Ewoud

A two-step protocol is developed for the efficient oxidative degradation of Kraft lignin. This method utilizes a highly concentrated peroxodicarbonate solution at moderate temperatures, followed by thermal treatment, significantly enhancing monoaromatic yield up to 15.6 wt%. Cogenerated carbonates in this transformation represent the make-up chemical of pulping plants.

The oxidative degradation of technically relevant types of Kraft lignin is efficiently accomplished by a significantly improved two-step protocol. The key is the use of highly concentrated peroxodicarbonate solution which selectively oxidizes the lignin particles at moderate temperature which are thermally treated in a subsequent step. The liberation of low-molecular-weight phenols occurs when the oxidizer is already consumed enhancing the yield of target compounds strongly up to 15.6 wt%. Co-generated carbonates in this transformation represent the make-up chemical of pulping plants. This makes this approach suitable and attractive to be implemented as a bolt-on or integrated into the Kraft pulping process. The green metrics clearly indicate the sustainable and superior features of the method established.

This interdisciplinary article explores the potential of biodegradable and biobased polymers (BBPs) to address plastic pollution and microplastic generation. It examines feedstock selection, chemical modification, use, and end-of-life scenarios, including biodegradation and environmental impact of BBPs. Societal perceptions and regulatory frameworks are also discussed.

Abstract

Global demand to reduce polymer waste and microplastics pollution has increased in recent years, prompting further research, development, and wider use of biodegradable and biobased polymers (BBPs). BBPs have emerged as promising alternatives to conventional plastics, with the potential to mitigate the environmental burdens of persistent plastic waste. We provide an updated perspective on their impact, five years after our last article, featuring several recent advances, particularly in exploring broader variety of feedstock, applying novel chemical modifications, and developing new functionalities. Life-cycle assessments reveal that environmental performance of BBPs depends on several factors including feedstock selection, production efficiency, and end-of-life management. Furthermore, the introduction of BBPs in several everyday life products has also influenced consumer perception, market dynamics, and regulatory frameworks. Although offering environmental advantages in specific applications, BBPs also raise concerns regarding their biodegradability under varying environmental conditions, potential microplastic generation, and soil health impacts. We highlight the need for a circular approach considering the entire polymer life cycle, from feedstock sourcing, modification and use, to end-of-life options. Interdisciplinary research, collaborative initiatives, and informed policymaking are crucial to unlocking the full potential of BBPs and exploiting their contribution to create a circular economy and more sustainable future.

A single-site Pt-doped RuO₂ was developed as a bifunctional electrocatalyst for synthesis of GA and H₂ fuels from PET wastes. Specifically, Pt₁/RuO₂ realizes a stable electrolysis over 500 h at 6 A with a GA and H₂ yield rate of 4.06 g h⁻¹ and 2.38 L h⁻¹, respectively, using a membrane electrode assembly.

Abstract

Electrochemical upcycling of polyethylene terephthalate (PET) wastes into valuable glycolic acid (GA) is an ideal solution for resource utilization. However, simultaneously achieving high activity and selectivity remains challenging due to the over-oxidation and C−C cleavage during ethylene glycol (EG) oxidation in PET hydrolysate. Herein, we develop an atomically isolated Pt on RuO₂ (Pt₁/RuO₂) catalyst composed of high-density Pt−Ru interfaces that ensure single-site adsorption of EG, enrich surface *OH coverage and weaken *CO−CH₂OH intermediate adsorption, thereby synergistically promoting GA generation. Specifically, Pt₁/RuO₂ delivers a remarkable mass activity of 8.09 A/mg_Pt, as well as a high GA Faradaic efficiency (95.3 %) and selectivity (96.9 %). Under membrane electrode assembly conditions, Pt₁/RuO₂ realizes a stable electrolysis over 500 h at 6 A with a GA yield rate of 4.06 g h⁻¹. In-depth theoretical and in situ spectroscopic investigations reveal the synergy between isolated Pt and oxophilic RuO₂ plays a crucial role in high-efficiency EG-to-GA conversion. This study offers valuable insights for the rational design of advanced catalysts for GA synthesis from PET wastes via a single-site doped bimetallic strategy.

Controlled Peracetic acid mediated oxidative depolymerization of lignins via deep eutectic solvents extraction using choline chloride/lactic acid and lactic acid/pyrazole solvents, correlating lignin structure with product selectivity for sustainable biorefineries.

Developing a selective lignin depolymerization process remains a daunting challenge due to lignin's inherent structural heterogeneity and chemical complexity. This study used a novel deep eutectic solvent (DES) extraction to produce oligomeric lignin with controlled structural characteristics (narrow size distribution, lower molecular weight) and further subjected it to oxidative depolymerization using peracetic acid as an oxidant. Oxidation of lignin resulting from lactic acid/pyrazole and choline chloride/lactic acid extraction produces phenolic acids (Ph-COOH) and dicarboxylic acid (DCA) as significant products. Our results show that the judicial choice of DES during extraction plays a critical role in determining the lignin chemical structure, which follows different oxidation pathways and results in different product selectivities. The generalization of this concept has been established with two different parent lignins, e.g., Douglas fir (D.fir) and wheat straw (WS). The overall process showed that the novel DES extraction not only provides a sustainable pathway for high-purity lignin generation but also could be used as a tool to produce high-value products selectively upon its oxidation, thus improving the overall lignin biorefinery process.

The synergistic interaction between Ru nanoparticles and functionalized carbon support is demonstrated as key factor for superior catalytic activity of Ru@FC catalyst. In addition, the reaction mechanism was proposed in which LA transformed to pseudo-LA over Ru@FC catalyst followed by dehydration and hydrogenation steps to produce GVL. Response surface methodology (RSM) was employed to optimize the reaction conditions.

Abstract

Ru nanoparticles (NPs) embedded in functionalized carbon (Ru@FC) were synthesized and employed as a bifuntional catalyst for the catalytic transfer hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). The synergistic interaction between the functionalized carbon support and Ru NPs was demonstrated with the carbon support facilitating the dehydration step, while Ru NPs acted as active sites for hydrogenation. The proposed reaction pathway involves the initial transformation of LA into a pseudo-LA intermediate over Ru@FC catalyst followed by dehydration and hydrogenation steps to produce GVL. Additionally, the response surface methodology (RSM) was used for the first time to predict the optimal reaction conditions and evaluate the influence of reaction parameters on the formation of the desired product. The quadratic model was effectively fitted between experimental and predicted data with a low p-value (<0.0001) and high R² (0.9967). Among the catalysts tested, 5Ru@FC-30% exhibited superior catalytic performance achieving a high GVL yield of 98.6% under optimized conditions (10 mg catalyst, 130°C, 5 h). Moreover, the 5Ru@FC-30% catalyst demonstrated high stability and reusability over five cycles. This work contributes a novel Ru@FC catalyst for sustainable and efficient biomass valorization.

Nature, Published online: 07 May 2025; doi:10.1038/d41586-025-01417-0

Nature, Published online: 07 May 2025; doi:10.1038/d41586-025-01061-8

Nature, Published online: 05 May 2025; doi:10.1038/d41586-025-01353-z

Nature, Published online: 25 April 2025; doi:10.1038/d41586-025-01272-z

The residual chloride ions in the commercially available Ru/C catalyst can influence the output of reductive catalytic fractionation of biomass, leading to the unselective degradation of hemicellulose.

Catalytic fractionation of lignocellulosic biomass is a promising technology for obtaining different fractions and the valorization of lignin. Reductive catalytic fractionation (RCF) is one of these technologies in which catalysts play an essential role. In this work, the impact of impurities in catalysts on the output of RCF is investigated. It is found that the yield of phenolic monomers is almost not influenced by the residual chloride (Cl) ions in the commercially available Ru/C catalyst. However, the presence of Cl ions in the catalyst facilitated hemicellulose removal and delignification. Moreover, the enzymatic conversion rate of cellulose in the solid residue increases after RCF, attributed to the enhanced removal of lignin and hemicellulose in the presence of Cl ions. The impact of Cl ions can be eliminated by removing the Cl ions in the catalyst. This work provides an engineering perspective for upscaling RCF technology using large-scale synthesized catalysts.

Removal of the C_γ─OH in methanol solvolyzed lignin followed by simultaneous cleavage of C_α─OH and β─O─4 bond enables valorization of native lignin in biomass toward prop-1-enyl (79.6% selectivity) and propyl (81.7% selectivity) substituted monomers under N₂ and H₂ atmosphere, respectively.

Abstract

Reductive catalytic fractionation (RCF) is a promising technology that can selectively extract lignin in biomass and depolymerize it. Here, we prepared one low Ru loading catalyst (Ru_0.8/C) for RCF of biomass to selectively produce different lignin oils (both monomers and oligomers) under different reaction atmospheres. The yield of phenolic monomers reached 46.0wt.% (rich in 4-propylguaiacol and 4-propylsyringol) in the RCF of birch wood under high H₂ pressure and using methanol as the solvent. But, under N₂ atmosphere the dominant monomers shifted to 4-(prop-1-enyl)guaiacol and 4-(prop-1-enyl)syringol (79.6% selectivity) with 35.8wt.% yield of total monomers using the same catalyst. The developed catalyst can also transform native lignin in other biomasses such as pine and corn stover. Mechanistic investigation using different model compounds and deuteration indicates that removal of the C_γ─OH in methanol-extracted lignin fragments occurred before obtaining the monomeric lignin fragment, and the C_α─OH and β─O─4 bonds were then cleaved simultaneously to form 4-(prop-1-enyl) substituted monomers. The results are distinct from the reported mechanism that the precursors of the propyl and prop-1-enyl substituted monomers are monolignols with removal of the C_γ─OH at the monomeric level. Thus, this work provided novel insights into the reaction pathway of (native) lignin depolymerization.

Nature, Published online: 16 April 2025; doi:10.1038/d41586-025-00967-7

Nature, Published online: 17 April 2025; doi:10.1038/d41586-025-01234-5

A continuous process for carbonylation reactions based on the online coupling of dry, high-temperature CO₂ electrolysis with a coil reactor has been reported. The strategy relies on producing CO/CO₂ mixtures onsite, without H₂ or H₂O entering the product gas, thus providing a safe and fast concept for the synthesis of several carbonyl compounds. The method demonstrated widespread applicability in amino-, alkoxy-, and phenoxycarbonylation, in carbonylative Sonogashira couplings, and in the synthesis of redox-active esters. The corresponding products were isolated with excellent yields in just 40 min.

Abstract

Despite being widely available, the broad utilization of CO₂ for chemical production remains in its infancy. The difficulty of using CO₂ as an important resource for the chemical industry lies in the high stability of the molecule and its associated inertia. In this work, we demonstrate how to overcome these limitations by utilizing a solid oxide electrolysis cell (SOEC) with an optimized cathode to produce dry CO through the high-temperature electrolysis of CO₂. We further integrate this process with a synthesis setup in a continuous-flow coil reactor to boost reactivity in various carbonylation processes, including in amino-, alkoxy-, and phenoxycarbonylation, carbonylative Sonogashira couplings, or the synthesis of redox-active esters. Ultimately, our approach offers a platform strategy for the rapid, scalable, and continuous production of carbonyl compounds directly from CO₂ while eliminating the requirement for storing large CO quantities.

A dual circularity concept was demonstrated to prevent plastic waste accumulation, where rational design paved the way. Apart from fully recovery of mechanical and thermal properties after as many as six repeated mechanical recycling cycles, the polyesters could be closed-loop chemical recycled via facile, time and energy efficient manners. In case of polymers with dual circularity, it is recommended to proceed with mechanical recycling when we can, switch to chemical recycling when we must.

Abstract

The plastic waste accumulation requires facile yet effective solutions. Currently mechanical recycling typically leads to downcycling, while the environmental footprint of chemical recycling is often unacceptable. Here, we introduce a dual circularity concept, where rational molecular design paves the way for complementary closed-loop mechanical and chemical recyclability under mild conditions. Very small changes in macromolecular structures, thermal and mechanical properties were observed, after as many as six repeated mechanical recycling cycles, showing that a wide processing window could be the key for closing the mechanical recycling loop. Facile, time and energy efficient closed-loop chemical recycling into products with identical performance to original ones was also realized, thanks to the abundant free volume and accessible ester-functionalities. With these design criteria at hand, dual circulation in recyclability can be realized; proceeding with mechanical recycling when we can, and switching to chemical recycling when we must.