The role of gas pressure, acid, metal and their synergistic effects on the catalytic cleavage of the ether bonds in benzyl phenyl ether (BPE) in aqueous and apolar phase using Ni and zeolite based catalysts are investigated. In absence of catalysts, the C-O bond is catalytically cleaved in water via hydrolysis forming phenol and benzyl alcohol as intermediates, followed by C-C bond alkylation. At the high temperature (523 K) water is dissociated to hydronium ions, which catalyzing both the hydrolysis and alkylation. Upon addition of a solid acid (HZSM-5), rates of hydrolysis and alkylation are markedly increased in proportion to the acid concentrations. In presence of a metal (Ni/SiO2), the selective hydrogenolysis becomes the major reaction route for cleaving the Caliphatic-O bond, forming phenol and toluene. Catalyzed by the dual-functional Ni/HZSM-5, hydrogenolysis occurs as the major route rather than hydrolysis (minor). In the apolar undecane, the non-catalytic thermal pyrolysis route dominates. Hydrogenolysis of BPE appears to be the major reaction pathway in undecane in presence of Ni/SiO2 or Ni/HZSM-5, almost suppressing the radical reactions completely. The density functional theory (DFT) calculations strongly support the proposed C-O bond cleavage mechanisms on BPE in aqueous and apolar phases. DFT calculations show that BPE is initially protonated and subsequently hydrolyzed in aqueous phase. The radical reaction plays a significant role for generating primary benzyl and phenoxy radicals in undecane evidenced by DFT calculation, which leads to heavier condensation products without the aid of metals for providing dissociated hydrogen radicals.

Mechanisms of catalytic conversion of lignin-derived benzyl phenyl ether in aqueous and apolar phase

247th National Meeting (2014)

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