The promoting effects of various calcium salts on the activity and selectiv
ity of ZrO2 in isosynthesis were studied in this work. Calcium salts were a
dded into zirconia by mechanical mixing methods. Catalytic tests were perfo
rmed under relatively mild operation conditions (673 K, 650 h(-1), 5.0 MPa)
. CaF2 and CaSO4 were found to be effective additives, which could remarkab
ly enhance the i-C-4 selectivity in total hydrocarbons while maintaining th
e 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 f
avor the methanation. The results of temperature-programmed desorption (TPD
) of NH3 and CO2 indicated that the performance of the catalysts depended o
n 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 s
ignificant for the synthesis of i-C4 hydrocarbons from CO hydrogenation. (C
) 2001 Elsevier Science B.V. All rights reserved.