Transition metal sulfides are an extraordinarily vital class of semiconductors with a wide range of applications in the photocatalytic field. A great number of recent advances in photocatalytic ...transformations of lignocellulosic biomass, the largest renewable carbon resource, into high‐quality fuels and value‐added chemicals has been achieved over metal sulfide semiconductors. Herein, the progress and breakthroughs in metal‐sulfide‐based photocatalytic systems for lignocellulose valorization with an emphasis on selective depolymerization of lignin and oxidative coupling of some important bioplatforms are highligted. The key issues that control reaction pathways and mechanisms are carefully examined. The functions of metal sulfides in the elementary reactions, including CO‐bond cleavage, selective oxidations, CC coupling, and CH activation, are discussed to offer insights to guide the rational design of active and selective photocatalysts for sustainable chemistry. The prospects of sulfide photocatalysts in biomass valorization are also analyzed and briefly discussed.
Recent advances in metal‐sulfide‐based photocatalytic valorization of lignocellulose are reviewed. Structures, roles, and functioning mechanisms of metal sulfides in biomass conversions are carefully analyzed. The unique properties of metal sulfides in catalyzing CO‐bond cleavage, selective oxidation, CC coupling, and CH activation under light irradiation are highlighted and discussed to inspire future breakthroughs.
Microporous zeolites have proven to be of great importance in many chemical processes. Yet, they often suffer from diffusion limitations causing inefficient use of the available catalytically active ...sites. To address this problem, hierarchical zeolites have been developed, which extensively improve the catalytic performance. There is a multitude of recent literature describing synthesis of and catalysis with these hierarchical zeolites. This review attempts to organize and overview this literature (of the last 5 years), with emphasis on the most important advances with regard to synthesis and application of such zeolites. Special attention is paid to the most common and important 10‐ and 12‐membered ring zeolites (MTT, TON, FER, MFI, MOR, FAU, and *BEA). In contrast to previous reviews, the research per zeolite topology is brought together and discussed here. This allows the reader to instantly find the best synthesis method in accordance to the desired zeolite properties. A summarizing graph is made available to enable the reader to select suitable synthesis procedures based on zeolite acidity and mesoporosity, the two most important tunable properties.
A practical overview of the most recent literature on synthesis of hierarchical zeolites for most relevant zeolite topologies is presented. Several fine‐tuning efforts of established and novel synthesis methods are discussed. Remaining challenges and points of attention and a personal view for future synthesis research to obtain the most sustainable and catalytically active hierarchical zeolites are also presented.
The profitability and sustainability of future biorefineries are dependent on efficient feedstock use. Therefore, it is essential to valorize lignin when using wood. We have developed an integrated ...biorefinery that converts 78 weight % (wt %) of birch into xylochemicals. Reductive catalytic fractionation of the wood produces a carbohydrate pulp amenable to bioethanol production and a lignin oil. After extraction of the lignin oil, the crude, unseparated mixture of phenolic monomers is catalytically funneled into 20 wt % of phenol and 9 wt % of propylene (on the basis of lignin weight) by gas-phase hydroprocessing and dealkylation; the residual phenolic oligomers (30 wt %) are used in printing ink as replacements for controversial
-nonylphenol. A techno-economic analysis predicts an economically competitive production process, and a life-cycle assessment estimates a lower carbon dioxide footprint relative to that of fossil-based production.
Increasing demand for sustainable chemicals and fuels has pushed academia and industry to search for alternative feedstocks replacing crude oil in traditional refineries. As a result, an immense ...academic attention has focused on the valorisation of biomass (components) and derived intermediates to generate valuable platform chemicals and fuels. Zeolite catalysis plays a distinct role in many of these biomass conversion routes. This contribution emphasizes the progress and potential in zeolite catalysed biomass conversions and relates these to concepts established in existing petrochemical processes. The application of zeolites, equipped with a variety of active sites, in Brønsted acid, Lewis acid, or multifunctional catalysed reactions is discussed and generalised to provide a comprehensive overview. In addition, the feedstock shift from crude oil to biomass involves new challenges in developing fields, like mesoporosity and pore interconnectivity of zeolites and stability of zeolites in liquid phase. Finally, the future challenges and perspectives of zeolites in the processing of biomass conversion are discussed.
Biodegradable and renewable polymers, such as polylactic acid, are benign alternatives for petrochemical-based plastics. Current production of polylactic acid via its key building block lactide, the ...cyclic dimer of lactic acid, is inefficient in terms of energy, time, and feedstock use. We present a direct zeolite-based catalytic process, which converts lactic acid into lactide. The shape-selective properties of zeolites are essential to attain record lactide yields, outperforming those of the current multistep process by avoiding both racemization and side-product formation. The highly productive process is strengthened by facile recovery and practical reactivation of the catalyst, which remains structurally fit during at least six consecutive reactions, and by the ease of solvent and side-product recycling.
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