Catalytic hydrotreatment of pyrolytic lignins from different sources to biobased chemicals: Identification of feed-product relations

M.B Figueirêdo,P.J Deuss,R.H Venderbosch,H.J Heeres

doi:10.1016/j.biombioe.2020.105484

M.B Figueirêdo, P.J Deuss + Show 2 more

Open Access

https://doi.org/10.1016/j.biombioe.2020.105484

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Abstract

The pyrolysis liquid biorefinery concept involves separation of pyrolysis liquids in various fractions followed by conversion of the fractions to value-added products. Pyrolytic lignins (PLs), the water-insoluble fractions of pyrolysis liquids, are heterogeneous, cross linked oligomers composed of substituted phenolics whose structure and physicochemical properties vary significantly depending on the biomass source. The catalytic hydrotreatment of six PLs from different biomass sources (pine, prunings, verge grass, miscanthus and sunflower seed peel) was investigated to determine the effect of different feedstocks on the final product composition and particularly the amount of alkylphenolics and aromatics, the latter being important building blocks for the chemical industry. Hydrotreatment was performed with Pd/C, 100 bar of hydrogen pressure and temperatures in the range of 350–435 °C, resulting in depolymerized product mixtures with monomer yields up to 39.1 wt% (based on PL intake). The molecular composition of the hydrotreated oils was shown to be a strong function of the PL feed and reaction conditions. Statistical analyses provided the identification of specific structural drivers on the formation of aromatics and phenolics, and a simple model able to accurately predict the yields of such monomers after catalytic hydrotreatment was obtained (R2 = 0.9944) and cross-validated (R2 = 0.9326). These feed-product relations will support future selections of PL feeds to obtain the highest amounts of valuable biobased chemicals.

Highlights

Pyrolysis liquids have great potential for the production of biofuels and biobased chemicals [1]
The Pyrolytic lignins (PLs) yield for the various biomass sources varied between 30 and 40 wt%, except for the product from prunings (PLC), which yielded 62% of PL. Possible explanations of this higher yield are: i) higher amounts of bark, extractives and impurities; ii) higher amounts of polysaccharides cova lently bound to the lignin [21]; iii) higher amounts of sugar and/or water molecules trapped during the separation steps, ending up in the insoluble fraction; iv) a combination thereof
The catalytic hydrotreatment of six well-characterized PLs from different biomass sources was investigated under a range of conditions

Summary

Introduction

Pyrolysis liquids have great potential for the production of biofuels and biobased chemicals [1]. Pyrolysis liquids can be either upgraded as a whole or sepa rated first into a sugar and lignin fraction through a simple water fractionation [3]. The latter results in the formation of a lignin-derived insoluble fraction, known as pyrolytic lignin (PL) and a pyrolytic sugar fraction. This initial fractionation is an essential element in a pyrolysis liquid biorefinery [4] (Fig. 1). Fractionation of the pyrolysis liquid into a PL and pyrolytic sugar fraction facilitates downstream upgrading, as each fraction can be processed through strategies tailored to their nature and inherent properties

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