CO偶联反应中Pd/α-Al_2O_3活性组分随孔径变化的数值模拟

Numeral simulation of supports' pore size impact on the active palladium distribution in Pd/α-Al_2O_3 catalysts for CO coupling reaction

在无梯度反应器中,测定了CO偶联制备草酸二甲酯(DMO)反应在负载型催化剂Pd/α-Al_2O_3内的颗粒动力学方程。基于颗粒动力学方程式、菲克扩散定律和傅里叶传热定律,建立了单颗粒催化剂内的扩散动力学数学模型。使用Matlab做数值分析,模拟得到单颗粒内各组分含量随载体孔径变化沿颗粒径向浓度分布情况。数值模拟结果显示,对于大孔径载体而言,活性组分在均匀分布时对载体有着更高的利用率;而蛋壳型分布的Pd/α-Al_2O_3使用范围,是在内扩散阻力较大的努森扩散以及更小的构型扩散时,即载体孔径数量级处于10nm或者更小的范围内。

In a no-gradient reactor, the particle dynamics of the synthesis of dimethyl oxalate（DMO） by CO coupling over the supported catalyst Pd/α-Al2O3 was determined. According to the single particle dynamics, Fick diffusion law and Fourier law for heat transfer, the diffusion kinetics model for the single particle catalyst was then constructed. Numerical analysis by Matlab was used to simulate the concentration variation of components along the radial direction with the change of supports ＇ pore size. The results show that, for the macro-porous α-alumina, a uniform distribution of the active palladium leads to a higher catalyst utilization rate, while the egg-shell distribution palladium is recommended in the case of Knudsen diffusion or configuration diffusion who possess a relatively high internal diffusion resistance, which means the order of magnitude of supports ＇ pore size attains to 10 nm or much smaller.