Levulinic acid(LA)is a platform biorefinery chemical from biomass which can be converted to green solvents,plasticizers,polymer precursors,biobased cleaning agents,fuels and fuel additives.This study assessed the pote...Levulinic acid(LA)is a platform biorefinery chemical from biomass which can be converted to green solvents,plasticizers,polymer precursors,biobased cleaning agents,fuels and fuel additives.This study assessed the potential of SnCl_(2)-based mixed acid systems as catalyst in the hydrothermal conversion of microcrystalline cellulose to levulinic acid.Maximum LAyield of 36.2 mol%was achieved using 0.2 M SnCl_(2) concentration at test conditions of 3 h,180℃ and 1%w/v cellulose loading.To reduce precipitate formation and further improve LA yield,the strategy employed was to combine SnCl_(2)(a Lewis acid)with conventional mineral acids(Bronsted acids).Evaluation of the catalytic performance of SnCl_(2)-HCl,SnCl_(2)-H_(2)SO_(4),SnCl_(2)-HNO_(3),and SnCl_(2)-H_(3)PO_(4)(1:1 molar ratio,0.2 M total acid concentration)were done with highest LA yield of 47.0 mol%obtained using the SnCl_(2)-HCl system at same test conditions.Response surface methodology optimization employing Box-Behnken design generated a quadratic model with a high coefficient of determination(r2)of 0.964.A maximum LA yield of 63.5 mol%can be achieved at 0.17 M catalyst concentration,198℃,and 5.15 h reaction time.Rate constants were estimated using nonlinear regression,while activation energies were determined using Arrhenius equation.Cellulose hydrolysis was determined to be the rate-limiting step in the overall process.Low activation energy of 63.3 kJ/mol for glucose dehydration to hydroxymethylfurfural supports the action of SnCl_(2) as Lewis acid in the mixed-acid system.LA yield simulations for plug flow reactor(PFR)and continuous stirred tank reactor(CSTR)were done suggesting a similar PFR-CSTR configuration with the established Biofine process.Lastly,a reaction scheme was presented to explain the synergy between SnCl_(2) and HCl in LA production from cellulose.展开更多
Tin perovskite solar cells(TPSCs)are promising for lead-free perovskite solar cells(PSCs)and have led to extensive research;however,the poor crystallinity and chemical stability of tin perovskites are two issues that ...Tin perovskite solar cells(TPSCs)are promising for lead-free perovskite solar cells(PSCs)and have led to extensive research;however,the poor crystallinity and chemical stability of tin perovskites are two issues that prevent stable TPSCs.In this study,we outline a new process that addresses these issues by using tin(II)acetate(Sn(Ac)2)in place of the conventional SnF2 precursor additive.Compared with SnF2,Sn(Ac)2 improves the crystallinity and stability of tin perovskite with fewer defects and better charge extraction.Using this process,we developed a device that has a higher external quantum efficiency for charge extraction compared with the control devices and a power conversion efficiency of 9.93%,which maintained more than 90%of its initial efficiency after 1000 h operation at the maximum power point under standard AM 1.5G solar illumination.展开更多
文摘Levulinic acid(LA)is a platform biorefinery chemical from biomass which can be converted to green solvents,plasticizers,polymer precursors,biobased cleaning agents,fuels and fuel additives.This study assessed the potential of SnCl_(2)-based mixed acid systems as catalyst in the hydrothermal conversion of microcrystalline cellulose to levulinic acid.Maximum LAyield of 36.2 mol%was achieved using 0.2 M SnCl_(2) concentration at test conditions of 3 h,180℃ and 1%w/v cellulose loading.To reduce precipitate formation and further improve LA yield,the strategy employed was to combine SnCl_(2)(a Lewis acid)with conventional mineral acids(Bronsted acids).Evaluation of the catalytic performance of SnCl_(2)-HCl,SnCl_(2)-H_(2)SO_(4),SnCl_(2)-HNO_(3),and SnCl_(2)-H_(3)PO_(4)(1:1 molar ratio,0.2 M total acid concentration)were done with highest LA yield of 47.0 mol%obtained using the SnCl_(2)-HCl system at same test conditions.Response surface methodology optimization employing Box-Behnken design generated a quadratic model with a high coefficient of determination(r2)of 0.964.A maximum LA yield of 63.5 mol%can be achieved at 0.17 M catalyst concentration,198℃,and 5.15 h reaction time.Rate constants were estimated using nonlinear regression,while activation energies were determined using Arrhenius equation.Cellulose hydrolysis was determined to be the rate-limiting step in the overall process.Low activation energy of 63.3 kJ/mol for glucose dehydration to hydroxymethylfurfural supports the action of SnCl_(2) as Lewis acid in the mixed-acid system.LA yield simulations for plug flow reactor(PFR)and continuous stirred tank reactor(CSTR)were done suggesting a similar PFR-CSTR configuration with the established Biofine process.Lastly,a reaction scheme was presented to explain the synergy between SnCl_(2) and HCl in LA production from cellulose.
基金the National Natural Science Foundation of China(11834011 and 11911530142)。
文摘Tin perovskite solar cells(TPSCs)are promising for lead-free perovskite solar cells(PSCs)and have led to extensive research;however,the poor crystallinity and chemical stability of tin perovskites are two issues that prevent stable TPSCs.In this study,we outline a new process that addresses these issues by using tin(II)acetate(Sn(Ac)2)in place of the conventional SnF2 precursor additive.Compared with SnF2,Sn(Ac)2 improves the crystallinity and stability of tin perovskite with fewer defects and better charge extraction.Using this process,we developed a device that has a higher external quantum efficiency for charge extraction compared with the control devices and a power conversion efficiency of 9.93%,which maintained more than 90%of its initial efficiency after 1000 h operation at the maximum power point under standard AM 1.5G solar illumination.
