Efficient utilization of bimetallic catalyst in low $$\hbox {H}_{2}/\hbox {CO}$$ H 2 / CO environment syngas for liquid fuel production

Abstract

Application of Fischer-Tropsch synthesis (FTS) in the utilization of low $$\hbox {H}_{2}/\hbox {CO}$$ ratio (0.5–1.5) gas obtained from coal and biomass gasification can be done by selecting a catalyst system active for both FTS and WGS reaction. The enhancement of $$\hbox {H}_{2}$$ content depends on the extent of water gas shift (WGS) reaction and can be quantified by measuring usage ratio define as a mole of $$\hbox {H}_{2}$$ to CO converted. With an attempt to utilize low $$\hbox {H}_{2}/\hbox {CO}$$ ratio syngas bimetallic $$(\hbox {Fe}/\hbox {Co}/\hbox {SiO}_{2})$$ were prepared and compared with monometallic ( $$\hbox {Fe}/\hbox {SiO}_{2}$$ and $$\hbox {Co}/\hbox {SiO}_{2}$$ ) catalysts. The catalysts were tested in fixed bed reactor at industrial relevant FTS conditions (T: $$220{-}260\,^{\circ }\hbox {C}$$ , P: 2.0 MPa, GHSV-1.2 SL/gcat-h, $$\hbox {H}_{2}/\hbox {CO}$$ : 1–1.5). The incorporation of Fe-Co bimetallic catalyst facilitates both FT and WGS reaction because of the presence of iron and cobalt phases. Compared to monometallic catalyst there is a significant increase in CO conversion over the bimetallic catalyst. Also, the yield of $$\hbox {C}_{5+}$$ was significantly higher over bimetallic catalyst compared to iron catalyst, where olefin was the major product. Selected catalyst $$(\hbox {Fe}/\hbox {Co}/\hbox {SiO}_{2})$$ was tested for their activity toward WGS reaction. Effects of temperature, pressure, and feed composition on WGS reaction over bimetallic catalyst were studied. Lower value usage ratio (1.62 and 1.58) reveals the occurrence WGS reaction Fe-Co bimetallic catalyst at 240 $$^{\circ }\hbox {C}$$ and 260 $$^{\circ }\hbox {C}$$ . At 240 $$^{\circ }\hbox {C}$$ , 72% CO conversion, and 60% $$\hbox {C}_{5+}$$ selectivity show that the catalyst efficiently utilizes the increased $$\hbox {H}_{2}/\hbox {CO}$$ ratio in the production of liquid hydrocarbon. Synopsis: A novel Fe-Co catalyst combination has been optimised for the conversion of biomass derived syngas, having low $$\hbox {H}_{2}/\hbox {CO}$$ ratio (1– 1.5mol/mol). The addition of iron onto silica supported cobalt catalyst facilitates the WGS reaction activity for higher $$\hbox {H}_{2}/\hbox {CO}$$ ratio internally and thus improves FTS activity. $$\hbox {10Fe}/\hbox {20Co}/\hbox {SiO}_{2}$$ catalyst resulted optimum WGS and FTS activity with 72% CO conversion, and 60% $$\hbox {C}_{5+}$$ selectivity.