Control of model catalytic conversion reaction over Pt nanoparticle supported mesoporous BEA zeolite catalysts

• Pt nanoparticles supported on mesoporous BEA zeolites yield cyclohexane and benzene.
• Product yields for cyclohexane and benzene are controlled by Pt loading and zeolite acidity.
• Weak acidity of mesoporous aluminosilica can inhibit the cracking reaction process.

Nanocrystalline mesoporous BEA zeolites supporting Pt metal nanoparticles have been investigated for the control of model catalytic reaction using methylcyclopentane as the reactant, while controlling the aluminum content in zeolite, Pt loading, Pt size and reaction temperature. Four different mesoporous BEA zeolites with different aluminum content were prepared via post-synthetic dealumination process with aqueous HCl solution. Pure mesoporous BEA zeolites without Pt metal nanoparticles converted methylcyclopentane to acyclic isomers via ring-opening and dehydrogenated version of methylcyclopentane as the major products, whereas Pt metal nanoparticle supported counterparts produced C6-cyclic products (cyclohexane, benzene) most dominantly. In the case of Pt loading, the cyclohexane/benzene formation ratio decreased as the loading of Pt metal nanoparticle increased. As the Pt size increased from 2.5 to 5, 7 nm, cyclohexane selectivity decreased whereas benzene selectivity increased. However, their tendencies were not significant, which means that the size of Pt nanoparticle is not crucial for control of product selectivity. As the reaction temperature increased from 150 to 200, 250 °C, cracking reaction pathway became much significant at the expense of that other reaction pathways were alleviated. This was due to the strong acidity of the mesoporous BEA zeolite support, which could be resolved by supporting Pt metal nanoparticles on weakly acidic mesoporous support such as aluminum-incorporated mesoporous silica.

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