First insights of SHVO catalyst activity for monomeric phenol production from olive pomace

Abstract

BACKGROUND: Materials from renewable sources are in great demand to reduce carbon fingerprint. Olive pomace is a waste with high lignin content (>25%) and generated in high volumes. Therefore lignin from olive pomace is susceptible to be transformed into added value chemicals such as monomeric phenols through its catalytic depolymerization combining hydrogen donors (i.e. molecular hydrogen, polar protic solvents and formic acid) and catalysts based on transition metals (i.e. palladium and ruthenium supported on carbon, and SHVO catalyst, also ruthenium-based). RESULTS: The reaction conditions for the nitrogen and hydrogen experiments were temperatures of 250 and 200 ∘ C and initialpressures of 4 and 20 bar respectively. The bio-oil obtained after the catalytic process was approximately half of the initial sample weight, although somewhat lower under hydrogen conditions. The SHVO catalyst yielded 15 and 10% of monomeric phenols under nitrogen and hydrogen conditions respectively, while the other two catalysts yielded between 6 and 9% irrespective of the gas. CONCLUSION: Overall, the SHVO catalyst provided a richer mixture of phenolic compounds owing to its milder hydrogenation activity compared with the other catalysts, although at the end of the reaction the catalyst did not preserve its native form. The use of formic acid under nitrogen atmosphere was advantageous to increase the yields of phenols. The most abundant monomers in the experiments using SHVO catalyst under both atmospheres were 4-propylguaiacol, (Z)-propenylguaiacol, 4-propylsyringol, dihydroconiferyl alcohol, (Z)-propenylsyringol and dihydrosinapyl alcohol.