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

Catalytic Activity of Pt Modified Hierarchical ZSM-5 Catalysts in Benzene Alkylation with Methanol

“…In addition, although many literatures [29][30][31][32] had reported that Pt/ZSM-5 could catalyze the hydrogenation of aromatic hydrocarbons, the hydrogenation of benzene was not occurred due to that the high temperature and low pressure used in this work was unfavorable for this reaction. As mentioned earlier, calcinations could influence the size of Pt metal particle, which in turn influenced the hydrogenation activity of Pt [20]. When the supported precursor was calcined in air and then reduced in hydrogen (calcination method), aggregated large particles were observed in TEM (Fig.…”

“…Schmidt had reported that the coke distribution for the microporous ZSM-5 showed a gradient over the particle and the carbonaceous species mainly accumulated in the outer particle layers which lead to the rapid deactivation of the catalyst, while hierarchical ZSM-5 showed a homogeneous distribution of coke residuals over the whole particle [28]. The other reason relates to the coke formation from alkenes by polymerization, so the decease of alkenes could reduce the coke deposit rate [20]. In addition, comparing the TG-DTA profiles (Fig.…”

“…Consequently, combining the suppressing ability of Pt towards the ethylbenzene formation and the catalytic advantages of hierarchical ZSM-5 would be of great interests. On the other hand, it is well known that calcination at high temperatures in air causes Pt particle sintering, which decreases the dispersion of Pt and further influences its hydrogenation activity [20,21]. Direct reduction of the supported Pt precursor in hydrogen flow could reduce the change of Pt particle caused by calcinations [22].…”

A Facile Strategy to Prepare Shaped ZSM-5 Catalyst with Enhanced para-Xylene Selectivity and Stability for Toluene Methylation

“…The first weight loss was in the range of 25 to 300 o C, which was attributed to desorption of organics and water adsorbed on catalyst surface [15,33]. The second weight loss was in the range of 300 to 800 o C, which was ascribed to the decomposition of coke species deposited on catalyst surface [15,33]. Quantification of the coke content on spent Z5-atp was much less than Z5-bo illustrated that attapulgite inhibited the rate of coke formation during toluene methylation.…”

Preparation of an MCM‐22/Hydrotalcite Framework Composite and Its Catalytic Application

“…MCM‐22 is an anionic framework zeolite material consisting of two non‐intersecting pore systems with thin‐plate morphology and possessing a large amount of supercages on the external packet (Scheme ) . Among the various zeolites, ZSM‐5 and MCM‐22 have medium pores and are known as promising shape‐selective catalysts for the selective preparation of p ‐xylene by various processes such as toluene alkylation, disproportionation of toluene, and m ‐xylene isomerization . In recent decades, significant improvement of C 8 selectivity was observed in toluene alkylation through different processes such as dealumination, substitution of metal ions, impregnation of oxides, and preparation of composites with MCM‐22 or ZSM‐5 materials .…”