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

Abstract

Abstract 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% Pt 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 results indicated that the 0.9 wt% Pt/Al₂O₃ (MAS) nanocatalyst outperformed its US-prepared counterpart. It achieved the highest conversion rate of 86% in cyclohexane dehydrogenation at 450 °C. In n-hexane dehydrocyclization, the MAS catalyst produced a maximum benzene yield of 48%. Additionally, in ethanol dehydration, it demonstrated superior activity with a maximum ethylene yield of 52% under the tested conditions.