Adkins catalyst oxide

Hydrogenation of Fatty Acid Methyl Esters The hydrogenolysis of fatty acid methyl esters into the corresponding fatty alcohols and methanol is performed at 200-300°C and a H2 pressure of 200-300 bar with the aid of copper oxide/chromium oxide catalysts (Adkins catalysts). Three different procedures are applied [39 a-c] ... 

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. 

Copper(ll) chromite is obtained by heating copper chromate, CuCr04 at 400°C. The Adkin catalyst, a mixture of copper oxide and copper chromite, is prepared by mixing aqueous solutions of copper nitrate, sodium dichromate and ammonium hydroxide the orange precipitate of copper ammonium chromate formed is dried and then heated below 400°C. 

Naturally occurring fatty alcohols used in the fragrance industry are produced principally by reduction of the methyl esters of the corresponding carboxylic acids, which are obtained by transesterification of natural fats and oils with methanol. Industrial reduction processes include catalytic hydrogenation in the presence of copper-chromium oxide catalysts (Adkins catalysts) and reduction with sodium (Bouveault—Blanc reduction). Unsaturated alcohols can also be prepared by the latter method. Numerous alcohols used in flavor compositions are, meantime, produced by biotechnological processes [11]. Alcohols are starting materials for aldehydes and esters. 

Copper chromite, CuCr204, and mixtures of cupric oxide with chromium sesquioxide and special additives (the Adkins catalyst), dehydrogenate primary alcohols to aldehydes [354, 355] and secondary alcohols to ketones [354, 355, 356]. 

Another common catalyst prepared by coprecipitation is copper-chromium oxide, also known as "copper chromite" or Adkins catalyst.23 This catalyst is prepared by the addition of copper nitrate to a solution of ammonium dichromate in ammonia giving a precipitate copper ammonium dichromate. This precipitate is filtered, dried and then calcined at 650°-800°C, or more commonly, heated with a flame to induce a thermal reaction (Eqn. 13.5). The resulting fine powder is washed with acetic acid and dried to give the copper chromite catalyst.23 A more active catalyst is prepared by adding 10% barium nitrate by weight of copper before precipitation.24,25 Copper chromite catalysts containing calcium and were found to be less effective than those having a barium promoter.25... 

Hydrogenation Copper chromite (Lazier catalyst). Copper chromium oxide (Adkins catalyst). Lindlar catalyst (see also Lithium ethoxyacetylide, Malealdehyde, Nickel boride). Nickel catalysts. Palladium catalysts. Palladium hydroxide on carbon. Perchloric acid (promoter). Platinum catalysts. Raney catalysts, Rhenium catalysts. Rhodium catalysts. Stannous chloride. Tributylborane. Trifluoroicetic acid, Tris (triphenylphosphine)chlororhodium. 

Adkins catalyst. A catalyst containing copper chromite and copper oxide. It is used for the reduction of organic compounds, usually at high temperatures and pressures. It is likewise used as a catalyst for dehydrogenation and for decarboxylation reactions. 

We mentioned above two copper catalysts produced by coprecipitation, viz., the Adkins catalyst (copper-chromia) and the copper-zinc oxide catalyst. The precursor of the two catalysts is produced by coprecipitation. The preparation of the catalysts involves selective removal of carbonate ions, water, and the oxygen atoms bonded to copper. The intimate mixing of the copper ions with the precursor of the supports and the strong interaction of copper with both zinc oxide and chromia furnish copper particles that are still small even after virtually complete reduction of the copper. 

It is necessary to precipitate rapidly and maintain a itrriform pH. This produces small active crystallites and well-mixed oxides in the firtished catalyst. Under these conditions specific compounds form such as those described by Feitknecht, with the composition (M )e(M )2 (OH)i6 (COs) 4H2O. The Adkins catalyst, copper/ammonium chromate, is another example of applying a specific precipitation procedure. 

H. Adkins, Reactions of Hydrogen with Organic Compounds over Chromium Oxide andNickel Catalysts, University of Wisconsin Press, Madison, 1946. 

The sequence has been applied to the synthesis of 1,4-cyclohexanedione from hydroquinone 10), using W-7 Raney nickel as prepared by Billica and Adkins 6), except that the catalyst was stored under water. The use of water as solvent permitted, after hltration of the catalyst, direct oxidation of the reaction mixture with ruthenium trichloride and sodium hypochlorite via ruthenium tetroxide 78). Hydroquinone can be reduced to the diol over /o Rh-on-C at ambient conditions quantitatively (20). 

Adkins-Peterson The oxidation of methanol to formaldehyde, using air and a mixed molybdenum/iron oxide catalyst. Not an engineered process, but the reaction which formed the basis of the Formox process. 

Formox [Formaldehyde by oxidation] A process for oxidizing methanol to formaldehyde, using a ferric molybdate catalyst. Based on the Adkins-Peterson reaction, developed by Reichold Chemicals, and licensed by that company and Perstorp, Sweden. Acquired by Dyno Industries in 1989. The process uses formaldehyde produced in this way to make formaldehyde-urea resin continuously. A plant using this process was to be built in Ghent by 1991, owned jointly by Dyno and AHB-Chemie. Licensed to 35 sites worldwide. Several other companies operate similar processes. 

Adkins, Reactions of Hydrogen with Organic Compounds over Copper-Chromium Oxide and Nickel Catalysts, p 31, University of Wisconsin Press, Madison, Wisconsin, 1937, Ind I ng tlum Anal I d 4, 342 (19)2)... 

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