Selective oxidation of propane to acetone(AC)with H_(2) and O_(2) provides a direct route to convert low-cost propane into valueadded products.Unfortunately,the catalytic activity of conventional Au/Ti-based catalysts...Selective oxidation of propane to acetone(AC)with H_(2) and O_(2) provides a direct route to convert low-cost propane into valueadded products.Unfortunately,the catalytic activity of conventional Au/Ti-based catalysts is constrained by the high energy barrier for H_(2) dissociation.Herein,uncalcined TS-1 supported Au-Pd bimetallic catalysts were prepared,and the relationship between the active-site structure and corresponding performance in the selective oxidation of propane with H_(2) and O_(2) in the gas phase was systematically investigated.In contrast to the liquid-phase reaction,trace Pd alloyed with Au triggered an increase in both catalytic activity and selectivity,in which Au_(20)-Pd_(1)/TS-1-B catalyst exhibited excellent activity(170 gAC·h^(−1)·kgcat^(−1))and AC selectivity(90.6%),much higher than those of the Au/TS-1-B catalyst(AC formation rate of 100 gAC·h^(−1)·kgcat^(−1)and AC selectivity of 86.3%).It was found that Pd was gradually isolated into monomers with the increase of Au/Pd molar ratio,and the synergy between Pd single atoms and Au improved the catalytic performance via enhancing hydrogen dissociation and modulating the electronic structure of Au.Furthermore,the reaction conditions were optimized based on the kinetics studies and the Au_(20)-Pd_(1)/TS-1-B catalyst exhibited enhanced H_(2) selectivity(45%)and long-term stability(over 130 h).The insights gained here can offer valuable guidance for the design of Au-Pd catalysts applicable to other gas-phase oxidation reactions.展开更多
High pressure roll grinding（HPRG）and ball milling were compared to investigate the influence of mechanical activation on the acid leaching dephosphorization of a high-phosphorus iron ore concentrate,which was manufa...High pressure roll grinding（HPRG）and ball milling were compared to investigate the influence of mechanical activation on the acid leaching dephosphorization of a high-phosphorus iron ore concentrate,which was manufactured through magnetizing roasting-magnetic separation of high-phosphorus oolitic iron ores.The results indicated that when high-phosphorus iron ore concentrates containing 54.92 mass% iron and 0.76 mass% phosphorus were directly processed through acid leaching,iron ore concentrates containing 55.74mass%iron and 0.33mass%phosphorus with an iron recovery of 84.64%and dephosphorization of 63.79% were obtained.When high-phosphorus iron ore concentrates activated by ball milling were processed by acid leaching,iron ore concentrates containing56.03mass%iron and 0.21mass% phosphorus with an iron recovery of 85.65% and dephosphorization of 77.49%were obtained.Meanwhile,when high-phosphorus iron ore concentrates activated by HPRG were processed by acid leaching,iron ore concentrates containing 58.02mass%iron and 0.10mass% phosphorus were obtained,with the iron recovery reaching 88.42% and the dephosphorization rate reaching 88.99%.Mechanistic studies demonstrated that ball milling can reduce the particle size,demonstrating aprominent reunion phenomenon.In contrast,HPRG pretreatment contributes to the formation of more cracks within the particles and selective dissociation of iron and P bearing minerals,which can provide the favorable kinetic conditions to accelerate the solid-liquid reaction rate.As such,the crystal structure is destroyed and the surface energy of mineral particles is strengthened by mechanical activation,further strengthening the dephosphorization.展开更多
Methane is a major component of natural gas. The activation and selectiveconversion of methane are one of the most difficult problems in chemistry because itis a thermodynamically most stable compound with an inert ga...Methane is a major component of natural gas. The activation and selectiveconversion of methane are one of the most difficult problems in chemistry because itis a thermodynamically most stable compound with an inert gas-like configuration.The oxidizing conditions usually are favourable for the conversion of methane;however, it is difficult to control and minimize the complete oxidation of methane展开更多
We theoretically investigate the production of cold CN molecules by photodissociating ICN precursors in a brute-force field. The energy shifts and adiabatic orientation of the rotational ICN precursors are first inves...We theoretically investigate the production of cold CN molecules by photodissociating ICN precursors in a brute-force field. The energy shifts and adiabatic orientation of the rotational ICN precursors are first investigated as a function of the external field strength. The dynamical photofragmentation of ICN precursors is numerically simulated for cases with and without orienting field. The CN products are compared in terms of their velocity distributions. A small portion of the CN fragments are recoiled to near zero speed in the lab frame by appropriately selecting the photo energy for dissociation. With a precursor ICN molecular beam of - 1.5 K in rotational temperature, the production of low speed CN fragments can be improved by more than 5 times when an orienting electrical field of 100 k V/cm is present. The corresponding production rate for decelerated fragments with speeds ≤ 50 m/s is simulated to be about ～2.1×10^-4 and CN number densities of 10^8 –10^10 cm^-3 can be reached with precursor ICN densities of ～10^12 –10^14 cm^-3 from supersonic expansion.展开更多
基金supported by the Ministry of Science and Technology of the People’s Republic of China under the Research Fund for National Key Research and Development Program of China(No.2021YFA1501403)the National Natural Science Foundation of China(Nos.22208093,22038003,and 22178100)+2 种基金the Shanghai Science and Technology Innovation Action Plan(No.22JC1403800)the Innovation Program of the Shanghai Municipal Education Commission,the Program of Shanghai Academic/Technology Research Leader(No.21XD1421000)the Fundamental Research Funds for the Central Universities.
文摘Selective oxidation of propane to acetone(AC)with H_(2) and O_(2) provides a direct route to convert low-cost propane into valueadded products.Unfortunately,the catalytic activity of conventional Au/Ti-based catalysts is constrained by the high energy barrier for H_(2) dissociation.Herein,uncalcined TS-1 supported Au-Pd bimetallic catalysts were prepared,and the relationship between the active-site structure and corresponding performance in the selective oxidation of propane with H_(2) and O_(2) in the gas phase was systematically investigated.In contrast to the liquid-phase reaction,trace Pd alloyed with Au triggered an increase in both catalytic activity and selectivity,in which Au_(20)-Pd_(1)/TS-1-B catalyst exhibited excellent activity(170 gAC·h^(−1)·kgcat^(−1))and AC selectivity(90.6%),much higher than those of the Au/TS-1-B catalyst(AC formation rate of 100 gAC·h^(−1)·kgcat^(−1)and AC selectivity of 86.3%).It was found that Pd was gradually isolated into monomers with the increase of Au/Pd molar ratio,and the synergy between Pd single atoms and Au improved the catalytic performance via enhancing hydrogen dissociation and modulating the electronic structure of Au.Furthermore,the reaction conditions were optimized based on the kinetics studies and the Au_(20)-Pd_(1)/TS-1-B catalyst exhibited enhanced H_(2) selectivity(45%)and long-term stability(over 130 h).The insights gained here can offer valuable guidance for the design of Au-Pd catalysts applicable to other gas-phase oxidation reactions.
基金supported by the National Natural Science Foundation of China(No.22178392)the Fundamental Research Funds for the Central Universities of Central South University,China(No.2022ZZTS0493)。
基金Item Sponsored by National Torch Program Project of China(2011GH561685)
文摘High pressure roll grinding（HPRG）and ball milling were compared to investigate the influence of mechanical activation on the acid leaching dephosphorization of a high-phosphorus iron ore concentrate,which was manufactured through magnetizing roasting-magnetic separation of high-phosphorus oolitic iron ores.The results indicated that when high-phosphorus iron ore concentrates containing 54.92 mass% iron and 0.76 mass% phosphorus were directly processed through acid leaching,iron ore concentrates containing 55.74mass%iron and 0.33mass%phosphorus with an iron recovery of 84.64%and dephosphorization of 63.79% were obtained.When high-phosphorus iron ore concentrates activated by ball milling were processed by acid leaching,iron ore concentrates containing56.03mass%iron and 0.21mass% phosphorus with an iron recovery of 85.65% and dephosphorization of 77.49%were obtained.Meanwhile,when high-phosphorus iron ore concentrates activated by HPRG were processed by acid leaching,iron ore concentrates containing 58.02mass%iron and 0.10mass% phosphorus were obtained,with the iron recovery reaching 88.42% and the dephosphorization rate reaching 88.99%.Mechanistic studies demonstrated that ball milling can reduce the particle size,demonstrating aprominent reunion phenomenon.In contrast,HPRG pretreatment contributes to the formation of more cracks within the particles and selective dissociation of iron and P bearing minerals,which can provide the favorable kinetic conditions to accelerate the solid-liquid reaction rate.As such,the crystal structure is destroyed and the surface energy of mineral particles is strengthened by mechanical activation,further strengthening the dephosphorization.
基金Project supported by the National Natural Science Foundation of China.
文摘Methane is a major component of natural gas. The activation and selectiveconversion of methane are one of the most difficult problems in chemistry because itis a thermodynamically most stable compound with an inert gas-like configuration.The oxidizing conditions usually are favourable for the conversion of methane;however, it is difficult to control and minimize the complete oxidation of methane
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504112,91536218,and 11604100)
文摘We theoretically investigate the production of cold CN molecules by photodissociating ICN precursors in a brute-force field. The energy shifts and adiabatic orientation of the rotational ICN precursors are first investigated as a function of the external field strength. The dynamical photofragmentation of ICN precursors is numerically simulated for cases with and without orienting field. The CN products are compared in terms of their velocity distributions. A small portion of the CN fragments are recoiled to near zero speed in the lab frame by appropriately selecting the photo energy for dissociation. With a precursor ICN molecular beam of - 1.5 K in rotational temperature, the production of low speed CN fragments can be improved by more than 5 times when an orienting electrical field of 100 k V/cm is present. The corresponding production rate for decelerated fragments with speeds ≤ 50 m/s is simulated to be about ～2.1×10^-4 and CN number densities of 10^8 –10^10 cm^-3 can be reached with precursor ICN densities of ～10^12 –10^14 cm^-3 from supersonic expansion.
