Single-event microkinetic(SEMK) model of the catalytic cracking of methylcyclohexane admixed with 1-octene over REUSY zeolites at 693 K—753 K in the absence of coke formation is enhanced. To keep consistency with the...Single-event microkinetic(SEMK) model of the catalytic cracking of methylcyclohexane admixed with 1-octene over REUSY zeolites at 693 K—753 K in the absence of coke formation is enhanced. To keep consistency with the wellknown carbenium ion chemistry, hydride transfer forming and consuming allylic carbenium ions in the aromatization of cycloparaffins are further investigated and differentiated. The reversibility of endocyclic β-scission and cyclization reactions is refined by accounting explicitly for the reacting olefins and resulting cycloparaffins in the corresponding thermodynamics. 24 activation energies for the reactions involved in the cracking of cycloparaffins are obtained by the regression of 15 sets of experimental data upon taking the resulting 37 main cracking products, i. e., responses into account. The enhanced SEMK model can adequately describe the catalytic behavior of 37 main products with conversion and temperature.展开更多
The developed SEMK model is used to provide an insight into the contribution of individual reactions in the cracking of methylcyclohexane as well as the site coverage by various carbenium ions. The preferred reaction ...The developed SEMK model is used to provide an insight into the contribution of individual reactions in the cracking of methylcyclohexane as well as the site coverage by various carbenium ions. The preferred reaction pathways for the conversion of methylcyclohexane are hydride transfer reactions followed by PCP-isomerizations, deprotonation and endocyclic β-scission, accounting for 61%, 22% and 12% of its disappearance, respectively, at 693 K and 30% conversion of methylcyclohexane. Protolysis plays a minor role in the cracking of methylcyclohexane. Once cyclic diolefins are formed, all of them can be instantaneously transformed to aromatics, which are easily interconverted via disproportionation. Judging from the carbenium ion concentrations it is evident that, at the investigated operating conditions, less than 5% of the acid sites are covered by carbenium ions, less than 2% of which corresponds to cyclic type species including allylic ones.展开更多
在非线性岩土/石力学问题中，网格质量是影响计算结果的一个重要因素.本文分析了弥散裂缝模型水力压裂数值求解方法中单元高宽比（AR）对计算结果的影响.材料的弹性部分采用线弹性和多孔弹性两种本构关系，屈服和破坏准则采用 Drucker -...在非线性岩土/石力学问题中，网格质量是影响计算结果的一个重要因素.本文分析了弥散裂缝模型水力压裂数值求解方法中单元高宽比（AR）对计算结果的影响.材料的弹性部分采用线弹性和多孔弹性两种本构关系，屈服和破坏准则采用 Drucker -Prager（DP）和 Mohr -Coulomb（MC）两种模型.通过综合分析，无论采用何种本构关系，均存在网格敏感性问题.当裂缝的传播方向已知时，可以将单元的 AR 值控制在2.8~8.0之间，以避免弥散裂缝模型的网格敏感性问题，并得到稳定的结果.如果裂缝传播方向未知，建议使用线弹性本构关系和 DP 或者 MC 塑性模型，同时建议 AR 的取值为1.0.展开更多
基金financial support from the China Scholarship Councilthe Long Term Structural Methusalem Funding by the Flemish Government
文摘Single-event microkinetic(SEMK) model of the catalytic cracking of methylcyclohexane admixed with 1-octene over REUSY zeolites at 693 K—753 K in the absence of coke formation is enhanced. To keep consistency with the wellknown carbenium ion chemistry, hydride transfer forming and consuming allylic carbenium ions in the aromatization of cycloparaffins are further investigated and differentiated. The reversibility of endocyclic β-scission and cyclization reactions is refined by accounting explicitly for the reacting olefins and resulting cycloparaffins in the corresponding thermodynamics. 24 activation energies for the reactions involved in the cracking of cycloparaffins are obtained by the regression of 15 sets of experimental data upon taking the resulting 37 main cracking products, i. e., responses into account. The enhanced SEMK model can adequately describe the catalytic behavior of 37 main products with conversion and temperature.
基金the financial support from the China Scholarship Councilthe Long Term Structural Methusalem Funding by the Flemish Government
文摘The developed SEMK model is used to provide an insight into the contribution of individual reactions in the cracking of methylcyclohexane as well as the site coverage by various carbenium ions. The preferred reaction pathways for the conversion of methylcyclohexane are hydride transfer reactions followed by PCP-isomerizations, deprotonation and endocyclic β-scission, accounting for 61%, 22% and 12% of its disappearance, respectively, at 693 K and 30% conversion of methylcyclohexane. Protolysis plays a minor role in the cracking of methylcyclohexane. Once cyclic diolefins are formed, all of them can be instantaneously transformed to aromatics, which are easily interconverted via disproportionation. Judging from the carbenium ion concentrations it is evident that, at the investigated operating conditions, less than 5% of the acid sites are covered by carbenium ions, less than 2% of which corresponds to cyclic type species including allylic ones.
文摘在非线性岩土/石力学问题中，网格质量是影响计算结果的一个重要因素.本文分析了弥散裂缝模型水力压裂数值求解方法中单元高宽比（AR）对计算结果的影响.材料的弹性部分采用线弹性和多孔弹性两种本构关系，屈服和破坏准则采用 Drucker -Prager（DP）和 Mohr -Coulomb（MC）两种模型.通过综合分析，无论采用何种本构关系，均存在网格敏感性问题.当裂缝的传播方向已知时，可以将单元的 AR 值控制在2.8~8.0之间，以避免弥散裂缝模型的网格敏感性问题，并得到稳定的结果.如果裂缝传播方向未知，建议使用线弹性本构关系和 DP 或者 MC 塑性模型，同时建议 AR 的取值为1.0.
