Accurate description of the adsorption process of reactants on metal surfaces from theory is crucial for mechanistic understanding of activity and selectivity of metal catalysts, but it remains challengeable for the n...Accurate description of the adsorption process of reactants on metal surfaces from theory is crucial for mechanistic understanding of activity and selectivity of metal catalysts, but it remains challengeable for the nowadays first-principles theory due to the lack of proper exchange-correlation functional describing the distinct interactions involved. We studied here the potential energy surfaces of ethylene adsorption on Ag(111), Rh(111) and Ir(111) using density functional theory calculations and (meta)-GGA functional including PBE, BEEF-vdW, SCAN, and SCAN+rVV10. For ethylene adsorption on noble metal Ag(111), it is found that BEEF-vdW, SCAN and SCAN+rVV10 predict the presence of the physisorption states only. For Rh(111), both SCAN and SCAN+rVV10 find that there is a precursor physisorption state before the chemisorption state. In contrast, there is no precursor state found based on potential energy surfaces from BEEF-vdW and PBE. Whereas for Ir(111), BEEF-vdW predicts the existence of a rather shallow precursor physisorption state, in addition to the chemisorption state. Irrespective to the transition metals considered, we find that SCAN+rVV10 gives the strongest binding strength, followed by SCAN, and PBE/BEEF-vdW, accordingly. The present work highlights great dependence of potential energy surface of ethylene adsorption on transition metal surfaces and exchange-correlation functionals.展开更多
The paper presents a Monte Carlo simulation to study the adsorption characteristics of methane molecule on coal slit pores from different aspects.Firstly,a physical model of adsorption and desorption of methane molecu...The paper presents a Monte Carlo simulation to study the adsorption characteristics of methane molecule on coal slit pores from different aspects.Firstly,a physical model of adsorption and desorption of methane molecules on micropores was established.Secondly,a grand canonical ensemble was introduced as the Monte Carlo simulation system.Thirdly,based on the model and system,the molecule simulation program was developed with VC++6.0 to simulate the isothermal adsorption relationship between the amount of molecule absorption and the factors affecting it.Lastly,the numerically simulated results were compared with measured results of adsorption coal samples of two different coal mines with a laboratory gas absorption instrument.The results show that the molecule simulations of the adsorption constants,the adsorption quantity,and the isothermal adsorption curve at the same and different coal temperatures were in good agreement with those measured in the experiments,indicating that it is feasible to use the established model and the Monte Carlo molecule simulation to study the adsorption characteristics of methane molecules in coal.展开更多
The adsorption isotherms of four activated carbons (Norit Rill, Chemviron BPL, Monolit, and Ambersorb-572) have been examined by nitrogen adsorption at 77.5 K. A method for adsorption potential distribution calculat...The adsorption isotherms of four activated carbons (Norit Rill, Chemviron BPL, Monolit, and Ambersorb-572) have been examined by nitrogen adsorption at 77.5 K. A method for adsorption potential distribution calculation has been proposed based on the adsorption isotherms. This distribution provides information about possible changes in the Gibbs free energy caused by the energetic and geometrical heterogeneities of an activated carbon as well as by the adsorbate-related entropic effects. The general character of the adsorption potential distribution is clearly visible by its simple relation to the micropore and mesopore distribution,展开更多
Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were inves...Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.展开更多
Because of the smallness of Estonia, its main source of economic growth is export, i.e. successful sales in the world market. It is necessary to shift from branches, activities and value chains where it is difficult t...Because of the smallness of Estonia, its main source of economic growth is export, i.e. successful sales in the world market. It is necessary to shift from branches, activities and value chains where it is difficult to increase value added, to more profitable and promising ones. The present economic situation provides for this an exceptionally good chance. All kinds of development, international relocation of production and reallocation of economic power in the world are gathering speed. It is necessary to rapidly find an opportunity in the "declining" market, a profitable niche. Manufacturing entrepreneurs and executive managers have for several years already been complaining of shortage of workforce that hinders them carrying out new business plans, increasing production and exports. Increased supply of workforce dismissed from construction is an opportunity for the forced development of the manufacturing export sector and sharp increase in exports.展开更多
基金supported by the National Key R&D Program of China (No.2017YFB0602205 and No.2018YFA0208603)the National Natural Science Foundation of China (No.91645202)the Chinese Academy of Sciences (No.QYZDJ-SSW-SLH054)
文摘Accurate description of the adsorption process of reactants on metal surfaces from theory is crucial for mechanistic understanding of activity and selectivity of metal catalysts, but it remains challengeable for the nowadays first-principles theory due to the lack of proper exchange-correlation functional describing the distinct interactions involved. We studied here the potential energy surfaces of ethylene adsorption on Ag(111), Rh(111) and Ir(111) using density functional theory calculations and (meta)-GGA functional including PBE, BEEF-vdW, SCAN, and SCAN+rVV10. For ethylene adsorption on noble metal Ag(111), it is found that BEEF-vdW, SCAN and SCAN+rVV10 predict the presence of the physisorption states only. For Rh(111), both SCAN and SCAN+rVV10 find that there is a precursor physisorption state before the chemisorption state. In contrast, there is no precursor state found based on potential energy surfaces from BEEF-vdW and PBE. Whereas for Ir(111), BEEF-vdW predicts the existence of a rather shallow precursor physisorption state, in addition to the chemisorption state. Irrespective to the transition metals considered, we find that SCAN+rVV10 gives the strongest binding strength, followed by SCAN, and PBE/BEEF-vdW, accordingly. The present work highlights great dependence of potential energy surface of ethylene adsorption on transition metal surfaces and exchange-correlation functionals.
基金supported by the Industrial Research Project in Guizhou Science and Technology Bureau of China (GY(2011)No.3012)International Cooperation Projects in Guizhou Science and Technology Bureau of China (G(2009)No.700111)
文摘The paper presents a Monte Carlo simulation to study the adsorption characteristics of methane molecule on coal slit pores from different aspects.Firstly,a physical model of adsorption and desorption of methane molecules on micropores was established.Secondly,a grand canonical ensemble was introduced as the Monte Carlo simulation system.Thirdly,based on the model and system,the molecule simulation program was developed with VC++6.0 to simulate the isothermal adsorption relationship between the amount of molecule absorption and the factors affecting it.Lastly,the numerically simulated results were compared with measured results of adsorption coal samples of two different coal mines with a laboratory gas absorption instrument.The results show that the molecule simulations of the adsorption constants,the adsorption quantity,and the isothermal adsorption curve at the same and different coal temperatures were in good agreement with those measured in the experiments,indicating that it is feasible to use the established model and the Monte Carlo molecule simulation to study the adsorption characteristics of methane molecules in coal.
基金Natural Science Foundation of Guangdong Province (No. 36566)
文摘The adsorption isotherms of four activated carbons (Norit Rill, Chemviron BPL, Monolit, and Ambersorb-572) have been examined by nitrogen adsorption at 77.5 K. A method for adsorption potential distribution calculation has been proposed based on the adsorption isotherms. This distribution provides information about possible changes in the Gibbs free energy caused by the energetic and geometrical heterogeneities of an activated carbon as well as by the adsorbate-related entropic effects. The general character of the adsorption potential distribution is clearly visible by its simple relation to the micropore and mesopore distribution,
基金the National Natural Science Foundation of China (No.29976031), the Collaboration Project Foundation of Tianjin University and Nankal University, and the Key Project Foundation of Tianjin (No.0331810112).
文摘Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.
文摘Because of the smallness of Estonia, its main source of economic growth is export, i.e. successful sales in the world market. It is necessary to shift from branches, activities and value chains where it is difficult to increase value added, to more profitable and promising ones. The present economic situation provides for this an exceptionally good chance. All kinds of development, international relocation of production and reallocation of economic power in the world are gathering speed. It is necessary to rapidly find an opportunity in the "declining" market, a profitable niche. Manufacturing entrepreneurs and executive managers have for several years already been complaining of shortage of workforce that hinders them carrying out new business plans, increasing production and exports. Increased supply of workforce dismissed from construction is an opportunity for the forced development of the manufacturing export sector and sharp increase in exports.