Characteristic Study On The Catalytic Reforming Of Biomass Tar By Modified Nickel-based Catalyst

Biomass can be widely utilized to produce syngas through pyrolysis and gasification technologies,which is one of the most important technical choices to achieve the strategic carbon peaking and carbon neutrality goals.However,along with the biomass syngas,biomass tar is also generated due to the incomplete cracking of the organic components in biomass,which not only affects the efficiency of biomass conversion but also causes corrosion and blockage of the facilities.Therefore,the removal of tar is very important for the generation of biomass syngas.Catalytic reforming is an efficient method for the abatement of biomass tar.Among the reforming catalysts,Nickel-based catalysts have the most developing potential,but many problems cause their deactivation,such as sintering and carbon deposition.In comparison with other metal oxides,TiO2 as the support of a nickelbased catalyst can not only enhance the reducibility of the catalyst but also has the advantage of delaying the formation of coke.However,the Ni/TiO2 catalyst still has problems including large crystal sizes and poor dispersibility of Ni components,which affects the activity and stability of the catalyst.In this study,two modifying methods,including the addition of metal promoter and the modification of carrier,were proposed to improve the catalytic activity and carbon deposition resistance during the catalytic reforming of biomass tar over the Ni/TiO2 catalyst,with benzene as the model compound.In addition,the mechanisms of the above modifying methods on the physicochemical property and catalytic performance of the catalyst were also revealed.Firstly,the effect of metal promoter modification on the performance of Ni/TiO2 catalyst was investigated,including the performance of benzene steam catalytic reforming under different metal promoters,loading amounts,reaction temperatures,and steam-to-carbon molar ratios(S/C).The results showed that the Fe promoter could not only promote the conversion of benzene to H2-rich biomass syngas but also significantly inhibit the formation of carbon on the catalysts surface.When the reaction temperature was 800℃ and the S/C was 1.00.the benzene conversion ratio and H2 yield reached 96.3 1%and 102.53 mmol/gbenzene,respectively.After the modification of the Fe promoter,the Ni-Fe alloys were formed,which improved the dispersion of Ni and enhanced the activity of the catalyst.In addition,the surface adsorption of H2O molecules was enhanced,which was beneficial to the catalytic reforming of benzene.Moreover,the formation of lattice oxygen was also promoted,which enhanced the oxidation of amorphous carbon and inhibited the formation of graphite carbon,thus protecting the active site Ni from carbon deposition.Therefore,the anti-carbon deposition capability of the Ni/TiO2 catalyst was improved.Secondly,the effect of carrier modification on the performance and stability of the Ni/TiO2 catalyst was investigated.The results showed that 10i/1TiO20.30SiO2 catalyst has better activity than Ni/TiO2 catalyst,with the conversion ratio of benzene and the yield of H2 in the biomass gases respectively reaching 61.48%and 49.89 mmol/gbenzene.In addition,the SiO2 modification significantly improved the thermal stability of the catalyst,which was stable in the reforming duration of more than 14 h.The characterization results revealed that the addition of SiO2 increased the catalyst’s specific surface area,and reduced the crystal size of Ni,thereby promoting the dispersion of active Ni sites.Meanwhile,the modification of SiO2 enhanced the reducibility of the catalyst and promoted the formation of the metal Ni.In addition,the acidity of the catalyst was also weakened after the SiO2 modification,which inhibited the accumulation of carbon deposition.Therefore,the activity and anti-carbon deposition capability of the modified Ni/TiO2-SiO2 catalyst was significantly improved.