Barium copper chromite

Barium copper chromite Diols from dicarboxylic acids... 

For more selective hydrogenations, supported 5—10 wt % palladium on activated carbon is preferred for reductions in which ring hydrogenation is not wanted. Mild conditions, a neutral solvent, and a stoichiometric amount of hydrogen are used to avoid ring hydrogenation. There are also appHcations for 35—40 wt % cobalt on kieselguhr, copper chromite (nonpromoted or promoted with barium), 5—10 wt % platinum on activated carbon, platinum (IV) oxide (Adams catalyst), and rhenium heptasulfide. Alcohol yields can sometimes be increased by the use of nonpolar (nonacidic) solvents and small amounts of bases, such as tertiary amines, which act as catalyst inhibitors. 

This reaction is favored by moderate temperatures (100—150°C), low pressures, and acidic solvents. High activity catalysts such as 5—10 wt % palladium on activated carbon or barium sulfate, high activity Raney nickel, or copper chromite (nonpromoted or promoted with barium) can be used. Palladium catalysts are recommended for the reduction of aromatic aldehydes, such as that of benzaldehyde to toluene. 

Copper chromite 14) and barium-promoted copper chromite (75,/7) have been used for acid reductions but very high temperatures (300 C) are required. The necessary temperature is sufficiently higher than that required foresters to permit selective reduction of half-acid esters to the hydroxy acid 23). The reverse selectivity can be achieved by reduction over H Ru4 CO)a PBu3)4 at I00-200 C and 1500-3000 psig. This homogeneous catalyst will reduce acids and anhydrides, but not esters (2). 

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. 

Phthalimide was hydrogenated catalytically at 60-80° over palladium on barium sulfate in acetic acid containing an equimolar quantity of sulfuric or perchloric acid to phthalimidine [7729]. The same compound was produced in 76-80% yield by hydrogenation over nickel at 200° and 200-250 atm [43 and in 75% yield over copper chromite at 250° and 190 atm [7730]. Reduction with lithium aluminum hydride, on the other hand, reduced both carbonyls and gave isoindoline (yield 5%) [7730], also obtained by electroreduction on a lead cathode in sulfuric acid (yield 72%) [7730]. 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosemnund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydrofomiylation, using HCN and HQ (Gatterman reaction) or carbon monoxide and HQ (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

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... 

Copper chromite (Lazier catalyst). Supplier Harshaw (CU-0202P 556-002). For preparation of the catalysC an aqueous solution of barium nitrate and cupric nitrate trihydrate is stirred during addition of a solution of ammonium chromate, prepared from ammonium dichromate and aqueous ammonia. The reddish brown precipitate of copper barium ammonium chromate is washed and dried and decomposed by heating in a muffle furnace at 350-450 . The ignition residue is pulverized, washed with 10% acetic acid, dried, and ground to a fine black powder. 

Copper chromite has been made by the ignition of basic copper chromate at a red heat and by the thermal decomposition of copper ammonium chromate. The procedure given here is a modification of the latter method in which barium ammonium chromate is also incorporated. Copper-chromium oxide hydrogenation catalysts have also been prepared by grinding or heating together copper oxide and chromium oxides, by the decomposition of copper ammonium chromium carbonates... 

In a steel reaction vessel (Note i), capable of withstanding high pressures with an adequate safety factor (Note 2) and having a capacity of 400 cc. or more, are placed 252 g. (1.25 moles) of ethyl adipate (b.p. i44-i45°/29 mm.) (Org. Syn. 17, 32) and 20 g. of copper chromite catalyst, prepared either with or without the addition of barium (p. 31). The reaction vessel is closed, made gas tight, and secured in a suitable agitating device. After connection is made with the hydrogen supply, hydrogen is introduced until a pressure of 2000 to 3000 lb. per sq. in. is reached (Note 2). 

Barium has been included as a catalyst component on account of its protective action against sulfate poisoning and its reported stabilization of the catalyst against reduction. Alternatively, the above procedure may be used for the preparation of a copper chromite catalyst containing no barium. In this case the barium nitrate is omitted and 242 g. (i mole) of copper nitrate is used. All other details are the same as given above. 

Moreover, the catalysts promoted by alkaline or alkaline-earth species are more stable than the unpromoted CuCr. For example, barium impregnated on copper chromite increases the stability of the active CuCr02 phase (13). Furthermore, the presence of barium or calcium on copper chromite catalysts influences strongly the selectivity to the methylation of amines N-alkylation/N-methylation. 

In our laboratory, we have shown that copper chromite doped with barium, calcium or manganese can lead selectively to dimethyldodecylamine from lauronitrile, ammonia, hydrogen and methanol but not to methyldidodecylamine (14). 

The catalyst used in this study was a copper chromite doped with barium (YPl). The other solids were prepared from that catalyst by impregnation with alkaline salts from Prolabo (LiNOj, KOH, CsNOs). After impregnation, the catalysts were dried in a sand-bath (120°C), and then calcinated at 350°C for 4 hours under a dry air stream. 

It is remarkable that furfuraldehyde can be converted into furfuryl alcohol in yields of up to 95% in presence of a copper chromite catalyst stabilized by barium,344b whereas it is hydrogenated simultaneously in the ring when the usual noble-metal catalysts are used. 

Copper-chromite type catalysts supported by alumina or graphite and promoted with barium were used for the one step synthesis of tertiary fatty amines (R2NCH3 or RN(CH3)2) from nitrile, methanol and hydrogen. The surface composition of the catalysts was studied by XPS and by adsorption experiments. A correlation was found between the selectivity and the presence of a well-dispersed CUC1O2 phase, stabilized with barium. Moreover the elements influencing the stability of the copper catalysts were also studied and we remarked the effect of the promoter or/and of the support on the variation of the copper surface area in the presence of water or ammonia. These modifications were examined in relation with the change of the catalytic properties with time-on-stream. 

Difluoropyrrole (58) has been extensively used in the syntheses of octafluor-oporphyrins and other calyx( )pyrroles. This was first accessed by Leroy and Wakselman by barium-promoted copper chromite decarboxylation of 3,4-difluor-opyrrole-2-carboxylic acid in quinoline at 200°C. The acid was prepared in four steps beginning with a cycloaddition reaction of the protected aziridine 59 and chlorotrifluoroethylene (Fig. 3.26). 

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