CO self-poisoning and slow surface kinetics pose major challenges to a CO oxidation catalyst that should work at ambient temperature.Furthermore,the presence of moisture would cause passivation of the catalyst A highl...CO self-poisoning and slow surface kinetics pose major challenges to a CO oxidation catalyst that should work at ambient temperature.Furthermore,the presence of moisture would cause passivation of the catalyst A highly active ceria promoted Pt catalyst（4%Pt-12%CeO_2/SiO_2;conversion≥99%at low（ 500 ppm） and high（ 2500 ppm） CO concentrations was developed for CO oxidation at ambient temperature in humid air.Catalyst preparation variables such as Pt and CeO_2 loading,ceria deposition method,drying and calcination conditions for the ceria and Pt precursors were optimized experimentally.The activity was correlated with surface properties using CO/H_2 chemisorption,O_2-H_2 titration,X-ray diffraction and BET surface area analysis.The method of CeO_2 deposition had a significant impact on the catalytic activity.CeO_2 deposition by impregnation resulted in a catalyst that was three times more active than that prepared by deposition precipitation or CeO_2grafting.O_2-H_2 titration results revealed that the close association of ceria and Pt in the case of CeO_2deposition by impregnation resulted in higher activity.The catalyst support used was also crucial as a silica supported catalyst was five times more active than an alumina supported catalyst.The particle size and pore structure of the catalyst support were also crucial as the reaction was diffusion controlled.The drying and calcination conditions of the ceria and Pt precursors also played a crucial role in determining the catalytic activity.The Pt-CeO_2/SiO_2 catalysts with Pt 2.5 wt%and CeO_2 15 wt%were highly active（TOF 0.02 s^（-1）） and stable（conversion 99%after 15 h） at ambient conditions.展开更多
Pyrite is a ubiquitous authigenic mineral in modern anoxic sediments and occurs in ancient sedimentary rocks.Study of sedimentary pyrite morphology, which can provide useful information on deposition environments and ...Pyrite is a ubiquitous authigenic mineral in modern anoxic sediments and occurs in ancient sedimentary rocks.Study of sedimentary pyrite morphology, which can provide useful information on deposition environments and early diagenetic processes,has become an important aspect for reconstruction of palaeoenviroment.The Upper Cretaceous Qingshankou Formation Unit 1（K<sub>2</sub>qn<sup>1</sup>）lithology,which occured in the south well of the SLCORE I for Continental Cretaceous Scientific Drilling Project展开更多
The conversion of biomass to chemicals/fuels has emerged as a valuable solution that offers both environmental and economic benefits,with the transformation of carbohydrate into formic acid garnering escalating schola...The conversion of biomass to chemicals/fuels has emerged as a valuable solution that offers both environmental and economic benefits,with the transformation of carbohydrate into formic acid garnering escalating scholar interest.However,the relative limited efficiency of catalyzed-oxidation or expensive cost of H_(2)O_(2) and alkali in wet hydrother-mal oxidation impose limitations on industrialization.This paper proposed a new idea for formic acid production by O_(2)-H_(2)O_(2) co-oxidation of carbohydrate.A two-step reaction method was developed,where the initial step is engi-neered to regulate the carbon chain cleavage of carbohydrates to augment the production of active intermediate.Oxygen was employed in the subsequent step as effective oxidant through free radical mechanism,resulting in a for-mic acid yield of 82.6%.Theoretical calculation,intermediates detection and real time EPR confirmed the reaction mechanism.Finally,the universality of the reaction was verified by using disaccharides and polysaccharides such as cellulose as substrates.展开更多
Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s ...Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s interior.In this study,we report the two new hydrous phases,Al_(2)SiO_(6)H_(2)and Al_(5.5)Si_(4)O_(18)H_(3.5)(hereafter referred to simply as phases Psi and Phi,respectively),which are synthesized in the Al_(2)O_(3)-SiO_(2)-H_(2)O system at 15.5 GPa,1400℃and 17.5 GPa,1600℃ by using Sakura2500-ton multi-anvil apparatus.The luminescence spectra of Cr3+show the phase Psi has characteristic peaks at 687,693 and705 nm,while phase Phi has characteristic peaks at 691,696 and 708 nm.Single-crystal X-ray diffraction (SCXRD) refinements yield a monoclinic structure of both phases (space group P2_(1)) with ideal chemical formulae of Al_(2)SiO6H2and Al5.5Si4O18H3.5respectively.The determined lattice parameters for phase Psi are a=9.4168±0.0016Å,b=4.3441±0.0007Å,c=9.4360±0.002Åand β=119.726±0.005°at ambient pressure and 300 K,while the phase Phi has a=7.2549±0.0018Å,b=4.3144±0.001Å,c=8.0520±0.002Å,and β=101.740±0.009°at ambient pressure and 250 K.Electron microprobe analyses (EPMA) show the chemical compositions of phases Psi and Phi to be Al_(1.99)Si_(0.85)O_(6)H_(2.62)and Al_(5.58)Si_(2.81)O_(18)H_(8.03),respectively,which slightly deviate from the ideal formulae inferred from SCXRD measurements.This may result from the disorder or substitution of Al and Si by H in the crystal structures under our synthesis conditions.Our study suggests that phases Psi and Phi are the two potential water carriers at the upper part of the mantle transitions zone,providing new insights into how deep water is stored in this region.展开更多
基金supported by US Army contract(W56HZV-05-C0686) at Auburn University administered through TARDEC
文摘CO self-poisoning and slow surface kinetics pose major challenges to a CO oxidation catalyst that should work at ambient temperature.Furthermore,the presence of moisture would cause passivation of the catalyst A highly active ceria promoted Pt catalyst（4%Pt-12%CeO_2/SiO_2;conversion≥99%at low（ 500 ppm） and high（ 2500 ppm） CO concentrations was developed for CO oxidation at ambient temperature in humid air.Catalyst preparation variables such as Pt and CeO_2 loading,ceria deposition method,drying and calcination conditions for the ceria and Pt precursors were optimized experimentally.The activity was correlated with surface properties using CO/H_2 chemisorption,O_2-H_2 titration,X-ray diffraction and BET surface area analysis.The method of CeO_2 deposition had a significant impact on the catalytic activity.CeO_2 deposition by impregnation resulted in a catalyst that was three times more active than that prepared by deposition precipitation or CeO_2grafting.O_2-H_2 titration results revealed that the close association of ceria and Pt in the case of CeO_2deposition by impregnation resulted in higher activity.The catalyst support used was also crucial as a silica supported catalyst was five times more active than an alumina supported catalyst.The particle size and pore structure of the catalyst support were also crucial as the reaction was diffusion controlled.The drying and calcination conditions of the ceria and Pt precursors also played a crucial role in determining the catalytic activity.The Pt-CeO_2/SiO_2 catalysts with Pt 2.5 wt%and CeO_2 15 wt%were highly active（TOF 0.02 s^（-1）） and stable（conversion 99%after 15 h） at ambient conditions.
文摘Pyrite is a ubiquitous authigenic mineral in modern anoxic sediments and occurs in ancient sedimentary rocks.Study of sedimentary pyrite morphology, which can provide useful information on deposition environments and early diagenetic processes,has become an important aspect for reconstruction of palaeoenviroment.The Upper Cretaceous Qingshankou Formation Unit 1（K<sub>2</sub>qn<sup>1</sup>）lithology,which occured in the south well of the SLCORE I for Continental Cretaceous Scientific Drilling Project
基金support of the National Natural Science Foundation of China(No.21978170&22108171)the Natural Science Foundation of Shanghai(No.23ZR1435200)Shanghai Key Laboratory of Hydrogen Science&Center of Hydrogen Science,Shanghai Jiao Tong University,China.
文摘The conversion of biomass to chemicals/fuels has emerged as a valuable solution that offers both environmental and economic benefits,with the transformation of carbohydrate into formic acid garnering escalating scholar interest.However,the relative limited efficiency of catalyzed-oxidation or expensive cost of H_(2)O_(2) and alkali in wet hydrother-mal oxidation impose limitations on industrialization.This paper proposed a new idea for formic acid production by O_(2)-H_(2)O_(2) co-oxidation of carbohydrate.A two-step reaction method was developed,where the initial step is engi-neered to regulate the carbon chain cleavage of carbohydrates to augment the production of active intermediate.Oxygen was employed in the subsequent step as effective oxidant through free radical mechanism,resulting in a for-mic acid yield of 82.6%.Theoretical calculation,intermediates detection and real time EPR confirmed the reaction mechanism.Finally,the universality of the reaction was verified by using disaccharides and polysaccharides such as cellulose as substrates.
基金supported by the Special Research Fund for the Doctoral Program of Tongren University(Grant No.trxyDH2201)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB42000000)the National Key Research and Development Program of China(Grant No.2019YFA0708502)。
文摘Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s interior.In this study,we report the two new hydrous phases,Al_(2)SiO_(6)H_(2)and Al_(5.5)Si_(4)O_(18)H_(3.5)(hereafter referred to simply as phases Psi and Phi,respectively),which are synthesized in the Al_(2)O_(3)-SiO_(2)-H_(2)O system at 15.5 GPa,1400℃and 17.5 GPa,1600℃ by using Sakura2500-ton multi-anvil apparatus.The luminescence spectra of Cr3+show the phase Psi has characteristic peaks at 687,693 and705 nm,while phase Phi has characteristic peaks at 691,696 and 708 nm.Single-crystal X-ray diffraction (SCXRD) refinements yield a monoclinic structure of both phases (space group P2_(1)) with ideal chemical formulae of Al_(2)SiO6H2and Al5.5Si4O18H3.5respectively.The determined lattice parameters for phase Psi are a=9.4168±0.0016Å,b=4.3441±0.0007Å,c=9.4360±0.002Åand β=119.726±0.005°at ambient pressure and 300 K,while the phase Phi has a=7.2549±0.0018Å,b=4.3144±0.001Å,c=8.0520±0.002Å,and β=101.740±0.009°at ambient pressure and 250 K.Electron microprobe analyses (EPMA) show the chemical compositions of phases Psi and Phi to be Al_(1.99)Si_(0.85)O_(6)H_(2.62)and Al_(5.58)Si_(2.81)O_(18)H_(8.03),respectively,which slightly deviate from the ideal formulae inferred from SCXRD measurements.This may result from the disorder or substitution of Al and Si by H in the crystal structures under our synthesis conditions.Our study suggests that phases Psi and Phi are the two potential water carriers at the upper part of the mantle transitions zone,providing new insights into how deep water is stored in this region.
