Effect of calcium salts on isosynthesis over ZrO2 catalysts

The promoting effects of various calcium salts on the activity and selectivity of ZrO2 in isosynthesis were studied in this work. Calcium salts were added into zirconia by mechanical mixing methods. Catalytic tests were performed under relatively mild operation conditions (673 K, 650 h(-1), 5.0 MPa). CaF2 and CaSO4 were found to be effective additives, which could remarkably enhance the i-C-4 selectivity in total hydrocarbons while maintaining the activity of pure ZrO2 when being added into zirconia. However, Ca(NO3)(2), Ca(BO2)(2) and CaCl2 wholly changed the distribution of hydrocarbons to favor the methanation. The results of temperature-programmed desorption (TPD) of NH3 and CO2 indicated that the performance of the catalysts depended on the acid-base properties of the catalysts. The appropriate amount of acid and base and the ratio of the basic to acidic sites on the catalysts are significant for the synthesis of i-C4 hydrocarbons from CO hydrogenation. (C) 2001 Elsevier Science B.V. All rights reserved.