Preparation copper-chromite

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

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). 

Chromia—alumina catalysts are prepared by impregnating T-alumina shapes with a solution of chromic acid, ammonium dichromate, or chromic nitrate, followed by gentie calciaation. Ziac and copper chromites are prepared by coprecipitation and ignition, or by thermal decomposition of ziac or copper chromates, or organic amine complexes thereof. Many catalysts have spiael-like stmctures (239—242). 

The catalyst is prepared as deseribed in Note 11 for the preparation of copper chromite. ... 

Alcohols are the most frequently formed products of ester hydrogenolysis. The hydrogenation of esters to alcohols is a reversible reaction with alcohol formation favored at high pressure, ester at low pressure (/). Copper chromite is usually the catalyst of choice. Details for the preparation of this catalyst (/7) and a detailed procedure for hydrogenation of ethyl adipate to hexamethylene glycol (/[Pg.80]

Interestingly, the Fischer indole synthesis does not easily proceed from acetaldehyde to afford indole. Usually, indole-2-carboxylic acid is prepared from phenylhydrazine with a pyruvate ester followed by hydrolysis. Traditional methods for decarboxylation of indole-2-carboxylic acid to form indole are not environmentally benign. They include pyrolysis or heating with copper-bronze powder, copper(I) chloride, copper chromite, copper acetate or copper(II) oxide, in for example, heat-transfer oils, glycerol, quinoline or 2-benzylpyridine. Decomposition of the product during lengthy thermolysis or purification affects the yields. 

The phthalide used by the submitters and by the checkers was a commercial product, obtained from E. I. du Pont de Nemours and Company, Wilmington, Delaware. This product is no longer available. Phthalide may be prepared in 82.5 per cent yields by hydrogenation of phthalic anhydride in benzene at 270° under 3000 lb. pressure in the presence of copper chromite 1 or, in yields of 61-71 per cent, from phthalimide according to the procedure given in Org. Syn. 16, 71 Coll. Vol. 2, 1943, 526. 

The hydrogenation of HMF in the presence of metal catalysts (Raney nickel, supported platinum metals, copper chromite) leads to quantitative amounts of 2,5-bis(hydroxymethyl)furan used in the manufacture of polyurethanes, or 2,5-bis(hydroxymethyl)tetrahydrofuran that can be used in the preparation of polyesters [30]. The oxidation of HMF is used to prepare 5-formylfuran-2-carboxylic acid, and furan-2,5-dicarboxylic acid (a potential substitute of terephthalic acid). Oxidation by air on platinum catalysts leads quantitatively to the diacid. [32], The oxidation of HMF to dialdehyde was achieved at 90 °C with air as oxidizing in the presence of V205/Ti02 catalysts with a selectivity up to 95% at 90% conversion [33]. 

Catalysts such as copper chromite, first prepared and utilized for carbonyl 1,2-reductions back in 1931 [47], have given way to more modern reagents for effecting... 

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. 

A high trans-mixture can be prepared starting from /3-cyclocitral which is hydrogenated to 2,2,6-trimethylcyclohexane carboxaldehyde. Condensation with 2-penta-none in the presence of sodium ethoxide yields the corresponding 3-hexenone. Hydrogenation with nickel copper chromite as a catalyst gives a mixture with up to 95% of the trans-isomer [114]. 

Copper chromite is prepared according to Organic Syntheses 3 and washed with sodium bicarbonate solution. The glycol is slurried with sodium bicarbonate and filtered before use. 

A wide variety of metals are active hydrogenation catalysts those of most interest are nickel, palladium, platinum, cobalt, iron, nickel-promoted copper, and copper chromite. Special preparations of the first three are active at room temperature and atmospheric pressure. The metallic catalysts are easily poisoned... 

Powders possessing relatively high surface area and active sites can be intrinsically catalytically active themselves. Powders of nickel, platinum, palladium, and copper chromites find broad use in various hydrogenation reactions, whereas zeolites and metal oxide powders are used primarily for cracking and isomerization. All of the properties important for supported powdered catalysts such as particle size, resistance to attrition, pore size, and surface area are likewise important for unsupported catalysts. Since no additional catalytic species are added, it is difficult to control active site location however, intuitively it is advantageous to maximize the area of active sites within the matrix. This parameter can be influenced by preparative procedures. 

An improved procedure for the laboratory preparation of 2,5-dimethylpyrazine has been reported.166 a-Amino alcohols are convenient precursors for the industrial preparation of alkylpyrazines. Thus when they are heated in the vapor phase with copper chromite catalysts, they are converted mainly into pyrazines [Eq. (8)] with hydrogenation catalysts such as Raney nickel, piperazines are the... 

Hexanediol,2 m.p. 40-41°, was prepared by catalytic reduction of diethyl adipate with hydrogen over copper chromite catalyst. It can also be purchased from Columbia Organic Chemicals Company, Inc. 

Copper chromite is prepared according to the method described by Adkins (1954). 

Clemo and Swan found that 2-methyl- and 2-ethyl-7-azaindole were reduced more reliably with copper chromite as catalyst under 160 atm of hydrogen at 180°. 2-Methyl-7-azaindoline (98, R = Me) was obtained in 42 % yield. They reported that Kruber s conditions gave mostly gums, from which only a little of the A-benzoyl derivatives could be isolated. Recently, however, 2-methyl-7-azaindoline (98, R = Me) was prepared on a 0.7-mole scale by use of Raney nickel under conditions identical to those used by Kruber, although no yield was reported. ... 

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