This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oi...This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.展开更多
Electron-phonon coupling(EPC)is a key factor for thermoelectric properties of materials.In this paper,the thermoelectric properties of zinc-blende chalcogenides(p-type)ZnS and ZnSe have been studied through full evalu...Electron-phonon coupling(EPC)is a key factor for thermoelectric properties of materials.In this paper,the thermoelectric properties of zinc-blende chalcogenides(p-type)ZnS and ZnSe have been studied through full evaluation of EPC from first-principles,including the influences on both electrical and thermal transport.We find that the polar longitudinal optical phonon scattering is the dominant mechanism for electrical transport.Due to the triple degeneracy near the valence band maximum,the inter-band scattering also has detrimental contributions to the electrical conductivities.For phonon transport,it shows that the lattice thermal conductivity can be reduced by the electron-phonon scattering significantly at high carrier concentrations(e.g.,at 300 K with 10^(21) cm^(3) of hole,the reduction is-24.9%for ZnS and-28.4%for ZnSe,respectively).Finally,the p-type thermoelectric figure of merit(ZT)of two systems have been obtained,which are 0.129 for ZnS and 0.141 for ZnSe,at 700 K with their respective optimal hole concentrations.Our work provides a complete and in-depth study of thermoelectric properties in chalcogenides ZnX from the role of EPC.The results suggest EPC plays an important role on the thermoelectric properties and thus full evaluation of EPC is necessary especially for polar materials.展开更多
基金support from the Natural Science Foundation of Shandong Province (Grant no.ZR2013BL010)the Research Excellence Award of Shandong University of Technology and the Zibo Technology Research and Development Program of China (Grant no.2013GG04110)
文摘This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.
基金supported by the National Key Research and Development Program of China(No.2017YFB0701600 and 2018YFB0703600)the National Natural Science Foundation of China(Grant Nos.21703136,51761135127,and 11674211)the 111 Project D16002.J.Y.X.acknowledges the support from the Shanghai Sailing Program,China(17YF1427900)。
文摘Electron-phonon coupling(EPC)is a key factor for thermoelectric properties of materials.In this paper,the thermoelectric properties of zinc-blende chalcogenides(p-type)ZnS and ZnSe have been studied through full evaluation of EPC from first-principles,including the influences on both electrical and thermal transport.We find that the polar longitudinal optical phonon scattering is the dominant mechanism for electrical transport.Due to the triple degeneracy near the valence band maximum,the inter-band scattering also has detrimental contributions to the electrical conductivities.For phonon transport,it shows that the lattice thermal conductivity can be reduced by the electron-phonon scattering significantly at high carrier concentrations(e.g.,at 300 K with 10^(21) cm^(3) of hole,the reduction is-24.9%for ZnS and-28.4%for ZnSe,respectively).Finally,the p-type thermoelectric figure of merit(ZT)of two systems have been obtained,which are 0.129 for ZnS and 0.141 for ZnSe,at 700 K with their respective optimal hole concentrations.Our work provides a complete and in-depth study of thermoelectric properties in chalcogenides ZnX from the role of EPC.The results suggest EPC plays an important role on the thermoelectric properties and thus full evaluation of EPC is necessary especially for polar materials.
