H‐ZSM‐5 zeolite is a typical catalyst for methanol‐to‐olefins(MTO)conversion.Although the performance of zeolite catalysts for MTO conversion is related to the actual location of acid sites in the zeolite framewor...H‐ZSM‐5 zeolite is a typical catalyst for methanol‐to‐olefins(MTO)conversion.Although the performance of zeolite catalysts for MTO conversion is related to the actual location of acid sites in the zeolite framework,the catalytic roles of the acid sites in different pore channels of the H‐ZSM‐5 zeolite are not well understood.In this study,the MTO reaction network,involving the aromatic cycle,alkene cycle,and aromatization process,and also the diffusion behavior of methanol feedstock and olefin and aromatic products at different acid sites in the straight channel,sinusoidal channel,and intersection cavity of H‐ZSM‐5 zeolite was comparatively investigated using density functional theory calculations and molecular dynamic simulations.The results indicated that the aromatic cycle and aromatization process occurred preferentially at the acid sites in the intersection cavities with a much lower energy barrier than that at the acid sites in the straight and sinusoidal channels.In contrast,the formation of polymethylbenzenes was significantly suppressed at the acid sites in the sinusoidal and straight channels,whereas the alkene cycle can occur at all three types of acid sites with similar energy barriers and probabilities.Consequently,the catalytic performance of H‐ZSM‐5 zeolite for MTO conversion,including activity and product selectivity,can be regulated properly through the purposive alteration of the acid site distribution,viz.,the location of Al in the zeolite framework.This study helps to elucidate the relation between the catalytic performance of different acid sites in the H‐ZSM‐5 zeolite framework for MTO conversion,which should greatly benefit the design of efficient catalyst for methanol conversion.展开更多
Objective:To systematically review the clinical practice guidelines(CPGs)for the treatment of patients with coronavirus disease 2019(COVID-19)using Chinese herbal medicine(CHM),assess the methodological quality as wel...Objective:To systematically review the clinical practice guidelines(CPGs)for the treatment of patients with coronavirus disease 2019(COVID-19)using Chinese herbal medicine(CHM),assess the methodological quality as well as clinical credibility and implementability of specific recommendations,and summarize key recommendations.Methods:As of April 2022,we conducted a comprehensive search on major electronic databases,guideline websites,academic society websites,and government websites to assess the methodological quality and clinical applicability of the included CPGs using the Appraisal of Guidelines for Research and Evaluation(AGREE)II tool and Evaluation-Recommendations EXcellence(AGREE-REX)instructions,respectively.Results:The search yielded 61 CPGs,which were mostly published in 2020;moreover,98.4%of the CPGs were published in China.Only five CPGs achieved a high-quality AGREE II rating;further,six CPGs could be directly recommended,with most of the CPGs still showing much room for improvement.CPGs had a low overall score in the AGREE-REX evaluation,with the domains of clinical applicability,values and preferences,and implementability being standardized in 21.80%±12.56%,16.00%±11.81%,and 31.33%±14.55%of the CPGs,respectively.Five high-quality CPGs mentioned 56 Chinese herbal formulas.Half of the recommendations had moderate or strong evidence level in the GRADE evaluation.The most frequently recommended herbal medicines were Lianhua Qingwen granule/capsule and Jinhua Qinggan granule;however,the strength of recommendation for each prescription varied across CPGs and populations.Conclusions:The overall quality of current CPGs for COVID-19 for CHM still needs to be improved;moreover,the strength of the evidence remains to be standardized across CPGs.展开更多
文摘H‐ZSM‐5 zeolite is a typical catalyst for methanol‐to‐olefins(MTO)conversion.Although the performance of zeolite catalysts for MTO conversion is related to the actual location of acid sites in the zeolite framework,the catalytic roles of the acid sites in different pore channels of the H‐ZSM‐5 zeolite are not well understood.In this study,the MTO reaction network,involving the aromatic cycle,alkene cycle,and aromatization process,and also the diffusion behavior of methanol feedstock and olefin and aromatic products at different acid sites in the straight channel,sinusoidal channel,and intersection cavity of H‐ZSM‐5 zeolite was comparatively investigated using density functional theory calculations and molecular dynamic simulations.The results indicated that the aromatic cycle and aromatization process occurred preferentially at the acid sites in the intersection cavities with a much lower energy barrier than that at the acid sites in the straight and sinusoidal channels.In contrast,the formation of polymethylbenzenes was significantly suppressed at the acid sites in the sinusoidal and straight channels,whereas the alkene cycle can occur at all three types of acid sites with similar energy barriers and probabilities.Consequently,the catalytic performance of H‐ZSM‐5 zeolite for MTO conversion,including activity and product selectivity,can be regulated properly through the purposive alteration of the acid site distribution,viz.,the location of Al in the zeolite framework.This study helps to elucidate the relation between the catalytic performance of different acid sites in the H‐ZSM‐5 zeolite framework for MTO conversion,which should greatly benefit the design of efficient catalyst for methanol conversion.
文摘Objective:To systematically review the clinical practice guidelines(CPGs)for the treatment of patients with coronavirus disease 2019(COVID-19)using Chinese herbal medicine(CHM),assess the methodological quality as well as clinical credibility and implementability of specific recommendations,and summarize key recommendations.Methods:As of April 2022,we conducted a comprehensive search on major electronic databases,guideline websites,academic society websites,and government websites to assess the methodological quality and clinical applicability of the included CPGs using the Appraisal of Guidelines for Research and Evaluation(AGREE)II tool and Evaluation-Recommendations EXcellence(AGREE-REX)instructions,respectively.Results:The search yielded 61 CPGs,which were mostly published in 2020;moreover,98.4%of the CPGs were published in China.Only five CPGs achieved a high-quality AGREE II rating;further,six CPGs could be directly recommended,with most of the CPGs still showing much room for improvement.CPGs had a low overall score in the AGREE-REX evaluation,with the domains of clinical applicability,values and preferences,and implementability being standardized in 21.80%±12.56%,16.00%±11.81%,and 31.33%±14.55%of the CPGs,respectively.Five high-quality CPGs mentioned 56 Chinese herbal formulas.Half of the recommendations had moderate or strong evidence level in the GRADE evaluation.The most frequently recommended herbal medicines were Lianhua Qingwen granule/capsule and Jinhua Qinggan granule;however,the strength of recommendation for each prescription varied across CPGs and populations.Conclusions:The overall quality of current CPGs for COVID-19 for CHM still needs to be improved;moreover,the strength of the evidence remains to be standardized across CPGs.
