Investigation of the Thermal Stability of the Chromia-Alumina Catalysts for the Process of the One-Stage Dehydrogenation of n-Butane

The effect of the hugh-temperature (800-1000 degrees C) treatment in air of the CWr(2)O(3)/Al2O3 catalyst, which contained 18Cr(2)O(3) + 0.4Na(+), wt % and was prepared under laboratory conditions with the use of Pural SB1 grade high-purity pseudoboehmite, on the variation in the phase composition of the catalyst, specific surface, and catalytic characteristics in the dehydrogenation reaction of n-butane (yield and selectivity by Sigma C-4 olefins and 1,3-butadiene, conversion of n-butane) was investigated depending on the calcination temperature of the catalyst. It is shown that thermal stability depends on the following main factors: the method preparation of catalysts, the phase composition of the starting aluminum hydroxide, carrier texture, and the presence of modifying additions and impurities of other metals. In the case of the same chemical composition of the catalyst, the samples obtained by the wet mixing of pseudoboehmite with an aqueous solution of chromic anhydride are most thermally stable compared with the impregnation samples. It is established that the addition of cerium improves the thermal stability and activity of the impregnation Al-Cr catalyst, while the impurity of the Fe3+ ions (up to 0.1 wt %) does not worsen these characteristics. The investigated samples of the catalyst are more thermally stable than the imported industrial catalyst, which loses activity and specific surface after calcination at 900-1000 degrees C. The determination of the thermal stability of fresh catalysts and the factors affecting it can be used as the preliminary evaluation of the future lifetime of catalysts.