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Lignin, a crucial component of lignocellulosic biomass, holds immense promise for advancing biorefineries and producing sustainable energy alternatives. This study engineered a CN/rGO/BMO (2 : 1) heterojunction photocatalyst with varying Pd NP loading to selectively target the hydrogenolysis of challenging C–O ether bonds in lignin model compounds. Specific focus was on β-O-4, α-O-4, and the formidable 4-O-5 linkages. The 4-O-5 linkage, due to its high dissociation energy, poses a significant challenge. Electrochemical and spectral analyses unveiled improvements in charge separation, leading to delayed recombination of charge carriers in the heterojunction photocatalyst. Decorating the heterojunction with Pd NPs exhibited an elevated work function and a low Fermi energy level, facilitating the accommodation of photogenerated electrons and enabling efficient H2 dissociation. Such enhancement facilitated the cleavage of all three linkages, including the resistant 4-O-5 bonds under ambient conditions. The photocatalyst exhibited effective cleavage, yielding aromatic (toluene, phenol, ethylbenzene) and aliphatic (cyclohexane, ethylcyclohexane) products. Selectivity modulation was achieved by adjusting the time, hydrogen pressure, and Pd loading. Furthermore, this photocatalytic approach successfully transformed simulated lignin bio-oil containing all three linkages into valuable monomers. The alcoholic solvents efficiently harnessed photogenerated holes and prevented electron–hole recombination. The photocatalyst also demonstrated the capability to produce monomers from the native lignin extracted from teak wood sawdust. Emphasizing the focus on the reaction pathway and mechanism, scavenging studies and analyses were conducted, including UPS and VBXPS, to establish the Z-scheme charge transfer mechanism within the heterojunction. These findings provide a sustainable and efficient pathway for lignin valorisation in biorefineries, significantly contributing to the advancement of green fuels and aligning with the principles of green chemistry. [ABSTRACT FROM AUTHOR]

Fast-growing plants with a high carbon fixation capability are promising candidates for mitigating climate change and serving as a renewable resource to replace fossil fuels. Nonetheless, their short lifespan and extensive use lead to the significant accumulation of underutilized waste. While conventional thermal energy extraction remains dominant in biomass utilization, the lack of appropriate carbon capture and storage techniques results in unavoidable CO2 emissions. In contrast, the fine reforming of lignocellulosic biomass offers the potential to reduce CO2 emissions. However, the polymeric, complex and rigid structure of lignocellulosic biomass poses challenges, necessitating energy-intensive pretreatment, where the balance between wood particle size reduction (and thus energy consumption) and pretreatment duration is often overlooked. Herein, we developed a facile energy-saving microwave-hydrothermal method to advance the utilization of fast-growing Paulownia. The optimized sugars (xylose and glucose) after pretreatment can be further converted to formate via a hybrid electrolysis process with the cogeneration of green hydrogen. Both xylose and glucose can be readily converted to formate with high yield and selectivity. This process can be directly powered by PV panel without the safety concerns of hydrogen crossover because oxygen evolution is greatly suppressed. This solar-driven hybrid electrolysis of pretreated Paulownia suggests a pathway to cogenerate green chemicals and green fuels from fast-growing woods while also storing energy from renewable sources in chemical bonds. Overall, this novel synthesis process for green chemicals contributes to the decarbonization efforts and sustainable development initiatives. [ABSTRACT FROM AUTHOR]

A sustainable upgrading of renewable bulk materials, obtained by decomposition of biomass lignocellulose, could facilitate their use in the industrial production of chemicals. Homogeneous ruthenium catalysis plays a fundamental role in this area. The review deals with the upgradation of lignocellulosic molecules through the formation of new C−C and C−N bonds. Selected examples of catalytic bond forming reactions reported until mid of 2023, include: (a) dehydrogenative based couplings of alcohols, (b) reductive amination of carbonyl compounds, (c) direct C−H functionalization of (hetero)aromatic compounds. These approaches fulfill the requirements of sustainability: application occurs without any previous substrate activation, thus reducing the production of waste. New chemicals containing the intrinsic molecular structure of lignocellulose substrates, showed a broad range of applications: green fuels, hydrogen carriers, monomers of polymers, intermediates of fine chemicals and pharmaceuticals. The results discussed in the review could inspire the reader to improve the valorization process, in terms of bio‐substrate scope as well as product complexity, through more strategic applications of the catalytic methods. [ABSTRACT FROM AUTHOR]

Using waste biomass as feedstock to obtain high value-added chemicals has attracted increasingly more attention from the viewpoint of sustainable development. A novel renewable bio-based solid acid (LFuS) was prepared by a two-step sulfonation of the phenol-formaldehyde condensation product of sodium lignosulfonate (LS-Na) and furfural derived from industrial and agricultural organic wastes. LFuS was then firstly employed as a catalyst for the selective esterification of glycerol (GL) with acetic acid (HOAc) to produce a fuel bio-additive, a mixture of glycerol diacetates (DAG) and glycerol triacetate (TAG). Using LFuS achieved a 98.0% conversion of GL with the selectivity to DAG + TAG of 94.1% under milder conditions. Additionally, the obtained LFuS also exhibited an excellent reusability in this reaction, and no loss in glycerol conversion was observed after five cycles, with the corresponding selectivity to DAG + TAG only decreasing from 94.1% to 90.0% after five cycles. The high concentration of acid sites and the polyphenolic structure of LFuS are responsible for its excellent catalytic performance and reusability in selective esterification of glycerol reaction. [Display omitted] [ABSTRACT FROM AUTHOR]

• Biohydrogen from biomass waste is a renewable, sustainable, and future fuel. • Emerging technologies are being investigated to increase the efficiency, and cost effectiveness of biohydrogen production. • Nanoparticles and value-added compounds may improve the techno-economic feasibility. • AI-driven automation and process optimization enhances the efficiency and sustainability through Managerial Decision Support. • The challenges in scaling the biohydrogen technology from lab to industry are examined along with future perspectives. The world's energy consumption is continuously increasing in developing and industrialized nations. However, the rapid depletion of fossil fuels and climate change issues has directed global researchers to think about alternative clean and cost-effective fuels using sustainable approaches to meet the world's energy demand. Biohydrogen production from lignocellulosic biomass (LCB) via dark fermentation is a valuable green fuel to address waste management problems and clean energy production. Further, hydrogen has advantages over other fossil fuels, including high calorific value, high energy efficiency, easy production, and environment friendly alternatives. Additionally, the gaseous emissions and global warming caused by biomass incineration can be decreased by utilizing biomass to produce biohydrogen. Although dark fermentation produces the most efficient and clean biohydrogen, the process's yield and production rate are very low. However, emerging technologies are being researched to increase efficiency and competitive biohydrogen production, especially with dark fermentation. Therefore, the current review emphasises recent developments in the dark fermentative process to enhance the biohydrogen yield and productivity, including various biomass pretreatment technologies, factors affecting the process efficiency, nanoparticles inclusion, bioaugmentation, metabolic engineering techniques, and techno-economic analysis of the biohydrogen generation from LCB. Further, challenges associated with the biohydrogen technology transfer from the lab scale to the industrial scale are examined and highlighted in the future direction of research. Biohydrogen can emerge as a future fuel provided there are low-cost hydrogen production technologies for large-scale efficient production, and policy implementation. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is the only renewable source of organic carbon, presenting a sustainable alternative to fossil fuels in the green production of value-added chemicals, transportation fuels, and polymeric materials. The process for converting biomass into desired end-products typically involves multiple steps through the formation of intermediate molecules or "platform chemicals". One such pivotal platform chemical is 5-hydroxymethylfurfural (HMF). Therefore, the efficient and selective conversion of biomass into HMF emerges as an imperative research focus. This review highlights the latest breakthroughs in the catalytic production of HMF from biomass and derivative sugars. An in-depth exploration of various synthesis pathways for HMF is provided, shedding light on the critical roles played by raw materials, catalysts, solvents, and operating conditions in influencing reaction performance. Central to the discussion is elucidating the mechanisms and active sites involved in HMF synthesis, with a spotlight on the synergy effects of Lewis acid and Brønsted sites within catalysts during the hydrolysis, isomerization, and dehydration phases of HMF production. The pivotal step of isomerization, which determines the reaction rate in HMF synthesis from biomass, is given particular attention. In conclusion, the review reflects on the state-of-the-art progress and charts out prospective avenues for enhancing HMF production from biomass. Through this, our ultimate aim is to guide future innovations in catalytic systems for HMF synthesis from biomass, fostering their swift transition into industrial applications. • Summarizing various raw materials, catalysts, and solvents for producing HMF. • Discussing roles and synergies of acid/base sites of catalysts for producing HMF. • The reaction mechanism of HMF synthesis was discussed in details. • Proposing future research trends and issues faced in industrialized production. [ABSTRACT FROM AUTHOR]