An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200℃ for 10-120 min. T...An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200℃ for 10-120 min. The reduced samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chemical analysis. A good degree of metallization and reduction was achieved. Gas diffusion through the solid was identified as the reaction-rate-controlling resistance; however, during the initial period, particularly at lower temperatures, resistance to interfacial chemical reaction was also significant, though not dominant. The apparent rate constant was observed to increase marginally with decreasing size of the particles constituting the nuggets. The apparent activation energy of reduction was estimated to be in the range from 49.640 to 51.220 kJ/mol and was not observed to be affected by the particle size. The sulfur and carbon contents in the reduced samples were also determined.展开更多
Based on the quantum chemical study of the silylidyne insertion reaction with NH3 or PH3, the general statistical thermodynamics and Eyring transition state theory with Wigner correction are used to compute the change...Based on the quantum chemical study of the silylidyne insertion reaction with NH3 or PH3, the general statistical thermodynamics and Eyring transition state theory with Wigner correction are used to compute the changes of thermodynamic functions, equilibrium constants, A factors and rate constants of the two reactions in the temperature range 200-2000K. The results show that both of these reactions are thermodynamically dominant at low temperatures and kinetically favored at higher temperatures. The comparison between these two reactions shows that the SiH reaction with NH3 is more exothermic than SiH with PH3, while the rate constant of SiH reaction with NH3 is lower than that of SiH with PH3 at the same temperature.展开更多
A green environmental protection and enhanced leaching process was proposed to recover all elements from spent lithium iron phosphate(LiFePO_(4)) lithium batteries.In order to reduce the influence of Al impurity in th...A green environmental protection and enhanced leaching process was proposed to recover all elements from spent lithium iron phosphate(LiFePO_(4)) lithium batteries.In order to reduce the influence of Al impurity in the recovery process,NaOH was used to remove impurity.After impurity removal,the spent LiFePO_(4) cathode material was used as raw material under the H_(2)SO_(4) system,and the pressure oxidation leaching process was adopted to achieve the preferential leaching of lithium.The E-pH diagram of the Fe-P-Al-H_(2)O system can determine the stable region of each element in the recovery process of spent LiFePO_(4)Li-batteries.Under the optimal conditions(500 r·min^(-1),15 h,363.15 K,0.4 MPa,the liquid-solid ratio was 4:1 ml·g^(-1)and the acid-material ratio was 0.29),the leaching rate of Li was 99.24%,Fe,Al,and Ti were 0.10%,2.07%,and 0.03%,respectively.The Fe and P were precipitated and recovered as FePO_(4)·2H_(2)O.The kinetic analysis shows that the process of high-pressure acid leaching of spent LiFePO_(4) materials depends on the surface chemical reaction.Through the life cycle assessment(LCA)of the spent LiFePO_(4) whole recovery process,eight midpoint impact categories were selected to assess the impact of recovery process.The results can provide basic environmental information on production process for recycling industry.展开更多
An efficient culture medium producing a bacterial elastase with high yields was developed further following preliminary studies by means of response surface method. Central composite design (CCD) and response surface ...An efficient culture medium producing a bacterial elastase with high yields was developed further following preliminary studies by means of response surface method. Central composite design (CCD) and response surface method-ology were applied to optimize the medium constituents. A central composite design was used to explain the combined effect of three medium constituents, viz, glucose, K2HPO4, MgSO47H2O. The strain produced more elastase in the completely optimized medium, as compared with the partially optimized medium. The fitted model of the second model, as per RSM, showed that glucose was 7.4 g/100 ml, casein 1.13 g/100 ml, corn steep flour 0.616 g/100 ml, K2HPO4 0.206 g/100 ml and MgSO47H2O 0.034 g/100 ml. The fermentation kinetics of these two culture media in the flask experiments were analyzed. It was found that the highest elastase productivity occurred at 54 hours. Higher glucose concentration had inhibitory effect on elastase production. At the same time, we observed that the glucose consumption rate was slow in the completely optimized medium, which can explain the lag period of the highest elastase production. Some metal ions and surfactant additives also affected elastase production and cell growth.展开更多
The catalytic activity for the synthesis of methanol from carbon dioxide and hydrogen was measured on various binary and ternary catalysts containing copper oxide under a pressure of 10 atm. Among these samples the ca...The catalytic activity for the synthesis of methanol from carbon dioxide and hydrogen was measured on various binary and ternary catalysts containing copper oxide under a pressure of 10 atm. Among these samples the catalysts, CuO/ZnO/γ-Al_2O_3, demonstrated the highest activity and selectivity to methanol; MnO, as third component, had no promotional effect on the activity of meth- anol formation. Based on a simple power rate law the apparent activation energy estimation and par- tial pressure dependence measurement were accomplished over eight catalysts. The activation energies varied from 40 to 120 kJ / mol depending on the composition of catalysts. The rates of methanol for- mation to be 0.3 -- 0.9 order in H_2 and about 0.1 -- 0.2 order in CO_2 were reported.展开更多
Kinetic studies of the singlet oxygenation of the title compounds were performed accord- ing to Monroe's method. The reaction rate increases with temperature decreasing, leading to a ne- gative activation enthalpy...Kinetic studies of the singlet oxygenation of the title compounds were performed accord- ing to Monroe's method. The reaction rate increases with temperature decreasing, leading to a ne- gative activation enthalpy and a large negative activation entropy. These data are interpreted as the evidence for the intermediacy of an exciplex. The solvent effect on the reaction rate suggests that the “dioxetane” path involves a transition state or an intermediate with significant zwitterionic character. The electronic effect of the substituent is obvious, with electron-withdrawing substituent retarding the reaction and electron-donating substituent increasing the reaction rate. However, steric bulkiness at the 6-position does not play an important role in the reaction rate.展开更多
The laser-induced optical fiber fluorimetry has been used for the first time to analyse the concentration of uranium(VI) in the kinetic studies on the extraction of uranium(VI) between 0.5 mol/L H_3PO_4 solution and H...The laser-induced optical fiber fluorimetry has been used for the first time to analyse the concentration of uranium(VI) in the kinetic studies on the extraction of uranium(VI) between 0.5 mol/L H_3PO_4 solution and HDEHP-cyclohexane system with Lewis cell. The effects of stirring speed, temper- ature and concentration of uranium(VI) and HDEHP on the rate of extraction were examined. These data show that the extraction rate of uranium(VI) in this system is controlled by the chemical reaction process at the interface. The rate equations and the rate constants of the forward and reverse ex- tractions were obtained. The mechanism of the extraction has been discussed.展开更多
Adsorption-desorption kinetics of CO and H_2 on Ni surface were studied with molecular beam relaxation spectrometry. It is found that there are two adsorbed states in the substrate temperature range 330K<T<480K ...Adsorption-desorption kinetics of CO and H_2 on Ni surface were studied with molecular beam relaxation spectrometry. It is found that there are two adsorbed states in the substrate temperature range 330K<T<480K and 720K<T<900K respectively for CO/Ni system. These results can be explained by a precursor state model. Their kinetic parameters: E_(aα)=14.6kJ/mol, E_(dx)=49.3kJ/mol; E_(aβ)= 68.6kJ/mol, E_(dβ)=200.6kJ/mol. It is shown that there are two adsorbed states in the low (350K<T<430K) and high (550K<T<625K) temperature range respectively for H_2/Ni system. These results can be explained by a direct dissociative model. Their kinetic parameters:E_(dl)=26.3kJ/mol, E_(dh)=103.7kJ/mol.展开更多
It is found that acetoacetanilide possesses very high promoting reactivity towards ceric ion in initiating polymerization of vinyl monomer. The kinetics of acrylamide polymerization and the activation energies were st...It is found that acetoacetanilide possesses very high promoting reactivity towards ceric ion in initiating polymerization of vinyl monomer. The kinetics of acrylamide polymerization and the activation energies were studied. The initiation mechanism of ceric/acetoacetanilide is proposed on the basis of experimental results of FT-IR and ESR.展开更多
In the present investigation,a microbial consortium consisting of four bacterial strains was selected for the treatment of pharmaceutical industry wa stewater.The consortium was immobilized on a natural support matrix...In the present investigation,a microbial consortium consisting of four bacterial strains was selected for the treatment of pharmaceutical industry wa stewater.The consortium was immobilized on a natural support matrixLuffa and used for the treatment of real-time pharmaceutical wastewater in batch and continuous processes.The batch process was carried out to optimize the culture conditions and monitor the enzymatic activity.An array of enzymes such as alcohol dehydrogenase,aldehyde dehydrogenase,monooxygenase,catechol 2,3-dioxygenase and hydroquinol 1,2-dioxygenase were produced by the consortium.The kinetics of the degradation in the batch process was analyzed and it was noted to be a first-order reaction.For the continuous study,an aerobic fixed-film bioreactor(AFFBR) was utilized for a period of 61 days with variable hydraulic retention time(HRT) and organic loading rate(OLR).The immobilized microbes treated the wastewater by reducing the COD,phenolic contaminants and suspended solids.The OLR ranged between(0.56±0.05) kg COD·m^(-3) d^(-1) to 3.35 kg COD·m^(-3)·d^(-1) and the system achieved an average reduction of 96.8% of COD,92.6% of phenolic compounds and 95.2% of suspended solids.Kinetics of the continuous process was interpreted by three different models,where the modified Stover Kincannon model and the Grau second-order model proved to be best fit for the degradation reaction with the constant for saturation value,k_(L) being 95.12 g·L^(-1)·d^(-1).the constant for maximum utilization of the substrate U_(max) being 90.01 g·L^(-1) d^(-1) and substrate removal constant KY was1.074 d^(-1) for both the models.GC-MS analysis confirmed that most of the organic contaminants were degraded into innocuous metabolite s.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
In recent years,scientists have become increasingly concerned in recycling electronic trash,particularly waste printed circuit boards(WPCBs).Previous research has indicated that the presence of Cu impacts the pyrolysi...In recent years,scientists have become increasingly concerned in recycling electronic trash,particularly waste printed circuit boards(WPCBs).Previous research has indicated that the presence of Cu impacts the pyrolysis of WPCBs.However,there may be errors in the experimental results,as printed circuit boards(PCBs)with copper and those without copper are produced differently.For this experiment,we blended copper powder with PCB nonmetallic resin powder in various ratios to create the samples.The apparent kinetics and pyrolysis properties of four resin powders with varying copper concentrations were compared using nonisothermal thermogravimetric analysis(TG)and thermal pyrolysis-gas chromatography mass spectrometry(Py-GC/MS).From the perspective of kinetics,the apparent activation energy of the resin powder in the pyrolysis reaction shows a rise(0.1<a<0.2)-stable(0.2<a<0.4)-accelerated increase(0.4<a<0.8)-decrease(0.8<a<0.9)process.After adding copper powder,the apparent activation energy changes more obviously when(0.2<a<0.4).In the early stage of the pyrolysis reaction(0.1<a<0.6),the apparent activation energy is reduced,but when a?0.8,it is much higher than that of the resin sample without copper.Additionally,it is discovered using thermogravimetric analysis and Py-GC/MS that copper shortens the temperature range of the primary pyrolysis reaction and prevents the creation of compounds containing bromine.This inhibition will raise the temperature at which compounds containing bromine first form,and it will keep rising as the copper level rises.The majority of the circuit board molecules have lower bond energies when copper is present,according to calculations performed using the Gaussian09 software,which promotes the pyrolysis reaction.展开更多
A one-step sintering process of bauxite raw material from direct mining was completed, and the kinetics of this process was analyzed thoroughly. The results show that the sintering kinetics of bauxite raw material exh...A one-step sintering process of bauxite raw material from direct mining was completed, and the kinetics of this process was analyzed thoroughly. The results show that the sintering kinetics of bauxite raw material exhibits the liquid-phase sintering behavior. A small portion of impurities existed in the raw material act as a liquid phase. After X-ray diffraction analyses, scanning electron microscopy observations, and kinetics calculations, sintering temperature and heating duration were determined as the two major factors contributing to the sintering process and densification of bauxite ore. An elevated heating temperature and longer duration favor the densification process. The major obstacle for the densification of bauxite material is attributed to the formation of the enclosed blowhole during liquid-phase sintering.展开更多
The plasticizer is an important polymer material additive.Non-toxic and environmentally friendly plasticizers are developed recently in order to decrease fossil fuel reserves,serious environmental pollution and the to...The plasticizer is an important polymer material additive.Non-toxic and environmentally friendly plasticizers are developed recently in order to decrease fossil fuel reserves,serious environmental pollution and the toxicity of phthalate esters.In this study,a new,efficient and environmentally friendly plasticizer of hydrogenated rosin dodecyl ester was prepared by an esterification reaction of hydrogenated rosin and dodecanol.The influences of different reaction conditions(including different catalysts,the catalyst concentration,the ratio of the reactants,reaction temperature,and reaction time)on the esterification yield are examined and discussed.Hydrogenated rosin dodecyl ester with 71.8%yield was synthesized under the optimized reaction conditions(1:0.8 molar ratio of rosin to dodecanol,1 mol%tetrabutyl titanate concentration,and 210℃for 6 h).The esterification reaction is a second-order reaction,and kinetic calculations showed that the activation energy is 39.77 KJ·mol^(−1).The structure of the hydrogenated rosin dodecyl ester was confirmed by FT-IR spectroscopy and^(13)C NMR spectrum.Besides,the thermal stability of target product(hydrogenated rosin dodecyl ester)was also tested by thermal gravimetric analysis(TGA),which showed a good thermal stability.展开更多
Mevinolin is one of the earlier statin drugs which is effective for the treatment of hypercholesterolemia, as an inhibitor of the HMG-CoA reductase. The transformations of mevinolin in acidic alcohol( such as ethanol...Mevinolin is one of the earlier statin drugs which is effective for the treatment of hypercholesterolemia, as an inhibitor of the HMG-CoA reductase. The transformations of mevinolin in acidic alcohol( such as ethanol, methanol and isopropanol) solutions caused by solvent effects were revealed in the present article. The solvates, that is, mevinolinic methyl ester, mevinolinic ethyl ester and mevinolinic isopropyl ester, were identified by LC/PDA and LC/MS. The kinetics parameters of the transformations caused by solvent effects, such as the observed rate constant of mevinolin (kobs), the maximum concentration( Cmax ), and its corresponding maximum time( t time for the acid form to reach the maximum concentration) of mevinolinic acid, are discussed. The influencing factors, such as the kind of solvents, the acidic concentration, the initial mevinolin concentration, and the water content as well as temperature were investigated. Two kinds of comparative reactions, hydrolysis and alcoholysis, of mevinolin in solution were studied. This detailed study on the kinetics of mevinolin transformations is valuable and meaningful for the purification, preparation, injection manufacturing, extraction, storage, etc. , of mevinolin or other similar compounds. This work provides useful information for the quality control of mevinolin and mevinolin-like drugs as well.展开更多
A simple model is described to simulate kinetic processes in dielectric barrier dis-charges for O2/NOx mixtures. A threshold of ozone production found experimentally is confirmedby the calculations of this modeling, a...A simple model is described to simulate kinetic processes in dielectric barrier dis-charges for O2/NOx mixtures. A threshold of ozone production found experimentally is confirmedby the calculations of this modeling, and the underiying chemical reaction mechanisms are dis-cussed. It is also found that the effects of diffusion processes in the period of the lifetime of Oatoms are not important to microdischarge channels with a large radius, i.e. larger than l50 μm.展开更多
Kinetic knowledge is of great importance in achieving good control of the pyrolysis and gasification process and optimising system design. An overall kinetic pyrolysis scheme is therefore addressed here. The ki-net...Kinetic knowledge is of great importance in achieving good control of the pyrolysis and gasification process and optimising system design. An overall kinetic pyrolysis scheme is therefore addressed here. The ki-netic modelling incorporates the following basic steps: the degradation of the virgin biomass materials into pri-mary products ( tar, gas and semi-char), the decomposition of primary tar into secondary products and the continuous interaction between primary gas and char. The last step is disregarded completely by models in the literature. Analysis and comparison of predicted results from different kinetic schemes and experimental data on our fixed bed pyrolyser yielded very positive evidence to support our kinetic scheme.展开更多
The cementation reaction of copper on zinc metal in solutions of different concentrations ofcopper sulphate, at 25℃, has been studied and it is found to be a first order reaction. Moreover,the rates of this reaction ...The cementation reaction of copper on zinc metal in solutions of different concentrations ofcopper sulphate, at 25℃, has been studied and it is found to be a first order reaction. Moreover,the rates of this reaction at 0.15 mol'L-1 copper sulphate solution have been measured in a varietyof ethanol-water media at temperatures from 20℃ to 40℃. The correlation between the masstransfer coefficient and the dielectric constant has been investigated. Also, the thermodynamicparameters of activation have been calculated. The isokinetic relationship reveals the existenceof compensation effect, where the solute-solvent interactions play an important role.展开更多
基金financial support from Technical Quality Improvement Programme (TEQIP) phase-IIJadavpur University towards fellowship is also acknowledged
文摘An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200℃ for 10-120 min. The reduced samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chemical analysis. A good degree of metallization and reduction was achieved. Gas diffusion through the solid was identified as the reaction-rate-controlling resistance; however, during the initial period, particularly at lower temperatures, resistance to interfacial chemical reaction was also significant, though not dominant. The apparent rate constant was observed to increase marginally with decreasing size of the particles constituting the nuggets. The apparent activation energy of reduction was estimated to be in the range from 49.640 to 51.220 kJ/mol and was not observed to be affected by the particle size. The sulfur and carbon contents in the reduced samples were also determined.
文摘Based on the quantum chemical study of the silylidyne insertion reaction with NH3 or PH3, the general statistical thermodynamics and Eyring transition state theory with Wigner correction are used to compute the changes of thermodynamic functions, equilibrium constants, A factors and rate constants of the two reactions in the temperature range 200-2000K. The results show that both of these reactions are thermodynamically dominant at low temperatures and kinetically favored at higher temperatures. The comparison between these two reactions shows that the SiH reaction with NH3 is more exothermic than SiH with PH3, while the rate constant of SiH reaction with NH3 is lower than that of SiH with PH3 at the same temperature.
基金supported by the National Natural Science Foundation of China(51834008,52022109,52274307,and 21804319)National Key Research and Development Program of China(2021YFC2901100)+1 种基金Science Foundation of China University of Petroleum,Beijing(2462022QZDX008,2462021QNX2010,2462020YXZZ019 and 2462020YXZZ016)State Key Laboratory of Heavy Oil Processing(HON-KFKT2022-10).
文摘A green environmental protection and enhanced leaching process was proposed to recover all elements from spent lithium iron phosphate(LiFePO_(4)) lithium batteries.In order to reduce the influence of Al impurity in the recovery process,NaOH was used to remove impurity.After impurity removal,the spent LiFePO_(4) cathode material was used as raw material under the H_(2)SO_(4) system,and the pressure oxidation leaching process was adopted to achieve the preferential leaching of lithium.The E-pH diagram of the Fe-P-Al-H_(2)O system can determine the stable region of each element in the recovery process of spent LiFePO_(4)Li-batteries.Under the optimal conditions(500 r·min^(-1),15 h,363.15 K,0.4 MPa,the liquid-solid ratio was 4:1 ml·g^(-1)and the acid-material ratio was 0.29),the leaching rate of Li was 99.24%,Fe,Al,and Ti were 0.10%,2.07%,and 0.03%,respectively.The Fe and P were precipitated and recovered as FePO_(4)·2H_(2)O.The kinetic analysis shows that the process of high-pressure acid leaching of spent LiFePO_(4) materials depends on the surface chemical reaction.Through the life cycle assessment(LCA)of the spent LiFePO_(4) whole recovery process,eight midpoint impact categories were selected to assess the impact of recovery process.The results can provide basic environmental information on production process for recycling industry.
文摘An efficient culture medium producing a bacterial elastase with high yields was developed further following preliminary studies by means of response surface method. Central composite design (CCD) and response surface method-ology were applied to optimize the medium constituents. A central composite design was used to explain the combined effect of three medium constituents, viz, glucose, K2HPO4, MgSO47H2O. The strain produced more elastase in the completely optimized medium, as compared with the partially optimized medium. The fitted model of the second model, as per RSM, showed that glucose was 7.4 g/100 ml, casein 1.13 g/100 ml, corn steep flour 0.616 g/100 ml, K2HPO4 0.206 g/100 ml and MgSO47H2O 0.034 g/100 ml. The fermentation kinetics of these two culture media in the flask experiments were analyzed. It was found that the highest elastase productivity occurred at 54 hours. Higher glucose concentration had inhibitory effect on elastase production. At the same time, we observed that the glucose consumption rate was slow in the completely optimized medium, which can explain the lag period of the highest elastase production. Some metal ions and surfactant additives also affected elastase production and cell growth.
基金Work financially supported by the National Natural Science Foundation of China.
文摘The catalytic activity for the synthesis of methanol from carbon dioxide and hydrogen was measured on various binary and ternary catalysts containing copper oxide under a pressure of 10 atm. Among these samples the catalysts, CuO/ZnO/γ-Al_2O_3, demonstrated the highest activity and selectivity to methanol; MnO, as third component, had no promotional effect on the activity of meth- anol formation. Based on a simple power rate law the apparent activation energy estimation and par- tial pressure dependence measurement were accomplished over eight catalysts. The activation energies varied from 40 to 120 kJ / mol depending on the composition of catalysts. The rates of methanol for- mation to be 0.3 -- 0.9 order in H_2 and about 0.1 -- 0.2 order in CO_2 were reported.
基金This report was partially supported by the National Natural Science Foundation of China
文摘Kinetic studies of the singlet oxygenation of the title compounds were performed accord- ing to Monroe's method. The reaction rate increases with temperature decreasing, leading to a ne- gative activation enthalpy and a large negative activation entropy. These data are interpreted as the evidence for the intermediacy of an exciplex. The solvent effect on the reaction rate suggests that the “dioxetane” path involves a transition state or an intermediate with significant zwitterionic character. The electronic effect of the substituent is obvious, with electron-withdrawing substituent retarding the reaction and electron-donating substituent increasing the reaction rate. However, steric bulkiness at the 6-position does not play an important role in the reaction rate.
文摘The laser-induced optical fiber fluorimetry has been used for the first time to analyse the concentration of uranium(VI) in the kinetic studies on the extraction of uranium(VI) between 0.5 mol/L H_3PO_4 solution and HDEHP-cyclohexane system with Lewis cell. The effects of stirring speed, temper- ature and concentration of uranium(VI) and HDEHP on the rate of extraction were examined. These data show that the extraction rate of uranium(VI) in this system is controlled by the chemical reaction process at the interface. The rate equations and the rate constants of the forward and reverse ex- tractions were obtained. The mechanism of the extraction has been discussed.
文摘Adsorption-desorption kinetics of CO and H_2 on Ni surface were studied with molecular beam relaxation spectrometry. It is found that there are two adsorbed states in the substrate temperature range 330K<T<480K and 720K<T<900K respectively for CO/Ni system. These results can be explained by a precursor state model. Their kinetic parameters: E_(aα)=14.6kJ/mol, E_(dx)=49.3kJ/mol; E_(aβ)= 68.6kJ/mol, E_(dβ)=200.6kJ/mol. It is shown that there are two adsorbed states in the low (350K<T<430K) and high (550K<T<625K) temperature range respectively for H_2/Ni system. These results can be explained by a direct dissociative model. Their kinetic parameters:E_(dl)=26.3kJ/mol, E_(dh)=103.7kJ/mol.
文摘It is found that acetoacetanilide possesses very high promoting reactivity towards ceric ion in initiating polymerization of vinyl monomer. The kinetics of acrylamide polymerization and the activation energies were studied. The initiation mechanism of ceric/acetoacetanilide is proposed on the basis of experimental results of FT-IR and ESR.
基金support extended by SSN College of Engineering, Chennai, Tamil Nadu, India。
文摘In the present investigation,a microbial consortium consisting of four bacterial strains was selected for the treatment of pharmaceutical industry wa stewater.The consortium was immobilized on a natural support matrixLuffa and used for the treatment of real-time pharmaceutical wastewater in batch and continuous processes.The batch process was carried out to optimize the culture conditions and monitor the enzymatic activity.An array of enzymes such as alcohol dehydrogenase,aldehyde dehydrogenase,monooxygenase,catechol 2,3-dioxygenase and hydroquinol 1,2-dioxygenase were produced by the consortium.The kinetics of the degradation in the batch process was analyzed and it was noted to be a first-order reaction.For the continuous study,an aerobic fixed-film bioreactor(AFFBR) was utilized for a period of 61 days with variable hydraulic retention time(HRT) and organic loading rate(OLR).The immobilized microbes treated the wastewater by reducing the COD,phenolic contaminants and suspended solids.The OLR ranged between(0.56±0.05) kg COD·m^(-3) d^(-1) to 3.35 kg COD·m^(-3)·d^(-1) and the system achieved an average reduction of 96.8% of COD,92.6% of phenolic compounds and 95.2% of suspended solids.Kinetics of the continuous process was interpreted by three different models,where the modified Stover Kincannon model and the Grau second-order model proved to be best fit for the degradation reaction with the constant for saturation value,k_(L) being 95.12 g·L^(-1)·d^(-1).the constant for maximum utilization of the substrate U_(max) being 90.01 g·L^(-1) d^(-1) and substrate removal constant KY was1.074 d^(-1) for both the models.GC-MS analysis confirmed that most of the organic contaminants were degraded into innocuous metabolite s.
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 Key Research and Development Program of China(2018YFC1902504).
文摘In recent years,scientists have become increasingly concerned in recycling electronic trash,particularly waste printed circuit boards(WPCBs).Previous research has indicated that the presence of Cu impacts the pyrolysis of WPCBs.However,there may be errors in the experimental results,as printed circuit boards(PCBs)with copper and those without copper are produced differently.For this experiment,we blended copper powder with PCB nonmetallic resin powder in various ratios to create the samples.The apparent kinetics and pyrolysis properties of four resin powders with varying copper concentrations were compared using nonisothermal thermogravimetric analysis(TG)and thermal pyrolysis-gas chromatography mass spectrometry(Py-GC/MS).From the perspective of kinetics,the apparent activation energy of the resin powder in the pyrolysis reaction shows a rise(0.1<a<0.2)-stable(0.2<a<0.4)-accelerated increase(0.4<a<0.8)-decrease(0.8<a<0.9)process.After adding copper powder,the apparent activation energy changes more obviously when(0.2<a<0.4).In the early stage of the pyrolysis reaction(0.1<a<0.6),the apparent activation energy is reduced,but when a?0.8,it is much higher than that of the resin sample without copper.Additionally,it is discovered using thermogravimetric analysis and Py-GC/MS that copper shortens the temperature range of the primary pyrolysis reaction and prevents the creation of compounds containing bromine.This inhibition will raise the temperature at which compounds containing bromine first form,and it will keep rising as the copper level rises.The majority of the circuit board molecules have lower bond energies when copper is present,according to calculations performed using the Gaussian09 software,which promotes the pyrolysis reaction.
基金financially supported by the National Natural Science Foundation of China (No. 51402016)the Fundamental Research Funds for the Central Universities (No. FRF-TP-15-008A2)
文摘A one-step sintering process of bauxite raw material from direct mining was completed, and the kinetics of this process was analyzed thoroughly. The results show that the sintering kinetics of bauxite raw material exhibits the liquid-phase sintering behavior. A small portion of impurities existed in the raw material act as a liquid phase. After X-ray diffraction analyses, scanning electron microscopy observations, and kinetics calculations, sintering temperature and heating duration were determined as the two major factors contributing to the sintering process and densification of bauxite ore. An elevated heating temperature and longer duration favor the densification process. The major obstacle for the densification of bauxite material is attributed to the formation of the enclosed blowhole during liquid-phase sintering.
基金the financial support From the Open Fund Project of Key Lab.of Biomass Energy and Material,Jiangsu Province(JSBEM201907)the Ordinary University Young Innovative Talents Project of Guangdong Province(2018KQNCX119)+4 种基金Provincial Science and Technology Planning Projects of Guangdong Province(2017A040405055)Guangdong-Hong Kong Cooperation Project(2017A050506055)Guangdong Provincial Education Department Project(Natural Science,2017KZDXM045)Guangzhou major special project for collaborative innovation of industry,University and research(201604020074)the fund project of Yele Science and Technology Innovation(YL201807).
文摘The plasticizer is an important polymer material additive.Non-toxic and environmentally friendly plasticizers are developed recently in order to decrease fossil fuel reserves,serious environmental pollution and the toxicity of phthalate esters.In this study,a new,efficient and environmentally friendly plasticizer of hydrogenated rosin dodecyl ester was prepared by an esterification reaction of hydrogenated rosin and dodecanol.The influences of different reaction conditions(including different catalysts,the catalyst concentration,the ratio of the reactants,reaction temperature,and reaction time)on the esterification yield are examined and discussed.Hydrogenated rosin dodecyl ester with 71.8%yield was synthesized under the optimized reaction conditions(1:0.8 molar ratio of rosin to dodecanol,1 mol%tetrabutyl titanate concentration,and 210℃for 6 h).The esterification reaction is a second-order reaction,and kinetic calculations showed that the activation energy is 39.77 KJ·mol^(−1).The structure of the hydrogenated rosin dodecyl ester was confirmed by FT-IR spectroscopy and^(13)C NMR spectrum.Besides,the thermal stability of target product(hydrogenated rosin dodecyl ester)was also tested by thermal gravimetric analysis(TGA),which showed a good thermal stability.
基金Supported by Shanghai Leading Discipline Project(No. Y0301) and the Funds of Shanghai Scientific and Technology Develop-ment(No. 03DZ19546)
文摘Mevinolin is one of the earlier statin drugs which is effective for the treatment of hypercholesterolemia, as an inhibitor of the HMG-CoA reductase. The transformations of mevinolin in acidic alcohol( such as ethanol, methanol and isopropanol) solutions caused by solvent effects were revealed in the present article. The solvates, that is, mevinolinic methyl ester, mevinolinic ethyl ester and mevinolinic isopropyl ester, were identified by LC/PDA and LC/MS. The kinetics parameters of the transformations caused by solvent effects, such as the observed rate constant of mevinolin (kobs), the maximum concentration( Cmax ), and its corresponding maximum time( t time for the acid form to reach the maximum concentration) of mevinolinic acid, are discussed. The influencing factors, such as the kind of solvents, the acidic concentration, the initial mevinolin concentration, and the water content as well as temperature were investigated. Two kinds of comparative reactions, hydrolysis and alcoholysis, of mevinolin in solution were studied. This detailed study on the kinetics of mevinolin transformations is valuable and meaningful for the purification, preparation, injection manufacturing, extraction, storage, etc. , of mevinolin or other similar compounds. This work provides useful information for the quality control of mevinolin and mevinolin-like drugs as well.
文摘A simple model is described to simulate kinetic processes in dielectric barrier dis-charges for O2/NOx mixtures. A threshold of ozone production found experimentally is confirmedby the calculations of this modeling, and the underiying chemical reaction mechanisms are dis-cussed. It is also found that the effects of diffusion processes in the period of the lifetime of Oatoms are not important to microdischarge channels with a large radius, i.e. larger than l50 μm.
文摘Kinetic knowledge is of great importance in achieving good control of the pyrolysis and gasification process and optimising system design. An overall kinetic pyrolysis scheme is therefore addressed here. The ki-netic modelling incorporates the following basic steps: the degradation of the virgin biomass materials into pri-mary products ( tar, gas and semi-char), the decomposition of primary tar into secondary products and the continuous interaction between primary gas and char. The last step is disregarded completely by models in the literature. Analysis and comparison of predicted results from different kinetic schemes and experimental data on our fixed bed pyrolyser yielded very positive evidence to support our kinetic scheme.
文摘The cementation reaction of copper on zinc metal in solutions of different concentrations ofcopper sulphate, at 25℃, has been studied and it is found to be a first order reaction. Moreover,the rates of this reaction at 0.15 mol'L-1 copper sulphate solution have been measured in a varietyof ethanol-water media at temperatures from 20℃ to 40℃. The correlation between the masstransfer coefficient and the dielectric constant has been investigated. Also, the thermodynamicparameters of activation have been calculated. The isokinetic relationship reveals the existenceof compensation effect, where the solute-solvent interactions play an important role.