Copper Chromite Catalysts

COPPER CHROMITE CATALYST (Copper-Chromium Oxide) 

A mixture of 26 g. (0.1 mole) of c.p. barium nitrate and 800 cc. of distilled water is warmed to 70°. After solution is complete 218 g. (0.9 mole) of c.p. cupric nitrate trihydrate is added and the mixture stirred at 70° until a clear solution results (Note 2). 

A solution of ammonium chromate is prepared by dissolving 126 g. (0.5 mole) of c.p. ammonium dichromate in 600 cc. of distilled water and adding 150 cc. of 28 per cent aqueous ammonia (sp. gr. 0.9) (Note 3). The warm solution of the nitrates is stirred (hand stirring is adequate) while the ammonium chromate solution is poured into it in a thin stream. The stirring is continued for a few minutes, after which the reddish brown precipitate of copper barium ammonium chromate is collected (Note 4) and pressed in a 16-cm. Buchner funnel, and dried at no0. This dry precipitate is placed in a loosely covered nickel pan (Note 5), or one or two small porcelain casseroles covered with watch glasses, and heated in a muffle furnace for one hour at 350-450° (Note 6). At this point the yield of chromite should be about 160 g. The ignition residue is pulverized in a mortar to break up any hard lumps that may be present (Note 7) and 

The reactions involved in this preparation cannot be expressed quantitatively in a simple equation. The process has been investigated by Groger.1 

Barium nitrate is sparingly soluble in cold water and even less soluble in copper nitrate solution. It is therefore necessary to heat the mixture in order to bring both salts into solution together. 

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Hydrolysis of primary amides cataly2ed by acids or bases is very slow. Even more difficult is the hydrolysis of substituted amides. The dehydration of amides which produces nitriles is of great commercial value (8). Amides can also be reduced to primary and secondary amines using copper chromite catalyst (9) or metallic hydrides (10). The generally unreactive nature of amides makes them attractive for many appHcations where harsh conditions exist, such as high temperature, pressure, and physical shear. 

Uses ndReactions. Nerol (47) and geraniol (48) can be converted to citroneUol (27) by hydrogenation over a copper chromite catalyst (121). In the absence of hydrogen and under reduced pressure, citroneUal is produced (122). If a nickel catalyst is used, a mixture of nerol, geraniol, and citroneUol is obtained and such a mixture is also useful in perfumery. Hydrogenation of both double bonds gives dimethyl octanol, another useful product. 

Dehydrogenation of citroneUol over a copper chromite catalyst produces citroneUal [106-23-0] in good yield (110). If the dehydrogenation is done under distiUation conditions in order to remove the lower boiling citroneUal as it is formed, polymerization or cyclization of citroneUal is prevented. 

Most synthetic camphor (43) is produced from camphene (13) made from a-piuene. The conversion to isobomyl acetate followed by saponification produces isobomeol (42) ia good yield. Although chemical oxidations of isobomeol with sulfuric/nitric acid mixtures, chromic acid, and others have been developed, catalytic dehydrogenation methods are more suitable on an iadustrial scale. A copper chromite catalyst is usually used to dehydrogenate isobomeol to camphor (171). Dehydrogenation has also been performed over catalysts such as ziac, iadium, gallium, and thallium (172). 

High pressure processes P > 150 atm) are catalyzed by copper chromite catalysts. The most widely used process, however, is the low pressure methanol process that is conducted at 503—523 K, 5—10 MPa (50—100 atm), space velocities of 20, 000-60,000 h , and H2-to-CO ratios of 3. The reaction is catalyzed by a copper—zinc oxide catalyst using promoters such as alumina (31,32). This catalyst is more easily poisoned than the older copper chromite catalysts and requites the use of sulfiir-free synthesis gas. 

Copper—cadmium and zinc—chromium oxides seem to provide most selectivity (38—42). Copper chromite catalysts are not selective. Reduction of red oil-grade oleic acid has been accompHshed in 60—70% yield and with high selectivity with Cr—Zn—Cd, Cr—Zn—Cd—Al, or Zn—Cd—A1 oxides (43). The reduction may be a homogeneously catalyzed reaction as the result of the formation of copper or cadmium soaps (44). 

The preparation of methyl 12-ketostearate from methyl ricinoleate has been accompHshed using copper chromite catalyst. The ketostearate can also be prepared from methyl ricinoleate in a two-step process using Raney nickel. The first step is a rapid hydrogenation to methyl 12-hydroxystearate, the hydrogen coming from the catalyst, followed by a slower dehydrogenation to product (50,51). 

Ruthenium dioxide or ruthenium-on-carbon are effective catalysts for hydrogenation of mono- and dicarboxylic acids to the alcohol or glycol. High pressures (5,000-10,000 psig) and elevated temperatures (130-225 C) have been used in these hydrogenations 8,12,24). Yields of alcohol tend to be less than perfect because of esterification of the alcohol. Near quantitative yields of alcohol can be obtained by mixing ruthenium and copper chromite catalysts so as to reduce the ester as formed. 

The most complete study on the oxidation of CO and hydrocarbons was reported by Kuo et al. (91). Their study was done on a copper chromite catalyst under conditions that simulate exhaust gases. They found that CO oxidation kinetics is very accurately represented as first order in CO... 

Two options are being developed at the moment. The first is to produce 1,2-propanediol (propylene glycol) from glycerol. 1,2-Propanediol has a number of industrial uses, including as a less toxic alternative to ethylene glycol in anti-freeze. Conventionally, 1,2-propanediol is made from a petrochemical feedstock, propylene oxide. The new process uses a combination of a copper-chromite catalyst and reactive distillation. The catalyst operates at a lower temperature and pressure than alternative systems 220°C compared to 260°C and 10 bar compared to 150 bar. The process also produces fewer by-products, and should be cheaper than petrochemical routes at current prices for natural glycerol. The first commercial plant is under construction and the process is being actively licensed to other companies. 

Lactones can be hydrogenolyzed on copper chromite catalysts.23 Diol formation is favored at lower temperatures, whereas higher temperatures give cyclic ethers. This process is not widely used, however, because of experimental difficulties. 

Palladium catalysts, mostly palladium on carbon and Pearlman s catalyst, are used for the hydrogenolysis of the benzyl—nitrogen bond. However, in some cases, platinum, nickel, and copper chromite catalysts have also been used. 

Copper chromite catalyst, after use in high-pressure hydrogenation of fatty acids to alcohols, is pyrophoric, possibly owing to presence of some metallic copper and/or chromium. Separation of the catalyst from the product alcohols at 130°C in a non-inerted centrifuge led to a rapid exotherm and autoignition at 263°C. 

See CATALYTIC NITRO REDUCTION PROCESSES, COPPER CHROMITE CATALYST... 

Catalysts suitable specifically for reduction of carbon-oxygen bonds are based on oxides of copper, zinc and chromium Adkins catalysts). The so-called copper chromite (which is not necessarily a stoichiometric compound) is prepared by thermal decomposition of ammonium chromate and copper nitrate [50]. Its activity and stability is improved if barium nitrate is added before the thermal decomposition [57]. Similarly prepared zinc chromite is suitable for reductions of unsaturated acids and esters to unsaturated alcohols [52]. These catalysts are used specifically for reduction of carbonyl- and carboxyl-containing compounds to alcohols. Aldehydes and ketones are reduced at 150-200° and 100-150 atm, whereas esters and acids require temperatures up to 300° and pressures up to 350 atm. Because such conditions require special equipment and because all reductions achievable with copper chromite catalysts can be accomplished by hydrides and complex hydrides the use of Adkins catalyst in the laboratory is very limited. 

Reduction of unsaturated ketones to saturated alcohols is achieved by catalytic hydrogenation using a nickel catalyst [49], a copper chromite catalyst [50, 887] or by treatment with a nickel-aluminum alloy in sodium hydroxide [555]. If the double bond is conjugated, complete reduction can also be obtained with some hydrides. 2-Cyclopentenone was reduced to cyclopentanol in 83.5% yield with lithium aluminum hydride in tetrahydrofuran [764], with lithium tris tert-butoxy)aluminium hydride (88.8% yield) [764], and with sodium borohydride in ethanol at 78° (yield 100%) [764], Most frequently, however, only the carbonyl is reduced, especially with application of the inverse technique (p. 21). 

Pentanediol (PDO) holds promise for being used in the synthesis of polyesters. It has been synthesized from GVL in the presence of a copper chromite catalyst. At 150 °C and 20.3-30.4 MPa hydrogen pressure, 78.5% PDO was produced together with 8.1% 1-pentanol. ... 

Synthesis from Citronellol. ( )-Citronellal can also be obtained by dehydrogenation of citronellol under reduced pressure with a copper chromite catalyst [64]. 

With Raney nickel-copper chromite catalysts, methylionones are converted into tetrahydromethylionols, which are also used as fragrance materials [91]. 

This was followed by Taback s (94) study of the effect of copper chromite catalyst additives. In general, the results of these investigations fitted the Summerfield relation remarkably well over the range 1—100 atm. (Figures 3 and 6). Moreover, the effects of propellant composition and oxidizer particle size on the constants a and b, respectively, were consistent with qualitative predictions from the theory. Similar results have since been obtained by Yamazaki (101), Marxman (18), and the group at ONERA (8, 52, 64) in France (Figure 7). An alternative to the above equation has been proposed by Penner et al. (68)—i.e., (1/r)2 = (a/p)2 + (b/pm)2. A systematic survey (91) of all available data shows that when... 

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