Comparative Study of Catalytic Performance of Nanoporous Pt -(Re, Sn)/HZSM -۵-HMS and Pt/(۱۳X, HY & HZSM -۵)-HMS in n -Heptane Isomerization

Catalytic isomerization of n-heptane is an important process in petroleum refining to increase octane number without increasing harmful aromatic compounds. In this study, two catalyst systems, Pt-(Re, Sn)/HZSM-۵-HMS and Pt/(۱۳X, HY & HZSM-۵)-HMS, were investigated and compared in the n-heptane isomerization reaction. The structural properties, surface area, acidity, catalytic activity, and selectivity of these catalysts were studied to determine the optimal performance for this reaction. The results showed that bi- and tri-metallic catalysts performed better than mono-metallic ones. The highest selectivity for multi-branched isomers (~۷۴%) was observed for Pt-Sn/HZSM۵-HMS at ۲۰۰ °C, while Pt/XH-HMS showed the highest surface area (۹۴۸ m۲/g) and reaction yield (~۵۱.۸%). XRD, UV-Vis DRS, NH۳-TPD, and SEM analyses confirmed that Sn and Re modifiers significantly improved the stability and reduced the undesired hydrogenolysis activity. In general, Pt-(Re, Sn)/HZSM-۵-HMS was superior to Pt/(۱۳X, HY, and HZSM-۵)-HMS due to higher selectivity for the desired products and greater resistance to coke deposition. Based on the obtained data, the Sn and Re-containing catalysts supported on HZSM-۵-HMS showed superior selectivity and stability. On the other hand, the Pt/XH-HMS composite showed the highest reaction surface and yield, therefore, the choice of catalyst depends on the industrial purpose: Pt-Sn/HZSM۵-HMS is recommended to maximize the selectivity of the branched isomer, while Pt/XH-HMS is optimal to achieve the highest conversion and reactivity.