Effect of Addition of K to Ni/SiO2 and Ni/Al2O3 Catalysts on Hydrothermal Cracking of Bitumen.

Abstract

Hydrothermal cracking of Canadian Athabasca bitumen was performed over Ni/SiO2 and Ni/Al2O3 catalysts under 703K and 5.0MPa of hydrogen pressure in a batch reactor. Comparing with thermal cracking under the same reaction conditions, hydrothermal cracking process obviously suppressed the formation of coke from 5.5 to 3.5wt% (Ni/SiO2) and to 3.0wt% (Ni/Al2O3), and the formation of gaseous hydrocarbon products. To decrease coke formation further, a small amount of potassium was impregnated in the catalysts. The spectroscopy of NH3-TPD showed that the amount of acidic sites in both catalysts, Ni/Al2O3 and Ni/SiO2, was dramatically decreased by K2O modification. The acid-catalyzed polymerization of residuum induced by acidic sites in the catalyst, that might result in the formation of coke, was suppressed by neutralization of the acidic sites. Adding 3% of potassium onto Ni/SiO2 decreased the yield of coke from 3.5 to 2.1wt%.