Biomass gasification process generates the residual tar,which in turn exerts some negative influence on biomass gasification system.To reduce this harmful influence,an evaluation of the tar properties during the bioma...Biomass gasification process generates the residual tar,which in turn exerts some negative influence on biomass gasification system.To reduce this harmful influence,an evaluation of the tar properties during the biomass gasification was studied.The chemical composition and pyrolysis behavior of biomass tar were investigated.The complex chemical composition of the tar,which includes phenol derivatives,naphthalene derivatives,other macromolecular aromatic compounds,furans,and other compounds(carbon number from 7 to 14),was established by gas chromatography-mass spectrometry technique.Thermogravimetric analysis was performed with two heating rates(10℃/min and 20℃/min),and Coats-Redfern method was applied to assess the kinetic parameters,i.e.,the activation energy(E)and pre-exponential factor(A)of tar thermochemical decomposition.The results showed that the main degradation of tar is a two-step process,including a volatilization step at lower temperatures(<105℃)and a pyrolysis step at higher temperatures(105℃-380℃).The application of the Coats-Redfern method revealed a variation trend of the activation energy during the decomposition of tar in a non-isothermal model.It shows that high temperature is more conducive to tar pyrolysis.By adjusting the temperature to control the generation and removal of tar,new approaches are provided for designing and optimizing biomass gasification systems.展开更多
Photocatalytic ammonia generation via nitrogen reduction reaction(NRR)is a green and prospective nitrogen fixation technique.However,NRR is often hampered by the high N_(2) adsorption/activation energies and is accomp...Photocatalytic ammonia generation via nitrogen reduction reaction(NRR)is a green and prospective nitrogen fixation technique.However,NRR is often hampered by the high N_(2) adsorption/activation energies and is accompanied by a slow kinetics oxygen evolution reaction(OER).Herein,a robust Bi_(2)S_(3)/OVBi_(2)MoO_(6)S-scheme heterojunction is constructed using a simple in-situ anion exchange process,which enables oxygen vacancy(OVs)abundant Bi_(2)Mo O_(6) microspheres with surface deposited Bi_(2)S_(3).The asfabricated Bi_(2)S_(3)/OVBi_(2)MoO_(6) functioned as an effective photocatalyst to convert N_(2)-to-NH_(3) under mild conditions.The photocatalytic NH_(3)/NH_(4)^(+) production rate reached 126μmol g_(cat)^(-1)under visible light for2.5 h with 2%of Bi_(2)S_(3)/OVBi_(2)MoO_(6)photocatalyst,which was 8-fold higher than pristine Bi_(2)MoO_(6).Furthermore,the as-fabricated Bi_(2)S_(3)/Bi_(2)MoO_(6)heterojunction exhibited good selectivity,high stability and reproducibility.The excellent photocatalytic NRR performance was ascribed to the Bi_(2)S_(3)/Bi_(2)MoO_(6)heterojunction formed subsequent to the strong interaction between Bi_(2)S_(3)and Bi_(2)MoO_(6).The OVs facilitated the chemical adsorption process allowing activation of N_(2)molecule on the Bi_(2)S_(3)/Bi_(2)MoO_(6).Simultaneously,the S-scheme heterojunction prolonged the lifetime of photogenerated carriers,accelerated the electrons/holes spatial separation and accumulation on the Bi_(2)S_(3)(reduction)and Bi_(2)MoO_(6)side(oxidation),respectively,thus strengthening both OER and NRR half-reactions.This simple in-situ anion exchange method offers a novel technique for strengthening OER and NRR half-reactions in Bi-based photocatalysts for effective photocatalytic ammonia generation.展开更多
基金supported by the Key R&D Projects in Henan Province(Grant No.241111321700)the Major Science and Technology Projects in Henan Province(Grant No.231100110200)the Key Scientific and Technological Project of Henan Province(Grant No.232102240040,232102110291).
文摘Biomass gasification process generates the residual tar,which in turn exerts some negative influence on biomass gasification system.To reduce this harmful influence,an evaluation of the tar properties during the biomass gasification was studied.The chemical composition and pyrolysis behavior of biomass tar were investigated.The complex chemical composition of the tar,which includes phenol derivatives,naphthalene derivatives,other macromolecular aromatic compounds,furans,and other compounds(carbon number from 7 to 14),was established by gas chromatography-mass spectrometry technique.Thermogravimetric analysis was performed with two heating rates(10℃/min and 20℃/min),and Coats-Redfern method was applied to assess the kinetic parameters,i.e.,the activation energy(E)and pre-exponential factor(A)of tar thermochemical decomposition.The results showed that the main degradation of tar is a two-step process,including a volatilization step at lower temperatures(<105℃)and a pyrolysis step at higher temperatures(105℃-380℃).The application of the Coats-Redfern method revealed a variation trend of the activation energy during the decomposition of tar in a non-isothermal model.It shows that high temperature is more conducive to tar pyrolysis.By adjusting the temperature to control the generation and removal of tar,new approaches are provided for designing and optimizing biomass gasification systems.
基金financially supported by the National Natural Science Foundation of China(Nos.22168040,21666039,21663030)the Open Project of State Key Laboratory of Organic-Inorganic Composites Beijing Key Laboratory,Beijing University of Chemical Technology Beijing(No.oic-201901009)+3 种基金the Project of Science&Technology Office of Shaanxi Province(Nos.2018TSCXL-NY-02–01,2020JQ-791)the Project of Yan’an Science and Technology Bureau(No.2018KG-04)the Graduate Innovation Project of Yan’an University(No.YCX2020005)the Open Project of Chongqing Key Laboratory of Inorganic Special Functional Materials,Yangtze Normal University(No.KFKT202001)。
文摘Photocatalytic ammonia generation via nitrogen reduction reaction(NRR)is a green and prospective nitrogen fixation technique.However,NRR is often hampered by the high N_(2) adsorption/activation energies and is accompanied by a slow kinetics oxygen evolution reaction(OER).Herein,a robust Bi_(2)S_(3)/OVBi_(2)MoO_(6)S-scheme heterojunction is constructed using a simple in-situ anion exchange process,which enables oxygen vacancy(OVs)abundant Bi_(2)Mo O_(6) microspheres with surface deposited Bi_(2)S_(3).The asfabricated Bi_(2)S_(3)/OVBi_(2)MoO_(6) functioned as an effective photocatalyst to convert N_(2)-to-NH_(3) under mild conditions.The photocatalytic NH_(3)/NH_(4)^(+) production rate reached 126μmol g_(cat)^(-1)under visible light for2.5 h with 2%of Bi_(2)S_(3)/OVBi_(2)MoO_(6)photocatalyst,which was 8-fold higher than pristine Bi_(2)MoO_(6).Furthermore,the as-fabricated Bi_(2)S_(3)/Bi_(2)MoO_(6)heterojunction exhibited good selectivity,high stability and reproducibility.The excellent photocatalytic NRR performance was ascribed to the Bi_(2)S_(3)/Bi_(2)MoO_(6)heterojunction formed subsequent to the strong interaction between Bi_(2)S_(3)and Bi_(2)MoO_(6).The OVs facilitated the chemical adsorption process allowing activation of N_(2)molecule on the Bi_(2)S_(3)/Bi_(2)MoO_(6).Simultaneously,the S-scheme heterojunction prolonged the lifetime of photogenerated carriers,accelerated the electrons/holes spatial separation and accumulation on the Bi_(2)S_(3)(reduction)and Bi_(2)MoO_(6)side(oxidation),respectively,thus strengthening both OER and NRR half-reactions.This simple in-situ anion exchange method offers a novel technique for strengthening OER and NRR half-reactions in Bi-based photocatalysts for effective photocatalytic ammonia generation.
