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The influence of the reduction gas (H2 or Syngas) on the performance of a precipitated iron FT catalyst

Yali Yao
Centre of Material and Process Synthesis (COMPS)
School of Chemical and Metallurgical Engineering
University of the Witwatersrand, Johannesburg

November 8, 2012 at 10:00am
Ben Bandy Conference Center
UK Center for Applied Energy Research

Iron-based catalysts are low cost, demonstrate high activity for both Fischer-Tropsch (FT) and water-gas shift (WGS) reactions, and are therefore attractive to use with syngases with low H2/CO ratios in the FT process. Catalyst activation is always required before the FT reaction, which consists of reducing the catalyst using an appropriate reducing agent. For industrial applications, pure H2 for catalyst reduction is usually expensive and operationally inconvenient. Economic benefits can potentially be obtained if the same syngas used for the normal FT reaction can also be used to activate the catalyst at the normal FT reaction temperature. It is therefore interesting to compare the catalyst performance of a syngas reduced catalyst to that of a H2 reduced catalyst.

The present work focuses on a systematic understanding of the effects of the activating agents, H2 and syngas, on the catalytic performances of a precipitated iron catalyst over long term operation. Two fixed bed reactors, each loaded with 1 gram of precipitated iron catalyst, were used for the low temperature FTS: (1) reactor 1 was reduced by H2 at atmospheric pressure, a temperature of 330 degrees C and flow rate of 60 mL(NTP)/(minogcat) for 48 hrs; and (2) reactor 2 was reduced by syngas at atmospheric pressure, temperature of 250 degrees C and flow rate of 60 mL(NTP)/(minogcat) for 48 hrs. After the reduction, the same FT reaction procedures were carried out for both of the reactors. The reactions have been running for period of more than 7 months (>5000 hrs) for each of the reactors; and the catalyst activity, selectivity and its life data are measured and compared.