Study On Ni-based Perovskite To Catalyze Bio-tar For Hydrogen-rich Syngas Production

Biomass energy is rich in China,and biomass gasification is one of best way to utilize biomass energy.However,biomass tar of toxic,difficulty transform and highly viscous are inevitable produced in the process of biomass gasification.Many issues have to consider because of biomass tar,including stable operation of biomass gasification,complex gas separation equipment and increase production costs.At the same time,biomass tar are main compostion,including acetic acid,acetone,toluene,phenol et al.It have higher energy density of hydrocarbon,and can effectively improve conversion efficiency of biomass when used as waste energy.In order to solve this issue,the a series of biomass tar model compounds,such as acetic acid,acetone and rice husk pyrolysis tar,were studied in this paper.Using biomass tar model compounds,La Ni O₃perovskite catalyst was discussed catalysis activity and mechanism for producing rich-hydrogen syngas.Meanwhile,improvement method of catalysis activity was studied,such as doped and loading.Basing on acetic acid as biomass tar model compound for studying steam reforming,the B-site doping of the La Ni O₃ perovskite catalyst can increase or decrease the catalysis activity of steam reforming due to the different B-site elements.Compared with the B-site doped La Ni_0.8M_0.2O₃（M=Fe,Co,Mn和Cu）perovskite,B-site doped Fe shows the higher surface adsorption energy with acetic acid and steam molecules.Higher surface adsorption energy indicate that catalytic conversion efficiency of acetic acid and steam is increased.In the other hand,the B-site doped Mn and Cu in La Ni O₃perovskite can break the thermodynamic balance of CH₄ decomposition reaction in the water-gas reforming process,resulting in carbon produced.Hence,B-site doped Mn and Cu could increase carbon deposition on the surface of the perovskite catalyst,decreasing catalytic activity.In the La Ni_xFe_1-xO₃（0≤x≤1）perovskite catalysts,the double metal bond of Ni-Fe can be formed,which easily release lattice oxygen.It can oxidizes the carbon deposition on the perovskite catalyst,maintaining catalytic stability.All of the La Ni_xFe_1-xO₃（0≤x≤1）perovskite catalysts,La Ni_0.8Fe_0.2O₃ perovskite catalytic shows great catalytic activity.At same time,the reaction parameters of steam reforming of acetic acid was studied with La Ni_0.8Fe_0.2O₃ perovskite catalyst,such as temperature and steam/carbon ratio（S/C）.The results show that the hydrogen-rich syngas is suitable production at 600℃and S/C=4.All of A-site doped La_0.8M_0.2Ni_0.8Fe_0.8O₃（M=Ca,Ce and Zr）perovskite catalysts,La_0.8Ce_0.2Ni_0.8Fe_0.2O₃ perovskite catalyst can be adjusted valence of Ni and Fe ion,improving conversion activity of acetic acid as biomass tar model compound to hydrogen-rich syngas.It is attributed that Ce doped can improves capacity of the electron and lattice oxygen transfer form the inside of the perovskite catalyst to the surface through oxygen vacancies,resulting in increasing catalytic activity.At the same time,the steam as reactant can supply lattice oxygen of lost in the perovskite catalyst for maintaining the perovskite structure.All of La_1-xCe_xNi_0.8Fe_0.2O₃（0≤x≤1）perovskite catalysts at blend of acetic acid and acetone,the different reaction pathway is shown compared with acetic or acetone.The addition of a little acetone into acetic acid promote formation of CH₃COO（9）group.This group in acetic acid convert to CH₃CO（9）group,which affects the subsequent series of dehydrogenation reactions and improves the hydrogen-rich syngas produce.However,there is an optimal blending ratio of acetic acid and acetone at 4:1,having a best gas yield of hydrogen and conversion.The highest conversion and hydrogen yield at blend ratio of acetic acid and acetone（4:1）,weight hourly space velocity(14.23h^-1)and temperature（600℃）.In the two-stage fixed bed and biomass tar produced by rice husk pyrolysis at450℃,0.1La Ni O₃/MCM-41 catalyst shows the best catalysis activity for producing hydrogen-rich syngas at 800℃,steam/carbon ratio（S/C=0.8）.At the optimal conditions,the gas yield of hydrogen shows decrease,while the gas yield of carbon monoxide shows increase with 0.1La Ni O₃/MCM-41 catalyst after five-time cycles.Among the liquid phase products,the 0.1La Ni O₃/MCM-41 catalyst shows a higher catalytic effect on the phenols.After five-time cycles,the content of phenol decrease significantly.In addition,the type of carbon deposition after five-time cycles is mainly amorphous carbon which is easy to eliminate.The reason could be related to the MCM-41 carrier.