Recent Developments in Heterogeneous Catalytic Routes for the Sustainable Production of Succinic Acid from Biomass Resources

Benzenoid Aromatics from Renewable Resources

In this Review, all known chemical methods for the conversion of renewable resources into benzenoid aromatics are summarized. The raw materials that were taken into consideration are CO2; lignocellulose and its constituents cellulose, hemicellulose, and lignin; carbohydrates, mostly glucose, fructose, and xylose; chitin; fats and oils; terpenes; and materials that are easily obtained via fermentation, such as biogas, bioethanol, acetone, and many more. There are roughly two directions. One much used method is catalytic fast pyrolysis carried out at high temperatures (between 300 and 700 °C depending on the raw material), which leads to the formation of biochar; gases, such as CO, CO2, H2, and CH4; and an oil which is a mixture of hydrocarbons, mostly aromatics. The carbon selectivities of this method can be reasonably high when defined small molecules such as methanol or hexane are used but are rather low when highly oxygenated compounds such as lignocellulose are used. The other direction is largely based on the multistep conversion of platform chemicals obtained from lignocellulose, cellulose, or sugars and a limited number of fats and terpenes. Much research has focused on furan compounds such as furfural, 5-hydroxymethylfurfural, and 5-chloromethylfurfural. The conversion of lignocellulose to xylene via 5-chloromethylfurfural and dimethylfuran has led to the construction of two large-scale plants, one of which has been operational since 2023.

Hydrothermal Valorization of Biosugars with Heterogeneous Catalysts: Advances, Catalyst Deactivation, Mitigation Strategies and Perspectives

Sustainable production of valuable biochemicals and biofuels from lignocellulosic biomass necessitates the development of durable and high-performance catalysts. To assist the next-stage catalyst design for hydrothermal treatment of biosugars, this paper provides a critical review of (1) recent advances in biosugar hydrothermal valorization using heterogeneous catalysts, (2) the deactivation process of catalysts based on recycling tests of representative biosugar hydrothermal treatments, (3) state-of-the-art understandings of the deactivation mechanisms of heterogeneous catalysts, and (4) strategies for preparing durable catalysts and the regeneration of deactivated catalysts. Based on the review, challenges and perspectives are proposed. Some remarkable achievements in heterogeneous catalysis of biosugars are highlighted. The understanding of catalyst durability needs to be further enhanced based on full examination of the catalytic performance based on the conversion of substrates, the yield, and selectivity of products. Further, a full examination of the physiochemical changes based on multiple characterization techniques is required to eclucidate the relationships between treatment variables and catalyst durability. Collectively, a clear understanding of the relationships between chemical reaction pathways, treatment variables, and the physiochemistry of catalysts is encouraged to be gained to advise the development of heterogeneous catalysts for long-term and efficient hydrothermal upgrading of biosugars.

PtFeCoNiCu High-Entropy Alloy Catalyst for Aqueous-Phase Hydrogenation of Maleic Anhydride

High-entropy alloys (HEAs), as new heterogeneous catalytic materials, possess remarkable catalytic performance in numerous reactions. However, rational and controllable synthesis of these complex structures remains a challenge. In this work, bulk and carbon nanotube (CNT)-supported ultrasmall PtFeCoNiCu HEA nanoparticles with an average particle size of 1.58 nm are prepared by lithium naphthalenide-driven reduction under mild conditions. The supported PtFeCoNiCu/CNT catalyst exhibits high catalytic activity in the aqueous-phase hydrogenation of maleic anhydride to succinic acid with a selectivity of 98% at full conversion of maleic acid (the hydrolysis product of maleic anhydride), a low apparent activation energy (E_a = 49 kJ mol^-1), and excellent stability. Moreover, a much higher mass-specific activity of Pt in the catalyst is displayed over PtFeCoNiCu/CNT (1515.4 mmol_maleic acid g_Pt^-1 h^-1) than that of 5 wt % Pt/CNT (388.0 mmol_maleic acid g_Pt^-1 h^-1). This work provides a strong support for HEAs as advanced heterogeneous catalysts and will be of great significance for promoting the research and application of HEAs in the field of selective hydrogenation.

Recent Approaches in the Catalytic Transformation of Biomass-Derived 5-Hydroxymethylfurfural into 2,5-Diformylfuran

The conversion of biomass into a great variety of valuable chemicals, polymers, and fuels gives a sustainable alternative for the insufficiency of non-renewable fossil fuel resources and reduces environmental pollution. 5-Hydroxymethylfurfural (HMF), converted from sustainable carbohydrates, is a significant building block chemical, and the selective oxidation of HMF into 2,5-diformylfuran (DFF) presents an ongoing challenge. DFF is a versatile platform molecule derived from biomass and has promising application in pharmaceuticals and polymers. This Review provides an overview of the latest developments of efficient catalytic systems for the sustainable conversion of HMF to DFF.

A Review on the Production of C4 Platform Chemicals from Biochemical Conversion of Sugar Crop Processing Products and By-Products

The development and commercialization of sustainable chemicals from agricultural products and by-products is necessary for a circular economy built on renewable natural resources. Among the largest contributors to the final cost of a biomass conversion product is the cost of the initial biomass feedstock, representing a significant challenge in effective biomass utilization. Another major challenge is in identifying the correct products for development, which must be able to satisfy the need for both low-cost, drop-in fossil fuel replacements and novel, high-value fine chemicals (and/or commodity chemicals). Both challenges can be met by utilizing wastes or by-products from biomass processing, which have very limited starting cost, to yield platform chemicals. Specifically, sugar crop processing (e.g., sugarcane, sugar beet) is a mature industry that produces high volumes of by-products with significant potential for valorization. This review focuses specifically on the production of acetoin (3-hydroxybutanone), 2,3-butanediol, and C4 dicarboxylic (succinic, malic, and fumaric) acids with emphasis on biochemical conversion and targeted upgrading of sugar crop products/by-products. These C4 compounds are easily derived from fermentations and can be converted into many different final products, including food, fragrance, and cosmetic additives, as well as sustainable biofuels and other chemicals. State-of-the-art literature pertaining to optimization strategies for microbial conversion of sugar crop byproducts to C4 chemicals (e.g., bagasse, molasses) is reviewed, along with potential routes for upgrading and valorization. Directions and opportunities for future research and industrial biotechnology development are discussed.

Strong Metal Phosphide-Phosphate Support Interaction for Enhanced Non-Noble Metal Catalysis

Strong metal-support interaction (SMSI) is crucial for supported catalysts in heterogeneous catalysis. Here is the first report on strong metal phosphide-phosphate support interaction (SMPSI). The key to SMPSI is the activation of P species on the support, which leads to simultaneous generation of metal phosphide nanoparticles (NPs) and core-shell nanostructures formed by support migration onto the NPs. The encapsulation state of metal phosphide and charge transfer are identical to those of classical SMSIs and can be optimally regulated. Furthermore, the strong interactions of Co₂ P_L /MnP-3 not only significantly enhance the anti-oxidation and anti-acid capability of non-noble metal but also exhibit excellent catalytic activity and stability toward hydrogenating a wide range of compounds into value-added fine chemicals with 100% selectivity, which is even better than Pd/C and Pt/C. The SMPSI construction can be generally extended to other systems such as Ni₂ P_L /Mn₃ (PO₄ )₂ , Co₂ P_L /LaPO₄ , and CoP_L /CePO₄ . This study provides a new approach for the rational design of advanced non-noble metal catalysts and introduce a novel paradigm for the strong interaction between NPs and support.

Lacerda T. Monomers and Macromolecular Materials from Renewable Resources: State of the Art and Perspectives

A progressively increasing concern about the environmental impacts of the whole polymer industry has boosted the design of less aggressive technologies that allow for the maximum use of carbon atoms, and reduced dependence on the fossil platform. Progresses related to the former approach are mostly based on the concept of the circular economy, which aims at a thorough use of raw materials, from production to disposal. The latter, however, has been considered a priority nowadays, as short-term biological processes can efficiently provide a myriad of chemicals for the polymer industry. Polymers from renewable resources are widely established in research and technology facilities from all over the world, and a broader consolidation of such materials is expected in a near future. Herein, an up-to-date overview of the most recent and relevant contributions dedicated to the production of monomers and polymers from biomass is presented. We provide some basic issues related to the preparation of polymers from renewable resources to discuss ongoing strategies that can be used to achieve original polymers and systems thereof.

Manganese-Doped Zinc Oxide Nanostructures as Potential Scaffold for Photocatalytic and Fluorescence Sensing Applications

Herein, we report the photocatalytic and fluorescence sensing applications of manganese-doped zinc oxide nanostructures synthesized by a solution combustion technique, using zinc nitrate as an oxidizer and urea as a fuel. The synthesized Mn-doped ZnO nanostructures have been analyzed in terms of their surface morphology, phase composition, elemental analysis, and optical properties with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and UV-Visible (UV-Vis) spectroscopy. A careful observation of the SEM micrograph reveals that the synthesized material was porous and grown in very high density. Due to a well-defined porous structure, the Mn-doped ZnO nanostructures can be used for the detection of ciprofloxacin, which was found to exhibit a significantly low limit of detection (LOD) value i.e., 10.05 µM. The synthesized Mn-doped ZnO nanostructures have been further analyzed for interfering studies, which reveals that the synthesized sensor material possesses very good selectivity toward ciprofloxacin, as it detects selectively even in the presence of other molecules. The synthesized Mn-doped ZnO nanostructures have been further analyzed for the photodegradation of methyl orange (MO) dye. The experimental results reveal that Mn-doped ZnO behaves as an efficient photocatalyst. The 85% degradation of MO has been achieved in 75 min using 0.15 g of Mn-doped ZnO nanostructures. The observed results clearly confirmed that the synthesized Mn-dopedZnO nanostructures are a potential scaffold for the fabrication of sensitive and robust chemical sensors as well as an efficient photocatalyst.