Effect of Pt on stability of nano-scale ZSM-5 catalyst for toluene alkylation with methanol into p-xylene

Shape-selective methylation of toluene (T) with methanol (M) was carried out in continuous flow fixed-bed reactor over Pt-modified nano-scale HZSM-5 catalysts, and excellent stability was obtained. Even after 500 h on stream, toluene conversion of 22.0–23.0% was achieved simultaneously with the para-selectivity of >98%. The presence of Pt on the modified nano-scale HZSM-5 solves the apparent paradox of high para-selectivity and low stability. Catalysts were characterized by using X-ray diffraction (XRD), temperature programmed desorption of ammonia (NH3-TPD), Pyridine IR (Py-IR), TG-SDTA, scanning electron microscope (SEM), etc. The results show that significant enhancement in stability over Pt-modified nano-scale HZSM-5 catalysts is mainly due to good hydrogenation properties of Pt particles.