The development of catalysts possessing higher activity and selectivity is an ever-evolving area of interest. It is known that increasing dispersion and uniformity of metal deposition on the support enhances catalyst performance. The present study thus intended to establish an improved method for catalyst preparation. The modified electroless deposition (ED) method involved cyclic and sequential exposure of the alumina support to metal precursor and reducing agent solution. The use of surfactant during deposition facilitated the attainment of lower metal particle size on the support. The effects of ED method and surfactant-assisted electroless deposition (SED) method were studied by preparing alumina supported 2 wt% Pt catalysts. The physicochemical properties and catalytic performance for butane dehydrogenation reactions for these catalysts were compared with the catalyst prepared by conventional impregnation method (WI). The new ED preparation method successfully attained uniform coverage and enhanced dispersion of Pt particles over the support by aiding lowering of Pt metal size to 3.8 nm in comparison to 9.7 nm obtained by impregnation method. The addition of surfactant further reduced the Pt particle size to 1.7 nm. The presence of surfactant effectively prevented agglomeration of metal clusters in the solution resulting in deposition of lower size metal particles. The presence of a reducing agent ensured that the deposited metal particles were predominantly in reduced state. For reaction study, the catalyst prepared by ED method exhibited higher butane conversion (18.4%) in comparison to WI catalyst (16%). The conversion further increased to 24.5% for catalyst prepared by SED method. The highest conversion obtained for SED catalyst may be attributed to higher metal dispersion as it effectively increased the number of active metal particles at similar metal loading. Better metal dispersion also ensured effective coverage of the support acid sites, which promote C-C bond breakage leading to the formation of C1-C3 hydrocarbons and more coke deposition on catalysts. Accordingly, catalyst prepared by SED, having the highest metal dispersion, showed the highest selectivity for butene (&gt;90%) and lowest for C1-C3 hydrocarbons. The second highest butene selectivity was observed for ED catalyst (84%) and least for WI catalyst (61%) having the lowest metal dispersion. The on-stream stability was also improved for catalysts prepared by the new method.

Enhancement of catalytic performance of supported Pt catalysts using surfactant assisted electroless deposition method

ACS Fall 2020 Virtual Meeting

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