The Mo/HZSM-5 catalyzed,non-oxidative methane dehydroaromatization reaction provides a promising direct approach for production of benzene as well as naphthalene from CH4 resources and therefore its early industrial a...The Mo/HZSM-5 catalyzed,non-oxidative methane dehydroaromatization reaction provides a promising direct approach for production of benzene as well as naphthalene from CH4 resources and therefore its early industrial application is highly desired.A simplified methane dehydroaromatization process that consists of only one reactor unit and two product separation units is presented,and the factors that could significantly affect the process efficiency are quantitatively analyzed.While efficiently separating and recycling up to 70vol%unreacted CH4 from the stream out of condensable aromatics separation unit might become the main problem in maximizing the process efficiency,increasing the operating temperature as high as possible of the CH4 converter in the reactor unit and raising the system operation pressure to a level somewhat higher than one atmosphere should help maximize the process performance.At process-required high reaction temperatures,however,Mo/HZSM-5 catalyst suffers from vary rapid deactivation due to serious coke formation.Therefore,it becomes necessary to employ a reactor system that enables continuous and simultaneous regeneration of deactivated catalyst so as to maintain the catalytic activity and stability of catalyst over a sufficiently long operation period.Nineteen years of sustained R&D efforts of the author’s team have led to a few applicable technologies related to preparation of a fluidizable binder-free Mo/HZSM-5 catalyst for use in fluidized bed reactors,regeneration of deactivated Mo/HZSM-5 catalyst using H_(2),and design and operation of a dual-bed circulating fluidized bed reactor system for continuous processing of the Mo/HZSM-5 catalyzed methane dehydroaromatization reaction.Operated at 1073 K and under a continuous regeneration mode,an in-house developed binder-free 6%Mo/HZSM-5 catalyst has proven to be capable of providing a stable benzene yield of approximately 13%over a cumulative period of 1800 min.Nevertheless,minimizing the catalyst deactivation by coking and developing a hig展开更多
采用四丙基氢氧化铵(TPAOH)处理HZSM-5分子筛,并负载金属Mo.利用XRD、低温氮气吸附、27Al MAS NMR、29Si MAS NMR和NH3-TPD等表征技术对TPAOH改性前后催化剂的结构和酸性进行了研究,考察了其对甲烷甲醇共芳构化反应的催化性能.结构表征...采用四丙基氢氧化铵(TPAOH)处理HZSM-5分子筛,并负载金属Mo.利用XRD、低温氮气吸附、27Al MAS NMR、29Si MAS NMR和NH3-TPD等表征技术对TPAOH改性前后催化剂的结构和酸性进行了研究,考察了其对甲烷甲醇共芳构化反应的催化性能.结构表征结果表明,适量的TPAOH改性可提高HZSM-5分子筛的相对结晶度,样品中介孔含量明显增加并且弱酸量和强酸量也有所增加.反应性能测试表明,以6%Mo负载的HZSM-5(6Mo/HZSM-5)为催化剂,在700℃、甲烷体积空速为2000 h-1的反应条件下,甲烷中添加少量甲醇(nCH4/nCH3OH=20)时,甲烷转化率稳定在10%左右,苯选择性在70%以上,C7-C9高碳芳烃的选择性为4%.在0.1mol/L TPAOH改性6Mo/HZSM-5催化剂上,甲烷转化率为8%左右,苯选择性稳定在60%以上,C7-C9高碳芳烃的选择性提升到10%~17%.利用TG和TPO技术对反应后样品的积碳情况进行了表征,发现甲烷甲醇共进料时催化剂积碳量由甲烷单独进料时的15%降低至5%,0.1mol/L的TPAOH改性后积碳量则进一步降低至1.4%.TPAOH改性的催化剂上介孔含量的增加和强酸中心上的稠环芳烃含量的减少是反应后积碳量显著下降的主要原因,这有利于提高芳构化催化剂的稳定性和碳原子的有效利用率.展开更多
As a potential methane efficient conversion process,non-oxidative aromatization of methane in fluidized bed requires a catalyst with good attrition resistance,especially in the states of high temperature,longtime rapi...As a potential methane efficient conversion process,non-oxidative aromatization of methane in fluidized bed requires a catalyst with good attrition resistance,especially in the states of high temperature,longtime rapid movement and chemical reaction.Existing evaluation methods for attrition resistance,such as ASTM D5757 and Jet Cup test,are targeted for fresh catalysts at ambient temperature,which cannot well reflect the real process.In this study,spherical-shaped Mo/HZSM-5 catalyst prepared by dipping and spray drying was placed in a self-made apparatus for attrition testing,in which the catalyst attrition under different system temperatures,running time and process factors was investigated with percent mass loss(PML),particle size-mass distribution(PSMD)and scanning electron microscope(SEM).Carbon deposition on the catalyst before and after activation,aromatization and regeneration was analyzed by thermogravimetry(TG),and the attrited catalysts were evaluated for methane dehydro-aromatization(MDA).The results show that the surface abrasion and body breakage of catalyst particles occur continuously,with the increase of system temperature and running time,and make the PML rise gradually.The process factors of activation,aromatization and regeneration can cause the catalyst attrition and carbon deposits,which broaden the PSMD in varying degrees,and the carbon-substances on catalysts greatly improve their attrition resistance at high temperature.Catalyst attrition has a certain influence on its catalytic performance,and the main reasons point to particle breakage and fine powder escape.展开更多
The hydrogenation of carbon dioxide over Cu-Mo/HZSM-5 composite catalysts prepared by an impregnation method has been studied. The reduction property and adsorption ability of the catalyst towards hydrogen and carbon ...The hydrogenation of carbon dioxide over Cu-Mo/HZSM-5 composite catalysts prepared by an impregnation method has been studied. The reduction property and adsorption ability of the catalyst towards hydrogen and carbon dioxide have been investigated by TPR and TPD-MS techniques. The results indicated that the addition of Mo increased the activity and dimethyl ether selectivity of Cu/HZSM-5 catalyst, the most active and selective for dimethyl ether was the catalyst with n (Cu)/n (Mo) = 5:1. The addition of Mo caused the TPR peaks of Cu/HZSM-5 to move to higher temperatures. CO2-TPD results revealed the raise of the adsorbability of the catalyst toward CO2.展开更多
文摘The Mo/HZSM-5 catalyzed,non-oxidative methane dehydroaromatization reaction provides a promising direct approach for production of benzene as well as naphthalene from CH4 resources and therefore its early industrial application is highly desired.A simplified methane dehydroaromatization process that consists of only one reactor unit and two product separation units is presented,and the factors that could significantly affect the process efficiency are quantitatively analyzed.While efficiently separating and recycling up to 70vol%unreacted CH4 from the stream out of condensable aromatics separation unit might become the main problem in maximizing the process efficiency,increasing the operating temperature as high as possible of the CH4 converter in the reactor unit and raising the system operation pressure to a level somewhat higher than one atmosphere should help maximize the process performance.At process-required high reaction temperatures,however,Mo/HZSM-5 catalyst suffers from vary rapid deactivation due to serious coke formation.Therefore,it becomes necessary to employ a reactor system that enables continuous and simultaneous regeneration of deactivated catalyst so as to maintain the catalytic activity and stability of catalyst over a sufficiently long operation period.Nineteen years of sustained R&D efforts of the author’s team have led to a few applicable technologies related to preparation of a fluidizable binder-free Mo/HZSM-5 catalyst for use in fluidized bed reactors,regeneration of deactivated Mo/HZSM-5 catalyst using H_(2),and design and operation of a dual-bed circulating fluidized bed reactor system for continuous processing of the Mo/HZSM-5 catalyzed methane dehydroaromatization reaction.Operated at 1073 K and under a continuous regeneration mode,an in-house developed binder-free 6%Mo/HZSM-5 catalyst has proven to be capable of providing a stable benzene yield of approximately 13%over a cumulative period of 1800 min.Nevertheless,minimizing the catalyst deactivation by coking and developing a hig
文摘采用四丙基氢氧化铵(TPAOH)处理HZSM-5分子筛,并负载金属Mo.利用XRD、低温氮气吸附、27Al MAS NMR、29Si MAS NMR和NH3-TPD等表征技术对TPAOH改性前后催化剂的结构和酸性进行了研究,考察了其对甲烷甲醇共芳构化反应的催化性能.结构表征结果表明,适量的TPAOH改性可提高HZSM-5分子筛的相对结晶度,样品中介孔含量明显增加并且弱酸量和强酸量也有所增加.反应性能测试表明,以6%Mo负载的HZSM-5(6Mo/HZSM-5)为催化剂,在700℃、甲烷体积空速为2000 h-1的反应条件下,甲烷中添加少量甲醇(nCH4/nCH3OH=20)时,甲烷转化率稳定在10%左右,苯选择性在70%以上,C7-C9高碳芳烃的选择性为4%.在0.1mol/L TPAOH改性6Mo/HZSM-5催化剂上,甲烷转化率为8%左右,苯选择性稳定在60%以上,C7-C9高碳芳烃的选择性提升到10%~17%.利用TG和TPO技术对反应后样品的积碳情况进行了表征,发现甲烷甲醇共进料时催化剂积碳量由甲烷单独进料时的15%降低至5%,0.1mol/L的TPAOH改性后积碳量则进一步降低至1.4%.TPAOH改性的催化剂上介孔含量的增加和强酸中心上的稠环芳烃含量的减少是反应后积碳量显著下降的主要原因,这有利于提高芳构化催化剂的稳定性和碳原子的有效利用率.
基金supported by Hydrocarbon High-efficiency Utilization Technology Research Center of Shaanxi Yanchang Petroleum(Group)Co.,Ltd.,China(Contract No.HCRC-C13-010)the National Natural Science Foundation of China(No.21536009)。
文摘As a potential methane efficient conversion process,non-oxidative aromatization of methane in fluidized bed requires a catalyst with good attrition resistance,especially in the states of high temperature,longtime rapid movement and chemical reaction.Existing evaluation methods for attrition resistance,such as ASTM D5757 and Jet Cup test,are targeted for fresh catalysts at ambient temperature,which cannot well reflect the real process.In this study,spherical-shaped Mo/HZSM-5 catalyst prepared by dipping and spray drying was placed in a self-made apparatus for attrition testing,in which the catalyst attrition under different system temperatures,running time and process factors was investigated with percent mass loss(PML),particle size-mass distribution(PSMD)and scanning electron microscope(SEM).Carbon deposition on the catalyst before and after activation,aromatization and regeneration was analyzed by thermogravimetry(TG),and the attrited catalysts were evaluated for methane dehydro-aromatization(MDA).The results show that the surface abrasion and body breakage of catalyst particles occur continuously,with the increase of system temperature and running time,and make the PML rise gradually.The process factors of activation,aromatization and regeneration can cause the catalyst attrition and carbon deposits,which broaden the PSMD in varying degrees,and the carbon-substances on catalysts greatly improve their attrition resistance at high temperature.Catalyst attrition has a certain influence on its catalytic performance,and the main reasons point to particle breakage and fine powder escape.
文摘The hydrogenation of carbon dioxide over Cu-Mo/HZSM-5 composite catalysts prepared by an impregnation method has been studied. The reduction property and adsorption ability of the catalyst towards hydrogen and carbon dioxide have been investigated by TPR and TPD-MS techniques. The results indicated that the addition of Mo increased the activity and dimethyl ether selectivity of Cu/HZSM-5 catalyst, the most active and selective for dimethyl ether was the catalyst with n (Cu)/n (Mo) = 5:1. The addition of Mo caused the TPR peaks of Cu/HZSM-5 to move to higher temperatures. CO2-TPD results revealed the raise of the adsorbability of the catalyst toward CO2.
