Developing Heterogeneous Catalysts for Biomass Conversion

Abstract

Hydrogenation, a prominent chemical process, finds extensive applications in both commercial and academic realms, particularly in the synthesis of valuable chemical intermediates, high-tonnage products, and important chemicals like agrochemicals and pharmaceuticals. The hydrogenation of phenol has been investigated using Pd (palladium) and Pd-Ru (palladium-ruthenium) supported on Al2O3 catalysts, which were operated in the liquid phase. The optimization of reaction conditions, including the choice of catalyst supports and metal loading, has been pursued to attain ideal outcomes. Notably, the Pd-Ru/Al2O3 catalyst, has demonstrated remarkableefficacy in phenol hydrogenation, outperforming other investigated supports and preparation methods employing modified impregnation with NaBH4 reduction. Additionally, Pd, Au (gold), and Pd-Au catalysts supported on Al2O3 catalysts have been utilized for the N-alkylation of phenol with p-toluidine, both with and without H2, at a temperature of 120 °C. A comprehensive investigation of various factors, including pressure, catalyst mass, support material, Au:Pd ratio, Pd loading, and solvent, has been undertaken to assess their influence on the reaction outcomes.Furthermore, Pd and Pd-Ru catalysts were studied for auto transfer reaction (HAT) involving benzyl alcohol and nitrobenzene. In this context, the synthesis of imine and secondary amine was thoroughly explored using Pd-Ru/Al2O3 catalysts at room temperature. The research revealed the exceptional effectiveness of Pd-Ru/Al2O3 catalysts for the synthesis of secondary amines under conditions of room temperature and low-pressure nitrogen (1 bar). Moreover, an investigation of various reaction parameters, such as temperature, catalyst treatment methods, and metal loading, has been conducted to gain a comprehensive understanding of the reaction system. The characteristics of catalysts are significantly influenced by the interaction between the metal and the support. Particularly, the electronic interaction between these components contributes to the enhancement of catalytic capabilities and stability. Building upon this crucial observation, researchers have opted to prepare Pd-Au and Pd-Ru catalysts utilizing Al2O3 as the support material. In-depth characterizations, including Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD), Brunauer Emmett-Teller (BET) surface area analysis, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM), have been employed to investigate the structural and electronic properties of the Pd Au and Pd-Ru catalysts supported on Al2O3. These investigations contribute valuable insights into the development and optimization of hydrogenation processes, paving the way for the efficient production of chemical intermediates, high-value products, and critical chemicals used in diverse industries. Moreover, the exploration of various catalyst compositions and support materials allows researchers to tailor catalytic systems for specific applications, leading to enhanced efficiency and stability in hydrogenation reactions.