Catalytic hydrotreatment of pyrolytic lignins to give alkylphenolics and aromatics using a supported Ru catalyst

Arjan Kloekhorst,Jelle Wildschut,Hero Jan Heeres

doi:10.1039/c4cy00242c

Abstract

The catalytic hydrotreatment of two pyrolytic lignins (pine and forestry residue), obtained from the corresponding fast pyrolysis oils, and organosolv Alcell lignin as a benchmark was explored in a batch set-up using Ru/C as the catalyst (400 °C, 4 h, 100 bar initial H2 pressure). The highest lignin oil yield was obtained for forest residue pyrolytic lignin (>75 wt% on intake). Advanced GCxGC techniques in combination with GPC and 13C-NMR measurements indicate that the lignin oils contain high amounts of interesting monomeric chemicals like alkylphenolics (up to 20.5 wt% on lignin feed intake) and aromatics (up to 14.1 wt% on lignin feed intake). These values are considerably higher than for Alcell lignin (6.6 wt% alkylphenolics and 9.7 wt% aromatics) and clearly indicate that pyrolytic lignins have potential to be used as feeds for the production of biobased phenolics and aromatics.

Highlights

The impending depletion of fossil resources together with environmental concerns has boosted research and development activities on renewable resources
The pyrolytic lignins used in this study are characterized by a relatively low molecular weight of around 700 g mol−1 (GPC), which is consistent with the molecular weight data reported by Bayerbach et al for PL from beech wood.[9,12]
The catalytic hydrotreatment of two representative pyrolytic lignins to low molecular weight aromatics and alkylphenolics was investigated and the results were compared with Alcell lignin

Summary

Introduction

The impending depletion of fossil resources together with environmental concerns has boosted research and development activities on renewable resources. An interesting alternative is biomass, which is currently already being used for the production of carbon-based transport fuels (e.g. bioethanol, biodiesel) and has high potential for bio-based chemicals.[1,2,3,4] An integrated model for biomass valorisation is the biorefinery concept, which is defined as the sustainable processing of biomass into a spectrum of marketable products and energy.[5] Various biorefinery models have been described and are actively being explored at the moment. An interesting example of the biorefinery concept is a pyrolysis oil biorefinery (see Fig. 1 for details). Pyrolysis oil is accessible from (lignocellulosic) biomass using fast pyrolysis technology in yields up to 70 wt%. It is considered an attractive liquefied form of biomass that has considerable advantages compared to solid biomass. Fast pyrolysis technology has shown to be economically viable in small scale units allowing decentralized biomass processing

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Discussion

Conclusion