Mossbauer Spectroscopy and Catalytic Reaction Studies of Chrysotile-Catalyzed Steam Reforming of Benzene

Chrysotile, a naturally occurring iron-bearing magnesium hydroxide phyllosilicate found in mine and milling residue heaps from southern Quebec, was tested for its potential use as a tar-cracking catalyst in biomass steam gasification. Interspersed within the chrysotile mineral, magnetite impurities were recognized to confer tar-cracking catalytic properties to the material. Chrysotile steam-reforming activity was probed using benzene model tar compound at various temperatures, gas hourly space velocities, and catalyst pretreatments. The activity of air-calcined chrysotile (converted to hematite-containing forsterite) was benchmarked against that of olivine catalyst with nearly equal iron content. Mossbauer spectroscopy combined with temperature programmed reduction studies, syngas yield, and benzene conversion responses enabled recognizing the role of the various oxidation states and coordination environments of iron as a function of pretreatment conditions of the catalyst. The study's findings were rationalized in terms of iron deportment and BET specific surface area of the minerals to explain the 5-fold increase of benzene conversion and syngas yield of chrysotile over olivine for similar gas hourly mass space velocities, temperatures, and particle sizes.