Zinc chromite

Zinc Chrome Cobalt Aluminate Blue pigment for plastics, 7 370t Zinc chromite... 

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. 

Unsaturated alcohols can be obtained from unsaturated esters under special precautions. Catalytic hydrogenation over zinc chromite converted butyl oleate to oleyl alcohol (9-octadecenol) in 63-65% yield even under very energetic conditions (283-300°, 200atm) [52]. 

Zinc chromite (ZnCr204), which is used to make magnetic tape for cassette recorders, can be prepared by the thermal decomposition of (NH4)2Zn(CrC>4)2. The other reaction products are N2 and water vapor. 

Moser, W. R., and Connolly, K. E., Synthesis and characterization of copper modified zinc chromites by the high-temperature decomposition (HTAD) process for higher alcohol synthesis, Chem. Eng. J. 64,239 (1996). 

Zinc chromite ZnCr204, ZnO methanol synthesis (high pressure)... 

Copper/zinc chromite CuxZni, Cr204, CuO methanol synthesis (low pressure)... 

The influence of the C02/C0 ratio on the synthesis has been embedded in kinetic equations only recently. The early kinetic equations for the high-pressure Zn0/Cr203 catalyst did not contain a C02-dependent term at all, perhaps because the effects of C02 were not significant when zinc chromite catalysts were used Natta et al. (57) proposed the rate equation for the Zn0/Cr203 catalyst at temperatures 300-360°C as follows ... 

Zinc Chromite, ZnO.CraOg, may be obtained in the same manner as the corresponding calcium salt. It yields dark green octahedral crystals of density 5 29 at 13° C. Two other zinc compounds are known, namely 3Zn0.2Cr20j eZnO.SCrgOg. 

The investigation of zinc oxide-zinc chromite of the composition ZnO-ZnO-CraOs (77), which reveals an x-ray pattern of zinc oxide plus a spinel structure, led to the result that 5obs. does not agree with any of the values of evaluated for n = 1, 2, and 3 (Fig. 18). The differential heat of adsorption of carbon dioxide on this catalyst was found to be 43 kcal./ mole, i.e., equal to that on zinc oxide alone but by far greater than that... 

Fig. 17. Adsorption isotherms of CO2 on zinc chromite (3.5 g., 103 m.O- The plot of Scald, and Sobs, against equilibrium pressure. T = 100°C., Ae = 16 kcal./mole.

Fig. 18. Adsorption isotherms of COz on zinc oxide-zinc chromite (4 g., 129 m.O-The plot of Scale, and Sobs, against equilibrium pressure. T = 400°C., Ac = 43 kcal./ mole.

Oleyl alcohol occurs naturally in fish oils. Synthetically, it can be prepared from butyl oleate by a Bouveault-Blanc reduction with sodium and butyl alcohol. An alternative method of manufacture is by the hydrogenation of triolein in the presence of zinc chromite. 

Zn-. [M THarshaw] Zinc chromite or zinc oxide catalysts. 

The concentration theory completely fails to explain the selective nature of catalysis. Why, for example, does formic acid decompose into hydrogen and carbon dioxide with a zinc oxide catalyst, whereas with titanium oxide, it breaks down to carbon monoxide and water Or, to quote another example, why do carbon monoxide and hydrogen form methane in the presence of nickel, whereas quantitative yields of methanol are produced with a zinc chromite catalyst.6... 

ZINC CHROMITE (12018-19-8) An oxidizer. Reacts with reducing agents, combustibles, organic materials. 

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