Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for the...Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for these systems remains a scientific challenge.In this work,copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity(up to 25.5%conversion and 66.8%selectivity)in the propylene-selective oxidation of acrolein at 300℃.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide(CuO)clusters into cuprous oxide(Cu2O)clusters.With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy(DB-FTIR),the allyl intermediate(CH2=CHCH2*)was clearly observed,along with the as-formed Cu2O species.The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process,and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene.展开更多
When trinuclear molybdenum cluster compound with 'loose coordination site', Mo_3(μ_3-S)(μ-S)_3(μ-dtp)(dtp)_3·H_2O(A) (dtp=diethyldithiophos-phinato anion), is reacted with an excess of imidazole, the H...When trinuclear molybdenum cluster compound with 'loose coordination site', Mo_3(μ_3-S)(μ-S)_3(μ-dtp)(dtp)_3·H_2O(A) (dtp=diethyldithiophos-phinato anion), is reacted with an excess of imidazole, the H_2O ligand and the bidentate bridging ligand μ-dtp are found to be simultaneously substituted by the imidazole to form the title compound. The title crystal belongs to the space group P(?), Z =2, with the following unit cell parameters: a=14.465(2), b=14.653(4), c=14.886(6), α=99.36(3),β=93.11(2),γ=114.29(2),V=2812(3). The crystalline compound consists of an ordered array of the cluster cation and dtp anion with acetone as packed molecule. The cation possesses a symmetry of C_3. Three Mo atoms form basically an equilateral triangle with three Mo—Mo bond lengths of 2.763 (1), 2.762(1), 2.756(1) respectively.展开更多
The existing research of sequential zoning system and simultaneous zoning system mainly focuses on some optimization problems such as workload balance,product assignment and simulation for each system separately.But t...The existing research of sequential zoning system and simultaneous zoning system mainly focuses on some optimization problems such as workload balance,product assignment and simulation for each system separately.But there is little research on comparative study between sequential zoning and simultaneous zoning.In order to help the designers to choose the suitable zoning policy for picker-to-parts system reasonably and quickly,a systemic selection method is presented.Essentially,both zoning and batching are order clustering,so the customer order sheet can be divided into many unit grids.After the time formulation in one-dimensional unit was defined,the time models for each zoning policy in two-dimensional space were established using filling curves and sequence models to link the one-dimensional unit grids.In consideration of ＂U＂ shaped dual tour into consideration,the subtraction value of order picking time between sequential zoning and simultaneous zoning was defined as the objective function to select the suitable zoning policy based on time models.As it is convergent enough,genetic algorithm is adopted to find the optimal value of order picking time.In the experimental study,5 different kinds of order/stock keeping unit（SKU） matrices with different densities d and quantities q following uniform distribution were created in order to test the suitability of sequential zoning and simultaneous zoning to different kinds of orders.After parameters setting,experimental orders inputting and iterative computations,the optimal order picking time for each zoning policy was gotten.By observing whether the delta time between them is greater than 0 or not,the suitability of zoning policies for picker-to-parts system were obtained.The significant effect of batch size b,zone number z and density d on suitability was also found by experimental study.The proposed research provides a new method for selection between sequential zoning and simultaneous zoning for picker-to-parts system,and improves the rationality and effi展开更多
C_(2)H_(2)semi-hydrogenation has been widely applied in industry to eliminate trace C_(2)H_(2)from C_(2)H_(4)feed.C_(2)H_(2)semi-hydrogenation to C_(2)H_(4)on a series of the newly designed catalysts,graphdiyne(GDY)as...C_(2)H_(2)semi-hydrogenation has been widely applied in industry to eliminate trace C_(2)H_(2)from C_(2)H_(4)feed.C_(2)H_(2)semi-hydrogenation to C_(2)H_(4)on a series of the newly designed catalysts,graphdiyne(GDY)as a new carbon allotrope supported different sizes of Pd_(x)M_(y)clusters(Pd_(x)M_(y)/GDY,M=Cu,Ag,Au,Ni;x+y=1-3),were studied using DFT calculations.The results found that C_(2)H_(2)semi-hydrogenation to C_(2)H_(4)on Pd_(x)M_(y)/GDY catalysts exhibits that both the activity and selectivity greatly depend on the composition and size of Pd_(x)M_(y)/GDY catalysts.Surprisingly,our results for the first time discovered the Pd_(1)/GDY catalyst with GDY supported the single atom Pd that presents the best selectivity and activity toward C_(2)H_(4)formation compared to the previously reported catalysts so far in C_(2)H_(2)semi-hydrogenation.This study would provide a theoretical clue for designing and screening out the potential catalysts with GDY supported small sizes of Pd_(x)M_(y)and other metal clusters in C_(2)H_(2)hydrogenation.展开更多
文摘Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for these systems remains a scientific challenge.In this work,copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity(up to 25.5%conversion and 66.8%selectivity)in the propylene-selective oxidation of acrolein at 300℃.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide(CuO)clusters into cuprous oxide(Cu2O)clusters.With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy(DB-FTIR),the allyl intermediate(CH2=CHCH2*)was clearly observed,along with the as-formed Cu2O species.The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process,and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene.
基金supported by the National Natural Science Foundation of China(21373167,21133004)the Program for Innovative Research Team in Chinese Universities(IRT_14R31)the Fundamental Research Funds of Central Universities~~
文摘When trinuclear molybdenum cluster compound with 'loose coordination site', Mo_3(μ_3-S)(μ-S)_3(μ-dtp)(dtp)_3·H_2O(A) (dtp=diethyldithiophos-phinato anion), is reacted with an excess of imidazole, the H_2O ligand and the bidentate bridging ligand μ-dtp are found to be simultaneously substituted by the imidazole to form the title compound. The title crystal belongs to the space group P(?), Z =2, with the following unit cell parameters: a=14.465(2), b=14.653(4), c=14.886(6), α=99.36(3),β=93.11(2),γ=114.29(2),V=2812(3). The crystalline compound consists of an ordered array of the cluster cation and dtp anion with acetone as packed molecule. The cation possesses a symmetry of C_3. Three Mo atoms form basically an equilateral triangle with three Mo—Mo bond lengths of 2.763 (1), 2.762(1), 2.756(1) respectively.
基金supported by National Natural Science Foundation of China (Grant No. 50175064)China Scholarship Council (Grant No. 2008622078)Material Handling Industry of America (Grant No. 12251)
文摘The existing research of sequential zoning system and simultaneous zoning system mainly focuses on some optimization problems such as workload balance,product assignment and simulation for each system separately.But there is little research on comparative study between sequential zoning and simultaneous zoning.In order to help the designers to choose the suitable zoning policy for picker-to-parts system reasonably and quickly,a systemic selection method is presented.Essentially,both zoning and batching are order clustering,so the customer order sheet can be divided into many unit grids.After the time formulation in one-dimensional unit was defined,the time models for each zoning policy in two-dimensional space were established using filling curves and sequence models to link the one-dimensional unit grids.In consideration of ＂U＂ shaped dual tour into consideration,the subtraction value of order picking time between sequential zoning and simultaneous zoning was defined as the objective function to select the suitable zoning policy based on time models.As it is convergent enough,genetic algorithm is adopted to find the optimal value of order picking time.In the experimental study,5 different kinds of order/stock keeping unit（SKU） matrices with different densities d and quantities q following uniform distribution were created in order to test the suitability of sequential zoning and simultaneous zoning to different kinds of orders.After parameters setting,experimental orders inputting and iterative computations,the optimal order picking time for each zoning policy was gotten.By observing whether the delta time between them is greater than 0 or not,the suitability of zoning policies for picker-to-parts system were obtained.The significant effect of batch size b,zone number z and density d on suitability was also found by experimental study.The proposed research provides a new method for selection between sequential zoning and simultaneous zoning for picker-to-parts system,and improves the rationality and effi
基金financially supported by the National Natural Science Foundation of China(No.21776193 and 21736007)U.S.NSF-sponsored NCAR-Wyoming Supercomputing Center(NWSC)。
文摘C_(2)H_(2)semi-hydrogenation has been widely applied in industry to eliminate trace C_(2)H_(2)from C_(2)H_(4)feed.C_(2)H_(2)semi-hydrogenation to C_(2)H_(4)on a series of the newly designed catalysts,graphdiyne(GDY)as a new carbon allotrope supported different sizes of Pd_(x)M_(y)clusters(Pd_(x)M_(y)/GDY,M=Cu,Ag,Au,Ni;x+y=1-3),were studied using DFT calculations.The results found that C_(2)H_(2)semi-hydrogenation to C_(2)H_(4)on Pd_(x)M_(y)/GDY catalysts exhibits that both the activity and selectivity greatly depend on the composition and size of Pd_(x)M_(y)/GDY catalysts.Surprisingly,our results for the first time discovered the Pd_(1)/GDY catalyst with GDY supported the single atom Pd that presents the best selectivity and activity toward C_(2)H_(4)formation compared to the previously reported catalysts so far in C_(2)H_(2)semi-hydrogenation.This study would provide a theoretical clue for designing and screening out the potential catalysts with GDY supported small sizes of Pd_(x)M_(y)and other metal clusters in C_(2)H_(2)hydrogenation.
