Nickel and Iron Biocarbon Catalysts for Water-Gas Shift Reaction
Résumé
Biocarbon catalysts for water-gas shift (WGS) reaction were prepared from pyrolyzed fern (F) impregnated with iron (Fe) and nickel (Ni) salts. They were tested in a fixed-bed reactor from 180 °C to 400 °C with variable steam to carbon monoxide (S/CO) ratio (1.4 to 20.7) and compared to rust. CO conversion was mostly below 10% and favored by increasing temperature and steam partial pressure relative to WGS kinetics. Ni-biocarbon catalysts were more active for WGS due to their lower temperature activity, according to their reducibility and inherent metals which improved electronic properties. WGS selectivity was generally above 95%, reflecting WGS predominance over methanation. FNiFe-B (impregnated before pyrolysis) was the most performant catalyst (10.3% conversion, 99.7% selectivity, 280 °C). Maximal rust conversion was 6.9% at 280 °C, compared to 20% at 300 °C in the literature. Catalyst activation energy and pre-exponential factor of 92.1 kJ/mol and 2.2 × 108 respectively were determined, and comparable to literature (up to 130 kJ/mol; 5.8 × 1010). Low temperature activity provided by Ni combined with Fe and fern-inherent metals’ co-catalytic effect was reflected in the high WGS performance by FNiFe-B with its associated kinetic parameters (59.5 kJ/mol; 5.6 × 105).