Using decalin and tetralin as hydrogen source for transfer hydrogenation of renewable lignin-derived phenolics over activated carbon supported Pd and Pt catalysts

Catalytic hydrogenation is considered as an efficient technique for upgrading pyrolysis bio-oil. High flammability of hydrogen gas in contact with air leads to difficult control of high pressurized hydrogen gas in large-scale systems. Meanwhile, molecular hydrogen production is a costly industrial process. Thus, hydrogenation study using hydrogen donor (H-donor) material as alternative for hydrogen gas could be useful in terms of cost and safety control. In this study, the potential of decalin and tetralin for use as hydrogen source was investigated in transfer hydrogenation of renewable lignin-derived phenolic compounds (phenol, o-cresol and guaiacol) and a simulated phenolic bio-oil over Pd/C and Pt/C catalysts. Reaction mechanisms of H-donor dehydrogenation and phenolics hydrogenation were studied. Catalytic activity of Pt/C for transfer hydrogenation of the phenolic compounds was higher than that of Pd/C at reaction temperature of 275 °C. Decalin as hydrogen source showed to be more efficient for hydrogenation of the phenolic compounds compared to tetralin. In addition, the influence of water content on transfer hydrogenation activity was studied by employing the water to donor ratios of 0/100, 25/75, 50/50 and 75/25 g/g. Maximum hydrogenation of phenol as bio-oil model compound was observed at water to donor ratio of 50/50 g/g.