Climbing the Bio-based Value Pyramid by Novel Transformations

In the last two centuries, the exponential industrial development was propelled by the exploitation of finite and depleting fossil resources, contributing – via the increased level of CO2 in the atmosphere – to climate change. Biomass could serve as an ideal carbon-neutral resource for the production of essential chemicals, until – or in parallel with – the realization of the direct, energy-efficient transformation of atmospheric CO2. This important research area has received a lot of attention in the past decade; however, the transition towards using renewable resources should be critically analyzed to deliver real net CO2 reduction and avoid unfair competition for food/feed. In this thesis, selected examples of neglected waste stream, volumes, potential applications are contrasted with the current demand for certain commodity chemicals. First, the synthesis of jet fuels and polymer building blocks from renewables via catalytic methodologies were demonstrated. Secondly, surfactants were identified as an ideal target for the incorporation of the neglected waste streams, e.g. lignocellulose and used cooking oil. Three high-performance surfactant families were designed, synthesized and characterized, capitalizing on the novel structures that are benign by design and obtained via catalytic methodologies under mild conditions.The present work attempts laying the foundation of profitable upcycling of neglected waste streams and ultimately the development of fully sustainable and economically viable synthesis of high-performance surfactants. They could bring benefits across many local economies: from less developed rural regions to the ultimate testing ground of conscious material management: Space colonies

Development of ’Lignin-First’ Approaches for the Valorization of Lignocellulosic Biomass

Currently, valorization of lignocellulosic biomass almost exclusively focuses on the production of pulp, paper, and bioethanol from its holocellulose constituent, while the remaining lignin part that comprises the highest carbon content, is burned and treated as waste. Lignin has a complex structure built up from propylphenolic subunits; therefore, its valorization to value-added products (aromatics, phenolics, biogasoline, etc.) is highly desirable. However, during the pulping processes, the original structure of native lignin changes to technical lignin. Due to this extensive structural modification, involving the cleavage of the β-O-4 moieties and the formation of recalcitrant C-C bonds, its catalytic depolymerization requires harsh reaction conditions. In order to apply mild conditions and to gain fewer and uniform products, a new strategy has emerged in the past few years, named ‘lignin-first’ or ‘reductive catalytic fractionation’ (RCF). This signifies lignin disassembly prior to carbohydrate valorization. The aim of the present work is to follow historically, year-by-year, the development of ‘lignin-first’ approach. A compact summary of reached achievements, future perspectives and remaining challenges is also given at the end of the review

Direct asymmetric reduction of levulinic acid to gamma-valerolactone: synthesis of a chiral platform molecule

Levulinic acid was directly converted to optically active (S)-gamma-valerolactone, a proposed biomass-based chiral platform molecule. By using a SEGPHOS ligand-modified ruthenium catalyst in methanol as a co-solvent, eventually, 100% chemoselectivity, and 82% enantioselectivity were achieved. The effect of the catalyst composition and reaction parameters on the activity and selectivity was investigated in detail. The conversion of a “real” biomass derived levulinic acid to optically active GVL without decreasing the enantioselectivity was also demonstrated

A molecular motor from lignocellulose

Lignin is the largest natural source of functionalized aromatics on the planet, therefore exploiting its inherent structural features for the synthesis of aromatic products is a timely and ambitious goal. While the recently developed lignin depolymerization strategies gave rise to well-defined aromatic platform chemicals, the diversification of these structures, especially toward high-end applications is still poorly addressed. Molecular motors and switches have found widespread application in many important areas such as targeted drug delivery systems, responsive coatings for self-healing surfaces, paints and resins or muscles for soft robotics. They typically comprise a functionalized aromatic backbone, yet their synthesis from lignin has not been considered before. In this contribution, we showcase the synthesis of a novel light-driven unidirectional molecular motor from the specific aromatic platform chemical 4-(3-hydroxypropyl)-2,6-dimethoxyphenol (dihydrosynapyl alcohol) that can be directly obtained from lignocellulose via a reductive catalytic fractionation strategy. The synthetic path takes into account the principles of green chemistry and aims to maintain the intrinsic functionality of the lignin-derived platform molecule

Bright Side of Lignin Depolymerization:Toward New Platform Chemicals

Lignin, a major component of lignocellulose, is the largest source of aromatic building blocks on the planet and harbors great potential to serve as starting material for the production of biobased products. Despite the initial challenges associated with the robust and irregular structure of lignin, the valorization of this intriguing aromatic biopolymer has come a long way: recently, many creative strategies emerged that deliver defined products via catalytic or biocatalytic depolymerization in good yields. The purpose of this review is to provide insight into these novel approaches and the potential application of such emerging new structures for the synthesis of biobased polymers or pharmacologically active molecules. Existing strategies for functionalization or defunctionalization of lignin-based compounds are also summarized. Following the whole value chain from raw lignocellulose through depolymerization to application whenever possible, specific lignin-based compounds emerge that could be in the future considered as potential lignin-derived platform chemicals

Complete lignocellulose conversion with integrated catalyst recycling yielding valuable aromatics and fuels

Lignocellulose, the main component of agricultural and forestry waste, harbours tremendous potential as a renewable starting material for future biorefinery practices. However, this potential remains largely unexploited due to the lack of strategies that derive substantial value from its main constituents. Here, we present a catalytic strategy that is able to transform lignocellulose to a range of attractive products. At the centre of our approach is the flexible use of a non-precious metal catalyst in two distinct stages of a lignocellulose conversion process that enables integrated catalyst recycling through full conversion of all process residues. From the lignin, pharmaceutical and polymer building blocks are obtained. Notably, among these pathways are systematic chemo-catalytic methodologies to yield amines from lignin. The (hemi)cellulose-derived aliphatic alcohols are transformed to alkanes, achieving excellent total carbon utilization. This work will inspire the development of fully sustainable and economically viable biorefineries