Calcination Temperature Effect on Supported Ruthenium Catalysts for Fischer-Tropsch Synthesis Reaction.

Abstract

Adjustment of air calcination temperature can significantly change the metal dispersion of Ru/Al2O3 catalyst and control the activity and selectivity of the Fischer-Tropsch synthesis. The reaction characteristics of the low-temperature-calcined catalysts were different from those of the high-temperature-calcined catalysts. The change in CO conversion by the catalysts calcined at different temperature took place in the range 200-250°C. n-Hexane in supercritical state was used to effectively extract high-molecular-weight products in the catalyst bed and reactor, to attain a complete distribution of the products. The chain-growth probability, as well as the olefin-to-paraffin ratio of the products was remarkably influenced by Ru dispersion. The water added to the synthesis gas promoted the chain-growth probability and enhanced the olefin contents in the products. The strength of the bond between adsorbed CO and surface Ru atoms was greatly controlled by calcination temperature. Oxygenates were formed on low-temperature-calcined catalyst but hydrocarbons were formed only on high-temperature-calcined catalyst in the ethylene-added Fischer-Tropsch reaction.