Surface properties of a catalyst, especially exposed crystal facets and coordination states, directly affect the catalyst's performance. Herein, we illustrate how reaction conditions direct the fabrication of a we...Surface properties of a catalyst, especially exposed crystal facets and coordination states, directly affect the catalyst's performance. Herein, we illustrate how reaction conditions direct the fabrication of a wellbehaved catalyst with desired structures in the case of hydrogen evolution reaction(HER). Stable adsorbed PtClxions on CNTs are in situ electrochemically reduced into a unique Pt nanosheet structure enclosed by high-index(311) and low-index(200) and(111) facets during HER process. Experimental results and density functional theory(DFT) calculation disclose the function mechanism between these unique structures and reactants. The adsorbed H2 O and reactive species act as capping agents protecting the(311) facet where the dissociation of water molecule is promoted, and the produced H*intermediates favorably combine and release on the nearby low-index Pt sites. The joint collaborations of these active sites afford Pt nanosheets comparable activity to 20 wt% Pt/C and a 12.7-fold over mass activity. These findings provide novel insight into the synthesis of heterogeneous catalysts with high specificity.展开更多
In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric aci...In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric acid solutions. The effect of six process variables, including the mass ratio of ferrous sulfate heptahydrate to pyrolusite, mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio, current density, leaching temperature, and leaching time, as well as their binary interactions, were modeled. The results revealed that the order of these factors with respect to their effects on the leaching efficiency were mass ratio of ferrous sulfate heptahydrate to pyrolusite 〉 leaching time 〉 mass ratio of sulfuric acid to pyrolusite 〉 liquid-to-solid ratio 〉 leaching temperature 〉 current density. The optimum conditions were as follows: 1.10:1 mass ratio of ferrous sulfate heptahydrate to pyrolusite, 0.9:1 mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio of 0.7:1, current density of 947 A/m^2, leaching time of 180 min, and leaching temperature of 73°C. Under these conditions, the predicted leaching efficiency for Mn was 94.1%; the obtained experimental result was 95.7%, which confirmed the validity of the model.展开更多
Promoted by various reductants,the addition of 1-iodo-4-chloro- perfluorobutane to 1-hexene giving 1:1 adduct is reported.Based on these facts,several new redox systems are proposed.
Ultrastable Y zeolite(USY)-supported Pt catalyst was prepared by gas-bubbling-assisted membrane reduction. The influence of reaction conditions and the metal and acid sites of catalysts on the catalytic performance ...Ultrastable Y zeolite(USY)-supported Pt catalyst was prepared by gas-bubbling-assisted membrane reduction. The influence of reaction conditions and the metal and acid sites of catalysts on the catalytic performance of catalyst in hydrogenation and selective ring opening of tetralin, 1,2,3,4-tetrahydronaphthalene(THN), was studied. It was found that the optimal reaction conditions were at a temperature of 280 °C, hydrogen pressure of 4 MPa, liquid hourly space velocity of 2 h^-1 and H2/THN ratio of 750. Under these optimal conditions, a high conversion of almost 100% was achieved on the 0.3 Pt/USY catalyst. XRD patterns and TEM images revealed that Pt particles were highly dispersed on the USY, favorable to the hydrogenation reaction of tetralin. Ammonia temperature-programmed desorption and Py-IR results indicated that the introduction of Pt can reduce the acid sites of USY, particularly the strong acid sites of USY. Thus, the hydrocracking reaction can be suppressed.展开更多
An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using(NH_4)_2SO_4. The optimized reaction conditions are defined as an(NH_4)_2SO_4/zinc molar ratio of 1.4:1, a roasting ...An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using(NH_4)_2SO_4. The optimized reaction conditions are defined as an(NH_4)_2SO_4/zinc molar ratio of 1.4:1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of(NH_4)_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for(NH_4)_2SO_4 and zinc mixed in a molar ratio of 1.4:1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.展开更多
An operando dual‐beam Fourier transform infrared (DB‐FTIR) spectrometer was successfully developed using a facile method. The DB‐FTIR spectrometer is suitable for the real‐time study of the dynamic surface process...An operando dual‐beam Fourier transform infrared (DB‐FTIR) spectrometer was successfully developed using a facile method. The DB‐FTIR spectrometer is suitable for the real‐time study of the dynamic surface processes involved in gas/solid heterogeneous catalysis under real reaction conditionsbecause it can simultaneously collect reference and sample spectra. The influence of gas‐phasemolecular vibration and heat irradiation at real reaction temperatures can therefore be eliminated.The DB‐FTIR spectrometer was successfully used to follow the transformation of isobutene over nano‐sized HZSM‐5 zeolite under real reaction conditions.展开更多
With Portulaca oleracea L. as an experimental material, its total DNA was extracted by the improved CTAB method, the ISSR-PCR primers were screened, and the ISSR-PCR reaction system and reaction conditions for P. oler...With Portulaca oleracea L. as an experimental material, its total DNA was extracted by the improved CTAB method, the ISSR-PCR primers were screened, and the ISSR-PCR reaction system and reaction conditions for P. oleracea were Optimized. The results showed that there were 8 primers suitable for ISSR-PCR of P. oleracea. The optimal reaction system had a volume of 25 μl, including 2 x Taq Platinum PCR Master Mix 12.5 μl, primer 2 μl, ddH20 9.5 μl, and DNA template 1μl. The optimized ISSR-PCR of P. oleracea was started with pre-denaturation at 94 ℃ for 360 s, followed by 30 cycles of denaturation at 94 ℃ for 60 s, annealing at 54 ℃ for 60 s and extension at 72 ℃ for 90 s, and completed by extension at 72 ℃ for 300 s.展开更多
1-Aryl-2-merhy1-4,5-dihydropyrro1-3-carboxylic acid ethyl ester was observed to dehydrogenate to give 1-ary1-2-methyl-pyrro1-3-carboxylic acid ethyl ester upon irradiation in the presence of oxygen and in the presence...1-Aryl-2-merhy1-4,5-dihydropyrro1-3-carboxylic acid ethyl ester was observed to dehydrogenate to give 1-ary1-2-methyl-pyrro1-3-carboxylic acid ethyl ester upon irradiation in the presence of oxygen and in the presence or absence of ms-tetraphenylporphine.展开更多
This study deals with the stagnation point flow of ferrofluid over a flat plate with non-linear slip boundary condition in the presence of homogeneous-heterogeneous reactions.Three kinds of ferroparticles,namely,magne...This study deals with the stagnation point flow of ferrofluid over a flat plate with non-linear slip boundary condition in the presence of homogeneous-heterogeneous reactions.Three kinds of ferroparticles,namely,magnetite(Fe_3O_4),cobalt ferrite(CoFe_2O_4) and manganese zinc ferrite(Mn-ZnFe_2O_4) are taken into account with water and kerosene as conventional base fluids.The developed model of homogeneous-heterogeneous reactions in boundary layer flow with equal and unequal diffusivities for reactant and autocatalysis is considered.The governing partial differential equations are converted into system of non-linear ordinary differential equations by mean of similarity transformations.These ordinary differential equations are integrated numerically using shooting method.The effects of pertinent parameters on velocity and concentration profiles are presented graphically and discussed.We found that in the presence of Fe_3O_4-kerosene and CoFe_2O_4-kerosene,velocity profiles increase for large values of α and β whereas there is a decrement in concentration profiles with increasing values of if and K_s.Furthermore,the comparison between non-magnetic(A1_2O_3) and magnetic Fe_3O_4 nanoparticles is given in tabular form.展开更多
Alcohols are selectively and efficiently protected as their tetrahydropranyl ethers in the presence of a catalytic amount of Fe(HSO4)3 in good to high yields. All reactions are performed under mild and completely he...Alcohols are selectively and efficiently protected as their tetrahydropranyl ethers in the presence of a catalytic amount of Fe(HSO4)3 in good to high yields. All reactions are performed under mild and completely heterogeneous reaction conditions.展开更多
China experienced worsening ground-level ozone(O_(2)) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature(T_(2)), solar radiation(SW), and wind speed(WS), were classifi...China experienced worsening ground-level ozone(O_(2)) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature(T_(2)), solar radiation(SW), and wind speed(WS), were classified into two aspects,(1) Photochemical Reaction Condition(PRC = T_(2)× SW) and(2) Physical Dispersion Capacity(PDC = WS). In this way, a Meteorology Synthetic Index(MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O_(2)pollution. The positive linear relationship between the 90 th percentile of MDA8(maximum daily 8-h average) O_(2)concentration and MSI determined that the contribution of meteorological changes to ground-level O-3 varied on a latitudinal gradient, decreasing from ~40% in southern China to 10%–20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O_(2)pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O_(2)variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies.展开更多
Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cy...Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the variations achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the volume fraction of the outlet CO_(2)remained more than 92%under the oxygen carriers.The optimized reaction conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min^(-1).When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH_(3)and-CH_(2),and CO and H_(2)were largely generated from the gasification of aromatic carbon.In the CLC process,H_(2)O and CO_(2)began to separate out at 270℃,CH4 and tar began to precipitate at 370℃,and the amount of CO_(2)was continuously elevated with the rise of the temperature.展开更多
Oxathioacetalyzation of carbonyl compounds with 2-mercaptoethanol and deprotection of the obtained 1,3-oxathiolanes is easily performed in the presence of silica sulfuric acid (SSA). All reactions were performed und...Oxathioacetalyzation of carbonyl compounds with 2-mercaptoethanol and deprotection of the obtained 1,3-oxathiolanes is easily performed in the presence of silica sulfuric acid (SSA). All reactions were performed under mild and completely heterogeneous reaction conditions in good to high yields.展开更多
The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O...The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species (-CH2-). Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity (GHSV), and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.展开更多
Ethylidene diacetate was prepared by reacting dimethyl ether,acetic acid and syngas in the presence of a catalytic system comprising RhI3,PPh3 and CH3I.The effects of reaction temperature,pressure,time and the CO/H2 m...Ethylidene diacetate was prepared by reacting dimethyl ether,acetic acid and syngas in the presence of a catalytic system comprising RhI3,PPh3 and CH3I.The effects of reaction temperature,pressure,time and the CO/H2 molar ratio on the conversion of dimethyl ether and the product selectivity were investigated under the same catalyst formulation.Results showed that a maximum conversion of dimethyl ether was obtained when a mixture consisting of 0.3 mol dimethyl ether and 120 ml acetic acid was reacted at 180 ℃ and 3.0 MPa for 10 h at a stirring speed of 600 rpm under a syngas flow with a CO/H2 molar ratio of 2.5,which was catalyzed by a catalyst mixture comprising 0.3 g RhI3,6 g PPh3 and 1.3 g CH3I.The selectivity of ethylidene diacetate increased with temperature,decreased with the CO/H2 molar ratio and exhibited a maximum with pressure.展开更多
Michael addition of active methylene compounds to α,β-unsaturated carboxylic esters and nitriles was effectively catalyzed by a basic ionic liquid, 1-butyl-3-methylimidazolium acetate([Bmim]OAc). The his-addition ...Michael addition of active methylene compounds to α,β-unsaturated carboxylic esters and nitriles was effectively catalyzed by a basic ionic liquid, 1-butyl-3-methylimidazolium acetate([Bmim]OAc). The his-addition products were selectively obtained in high yields under mild reaction conditions.展开更多
Silica triflate, as a new silica-based reagent, can be used for the efficient synthesis of 4-substituted coumarins via a Pechmann reaction under solvent-free reaction conditions. All reactions were performed at 80 ℃ ...Silica triflate, as a new silica-based reagent, can be used for the efficient synthesis of 4-substituted coumarins via a Pechmann reaction under solvent-free reaction conditions. All reactions were performed at 80 ℃ in good to high yields.展开更多
Acetic anhydride is the important organic chemical raw material, and is used widely in chemical industry,pharmaceutical industry, dyes, spices and other fields. In this paper, the process of carbonylation of methyl ac...Acetic anhydride is the important organic chemical raw material, and is used widely in chemical industry,pharmaceutical industry, dyes, spices and other fields. In this paper, the process of carbonylation of methyl acetate in rhodium iodine catalyst system was studied, and the suitable reaction conditions were determined.At the same time, the kinetic model was established. The optimum reaction conditions were as follows: the reaction pressure was 5 MPa, the hydrogen content was 8%, the amount of iodomethane was 15%, the amount of lithium iodide was 3%, the reaction temperature was 150 ℃ and the reaction time is 3 h. Under the above reaction conditions, the selectivity of the reaction is close to 100% and the conversion is as high as 92%. The macroscopic kinetic model of the reaction was established in the temperature range of 120 ℃–150 ℃. The reaction is an irreversible reaction without the formation of by-products and the dynamic equation is also given in the Conclusions section.展开更多
A mild and efficient method for the conversion of alcohols to their corresponding methoxymethyl ethers and acetates using benzyltriphenylphosphonium tribromide (BTPTB) as catalyst is described. All reactions were pe...A mild and efficient method for the conversion of alcohols to their corresponding methoxymethyl ethers and acetates using benzyltriphenylphosphonium tribromide (BTPTB) as catalyst is described. All reactions were performed under completely heterogeneous reaction conditions in good to high yields.展开更多
The process of synthesis of dimethyl-2,6-naphthalene dicaboxylate from esterification of 2,6-naphthalene dicarboxylic acid (2,6-NDCA) by methanol using sodium tungstate as catalyst was investigated. The orthogonal tes...The process of synthesis of dimethyl-2,6-naphthalene dicaboxylate from esterification of 2,6-naphthalene dicarboxylic acid (2,6-NDCA) by methanol using sodium tungstate as catalyst was investigated. The orthogonal tests method was used for optimizing the process factors. The effects of reaction temperature, mass percentage of catalyst, reaction time and mass ratio of methanol to 2,6-NDCA on the 2,6-NDCA conversion were investigated. It was found that all the four factors had significant effect on the conversion. The optimum reaction conditions were reaction temperature 215 ℃,mass percentage of catalyst 3%, reaction time 3 h, mass ratio of methanol to 2,6-NDCA 6∶1. The 2,6-NDCA conversion at above condition was 92.80%.展开更多
基金Financial supports from the Key Program Supported by the Natural Science Foundation of Zhejiang Province, China (LZ18B060002)the National Natural Science Foundation of China (21802120, 21872121)。
文摘Surface properties of a catalyst, especially exposed crystal facets and coordination states, directly affect the catalyst's performance. Herein, we illustrate how reaction conditions direct the fabrication of a wellbehaved catalyst with desired structures in the case of hydrogen evolution reaction(HER). Stable adsorbed PtClxions on CNTs are in situ electrochemically reduced into a unique Pt nanosheet structure enclosed by high-index(311) and low-index(200) and(111) facets during HER process. Experimental results and density functional theory(DFT) calculation disclose the function mechanism between these unique structures and reactants. The adsorbed H2 O and reactive species act as capping agents protecting the(311) facet where the dissociation of water molecule is promoted, and the produced H*intermediates favorably combine and release on the nearby low-index Pt sites. The joint collaborations of these active sites afford Pt nanosheets comparable activity to 20 wt% Pt/C and a 12.7-fold over mass activity. These findings provide novel insight into the synthesis of heterogeneous catalysts with high specificity.
基金financially supported by the "121" Scientific and Technological Supporting Demonstration Project of Chongqing, China (No. cstc2014zktjccx B0043)the Scientific Research and Technology Development Program of Guangxi, China (No. 2014BA10016)
文摘In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric acid solutions. The effect of six process variables, including the mass ratio of ferrous sulfate heptahydrate to pyrolusite, mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio, current density, leaching temperature, and leaching time, as well as their binary interactions, were modeled. The results revealed that the order of these factors with respect to their effects on the leaching efficiency were mass ratio of ferrous sulfate heptahydrate to pyrolusite 〉 leaching time 〉 mass ratio of sulfuric acid to pyrolusite 〉 liquid-to-solid ratio 〉 leaching temperature 〉 current density. The optimum conditions were as follows: 1.10:1 mass ratio of ferrous sulfate heptahydrate to pyrolusite, 0.9:1 mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio of 0.7:1, current density of 947 A/m^2, leaching time of 180 min, and leaching temperature of 73°C. Under these conditions, the predicted leaching efficiency for Mn was 94.1%; the obtained experimental result was 95.7%, which confirmed the validity of the model.
文摘Promoted by various reductants,the addition of 1-iodo-4-chloro- perfluorobutane to 1-hexene giving 1:1 adduct is reported.Based on these facts,several new redox systems are proposed.
基金the National Natural Science Foundation of China (U1662103 and 21673290)the National HiTech Research and Development Program (863) of China (2015AA034603)the China National Offshore Oil Corporation Fund (LHYJYKJSA20160002)
文摘Ultrastable Y zeolite(USY)-supported Pt catalyst was prepared by gas-bubbling-assisted membrane reduction. The influence of reaction conditions and the metal and acid sites of catalysts on the catalytic performance of catalyst in hydrogenation and selective ring opening of tetralin, 1,2,3,4-tetrahydronaphthalene(THN), was studied. It was found that the optimal reaction conditions were at a temperature of 280 °C, hydrogen pressure of 4 MPa, liquid hourly space velocity of 2 h^-1 and H2/THN ratio of 750. Under these optimal conditions, a high conversion of almost 100% was achieved on the 0.3 Pt/USY catalyst. XRD patterns and TEM images revealed that Pt particles were highly dispersed on the USY, favorable to the hydrogenation reaction of tetralin. Ammonia temperature-programmed desorption and Py-IR results indicated that the introduction of Pt can reduce the acid sites of USY, particularly the strong acid sites of USY. Thus, the hydrocracking reaction can be suppressed.
基金financially supported by the National Natural Science Foundation of China(Nos.51204054 and 51574084)the Fundamental Research Funds for the Central Universities of China(No.N150204009)the National Basic Research Priorities Program of China(No.2014CB643405)
文摘An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using(NH_4)_2SO_4. The optimized reaction conditions are defined as an(NH_4)_2SO_4/zinc molar ratio of 1.4:1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of(NH_4)_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for(NH_4)_2SO_4 and zinc mixed in a molar ratio of 1.4:1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.
基金supported by the National Natural Science Foundation of China (21603023)the PetroChina Innovation Foundation, China (2014D-5006-0501)~~
文摘An operando dual‐beam Fourier transform infrared (DB‐FTIR) spectrometer was successfully developed using a facile method. The DB‐FTIR spectrometer is suitable for the real‐time study of the dynamic surface processes involved in gas/solid heterogeneous catalysis under real reaction conditionsbecause it can simultaneously collect reference and sample spectra. The influence of gas‐phasemolecular vibration and heat irradiation at real reaction temperatures can therefore be eliminated.The DB‐FTIR spectrometer was successfully used to follow the transformation of isobutene over nano‐sized HZSM‐5 zeolite under real reaction conditions.
文摘With Portulaca oleracea L. as an experimental material, its total DNA was extracted by the improved CTAB method, the ISSR-PCR primers were screened, and the ISSR-PCR reaction system and reaction conditions for P. oleracea were Optimized. The results showed that there were 8 primers suitable for ISSR-PCR of P. oleracea. The optimal reaction system had a volume of 25 μl, including 2 x Taq Platinum PCR Master Mix 12.5 μl, primer 2 μl, ddH20 9.5 μl, and DNA template 1μl. The optimized ISSR-PCR of P. oleracea was started with pre-denaturation at 94 ℃ for 360 s, followed by 30 cycles of denaturation at 94 ℃ for 60 s, annealing at 54 ℃ for 60 s and extension at 72 ℃ for 90 s, and completed by extension at 72 ℃ for 300 s.
文摘1-Aryl-2-merhy1-4,5-dihydropyrro1-3-carboxylic acid ethyl ester was observed to dehydrogenate to give 1-ary1-2-methyl-pyrro1-3-carboxylic acid ethyl ester upon irradiation in the presence of oxygen and in the presence or absence of ms-tetraphenylporphine.
文摘This study deals with the stagnation point flow of ferrofluid over a flat plate with non-linear slip boundary condition in the presence of homogeneous-heterogeneous reactions.Three kinds of ferroparticles,namely,magnetite(Fe_3O_4),cobalt ferrite(CoFe_2O_4) and manganese zinc ferrite(Mn-ZnFe_2O_4) are taken into account with water and kerosene as conventional base fluids.The developed model of homogeneous-heterogeneous reactions in boundary layer flow with equal and unequal diffusivities for reactant and autocatalysis is considered.The governing partial differential equations are converted into system of non-linear ordinary differential equations by mean of similarity transformations.These ordinary differential equations are integrated numerically using shooting method.The effects of pertinent parameters on velocity and concentration profiles are presented graphically and discussed.We found that in the presence of Fe_3O_4-kerosene and CoFe_2O_4-kerosene,velocity profiles increase for large values of α and β whereas there is a decrement in concentration profiles with increasing values of if and K_s.Furthermore,the comparison between non-magnetic(A1_2O_3) and magnetic Fe_3O_4 nanoparticles is given in tabular form.
文摘Alcohols are selectively and efficiently protected as their tetrahydropranyl ethers in the presence of a catalytic amount of Fe(HSO4)3 in good to high yields. All reactions are performed under mild and completely heterogeneous reaction conditions.
基金supported by the National Key Research and Development Plan(Grant No.2017YFC0210105)the second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0604)+7 种基金the National Natural Science Foundation of China(Grant Nos.41905086,41905107,42077205,and 41425020)the Special Fund Project for Science and Technology Innovation Strategy of Guangdong Province(Grant No.2019B121205004)the China Postdoctoral Science Foundation(Grant No.2020M683174)the Air Quip(High-resolution Air Quality Information for Policy)Project funded by the Research Council of Norwaythe Collaborative Innovation Center of Climate ChangeJiangsu ProvinceChinathe high-performance computing platform of Jinan University。
文摘China experienced worsening ground-level ozone(O_(2)) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature(T_(2)), solar radiation(SW), and wind speed(WS), were classified into two aspects,(1) Photochemical Reaction Condition(PRC = T_(2)× SW) and(2) Physical Dispersion Capacity(PDC = WS). In this way, a Meteorology Synthetic Index(MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O_(2)pollution. The positive linear relationship between the 90 th percentile of MDA8(maximum daily 8-h average) O_(2)concentration and MSI determined that the contribution of meteorological changes to ground-level O-3 varied on a latitudinal gradient, decreasing from ~40% in southern China to 10%–20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O_(2)pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O_(2)variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies.
基金support from the National Key Research and Development Program of China(2018YFB06050401)Key Research and Development Program of the Ningxia Hui Autonomous Region(2018BCE01002)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(2019-KF30,2019-KF33)。
文摘Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the variations achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the volume fraction of the outlet CO_(2)remained more than 92%under the oxygen carriers.The optimized reaction conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min^(-1).When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH_(3)and-CH_(2),and CO and H_(2)were largely generated from the gasification of aromatic carbon.In the CLC process,H_(2)O and CO_(2)began to separate out at 270℃,CH4 and tar began to precipitate at 370℃,and the amount of CO_(2)was continuously elevated with the rise of the temperature.
文摘Oxathioacetalyzation of carbonyl compounds with 2-mercaptoethanol and deprotection of the obtained 1,3-oxathiolanes is easily performed in the presence of silica sulfuric acid (SSA). All reactions were performed under mild and completely heterogeneous reaction conditions in good to high yields.
基金the National Key Project for Basic Research of China(973 Project)(No.2005CB221402)the China National Petroleum Corporation.
文摘The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species (-CH2-). Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity (GHSV), and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.
文摘Ethylidene diacetate was prepared by reacting dimethyl ether,acetic acid and syngas in the presence of a catalytic system comprising RhI3,PPh3 and CH3I.The effects of reaction temperature,pressure,time and the CO/H2 molar ratio on the conversion of dimethyl ether and the product selectivity were investigated under the same catalyst formulation.Results showed that a maximum conversion of dimethyl ether was obtained when a mixture consisting of 0.3 mol dimethyl ether and 120 ml acetic acid was reacted at 180 ℃ and 3.0 MPa for 10 h at a stirring speed of 600 rpm under a syngas flow with a CO/H2 molar ratio of 2.5,which was catalyzed by a catalyst mixture comprising 0.3 g RhI3,6 g PPh3 and 1.3 g CH3I.The selectivity of ethylidene diacetate increased with temperature,decreased with the CO/H2 molar ratio and exhibited a maximum with pressure.
基金Supported by the National Natural Science Foundation of China(Nos.20533010 and 20873041)Shanghai Leading Academic Discipline Project,China(No.B409)
文摘Michael addition of active methylene compounds to α,β-unsaturated carboxylic esters and nitriles was effectively catalyzed by a basic ionic liquid, 1-butyl-3-methylimidazolium acetate([Bmim]OAc). The his-addition products were selectively obtained in high yields under mild reaction conditions.
文摘Silica triflate, as a new silica-based reagent, can be used for the efficient synthesis of 4-substituted coumarins via a Pechmann reaction under solvent-free reaction conditions. All reactions were performed at 80 ℃ in good to high yields.
文摘Acetic anhydride is the important organic chemical raw material, and is used widely in chemical industry,pharmaceutical industry, dyes, spices and other fields. In this paper, the process of carbonylation of methyl acetate in rhodium iodine catalyst system was studied, and the suitable reaction conditions were determined.At the same time, the kinetic model was established. The optimum reaction conditions were as follows: the reaction pressure was 5 MPa, the hydrogen content was 8%, the amount of iodomethane was 15%, the amount of lithium iodide was 3%, the reaction temperature was 150 ℃ and the reaction time is 3 h. Under the above reaction conditions, the selectivity of the reaction is close to 100% and the conversion is as high as 92%. The macroscopic kinetic model of the reaction was established in the temperature range of 120 ℃–150 ℃. The reaction is an irreversible reaction without the formation of by-products and the dynamic equation is also given in the Conclusions section.
文摘A mild and efficient method for the conversion of alcohols to their corresponding methoxymethyl ethers and acetates using benzyltriphenylphosphonium tribromide (BTPTB) as catalyst is described. All reactions were performed under completely heterogeneous reaction conditions in good to high yields.
文摘The process of synthesis of dimethyl-2,6-naphthalene dicaboxylate from esterification of 2,6-naphthalene dicarboxylic acid (2,6-NDCA) by methanol using sodium tungstate as catalyst was investigated. The orthogonal tests method was used for optimizing the process factors. The effects of reaction temperature, mass percentage of catalyst, reaction time and mass ratio of methanol to 2,6-NDCA on the 2,6-NDCA conversion were investigated. It was found that all the four factors had significant effect on the conversion. The optimum reaction conditions were reaction temperature 215 ℃,mass percentage of catalyst 3%, reaction time 3 h, mass ratio of methanol to 2,6-NDCA 6∶1. The 2,6-NDCA conversion at above condition was 92.80%.