In this study,NiO/SBA-15 was prepared by both direct and post synthesis methods.TEM images revealed that NiO particles aggregated in NiO/SBA-15 obtained with post synthesis method,regardless of NiO loading.However,NiO...In this study,NiO/SBA-15 was prepared by both direct and post synthesis methods.TEM images revealed that NiO particles aggregated in NiO/SBA-15 obtained with post synthesis method,regardless of NiO loading.However,NiO particles were monodispersed in NiO/SBA-15 with a NiO loading of less than 15 wt%by using the direct synthesis method.In this case,NiO particles aggregated when NiO loading was over 20 wt%.TPR analysis verified that with direct synthesis method the location boundary of NiO particles on outer and pore surface could be observed clearly,whereas that could not observed in the case of post synthesis method.This indicates that the type of synthesis method displays significant effect on the location of NiO particles dispersed into the SBA-15.Producer gas conversion was carried out using NiO/SBA-15 as catalysts,which were synthesized with different synthesis methods.The gas conversion including methanation occurred at low temperature(i.e.,300-400℃)and the reverse water gas shift(RWGS)reaction at hightemperature(i.e.,400-900℃).High temperatures facilitated CO conversion to CO with CO selectivity close to 100%,regardless of the synthesis method of the used catalyst.At low temperatures the dispersion type of NiO particles affectedthe CO,conversion reaction,i.e.,monodispersed Ni0 particles gave a CO selectivity of close to 100%,similar to thatobtained at high temperature.The aggregated NiO particles resuled in a CO selectivity of less than 100%owing to CH,formation,regardless of synthesis method of catalyst.Therefore,NiO/SBA-15 obtained with direct synthesis methodfavored RWGS reaction because of high CO selectivity.NiOSBA-15 obtained with post synthesis method is suited formethanation because of high CH selectivity,and the conversion of CO,to CHa through methanation increased withincreasing NiO loading.展开更多
This study aims to compare the catalytic performance of ZSM-5 and SAPO-34 zeolite catalysts in the conversion of ethanol.Through experiments conducted at different temperatures(773 and 673 K),it was found that SAPO-34...This study aims to compare the catalytic performance of ZSM-5 and SAPO-34 zeolite catalysts in the conversion of ethanol.Through experiments conducted at different temperatures(773 and 673 K),it was found that SAPO-34 initially exhibits superior propylene selectivity compared to ZSM-5.However,the propylene yield on SAPO-34 gradually decreases,while the ethylene yield increases with time on stream.Density functional theory calculations were employed for the investigation of the reaction mechanism.The results indicate that the SAPO-34 catalyst surface favors propylene desorption,which is beneficial for its initial high propylene selectivity.Nevertheless,the smaller pore structure of SAPO-34 limits the effective diffusion of products,leading to product accumulation within the pores and potentially causing catalyst coking and deactivation.By combining the experimental results with theoretical calculations,this study not only explored the selectivity difference between SAPO-34 and H-ZSM-5 in ethanol conversion reaction but also revealed the influence of different molecular sieve catalyst structures on product distribution and catalyst stability.展开更多
文摘In this study,NiO/SBA-15 was prepared by both direct and post synthesis methods.TEM images revealed that NiO particles aggregated in NiO/SBA-15 obtained with post synthesis method,regardless of NiO loading.However,NiO particles were monodispersed in NiO/SBA-15 with a NiO loading of less than 15 wt%by using the direct synthesis method.In this case,NiO particles aggregated when NiO loading was over 20 wt%.TPR analysis verified that with direct synthesis method the location boundary of NiO particles on outer and pore surface could be observed clearly,whereas that could not observed in the case of post synthesis method.This indicates that the type of synthesis method displays significant effect on the location of NiO particles dispersed into the SBA-15.Producer gas conversion was carried out using NiO/SBA-15 as catalysts,which were synthesized with different synthesis methods.The gas conversion including methanation occurred at low temperature(i.e.,300-400℃)and the reverse water gas shift(RWGS)reaction at hightemperature(i.e.,400-900℃).High temperatures facilitated CO conversion to CO with CO selectivity close to 100%,regardless of the synthesis method of the used catalyst.At low temperatures the dispersion type of NiO particles affectedthe CO,conversion reaction,i.e.,monodispersed Ni0 particles gave a CO selectivity of close to 100%,similar to thatobtained at high temperature.The aggregated NiO particles resuled in a CO selectivity of less than 100%owing to CH,formation,regardless of synthesis method of catalyst.Therefore,NiO/SBA-15 obtained with direct synthesis methodfavored RWGS reaction because of high CO selectivity.NiOSBA-15 obtained with post synthesis method is suited formethanation because of high CH selectivity,and the conversion of CO,to CHa through methanation increased withincreasing NiO loading.
基金sponsored by the National Natural Science Foundation of China(Grant 21978327).
文摘This study aims to compare the catalytic performance of ZSM-5 and SAPO-34 zeolite catalysts in the conversion of ethanol.Through experiments conducted at different temperatures(773 and 673 K),it was found that SAPO-34 initially exhibits superior propylene selectivity compared to ZSM-5.However,the propylene yield on SAPO-34 gradually decreases,while the ethylene yield increases with time on stream.Density functional theory calculations were employed for the investigation of the reaction mechanism.The results indicate that the SAPO-34 catalyst surface favors propylene desorption,which is beneficial for its initial high propylene selectivity.Nevertheless,the smaller pore structure of SAPO-34 limits the effective diffusion of products,leading to product accumulation within the pores and potentially causing catalyst coking and deactivation.By combining the experimental results with theoretical calculations,this study not only explored the selectivity difference between SAPO-34 and H-ZSM-5 in ethanol conversion reaction but also revealed the influence of different molecular sieve catalyst structures on product distribution and catalyst stability.
