Steam reforming of gasified biomass tar for hydrogen production over nickel- dolomite based catalyst

Abstract

Catalytic steam reforming is a promising approach to address tar formation and improve hydrogen (H2) production from biomass gasification. In this research, multi-compound tar model (phenol, toluene, naphthalene, and pyrene) was steam reformed for H2 production over various types of 10 wt.% dolomite promoted 10 wt.% nickel based catalysts supported on alumina, lanthana, ceria, and zirconia. The research aims to synthesize nickel-dolomite catalyst for steam reforming of gasified biomass tar for optimum H2 production. The catalysts were characterized by thermogravimetric analysis, temperature programmed reduction, temperature programmed desorption, nitrogen physisorption, and X-ray diffraction. The results showed that the addition of dolomite promoter to the catalysts strengthened the metal-support interaction and basicity of the catalyst. Steam reforming for catalyst screening was carried out at 700 oC with steam to carbon (S/C) molar ratio of 1 and gas hourly space velocity (GHSV) of 20,453 mL/h·gcat. The Ni/dolomite/La2O3 (NiDLa) catalyst displayed mesoporous structure, high reducibility, and basicity, which lead to superior carbon conversion to gas (77.66 mol%) and H2 yield (66.20 mol%). In addition, spent NiDLa exhibited the lowest amount of filamentous coke (110 mg/gcat) formation after 5 hours of reaction compared to the other catalysts investigated. Findings on effect of reaction condition revealed that higher temperature (> 750 oC), S/C ratio that is close to the stoichiometric value (1), and moderate GHSV (12,000 – 18,000 h-1) can improve carbon conversion to gas and H2 yield. The optimum conditions were found to be 775 oC of temperature, 1.02 of S/C molar ratio, and 14,648 h-1 of GHSV which resulted in 99.94 mol% of carbon conversion to gas and 82.84 mol% of H2 yield. This finding is close to the predicted 98.96 mol% of carbon conversion to gas and 82.00 mol% of H2 yield by response surface method.