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
The surface species formed in the reaction of NO and NO2 with pre-adsorbed NH 3 over a Fe-ZSM-5 catalyst(1.27 wt.%Fe,SiO2/Al2O3=25)at low temperature(140°C)were studied by in situ diffuse reflectance infrared Fou...The surface species formed in the reaction of NO and NO2 with pre-adsorbed NH 3 over a Fe-ZSM-5 catalyst(1.27 wt.%Fe,SiO2/Al2O3=25)at low temperature(140°C)were studied by in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Through using a background spectrum of NH3-saturated Fe-ZSM-5,we clearly observed the formation of common intermediates resulting from the reaction of NO2 or NO+O2 with pre-adsorbed NH3.This presents strong evidence that the oxidation of NO to form surface nitrates and nitrites is the key step for standard SCR at low temperature.In addition,the results suggest that in the SCR reaction at low temperature,the NH^4+ions absorbed on Brønsted acid sites are less active than NH3 adsorbed on Lewis acid sites related to Fe species.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This work was financially supported by the National Natural Science Foundation of China(Nos.21777174 and 21637005).
文摘The surface species formed in the reaction of NO and NO2 with pre-adsorbed NH 3 over a Fe-ZSM-5 catalyst(1.27 wt.%Fe,SiO2/Al2O3=25)at low temperature(140°C)were studied by in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Through using a background spectrum of NH3-saturated Fe-ZSM-5,we clearly observed the formation of common intermediates resulting from the reaction of NO2 or NO+O2 with pre-adsorbed NH3.This presents strong evidence that the oxidation of NO to form surface nitrates and nitrites is the key step for standard SCR at low temperature.In addition,the results suggest that in the SCR reaction at low temperature,the NH^4+ions absorbed on Brønsted acid sites are less active than NH3 adsorbed on Lewis acid sites related to Fe species.
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 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)~~
