Catalysts Adkins’ catalyst

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] ... 

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. 

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 chromite (Adkins catalyst) does not catalyze hydrogenation of benzene rings. 

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. 

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. 

With this catalyst, methyl palmitate afforded palmityl alcohol in 78% yield on hydrogenation at 175° for 3 hrs. Aldehydes and ketones were hydrogenated at room temperature with catalyst that had been activated by heating it at 100° under hydrogen pressure. The same activation can be effected by refluxing the catalyst in cyclohexanol for 4 hrs. during this time 11% of cyclohexanone is formed. Cholestane-3/3-ol, refluxed in xylene with three times its weight of Adkins catalyst (HJS 2), affords cholestane-3-one in moderate yield. 

This Adkins catalyst is effective for saturation of the reactive 9,10-double bond of phenanthrene, and for hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol. ... 

Raney cobalt catalyst. The catalyst is prepared by the action of sodium hydroxide on a 40 60 cobalt-aluminum alloy available from Raney Catalyst Co. The procedure is that used by Billica and Adkins for the preparation of W-7 Raney nickel. 

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. 

By hydrogenation at high pressure of ethyl laurate in the presence of a copper-chromium catalyst. Adkins and Folkers, J. Am. Chem. Soc. 53, 1095 (1931). 

Dr. S. L. Stafford (Alfa Inorganics) writes that I am unable to tell the difference from the method of preparation between the Lazier catalysts and the Adkins catalysts. They seem to be essentially identical and both are made in the same way as the material which we offer. Our copper chromate is a fine black powder of the formula indicated plus small amounts of barium chromate which may or may not be essential as the activator. The catalyst is stable to both air and moisture. ... 

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. 

As far as the effect of the decomposition conditions is concerned, the following can be reported. The activity of the product is proportional to the rate of the decomposition and varies inversely with the decomposition temperature. The rate can be enhanced by starting with as fine metal powder as possible and adding the latter as rapidly as possible to the decomposing medium [6]. The primary particle size of the catalyst (as determined by x-ray analysis) always increases with the hydroxide concentration and the temperature [23]. However, the hydroxide concentration has little effect on the activity of the catalyst. Adkins [1] has presented a number of conclusions on the effect of these external conditions on the preparation of Raney Ni. 

Cu(0H)NH4Cr04 as a precursor for copper chromite (Adkins catalyst)... 

For hydrogenation, the Adkins catalyst will help the cleavage of a hydrogen-hydrogen bond so that the hydrogen can add to double bonds (Scheme 1). 

SCHEME 1. Hydrogenation of olefin over an Adkins catalyst... 

Other references related to the Adkins catalyst are cited in the literature. H. REFERENCES... 

The mechanism in Bergius process might be similar to the hydrogenation of alkenes using the Adkins Catalyst. 

In terms of hydrogenation, the Sabatier-Senderens reduction has been extensively modified, as shown by the Fischer-Tropsch Synthesis (or process), the Adkins Catalyst, and Raney-Nickel Catalyst. In addition, the silica black-supported nickel catalyst, and nickel-based complex reducing agents (Nic, e.g. NaH-RONa-Ni(OAc)2), have also been developed, the latter is a heterogeneous hydrogenation catalyst that works at atmospheric pressure. 

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. 

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