A series of metal-organic frameworks MOF-808-X(6-connected)were synthesized by regulating the ZrOCl2·8H2O/1,3,5-benzenetricarboxylic acid(BTC)molar ratio(X)and tested for the direct synthesis of dimethyl carbonat...A series of metal-organic frameworks MOF-808-X(6-connected)were synthesized by regulating the ZrOCl2·8H2O/1,3,5-benzenetricarboxylic acid(BTC)molar ratio(X)and tested for the direct synthesis of dimethyl carbonate(DMC)from CO2 and CH3OH with 1,1,1-trimethoxymethane(TMM)as a dehydrating agent.The effect of the ZrOCl2·8H2O/BTC molar ratio on the physicochemical properties and catalytic performance of MOF-808-X was investigated.Results showed that a proper ZrOCl2·8H2O/BTC molar ratio during MOF-808-X synthesis was fairly important to reduce the redundant BTC or zirconium clusters trapped in the micropores of MOF-808-X.MOF-808-4,with almost no redundant BTC or zirconium clusters trapped in the micropores,exhibited the largest surface area,micropore size,and the number of acidic-basic sites,and consequently showed the best activity among all MOF-808-X,with the highest DMC yield of 21.5% under the optimal reaction conditions.Moreover,benefiting from the larger micropore size,MOF-808-4 outperformed our previously reported UiO-66-24(12-connected),which had even more acidic-basic sites and larger surface area than MOF-808-4,mainly because the larger micropore size of MOF-808-4 provided higher accessibility for the reactant to the active sites located in the micropores.Furthermore,a possible reaction mechanism over MOF-808-4 was proposed based on the in situ FT-IR results.The effects of different reaction parameters on DMC formation and the reusability of MOF-808-X were also studied.展开更多
Composite solid base catalysts derived from Ca‐M‐Al(M=Mg,La,Ce,Y)layered double hydroxides(LDH)were synthesized,characterized and applied to the transesterification of methanol with propylene carbonate.X‐ray diffra...Composite solid base catalysts derived from Ca‐M‐Al(M=Mg,La,Ce,Y)layered double hydroxides(LDH)were synthesized,characterized and applied to the transesterification of methanol with propylene carbonate.X‐ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides.Compared with the Ca‐Al LDH catalyst,the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg,La or Ce.The catalytic performance of these catalysts increases in the order of Ca‐Y‐Al<Ca‐Al<Ca‐Ce‐Al<Ca‐La‐Al<Ca‐Mg‐Al,which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La.The Ca‐Mg‐Al catalyst shows the highest(Ca+Mg):Al atomic ratio,indicating that it likely contains more unsaturated O2?ions,providing it with the highest concentration of very strong basic sites.The recyclability of these catalysts is improved following the addition of Mg,La,Ce or Y,with the Ca‐Mg‐Al maintaining a high level of activity after ten recycling trials.X‐ray diffraction analyses of fresh and used Ca‐Mg‐Al demonstrate that this catalyst is exceptionally stable,which could be of value in practical applications related to heterogeneous catalysis.展开更多
Much attention has been paid for the synthesis of dimethyl carbonate(DMC) by urea indirect alcoholysis method, which had not been actually industrialized by now. The rigorous full process model was then necessary to o...Much attention has been paid for the synthesis of dimethyl carbonate(DMC) by urea indirect alcoholysis method, which had not been actually industrialized by now. The rigorous full process model was then necessary to optimize the process with heat integration. In this paper, a full process was designed and optimized for the DMC synthesis by urea indirect alcoholysis method based on Aspen Plus software.The technological analysis was developed to find how the process was influenced by the three main recycled materials of methanol, 1,2-propylene glycol(PG) and mixture of DMC–methanol. Simultaneously,the thermal optimization was taken into account for energy saving and the optimized process was proposed with heat integration. Moreover, the economic evaluation was implemented for the optimized process with total annualized cost(TAC) and cost of product(COP) according to the plant investment and operations. It was found that the 11.6% decrease in TAC was obtained for the optimized process compared to the original designed process. The COP analysis showed that the process was economically efficient for the production of DMC from urea and methanol.展开更多
A new improved tri-diagonal method was developed for the non-equilibrium stage model of the catalytic distillation by coupling consumptive reaction coefficient.The reactions in the distillation column were divided int...A new improved tri-diagonal method was developed for the non-equilibrium stage model of the catalytic distillation by coupling consumptive reaction coefficient.The reactions in the distillation column were divided into generative reaction and consumptive reac-tion.The non-equilibrium stage model was introduced for the catalytic distillation process of the dimethyl car-bonate(DMC)synthesis by urea methanolysis over solid based catalyst,and the improved tri-diagonal method was used to solve the model equations.Comparison of pre-dicted results with experiment data shows that the mean relative error of the yield of DMC was 3.78%under dif-ferent conditions such as different operating pressures and reaction temperatures.The improved tri-diagonal matrix method could avoid the negative values of the liquid com-positions during the calculations and restrain the fluc-tuation of compositions by slowing down the variations of the values in the iteration.The modeling results show that the improved tri-diagonal method was appropriate for system containing a wide range of boiling point com-ponents and a different rate of reactions.展开更多
基金financially supported by the Natural Science Foundation of Shanxi Province,China(201601D102006)the Science Foundation for Young Scientists of Shanxi Province,China(201701D221052)+2 种基金the National Natural Science Foundation of China(21776294)the Key Science and Technology Program of Shanxi Province,China(MD2014-09,MD2014-10)the Independent Research Project of the State Key Laboratory of Coal Conversion(2018BWZ002)~~
文摘A series of metal-organic frameworks MOF-808-X(6-connected)were synthesized by regulating the ZrOCl2·8H2O/1,3,5-benzenetricarboxylic acid(BTC)molar ratio(X)and tested for the direct synthesis of dimethyl carbonate(DMC)from CO2 and CH3OH with 1,1,1-trimethoxymethane(TMM)as a dehydrating agent.The effect of the ZrOCl2·8H2O/BTC molar ratio on the physicochemical properties and catalytic performance of MOF-808-X was investigated.Results showed that a proper ZrOCl2·8H2O/BTC molar ratio during MOF-808-X synthesis was fairly important to reduce the redundant BTC or zirconium clusters trapped in the micropores of MOF-808-X.MOF-808-4,with almost no redundant BTC or zirconium clusters trapped in the micropores,exhibited the largest surface area,micropore size,and the number of acidic-basic sites,and consequently showed the best activity among all MOF-808-X,with the highest DMC yield of 21.5% under the optimal reaction conditions.Moreover,benefiting from the larger micropore size,MOF-808-4 outperformed our previously reported UiO-66-24(12-connected),which had even more acidic-basic sites and larger surface area than MOF-808-4,mainly because the larger micropore size of MOF-808-4 provided higher accessibility for the reactant to the active sites located in the micropores.Furthermore,a possible reaction mechanism over MOF-808-4 was proposed based on the in situ FT-IR results.The effects of different reaction parameters on DMC formation and the reusability of MOF-808-X were also studied.
基金supported by the Natural Science Foundation of Shanxi Province(201601D102006)the Key Science and Technology Program of Shanxi Province,China(MD2014-09,MD2014-10)~~
文摘Composite solid base catalysts derived from Ca‐M‐Al(M=Mg,La,Ce,Y)layered double hydroxides(LDH)were synthesized,characterized and applied to the transesterification of methanol with propylene carbonate.X‐ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides.Compared with the Ca‐Al LDH catalyst,the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg,La or Ce.The catalytic performance of these catalysts increases in the order of Ca‐Y‐Al<Ca‐Al<Ca‐Ce‐Al<Ca‐La‐Al<Ca‐Mg‐Al,which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La.The Ca‐Mg‐Al catalyst shows the highest(Ca+Mg):Al atomic ratio,indicating that it likely contains more unsaturated O2?ions,providing it with the highest concentration of very strong basic sites.The recyclability of these catalysts is improved following the addition of Mg,La,Ce or Y,with the Ca‐Mg‐Al maintaining a high level of activity after ten recycling trials.X‐ray diffraction analyses of fresh and used Ca‐Mg‐Al demonstrate that this catalyst is exceptionally stable,which could be of value in practical applications related to heterogeneous catalysis.
基金Supported by the Science Foundation for Young Scientists of Shanxi Province,China(201701D221052)Natural Science Foundation of Shanxi Province(201601D102006)the Key Science and Technology Program of Shanxi Province,China(MD2014-09,MD2014-10)
文摘Much attention has been paid for the synthesis of dimethyl carbonate(DMC) by urea indirect alcoholysis method, which had not been actually industrialized by now. The rigorous full process model was then necessary to optimize the process with heat integration. In this paper, a full process was designed and optimized for the DMC synthesis by urea indirect alcoholysis method based on Aspen Plus software.The technological analysis was developed to find how the process was influenced by the three main recycled materials of methanol, 1,2-propylene glycol(PG) and mixture of DMC–methanol. Simultaneously,the thermal optimization was taken into account for energy saving and the optimized process was proposed with heat integration. Moreover, the economic evaluation was implemented for the optimized process with total annualized cost(TAC) and cost of product(COP) according to the plant investment and operations. It was found that the 11.6% decrease in TAC was obtained for the optimized process compared to the original designed process. The COP analysis showed that the process was economically efficient for the production of DMC from urea and methanol.
基金support from the National Science Key Foundation(Grant No.2006BAC02A08)was acknowledged.
文摘A new improved tri-diagonal method was developed for the non-equilibrium stage model of the catalytic distillation by coupling consumptive reaction coefficient.The reactions in the distillation column were divided into generative reaction and consumptive reac-tion.The non-equilibrium stage model was introduced for the catalytic distillation process of the dimethyl car-bonate(DMC)synthesis by urea methanolysis over solid based catalyst,and the improved tri-diagonal method was used to solve the model equations.Comparison of pre-dicted results with experiment data shows that the mean relative error of the yield of DMC was 3.78%under dif-ferent conditions such as different operating pressures and reaction temperatures.The improved tri-diagonal matrix method could avoid the negative values of the liquid com-positions during the calculations and restrain the fluc-tuation of compositions by slowing down the variations of the values in the iteration.The modeling results show that the improved tri-diagonal method was appropriate for system containing a wide range of boiling point com-ponents and a different rate of reactions.
