NL8104804A - PROCESS FOR PREPARING ACETETHALDEHYDDIMETHYL ACETAL. - Google Patents

Description

Ν Ν.0. 30,543 1

Process for the preparation of acetaldehyde dimethyl acetal.

The invention relates to a process for preparing acetaldehyde dimethyl acetal by reacting methanol with carbon monoxide and hydrogen at elevated temperatures and pressures in the presence of a catalyst which, in addition to cobalt, contains one or more of the metals molybdenum, tungsten, uranium, chromium, vanadium, titanium and contains iron.

The subject of Dutch patent application 80.01911 is a process for preparing acetaldehyde dimethyl acetal by cobalt-catalyzed conversion of methanol with carbon monoxide and hydrogen in the presence of halogen and / or halide as a promoter at elevated temperatures and pressures, in addition to cobalt nickel in the in the form of its compounds or as a finely divided metal as a cocatalyst together with a compound of the trivalent phosphorus as a ligand. Thus, for the first time, a two-metal catalyst system was described for the recovery of acetaldehyde dimethyl-15 acetal, which has advantages over the use of cobalt alone. Although it was previously proposed to use ruthenium in the homologization of methanol in addition to cobalt, this was done in order to promote the hydrogenation reaction in addition to the homologization reaction and thus to promote the formation of ethanol and that of by-products, for example acetaldehyde, suppress ethers, esters, etc. (U.S. Patent 4,133,966).

It has now been found that, instead of nickel as a cocatalyst, it is also possible to add other metals to the cobalt with good success and to use as ligand in all metal compounds of the trivalent phosphorus, arsenic and / or anti-moon. Accordingly, the subject of the present application is a process for the preparation of acetaldehyde dimethyl acetal by cobalt-catalyzed conversion of methanol with carbon monoxide and hydrogen in the presence of halogen and / or halogen compounds as promoter at elevated temperatures and pressures, characterized in that in addition to cobalt as a nickel cocatalyst together with compounds of the trivalent arsenic and / or antimony or as a cocatalyst one or more of the metals molybdenum, tungsten, uranium, chromium, vanadium, titanium and iron together with compounds of the trivalent phosphorus, arsenic and / or use antimony as a ligand, wherein a ratio of carbon monoxide to hydrogen is between 2: 1 and 1: 3, with at most 1% by weight of cobalt and at most 5% by weight of said metals, based on used methanol , and proceeds with a ligand to cocatalyst molar ratio of 5: 1 to 1: 5 8104804 ** V -% 2.

It has also been found that not only nickel as a cocatalyst in addition to cobalt favors the conversion of methanol to acetaldehyde dimethyl acetal, but that the new principle of the two metal catalysts can be applied to a surprisingly large extent.

It is advantageous to proceed in the liquid phase with dissolved catalyst. However, the catalyst can also be used in an insoluble form, for example as a finely divided metal or on a support material. The conversion can also be carried out in the gas phase. Solvents are not required before the reaction of the invention, but can be used, for example, hydrocarbons, such as heptane, cyclohexane, toluene or also oxygen-containing solvents.

The cobalt catalyst and the said cocatalysts are advantageously used in the form of metal carbonyl compounds or in the form of suitable salts, for example, as bromide, iodides, acetates, formates or propionates, as well as other compounds which are reacted with carbon monoxide or the like. carbon monoxide and water carbonyl resp. form hydrocarbonyl complexes »

Cobalt, based on the methanol employed, is used at a maximum of 20 1% by weight, preferably at 0.01 - 0.5% by weight, while the cocatalyst is used at a maximum of 5% by weight, preferably at 0% by weight, 01 to 3% by weight, based on methanol, is used.

As ligands, in particular, compounds of the 3-value phosphorus of the formula PR1R2R3 are used, wherein R1, R25 and R3 can be, for example, alkyl, aryl or aralkyl groups. However, numerous other groups, such as bicyclic compounds, in which P is incorporated as a heteroatom, phenoxy or alkoxy groups, are also suitable for the reaction. The use of triphenylphosphine, for example, has proven advantageous. Use of the corresponding compounds of trihydric arsenic or antimony is also possible in all cocatalyst systems. Surprisingly, the disadvantages of an enhanced aldol condensation (European patent application 0.010.373) in the bimetal catalysts observed when using only cobalt-containing catalysts did not occur.

Halides, in particular hydrogen iodide or hydrogen bromide, but also metal bromides and iodides, furthermore methyl iodide or bromide, phosphonium iodide, but also elemental iodine or bromine as well as mixtures of these substances, can be used as promoters for the reaction.

40 The molar ratio of iodine and / or bromine, based on the co-catalyst 8104804 v - <9 3%, is generally 0.1 - 5. The reaction takes place in a temperature range of 180 - 230 ° C and a pressure range of about 20,000 - 50,000 kPa, but the use of even higher pressures can also be advantageous. Preferred reaction conditions are 190 - 210 ° C and 23,000 - 32,000 kPa. Carbon monoxide: hydrogen ratios are used between 2: 1 and 1: 3, the preferred ratio being 1: 1. The yield of acetaldehyde dimethyl acetal is not affected when inert components such as CO2, N2 or CH4 are present in the gas used. Therefore, the usual synthesis gas-10 grade can be used.

In operating according to the invention, the residence times required by the known methods can generally be reduced from more than 30 hours to less than two hours. Preferred residence times range from 5 minutes to 2 hours depending on discontinuous or continuous operation.

The reaction product contains only small amounts of by-products and can be worked up by distillation in the usual manner.

Example I

39.8 g (1.24 mol) of methanol, 160 mg of cobalt acetate were added to a stirring autoclave. 4 H2O, 429 mg of 57% aqueous hydrogen iodide solution, 674 mg of triphenylphosphine and 450 mg of tungsten hexacarbonyl. A mixture of carbon monoxide and hydrogen (volume ratio 1: 1) was pressed in such an amount that after reaching 200 ° C the pressure was at 30,000 kPa. Synthesis gas was forced to maintain this pressure for a reaction time of 1 hour. After cooling and working up, it was found that 56.0% by weight of the methanol used had been converted. For the organic products, selectivities from 85.5% to acetaldehyde dimethyl acetal, 6.6% to acetaldehyde, 0.7% to acetaldehyde methyl ethyl acetal, 1.0% to ethanol, 4.9% to methyl acetate and 1.3% with products with more than 2 carbon atoms. When the test was repeated with the addition of 612 mg of triphenylarsine instead of triphenylphosphine, a conversion of 56.4% by weight with a selectivity of 84.1% to acetaldehyde dimethyl acetal was achieved with a reaction time of 45 minutes.

Example II

The conversion was carried out analogously to Example I, but 338 mg of molybdenum hexacarbonyl were added instead of the tungsten carbonyl.

The conversion was 69.1% by weight of the methanol used. The selections were 66.6% to acetaldehyde dimethyl acetal, 15.1% 8104804 ** They were 4 to acetaldehyde, 5.0% to acetaldehyde methyl ethyl acetal, 4.0% to ethanol, 5.3% to methyl acetate and 4.0% to products with more than 2 carbon atoms. A repeat of the tests with the addition of 495 mg of tributylphosphine gave a methanol conversion of 64.2% by weight at a selectivity to acetaldehyde dimethyl acetal of 68.4%.

Example III

The reaction was carried out analogously to Example I, but 450 mg of chromium (III) acetylacetonate and 336 mg of triphenylphosphine were added as the second metal. The methanol conversion was at 68.2 wt% at 10, a selectivity of 69.9% to acetaldehyde dimethyl acetal. Repeating the test with 225 mg of chromium (III) acetylacetonate, the corresponding results were 68.6 resp. 66.8%.

Example IV

The conversion was carried out analogously to Example 1, but with a starting product of 336 mg triphenylphosphine and with 446 resp. 223 mg vanadium (III) acetylacetonate. The methanol conversion was 66.7 resp. 69.1 wt% for selectivities of 56.9 resp. 64.2% to acetaldehyde dimethyl acetal.

Example V

The reaction was carried out analogously to Example I, but with a starting product of 336 mg of triphenylphosphine and 168 mg of titanium (II) -acetylacetonate. A methanol conversion of 63.4% by weight at a selectivity of 63.8% to acetaldehyde dimethyl acetal was obtained. Repeating the test with 168 mg of triphenylphosphine, the corresponding results were 65.1 resp. 62.1%.

8104804

Claims (4)

A process for the preparation of acetaldehyde dimethyl acetal by cobalt-catalyzed conversion of methanol with carbon monoxide and hydrogen in the presence of halogen and / or halogen compounds as a promoter at temperatures of 180-230 ° C and pressures of 20,000-50,000 kPa, characterized by, that in addition to cobalt, nickel is co-catalyst together with compounds of the trivalent arsenic and / or antimony or as a cocatalyst one or more of the metals molybdenum, tungsten, uranium, chromium, vanadium, titanium and iron together with compounds of the Trivalent phosphorus, arsenic and / or antimony is used as the ligand, with a carbon monoxide to hydrogen ratio of between 2: 1 and 1: 3, with at most 1% by weight of cobalt and at most 5% by weight of said metals based on methanol used, and proceeds with a ligand to cocatalyst molar ratio of from 5: 1 to 1: 5. 2. Process according to claim 1, characterized in that salts of cobalt and the cocatalyst which are soluble in the reaction medium are used. 3. Process according to claims 1 and 2, characterized in that the process is carried out with 0.01 - 0.5% by weight of cobalt, based on the methanol used. 4. Process according to claims 1 to 3, characterized in that 0.01-3% by weight of cocatalyst, based on used methanol, is used. 25 ===== \ 8104804