Catalytic oxygenless steam cracking of syngas-containing benzene model tar compound over natural Fe-bearing silicate minerals

Abstract

In a prospect of identifying cheap and abundant mineral sources for biomass catalytic steam gasification, the catalytic steam reforming activity of two naturally-occurring iron-bearing mineral silicate ores containing chrysotile and lizardite, was probed using benzene model-tar compound co-mixed with simulated syngas at varying H2, CO, CO2, CH4 and steam compositions. Abundant intra-/extra-framework iron entwined within these silicates revealed remarkable steam cracking catalytic properties. The activity of the silicate ores was benchmarked against that of a common tar-cracking olivine catalyst at identical temperature, iron loading and particle size. Benzene conversion of chrysotile and chrysotile/lizardite ores exhibited up to a fourfold increase compared to olivine. Activity toward benzene and methane conversions, and coke formation were very sensitive to the ratio of reductive (H2 and CO) to oxidative (H2O and CO2) gases in syngas whereas benzene conversion of chrysotile and chrysotile/lizardite ores exhibited up to a fourfold increase compared to olivine. The reaction studies were interpreted in light of iron oxidation state and coordination, and reducibility and particle size of iron oxides as determined using Mössbauer spectroscopy, temperature-programmed reduction (TPR) and transmission electron microscopy (TEM).