Abstract:

With trimethylphosphine (TMP) as the precursor, ZSM-5 was firstly modified to improve its hydrothermal stability, and then subject to impregnation of Ga₂O₃ or ZnO to prepared phosphorus and metal oxide modified ZSM-5 zeolites. The statuses of metal oxides and phosphorus species, as well as ZSM-5 matrix and their interaction were systematically investigated by XRD, MAS NMR, NH₃-TPD and Py-FTIR spectroscopy. The cleavage of n-tetradecane was used as a probe reaction to study the effect of phosphorus and metal oxide compound modification on the catalytic cracking performance of ZSM-5. Via such trimethylphosphine and metal oxide modification, more acids were preserved to show better cracking performance, as well as higher light olefin yield and selectivity with lower coke yield.

Key words: catalytic cracking, ZSM-5, hydrothermal stability, P modification, trimethylphosphine, co-modifiction

摘要：

以三甲基膦（TMP）为前体对ZSM-5分子筛进行磷改性，以提升其水热稳定性，然后再分别通过等体积浸渍法引入Ga₂O₃或ZnO，制备得到磷和金属氧化物复合改性的ZSM-5分子筛。利用X射线衍射（XRD）、固体核磁（MAS NMR）、氨程序升温脱附（NH₃-TPD）以及吡啶吸附傅里叶变换红外光谱（Py-FTIR）等表征手段系统地研究了磷和金属氧化物复合改性对ZSM-5分子筛的物化性质、P和Al相互作用以及酸性的影响。并以正十四烷裂解为探针反应，研究磷和金属氧化物复合改性对ZSM-5分子筛催化裂解性能的影响。研究结果表明以三甲基膦为前体对ZSM-5分子筛改性，再引入金属氧化物的复合改性方式制备的催化裂解催化剂不仅具有较高的酸性保留度，具有较高的催化裂解活性，也同时保留了金属氧化物中心的脱氢作用，从而提升了C₂⁼~C₄⁼收率及选择性，同时降低了积炭的生成。

关键词: 催化裂解, ZSM-5, 水热稳定性, 磷改性, 三甲基膦, 复合改性