NZ204467A - Process for preparing alcohols - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £04467 <u 204467 Priority Date(s): 4 Complete Specification Filed: 8v>.-Class: p. XQ3.C31; f 18 NOV me' Publication Data: .....

P.O. Journal, No: .1.3."?"?.* kik NEW ZEALAND PATENTS ACT, 1953 No.: Date: COM PLETE SPECIFIC ATI ON fe- PROCESS FOR PREPARING ALCOHOLS A. 3. p. & S. i>er,.;.4UA....

J/We, UNION CARBIDE CORPORATION, manufacturers, a corporation organized under the laws of the State of New York,Alocated at Old Ridgebury Road, Danbury, State of Connecticut, 06817, United States of America hereby declare the invention for which X / we pray that a patent may be granted to oik/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- - 1 (followed by page la) 2044 6 i=«- Process for preparing alcohols This invention relates to a process for preparing an alcohol or alcohols from a dialkyl carbonate.

A dialkyl carbonate is by-produced in. for example, a reaction process in which such a dibasic acid ester as an ester of oxalic acid, which is useful as a starting material for various kinds of compounds, is produced. Dialkyl carbonate, however, has little industrial application. Therefore, at present, a dialkyl carbonate, which is by-produced in such a manner, is converted into an alcohol corresponding to the alkyl group by hydrolysis or subjected to waste treatment by burning.

Although through hydrolysis, the carbon component contained in the alkyl group of a dialkyl carbonate can be utilized effectively as a recovered alcohol, the carbon component contained in the carbonic acid group becomes carbon dioxide and hence can not be utilized effectively. Further, burning the dialkyl carbonate does represent an effective utilization of industrial sources, and generates waste gas.

A primary object of this invention is to utilize effectively a dialkyl carbonate by converting each of the carbon components to those which can be used effectively.

Another object of this invention is to enhance the efficiency as a whole of various reaction processes by providing a process capable of converting a dialkyl carbonate, which is by-produced in a reaction process for preparing a dibasic acid D 13,978 204467 ester and the like, into an alcohol corresponding to the alkyl group and methanol.

The above mentioned objects can be accomplished by this invention, that is, a process for preparing an alcohol or alcohols which comprising heating a dialkyl carbonate in the presence of a copper-containing catalyst in an atmosphere of hydrogen to produce an alcohol corresponding to the alkyl group and methanol.

This invention is explained in detail below. The reaction utilized in this invention is novel and processes in accordance with this invention can effect the reaction at advantageous rates in the presence of effective amounts of a copper-containing catalyst.

The copper-containing catalyst used in this invention is not limited in particular. The copper-containing catalyst used in this invention may contain, besides the copper, one or more metal components. Preferably, the other metal component is provided in an amount of 0 to 30. say, 0 to 20, mole percent based on copper. As examples of such metal components, there may be mentioned chromium, aluminum, barium, zinc, nickel, palladium, silver, titanium and the like.

Illustrative examples of the copper-containing catalyst which may be used in this invention include copper catalyst, copper-chromium catalyst, copper-zinc catalyst, copper-chromium-zinc catalyst, copper-chromium-barium catalyst, copper-aluminum catalyst, copper-silver catalyst, copper-palladium catalyst and the like.

Various kinds of carriers or supports for the copper-containing catalyst may optionally be employed. Examples of such carriers include silicon dioxide, titanium dioxide, lanthanum oxide. zirconium oxide, activated carbon and the like.

There is no particular limitation to the size and the shape of the catalyst, and the catalyst may be employed after be">ng suitably shaped or granulated in a desired size and shape such as rods, pellets, and granules.

Preferred copper-containing catalysts used in this invention may be prepared by, for example, the following method.

A water-soluble copper salt (e.g. cupric nitrate) is dissolved in water. Thereto is added a concentrated aqueous ammonia until the pH of the solution reaches at least about 10. Thus, the solution provides blue color. To the blue-colored solution is added a colloidal silica sol. and the mixture is stirred at room temperature or under heating to form in situ copper ions supported on silica gel. After evaporation of the solution to dryness, the residue is washed sufficiently with water (e.g.. until the filtrate becomes transparent) and then dried again, followed by reduction treatment of the thus obtained catalyst supported on a carrier. The reduction treatment may be by. for example, providing the supported catalyst in a stream of hydrogen at a temperature of about 150° to about 500°C. A copper catalyst which has been dispersed uniformly on silica can be prepared by this method. This copper catalyst may be employed for the reaction of this invention in the same manner as in conventional catalytic reactions.

In the above-mentioned procedure the silica gel-containing solution may be concentrated to recover the solid catalyst rather than evaporated to dryness. For instance, the solution may be subjected to evaporation operation so that its volume may be reduced to a half thereof and a solid may be removed from the concentrate by suitable means such as filtration. The recovered solid may be treated by the same procedure as in the above-mentioned operation to obtain the desired copper catalyst.

Alternatively, similar copper catalyst may be obtained also by using a silica gel having an average particle size of, for instance, about 1 my. to about 200 my. in place of the silica sol mentioned above.

The evaporation of the solution to obtain thei solid catalyst may conveniently be carried out either under atmospheric pressure or under reduced pressure. Further, the treatment may be conducted either at room temperature or preferably at an elevated temperature, for instance, at about 60° to 90°C.

Optionally, the solid catalyst may be calcined at a temperature of about 300° to 800°C in an air for several hours prior to the reduction treatment mentioned above.

The following procedure illustrates one type of procedure suitable for preparing a copper-chromium-zinc catalyst to be used for the reaction according to this invention. 204467 A water-soluble copper salt (e.g. cupric nitrate) and a water-soluble zinc salt (e.g. zinc nitrate) are dissolved in water. Thereto is added such a chromic acid salt as ammonium chromate to obtain a compound composed of copper, chromium and zinc, or a precipitate of the mixture thereof, followed by filtration and sufficient washing with water so that the filtrate becomes transparent. Subsequently, the product is dried in an air at about 100° to about 200°C. and the dried product is carefully decomposed at a temperature of about 300° to about 500°C to obtain the desired copper-chromium-zinc catalyst. Then, the catalyst is reduced at a temperature of about 150° to about 500°C for several hours in a stream of hydrogen, and is employed as the catalyst for the reaction according to this invention.

While, in each reaction for preparing a catalyst mentioned above, cupric nitrate has been exemplified as the starting material for the copper component also include for instance, metallic copper or various copper compounds (preferably water-soluble compounds) such as copper acetate, copper oxalate, copper formate, cuprous chloride, cupric chloride and complexes of copper.

In cases where other metal components are incorporated in the copper-containing copper according to this invention, these metal components may be introduced into the catalyst in the form of a metal per se or of various kinds of metal compounds (preferably water-soluble ones) such as a nitrate, an acetate, an oxalate, a formate, a chloride and a complex compound.

D-13,970 204467 The reaction according to this invention can be practiced by reacting various kinds of dialkyl carbonates with hydrogen in the presence of a copper-containing catalyst. The dialkyl carbonate used in this invention is a compound represented by the following formula: (R10)C0(0R2) 1 2 wherein R and R each represent an alkyl group. 1 2 and R and R may be the same or different.

The alkyl group represented by R1 and 2 R in the above formula is not limited, and may include preferably an aliphatic alkyl group, most preferably an aliphatic alkyl group having up to 6 carbon atoms such as methyl, ethyl, n-propyl. isopropyl. n-butyl. isobutyl. tert-butyl. n-pentyl. isopentyl. n-hexyl and isohexyl.

Illustrative of the dialkyl carbonates employed as the starting material in this invention 1 2 are dialkyl carbonates in which R and R are the same and each has not more than 6 carbon atoms. such as dimethyl carbonate, diethyl carbonate. di-n-propyl carbonate, diisopropyl carbonate. di-n-butyl carbonate, diisobutyl carbonate. di-tert-butyl carbonate, di-n-pentyl carbonate. diisopentyl carbonate, di-n-hexyl carbonate and diisohexyl carbonate; a dialkyl carbonate in which 1 2 R and R are different from each other and each has not more than 6 carbon atoms, such as ethyl methyl carbonate and isopropyl methyl carbonate; and the like.

D 13,978 2044 The reaction according to this invention is usually practiced by passing dialkyl carbonate and hydrogen through a reaction vessel packed with the copper-containing catalyst.

The reaction temperature and pressures employed are sufficient to form the desired alcohol products. The reaction temperature may preferably be in the range of about 100° to about 300°C. Particularly preferable reaction temperatures are in the range of about 160°C to around 220°C.

The reaction pressure may preferably be in the range of about 0.5 to about 100 atmospheres (atm.) absolute. Particularly preferred reaction pressures are in the range of about 1 to about 30 atm. absolute. The space velocity (based on the volume of catalyst) for the supply of the above-mentioned starting material may preferably be in the range of about 500 to about 100.000 hr""1. Particularly preferred space velocities are in the range of about 1.000 to about 20.000 hr-1. The ratio of hydrogen and the dialkyl carbonate to be supplied (molar ratio: hydrogen/dialkyl carbonate) may preferably be in the range of about 3 to about 300. Particularly preferred molar ratios of hydrogen/dialkyl carbonate to be supplied are in the range of about 10 to about 100.

The. reaction according to this invention can produce the desired alcohols in particularly high yield.

The alcohols produced by the reaction according to this invention are. in principle, methanol and an alcohol corresponding to the alkyl D 13i978 2 044 6 dLoWc*^- $group in the -dirfmethyi- carbonate. Accordingly, in 'Cases where-diiuelfly'l" carbonate is used as the J3 . , starting dialkyl carbonate, the produced alcohols are substantially a mixture of methanol and ethanol.

According to thi6 invention as described above, a dialkyl carbonate, which is by-produced in, for instance, a reaction process for preparing a dibasic acid ester such as an ester of oxalic acid and has never been utilized effectively; can be converted into the starting alcohol and methanol by means of a method which can easily be carried out on an industrial scale. The alcohol produced by the conversion can be recycled and employed, for instance, to prepare dibasic acid esters and may also be utilized for other applications. Therefore. this invention is very advantageous from the view point of reutilization of starting materials and reduction of waste materials.

In the following Examples the conversion (reaction rate) of a dialkyl carbonate is meant to be a value obtain by calculation according to the following: Conversion of dialkyl carbonate (%) = [(mole number of consumed dialkyl carbonate)/(mole number of supplied dialkyl carbonateljx 100 The selectivity to an alcohol means a value obtained by calculation according to the following: In cases where dimethyl carbonate is used as the starting material Selectivity to methanol (%) = [(mole number of produced methanol * ^/(mole number of consumed D 13.978 dimethyl carbonate)] x 100 In cases where diethyl carbonate is used as the starting material Selectivity to methanol (%) = [(mole number of produced methanol/(mole number of consumed diethyl carbonate)] x 100 Selectivity to ethanol (%) = [(mole number of produced ethanol * 2/(mole number of consumed diethyl carbonate)] x 100 Example 1.

In 1500 ml of water was dissolved 506 g of cupric nitrate trihydrate [Cu(N03)2 * 3HzO]. and thereto was added further 1500 ml of a conc. aqueous ammonia to adjust the pH of the solution to around 11 - 12, whereby a deep blue solution containing a copper-'amine complex was obtained.

With the deep blue solution thus obtained was mixed 666 g of a colloidal silica sol (silica content: 30 % by weight) and the mixture was stirred at room temperature for several hours. Subsequently, the temperature of the mixed solution was raised up to 80 to 100°C to evaporate the major portion of the water, whereby a solid having copper ions supported on silica was obtained. The thus obtained solid was then dried at 120°C for 16 hours. Next, the dried product was washed sufficiently with water until filtrate became transparent and then dried again at 120°C for 24 hours. Then, the dried product was shaped into pellets having a size of 5 mm x 5 mm (in diameter) and calcined in an air at 750°C for 5 hours followed by pulverization to particles being 9 - 16 mesh. This pulverized product was subjected to D 13i978 '044 reduction treatment at 200°C for 5 hours in a stream of hydrogen to give a copper-supporting catalyst. The content of copper in the catalyst was around 40% by weight.

After reduction treatment, 10 ml of the catalyst was charged into a stainless steel tubular reactor having an inner diameter of 8 mm and a length of 20 cm. Dimethyl carbonate, which had been vaporized in an oven maintained at around 200°C was supplied to the tubular reactor together with the hydrogen gas under the following conditions: liquid space velocity (LHSV): 0.56 g/ml. hr space velocity (SV): 3,000/hr ratio of H2/dimethyl carbonate supplied (molar ratio): 21.5 to carry out the hydrogenolysis reaction of the dimethyl carbonate at a reaction temperature of 2 200°C under a reaction pressure of 3.0 kg/cm G.

After the produced gas coming out of the reactor was passed through a reducing valve which had been heated at around 150°C, it was collected in two hose-type traps connected in series, which had been cooled with dry ice-methanol. Then, the collected liquid was analyzed by gas chromatography (column temperature: 40°C, stationary phase: DEGS. 2 m) to determine the amount of the components contained in the produced gas.

The results obtained are as follows: Conversion of dimethyl carbonate = 97.7% Selectivity to methanol = 90.4% Example 2.

After the catalyst, which had been prepared D-13.970 in Example 1 and subjected to reduction treatment, was charged into a tubular reactor in the same manner as in Example 1. the same procedure as in Example 1 was followed except that the conditions for the hydrogenolysis reaction of dimethyl carbonate were changed as follows: reaction temperature = 190°C 2 reaction pressure: = 3.0 kg/cm G. liquid space velocity = 0.64 g/ml. hr. space velocity: = 6,000/hr.

H2/dimethyl carbonate (molar ratio): 37.5 The results obtained are as follows: Conversion of dimethyl carbonate = 82.6% Selectivity to methanol = 92.3% Example 3.

After the catalyst, which had been prepared in Example 1 and subjected to reduction treatment, was charged into a tubular reactor in the same manner as in Example 1. the same procedure as in Example 1 was followed except that the conditions for the hydrogenolysis reaction of diethyl carbonate were changed as follows: reaction temperature = 200°C 2 reaction pressure: =3.0 kg/cm G. liquid space velocity = 0.72 g/ml. hr. space velocity: = 6.000/hr.

H2/diethyl carbonate (molar ratio): 43 H The results obtained are as follows: Conversion of diethyl carbonate = 98.7% Selectivity to ethanol = 100% Selectivity to methanol = 75.3% D-13.970 204467 Example 4.

After the catalyst, which had been prepared in Example 1 and subject to reduction treatment, was charged into a tubular reactor in the same manner as in Example 1. the same procedure as in Example 1 was followed except that the conditions for the hydrogenolysis reaction of diethyl carbonate were changed as follows: reaction temperature = 180°C 2 reaction pressure: = 3.0 kg/cm G. liquid space velocity = 0.35 g/ml. hr. space velocity: = 6,000/hr.

H2/diethyl carbonate (molar ratio): 90 The results obtained are as follows: Conversion of diethyl carbonate = 88.2% Selectivity to ethanol = 106% Selectivity to methanol = 62.1% In the above results, the selectivity to ethanol exceeds 100%. Such results are believed to be due to the carbon atom being converted into ethanol by reactions such as dimerization. reduction and the like. Thus ethanol from this source is in addition to the ethanol derived from the ethyl group in the diethyl carbonate. While the similar results appear in the following Examples, the reason for such phenomenon may be considered to be the same as above.

Example 5.

In 300 ml of water was dissolved 33 g of D 13^078 2 04467 cupric nitrate trihydrate [Cu(N03)3 ' 3HzO]. and thereto was added further 385 ml of conc. aqueous ammonia to adjust the pH of the solution to around 11. whereby a deep blue solution containing a copper-t±m±2m_complex was obtained. With the deep blue solution was mixed 170 g of a colloidal silica sol (silica content: 30% by weight), and the mixture was stirred at room temperature for several hours. Subsequently, the temperature of the mixed solution was raised up to 80 to 100°C to evaporate the major portion of the water, whereby a solid having copper ions supported on silica was obtained. The thus obtained solid was then dried at 120°C for 16 hours. Next, the dried product was washed sufficiently with water until the filtrate became transparent and then dried again at 120°C for 24 hours. Then, the dried product was subjected to reduction treatment at 300°C for 2.5 hours in a stream of hydrogen to give a copper-containing catalyst. The content of copper in the catalyst was around 10%.

After reduction treatment, 10 ml of the catalyst was taken and filled in a stainless steel tubular reactor having an inner diameter of 8 mm and a length of 20 cm and an experiment was run according to the same procedure as in Example 1 except that the conditions for the hydrogenolysis reaction of diethyl carbonate were changed as follows: reaction temperature = 200°C 2 reaction pressure: = 3.0 kg/cm G. liquid space velocity = 0.76 g/ml. hr.

D-13.070 204467 space velocity: = 6.000/hr.

H2/diethyl carbonate (molar ratio): 40 The results obtained are as follows: Conversion of diethyl carbonate = 39.0% Selectivity to ethanol = 104% Selectivity to methanol = 35.0% Example 6.

In 100 ml of water was dissolved 3.8 g of cupric nitrate trihydrate [Cu(N03)2 * 3 H20], and thereto was added further 12 ml of conc. aqueous ammonia to adjust the pH of the solution to around ?\l 11. whereby a deep blue solution containing a w- J'Oun\rn\f)Q' oJ0^ copper-^ajoMwr complex was obtained. With the deep blue solution thus obtained was mixed 20 g of silica gel (manufactured by Fuji-Devison Co.. Ltd: A type) and the obtained dispersion was stirred overnight at room temperature. In this procedure, the copper-amine complex caused cation exchange reactions with the hydroxyl groups on the surface of the silica gel so that the copper component was supported on the silica gel. After the blue colored copper-supporting catalyst was removed from the mixture and washed sufficiently with water until the filtrate became transparent, it was dried at 140°C for 14 hours. Then, the dried product was subject to reduction treatment in a stream of hydrogen at 300°C for 2.5 hours to prepare a supported copper catalyst. The content of copper in the catalyst was around 5% by weight.

After reduction treatment. 10 ml of the catalyst was charged into a stainless steel tubular D* 13,970' reactor having an inner diameter of 8 mm and a length of 20 cm. and the conditions for the hydrogenolysis reaction of diethyl carbonate were changed as follows: reaction temperature = 200°C 2 reaction pressure: = 3.0 kg/cm G. liquid space velocity = 0.38 g/ml. hr. space velocity: = 6.000/hr.

H2/diethyl carbonate (molar ratio): 77 The results obtained are as follows: Conversion of diethyl carbonate = 16.2% Selectivity to ethanol = 67.9% Selectivity to methanol = about 5.0% Examples 7 to 9.

In 220 ml of water was dissolved 24.2 g of cupric nitrate trihydrate [Cu(NC>3)2 * 3 H20]. Separately. 29.7 g of zinc nitrate [Zn(N03)2 " 6H20] was dissolved in 270 ml of water. Further separately. 15.2 g of ammonium chromate t(NH4)2Cr04] was dissolved in 140 ml of water.

First, the cupric nitrate solution was mixed with the zinc nitrate solution, and thereto was added the ammonium chromate solution to form a brown precipitate. To the resulting solution containing the precipitate, there was added conc. aqueous ammonia to adjust the pH to around 7. After the precipitate-containing solution was stirred at room temperature for 1.5 hours, the precipitate was collected by filtration. Subsequently, the thus separated precipitate was dried at 120°C for 15 hours.

D 13,978 2 044 Next, the thus obtain dried product was introduced in portions in a vessel maintained at a temperature of around 400°C to conduct its pyrolysis. By the pyrolysis, the color of the dried product was changed from brown to black. Then, the black-colored pyrolized product was subjected to reduction treatment in a stream of hydrogen at 200°C for 5 hours to prepare a copper-chromium-zinc catalyst. The contents of copper, chromium and zinc as metal in the catalyst were as follows: catalyst was charged into a stainless steel tubular reactor having an inner diameter of 8 mm and a length of 20 cm. and an experiment was run according to the same procedure as in Example 1 except that the conditions for the hydrogenolysis reaction of diethyl carbonate were changed as follows: Cu: 22.3% by weight Cr: 54.8% by weight Zn: 22.9% by weight After reduction treatment. 5 ml of the reaction temperature reaction temperature reaction temperature reaction pressure: = 180°C (Example 7) = 190°C (Example 8) = 200°C (Example 9) 2 = 6.0 kg/cm G. liquid space velocity space velocity: = 0.4 g/ml. hr. = 10.000/hr.

H2/diethyl carbonate (molar ratio): 130 The results obtained are shown in Table 1.

D 13 i 9 7 8* 204467 Example No. 7 8 9 Table 1 Conversion of Selectivity diethyl carbonate (%) 32.2 95.3 100.0 to ethanol % 91.2 102.0 103 .0 Selectivity to methanol % 17 .2 64.9 61.3 Examples 10 to 12.

CuO-ZnO catalyst (manufactured by Nikki Kagaku Kabushikikaisha, Japan, tradename: N211. atomic ratio of Cu : Zn = 1 : 0.905) was pulverized into 9 mesh particles and subjected to reduction treatment in a stream containing 15% by volume of hydrogen at 200°C for 6 hours.

After reduction treatment. 5 ml of the catalyst was charged into a stainless steel tubular reactor having an inner diameter of 8 mm and a length of 20 cm. and an experiment was run according to the same procedure as described in Example 1 except that the conditions for the hydrogenolysis reaction of diethyl carbonate were changed as follows: reaction temperature reaction temperature reaction temperature reaction pressure: liquid space velocity space velocity: = 200°C (Example 10) = 210°C (Example 11) = 220°C (Example 11) 2 = 3.0 kg/cm G. = 0.4 g/ml. hr. = 10,000/hr.

H2/diethyl carbonate (molar ratio): 130 The results obtained are shown in Table 2.

D 13,978

Claims (13)

204467 - 18 - Table 2 Conversion of Selectivity Selectivity Example diethyl to ethanol to methanol No. carbonate (%) % % 10 23.3 143.0 10.2 11 58.9 125.0 32.5 12 100.0 126.0 43.7 D 13 i 9~M. 204467 - 19 - \ VaV~SCJX VM "^Vc^rrv \ "S>'. Cldla^'

1. A process for preparing an alcohol or alcohols which comprises heating a dialkyl carbonate represented by the formula: (R10)CO(OR2) 1 2 wherein R and R each represent an alkyl group, 12 I and R and R may be the same or, different, in the presence of a copper-containing catalyst in an atmosphere of hydrogen to prepare an alcohol corresponding to the alkyl group in the dialkyl carbonate and methanol.

2. The process according" to Claim 1 where said alkyl group has up to 6 carbon atoms.

3. The process according to Claim 2 where said alkyl group is a methyl group or an ethyl group.

4. The process according to Claim 1 wherein said copper-containing catalyst is selected from the group consisting of a copper catalyst, a copper-chromium catalyst, a copper-zinc catalyst, a copper-chromium-zinc catalyst, a copper-chromium-barium catalyst, a copper-aluminum catalyst, a copper-silver catalyst and a copper-palladium catalyst.

5. The process according to Claim 1 wherein said copper-containing catalyst is supported on a carrier.

6. The process according to Claim 5 wherein said carrier is selected from the group 204467 - 20 - \ consisting of silicon dioxide, titanium dioxide, lanthanum oxide, zirconium oxide and activated carbon.

7. The process according to Claim 1 wherein the reaction is carried out by passing dialkyl carbonate and hydrogen through a reaction vessel packed with the copper-containing catalyst.

8. The process according to Claim 1 wherein the reaction is conducted at a temperature of 100° to . 300°C.

9. The process according to Claim 1 wherein the reaction is conducted at a pressure of - 0.5 to 100 atmospheres absolute.

10. The process according to Claim 6 wherein said dialkyl carbonate and hydrogen is supplied at a space velocity of , 500 to 100,000 hr"1.

11. The process according to Claim 1 wherein the molar ratio of hydrogen/dialkyl carbonate is in the range of 3 to j 300.

12. A process as claimed in any one of the preceding claims when performed substantially as hereinbefore described with reference to any example thereof. ^

13. An alcohol or alcohols produced, by a process as claimed in any one of the preceding claims. ''V 12JUL1985mj By H4a/Their authorised Agent A. J. PARK & SON Per: "foe/.