The phase and valency state of cobalt species on Co/HZSM 5 catalysts containing 1 0% to 10 0% cobalt were characterized by XRD, TPR and DRS technique. It was found that cobalt species on Co/HZSM 5 may exist in the pha...The phase and valency state of cobalt species on Co/HZSM 5 catalysts containing 1 0% to 10 0% cobalt were characterized by XRD, TPR and DRS technique. It was found that cobalt species on Co/HZSM 5 may exist in the phases of Co 3O 4, CoO, CoAl 2O 4 spinel, exchanged Co or metal Co at different calcination and reduction temperature, and CoAl 2O 4 spinel is difficult to be reduced.展开更多
The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution ...The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution of aromatics were investigated. The experimental results showed that the addition of Fe, Cr, Co and Ga promoted the dehydrogenation and dissociation of methane. The results of NH3-TPD indicated that the acidity of HZSM-5 was changed by adding Fe and Co components, consequently the catalytic properties of Mo/HZSM-5 were changed. It was also revealed that strong acid sites were the center of methane aromatization. The results of XRD characterization showed that the crystallinity of Mo on ZSM-5 zeolite was increased after adding Fe, Co additives.展开更多
The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of ...The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g·h). A high benzene yield was obtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value. TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant. It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.展开更多
文摘The phase and valency state of cobalt species on Co/HZSM 5 catalysts containing 1 0% to 10 0% cobalt were characterized by XRD, TPR and DRS technique. It was found that cobalt species on Co/HZSM 5 may exist in the phases of Co 3O 4, CoO, CoAl 2O 4 spinel, exchanged Co or metal Co at different calcination and reduction temperature, and CoAl 2O 4 spinel is difficult to be reduced.
文摘The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution of aromatics were investigated. The experimental results showed that the addition of Fe, Cr, Co and Ga promoted the dehydrogenation and dissociation of methane. The results of NH3-TPD indicated that the acidity of HZSM-5 was changed by adding Fe and Co components, consequently the catalytic properties of Mo/HZSM-5 were changed. It was also revealed that strong acid sites were the center of methane aromatization. The results of XRD characterization showed that the crystallinity of Mo on ZSM-5 zeolite was increased after adding Fe, Co additives.
基金Financial supports from the Ministry of Science and Technology of Chinathe Natural Science Foundation of China+1 种基金the Chinese Academy of Sciencethe BP-China Joint Research Center are gratefully acknowledged.
文摘The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g·h). A high benzene yield was obtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value. TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant. It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.
