用密度泛函理论和ONIOM(our own N-layer integrated molecular orbital molecular mechanics)方法研究磷改性的ZSM-5沸石中含磷基团的可能存在形态.计算的反应焓和自由能数据表明P-ZSM-5沸石中以磷进入骨架和在骨架外的形成磷酸根离子...用密度泛函理论和ONIOM(our own N-layer integrated molecular orbital molecular mechanics)方法研究磷改性的ZSM-5沸石中含磷基团的可能存在形态.计算的反应焓和自由能数据表明P-ZSM-5沸石中以磷进入骨架和在骨架外的形成磷酸根离子对是合理的稳定结构.而且,计算结果表明离子对模型F和G更适合在室温下存在,磷进入骨架的酸性结构C?在高温下更稳定,而磷进入骨架的结构C对温度变化不敏感.计算得到的27Al,31P,29Si化学位移、酸性的变化趋势和结构参数与相关实验数据吻合.展开更多
The most prestigious catalyst applied in natural gas （methane） non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5. Chromium, molybdenum and tungsten are the group VI metals. Hence, in this work, 6%Mo/H-ZSM-5...The most prestigious catalyst applied in natural gas （methane） non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5. Chromium, molybdenum and tungsten are the group VI metals. Hence, in this work, 6%Mo/H-ZSM-5 was correlated with 3%Cr＋3%Mo/H-ZSM-5 and 3%W＋3%Mo/H-ZSM-5 as catalysts to examine their promoting or inhibiting effects on the various reactions taking place during methane conversion. The catalytic activities of these catalysts were tested in a continuous flow fixed bed reactor at 700℃ and a GHSV of 1500 ml·g^-1·h^-1 Characterization of the catalysts using XRD, TGA and TPD were investigated. XRD and NH3-TPD showed greater interaction between the W-phase and the Bronsted acid sites in the channels of the zeolite than between Cr-phase and the acid sites in the zeolite.展开更多
Ni/γ-Al2O3 , Ni/Y-zeolite, and Ni/H-ZSM-5 catalysts were prepared using the incipient wetness impregnation method. Their catalytic performance in dry reforming of methane was studied. The fresh and used catalysts and...Ni/γ-Al2O3 , Ni/Y-zeolite, and Ni/H-ZSM-5 catalysts were prepared using the incipient wetness impregnation method. Their catalytic performance in dry reforming of methane was studied. The fresh and used catalysts and deposited carbon were characterized using H2 temperature-programmed reduction, temperature-programmed oxidation, N2 adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H-ZSM-5-supported Ni catalyst proved to be more stable than the other two catalysts, as it had the lowest carbon deposition.展开更多
Extended use of supported Pt catalysts causes thermal migration of Pt particles to form large agglomerates,thus decreasing the catalytic activity.The combination of Pt with Re protects Pt against migration.In addition...Extended use of supported Pt catalysts causes thermal migration of Pt particles to form large agglomerates,thus decreasing the catalytic activity.The combination of Pt with Re protects Pt against migration.In addition,Cl injection into the reactor assists Pt particles redispersion to prolong catalyst life.In this work,a PtRe/H-ZSM-5 catalyst was treated with either HCl or HF to investigate their role in activating or deactivating the catalyst.The conversion exceeded 90% in the whole temperature range with the PtRe/H-ZSM-5(HCl) catalyst,and its activity for the direct isomerization of cyclohexene to methylcyclopentenes(MCPEs) was the lowest but the activity for the hydrogenation of the MCPEs to methylcyclopentane was the highest.The reactivities of MCPEs and cyclohexadienes on the catalysts were similar because both are dehydrogenation reactions.Benzene production was significantly higher on the hydrochlorinated catalyst than on the other catalysts,and its hydrocracking activity was the lowest,which is a good characteristic for processing catalysts where cracking is undesired.展开更多
文摘用密度泛函理论和ONIOM(our own N-layer integrated molecular orbital molecular mechanics)方法研究磷改性的ZSM-5沸石中含磷基团的可能存在形态.计算的反应焓和自由能数据表明P-ZSM-5沸石中以磷进入骨架和在骨架外的形成磷酸根离子对是合理的稳定结构.而且,计算结果表明离子对模型F和G更适合在室温下存在,磷进入骨架的酸性结构C?在高温下更稳定,而磷进入骨架的结构C对温度变化不敏感.计算得到的27Al,31P,29Si化学位移、酸性的变化趋势和结构参数与相关实验数据吻合.
文摘The most prestigious catalyst applied in natural gas （methane） non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5. Chromium, molybdenum and tungsten are the group VI metals. Hence, in this work, 6%Mo/H-ZSM-5 was correlated with 3%Cr＋3%Mo/H-ZSM-5 and 3%W＋3%Mo/H-ZSM-5 as catalysts to examine their promoting or inhibiting effects on the various reactions taking place during methane conversion. The catalytic activities of these catalysts were tested in a continuous flow fixed bed reactor at 700℃ and a GHSV of 1500 ml·g^-1·h^-1 Characterization of the catalysts using XRD, TGA and TPD were investigated. XRD and NH3-TPD showed greater interaction between the W-phase and the Bronsted acid sites in the channels of the zeolite than between Cr-phase and the acid sites in the zeolite.
基金the Deanship of Scientific Research at KSU for funding the work through the research group Project#RGP‐VPP‐119
文摘Ni/γ-Al2O3 , Ni/Y-zeolite, and Ni/H-ZSM-5 catalysts were prepared using the incipient wetness impregnation method. Their catalytic performance in dry reforming of methane was studied. The fresh and used catalysts and deposited carbon were characterized using H2 temperature-programmed reduction, temperature-programmed oxidation, N2 adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H-ZSM-5-supported Ni catalyst proved to be more stable than the other two catalysts, as it had the lowest carbon deposition.
文摘Extended use of supported Pt catalysts causes thermal migration of Pt particles to form large agglomerates,thus decreasing the catalytic activity.The combination of Pt with Re protects Pt against migration.In addition,Cl injection into the reactor assists Pt particles redispersion to prolong catalyst life.In this work,a PtRe/H-ZSM-5 catalyst was treated with either HCl or HF to investigate their role in activating or deactivating the catalyst.The conversion exceeded 90% in the whole temperature range with the PtRe/H-ZSM-5(HCl) catalyst,and its activity for the direct isomerization of cyclohexene to methylcyclopentenes(MCPEs) was the lowest but the activity for the hydrogenation of the MCPEs to methylcyclopentane was the highest.The reactivities of MCPEs and cyclohexadienes on the catalysts were similar because both are dehydrogenation reactions.Benzene production was significantly higher on the hydrochlorinated catalyst than on the other catalysts,and its hydrocracking activity was the lowest,which is a good characteristic for processing catalysts where cracking is undesired.
