Hydrogen-rich gas production by steam reforming of gasified biomass tar over Ni/dolomite/La2O3 catalyst

Abstract

The steam reforming of gasified biomass tar model that consists of phenol, toluene, naphthalene, and pyrene over Ni/dolomite/La2O3 (NiDLa) catalyst was performed in a fixed bed reactor. The effect of reaction temperature (500-900 °C), steam to carbon (S/C) molar ratio (0.5-2.5), and gas hourly space velocity (GHSV) (8,000-22000 h-1) on hydrogen (H2) yield, carbon conversion to gas, molar composition of product gas, turnover frequency for H2(TOFH2), and deactivation was investigated. The fresh and spent catalysts were characterized by H2-TPD, FE-SEM, EDX, TGA, and XRD. High efficiency of NiDLa catalyst for H2 production via steam reforming of tar was observed at 750 °C with S/C molar ratio of 1 and GHSV of 14,000 h-1. At these conditions, the carbon to gas conversion, H2 yield, and TOFH2 were 89 mol%, 81 mol%, and 3.57 min-1, respectively. Findings on the effect of reaction conditions revealed that higher temperatures (> 750 °C), S/C ratios that closed to the stoichiometric value (1), and moderate GHSV (12,000-18,000 h-1) improved carbon conversion to gas and H2 yield. Likewise, the coke formation over the catalyst increased at lower reaction temperatures, S/C ratios, and GHSV. XRD analysis showed that Ni metal was oxidized after steam reforming at higher S/C ratio.