pre-reduced dilute catalyst as described in Example 5. Diisobutyl oxalate with a sulfur content of less than 0.3 ppm and hydrogen become 200⁰C heated. The vaporous oxalate-hydrogen mixture is introduced into the reactor and at a catalyst bed temperature of 220 ° C⁰C is passed over the catalyst under a hydrogen pressure of 14 atmospheres at a flow rate of 12,000 hours and a fluid-related throughput rate of 3.0 hours. "The onset of the exothermic reaction raises the temperature to 260 ⁰C increased. The implementation will be 25 hours

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and samples are taken every 15 minutes of the condensed liquid product. Gas-liquid chromatographic analysis of the samples taken gives -23.9 to 27.8 weight percent ethylene glycol, 57.2 to 70.9 weight percent isobutanol, 0.90 to 1.65 weight percent Kasser, and trace amounts of ethanol and isobutyl glycolate at 100-60. percent conversion of diisobutyl oxalate.

B ice ρ ie 1 IO

using the same amount and the same kind of pre-reduced dilute catalyst as in Example 9, a diroethyloxalate melt and hydrogen to 200 ⁰C heated. The vapor mixture containing less than 0.2 ppm sulfur is introduced into the reactor and at a temperature of 225^eC was passed over the catalyst under a hydrogen pressure of 21 atmospheres at a throughput rate of 15,000 hours "and a liquid hourly flow rate of 3.0 hours". The release of heat of reaction is noted. The reaction is continued for 36 hours and samples of the condensed liquid product are taken every 15 minutes. Gas-liquid chromatographic analysis of the samples yields 36.5 to 47.3 weight percent ethylene glycol, 35.3 to 46.1 weight percent methanol, 0.48 to 1.02 weight percent water, and trace amounts of ethanol and methyl glycolate with 100 percent conversion of dimethyloxalate ,

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