Acid Hydrolysis of Lignocellulosic Biomass: Sugars and Furfurals Formation

Katarzyna Świątek,Jörg Sauer,Andreas Klier,David Steinbach,Stephanie Gaag,Andrea Kruse

doi:10.3390/catal10040437

Katarzyna Świątek, Jörg Sauer + Show 4 more

Open Access

https://doi.org/10.3390/catal10040437

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Abstract

Hydrolysis of lignocellulosic biomass is a crucial step for the production of sugars and biobased platform chemicals. Pretreatment experiments in a semi-continuous plant with diluted sulphuric acid as catalyst were carried out to measure the time-dependent formation of sugars (glucose, xylose, mannose), furfurals, and organic acids (acetic, formic, and levulinic acid) at different hydrolysis temperatures (180, 200, 220 °C) of one representative of each basic type of lignocellulose: hardwood, softwood, and grass. The addition of the acid catalyst is followed by a sharp increase in the sugar concentration. Xylose and mannose were mainly formed in the initial stages of the process, while glucose was released slowly. Increasing the reaction temperature had a positive effect on the formation of furfurals and organic acids, especially on hydroxymehtylfurfural (HMF) and levulinic acid, regardless of biomass type. In addition, large amounts of formic acid were released during the hydrolysis of miscanthus grass. Structural changes in the solid residue show a complete hydrolysis of hemicellulose at 180 °C and of cellulose at 200 °C after around 120 min reaction time. The results obtained in this study can be used for the optimisation of the hydrolysis conditions and reactor design to maximise the yields of desired products, which might be sugars or furfurals.

Highlights

Renewable lignocellulosic feedstocks have potential for large-scale production of biofuels and chemicals in second generation biorefineries with sugars from cellulose and hemicellulose as intermediates [1]
Hydrolysis of lignocellulosic materials is a crucial step for sugars as well as biobased platform chemicals production (HMF, furfural, levulinic acid)
This study focused on dilute acid hydrolysis at different temperatures of three lignocellulosic feedstocks

Summary

Introduction

Renewable lignocellulosic feedstocks have potential for large-scale production of biofuels and chemicals in second generation biorefineries with sugars from cellulose and hemicellulose as intermediates [1]. Mild reaction conditions are employed to minimise the formation of fermentation inhibitors. This sugar can be used for platform chemical production, for example, hydroxymethylfurfural (HMF) [4], by chemical pathways. Modification of the existing hydrolysis process would directly provide platform chemicals like HMF, furfural, and levulinic acid as primary products [5]. In this case, more severe reaction conditions can be applied, because the fact that these compounds may inhibit yeasts is of no importance

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