Adsorption characteristics of CO2 by coal are an important reservoir parameter to determine the CO2 storage capacity of the coal seam. The Langmuir isotherm adsorption model is commonly used to describe the isothermal adsorption line of coal. However, we cannot predict the CO2 adsorption capacity at other temperatures by using the Langmuir model based on the experimental data at a fixed temperature. This paper analyzes the ε-V ad adsorption characteristic curves of three coal samples over a range of temperatures and pressures. The study demonstrates that the adsorption characteristic curves of CO2 gas are independent of temperature and depend mainly on the dispersion force between coal and the CO2 molecules. In addition, the adsorption potential of CO2 gas has a negative correlation with the volume of the adsorbed phase. Hence, the CO2 adsorption characteristic curve of coal conforms to the logarithmic function. Based on the adsorption potential theory, the prediction model of CO2 adsorption by coal is derived. The deviation analysis from measured data shows that the average relative deviation of the three coal samples is ∼5%, and the prediction results are accurate and reliable. Under different temperature and pressure conditions of the three coal samples, the results from the prediction model of CO2 adsorption by coal and the Langmuir model have a strong correlation with the experimental results. In comparison with the Langmuir model, the prediction model of CO2 adsorption by coal can predict the adsorption capacity under different temperature and pressure conditions. Hence, it has a wide range of applications when compared to that of the Langmuir model. In practical applications, better results are achieved with a significant reduction in experimental time and labor.The coal and gas outbursts are recognized as a worldwide difficulty, and there is still ample research space in this field, especially on the mechanical mechanism of outbursts. The main purpose of this paper is to attempt to reveal the outburst mechanism as fully as possible from the point of view of mechanics. https://www.selleckchem.com/products/4u8c.html In this paper, a mechanical model on coal and gas outbursts including the governing equations of gas desorption-seepage, the stress state in the coal sample, and the criteria of coal sample failure and outburst evolution is put forward according to the porous media seepage theory and elastic theory. Based on the proposed model, the variation and distribution of the gas state and stress state in the coal sample in the outburst are analyzed quantitatively and a series of detailed discussions are conducted in terms of the in-situ stress, gas pressure, and the physical characteristics of coal in outbursts. The results of theoretical analysis and numerical simulation show that the stress concentration in the front of the outburst cavity is the main reason for the failure of the coal sample in this area, and then, the drag force caused by gas flow provides energy for the movement of the crushed coal sample, which leads to the outburst cavity expansion and the increase of stress concentration factor. The end of the outburst is because the gas velocity is less than the threshold friction velocity of the crushed coal sample. Additionally, the outburst strength increases with the increase of the vertical in-situ stress and initial gas pressure and decreases with the increase of the internal friction angle and cohesion of coal.Three 1D coordination polymers (CPs) [M(pdca)(H2O)2] n (M = Zn, Cd, and Co; 1-3), and a 3D coordination framework [(CH3)2NH2][CuK(2,3-pdca)(pa)(NO3)2] n (4) (2,3-pdca = pyridine-2,3-dicarboxylate and pa = picolinic acid), have been synthesized adopting a solvothermal reaction strategy. The CPs have been thoroughly characterized using various spectral techniques, that is, elemental analyses, FT-IR, TGA, DSC, UV/vis, and luminescence. Structural information on 1-4 was obtained by PXRD and X-ray single-crystal analyses, whereas morphological insights were attained through FESEM, AFM, EDX, HRTEM, and BET surface area analyses. Roughness parameters were calculated from AFM analysis, whereas dimensions of small domains and interplanar spacing were defined with the aid of HRTEM. CPs 1-3 are 1D isostructural networks, whereas 4 is a 3D framework. Moreover, 1-4 display moderate luminescence at rt. In addition, 1-4 have been applied as economic and efficient porous catalysts for the Knoevenagel condensation reaction and C-H bond activation under mild conditions with good yields (95-98 and 97-99%), respectively. Notably, 1-3 can be reused up to seven cycles, whereas 4 can be reused up to five catalytic cycles with retained catalytic efficiency. Relative catalytic efficacy toward the Knoevenagel condensation reaction follows in the order 2 > 1 > 3 > 4, whereas 2 > 4 > 1 > 3 for C-H activation. The present result demonstrates synthetic, structural, optical, morphological, and catalytic aspects of 1-4.The three major lignocellulose components can be transformed into various biomass-derived platform fuels, chemicals, and materials upon pretreatment and chemical upgrading. Lignocellulose pretreatment is an important step to obtain an eco-friendly, economical, and effective biomass utilization process. The combination of microwave heating and hydrotropic pretreatment is considered as a green method of lignocellulose pretreatment. Experimental data and two mechanistic kinetic models of microwave-assisted pretreatment of rice straw are presented. Here, the use of urea solution as the hydrotropic agent was examined to facilitate the degradation of three major lignocellulose components. The first kinetic model assumes that the soluble lignin does not undergo condensation, while the second one assumes that part of the soluble lignin condenses to a solid product. The mechanistic models were validated with a series of experimental data obtained from microwave-assisted hydrotropic pretreatment of rice straw. The resu-assisted hydrotropic pretreatment was able to produce higher crystallinity and thermally stable cellulosic biomass.Two-dimensional (2D) ****compounds possess rich allotropic structures with many applications. Obtaining new 2D **** structures is highly desirable due to the novel applications of three-dimensional (3D) **** in protections. In this work, we proposed a new family of 2D **** from the first-principles calculations. Distinct from previous observations, this family of 2D **** consists of bonded 2D **** bilayers. Six different types of bilayers with distinct bonded structures are found. The phonon spectrum calculations and ab initio molecular dynamics simulations at room temperature demonstrate their dynamic and thermal stabilities. Low formation energies suggest the high possibility of realizing such structures in experiments. Rich electronic structures are found, and the predicted Young's moduli are even higher than those of the previous ones. It is revealed that the unique electronic and mechanical properties are rooted in the bonding structures, indicating the prompting applications of this family of 2D **** materials in photovoltaics, nanoelectronics, and nanomechanics.
Adsorption characteristics of CO2 by coal are an important reservoir parameter to determine the CO2 storage capacity of the coal seam. The Langmuir isotherm adsorption model is commonly used to describe the isothermal adsorption line of coal. However, we cannot predict the CO2 adsorption capacity at other temperatures by using the Langmuir model based on the experimental data at a fixed temperature. This paper analyzes the ε-V ad adsorption characteristic curves of three coal samples over a range of temperatures and pressures. The study demonstrates that the adsorption characteristic curves of CO2 gas are independent of temperature and depend mainly on the dispersion force between coal and the CO2 molecules. In addition, the adsorption potential of CO2 gas has a negative correlation with the volume of the adsorbed phase. Hence, the CO2 adsorption characteristic curve of coal conforms to the logarithmic function. Based on the adsorption potential theory, the prediction model of CO2 adsorption by coal is derived. The deviation analysis from measured data shows that the average relative deviation of the three coal samples is ∼5%, and the prediction results are accurate and reliable. Under different temperature and pressure conditions of the three coal samples, the results from the prediction model of CO2 adsorption by coal and the Langmuir model have a strong correlation with the experimental results. In comparison with the Langmuir model, the prediction model of CO2 adsorption by coal can predict the adsorption capacity under different temperature and pressure conditions. Hence, it has a wide range of applications when compared to that of the Langmuir model. In practical applications, better results are achieved with a significant reduction in experimental time and labor.The coal and gas outbursts are recognized as a worldwide difficulty, and there is still ample research space in this field, especially on the mechanical mechanism of outbursts. The main purpose of this paper is to attempt to reveal the outburst mechanism as fully as possible from the point of view of mechanics. https://www.selleckchem.com/products/4u8c.html In this paper, a mechanical model on coal and gas outbursts including the governing equations of gas desorption-seepage, the stress state in the coal sample, and the criteria of coal sample failure and outburst evolution is put forward according to the porous media seepage theory and elastic theory. Based on the proposed model, the variation and distribution of the gas state and stress state in the coal sample in the outburst are analyzed quantitatively and a series of detailed discussions are conducted in terms of the in-situ stress, gas pressure, and the physical characteristics of coal in outbursts. The results of theoretical analysis and numerical simulation show that the stress concentration in the front of the outburst cavity is the main reason for the failure of the coal sample in this area, and then, the drag force caused by gas flow provides energy for the movement of the crushed coal sample, which leads to the outburst cavity expansion and the increase of stress concentration factor. The end of the outburst is because the gas velocity is less than the threshold friction velocity of the crushed coal sample. Additionally, the outburst strength increases with the increase of the vertical in-situ stress and initial gas pressure and decreases with the increase of the internal friction angle and cohesion of coal.Three 1D coordination polymers (CPs) [M(pdca)(H2O)2] n (M = Zn, Cd, and Co; 1-3), and a 3D coordination framework [(CH3)2NH2][CuK(2,3-pdca)(pa)(NO3)2] n (4) (2,3-pdca = pyridine-2,3-dicarboxylate and pa = picolinic acid), have been synthesized adopting a solvothermal reaction strategy. The CPs have been thoroughly characterized using various spectral techniques, that is, elemental analyses, FT-IR, TGA, DSC, UV/vis, and luminescence. Structural information on 1-4 was obtained by PXRD and X-ray single-crystal analyses, whereas morphological insights were attained through FESEM, AFM, EDX, HRTEM, and BET surface area analyses. Roughness parameters were calculated from AFM analysis, whereas dimensions of small domains and interplanar spacing were defined with the aid of HRTEM. CPs 1-3 are 1D isostructural networks, whereas 4 is a 3D framework. Moreover, 1-4 display moderate luminescence at rt. In addition, 1-4 have been applied as economic and efficient porous catalysts for the Knoevenagel condensation reaction and C-H bond activation under mild conditions with good yields (95-98 and 97-99%), respectively. Notably, 1-3 can be reused up to seven cycles, whereas 4 can be reused up to five catalytic cycles with retained catalytic efficiency. Relative catalytic efficacy toward the Knoevenagel condensation reaction follows in the order 2 > 1 > 3 > 4, whereas 2 > 4 > 1 > 3 for C-H activation. The present result demonstrates synthetic, structural, optical, morphological, and catalytic aspects of 1-4.The three major lignocellulose components can be transformed into various biomass-derived platform fuels, chemicals, and materials upon pretreatment and chemical upgrading. Lignocellulose pretreatment is an important step to obtain an eco-friendly, economical, and effective biomass utilization process. The combination of microwave heating and hydrotropic pretreatment is considered as a green method of lignocellulose pretreatment. Experimental data and two mechanistic kinetic models of microwave-assisted pretreatment of rice straw are presented. Here, the use of urea solution as the hydrotropic agent was examined to facilitate the degradation of three major lignocellulose components. The first kinetic model assumes that the soluble lignin does not undergo condensation, while the second one assumes that part of the soluble lignin condenses to a solid product. The mechanistic models were validated with a series of experimental data obtained from microwave-assisted hydrotropic pretreatment of rice straw. The resu-assisted hydrotropic pretreatment was able to produce higher crystallinity and thermally stable cellulosic biomass.Two-dimensional (2D) B-C compounds possess rich allotropic structures with many applications. Obtaining new 2D B4C3 structures is highly desirable due to the novel applications of three-dimensional (3D) B4C3 in protections. In this work, we proposed a new family of 2D B4C3 from the first-principles calculations. Distinct from previous observations, this family of 2D B4C3 consists of bonded 2D B4C3 bilayers. Six different types of bilayers with distinct bonded structures are found. The phonon spectrum calculations and ab initio molecular dynamics simulations at room temperature demonstrate their dynamic and thermal stabilities. Low formation energies suggest the high possibility of realizing such structures in experiments. Rich electronic structures are found, and the predicted Young's moduli are even higher than those of the previous ones. It is revealed that the unique electronic and mechanical properties are rooted in the bonding structures, indicating the prompting applications of this family of 2D B4C3 materials in photovoltaics, nanoelectronics, and nanomechanics.
0 Yorumlar 0 hisse senetleri 18 Views 0 önizleme
Sponsorluk