The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Junhua Li - One of the best experts on this subject based on the ideXlab platform.
-
Identification of the reaction pathway and reactive species for the selective catalytic reduction of NO with NH3 over cerium–niobium oxide catalysts
Catalysis Science & Technology, 2016Co-Authors: Ruiyang Qu, Yue Peng, Junhua LiAbstract:A series of Ce–Nb oxide catalysts were synthesized at different calcination temperatures for the selective catalytic reduction (SCR) of NO with NH3 and the reaction pathway and reactive species were investigated in detail. The SCR reaction pathway over the Ce–Nb catalysts followed both the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism, where the former contributed more especially at high reaction temperatures. Lewis acidity was found to be catalytically important in the Eley–Rideal Mechanism. NO2 and monodentate nitrate were the main reactive species in the Langmuir–Hinshelwood Mechanism. The catalyst calcined at lower temperatures exhibited higher catalytic activity at low temperatures but lower activity at high temperatures. With the increase in calcination temperature, the catalyst surface was gradually covered with niobium oxide species, resulting in the enhancement of total acidity but the decline of redox ability, along with the decrease in the contribution of the Langmuir–Hinshelwood Mechanism to the SCR reaction.
-
Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.
Environmental Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Xin Xiao, Feihong Qi, Yue Peng, Yuwu Fu, Wenpo Shan, Junhua LiAbstract:The Mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn–Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley–Rideal Mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir–Hinshelwood Mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism was much less than that through the Eley–Rideal Mechanism. The ratio of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn–Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn–Fe spinel increased because of the promo...
-
Competition of selective catalytic reduction and non selective catalytic reduction over MnOx/TiO2 for NO removal: the relationship between gaseous NO concentration and N2O selectivity
Catalysis Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Yuwu Fu, Zan Qu, Junhua LiAbstract:In this work, a novel phenomenon was discovered that N2O selectivity of NO reduction over MnOx/TiO2 was related to the concentration of gaseous NO and that lower concentration of gaseous NO would cause higher N2O selectivity. In situ DRIFTS and transient reaction studies demonstrated that both the Eley–Rideal Mechanism (the reaction of over-activated NH3 with gaseous NO) and the Langmuir–Hinshelwood Mechanism (the reaction of adsorbed NO3− with adsorbed NH3 on the adjacent sites) could contribute to the formation of N2O. Kinetic study demonstrated that N2O selectivity would be independent of gaseous NO concentration if NO reduction over MnOx/TiO2 mainly followed the Langmuir–Hinshelwood Mechanism. If NO reduction over MnOx/TiO2 mainly followed the Eley–Rideal Mechanism, there was competition between the selective catalytic reduction (SCR) reaction and non selective catalytic reduction (NSCR) reaction. As gaseous NO concentration increased, more –NH2 was used to reduce gaseous NO to form N2 and the further oxidization of –NH2 to –NH was restrained, resulting in an obvious decrease of N2O selectivity. The Eley–Rideal Mechanism played an important role in NO reduction over MnOx/TiO2, especially at higher temperatures. Therefore, N2O selectivity of the low temperature SCR reaction over MnOx/TiO2 decreased especially at higher temperatures after the increase of gaseous NO concentration.
-
Low temperature selective catalytic reduction of NO with NH3 over Mn–Fe spinel: Performance, Mechanism and kinetic study
Applied Catalysis B-environmental, 2011Co-Authors: Shijian Yang, Junhua Li, Chizhong Wang, Lei Ma, Huazheng ChangAbstract:Abstract (Fe3−xMnx)1−δO4 was synthesized using a co-precipitation method and then developed as a catalyst for the low temperature selective catalytic reduction (SCR) of NO with NH3. The SCR activity of (Fe3−xMnx)1−δO4 was clearly enhanced with the increase of Mn content. The results of in situ DRIFTS study demonstrated that both the Eley–Rideal Mechanism (i.e. reaction of activated ammonia with gaseous NO) and the Langmuir–Hinshelwood Mechanism (i.e. reaction of adsorbed ammonia species with adsorbed NOx species) might happen during the SCR reaction over (Fe3−xMnx)1−δO4. According to the kinetic analysis, the respective contribution of the Langmuir–Hinshelwood Mechanism and the Eley–Rideal Mechanism on the SCR reaction was studied. Only the adsorption of NO + O2 on (Fe2.8Mn0.2)1−δO4 was promoted, so the Langmuir–Hinshelwood Mechanism predominated over NO conversion on (Fe2.8Mn0.2)1−δO4 especially at lower temperatures. Both the adsorption of NO + O2 and the adsorption of NH3 on (Fe2.5Mn0.5)1−δO4 were obviously promoted, so NO conversion on (Fe2.5Mn0.5)1−δO4 mainly followed the Eley–Rideal Mechanism especially at higher temperatures. Both the nitrate route and the over-oxidization of adsorbed ammonia species contributed to the formation of N2O on (Fe2.8Mn0.2)1−δO4 above 140 °C. However, the formation of N2O on (Fe2.5Mn0.5)1−δO4 mainly resulted from the over-oxidization of adsorbed ammonia species. Although the activity of (Fe2.5Mn0.5)1−δO4 was suppressed in the presence of H2O and SO2, the deactivated catalyst can be regenerated after the water washing.
Shijian Yang - One of the best experts on this subject based on the ideXlab platform.
-
The Mechanism of the effect of H2O on the low temperature selective catalytic reduction of NO with NH3 over Mn–Fe spinel
Catalysis Science & Technology, 2015Co-Authors: Shangchao Xiong, Yong Liao, Xin Xiao, Hao Dang, Shijian YangAbstract:H2O showed a notable inhibition on the low temperature selective catalytic reduction (SCR) reaction over Mn based catalysts. However, the Mechanism of H2O effect was not clear. In this work, the Mechanism of H2O effect on the low temperature SCR reaction over Mn–Fe spinel was studied using the transient reaction study and the steady-state kinetic analysis. According to the steady-state kinetic analysis, the reaction kinetic rate constants of NO reduction over Mn–Fe spinel (including the rate constants of N2 formation through the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism, and the rate constants of N2O formation) in the presence of H2O and in the absence of H2O were compared. According to the transient reaction study, the effect of H2O on the elementary reactions of NO reduction over Mn–Fe spinel through both the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism was investigated. The results indicated that the effect of H2O on the low temperature SCR reaction over Mn–Fe spinel was not only attributed to the competition adsorption of H2O with NH3 and NOx, but also related to the decrease in the oxidation ability and the inhibition of the interface reaction.
-
Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.
Environmental Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Xin Xiao, Feihong Qi, Yue Peng, Yuwu Fu, Wenpo Shan, Junhua LiAbstract:The Mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn–Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley–Rideal Mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir–Hinshelwood Mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism was much less than that through the Eley–Rideal Mechanism. The ratio of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn–Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn–Fe spinel increased because of the promo...
-
Competition of selective catalytic reduction and non selective catalytic reduction over MnOx/TiO2 for NO removal: the relationship between gaseous NO concentration and N2O selectivity
Catalysis Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Yuwu Fu, Zan Qu, Junhua LiAbstract:In this work, a novel phenomenon was discovered that N2O selectivity of NO reduction over MnOx/TiO2 was related to the concentration of gaseous NO and that lower concentration of gaseous NO would cause higher N2O selectivity. In situ DRIFTS and transient reaction studies demonstrated that both the Eley–Rideal Mechanism (the reaction of over-activated NH3 with gaseous NO) and the Langmuir–Hinshelwood Mechanism (the reaction of adsorbed NO3− with adsorbed NH3 on the adjacent sites) could contribute to the formation of N2O. Kinetic study demonstrated that N2O selectivity would be independent of gaseous NO concentration if NO reduction over MnOx/TiO2 mainly followed the Langmuir–Hinshelwood Mechanism. If NO reduction over MnOx/TiO2 mainly followed the Eley–Rideal Mechanism, there was competition between the selective catalytic reduction (SCR) reaction and non selective catalytic reduction (NSCR) reaction. As gaseous NO concentration increased, more –NH2 was used to reduce gaseous NO to form N2 and the further oxidization of –NH2 to –NH was restrained, resulting in an obvious decrease of N2O selectivity. The Eley–Rideal Mechanism played an important role in NO reduction over MnOx/TiO2, especially at higher temperatures. Therefore, N2O selectivity of the low temperature SCR reaction over MnOx/TiO2 decreased especially at higher temperatures after the increase of gaseous NO concentration.
-
Low temperature selective catalytic reduction of NO with NH3 over Mn–Fe spinel: Performance, Mechanism and kinetic study
Applied Catalysis B-environmental, 2011Co-Authors: Shijian Yang, Junhua Li, Chizhong Wang, Lei Ma, Huazheng ChangAbstract:Abstract (Fe3−xMnx)1−δO4 was synthesized using a co-precipitation method and then developed as a catalyst for the low temperature selective catalytic reduction (SCR) of NO with NH3. The SCR activity of (Fe3−xMnx)1−δO4 was clearly enhanced with the increase of Mn content. The results of in situ DRIFTS study demonstrated that both the Eley–Rideal Mechanism (i.e. reaction of activated ammonia with gaseous NO) and the Langmuir–Hinshelwood Mechanism (i.e. reaction of adsorbed ammonia species with adsorbed NOx species) might happen during the SCR reaction over (Fe3−xMnx)1−δO4. According to the kinetic analysis, the respective contribution of the Langmuir–Hinshelwood Mechanism and the Eley–Rideal Mechanism on the SCR reaction was studied. Only the adsorption of NO + O2 on (Fe2.8Mn0.2)1−δO4 was promoted, so the Langmuir–Hinshelwood Mechanism predominated over NO conversion on (Fe2.8Mn0.2)1−δO4 especially at lower temperatures. Both the adsorption of NO + O2 and the adsorption of NH3 on (Fe2.5Mn0.5)1−δO4 were obviously promoted, so NO conversion on (Fe2.5Mn0.5)1−δO4 mainly followed the Eley–Rideal Mechanism especially at higher temperatures. Both the nitrate route and the over-oxidization of adsorbed ammonia species contributed to the formation of N2O on (Fe2.8Mn0.2)1−δO4 above 140 °C. However, the formation of N2O on (Fe2.5Mn0.5)1−δO4 mainly resulted from the over-oxidization of adsorbed ammonia species. Although the activity of (Fe2.5Mn0.5)1−δO4 was suppressed in the presence of H2O and SO2, the deactivated catalyst can be regenerated after the water washing.
Dmitry Yu. Murzin - One of the best experts on this subject based on the ideXlab platform.
-
Cluster Size Dependent Kinetics: Analysis of Different Reaction Mechanisms
Catalysis Letters, 2015Co-Authors: Dmitry Yu. MurzinAbstract:Quantitative description for turnover frequency dependence on the metal cluster size is discussed for competitive Langmuir–Hinshelwood Mechanism showing that the apparent reaction orders depend on the cluster size. Position of the maximum rate of the turnover frequency for a two-step sequence is a function on temperature and only in a special case, maximum of the turnover frequency is temperature independent on reaction temperature. For the same reaction Mechanism the impact of internal diffusion limitations on structure sensitivity is discussed. Graphical Abstract
-
Size-dependent heterogeneous catalytic kinetics
Journal of Molecular Catalysis A-chemical, 2010Co-Authors: Dmitry Yu. MurzinAbstract:Abstract A quantitative thermodynamic approach is considered with the aim to describe the size-dependent Langmuir–Hinshelwood Mechanism and the two-step catalytic cycle. The general treatment takes into account surface energy excess due to an intrinsic increase in chemical potential with size decrease as well as the changes in chemical potential upon adsorption. Numerical simulations as well as qualitative analysis show that for catalytic reactions over nanoparticles not only the rates but also reaction orders can vary depending on the size of nanoclusters. Comparison with experimental data is given.
-
Reaction kinetics and modelling of the gold catalysed glycerol oxidation
Topics in Catalysis, 2007Co-Authors: Séval Demirel, Tapio Salmi, Dmitry Yu. Murzin, Martin Lucas, Johan Wärnå, Peter ClausAbstract:The kinetics of the glycerol oxidation using a carbon supported gold catalyst was studied experimentally in a batch reactor at oxygen pressures up to 10 bar and at temperatures from 25 to 100 °C. The influence of the mass transfer on the reaction was estimated and confirmed with theoretical calculations. A kinetic model has been proposed on the basis of a Langmuir-Hinshelwood Mechanism for the experiments carried out in the kinetic regime and the kinetic parameters (reaction rate and adsorption constants as well as activation energies) were calculated.
Shangchao Xiong - One of the best experts on this subject based on the ideXlab platform.
-
The Mechanism of the effect of H2O on the low temperature selective catalytic reduction of NO with NH3 over Mn–Fe spinel
Catalysis Science & Technology, 2015Co-Authors: Shangchao Xiong, Yong Liao, Xin Xiao, Hao Dang, Shijian YangAbstract:H2O showed a notable inhibition on the low temperature selective catalytic reduction (SCR) reaction over Mn based catalysts. However, the Mechanism of H2O effect was not clear. In this work, the Mechanism of H2O effect on the low temperature SCR reaction over Mn–Fe spinel was studied using the transient reaction study and the steady-state kinetic analysis. According to the steady-state kinetic analysis, the reaction kinetic rate constants of NO reduction over Mn–Fe spinel (including the rate constants of N2 formation through the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism, and the rate constants of N2O formation) in the presence of H2O and in the absence of H2O were compared. According to the transient reaction study, the effect of H2O on the elementary reactions of NO reduction over Mn–Fe spinel through both the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism was investigated. The results indicated that the effect of H2O on the low temperature SCR reaction over Mn–Fe spinel was not only attributed to the competition adsorption of H2O with NH3 and NOx, but also related to the decrease in the oxidation ability and the inhibition of the interface reaction.
-
Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.
Environmental Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Xin Xiao, Feihong Qi, Yue Peng, Yuwu Fu, Wenpo Shan, Junhua LiAbstract:The Mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn–Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley–Rideal Mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir–Hinshelwood Mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism was much less than that through the Eley–Rideal Mechanism. The ratio of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn–Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn–Fe spinel increased because of the promo...
-
Competition of selective catalytic reduction and non selective catalytic reduction over MnOx/TiO2 for NO removal: the relationship between gaseous NO concentration and N2O selectivity
Catalysis Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Yuwu Fu, Zan Qu, Junhua LiAbstract:In this work, a novel phenomenon was discovered that N2O selectivity of NO reduction over MnOx/TiO2 was related to the concentration of gaseous NO and that lower concentration of gaseous NO would cause higher N2O selectivity. In situ DRIFTS and transient reaction studies demonstrated that both the Eley–Rideal Mechanism (the reaction of over-activated NH3 with gaseous NO) and the Langmuir–Hinshelwood Mechanism (the reaction of adsorbed NO3− with adsorbed NH3 on the adjacent sites) could contribute to the formation of N2O. Kinetic study demonstrated that N2O selectivity would be independent of gaseous NO concentration if NO reduction over MnOx/TiO2 mainly followed the Langmuir–Hinshelwood Mechanism. If NO reduction over MnOx/TiO2 mainly followed the Eley–Rideal Mechanism, there was competition between the selective catalytic reduction (SCR) reaction and non selective catalytic reduction (NSCR) reaction. As gaseous NO concentration increased, more –NH2 was used to reduce gaseous NO to form N2 and the further oxidization of –NH2 to –NH was restrained, resulting in an obvious decrease of N2O selectivity. The Eley–Rideal Mechanism played an important role in NO reduction over MnOx/TiO2, especially at higher temperatures. Therefore, N2O selectivity of the low temperature SCR reaction over MnOx/TiO2 decreased especially at higher temperatures after the increase of gaseous NO concentration.
Yong Liao - One of the best experts on this subject based on the ideXlab platform.
-
The Mechanism of the effect of H2O on the low temperature selective catalytic reduction of NO with NH3 over Mn–Fe spinel
Catalysis Science & Technology, 2015Co-Authors: Shangchao Xiong, Yong Liao, Xin Xiao, Hao Dang, Shijian YangAbstract:H2O showed a notable inhibition on the low temperature selective catalytic reduction (SCR) reaction over Mn based catalysts. However, the Mechanism of H2O effect was not clear. In this work, the Mechanism of H2O effect on the low temperature SCR reaction over Mn–Fe spinel was studied using the transient reaction study and the steady-state kinetic analysis. According to the steady-state kinetic analysis, the reaction kinetic rate constants of NO reduction over Mn–Fe spinel (including the rate constants of N2 formation through the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism, and the rate constants of N2O formation) in the presence of H2O and in the absence of H2O were compared. According to the transient reaction study, the effect of H2O on the elementary reactions of NO reduction over Mn–Fe spinel through both the Eley–Rideal Mechanism and the Langmuir–Hinshelwood Mechanism was investigated. The results indicated that the effect of H2O on the low temperature SCR reaction over Mn–Fe spinel was not only attributed to the competition adsorption of H2O with NH3 and NOx, but also related to the decrease in the oxidation ability and the inhibition of the interface reaction.
-
Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.
Environmental Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Xin Xiao, Feihong Qi, Yue Peng, Yuwu Fu, Wenpo Shan, Junhua LiAbstract:The Mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn–Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley–Rideal Mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir–Hinshelwood Mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism was much less than that through the Eley–Rideal Mechanism. The ratio of NO reduction over Mn–Fe spinel through the Langmuir–Hinshelwood Mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn–Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn–Fe spinel increased because of the promo...
-
Competition of selective catalytic reduction and non selective catalytic reduction over MnOx/TiO2 for NO removal: the relationship between gaseous NO concentration and N2O selectivity
Catalysis Science & Technology, 2014Co-Authors: Shijian Yang, Shangchao Xiong, Yong Liao, Yuwu Fu, Zan Qu, Junhua LiAbstract:In this work, a novel phenomenon was discovered that N2O selectivity of NO reduction over MnOx/TiO2 was related to the concentration of gaseous NO and that lower concentration of gaseous NO would cause higher N2O selectivity. In situ DRIFTS and transient reaction studies demonstrated that both the Eley–Rideal Mechanism (the reaction of over-activated NH3 with gaseous NO) and the Langmuir–Hinshelwood Mechanism (the reaction of adsorbed NO3− with adsorbed NH3 on the adjacent sites) could contribute to the formation of N2O. Kinetic study demonstrated that N2O selectivity would be independent of gaseous NO concentration if NO reduction over MnOx/TiO2 mainly followed the Langmuir–Hinshelwood Mechanism. If NO reduction over MnOx/TiO2 mainly followed the Eley–Rideal Mechanism, there was competition between the selective catalytic reduction (SCR) reaction and non selective catalytic reduction (NSCR) reaction. As gaseous NO concentration increased, more –NH2 was used to reduce gaseous NO to form N2 and the further oxidization of –NH2 to –NH was restrained, resulting in an obvious decrease of N2O selectivity. The Eley–Rideal Mechanism played an important role in NO reduction over MnOx/TiO2, especially at higher temperatures. Therefore, N2O selectivity of the low temperature SCR reaction over MnOx/TiO2 decreased especially at higher temperatures after the increase of gaseous NO concentration.
