A Comparative study between Microwaves and Ultrasound Assisted in-Situ Reduction of Platinum supported γ-Al2O3 using different Organic templates for Enhanced Catalytic Activity and Potential Applications

In this study, mesoporous alumina was synthesized and modified with two different surfactants: cetyltrimethylammonium bromide (CTAB), a cationic surfactant, and pluronic P123, a non-ionic surfactant, using the sol-gel method. The synthesis involved the co-assembly of aluminum precursors with the surfactants, followed by calcination to remove the templates, resulting in a porous alumina structure that serves as a support. Platinum (Pt) was then loaded onto the surfactant-modified alumina support (CTAB) at a concentration of 0.9 wt. % using microwave-assisted solution (MAS) and ultrasonic techniques. The synthesized catalysts were characterized using nitrogen adsorption-desorption, X-ray diffraction (XRD), thermal analysis, and transmission electron microscopy (TEM) to assess their textural properties, thermal stability, and morphology. The catalytic activity of the Pt-loaded alumina catalysts was evaluated for n-hexane dehydrocyclization, cyclohexane dehydrogenation, and ethanol dehydration. Both the ultrasonic technique and microwave irradiation were employed as in situ reduction methods to produce stable, well-dispersed platinum nanoparticles with average diameters not exceeding 6 nm. The catalytic performance studies indicated that the 0.9 Pt/Al ₂ O ₃ (MAS) nanocatalyst, produced using the microwave approach, exhibited 86% higher catalytic activity for n-hexane dehydrocyclization and cyclohexane dehydrogenation into benzene at 450°C compared to the ultrasonic method, which achieved 75% activity. In ethanol conversion, the 0.9 Pt/Al ₂ O ₃ (US) sample generated via sonication was the most active for ethanol dehydration to ethylene, yielding 84% ethylene and 16% acetaldehyde, outperforming the 0.9 Pt/Al ₂ O ₃ (MAS) nanocatalyst.