SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and ch...SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and characterized by XRD,BET and TEM.The catalytic reaction was carried out in a fixed-bed reactor.Overall,the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene.Among the four Pd catalysts on low specific surface area supports,the catalyst on low specific surface area SiO2(LSA-SiO2) retained a high ethylene selectivity even at complete conversion,while the other catalysts showed significant decrease in the selectivity at complete conversion.The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene.Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane,C4 alkenes and green oil,and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(ω).When the ratio of Pd to Ag was above 1,the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst,and the selectivity of ethylene increased with increasing of amount of Ag.When the ratio of Pd to Ag was below 1,the activity of bimetallic catalyst decreased with increasing of amount of Ag,while the selectivity of ethylene was kept unchanged.The optimum temperature was 200-230℃ for 0.02%(ω)Pd-0.02%(ω)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.展开更多
The hydrogenation of SiCl_4 to SiHCl_3 was studied in a stirred bed reactor with CuCl catalyst.The properties of the CuCl catalysts and silicon particles before and after the reaction were characterized by SEM,XRD and...The hydrogenation of SiCl_4 to SiHCl_3 was studied in a stirred bed reactor with CuCl catalyst.The properties of the CuCl catalysts and silicon particles before and after the reaction were characterized by SEM,XRD and XPS.The XRD showed that the active component of Cu3Si was formed during the reaction,and the EDX proved the molar ratio of Cu and Si on the region of apertures.The valent of Cu was discussed by XPS before and after the hydrogen reaction.Then the effects of the reaction temperature,pressure,molar ratio of H2 to SiC l4,weight hourly space velocity(WHSV),and catalyst loading were studied.The results showed that the conversion rate of Si Cl4 was about 38%at WHSV of 190 Nm3/(t·h),temperature of 540℃,pressure of 1.8 MPa,catalyst loading of 0.9%(ω),and molar ratio of H2 to Si Cl4 1.7:1.Based on the experemental results,a reaction mechanism was proposed,which involved the continuous consumption of silicon(many apertures was showed on SEM image)and formation of new Cu3Si active component during the hydrogenation reaction.展开更多
Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of different factors ...Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of different factors on the epoxidation of three unsaturated natural products were investigated by orthogonal design.Results The experimental results show that three unsaturated natural products are oxidized to the corresponding epoxides with hydrogen peroxide in the presence of 10%(mol/mol) of iodine at room temperature in high yields.Conclusion Iodine was found to be an efficient catalyst for the epoxidation of carbon-carbon double bonds in some unsaturated natural products with hydrogen peroxide at room temperature.展开更多
Abstract :The principle of processing popped ricecake, especially bymicrowave, was expounded. Then the relations between popping time,materials ratio, H20 content of biscuit-base and the crisp degree and poppingdegree...Abstract :The principle of processing popped ricecake, especially bymicrowave, was expounded. Then the relations between popping time,materials ratio, H20 content of biscuit-base and the crisp degree and poppingdegree of ricecake were discussed. The microwave popping and oil-fry poppingwere compared as well.展开更多
文摘SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and characterized by XRD,BET and TEM.The catalytic reaction was carried out in a fixed-bed reactor.Overall,the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene.Among the four Pd catalysts on low specific surface area supports,the catalyst on low specific surface area SiO2(LSA-SiO2) retained a high ethylene selectivity even at complete conversion,while the other catalysts showed significant decrease in the selectivity at complete conversion.The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene.Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane,C4 alkenes and green oil,and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(ω).When the ratio of Pd to Ag was above 1,the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst,and the selectivity of ethylene increased with increasing of amount of Ag.When the ratio of Pd to Ag was below 1,the activity of bimetallic catalyst decreased with increasing of amount of Ag,while the selectivity of ethylene was kept unchanged.The optimum temperature was 200-230℃ for 0.02%(ω)Pd-0.02%(ω)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.
文摘The hydrogenation of SiCl_4 to SiHCl_3 was studied in a stirred bed reactor with CuCl catalyst.The properties of the CuCl catalysts and silicon particles before and after the reaction were characterized by SEM,XRD and XPS.The XRD showed that the active component of Cu3Si was formed during the reaction,and the EDX proved the molar ratio of Cu and Si on the region of apertures.The valent of Cu was discussed by XPS before and after the hydrogen reaction.Then the effects of the reaction temperature,pressure,molar ratio of H2 to SiC l4,weight hourly space velocity(WHSV),and catalyst loading were studied.The results showed that the conversion rate of Si Cl4 was about 38%at WHSV of 190 Nm3/(t·h),temperature of 540℃,pressure of 1.8 MPa,catalyst loading of 0.9%(ω),and molar ratio of H2 to Si Cl4 1.7:1.Based on the experemental results,a reaction mechanism was proposed,which involved the continuous consumption of silicon(many apertures was showed on SEM image)and formation of new Cu3Si active component during the hydrogenation reaction.
文摘Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of different factors on the epoxidation of three unsaturated natural products were investigated by orthogonal design.Results The experimental results show that three unsaturated natural products are oxidized to the corresponding epoxides with hydrogen peroxide in the presence of 10%(mol/mol) of iodine at room temperature in high yields.Conclusion Iodine was found to be an efficient catalyst for the epoxidation of carbon-carbon double bonds in some unsaturated natural products with hydrogen peroxide at room temperature.
文摘Abstract :The principle of processing popped ricecake, especially bymicrowave, was expounded. Then the relations between popping time,materials ratio, H20 content of biscuit-base and the crisp degree and poppingdegree of ricecake were discussed. The microwave popping and oil-fry poppingwere compared as well.
