The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based so...The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.展开更多
TWC-equipped exhausts are widely used in gasoline-fueled vehicles to meet stringent emission regulations. The main components in TWCs are precious metals such as palladium (Pd), platinum (Pt), and rhodium (Rh) as the ...TWC-equipped exhausts are widely used in gasoline-fueled vehicles to meet stringent emission regulations. The main components in TWCs are precious metals such as palladium (Pd), platinum (Pt), and rhodium (Rh) as the active component, and inorganic oxides such as γ-alumina (Al 2 O 3 ), ceria (CeO 2 ), zirconia (ZrO 2 ) and ceria-zirconia (CeO 2-ZrO 2 ) are used as the support. Interaction of precious metals and support plays an important role in the thermal stability and catalytic performance of TWCs. The support can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature. In the same, precious metals can also enhance the redox performance and oxygen storage capacity of support. This paper reviews the reaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and supports such as Al 2 O 3 , CeO 2-based composite oxides.展开更多
Six transition metal oxides were added in ceria-modified titania using a sol-gel method for catalytic oxidation of toluene.An MnOx based catalyst was found to be the most active one,with which toluene could be decompo...Six transition metal oxides were added in ceria-modified titania using a sol-gel method for catalytic oxidation of toluene.An MnOx based catalyst was found to be the most active one,with which toluene could be decomposed completely at 200 oC.The greatest Mn/Ti and molar ratio of the mobile oxygen to the total oxygen concentration,together with a large surface area and a low reduction peak-starting temperature,would result in its best activity in toluene oxidation.展开更多
Increasing applications of metal oxide nanoparticles and their release in the natural environment is a serious concern due to their toxic nature.Therefore,it is essential to have eco-friendly solutions for the remedia...Increasing applications of metal oxide nanoparticles and their release in the natural environment is a serious concern due to their toxic nature.Therefore,it is essential to have eco-friendly solutions for the remediation of toxic metal oxides in an aqueous environment.In the present study,eco-friendly Iron Oxide Nanoparticles(IONPs)are synthesized using solvothermal technique and successfully characterized using scanning and transmission electron microscopy(SEM and TEM respectively)and powder X-Ray diffraction(PXRD).These IONPs were further utilized for the remediation of toxic metal oxide nanoparticle,i.e.,Ce02.Sorption experiments were also performed in complex aqueous solutions and real water samples to check its applicability in the natural environment.Reusability study was performed to show cost-effectiveness.Results show that these 200 nm-sized spherical IONPs,as revealed by SEM and TEM analysis,were magnetite(Fe3O4)and contained short-range crystallinity as confirmed from XRD spectra.Sorption experiments show that the composite follows the pseudosecond-order kinetic model.Further k>0.99 for Langmuir sorption isotherm suggests chemisorption as probable removal mechanism with monolayer sorption of Ce02 NPs on IONP.More than 80%recovery of adsorbed Ce02 NPs through ultrasonication and magnetic separation of reaction precipitate confirms reusability of IONPs.Obtained removal%of Ce02 in various synthetic and real water samples was>90%signifying that IONPs are candidate adsorbent for the removal and recovery of toxic metal oxide nanoparticles from contaminated environmental water samples.展开更多
Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a cartier for active compotmds in catalysts but al...Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a cartier for active compotmds in catalysts but also can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature; meanwhile, noble metals can also enhance the redox performance and oxygen storage capacity of support. The mechanism of metal-support interactions mainly includes electronic interaction, formation of alloy and inward diffusion of metal into the support or covered by support. The form and degree of precious metal-sup- port interaction depend on many factors, including the content of precious metal, the species of support and metal, and preparation methods. The research results about strong metal-support interaction （SMSI） gave a theory support for developing a kind of new cata- lyst with excellent performance. This paper reviewed the interaction phenomenon and mechanism of precious metals （Pt, Pd, Rh） and support such as A1203, CeO2, and CeO2-based oxides in automotive exhaust catalysts. The factors that affect SMSI and the catalysts developed by SMSI were also discussed.展开更多
文摘The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.
基金National Science technology Support Plan Projects"(2012BAE06B00)
文摘TWC-equipped exhausts are widely used in gasoline-fueled vehicles to meet stringent emission regulations. The main components in TWCs are precious metals such as palladium (Pd), platinum (Pt), and rhodium (Rh) as the active component, and inorganic oxides such as γ-alumina (Al 2 O 3 ), ceria (CeO 2 ), zirconia (ZrO 2 ) and ceria-zirconia (CeO 2-ZrO 2 ) are used as the support. Interaction of precious metals and support plays an important role in the thermal stability and catalytic performance of TWCs. The support can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature. In the same, precious metals can also enhance the redox performance and oxygen storage capacity of support. This paper reviews the reaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and supports such as Al 2 O 3 , CeO 2-based composite oxides.
基金Project supported by Changjiang Scholar Incentive Program,Ministry of Education,China
文摘Six transition metal oxides were added in ceria-modified titania using a sol-gel method for catalytic oxidation of toluene.An MnOx based catalyst was found to be the most active one,with which toluene could be decomposed completely at 200 oC.The greatest Mn/Ti and molar ratio of the mobile oxygen to the total oxygen concentration,together with a large surface area and a low reduction peak-starting temperature,would result in its best activity in toluene oxidation.
基金We recognize financial support from the SERBRamanujan Fellowship grant(SB/S2/RJN-006/2016)SERB-ECR project grant(ECR/2017/000707) from Department of Science and Technology(DST),India.We are also thankful to the Indian Institute of Science Education and Research Kolkata's central instrumentation facility for TEM,FESEM,and PXRD analysis.
文摘Increasing applications of metal oxide nanoparticles and their release in the natural environment is a serious concern due to their toxic nature.Therefore,it is essential to have eco-friendly solutions for the remediation of toxic metal oxides in an aqueous environment.In the present study,eco-friendly Iron Oxide Nanoparticles(IONPs)are synthesized using solvothermal technique and successfully characterized using scanning and transmission electron microscopy(SEM and TEM respectively)and powder X-Ray diffraction(PXRD).These IONPs were further utilized for the remediation of toxic metal oxide nanoparticle,i.e.,Ce02.Sorption experiments were also performed in complex aqueous solutions and real water samples to check its applicability in the natural environment.Reusability study was performed to show cost-effectiveness.Results show that these 200 nm-sized spherical IONPs,as revealed by SEM and TEM analysis,were magnetite(Fe3O4)and contained short-range crystallinity as confirmed from XRD spectra.Sorption experiments show that the composite follows the pseudosecond-order kinetic model.Further k>0.99 for Langmuir sorption isotherm suggests chemisorption as probable removal mechanism with monolayer sorption of Ce02 NPs on IONP.More than 80%recovery of adsorbed Ce02 NPs through ultrasonication and magnetic separation of reaction precipitate confirms reusability of IONPs.Obtained removal%of Ce02 in various synthetic and real water samples was>90%signifying that IONPs are candidate adsorbent for the removal and recovery of toxic metal oxide nanoparticles from contaminated environmental water samples.
基金supported by National Science & Technology Pillar Program(2012BAE06B00)
文摘Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a cartier for active compotmds in catalysts but also can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature; meanwhile, noble metals can also enhance the redox performance and oxygen storage capacity of support. The mechanism of metal-support interactions mainly includes electronic interaction, formation of alloy and inward diffusion of metal into the support or covered by support. The form and degree of precious metal-sup- port interaction depend on many factors, including the content of precious metal, the species of support and metal, and preparation methods. The research results about strong metal-support interaction （SMSI） gave a theory support for developing a kind of new cata- lyst with excellent performance. This paper reviewed the interaction phenomenon and mechanism of precious metals （Pt, Pd, Rh） and support such as A1203, CeO2, and CeO2-based oxides in automotive exhaust catalysts. The factors that affect SMSI and the catalysts developed by SMSI were also discussed.
