The decomposition of calcium carbonate in catalysts

Abstract

It has been shown by x-ray phase analysis and by derivatographic, IR-spectroscopic, and gas-analytical (URAS-2 gas analyzers for C02 and CO) methods that when nickel, cobalt, and copper catalysts based on cements and calcium aluminate in which calcite is formed during their preparation [i] are reduced, decomposition of the calcite takes place at a temperature of 400~ i.e., considerably lower than its dissociation temperature. Such a lowering of the decomposition temperature of CaCO3 has not been observed in samples prepared by mechanically mixing the initial components and the corresponding metal powders (Ni, Co, Cu). Analysis of the decomposition products of CaCOs showed the presence in the gas phase of, apart from C02, considerable amounts of CO, CH4, and H20, which are the products of the transformation of COz in a reducing medium in the presence of the active components (Ni, Co, Cu) of the catalysts. CO and H~O are formed by the reaction of C02 with H2, and CH~ by the hydrogenation of CO2 and CO. The decomposition of the CaC03 included in the composition of the catalysts begins at 200-280~ in a reducing medium. Complete decomposition is reached at 400~ with a time of thermostating of ~24 h.