Abstract
An alkaline treatment is employed for tailoring a commercial H-ZSM-5 to produce a catalyst for the synthesis of pyridine and picolines. The most significant consequence of the alkaline treatment was desilication. However, it is accompanied by extraction of aluminum and formation of extra-framework aluminum (Alef) and amorphous alumina. Slit-shaped intracrystaline mesopores and macropores form. Because of the decrease in the Si/Al ratio in the zeolite framework and the formation of Alef and amorphous alumina, the number of strong acid sites decreases and that of weak acid sites increases. The ratio of Lewis acids to Brönsted acids (L/B) also increases. We note that the induced hierarchical pores and the change of acid strength distribution increase the stability of the catalyst, and the increased L/B causes an increase in the initial yield and comparative selectivity for pyridine and a decrease in those properties for 3-picoline. Coking leads to a gradual deactivation and affects product selectivity.
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