Normal spinel LiMn 2O 4 was synthesized by sol-gel method using lithium nitrate,manganese nitrate,citric acid and ethylene glycol as raw materials. LiMn 2O 4 was characterized by XRD,TG-DTA,IR,SEM and AAS.The opti...Normal spinel LiMn 2O 4 was synthesized by sol-gel method using lithium nitrate,manganese nitrate,citric acid and ethylene glycol as raw materials. LiMn 2O 4 was characterized by XRD,TG-DTA,IR,SEM and AAS.The optimum conditions for the synthesis were explored.Citric acid and ethylene glycol were mixed with molar ratio of 0.25,and the mixture was esterified at 140℃ for 4 hours.Then lithium nitrate and manganese nitrate were added with molar ratio of 0.6. In the system,the total molar of cations was equal to that of citric acid. At last, reflux the system at 105℃ for 2 hours. Dried gel was fired at 600℃ for 8 hours. Particle diameters of raw product were about 100 nm mainly. Further research shows that lithium ion of LiMn 2O 4 is easy to be extracted,and normal spinel λ-MnO 2 can be obtained after lithium ion extraction.展开更多
Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate therm...Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate thermodynamic data provide basic thermodynamic quantities for the actual chemical engineering process and are useful in analyzing product distribution because FTS demonstrates many features of an equilibrium-controlled system. Our results show that the number of thermodynamically allowed products to increase when lowering temperature, raising pressure, and raising H2/CO ratio. At low temperature, high pressure and high H2/CO ratio, many products are thermodynamically allowed and the selectivity of product has to be controlled by kinetic factors. On the other hand, high selectivity of lighter products can be realized in thermodynamics by raising temperature and lowering pressure. We found that the equilibrium product yield will reach a maximum and remain unchanged when lowering temperature, raising pressure, and raising H2/CO ratio to some limits, implying that optimizing reaction conditions has no effect on equilibrium product yields beyond these limits. The thermodynamic analysis is also useful in designing and evaluating FTS reaction mechanisms. We found that reaction pathways through formaldehyde should be discarded because of its extremely low equilibrium yield. Recently, in the FTS process using metal-oxide-zeolite catalysts for the highly selective production of C2-C4 olefins and aromatic hydrocarbons, there are several guesses on the possible reaction intermediates entering the zeolite channel. Our results show that ketene, methanol, and dimethyl ether are three possible reaction intermediates.展开更多
Calcium sulfate(CaSO_(4))has been verified as a promising oxygen carrier(OC)in the chemical looping combustion(CLC)for its high oxygen capacity,abundant reserve and low cost,but its low reactivity and deleterious sulf...Calcium sulfate(CaSO_(4))has been verified as a promising oxygen carrier(OC)in the chemical looping combustion(CLC)for its high oxygen capacity,abundant reserve and low cost,but its low reactivity and deleterious sulfur species emission from the side reactions of CaSO_(4) should be well considered for its wide application in CLC.In order to promote the reactivity of CaSO_(4) and increase its potential to inhibit the gaseous sulfur emission,a CeO_(2)-enhanced CaSO_(4) OC mixed OC of core–shell structure was prepared using the combined template synthesis method.Reaction characteristics of the prepared CaSO_(4)-CeO_(2) mixed OC with a typical lignite was first conducted and systematically investigated,and an improved reactivity of the prepared CaSO_(4)-CeO_(2) mixed OC was demonstrated than its single component CaSO_(4) or CeO_(2) due to the fast transfer and exchange of oxygen from the CaSO_(4) substrate to coal via the doped CeO_(2).Furthermore,the solid products formed from the mixed CaSO_(4)-CeO_(2) OC with the selected coal were collected and analyzed.Especially,evolution and redistribution of the sulfur species of different forms were focused.At the latter reaction stage of YN reaction with the CaSO_(4)-CeO_(2) mixed OC,the SO_(2) emitted from the side reactions of CaSO_(4) was greatly diminished and the doped CeO_(2) was proven effective to directionally fix the SO_(2) released to turn into different solid sulfur compounds,which were determined as Ce_(2)O_(2)S,Ce_(2)S_(3) and Ce_(2)(SO_(4))_(3)·5H_(2)O and formed through the different pathways.In addition,good regeneration of the reduced CaSO_(4)-CeO_(2) mixed OC could be reached in spite of the unavoidable interaction between the included minerals in coal and the reduced mixed OC.Overall,the combined template method-made CaSO_(4)-CeO_(2) mixed OC reported herein was not only endowed with enhanced reactivity for coal conversion,but also owned the potential to directionally fix the gaseous sulfur emission,which is quite applicable as OC for simultaneous decarbonatization and desulfurization in the real CLC process.展开更多
The Li 4SiO 4 has been prepared by the sol gel method and characterized by IR, DTA, TG, XRD, SEM and AC impedance measurements. The results showed that in comparison with the solid state method Li 4SiO 4 could be obta...The Li 4SiO 4 has been prepared by the sol gel method and characterized by IR, DTA, TG, XRD, SEM and AC impedance measurements. The results showed that in comparison with the solid state method Li 4SiO 4 could be obtained by sol gel method at lower temperature and the products exhibited smaller particle size and higher ionic conductivity.展开更多
基金FundedbytheNationalNaturalScienceFoundationofChi na (No .5 9972 0 2 7)
文摘Normal spinel LiMn 2O 4 was synthesized by sol-gel method using lithium nitrate,manganese nitrate,citric acid and ethylene glycol as raw materials. LiMn 2O 4 was characterized by XRD,TG-DTA,IR,SEM and AAS.The optimum conditions for the synthesis were explored.Citric acid and ethylene glycol were mixed with molar ratio of 0.25,and the mixture was esterified at 140℃ for 4 hours.Then lithium nitrate and manganese nitrate were added with molar ratio of 0.6. In the system,the total molar of cations was equal to that of citric acid. At last, reflux the system at 105℃ for 2 hours. Dried gel was fired at 600℃ for 8 hours. Particle diameters of raw product were about 100 nm mainly. Further research shows that lithium ion of LiMn 2O 4 is easy to be extracted,and normal spinel λ-MnO 2 can be obtained after lithium ion extraction.
基金the National Natural Science Foundation of China (No.91645201, No.21873019 and No.21573044).
文摘Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate thermodynamic data provide basic thermodynamic quantities for the actual chemical engineering process and are useful in analyzing product distribution because FTS demonstrates many features of an equilibrium-controlled system. Our results show that the number of thermodynamically allowed products to increase when lowering temperature, raising pressure, and raising H2/CO ratio. At low temperature, high pressure and high H2/CO ratio, many products are thermodynamically allowed and the selectivity of product has to be controlled by kinetic factors. On the other hand, high selectivity of lighter products can be realized in thermodynamics by raising temperature and lowering pressure. We found that the equilibrium product yield will reach a maximum and remain unchanged when lowering temperature, raising pressure, and raising H2/CO ratio to some limits, implying that optimizing reaction conditions has no effect on equilibrium product yields beyond these limits. The thermodynamic analysis is also useful in designing and evaluating FTS reaction mechanisms. We found that reaction pathways through formaldehyde should be discarded because of its extremely low equilibrium yield. Recently, in the FTS process using metal-oxide-zeolite catalysts for the highly selective production of C2-C4 olefins and aromatic hydrocarbons, there are several guesses on the possible reaction intermediates entering the zeolite channel. Our results show that ketene, methanol, and dimethyl ether are three possible reaction intermediates.
基金supported by the National Natural Science Founda-tion of China(Nos.51776073,51906083)Key Research&Develop-ment program of Henan Province(No.162102210233)+1 种基金North China University of Water Resources and Electric Power Innovative Project(Nos.2019XA014,2019XB058)Scientific Research&Development Project of Ji-Yan Energy Science and Technology Research Institute(NKY2020-05).
文摘Calcium sulfate(CaSO_(4))has been verified as a promising oxygen carrier(OC)in the chemical looping combustion(CLC)for its high oxygen capacity,abundant reserve and low cost,but its low reactivity and deleterious sulfur species emission from the side reactions of CaSO_(4) should be well considered for its wide application in CLC.In order to promote the reactivity of CaSO_(4) and increase its potential to inhibit the gaseous sulfur emission,a CeO_(2)-enhanced CaSO_(4) OC mixed OC of core–shell structure was prepared using the combined template synthesis method.Reaction characteristics of the prepared CaSO_(4)-CeO_(2) mixed OC with a typical lignite was first conducted and systematically investigated,and an improved reactivity of the prepared CaSO_(4)-CeO_(2) mixed OC was demonstrated than its single component CaSO_(4) or CeO_(2) due to the fast transfer and exchange of oxygen from the CaSO_(4) substrate to coal via the doped CeO_(2).Furthermore,the solid products formed from the mixed CaSO_(4)-CeO_(2) OC with the selected coal were collected and analyzed.Especially,evolution and redistribution of the sulfur species of different forms were focused.At the latter reaction stage of YN reaction with the CaSO_(4)-CeO_(2) mixed OC,the SO_(2) emitted from the side reactions of CaSO_(4) was greatly diminished and the doped CeO_(2) was proven effective to directionally fix the SO_(2) released to turn into different solid sulfur compounds,which were determined as Ce_(2)O_(2)S,Ce_(2)S_(3) and Ce_(2)(SO_(4))_(3)·5H_(2)O and formed through the different pathways.In addition,good regeneration of the reduced CaSO_(4)-CeO_(2) mixed OC could be reached in spite of the unavoidable interaction between the included minerals in coal and the reduced mixed OC.Overall,the combined template method-made CaSO_(4)-CeO_(2) mixed OC reported herein was not only endowed with enhanced reactivity for coal conversion,but also owned the potential to directionally fix the gaseous sulfur emission,which is quite applicable as OC for simultaneous decarbonatization and desulfurization in the real CLC process.
文摘The Li 4SiO 4 has been prepared by the sol gel method and characterized by IR, DTA, TG, XRD, SEM and AC impedance measurements. The results showed that in comparison with the solid state method Li 4SiO 4 could be obtained by sol gel method at lower temperature and the products exhibited smaller particle size and higher ionic conductivity.
