SPICY Publications


Functionalised Heterogeneous Catalysts for Sustainable Biomass Valorization
Putla Sudarsanam, Ruyi Zhong, Sander Van den Bosch, Simona M. Coman, Vasile I. Parvulescu, Bert F. Sels
Chem. Soc. Rev., 2018,47, 8349-8402 – DOI: 10.1039/C8CS00410B

Efficient transformation of biomass to value-added chemicals and high-energy density fuels is pivotal for a more sustainable economy and carbon-neutral society. In this framework, developing potential cascade chemical processes using functionalised heterogeneous catalysts is essential because of their versatile roles towards viable biomass valorisation. Advances in materials science and catalysis have provided several innovative strategies for the design of new appealing catalytic materials with well-defined structures and special characteristics. Promising catalytic materials that have paved the way for exciting scientific breakthroughs in biomass upgrading are carbon materials, metal–organic frameworks, solid phase ionic liquids, and magnetic iron oxides. These fascinating catalysts offer unique possibilities to accommodate adequate amounts of acid–base and redox functional species, hence enabling various biomass conversion reactions in a one-pot way. This review therefore aims to provide a comprehensive account of the most significant advances in the development of functionalised heterogeneous catalysts for efficient biomass upgrading. In addition, this review highlights important progress ensued in tailoring the immobilisation of desirable functional groups on particular sites of the above-listed materials, while critically discussing the role of consequent properties on cascade reactions as well as on other vital processes within the bio-refinery. Current challenges and future opportunities towards a rational design of novel functionalised heterogeneous catalysts for sustainable biomass valorisation are also emphasized.


Advances in Porous and Nanoscale Catalysts for Viable Biomass Conversion
Putla Sudarsanam, Elise Peeters, Ekaterina V. Makshina, Vasile I. Parvulescu, Bert F. Sels
Chem. Soc. Rev., 2019, Advance Article – DOI: 10.1039/C8CS00452H

Heterogeneous catalysis is a promising technology for the valorization of renewable biomass to sustainable advanced fuels and fine chemicals. Porosity and nanostructure are the most versatile features of heterogeneous solid catalysts, which can greatly determine the accessibility of specific active sites, reaction mechanisms, and the selectivity of desirable products. Hence, the precise tuning of porosity and nanostructure has been a potential strategy towards developing novel solid catalysts with indispensable characteristics for efficient biomass valorization. Herein, we present a timely and comprehensive review of the recent advances in catalytic biomass conversions over microporous zeolites, mesoporous silicas, and nanostructured metals/metal oxides. This review covers the catalytic processing of both edible (lipids and starch) and non-edible (lignocellulose) biomass as well as their derived compounds, along with a systematic evaluation of catalyst reusability/kinetic/mechanistic aspects in the relevant processes. The key parameters essential for tailoring particle size, morphology, porosity, acid–base, and redox properties of solid catalysts are emphasized, while discussing the ensuing catalytic effects towards the selective conversion of biomass into desirable chemicals. Special attention has been drawn to understand the role of water in liquid phase biomass conversions as well as the hydrothermal stability and the deactivation of nanoporous catalysts. We believe this comprehensive review will provide new insights towards developing state-of-the-art solid catalysts with well-defined porosity and nanoscale properties for viable biomass conversion.

Bio-Acrylates Production: Recent Catalytic Advances and Perspectives of the Use of Lactic Acid and their Derivatives
Ekaterina V. Makshina, Judit Canadell, Jan van Krieken, Elise Peeters, Michiel Dusselier, Bert F. Sels
ChemCatChem, 2019, 180-201 – DOI: 10.1002/cctc.201801494

The production of drop‐in chemicals from bio‐based renewable sources is gaining a lot of momentum due to proven negative impact of fossil‐based economy on environment and society. In this Review, various bio‐derived platform molecules are assessed as renewable alternatives to fossil resources for the catalytic production of acrylates. Acrylic acid and its esters are key building blocks of a large number of high‐value oligomers and polymers in the current industry. In spite of the encouraging successes reported on gram or lab‐scale, real implementation of bio‐based examples remain scarce mainly due to the current high cost and limited availability of the bio‐based substrates. As lactic acid and their derivatives are one of the most promising feedstocks for bio‐acrylate production, they are the main focus of this Review.


Muconic Acid Isomers as Platform Chemicals and Monomers in the Biobased Economy
Ibrahim Khalil, Greg Quintens, Tanja Junkers, Michiel Dusselier
Green Chem., 2020, 22, 1517-1541 – DOI: 10.1039/C9GC04161C

Muconic acid (MA) is a high value-added dicarboxylic acid with conjugated double bonds, presenting three isomeric forms, i.e., cis,cis-MA, cis,trans-MA and trans,trans-MA. Its production is garnering increased interest owing to its potential as a starting material for the synthesis of value-added products as well as by being a versatile monomer for the production of specialty polymers. This review presents a systematic overview of production and synthesis routes to MA isomers as well as the routes for its final valorization. The production of MA through chemical pathways and the progress developed in the biotechnological pathways will be discussed. Traditional and new processes for achieving successful isomerization into the value-added trans,trans form of MA are also discussed and compared, with their constraints and possible solutions. The valorization of the three different isomers of MA into value-added chemicals such as adipic or terephthalic acids and MA polymers are summarized. Finally, the review concludes with a thorough summary, a practical insights section and an outlook. This work thus offers new perspectives and guidelines to tackle the challenges in MA chemistry, especially when aiming to combine an efficient biotechnological production of MA with its valorization.

Muconic Acid Esters as Bio-Based Acrylate Mimics
Greg Quintens, Jeroen H. Vrijsen, Peter Adriaensens, Dirk Vanderzande, Tanja Junkers
Polym. Chem., 2019, 10, 5555-5563 – DOI: 10.1039/C9PY01313J

Over the course of the last century, a large number of synthetic polymers has been developed and introduced. Yet, most polymer materials are based on fossil fuels as raw materials and are associated with a considerable environmental impact. trans,trans-Muconic acid esters are interesting plant-based monomers that have not received much attention yet. The synthesis of a series of dialkyl muconates from muconic acid is described, followed by an optimization of the solution free-radical polymerization of these monomers. Unlike the claim in previous studies, dialkyl muconates can be polymerized efficiently in solution to polymers with significant molecular weights above 105 g mol−1. Polymerizations are, however, relatively slow, as can be expected for diene monomers (48 h at 120 °C). Mark–Houwink coefficients have been determined for diethyl muconate, dibutyl muconate and di(2-ethylhexyl) muconate. Furthermore, glass transition temperatures and thermal stability are assessed for the polymers, showcasing that polymuconates can serve as alternatives to polyacrylate materials. In a last step, also the reversible addition–fragmentation chain transfer (RAFT) polymerization of the muconates is investigated, showing excellent control over the molecular weight when a conventional trithiocarbonate is used to control polymerizations.