Catalytic oxidation of benzene with N_(2)O to phenol over the hierarchical and microporous Fe/ZSM-5-based catalysts in a continuous fixedbed reactor was investigated.The spent catalyst was in-situ regenerated by an ox...Catalytic oxidation of benzene with N_(2)O to phenol over the hierarchical and microporous Fe/ZSM-5-based catalysts in a continuous fixedbed reactor was investigated.The spent catalyst was in-situ regenerated by an oxidative treatment using N_(2)O and in total 10 reaction-regeneration cycles were performed.A 100% N_(2)O conversion,93.3% phenol selectivity,and high initial phenol formation rate of 16.49±0.06mmol_(phenol gcatalyst)^(-1)h^(-1)at time on stream(TOS) of 5 min,and a good phenol productivity of 147.06 mmol_(phenol gcatalyst)^(-1)during catalyst lifetime of 1800 min were obtained on a fresh hierarchical Fe/ZSM-5-Hi2.8 catalyst.With the reaction-regeneration cycle,N_(2)O conversion is fully recovered within TOS of 3 h,moreover,the phenol productivity was decreased ca.2.2±0.8% after each cycle,leading to a total phenol productivity of ca.0.44 ton_(pheol kg_(catalyst)^(-1)estimated for 300 cycles.Catalyst characterizations imply that the coke is rapidly deposited on catalyst surface in the initial TOS of 3 h(0.28 mgc_(gcatalyst)^(-1)min^(-1)) and gradually becomes graphitic during the TOS of 30 h with a slow formation rate of 0.06 mgc g_(catalyst)^(-1)min^(-1).Among others(e.g.,the decrease of textural property and acidity),the nearly complete coverage of the active Fe-O-Al sites by coke accounts for the main catalyst deactivation.Besides these reversible deactivation characteristics related to coking,the irreversible catalyst deactivation is also observed with the reaction-regeneration cycle.The latter is reflected by a further decreased amount of the active Fe-O-Al sites,which agglomerate on catalyst surface with the cycle,likely associated with the hard coke residue that is not completely removed by the regeneration.展开更多
Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determin...Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determined as the active iron complex for N2O decomposition to produce the active oxygen. Reduction of Fe3+ to Fe2+ by H2 in the dimer and removal of OH- groups from Fe2+ dimer by heating Fe/ZSM-5 to 700 ℃ were the prerequisites for the formation of this active Fe complex. A linear correlation with a slope of 1.0 between the amount of Fe-O-Fe2+ and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe/ZSM-5 catalyst with H2 at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N2O exposure at 250 ℃.The ratio of the total number of oxygen atoms (Ode) deposited by interaction of Fe-O-Fe2+ with N2O to the amount of Fe-O-Fe2+ was 2. However, not all the deposited oxygen atoms were active oxygen (Oa); the ratio of Oa and Ode was 0.5. The iron dimer complex composing active oxygen is a five-atom ion Fe2O32+; the most probable structure is as follows:展开更多
The catalytic activity of Fe/ZSM-5 for the selective reduction of NO to N_2 with methane in the presence of excess O_2 was studied.Fe/ZSM-5 catalysts with various Fe loadings were prepared by impregnation method.It is...The catalytic activity of Fe/ZSM-5 for the selective reduction of NO to N_2 with methane in the presence of excess O_2 was studied.Fe/ZSM-5 catalysts with various Fe loadings were prepared by impregnation method.It is well known that methane is inactive when Fe/ZSM-5 as the catalyst for the selective catalytic reduction(SCR) of NO with methane.However,this paper shows that when the content of Fe was about 0.5%,Fe/ZSM-5 showed higher catalytic activity and selectivity of methane,and put forward measurable activation for CH_4 is an important factor for the reaction of removal of NOx with CH_4.展开更多
基金Financial support by the Specialized Research Fund for Doctoral Program of Higher Education,China (No.20120010110003)。
文摘Catalytic oxidation of benzene with N_(2)O to phenol over the hierarchical and microporous Fe/ZSM-5-based catalysts in a continuous fixedbed reactor was investigated.The spent catalyst was in-situ regenerated by an oxidative treatment using N_(2)O and in total 10 reaction-regeneration cycles were performed.A 100% N_(2)O conversion,93.3% phenol selectivity,and high initial phenol formation rate of 16.49±0.06mmol_(phenol gcatalyst)^(-1)h^(-1)at time on stream(TOS) of 5 min,and a good phenol productivity of 147.06 mmol_(phenol gcatalyst)^(-1)during catalyst lifetime of 1800 min were obtained on a fresh hierarchical Fe/ZSM-5-Hi2.8 catalyst.With the reaction-regeneration cycle,N_(2)O conversion is fully recovered within TOS of 3 h,moreover,the phenol productivity was decreased ca.2.2±0.8% after each cycle,leading to a total phenol productivity of ca.0.44 ton_(pheol kg_(catalyst)^(-1)estimated for 300 cycles.Catalyst characterizations imply that the coke is rapidly deposited on catalyst surface in the initial TOS of 3 h(0.28 mgc_(gcatalyst)^(-1)min^(-1)) and gradually becomes graphitic during the TOS of 30 h with a slow formation rate of 0.06 mgc g_(catalyst)^(-1)min^(-1).Among others(e.g.,the decrease of textural property and acidity),the nearly complete coverage of the active Fe-O-Al sites by coke accounts for the main catalyst deactivation.Besides these reversible deactivation characteristics related to coking,the irreversible catalyst deactivation is also observed with the reaction-regeneration cycle.The latter is reflected by a further decreased amount of the active Fe-O-Al sites,which agglomerate on catalyst surface with the cycle,likely associated with the hard coke residue that is not completely removed by the regeneration.
基金supported by the National High Technology Research and Development Program of China(863 Program,2013AA065301)the National Basic Research Program of China(973 Program,2010CB732304)the National Natural Science Found for Creative Research Groups of China(51221892)~~
文摘Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determined as the active iron complex for N2O decomposition to produce the active oxygen. Reduction of Fe3+ to Fe2+ by H2 in the dimer and removal of OH- groups from Fe2+ dimer by heating Fe/ZSM-5 to 700 ℃ were the prerequisites for the formation of this active Fe complex. A linear correlation with a slope of 1.0 between the amount of Fe-O-Fe2+ and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe/ZSM-5 catalyst with H2 at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N2O exposure at 250 ℃.The ratio of the total number of oxygen atoms (Ode) deposited by interaction of Fe-O-Fe2+ with N2O to the amount of Fe-O-Fe2+ was 2. However, not all the deposited oxygen atoms were active oxygen (Oa); the ratio of Oa and Ode was 0.5. The iron dimer complex composing active oxygen is a five-atom ion Fe2O32+; the most probable structure is as follows:
文摘The catalytic activity of Fe/ZSM-5 for the selective reduction of NO to N_2 with methane in the presence of excess O_2 was studied.Fe/ZSM-5 catalysts with various Fe loadings were prepared by impregnation method.It is well known that methane is inactive when Fe/ZSM-5 as the catalyst for the selective catalytic reduction(SCR) of NO with methane.However,this paper shows that when the content of Fe was about 0.5%,Fe/ZSM-5 showed higher catalytic activity and selectivity of methane,and put forward measurable activation for CH_4 is an important factor for the reaction of removal of NOx with CH_4.
基金supported by the National Natural Science Foundation of China(No.21073131)Shanxi Provincial Science and Technology Projects(No.20140313002-2)+1 种基金State Key Laboratory Breeding Base of Coal Science and Technology Co-founded by Shanxi Province and the Ministry of Science and TechnologyTaiyuan University of Technology(No.MKX201301)~~
