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Synergistic Catalysis over Ru–Pd/Al₂O₃ Catalysts with Dual-Active Sites for Highly Selective Hydrogenation of Phthalic Anhydride to Hexahydrophthalide
Original title: Synergistic Catalysis over Ru–Pd/Al 2 O 3 Catalysts with Dual-Active Sites for Highly Selective Hydrogenation of Phthalic Anhydride to Hexahydrophthalide
Summary
Scientists developed a new metal catalyst that efficiently converts a chemical byproduct into a building block for a special plastic that can be chemically broken down and reused, rather than piling up in landfills or breaking into microplastics. This matters because microplastics have been found in human blood, organs, and even brain tissue, and creating plastics that can actually be recycled at the molecular level could help reduce that exposure over time. The catalyst worked with high efficiency (over 98% success rate) and remained stable for over three days of continuous use, suggesting it could be practical for real-world manufacturing.
Chemically recyclable polyester based on hexahydrophthalide is a kind of green solution to plastic pollution and resource waste. However, it is a challenge to produce hexahydrophthalide by selective hydrogenation of phthalic anhydride, in which multiple reducible functional groups need to be regulated to achieve dominant selectivity of hexahydrophthalide. In this work, ruthenium–palladium bimetallic catalysts with low Pd loading (about 0.06 wt %) were prepared by different methods and applied in the hydrogenation of phthalic anhydride to hexahydrophthalide. The synthesized Ru–Pd/Al 2 O 3 –IM catalyst via impregnation and Ru–Pd@Al 2 O 3 –SM catalyst via spray were characterized by XRD, TEM, EMPA, and XPS, which collectively confirmed the coexistence of Pd species and RuPd (Ru δ+ ) species in the Ru 10 –Pd 1 /Al 2 O 3 –IM catalyst. The synergistic effect of dual-active sites between Pd species and RuPd species brought about good catalytic performance, with 98.5% conversion of phthalic anhydride and 98.2% selectivity of hexahydrophthalide, as well as outstanding stability after 80 h at 3 MPa H 2 and 160 °C. The hydrogenation pathway of phthalic anhydride was proposed by a series of experiments of the hydrogenations of intermediates (phthalide, hexahydrophthalic anhydride, tetrahydrophthalic anhydride). This study highlights the importance of the preparation method for a bimetallic catalyst and the cooperative mechanism for hydrogenation of phthalic anhydride.