Catalytic hydrogenation copper-chromium oxide

Aromatic rings in lignin may be converted to cyclohexanol derivatives by catalytic hydrogenation at high temperatures (250°C) and pressures (20—35 MPa (200—350 atm)) using copper—chromium oxide as the catalyst (11). Similar reduction of aromatic to saturated rings has been achieved using sodium in hquid ammonia as reductants (12). 

Although all of the above elements catalyze hydrogenation, only platinum, palladium, rhodium, ruthenium and nickel are currently used. In addition some other elements and compounds were found useful for catalytic hydrogenation copper (to a very limited extent), oxides of copper and zinc combined with chromium oxide, rhenium heptoxide, heptasulfide and heptaselen-ide, and sulfides of cobalt, molybdenum and tungsten. 

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. 

The hydrogenation of fatty acids or fatty esters is of industrial importance for the production of fatty alcohols. Usually, the hydrogenation is performed in slurry-phase or fixed-bed reactors over copper-chromium oxide catalyst at elevated temperature and pressure.37 Rieke et al. investigated the hydrogenation of methyl dodecanoate over copper-chromium oxide at 280°C and 13.8 MPa H2, in order to study the side reactions that occur during hydrogenation.37 On the basis of the potential reaction routes described by Rieke et al., the pathways leading to C12 alcohol and various byproducts are summarized in Scheme 10.2, with exclusion of the formation and reactions of acetals. It has been found that both catalytic activity and selectivity correlated well with the crystallinity of the copper-chromium ox-... 

Catalytic hydrogenation of alkyl aryl ketones and diaryl ketones to hydrocarbons is most convenient provided that high-pressure apparatus is available. Coppoalumina and copper-chromium oxide catalysts have been used. At 100-130° alcohols are formed, but at 180-250° excellent yields of the corresponding hydrocarbons are obtained. ... 

The reduction of aldols and ketols from the aldol condensation (method 102) is often a convenient route to branched 1,3-dio/s. Catalytic hydrogenation over platinum oxide, nickel-on-kieselguhr, and copper-chromium oxide has been used. Other procedures include electrolytic reduction and reduction by aluminum amalgam. 1,3-Diols may also be prepared by catalytic reduction of 1,3-diketones. Cleavage of the carbon-to-carbon and carbon-to-oxygen bonds accompanies this conversion. The effect of structure on the course of the reaction has been studied. ... 

Under certain conditions the reduction of amides leads to primary alcohols (cf. method 428). Thus, phenylethylacetamide is reduced by sodium and absolute ethanol to 2-phenyl-1-butanol (75%). a-Naphthylacetamide is reduced by sodium amalgam and hydrochloric acid to a-naphthylcarbinol (63%). Trifluoroethanol is obtained by catalytic hydrogenation of tri-fluoroacetamide over a platinum catalyst. Hydrogenation of the corresponding ester over copper-chromium oxide failed. ... 

Catalytic hydrogenation of amides to amines requires drastic conditions in general, a temperature of 250 to 265" and a pressure of 200 to 300 atm. over copper-chromium oxide catalyst using dioxane as the solvent. The yields of primary amines from unsubstituted amides are lowered mainly by the formation of secondary amines, viz.,... 

The keto group of a keto ester may be preferentially reduced by catalytic hydrogenation. Excellent yields of hydroxy esters are obtained. Copper-chromium oxide catalyst has been employed in the preparation of methyl p-(a-hydroxyethyl)-benzoate and several aliphatic -hydroxy esters. The last compounds have also been made by hydrogenation over nickel catalysts.Substituted mandelic esters are prepared by catalytic reduction of aromatic a-keto esters over a palladium catalyst. Similarly, platinum oxide and copper-chromium oxide have been used in the aliphatic series for the preparation of the a-hydroxy diester, diethyl... 

Hexamethylene glycol has been prepared by treating hexa-methylene iodide with silver acetate and hydrolyzing the acetate, by hydrolyzing the bromide, by reducing ethyl adipate with sodium and alcohol, and by the method here described. The catalytic hydrogenation over copper-chromium oxide of the... 

Reduction of cyclopropyl methyl ketone has been attempted by four different methods 415 Only poor yields of the alcohol were obtained by use of sodium and alcohol on use of LiAlH4 difficulties were encountered for larger batches and catalytic hydrogenation with Raney nickel caused partial cleavage of the cyclopropane ring however, excellent yields of 1-cyclopropylethanol were obtained in the presence of a copper-chromium oxide catalyst activated by barium, at 100°. 

Amides and lactams can be reduced in ways similar to those used for the acids and esters. Catalytic hydrogenation over copper-chromium oxide as... 

In general, nickel in its various forms requires elevated temperature and pressure conditions for the catalytic reduction of pyridines. Hydrogenations with nickel on keiselguhr (4) or nickel chromite (5), for example, employ similar rigorous conditions. Copper chromite (6) (copper chromium oxide) has also been investigated. With this catalyst temperature conditions are usually higher than with nickel catalysts. There is a report of the use of a palladium catalyst in the reduction of some 2-(/3-hydroxyalkyl) pyridines at 130° and 200 atmospheres pressure (7). 

Heterocyclic Compounds. Such materials undergo catalytic hydrogenation to yield the corresponding saturated derivatives. Thus, pyrrole is slowly converted to pyrrolidine at 200 C over either a nickel or copper-chromium oxide catalyst pyridine and pyridine derivatives behave similarly. Compounds such as furan and dihydropyran reduce rapidly and behave more like olefins in reactivity. Similarly, thiophene is converted to the tetrahydro derivative. 

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