Simultaneous catalytic de-polymerization and hydrodeoxygenation of lignin in water/formic acid media with Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3 as bifunctional catalysts

Abstract

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

Unraveling the Role of Formic Acid and the Type of Solvent in the Catalytic Conversion of Lignin: A Holistic Approach

“…No effect of the H 2 partial pressure in the reaction was observed, which is probably because of the excess of H 2 present under the studied reaction conditions in which the rate‐limiting step is the previous deformylation. In the case of the uncatalyzed experiments, the three steps of the reaction would be catalyzed by the reactor surface, the activity of which has been proven previously, for which the activity would be lower than our NiMo/AA catalyst.…”

“…Formic acid can decompose either into H 2 and CO 2 or H 2 O and CO at high temperatures; although its decomposition kinetics can be modified by the presence of a catalyst . Previous results in our group suggest that in the LtL process formic acid is decomposed mainly into H 2 and CO 2 . For this reason, the oil and solid yields of the experiments performed with formic acid were compared with those of experiments in which formic acid was substituted either partially (ET‐FA/H 2 ‐BS) or totally by H 2 or a mixture of H 2 /CO 2 (1:1) (Table , entries 1, 2, and 4–7).…”

“…A detailed description is given elsewhere by Oregui‐Bengoechea et al . Briefly, after reaction completion the reactor was cooled overnight to RT, the produced gas was vented, and the gas quantity was determined.…”

Stirred and non-stirred lignin solvolysis with formic acid in aqueous and ethanolic solvent systems at different levels of loading in a 5-L reactor

“…Utilization of biomass as a renewable and sustainable raw material for production of biofuels and other value-added chemicals through a biorefinery approach has recently received a great deal of attention as a promising alternative to fossil resources (Cherubini and Jungmeier, 2010;Bu et al, 2012;Kim et al, 2013). A biorefinery system comprises optimal and sustainable use of the renewable resources where the incoming raw material is completely converted into a range of products with high values (Kleinert and Barth, 2008;Gasson et al, 2010;Oregui Bengoechea et al, 2015).…”

“…The reaction product is a mixture of monomeric alkylated phenols and aliphatic hydrocarbons, with a high H/C and a low O/C ratio. As shown by previous studies, the decomposition of formic acid and the chemical reaction between lignin and formic acid are competing reactions, and therefore, a formylation-eliminationhydrogenolysis mechanism for the formic acid aided lignin conversion has been proposed (Kleinert et al, 2009;Oregui Bengoechea et al, 2015;Løhre et al, 2017;Oregui Bengoechea et al, 2017). However, as highlighted in these works, optimization of such a process would be challenging and timeconsuming due to the interactions between different experimental conditions.…”