VGO分子在FAU分子筛中的扩散研究

应用分子模拟技术计算了VGO模型化合物中刚性基团的尺寸和VGO分子尺寸,利用分子动力学模拟在800K催化裂化反应温度下VGO分子在FAU型分子筛内的扩散过程,并通过计算扩散穿透距离,研究不同类型VGO分子在FAU型分子筛内扩散能力的差异。结果表明:分子中刚性基团的尺寸和VGO分子碳链长度是影响VGO分子在FAU型分子筛内扩散能力的主要因素;直链烷烃的链长增加,烃分子在扩散时易发生卷曲,扩散能力降低;环烷烃、芳烃环数的增加或分子中含有支链会增加烃分子刚性基团的尺寸,进而降低烃分子的扩散能力;烃分子与多环芳烃混合进行扩散,难扩散的多环芳烃占据分子筛孔道,堵塞孔道而降低易扩散烃分子的扩散能力。

DIFFUSION STUDY OF VGO IN FAU ZEOLITE SEIEVE

The dimensions of the rigid groups in the VGO model compounds and the dimensions of VGO molecules are calculated by using molecular simulation techniques. Dynamics methods were applied to investigate the diffusion process of VGO compounds at 800 K in FAU zeolite. The diffusibility difference of different VGO model compounds was studied by calculated penetration distance. The results indicated that the carbon chain length of VGO molecule and the dimensions of rigid group are the main factors that influence the diffusion ability of VGO in FAU zeolite. The increase in chain length leads to a lower diffusion ability due to the crimp of VGO molecules. The increase in ring number in naphthene and aromatics or the branched chain in the molecule increases the minimum cross section size of the molecular rigid group of the hydrocarbon molecules， thus reducing the diffusion ability of the hydrocarbon molecules. When the hydrocarbon mixed with polycyclic aromatics as a model， the diffusion ability of the easy diffused molecules is lowered due to pore block by polycyclic aromatics.