摘要
用色谱-质谱研究了结焦HY沸石分子筛上焦的溶剂可溶部分的分子性质,用程序升温氧化-色谱装置测量了焦中各物种的C/H比。结果表明,在结焦HY外表面上的焦含有较多的苯和萘的烷基衍生物,而内表面的焦富集了较多的多核芳烃。这意味着由于HY分子筛骨架的空间限制,在超笼和孔道中烷基芳烃极易发生环化和脱氢反应。孔内焦较难烧掉,这可能与高C/H比的多核芳烃分子残余物的性质有关;孔口结焦阻碍了氧的扩散进入孔内,这可能是孔内焦难烧的另一原因。
The molecular nature of the Solvent-extractable portion of coke deposited on HY zeolite was studied by combined chromatographic and mass spectrometric technique (GC-MS). The C/H ratio of the species on coked HY was measured by TPO-GC equipment. The results show that the alkyl derivatives of benzene and naphthalene are the major species on the outer Surface, while the polynuclear aromatics are abundant in supercage of coked HY zeolite. It means that the cyclization and dehydrogenalion of alkyl derivatives of aromatic occur easily in the supercage due to the steric restrictions of the framework of HY zeolite. Burning off the coke deposited in supercage is rather difficult. It may be caused by the nature of the polynuclear aromatics residues with high C/H ratio. The coke deposited on pore opening plays a key role in hampering the diffusion of oxygen into the channel. It is perhaps the another reason that burning off the coke deposited on the wall of the channel and Supercage is difficult.
