Lignin to liquids over sulfided catalysts

Direct lignin conversion into valuable chemicals (phenols and hydrocarbons) was explored in a semi-continuous tubular reactor in the presence of a heterogeneous hydrotreating catalyst at 320–380 °C and hydrogen pressure 4–7 MPa. The catalyst to lignin mass ratio was varied in the range 0.25–1. The hydrolysis lignin was fully converted under the experimental conditions to yield gaseous, liquid and solid products. The amount of the undesired solid products decreased with the increasing severity of reaction conditions. The liquid products consisted mainly of aromatics and naphthenes in the organic phase and phenols in the aqueous phase. The proximity of the catalyst active sites and of the primary reaction intermediates originating from thermal depolymerization of lignin was shown to be crucial for product distribution.

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► Direct conversion of lignin to chemicals is possible.
► Close proximity between catalyst active sites and reaction intermediates is essential.
► Complete conversion of lignin achieved in presence of a hydrotreating catalyst.