The effect of molybdenum oxide on the activity and durability of Ce O2-Ti O2 catalyst for NO reduction by NH3 was examined. It was found that the introduction of Mo could improve the low-temperature NH3-SCR activity a...The effect of molybdenum oxide on the activity and durability of Ce O2-Ti O2 catalyst for NO reduction by NH3 was examined. It was found that the introduction of Mo could improve the low-temperature NH3-SCR activity and SO2/H2 O durability of the Ce O2-Ti O2 catalyst and an optimal loading of Mo was 4?wt.%. The best Mo O3/Ce O2-Ti O2 catalyst displayed over 90% NO conversion from 200 °C to 400 °C and obtained 4-fold increase in NO conversion compared to Ce O2-Ti O2 at 150 °C. The characterization results revealed that the number of Br?nsted acid sites over Mo O3/Ce O2-Ti O2 was significantly increased, and the adsorption of nitrate species was dramatically weakened because of the coverage of Mo O3, which were favorable for the high NH3-SCR performance. It is believed that the Mo O3/Ce O2-Ti O2 catalyst is a suitable substitute for the NH3-SCR reaction.展开更多
Two series of molybdenum-containing MCM-41 catalysts were prepared for oxidative desulfurization ofdibenzothiophene （DBT） using t-butylhydroperoxide （TBHP） as the oxidant. The electronic properties, pore dimension...Two series of molybdenum-containing MCM-41 catalysts were prepared for oxidative desulfurization ofdibenzothiophene （DBT） using t-butylhydroperoxide （TBHP） as the oxidant. The electronic properties, pore dimension and hydrophilic properties of the catalysts were studied by XRD, BET, and 1R spectrometry. The Mo-Al2O3 catalyst and TiMCM-3% were also studied for comparison. The two series of MCM-41 zeolite with MoO3 in the framework or impregnated on the surface exhibited considerable activities at low MoO3 content and both were faxbetter than the Mo-Al2O3 catalyst, but had lower activities as compared to the TiMCM-3% catalyst. The catalysts with the highest activity were evaluated in a fixed-bed reactor. The concentration of DBT in model diesel upon oxidative desulfurization was successfully reduced from 5000 ppm to less than 150 ppm, but the catalysts were deactivated very fast. The probable reason was the high affinity of DBTO2 to the MCM-41 skeleton, especially to MoO3. The catalysts could restore most of its original activity by treating with alcohol.展开更多
In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were...In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.展开更多
We present a comparison of Mo, V and Nb oxides as shell materials atop haematite cores used for selective methanol oxidation. While Mo and V both yield high selectivity to formaldehyde, Nb does not. Very different rea...We present a comparison of Mo, V and Nb oxides as shell materials atop haematite cores used for selective methanol oxidation. While Mo and V both yield high selectivity to formaldehyde, Nb does not. Very different reactivity patterns are seen for Nb, which mainly shows dehydrogenation (to CO) and dehydration (to DME), indicating the lack of a complete shell, while Raman spectroscopy shows that the Mo and V formation process is not followed by NbOx. We suggest this is due to the large differences in mobility within the solid materials during formation, NbOx requiring significantly higher (and deleterious) calcination temperatures to allow sufficient mobility for shell completion.展开更多
The kinetics of epoxidation of methylbutene with structurally identical methylbutane hydroperoxide was studied in the presence of a molybdenum catalyst. The analysis of the rate curves suggested the most probable sche...The kinetics of epoxidation of methylbutene with structurally identical methylbutane hydroperoxide was studied in the presence of a molybdenum catalyst. The analysis of the rate curves suggested the most probable scheme of the process. The revealed features of the process and its mathematical description make it possible to more competently design a reactor unit for the commercial production of isoprene according to the developed scheme. The main kinetic constants were calculated.展开更多
Synthesis of cyclic carbonates from carbon dioxide(CO_(2))and epoxides is an effective pathway for the CO_(2) utilization.Although various metal catalysts have been reported,it is highly desirable to develop a method ...Synthesis of cyclic carbonates from carbon dioxide(CO_(2))and epoxides is an effective pathway for the CO_(2) utilization.Although various metal catalysts have been reported,it is highly desirable to develop a method for the reuse or recycling of catalysts.Herein,an N-heterocyclic carbene-pyridine molybdenum complex supported over SBA-15(Mo@SBA-15)was used as an efficient and recyclable catalyst for converting CO_(2) and epoxides into cyclic carbonates.Mo@SBA-15 in combination with tetra-butylammonium bromide(TBAB)shows high catalytic activity in the synthesis of cyclic carbonates under 100℃and 1 MPa CO_(2) pressure.In addition,Mo@SBA-15 was reused seven times without any significant activity loss.展开更多
Electron-hole separation is a critical step to achieving efficient photocatalysis, towards which use of co-catalysts has become a widely used strategy. Despite the tremendous efforts and demonstrated functions of nobl...Electron-hole separation is a critical step to achieving efficient photocatalysis, towards which use of co-catalysts has become a widely used strategy. Despite the tremendous efforts and demonstrated functions of noble metal co-catalysts, seeking noble metal-free co-catalysts will always be the goal when designing cost- effective, high-performance hybrid photocatalysts. In this work, we demonstrate that MoS~ nanosheets with 1T phase （i.e., octahedral phase） can function as a co-catalyst with multiple merits： （1） Noble-metal-free; （2） high mobility for charge transport; （3） high density of active sites for H2 evolution on basal planes; （4） good performance stability; （5） high light transparency. As demonstrated in both photocatalytic hydrogen production and Rhodamine B degradation, the developed hybrid structure with TiO2 exhibits excellent performance, in sharp contrast to bare TiO2 and the hybrid counterpart with 2H-MoS2.展开更多
基金supported by the National Natural Science Foundation of China(21773106,21707066,21677069,and 21806077)the China Postdoctoral Science Foundation(2018M642206)~~
文摘The effect of molybdenum oxide on the activity and durability of Ce O2-Ti O2 catalyst for NO reduction by NH3 was examined. It was found that the introduction of Mo could improve the low-temperature NH3-SCR activity and SO2/H2 O durability of the Ce O2-Ti O2 catalyst and an optimal loading of Mo was 4?wt.%. The best Mo O3/Ce O2-Ti O2 catalyst displayed over 90% NO conversion from 200 °C to 400 °C and obtained 4-fold increase in NO conversion compared to Ce O2-Ti O2 at 150 °C. The characterization results revealed that the number of Br?nsted acid sites over Mo O3/Ce O2-Ti O2 was significantly increased, and the adsorption of nitrate species was dramatically weakened because of the coverage of Mo O3, which were favorable for the high NH3-SCR performance. It is believed that the Mo O3/Ce O2-Ti O2 catalyst is a suitable substitute for the NH3-SCR reaction.
文摘Two series of molybdenum-containing MCM-41 catalysts were prepared for oxidative desulfurization ofdibenzothiophene （DBT） using t-butylhydroperoxide （TBHP） as the oxidant. The electronic properties, pore dimension and hydrophilic properties of the catalysts were studied by XRD, BET, and 1R spectrometry. The Mo-Al2O3 catalyst and TiMCM-3% were also studied for comparison. The two series of MCM-41 zeolite with MoO3 in the framework or impregnated on the surface exhibited considerable activities at low MoO3 content and both were faxbetter than the Mo-Al2O3 catalyst, but had lower activities as compared to the TiMCM-3% catalyst. The catalysts with the highest activity were evaluated in a fixed-bed reactor. The concentration of DBT in model diesel upon oxidative desulfurization was successfully reduced from 5000 ppm to less than 150 ppm, but the catalysts were deactivated very fast. The probable reason was the high affinity of DBTO2 to the MCM-41 skeleton, especially to MoO3. The catalysts could restore most of its original activity by treating with alcohol.
基金Supported by the Iranian Nano Technology Initiative Council and Petroleum University of Technology
文摘In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.
基金EPSRC for support via the UK Catalysis Hub(EP/K014854/1,EP/K014714/1)EPSRC and Diamond Light Source for funding the studentship to PH
文摘We present a comparison of Mo, V and Nb oxides as shell materials atop haematite cores used for selective methanol oxidation. While Mo and V both yield high selectivity to formaldehyde, Nb does not. Very different reactivity patterns are seen for Nb, which mainly shows dehydrogenation (to CO) and dehydration (to DME), indicating the lack of a complete shell, while Raman spectroscopy shows that the Mo and V formation process is not followed by NbOx. We suggest this is due to the large differences in mobility within the solid materials during formation, NbOx requiring significantly higher (and deleterious) calcination temperatures to allow sufficient mobility for shell completion.
文摘The kinetics of epoxidation of methylbutene with structurally identical methylbutane hydroperoxide was studied in the presence of a molybdenum catalyst. The analysis of the rate curves suggested the most probable scheme of the process. The revealed features of the process and its mathematical description make it possible to more competently design a reactor unit for the commercial production of isoprene according to the developed scheme. The main kinetic constants were calculated.
文摘Synthesis of cyclic carbonates from carbon dioxide(CO_(2))and epoxides is an effective pathway for the CO_(2) utilization.Although various metal catalysts have been reported,it is highly desirable to develop a method for the reuse or recycling of catalysts.Herein,an N-heterocyclic carbene-pyridine molybdenum complex supported over SBA-15(Mo@SBA-15)was used as an efficient and recyclable catalyst for converting CO_(2) and epoxides into cyclic carbonates.Mo@SBA-15 in combination with tetra-butylammonium bromide(TBAB)shows high catalytic activity in the synthesis of cyclic carbonates under 100℃and 1 MPa CO_(2) pressure.In addition,Mo@SBA-15 was reused seven times without any significant activity loss.
文摘Electron-hole separation is a critical step to achieving efficient photocatalysis, towards which use of co-catalysts has become a widely used strategy. Despite the tremendous efforts and demonstrated functions of noble metal co-catalysts, seeking noble metal-free co-catalysts will always be the goal when designing cost- effective, high-performance hybrid photocatalysts. In this work, we demonstrate that MoS~ nanosheets with 1T phase （i.e., octahedral phase） can function as a co-catalyst with multiple merits： （1） Noble-metal-free; （2） high mobility for charge transport; （3） high density of active sites for H2 evolution on basal planes; （4） good performance stability; （5） high light transparency. As demonstrated in both photocatalytic hydrogen production and Rhodamine B degradation, the developed hybrid structure with TiO2 exhibits excellent performance, in sharp contrast to bare TiO2 and the hybrid counterpart with 2H-MoS2.
