Industrial propane dehydrogenation(PDH)catalysts generally suffer from low catalytic stability due to the coke formation onto the catalyst surface to cover the active sites.The exploitation of an efficient catalyst wi...Industrial propane dehydrogenation(PDH)catalysts generally suffer from low catalytic stability due to the coke formation onto the catalyst surface to cover the active sites.The exploitation of an efficient catalyst with both high catalytic selectivity and long-term stability toward PDH is of great importance but challenging to make.Herein CrOx supported on high-silica HZSM-5 with a SiO2/Al2O3 ratio of 260(Cr/Z-5(260)is synthesized by a simple wet impregnation method,which exhibits high catalytic activity,good selectivity and excellent stability for PDH.At a weight hourly space velocity(WHSV)of 0.59 h-1,a propylene formation rate of 4.1 mmol g-1cath-1(~32.6% propane conversion and ~94.2% propylene selectivity)can be maintained over the 5%Cr/Z-5(260)catalyst after 50 h time on stream,which is much better than commercial Cr/Al2O3(Catofin process,catalyst life is several hours)at the same reaction conditions.With increasing the WHSV to 5.9 h-1,a high propylene formation rate of 27.9 mmol gcat-1h-1can be obtained over the 5%Cr/Z-5(260)catalyst after 50 h time on stream,demonstrating a very promising PDH catalyst.Characterization results and Na+doping experiments reveal that the Cr species combined with Br?nsted acid sites in Cr/HZSM-5 catalysts are responsible for the high catalytic performance.In particular,the Br?nsted acid sites in HZSM-5 zeolite could increase the propane adsorption and enhance the C–H bond activation.Furthermore,the high surface area and well-defined pores of HZSM-5 zeolite can provide a special environment for the dispersion and stabilization of Cr species,thus guaranteeing high catalytic activity and stability.展开更多
Improving the aromatic selectivity in the alkane aromatization process is of great importance for its practical utilization but challenge to make because the high H/C ratio of alkanes would lead to a serious hydrogen ...Improving the aromatic selectivity in the alkane aromatization process is of great importance for its practical utilization but challenge to make because the high H/C ratio of alkanes would lead to a serious hydrogen transfer process and a large amount of light alkanes.Herein,CO_(2)is introduced into the cyclohexane conversion process on the HZSM-5 zeolite,which can improve the aromatic selectivity.By optimizing the reaction conditions,an improved aromatic(benzene,toluene,xylene,and C9+)selectivity of 48.2%can be obtained at the conditions of 2.7 MPa(CO_(2)),450℃,and 1.7 h^(−1),which is better than that without CO_(2)(aromatic selectivity=43.2%).In situ transmission Fourier transform infrared spectroscopy spectra illustrate that many oxygenated chemical intermediates(e.g.,carboxylic acid,anhydride,unsaturated aldehydes/ketones or ketene)would be formed during the cyclohexane conversion process in the presence of CO_(2).13C isotope labeling experimental results demonstrate that CO_(2)can enter into the aromatics through the formation of oxygenated chemical intermediates and thereby improve the aromatic selectivity.This study may open a green,economic,and promising way to improve the aromatic selectivity for alkane aromatization process.展开更多
基金supported by the National Natural Science Foundation of China(21421001,21573115)the Fundamental Research Funds for the Central Universities(63185015)the Foundation of State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering(2017-K13)~~
基金supported by the National Natural Science Foundation of China(21421001,21573115)the Fundamental Research Funds for the Central Universities(63185015)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(2017-K13)~~
基金supported by the National Natural Science Foundation of China (21421001, 21573115)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering (2017-K13)。
文摘Industrial propane dehydrogenation(PDH)catalysts generally suffer from low catalytic stability due to the coke formation onto the catalyst surface to cover the active sites.The exploitation of an efficient catalyst with both high catalytic selectivity and long-term stability toward PDH is of great importance but challenging to make.Herein CrOx supported on high-silica HZSM-5 with a SiO2/Al2O3 ratio of 260(Cr/Z-5(260)is synthesized by a simple wet impregnation method,which exhibits high catalytic activity,good selectivity and excellent stability for PDH.At a weight hourly space velocity(WHSV)of 0.59 h-1,a propylene formation rate of 4.1 mmol g-1cath-1(~32.6% propane conversion and ~94.2% propylene selectivity)can be maintained over the 5%Cr/Z-5(260)catalyst after 50 h time on stream,which is much better than commercial Cr/Al2O3(Catofin process,catalyst life is several hours)at the same reaction conditions.With increasing the WHSV to 5.9 h-1,a high propylene formation rate of 27.9 mmol gcat-1h-1can be obtained over the 5%Cr/Z-5(260)catalyst after 50 h time on stream,demonstrating a very promising PDH catalyst.Characterization results and Na+doping experiments reveal that the Cr species combined with Br?nsted acid sites in Cr/HZSM-5 catalysts are responsible for the high catalytic performance.In particular,the Br?nsted acid sites in HZSM-5 zeolite could increase the propane adsorption and enhance the C–H bond activation.Furthermore,the high surface area and well-defined pores of HZSM-5 zeolite can provide a special environment for the dispersion and stabilization of Cr species,thus guaranteeing high catalytic activity and stability.
基金the National Key Research and Development Program of China(Grant No.2022YFE0116000)the National Natural Science Foundation of China(Grant Nos.22202193,21991092,21991090,22172166 and 22288101)+2 种基金the China Postdoctoral Science Foundation(Grant No.2019M661147)the Excellent Postdoctoral Support Program of Dalian Institute of Chemical Physics,CAS,the Excellent Research Assistant Funding Project of CAS,the Youth Innovation Promotion Association CAS(Grant No.2021182)the Innovation Research Foundation of Dalian Institute of Chemical Physics,Chinese Academy of Sciences(Grant No.DICP I202217)。
文摘Improving the aromatic selectivity in the alkane aromatization process is of great importance for its practical utilization but challenge to make because the high H/C ratio of alkanes would lead to a serious hydrogen transfer process and a large amount of light alkanes.Herein,CO_(2)is introduced into the cyclohexane conversion process on the HZSM-5 zeolite,which can improve the aromatic selectivity.By optimizing the reaction conditions,an improved aromatic(benzene,toluene,xylene,and C9+)selectivity of 48.2%can be obtained at the conditions of 2.7 MPa(CO_(2)),450℃,and 1.7 h^(−1),which is better than that without CO_(2)(aromatic selectivity=43.2%).In situ transmission Fourier transform infrared spectroscopy spectra illustrate that many oxygenated chemical intermediates(e.g.,carboxylic acid,anhydride,unsaturated aldehydes/ketones or ketene)would be formed during the cyclohexane conversion process in the presence of CO_(2).13C isotope labeling experimental results demonstrate that CO_(2)can enter into the aromatics through the formation of oxygenated chemical intermediates and thereby improve the aromatic selectivity.This study may open a green,economic,and promising way to improve the aromatic selectivity for alkane aromatization process.
