Among all biomass sources, the lignocellulosic biomass derived from agricultural and forestry wastes is considered as the most adequate substitute for fossil sources due to its abundance, versatility and lack of competition with food resources. Yet, the efficient and economically feasible conversion of lignin into fuels and chemicals remains one of the major technology gaps for the development of lignocellulosic biorefineries. Here, the chemical nature of the lignin biopolymers will be described based on their botanical origin and the isolation process. After summarizing the most relevant advances in the catalytic conversion of lignin, the recently developed Ligninto-Liquids (LtL) process will be described and its major challenges addressed. 1.1 Energy transition: from crude oil to a biomass based energy system According to the results of the 2015 Revision 1 published by the Department of Economic and Social Affairs of United Nations (UN-DESA), the world population reached 7.3 billion as of mid-2015. The global population is expected to rise in the short-to-medium term, reaching between 8.4 and 8.6 billion in 2030 and between 9.5 and 13.3 billion by the end of the century 1. Hence, the demand of natural resources for the production of food, energy and chemicals is expected to increase significantly in the course of the century. It is important, therefore, to develop an integrated production model that addresses the sustainable and environmentally friendly production and distribution of these three basic commodities: food, energy and raw materials (chemicals). The challenge is of immense magnitude. In terms of food supply, the Food and Agriculture Organization (FAO) expects an steady growth of the total agricultural product consumption of 1.1 % per year until 2050 2. The global energy demand is estimated to grow even faster, by 48 % between 2012 and 2040 (Figure 1.1, above); fossil fuels being the major contributor providing over 78 % of the demand 3. The same trend is observed for the bulk chemicals, of which organic chemicals account for 4 CHAPTER 1

Lignin is naturally abundant and a renewable precursor with the potential to be used in the production of both chemicals and materials. As many lignin conversion processes suffer from a significant production of solid wastes in the form of hydrochars, this study focused on transforming hydrochars into magnetic activated carbons (MAC). The hydrochars were produced via hydrothermal treatment of lignins together with formic acid. The activation of the hydrochars was performed chemically with KOH with a focus on the optimization of the MACs as adsorbents for CO2. MACs are potentially relevant to carbon capture and storage (CCS) and gas purification processes. In general, the MACs had high specific surface areas (up to 2875 m2/g), high specific pore volumes, and CO2 adsorption capacities of up to 6.0 mmol/g (1 atm, 0 °C). The textual properties of the MACs depended on the temperature of the activation. MACs activated at a temperature of 700 °C had very high ultramicropore volumes, which are relevant for potential adsorption-driven separation of CO2 from N2. Activation at 800 °C led to MACs with larger pores and very high specific surface areas. This temperature-dependent optimization option, combined with the magnetic properties, provided numerous potential applications of the MACs besides those of CCS. The hydrochar was derived from eucalyptus lignin, and the corresponding MACs displayed soft magnetic behavior with coercivities of <100 Oe and saturation magnetization values of 1–10 emu/g.

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The chemo-selective hydrogenolysis of secondary hydroxyls is an important reaction for the production of biomass-derived α,ω-diols. This is the case for 1,3-propanediol production from glycerol. Supported Pt-WOx materials are effective catalysts for this transformation, and their activity is often related to the tungsten surface density and Brönsted acidity, although there are discrepancies in this regard. In this work, a series of Pt-WOx/γ-Al2O3 catalysts were prepared by modifying the pH of the solutions used in the active metal impregnation step. The activity–structure relationships, together with the results from the addition of in situ titrants, i.e., 2,6-di-tert-butyl-pyridine or pyridine, helped in elucidating the nature of the bifunctional active sites for the selective production of 1,3-propanediol.

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