Catalytic Steam Reforming Of Toluene As A Biomass Tar Model Compound

Gasification is the most promising method of converting biomass into syngas.However,the presence of tar in biomass gasification products is considered a major problem that still remaining to be solved.Among the different tar reduction methods,catalytic steam reforming is a favorable route for tar conversion to high energy syngas in the biomass gasification process.However,the catalyst deactivation caused by carbon deposition and metal sintering is still considered a major challenge need to be solved.In this work,two experimental studies were conducted to investigate the steam reforming of toluene as a biomass tar model compound over several catalysts.For the first experimental study,a modified Ni-based Ni-Co/Al2O3-CaO(Ni-Co/AC)catalyst and a conventional Ni/Al2O3(Ni/A)catalyst were prepared and tested for steam reforming of toluene as a biomass tar model compound.Experiments were conducted to reveal the influences of temperature and the steam to carbon(S/C)ratio on the toluene conversion and hydrogen yield.Moreover,a stability test for 40 hours was performed.In addition,the catalyst properties were characterized by a series of methods including temperature-programmed reduction of hydrogen(H2-TPR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and carbon content analysis.The results showed formation of Ni-Co alloy in the Ni-Co/AC catalyst.The addition of CaO and the presence of Ni-Co alloy promoted the catalytic performance of toluene conversion over Ni-Co/AC catalyst compared with that over Ni/A catalyst.After testing in steam for 40 hours,the carbon conversion over Ni-Co/Ac maintained above 86%and its resistance of carbon deposition was superior to the Ni/A catalyst.For the second experimental study,two catalysts derived from hydrotalcite-like compounds Co-CaO-Al2O3(15Co-Ca-Al)and Ni-CaO-Al2O3(15Ni-Ca-Al),besides a conventional Ni-Al2O3(15Ni-Al)catalyst,were prepared by co-precipitation method and tested for steam reforming of toluene as a biomass tar model compound.The catalysts that derived from hydrotalcite-like compounds exhibited a better catalytic activity than the conventional catalyst.On the other hand,all three catalysts showed a stable reforming activity for a period of 17 h.