Modern diesel passenger cars already fulfill high demands regarding the reduction in NOx emissions through complex exhaust aftertreatment systems.With the consideration of real driving emissions,the reduction in NOx e...Modern diesel passenger cars already fulfill high demands regarding the reduction in NOx emissions through complex exhaust aftertreatment systems.With the consideration of real driving emissions,the reduction in NOx emissions in high transient engine operation becomes even more challenging.Apart from increasing the complexity of exhaust aftertreatment systems,internal engine measures play a major role.The approach to reducing NOx emissions described in this paper uses the precise control of the combustion.For this purpose,the method of digital combustion rate shaping control is applied,which allows the realization of a predefined combustion by automatically adapting the injection profile during operation.Within this work,this controller is extended in order to control the predefined combustion trace based on target NOx values.First,the working principal of the state-of-the-art digital combusting rate shaping controller is explained.In the next step,the design and strategy of the extended control approach are explained and validated.Finally,its potential to reduce engine-out NOx emissions during transient driving situations is evaluated based on simulations of the WLTC.It is shown that the control concept fulfills the requirements and is able to effectively reduce high NOx peaks during transient operation.展开更多
NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion（MOF-C） technique, for use as an anode material in rechargeable lithium ion batteries（LIBs）...NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion（MOF-C） technique, for use as an anode material in rechargeable lithium ion batteries（LIBs）. The structural and electronic properties of these nanoparticles are studied using various techniques, including powder X-ray diffraction（PXRD）, transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS）, and N_2 adsorption/desorption studies. The as-synthesized NiO nanoparticles sustained reversible stable capacities of 748 and 410 mAh/g at applied current densities of 500 and 1000 m A/g, respectively, after 100 cycles. Furthermore, the anode displays a notable rate capability, achieving a stable capacity of ~200 mAh/g at a high current density of10 A/g. These results indicate that the size of the NiO nanoparticles and their high surface area influence their electrochemical properties. Specifically, this combustion strategy is clearly favorable for improving the cyclability and rate capability of various metal oxides in rechargeable battery electrodes.展开更多
The effect of the preparation method on the properties of LaMnO3 and La0.8Sr0.2MnO3 perovskite was studied. Materials were prepared by four methods: sol-gel, chemical combustion, solvothermal and spray pyrolysis and c...The effect of the preparation method on the properties of LaMnO3 and La0.8Sr0.2MnO3 perovskite was studied. Materials were prepared by four methods: sol-gel, chemical combustion, solvothermal and spray pyrolysis and characterized. The effect of the synthesis method on the texture, acid-base character of the surface, reducibility with hydrogen, oxygen desorption, surface composition and catalytic activity for combustion of lean methane was studied. It was found that synthesis method affects physicochemical properties of obtained materials-solvothermally produced materials exhibit well-developed surface area, presence of reactive oxygen species on surface and high catalytic activity for CH4 combustion. Generally, LaMnO3 and La0.8Sr0.2MnO3 perovskites show catalytic activity for lean CH4 combustion comparable or higher than the activity of 0.5 wt.% Pt/Al2O3 but lower than 1 wt.% Pd/Al2O3.展开更多
This paper represents an attempt to extend the mechanisms of reactions and kinetics of a methane combustion reaction.Three saddle points（SPs） are identified in the reaction CH_4＋ O（~3P） → OH ＋ CH_3 using the co...This paper represents an attempt to extend the mechanisms of reactions and kinetics of a methane combustion reaction.Three saddle points（SPs） are identified in the reaction CH_4＋ O（~3P） → OH ＋ CH_3 using the complete active space selfconsistent field and the multireference configuration interaction methods with a proper active space. Our calculations give a fairly accurate description of the regions around the twin first-order SPs（~3A＇ and ~3A〞） along the direction of O（~3P） attacking a near-collinear H–CH_3. One second-order SP^（2nd）（~3E） between the above twin SPs is the result of the C_（3v） symmetry Jahn–Teller coupling within the branching space. Further kinetic calculations are performed with the canonical unified statistical theory method with the temperature ranging from 298 K to 1000 K. The rate constants are also reported. The present work reveals the reaction mechanism of hydrogen-abstraction by the O（~3P） from methane, and develops a better understanding for the role of SPs. In addition, a comparison of the reactions of O（~3P） with methane through different channels allows a molecule-level discussion of the reactivity and mechanism of the title reaction.展开更多
基金This work is part of the Excellence Cluster“Tailor-made fuels from biomass,”which is funded by the Excellence Initiative of the Federal Government to promote science and research at German universities.
文摘Modern diesel passenger cars already fulfill high demands regarding the reduction in NOx emissions through complex exhaust aftertreatment systems.With the consideration of real driving emissions,the reduction in NOx emissions in high transient engine operation becomes even more challenging.Apart from increasing the complexity of exhaust aftertreatment systems,internal engine measures play a major role.The approach to reducing NOx emissions described in this paper uses the precise control of the combustion.For this purpose,the method of digital combustion rate shaping control is applied,which allows the realization of a predefined combustion by automatically adapting the injection profile during operation.Within this work,this controller is extended in order to control the predefined combustion trace based on target NOx values.First,the working principal of the state-of-the-art digital combusting rate shaping controller is explained.In the next step,the design and strategy of the extended control approach are explained and validated.Finally,its potential to reduce engine-out NOx emissions during transient driving situations is evaluated based on simulations of the WLTC.It is shown that the control concept fulfills the requirements and is able to effectively reduce high NOx peaks during transient operation.
基金supported by National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(2014R1A2A1A10050821)
文摘NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion（MOF-C） technique, for use as an anode material in rechargeable lithium ion batteries（LIBs）. The structural and electronic properties of these nanoparticles are studied using various techniques, including powder X-ray diffraction（PXRD）, transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS）, and N_2 adsorption/desorption studies. The as-synthesized NiO nanoparticles sustained reversible stable capacities of 748 and 410 mAh/g at applied current densities of 500 and 1000 m A/g, respectively, after 100 cycles. Furthermore, the anode displays a notable rate capability, achieving a stable capacity of ~200 mAh/g at a high current density of10 A/g. These results indicate that the size of the NiO nanoparticles and their high surface area influence their electrochemical properties. Specifically, this combustion strategy is clearly favorable for improving the cyclability and rate capability of various metal oxides in rechargeable battery electrodes.
基金financed by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Chemistry of Wroclaw University of Technology.
文摘The effect of the preparation method on the properties of LaMnO3 and La0.8Sr0.2MnO3 perovskite was studied. Materials were prepared by four methods: sol-gel, chemical combustion, solvothermal and spray pyrolysis and characterized. The effect of the synthesis method on the texture, acid-base character of the surface, reducibility with hydrogen, oxygen desorption, surface composition and catalytic activity for combustion of lean methane was studied. It was found that synthesis method affects physicochemical properties of obtained materials-solvothermally produced materials exhibit well-developed surface area, presence of reactive oxygen species on surface and high catalytic activity for CH4 combustion. Generally, LaMnO3 and La0.8Sr0.2MnO3 perovskites show catalytic activity for lean CH4 combustion comparable or higher than the activity of 0.5 wt.% Pt/Al2O3 but lower than 1 wt.% Pd/Al2O3.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51574016 and 51604018)
文摘This paper represents an attempt to extend the mechanisms of reactions and kinetics of a methane combustion reaction.Three saddle points（SPs） are identified in the reaction CH_4＋ O（~3P） → OH ＋ CH_3 using the complete active space selfconsistent field and the multireference configuration interaction methods with a proper active space. Our calculations give a fairly accurate description of the regions around the twin first-order SPs（~3A＇ and ~3A〞） along the direction of O（~3P） attacking a near-collinear H–CH_3. One second-order SP^（2nd）（~3E） between the above twin SPs is the result of the C_（3v） symmetry Jahn–Teller coupling within the branching space. Further kinetic calculations are performed with the canonical unified statistical theory method with the temperature ranging from 298 K to 1000 K. The rate constants are also reported. The present work reveals the reaction mechanism of hydrogen-abstraction by the O（~3P） from methane, and develops a better understanding for the role of SPs. In addition, a comparison of the reactions of O（~3P） with methane through different channels allows a molecule-level discussion of the reactivity and mechanism of the title reaction.
