In this study, the effects of pre-carburization of catalyst, hydrogen addition to methane feed and the space velocity of methane on the catalytic performance in methane to benzene （MTB） reaction were discussed in de...In this study, the effects of pre-carburization of catalyst, hydrogen addition to methane feed and the space velocity of methane on the catalytic performance in methane to benzene （MTB） reaction were discussed in detail over Mo/HZSM-5 catalyst at 1023 K and 0.3 MPa. Compared with the non-precarburized catalyst, the Mo catalyst pre-carburized under the flow of CHa＋4H2 at 973 K was found to have the higher activity and better stability. Further 6% H2 addition to the methane feed suppressed the aromatic type of coke formation effectively, and improved the stability of catalyst markedly, moreover gave a much longer reaction life of catalyst （53 h at 1023 K and 5400 ml/（g-h）） and much more formation amounts of benzene and hydrogen. With increase of methane space velocity, both the naphthalene formation selectivity and the coke formation selectivity were decreased by the shortened contact time; the benzene formation selectivity and total formation amount before the complete deactivation of catalyst were increased markedly, while the total naphthalene and coke formation amounts did not change much. At high methane space velocity （≥5400 ml/（g·h））, a new middle temperature coke derived from the high temperature aromatic coke was formed on the catalyst; all the coke formed could be burnt off at lower temperature in oxygen, compared with those obtained at low space velocity. Considering the benzene formation amount and catalyst stability together, 5400 ml/（g·h） was proved to be the most efficient methane space velocity for benzene production.展开更多
Copper and cobalt oxides supported on CeO2 were investigated for preferential oxidation of carbon monoxide(CO-PROX)in the presence of excess hydrogen and CO2.(Cuo)1-x(Co3 O4)x/3-(CeO2)2.5(x=0,0.25,0.50,0.75,0.85 and 1...Copper and cobalt oxides supported on CeO2 were investigated for preferential oxidation of carbon monoxide(CO-PROX)in the presence of excess hydrogen and CO2.(Cuo)1-x(Co3 O4)x/3-(CeO2)2.5(x=0,0.25,0.50,0.75,0.85 and 1)catalysts were prepared by coprecipitation method.These mixed oxide catalysts were characterized by several physicochemical techniques,such as BET surface area(SBET),X-ray diffraction(XRD),high resolution transmission electron microscopy(HRTEM),temperature programmed reduction(TPR)and X-ray photoelectron spectroscopy(XPS).XRD studies show the peaks related to CuO and Co3 O4 phases in copper and cobalt containing CeO2 catalysts.The average particle size of the CeO2 crystallites is in the range of 8-10 nm as evaluated from HRTEM studies.XPS studies demonstrate that Cu,Co and Ce in(cuO)1-x(Co3O4)x/3-(CeO2)2.5 catalysts are presented in+2 and+1,+3 and+2 and+4 and+3 oxidation states,respectively.The catalyst with x=0.75 shows better activity and selectivity towards CO-PROX.Though the catalyst with only copper(CuO-CeO2,x=0)shows good activity but reverse water gas shift(RWGS)reaction is noticed at high temperature.On the other hand,RWGS reaction is suppressed on the cobalt containing CuO-ceO2 catalyst.Cobalt on CeO2 with x=1 shows hardly any activity for PRoX reaction at low temperatures.No methanation activity is observed on CuO-CeO2 or Co3O4-CeO2 catalysts.In contrast,combination of copper and cobalt on CeO2 shows methanation of CO where enhanced activity is observed with increasing in cobalt content.展开更多
For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mi...For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mixed H_2/H_∞ state feedback attitude control problem of microsatellite based on extended LMI method.Firstly,the microsatellite attitude control system is established and transformed into corresponding state space form.Then,without the equivalence restriction of the two Lyapunov variables of H_2 and H∞performance,this paper introduces additional variables to design the mixed H_2/H_∞ control method based on LMI which can also reduce the conservatives.Finally,numerical simulations are analyzed to show that the proposed method can make the satellite stable within 20 s whether there is additive perturbation of the controller gain or not.The comparative analysis of the simulation results between extended LMI method and traditional LMI method also demonstrates the effectiveness and feasibility of the proposed method in this paper.展开更多
Kinetic analysis of coupled effects of CO2 and H2 additions on laminar lean premixed dimethyl ether flames is performed at atmospheric pressure. The coupled effects of H2/CO2 additions on major species, intermediate s...Kinetic analysis of coupled effects of CO2 and H2 additions on laminar lean premixed dimethyl ether flames is performed at atmospheric pressure. The coupled effects of H2/CO2 additions on major species, intermediate stable species and radicals are discussed and analyzed in detail. The dilution, thermal and chemical effects of H2 and CO2 are separated and identified. The results show that H2 addition can slightly mitigate the CO2 chemical effects on decreasing the temperatures, H radical concen- tration, acetylene mole fraction and formaldehyde concentration. After CO2 is added, the H2 chemical effects on increasing the temperatures are enhanced. DME oxidation is promoted by the H2 chemical effects, which is further strengthened by the CO2 addition. Moreover, CO2 addition can reduce the H2 chemical effects on increasing the H radical mole fraction, but strengthen the H2 chemical effects on increasing the production of HO2 and C2H2. CH2O formation can be promoted by the H2 chemical effects, which is enhanced by the CO2 addition. In actually, the H2/CO2 coupled chemical effects almost have no obvious in- fluence on the temperatures and HO2 mole fraction. DME consumption is delayed by the H2/CO2 coupled chemical effects. Furthermore, the H2/CO2 coupled chemical effects can decrease the H radical mole fraction, CH4 concentration, C2H2 mole fraction, CH2O concentration and CHaCHO mole fraction, but increase the CO concentration.展开更多
Electrocoagulation(EC)technique was used to investigate the removal performance of aqueous perfluorooctanoic acid(PFOA)with relatively high concentration as simulating the wastewater from organic fluorine industry.A c...Electrocoagulation(EC)technique was used to investigate the removal performance of aqueous perfluorooctanoic acid(PFOA)with relatively high concentration as simulating the wastewater from organic fluorine industry.A comparison was done with the similar amount of coagulant between EC and chemical coagulation process.PFOA removal obtained was higher with EC process,especially for Fe anode.Several factors were studied to optimize the EC process.At the optimal operating parameters including 37.5 mA/cm^2 of current density,initial pH 3.77,and 180 rpm of mixing speed,93%of PFOA could be removed with 100 mg/L of initial concentration after 90-min electrolysis.Furthermore,the remove efficiency could be obviously improved by H2O2 intermittent addition,which removed more than 99%of PFOA within 40-min EC.It could be attributed to that H2O2 facilitated the oxidative transformation from ferrous to ferric ion.In addition,the adsorptive removal of aqueous PFOA on Fe flocs during EC was also verified by fourier transform infrared spectra.展开更多
文摘In this study, the effects of pre-carburization of catalyst, hydrogen addition to methane feed and the space velocity of methane on the catalytic performance in methane to benzene （MTB） reaction were discussed in detail over Mo/HZSM-5 catalyst at 1023 K and 0.3 MPa. Compared with the non-precarburized catalyst, the Mo catalyst pre-carburized under the flow of CHa＋4H2 at 973 K was found to have the higher activity and better stability. Further 6% H2 addition to the methane feed suppressed the aromatic type of coke formation effectively, and improved the stability of catalyst markedly, moreover gave a much longer reaction life of catalyst （53 h at 1023 K and 5400 ml/（g-h）） and much more formation amounts of benzene and hydrogen. With increase of methane space velocity, both the naphthalene formation selectivity and the coke formation selectivity were decreased by the shortened contact time; the benzene formation selectivity and total formation amount before the complete deactivation of catalyst were increased markedly, while the total naphthalene and coke formation amounts did not change much. At high methane space velocity （≥5400 ml/（g·h））, a new middle temperature coke derived from the high temperature aromatic coke was formed on the catalyst; all the coke formed could be burnt off at lower temperature in oxygen, compared with those obtained at low space velocity. Considering the benzene formation amount and catalyst stability together, 5400 ml/（g·h） was proved to be the most efficient methane space velocity for benzene production.
基金Project supported by Council of Scientific and Industrial Research,Government of India through a Senior Research Fellowship。
文摘Copper and cobalt oxides supported on CeO2 were investigated for preferential oxidation of carbon monoxide(CO-PROX)in the presence of excess hydrogen and CO2.(Cuo)1-x(Co3 O4)x/3-(CeO2)2.5(x=0,0.25,0.50,0.75,0.85 and 1)catalysts were prepared by coprecipitation method.These mixed oxide catalysts were characterized by several physicochemical techniques,such as BET surface area(SBET),X-ray diffraction(XRD),high resolution transmission electron microscopy(HRTEM),temperature programmed reduction(TPR)and X-ray photoelectron spectroscopy(XPS).XRD studies show the peaks related to CuO and Co3 O4 phases in copper and cobalt containing CeO2 catalysts.The average particle size of the CeO2 crystallites is in the range of 8-10 nm as evaluated from HRTEM studies.XPS studies demonstrate that Cu,Co and Ce in(cuO)1-x(Co3O4)x/3-(CeO2)2.5 catalysts are presented in+2 and+1,+3 and+2 and+4 and+3 oxidation states,respectively.The catalyst with x=0.75 shows better activity and selectivity towards CO-PROX.Though the catalyst with only copper(CuO-CeO2,x=0)shows good activity but reverse water gas shift(RWGS)reaction is noticed at high temperature.On the other hand,RWGS reaction is suppressed on the cobalt containing CuO-ceO2 catalyst.Cobalt on CeO2 with x=1 shows hardly any activity for PRoX reaction at low temperatures.No methanation activity is observed on CuO-CeO2 or Co3O4-CeO2 catalysts.In contrast,combination of copper and cobalt on CeO2 shows methanation of CO where enhanced activity is observed with increasing in cobalt content.
文摘For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mixed H_2/H_∞ state feedback attitude control problem of microsatellite based on extended LMI method.Firstly,the microsatellite attitude control system is established and transformed into corresponding state space form.Then,without the equivalence restriction of the two Lyapunov variables of H_2 and H∞performance,this paper introduces additional variables to design the mixed H_2/H_∞ control method based on LMI which can also reduce the conservatives.Finally,numerical simulations are analyzed to show that the proposed method can make the satellite stable within 20 s whether there is additive perturbation of the controller gain or not.The comparative analysis of the simulation results between extended LMI method and traditional LMI method also demonstrates the effectiveness and feasibility of the proposed method in this paper.
基金supported by the National Natural Science Foundation of China(Grant Nos.51576100&51306091)the Jiangsu Provincial Natural Science Foundation of China(Grant Nos.BK20140034&BK20130758)+1 种基金Jiangsu “Shuangchuang Program”the Jiangsu Provincial Project of “Six Talent Summit”(Grant No.2014-XNY-002)
文摘Kinetic analysis of coupled effects of CO2 and H2 additions on laminar lean premixed dimethyl ether flames is performed at atmospheric pressure. The coupled effects of H2/CO2 additions on major species, intermediate stable species and radicals are discussed and analyzed in detail. The dilution, thermal and chemical effects of H2 and CO2 are separated and identified. The results show that H2 addition can slightly mitigate the CO2 chemical effects on decreasing the temperatures, H radical concen- tration, acetylene mole fraction and formaldehyde concentration. After CO2 is added, the H2 chemical effects on increasing the temperatures are enhanced. DME oxidation is promoted by the H2 chemical effects, which is further strengthened by the CO2 addition. Moreover, CO2 addition can reduce the H2 chemical effects on increasing the H radical mole fraction, but strengthen the H2 chemical effects on increasing the production of HO2 and C2H2. CH2O formation can be promoted by the H2 chemical effects, which is enhanced by the CO2 addition. In actually, the H2/CO2 coupled chemical effects almost have no obvious in- fluence on the temperatures and HO2 mole fraction. DME consumption is delayed by the H2/CO2 coupled chemical effects. Furthermore, the H2/CO2 coupled chemical effects can decrease the H radical mole fraction, CH4 concentration, C2H2 mole fraction, CH2O concentration and CHaCHO mole fraction, but increase the CO concentration.
基金the National Natural Science Foundation of China(21547011,21177089,21307036)the National High-Tech Research and Development Program of China(863 Program,2013AA062705)+1 种基金the Guangdong Natural Science Foundation(2014A030313761)the Shenzhen Science and Technology Project for Fundamental Research(JCYJ20150324141711622,JCYJ20150529164656097).
文摘Electrocoagulation(EC)technique was used to investigate the removal performance of aqueous perfluorooctanoic acid(PFOA)with relatively high concentration as simulating the wastewater from organic fluorine industry.A comparison was done with the similar amount of coagulant between EC and chemical coagulation process.PFOA removal obtained was higher with EC process,especially for Fe anode.Several factors were studied to optimize the EC process.At the optimal operating parameters including 37.5 mA/cm^2 of current density,initial pH 3.77,and 180 rpm of mixing speed,93%of PFOA could be removed with 100 mg/L of initial concentration after 90-min electrolysis.Furthermore,the remove efficiency could be obviously improved by H2O2 intermittent addition,which removed more than 99%of PFOA within 40-min EC.It could be attributed to that H2O2 facilitated the oxidative transformation from ferrous to ferric ion.In addition,the adsorptive removal of aqueous PFOA on Fe flocs during EC was also verified by fourier transform infrared spectra.
