United States Patent Office Patented
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r 2,861,106 United States Patent Office Patented. Nov. 18, 1958 2 rectly, i. e., without prior reduction. In this case, re 2,861,106 duction occurs during the initial phase of the reaction. PROCESS OF PREPARING ALDEHYDES OR KE However, it is advantageous to reduce the catalyst prior TONES BY DEHYDROGENATION OF ALCOHOLS to use in the reaction. Such reduction can be carried Wolfgang Opitz, Knapsack, near Koln, and Werner out by treating the catalyst at relatively low tempera Urbanski, Koln-Bickendorf, Germany, assignors to tures, for instance, between 200° C. and 300° C. with Knapsack - Griesheim Aktiengesellschaft, Knapsack, hydrogen to effect reduction of a considerable amount near Koln, Germany, a corporation of Germany of the cupric oxide to copper and reduction of the high valent chromium to trivalent chromium. If need be, the No Drawing. Application February 24, 1955 O reduction can be carried out by adding nitrogen whereby Serial No. 490,402 too rapid a reaction and a thereby caused sintering can Claims priority, application Germany February 26, 1954 be avoided. A suitable catalyst can, for instance, be prepared as 6 Claims. (CI. 260-596) follows: 5 The present invention relates to a process for the de Cupric oxide is precipitated of its salts by means of hydrogenation of saturated aliphatic alcohols having a sodium carbonate at 80° C. to 90° C., washed until neu straight chain and being of a low molecular weight or tral and dried at 100° C. This fine-grained cupric oxide of cyclic primary and secondary alcohols, preferably al is comminuted and impregnated with an aqueous solu cohols containing 2 to 6 carbon atoms, into the corre 20 tion, for instance a sodium chromate solution of about sponding aldehydes or ketones by leading the alcohol 10% strength, whereby 0.5-3 parts by weight of Cr2O3 vapours, at raised temperatures, over a catalyst compris are calculated for 97-99.5 parts by weight of CuO. Then ing copper and small amounts of chromium, an alkali water is added to the mass in such an amount that an metal and oxygen. aqueous suspension is obtained which can easily be ap In industrial practice the dehydrogenation of alcohols, 25 plied onto pumice or another known carrier, for in for instance of isopropanol, into acetone, is carried out stance diatomaceous earth. However, it is also possible on a large scale. As catalysts, there are used, on the one to press the mass after stirring with water, without addi hand, zinc oxide or brass, on the other hand copper tion of carriers, in order to obtain shaped bodies or tab catalysts. lets, eventually by adding a binder, for instance an aque When using zinc oxide and brass catalysts it is neces 30 ous solution of methyl cellulose. The catalyst is then sary to operate at elevated temperatures of about 400 C. dried, at first suitably at a temperature of e.g. 100 C., to about 500 C. Thereby, secondary reactions increas then at a high temperature of e. g. between 600 C. and ingly occur, for instance the formation of olefines by 800° C. whereby the abrasion resistance can be consid separation of water and, before all, decompositions of erably increased. It is useful to fix the baking tempera the acetone at the iron tubes. 35 ture high enough that the binder, in the aforementioned When operating by means of a copper catalyst, these example the methyl cellulose, bakes, thus giving to the secondary reactions do not occur, as it is possible to catalyst an increased porosity. The impregnation can work at a lower temperature, but the durability of the also be carried out by spraying a chromate solution onto catalyst is reduced. the copper oxide which can, for instance, already have It is also known to dehydrogenize ethanol in the pres 40 been applied onto a carrier or compressed to form shaped ence of copper catalysts containing small amounts of bodies, chromium. However, these catalysts prepared by im The catalyst can be regenerated by oxidation by means pregnating silica which is used as carrier with solutions of air and by subsequent reduction by means of hydro of copper nitrate, chromium nitrate and subsequent dry gen. ing and baking do not contain an alkali metal and, after 45 The chromium Salt is added to the oxygen-containing having been in operation for about 250 hours, undergo copper compound suitably in small amounts only, ad a reduction of activity of about 20%. Besides that, the vantageously in a quantity of about 0.5-3%, preferably yield amounts to less than 40%. 0.5% to 2% of CrO3 referred to the total content of It has also been attempted to stabilize the catalyst chromium oxide and oxygen-containing copper com by means of oxides and hydroxides of the alkali and 50 pound, the latter being calculated as cupric oxide. The alkaline earth metals. Under the influence of these alkali addition of considerably larger quantities of chromium metal oxides and alkaline earth metal oxides, however, salt is not recommendable as, otherwise, the risk is given condensation reactions readily take place. that in consequence of the separation of water, olefines Now, we have found a copper catalyst containing, in may be formed and, simultaneously, the carbonyl group addition to small amounts of oxygen, also small amounts 55 may again be partially hydrogenated. of chromium and alkali metal oxide, which is effective at As chromium salts for the impregnation there can be a relatively low temperature, i. e. between about 250 used soluble alkali metal chromates and peroxychromates C. and about 380° C. It keeps an activity of long dura showing an alkaline reaction, especially the sodium and tion and, in consequence of its only insignificant alkalinity potassium salts readily accessible in industry, and, there does not cause any secondary reactions worth mention 60 of, especially the chromates. Ing. There are suitable, for instance, sodium chromate, po The catalyst according to the invention is prepared in tassium chromate, rubidium chromate, caesium chromate, that way that copper compounds, such as copper hydrox lithium chromate, as such, or in mixtures, or also in the ide, cuprous oxide or, advantageously, cupric oxide, are form of solutions which are obtained by adding liquors impregnated with a chromium salt solution showing an 65 to the dichromate solutions. The peroxy chromates alkaline reaction, for instance a sodium chromate solu MeCrO3, in which "Me” means a monovalent alkali rtion, that they are applied, if required, onto carriers and metal, of the same alkali metals can also be used. All then dried. The catalyst thus obtained may be used di- . these chromium salts contain at least double the molar 2,861,106 3 4 quantity of alkali metal oxide compared with chromium about 250 ml. of isopropyl alcohol. The following yields oxide. The limited amounts of chromium salts showing of acetone are obtained: an alkaline reaction and added to the catalyst according Conversion, to the invention, impart to the catalyst a reduced alka percent by inity. Besides that, the small chromium content shows Duration of weight (the Yield of ace Temperature operation, remainder tone referred an activating effect. hours being un- to isopropanol Small amounts of alkali liquors or salts can equally changed converted isopropy be added to the chromium salt, for instance sodium car alcohol) bonate, sodium bicarbonate or salts of organic acids such 0. as sodium acetate, sodium oxalate etc. or the correspond 250-270----------------------- 32 88.3 99.4 ing salts of the other alkali metals. These substances are 270--- 448 89.2 98.4 added, advantageously, in such an amount that the chro 800---------- 816 89.5 99.0 mium content amounts to between 0.5% and 3% calcu lated as Cr2O3 onto the sum of CuO and Cr2O3, and that In the same way secondary butyl alcohol can be con the alkali metal oxide content corresponds at least to verted into methyl-ethyl-ketone. about double the amount of mols and at most to six times Example 2 the molar amount of the CrO3. Ethyl alcohol of 95% (by volume) strength is led According to the process of the present invention, any over 2.2 1. corresponding to 1230 grams of a catalyst pre saturated primary or secondary aliphatic alcohol or satu 20 pared according to Example 1 and containing 39.64% rated cyclic compound, preferably those containing 2 to of CuO and 0.39% of CrO3, referred to the oxides. The 6 carbon atoms, may be dehydogenated. Examples of charge per hour of the catalyst amounts to about 480 such alcohols include ethyl alcohol, propyl alcohol, iso propyl alcohol, butanol, secondary butanol, primary and ml. of ethanol. The following yields were obtained at secondary pentanols and hexanols, cyclopentanol and cy temperatures of 280° C. to 340° C. within 480 hours clohexanol. The time of residence is determined by the 25 of operation and at a conversion of 72% by weight. charge of the catalyst which varies, according to the Yield in mol-percent, referred to the ethanol converted: alcohol used. It may, for instance, amount from about CECHO CH3COO-C2H5 CH3COOH CEI CO Total 1:1 to about 1:8, preferably from about 1:2 to about yield 1:4. This means that per each liter of liquid alcohol 30 reacted per hour 1-8 parts by volume of catalyst are 88.5 4.0 3.1 1.1 : 12 97.9 used. For the dehydrogenation of secondary alcohols into the corresponding ketones temperatures of about 250 C. to We claim: about 380° C., preferably between 250° C. and 360° C. 1.