噻吩在稀土离子改性Y型分子筛上吸附与催化转化研究

以NaY、HY、液相Ce离子交换改性Y分子筛(L-CeY)和稀土离子改性超稳Y分子筛(HRSY-3)为研究对象,运用XRD、N₂吸附、NH₃-TPD和Py-FTIR表征样品的物化性能;采用原位红外光谱技术与程序升温脱附-同步质谱检测联用技术(TPD-MS)研究噻吩在活性中心上的吸附及催化转化行为.结果表明,稀土离子改性不改变分子筛晶体的基本结构但改变其精细结构,并形成一定的介孔,同时降低分子筛强酸位的强度,并生成与稀土离子物种有关的弱L酸位.REY与HY均可通过B酸中心的质子化作用活化噻吩,而稀土离子物种促进氢转移反应及低聚反应的进行,进而利于噻吩裂化反应的进行.

Adsorption and catalytic conversion of thiophene on Y-type zeolites modified with rare-earth metal ions

Rare earth metal modified Y zeolites (L-CeY) and USY zeolites (HRSY-3) were characterized by XRD, N₂ adsorption, NH₃-TPD, and in-situ Py-FTIR; the adsorption and catalytic conversion behavior of thiophene on the modified zeolites were investigated by using the in situ FT-IR combined with TG-MS analysis. The results indicated that the original crystal structures of the zeolites remain unchanged after the modification with the rare earth metal ions; however, the modification results in the formation of partial mesoporous structure and weak Lewis acid sites related to the rare-earth ion species as well as certain decrease of the acidic strength of the strong acid sites. Thiophene molecules can be activated via protonization upon the Brönsted acid sites of the USY and HY zeolites; however, the rare earth metal ions are able to promote the hydrogen transfer and oligomerization reactions, which can then enhance the catalytic cracking of thiophene reactions.