The present study investigates the synthesis of novel strontium (Sr) and barium (Ba) modified crystalline zeolites including Zeolite Socony Mobil-5 (ZSM-5) and Mordenite (MOR) utilizing a batchwise ion-exchange method with an appropriate chloride solution of 3 N at pH 7.2 and 50 °C. Modified zeolites (Ba-ZSM-5 and Ba-MOR, Sr-ZSM-5 and Sr-MOR) were coated with an inert metal (Pt) by a novel supercritical CO 2 method using PtMe 2 COD as a precursor for n-hexane hydroisomerization in a microreactor unit at different temperatures (250−325 °C), H 2 /HC ratios of 3, 6, and 9, and a pressure of 5 bar. The acidic and physical features of Pt loaded zeolites were systematically characterized using FT-IR, XRD, BET surface area measurements, TGA, and TEM techniques. It is found that the metal loading in scCO 2 results in more uniform and very small metal nanoparticle (1.37 nm) dispersion with high stability after reduction. It is also revealed that high loading pressure in scCO 2 (280−300 bar) results in higher catalytic activity and surface area. The maximum conversion and selectivity of about 80 and 90% were achieved for n-hexane isomerization at 275 °C and a H 2 /HC ratio of 6 for Pt/Sr-ZSM-5 catalyst. Results reported that Pt loaded over all zeolites (H-MOR, Sr-MOR, Ba-MOR, H-ZSM-5, Ba-ZSM-5, and Sr-ZSM-5) by the scCO 2 method showed the minimum production of cracking products (C 1 −C 5 ) and maximum isomeric products including iso-C 6 isomers (2,2-DMB, 2,3-DMB, 2-MP, and 3-MP). Furthermore, the overall results of the rate of reaction revealed that Pt/Sr-ZSM-5 and Pt/Ba-ZSM-5 catalysts showed a better rate of isomerization (46.44%) and conversion (47%) for n-hexane at 300 °C and a H 2 /HC ratio of 9 with a minimum rate of cracking. However, it is concluded that the small, pored size Pt loaded ZSM-5 zeolite showed the highest catalytical activity compared to large pored MOR zeolite making it of great interest for diesel and gasoline formation in the oil refining industry.

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