DE904527C - Dehydrogenation catalyst - Google Patents

Description

Dehydrogenation catalyst The invention relates to a dehydrogenation catalyst, which is particularly suitable for the production of ketones from secondary alcohols, and a method for producing such a catalyst.

It is well known that the elimination of hydrogen from secondary Alcohols, which leads to the corresponding ketones, can be obtained by that one leads the alcohols at elevated temperature over substances that act as dehydrogenation catalysts works. In the early stages of development in this field, metals such as copper were used or brass, is used. These catalysts have the disadvantages of short life and that they require high working temperatures. A little later have hard reducible Metal oxides, such as zinc, cerium, magnesium oxide, etc., of considerable importance as obtained hydrogen-releasing catalysts. Different combinations of catalytic Effective metals and difficult to reducible metal oxides are also available from time to time been applied. It has been shown that difficult to reducible metal oxides do not cause only hydrogen, but also dehydration and that as a result of the dehydrating Effect considerable amounts of olefins are produced from the alcohol, which increases the overall yield reduced to ketone. In order to suppress these side reactions as much as possible, in In connection with the difficult to reduce oxide catalysts, additives such as carbonates and hydroxides of alkalis and alkaline earths have been used. If such additives were used, it was found, however, that they the thermal stability of the catalyst affect and thereby reduce its service life and its sensitivity increase against catalyst poisons.

It is an object of the invention to improve the effectiveness of catalysts from metal oxides that are difficult to reducible, such as magnesium, zinc and beryllium oxide, as water Substance-releasing catalysts, especially for Splitting off of hydrogen from compounds containing secondary alcohol groups, to increase.

Another aim of the invention is the stability of catalysts from difficult to reducible metal oxides at high temperature. Another The aim is to increase the resistance of these catalysts to toxins and thus extending their service life.

In the dehydrogenation of alcohols using the new catalyst by-products are obtained which are relatively pure, i.e. H. free of ethers, hydrocarbons, Resins, etc. Still other advantages of the invention will become apparent from the following description recognizable.

The process of the invention, in its general form, consists in preparing a catalyst composed in large part of an oxide of magnesium, zinc or beryllium and in minor part of an oxide of zirconium, cerium or thorium. The latter oxides are present in amounts of 1 to 1 weight percent, preferably 6 to 12 weight percent, based on the weight of the total oxides. It has been found that 1 to 1 4 percent by weight of at least one of the oxides of zirconium, cerium and thorium, based on the total weight of the catalyst mixture, considerably increases the effectiveness of the magnesium, zinc or beryllium oxide as a dehydrogenation catalyst. The catalyst is particularly effective in the dehydrogenation of compounds of the general formula where R is an alkyl, aryl, alkylaryl, arylalkyl or a ring-shaped alkyl radical and R1 can be hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or a ring-shaped alkyl radical, e.g. B. a methyl, ethyl, propyl, phenyl, benzyl, methylphenyl or cyclohexyl group.

The improvement that can be achieved when one is less than I. 01o zirconium, cerium or thorium oxide or their mixtures used is probably measurable, but not sufficient to be of practical importance while improving, which can be achieved when using more than I5 01o of these oxides, with 6 to 12 ole achievable improvement does not sufficiently surpass the additional Justify costs.

It has also been shown that catalysts of the types described can be further stabilized by, based on the weight of the zirconium, Cerium or thorium oxide, 6 to 10% of a stabilizer added, which is made of iron oxide, Silicic acid or aluminum zinc oxide consists.

The catalyst made from zinc oxide, magnesium oxide or beryllium oxide and one of the oxides of zirconium, cerium or thorium was made high effectiveness in the dehydration of pure secondary alcohols and primary Low molecular weight alcohols. As in dehydration processes, as a rule no pure raw materials are processed, other metal oxides are dem activated zinc oxide catalyst added to the perishable influence of impurities on alcohols that resinify or char under the conditions of dehydration, to eliminate. The catalyst made from the two oxides is deposited by deposition inactivated by resin or carbon, if one does not also use small amounts of SiO2, Add A1203 or Fe2O3. Primary alcohols with more than 6 carbon atoms and polymeric olefins lead to the inactivity of the catalyst if they are used as impurities are present in the alcohol to be dehydrated.

Production of the catalyst The production of the catalyst according to the invention is illustrated below using the example of a zinc oxide-zirconium oxide catalyst shown.

Various types of zirconia or zirconia can be used in the preparation of a zirconium-containing catalyst in accordance with the present invention. Typical analyzes of some suitable grades of zirconia follow: Commercial standard Usual chemical and electrical patterns Too pure for merged spectro- setting copy % ZrO2 to to to to to 87.97 99.37 97.10 99.943 % SiO2 ....... 8.49 0.30 1.88 0.020 % Al2O3 ..... 0.38 0.08 0.52 0.005 01o MgO. 0.30 0.05: 0.05 0.005 % Na2O (as silicate) 1.50 0.02 0.02 0.002 % TiO @ ..... 0.30 0.15 0.30 0.005 0 / o Fe203 .... o, o8 0.03 1 0, II 0.020 It has been found that the catalytic effect of the zirconia added to the oxides of zinc, magnesium or beryllium is due to the zirconia itself and not to the impurities it contains. This was proven by an experiment in which pure zirconium oxide was used as an additive to zinc oxide. In preparing the catalyst it is preferred to mix the oxides in the desired proportions in powder form and then incorporate enough water into the mixture to obtain a pulp of the approximate consistency of thick cream. This generally requires a volume of water approximately as large as that of powder. A carrier mass is then coated with the catalyst slurry.

This can be done by putting the support material in a mixing drum or similar device introduces, poured over with the catalyst slurry and then rotated until a uniform thick mixture is obtained. the Mixture is placed in an oven at about 80 ° and dried. Requires drying about 24 to 48 hours.

Metal chips can be used as a catalyst carrier Find, although pumice stone in granular or pill form and also other types of carriers, which are common and well known can be used.

Pumice stone and metal shavings are preferred as supports, and among the Metal shavings, steel and brass shavings are preferred.

Catalytic Dehydrogenation The catalyst of the invention is useful especially for the dehydration of secondary alcohols such as isopropyl alcohol, secondary Butyl alcohol, secondary amyl alcohol, to the corresponding ketones. The transformation Converting secondary alcohols to ketones is accomplished by taking the alcohol in vapor form can be passed through a tube filled with the catalyst that extends to about 200 to 550 °, preferably 315 to 480 °, the pressure being I to 2 atmospheres and the throughput 0.5 to 10 volumes, preferably 1.5 to 3 volumes, more fluid Alcohol per volume of catalyst per hour. The one during the reaction preferably pressure used is maintained between atmospheric and approximately 0.68 atmospheres. Higher pressures are not desirable because decomposition reactions occur at higher temperatures become more noticeable. The gaseous reaction product is passed through a condenser led in which the ketone and the unchanged alcohol condensed and of which less easily condensable gas, which consists mainly of hydrogen and to a small extent consists of olefinic hydrocarbons.

The alcohol used for the dehydration process can be up to 10 to Contain I2% water without seriously affecting the dehydration to ketone will. The main by-product that occurs in the dehydrogenation of secondary alcohols produced by means of the catalyst according to the invention has been found to be a ketone of high molecular weight and quite high purity. The mixture of by-products, which is usually obtained in the dehydrogenation of secondary alcohols is thus at Use of the catalyst of the type described is well-defined and easily separable. The formation of other by-products such as B. of ethers, hydrocarbons and polymeric hydrocarbon resins, is practically prevented. The main one By-product of the dehydrogenation of isopropyl alcohol to acetone, has been identified as mesityl oxide while that in the conversion of secondary By-product of butanol to methyl ethyl ketone as a ketone with 8 carbon atoms has been recognized in which 3-methylhepten-4-one-5 predominates. Small amounts of methylheptanone-3 and ethylhexanone-2 were identified in the latter by-product.

The following examples are given for illustrative purposes only and are not intended to limit the invention, serve to improve the effectiveness of what is described Catalyst for the dehydrogenation of secondary alcohols under the specified conditions to show. The examples show the effectiveness of the catalyst in terms of its Activity at high throughput, its thermal stability, favorable reaction temperature, long life and resistance to toxins.

Effectiveness of the catalyst In the following table are test results compiled, the effectiveness of zinc oxide-zirconium oxide, zinc oxide-cerium oxide and zinc oxide-thorium oxide catalysts show in the dehydration of alcohols.

Table I I. Dehydrogenation of isopropanol (91 to 99 ° / 0) over 94% ZnO, 6 0 / o ZrO2 (chemically pure) % Conversion to Test throughput temperature% acetone No. V / V / St. ° C Conversion of mesityl Acetone olefin yield oxide 34 I, 5,400 98.2 88.6 7.84 I, 78 90.2 37 I, 5,480 95.8 84.6 6.95 4.2 I 88.5 40 3.0 480 99.8 9I, 2 6.46 2, I6 9I, 2 39 6, o 400 86.3 83.6 2.22 0.52 96.9 4I I, 5,192.3 82.4 7.88 1.99 89.3 3I I, 5,400 95.4 85.6 9, I4 o, 69 89.7 35 I, 5,480 99.4 88.3 i 8.49 2.62 88.8 Experiments No. 3I, 34 and 35 with gI% isopropanol, otherwise gg0 /, ig.

2. Dehydration of 6% secondary butanol over 94% ZnO, 6% ZrO2 (chemically pure) Experiment throughput temperature% alcohol Ethylamylen-% yield of methylethyl No. V / V / St. ° C conversion ketone olefin ketone 43 I, 5,400 88.2 4.18 3.5 gI, o 44 6, o 400 48.8 o, 69 0.63 97.0 45 3.0 480 93.8 I, 83 2.0 96, o 46 1.5 400 38.0 2.3 I, 8 -90.2 3. Dehydration of 99% secondary butanol over 94% ZnO, 6% CeO2 Attempt throughput temperature% alcohol% yield No. V / V / St. ° C conversion ethylamylene olefin methyl ethyl ketone ketone 58 A 1.5 400 94.6 0.24 0.1 99.6 58 B 6, o400 83.7 0.98 0.4 98.8 58 C 3.0 480 90.6 I, 3 0.6 98.2 58 D 1.5 400 60, I5 I, 6I 1.8 96.7 4. Dehydration of 99% secondary butanol over 94% ZnO, 6% ThO2 Experiment throughput temperature% alcohol- ° jO yield Ethylamylenemethylethyl No. V / V / St. ° C conversion olefin ketone ketone 61 A 1.5 400 88.1 8.0 1.91 90.1 61 B 6, o 400 7I, 0 I, 61 0.84 97.7 61 C 3.0 480 91.5 1.42 2.34 96.0 61 D 1.5 400 62.2 I, 7 3.5! 94.8 5. Dehydration of 99% secondary butanol over 94% MgO, 6% ZrO2 (chemically pure) Conversion to Attempt throughput temperature yield No. V / V / St. ° C mole percent Mole mole percent 114 1.5 400 methyl ethyl ketone ... 6.166 64.2 96.6 9.49 moles of ethyl amylene ketone. 0.084 0.87 1.3 sec. BuOH C4 olefin ........... 0.144 1.5 2.25 6. Dehydration of 10% isopropanol over 94 01o MgO, 6% ZrO2 (chemically pure) Conversion to Attempt throughput temperature yield No. V / V / St. ° C mole percent Mole mole percent 115 1.5 400 acetone ............ 6.042 51.0 91.6 11.7 moles of mesityl oxide .......... 0.059 0.49 0.88 Isopropanol C3-olefin ......... 0.578 4.8 8.62 Polymer ....................... 0.023 0.19 0.34 Stability at elevated temperature and service life of the catalyst In order to test the stability of the catalyst at elevated temperature, tests were carried out, each lasting 5 hours, at a temperature of 400 ° and a throughput of 1.5, then at a temperature of 400 ° and a throughput of 6, o, further carried out at 4800 and a throughput of 3.0, finally again at 4000 and a throughput of 1.5.

The test results in Table II demonstrate the stability of the catalyst at high temperature.

From the tests with respect to the service life it is found that the used Catalyst would work 3 to 6 months without regeneration. The trials also show the stability of the catalyst over a wide temperature range.

Table II Experiment No. 79 Catalyst 94 01o ZnO, 6 0 /, ZrO2 (of the commercial grade mentioned above) ABCD Starting material: 99% isopropanol Duration of experiment, hours .................. o to 5 5 to 10 10 to 15 15 to 20 Throughput V / V / St. ........................ 1.5 6.0 3.0 1.5 Temperature, ° C ........................... 400 400 480 400 Mole percent alcohol too Acetone ................................ 87.0 55.8 82.4 5I, 7 Isopropanol ............................. 5.43 40.6 8.18 41.4 C3 olefin ........ 2, 15 0.67 7.56 5.23 Mesityloxyd ........................... 5.43 2.91 1.81 1.59 % Yield acetone .................... 92.0 94.0 89.8 88.2 Experiment No. 80 Catalyst *) 94% ZnO, 6% ZrO2 Starting material: 99% secondary butanol Duration of experiment, hours .................. o to 5 5 to 10 10 to 15 15 to 20 Throughput V / V / St. ........................ 1.5 6.0 3.0 1.5 Temperature, ° C ........................... 400 400 480 400 Mole percent alcohol too Methyl ethyl ketone ........................ 84.5 62.3 91.0 49.2 Secondary butanol ..................... 0.2 33.6 I, 48 46.2 Butylene. I, 52 o, 68 5.52 3.8 Ethyl amylene ketone ....................... 13.85 3.4 1.87 0.7 % Methyl ethyl ketone yield ............. 84.6 93.8 92.4 91.5 *) Standard specimen for spectroscopy, purer than chemically pure, experiment No. 83 Catalyst 94% ZnO, 6% ZrO2 ABCD Starting material: 91% isopropanol Test duration, hours ................... 0 to 5 5 to 10 10 to 15 15 to 20 Throughput V / V / St. ........................ 1.5 6.0 3.0 1.5 Temperature, ° C ........................... 400 400 480 400 Mole percent alcohol too Acetone ................................... 75.58 44.82 86.2 74.14 Isopropanol .............................. 3.37 41.56 0.428 9.40 Water ................................... 16.11 14.63 12.95 13.96 % Conversion ............................ 95.7 51.9 99.0 88.8 Experiment No. 70 Catalyst 88% ZnO, 12% ZrO2 *) ABCD Starting material: 91% isopropanol Duration of experiment, hours .................. o to 5 5 to 10 10 to 15 15 to 20 Throughput V / V / St. ........................ 1.5 6.0 3.0 1.5 Temperature, ° C ........................... 400 400 480 400 Mole percent alcohol too Acetone .................................. 51.3 70.1 89.8 86.2 Isopropanol ............................. 5.5 22.6 1.05 8.72 C8 olefin ...... 1.4 0.57 I, 24 0.97 Mesityloxyd ............................ 11.75 6.66 8.42 4.04 % Acetone yield ...................... 86.0 90.6 90.7 93.4 *) chemically pure test No. 7I Catalyst 88% ZnO, 12% ZrO2 *) Starting material: 99% secondary butanol Duration of experiment, hours .................. o to 5 5 to 10 10 to 15 15 to 20 Throughput V / V / St. ........................ 1.5 6.0 3.0 1.5 Temperature, ° C ........................... 400 400 480 400 Mole percent alcohol too Methyl ethyl ketone ....................... 90.6 57.2 95.2 89.0 Secondary butanol ..................... 4.68 41.6 0.75 6.5 Butylene ................................ 1.93 0.64 2.0 2.1 Ethyl amylene ketone ....................... 1.9 0.43 2.0 2.5 % Methyl ethyl ketone yield ........... 95.1 97.9 95.9 95.2 *) chemically pure experiment No. 74 Catalyst 94% ZnO, 6% ZrO2 (of the commercial grade mentioned above) ABCD Starting material: 99%, secondary butanol Duration of experiment, hours .................. o to 5 5 to 10 10 to 15 15 to 20 Throughput V / V / St. ........................ 1.5 6.0 3.0 1.5 Temperature, ° C ........................... 400 400 480 400 Mole percent alcohol too Methyl ethyl ketone ........................ 86.8 83.5 85.9 69.6 Secondary butanol .................... 1.5 14.0 9.25 21.2 Butylene ............................... 1.8 1.1 4.0 5.0 Ethyl amylene ketone ...................... 6.9 1.3 0.79 4.1 % Methyl ethyl ketone yield .......... 88.2 97.1 94.6 88.4 The catalysts, which contain zirconium oxide, cerium oxide and thorium oxide, show clear resistance to poisons. For example, in the experiments described, the secondary butyl alcohol contained 91 to 99,010 alcohol, 1 to 7.3 e10 impurities and 0.3 to 1 ole of water.

Claims (4)

P A T E N T A N S P R Ü C H E: I. Dehydrogenation catalyst, the is particularly suitable for the production of ketones from secondary alcohols, characterized in that it is made from oxides of zinc, magnesium or beryllium and an addition of oxides of zirconium, cerium or thorium, optionally also a mixture of these oxides, with the addition 1 to 15%, preferably 6 to 12% of the weight of the whole mixture. 2. Catalyst according to claim I, characterized in that it is used as Stabilizer an oxide of silicon, iron or aluminum in an amount from 6 to Contains 10 oils of the weight of the additive. 3. Catalyst according to claim I and 2, characterized in that it is deposited on a support, preferably iron filings. 4. A method for producing the catalyst according to claim 3, characterized characterized in that the oxides mixed in the appropriate proportions in powder form, sufficient Water is incorporated into the mixture to obtain a heavy pulp, and the Slurry applied to a support and dried at a temperature of about 80 ° will. Cited references: U.S. Patent No. 2,204,978 (ref. Chem. Zbl. I940, II, 3405); French Patent No. 906 I48 (ref. Chem. Zbl. 1946, I, I468).