Fischer-Tropsch synthesis: A long term comparative study of the product selectivity and paraffin to olefin ratios over an iron-based catalyst activated by syngas or H2

Abstract

The effect of activating atmosphere, reaction conditions and time on stream (TOS) on the catalytic performance and especially on the paraffin to olefin ratios (P/O) over an iron catalyst during Fischer-Tropsch synthesis was investigated. Activation with syngas led to better catalyst performance. For the long-term FT runs, although a higher catalytic activity and P/O ratio have been measured for the catalyst reduced by syngas, similar CO conversions, P/O ratios and product selectivity were achieved for the catalysts reduced by either syngas or H2 after 2200 h TOS, which indicates that no matter which kind of reducing agent is used to reduce the catalyst, the catalyst performance tends to be similar after a long TOS. Despite the P/O variations with different reaction conditions, a graphical approach (Yao plot) gave a linear relationship between P(n+1)/O(n+1) and Pn/On indicating the inner constraints between the olefin and the paraffin product distribution.