Limited availability and harmful environmental impacts of fossil sources have created a need for development of sustainable technologies using renewable feedstocks.  Manufacturing of nylon and esters require cyclohexanone and cyclohexanol as starting materials. These are also used as solvents in several processes. While conventional methods rely on fossil-derived crude oil to produce these chemicals, we are focusing on the selective production of cyclohexanone and cyclohexanol using bio-derived feedstock.  We have developed palladium (Pd) catalysts using a novel animated organic-inorganic hybrid support- ‘Swellable organically modified silica (SOMS)’ for aqueous phase hydrogenation of phenol to cyclohexanone and cyclohexanol. SOMS has a selective affinity towards organics and an ability to swell in the presence of organics imparting it a high adsorption capacity. This enhances the local concentration of the reactant near the active sites and hence, promote the reaction kinetics. SOMS is synthesized using sol gel method from organically modified precursor, bis (trimethoxysilyl) ethyl benzene, followed by capping of the hydrophilic Si-OH groups with hexamethyl disilazane. The synthesis procedure of SOMS was altered to modify the surface properties such as polarity, hydrophobicity and textural properties of SOMS. Activity experiments performed in a batch reactor at 50 bar H<sub>2</sub> at 200 °C, showed the dependence of cyclohexanol and cyclohexanone selectivity on the surface polarity of SOMS. Structural changes, resulting effects on phenol adsorption and metal dispersion, caused by the modification in the synthesis procedure were characterized by N<sub>2</sub> physisorption, infrared spectroscopy, pulse CO chemisorption and transmission Electron Microscopy (TEM), batch equilibrium adsorption. Thus, this work provides a unique and facile approach of synthesizing a catalyst with tunable surface polarity and hydrophobicity and hence tunable selectivity for cyclohexanone and cyclohexanol in phenol hydrogenation.

Tunable palladium catalyst using swellable organically modified silica as a scaffold for aqueous phase phenol hydrogenation

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