Production of high carbon number hydrocarbon fuels from a lignin-derived α-O-4 phenolic dimer, benzyl phenyl ether, via isomerization of ether to alcohols on high-surface-area silica-alumina aerogel catalysts

Two-step hydrodeoxygenation of benzyl phenyl ether (BPE), a lignin-derived phenolic dimer containing an alpha-O-4 linkage, was performed to produce high carbon number saturated hydrocarbons. The ether linkage of BPE was first isomerized to alcohols of benzylphenols on the solid acid catalysts of silica (SA), alumina (AA), and silica-alumina aerogels (SAAs), which were further hydrodeoxygenated to saturated cyclic hydrocarbons on a silica-alumina-supported Ru catalyst. During the isomerization of BPE, noble-metal-free catalysts suppressed the formation of phenyl monomers but produced the phenolic dimers. SA, AA, and SAA-73 (Al/(Si + Al)=0.73) exhibited negligible activity. However, SAA-38 and SAA-57 containing Al/(Si + Al) contents of 0.38 and 0.57, respectively, exhibited high catalytic activity among the prepared aerogel catalysts. The BPE conversion on SAA-38 reached 100% at a temperature range of 100-150 degrees C. The Bronsted acid sites appear to be catalytic active sites. On the basis of the predominant isomerization of phenyl ether to phenols over ether decomposition on the SAAs, the following second step of hydrodeoxygenation (H DO) after the first step of isomerization of BPE produced deoxygenated C13-19 cyclic hydrocarbons, as opposed to the saturated deoxygenated cyclic hydrocarbons produced trhough a one-step reaction process with silica-alumina-supported Ru catalysts, demonstrating this to be a promising process for producing high carbon number hydrocarbons from lignin dimers and oligomers. (c) 2013 Published by Elsevier B.V.