Production Of Platform Chemicals Research Articles

Tethered Alkylammonium Dications as Electrochemical Interface Modifiers: Chain Length Effect on CO2 Reduction Selectivity at Industry-Relevant Current Density.

The electrochemical reduction of CO2 (CO2RR) has the potential to be an economically viable method to produce platform chemicals synergistically with renewable energy sources. Copper is one of the most commonly used electrocatalysts for this purpose, as it allows C-C bond formation, yielding a broad product distribution. Controlling selectivity is a stepping stone on the way to its industrial application. The kinetics of the reaction can be modified to favor the rates of certain products quickly and inexpensively by applying additives such as ionic liquids and coelectrolytes that directly affect the electrocatalytic interface. In this work, we propose tethered tetraalkylammonium salts as double-charged cationic modifiers of the electrochemical double layer to control CO2RR product selectivity. A novel setup comprising a gas diffusion electrode (GDE) flow cell coupled with real-time mass spectroscopy was used to study the effect of a library of the selected salts. We emphasize how the length of an alkyl linker effectively controls the selectivity of the reaction toward C1, C2, or C3 products at high relevant current densities (Jtotal = -400 mA cm-2) along with the inhibition of the parasitic hydrogen evolution reaction. Standard long-term experiments were performed for quantitative validation and stability evaluation. These results have broad implications for further tailoring an effective catalytic system for selective CO2 reduction reaction.

Investigating the Inhibitory Factors of Sucrose Hydrolysis in Sugar Beet Molasses with Yeast and Invertase

Sugar beet molasses is a low-value byproduct from the sugar industry. It contains significant amounts of sucrose (approx. 50% (w/w)), which can be used for many different applications, for example, as feedstock for the production of fuel (as ethanol) and biobased chemicals such as 5-hydoxymethyl furfural (HMF). To produce platform chemicals, sucrose is hydrolyzed into its monomeric C6 sugars: glucose and fructose. When comparing the hydrolysis rates of molasses with a pure sucrose solution, the specific reaction rate is much slower (Qp/x,60min = 93 and 70 gprod L−1 h−1 gcell−1 for pure sucrose and crude molasses, respectively) at the same sucrose concentration (300 g/L) and process conditions. To clarify why molasses inhibits the enzymatic hydrolysis rate, the influence of its viscosity and inorganic and organic composition was investigated. Also, the effects of molasses and treated molasses on pure enzymes, invertase (from Saccharomyces cerevisiae, 0.05 mg/mL), compared with hydrolysis using whole cells of Baker’s yeast (3 mg/mL), were tested. The results indicate an inhibitory effect of potassium (Qp/x,60min = 76 gprod L−1 h−1 gcell−1), generally at high salt concentrations (Qp/x,60min = 67 gprod L−1 h−1 gcell−1), which could be correlated to the solution’s high salt concentrations and possibly the synergistic effects of different ions when applying concentrations that were four times that in the molasses. Also, the viscosity and sucrose purity seem to have an effect, where pure sucrose solutions and thick juice from the sugar mill yielded higher hydrolysis rates (Qp/x,60min = 97 gprod L−1 h−1 gcell−1) than molasses-type solutions with a higher viscosity (Qp/x,60min = 70–74 gprod L−1 h−1 gcell−1). Attempting to further understand the effects of different components on the invertase activity, an in silico investigation was performed, indicating that high salt concentrations affected the binding of sucrose to the active site of the enzyme, which can result in a lower reaction rate. This knowledge is important for future scale-up of the hydrolysis process, since reduced hydrolysis rates require larger volumes to provide a certain productivity, requiring larger process equipment and thereby higher investment costs.

Liquid Hot Water (LHW) and Hydrothermal Carbonization (HTC) of Coffee Berry Waste: Kinetics, Catalysis, and Optimization for the Synthesis of Platform Chemicals

Colombia is the world’s leading producer of mildly washed arabica coffee and produces 12.6 million bags of green coffee, but at the same time, 784,000 tons of waste biomass are dumped in open fields, of which only 5% is recovered or used. The objective of this project was to evaluate the production of platform chemicals from these coffee wastes for sustainable resource management. To achieve this, biomass characterization was carried out using proximate analysis, ultimate analysis, and structural analysis. Hydrothermal valorization was carried out at a temperature range of 120–180 °C (LHW) and 180–260 °C (HTC) for one hour. The platform chemicals obtained were quantified by HPLC-RI and monitored by pH and conductivity, and the solid fraction was characterized by monitoring the functional groups in IR spectroscopy and elemental analysis. Hydrolysis processes were obtained at 150 °C, production of platform chemicals at 180 °C, and maximum concentration at 180 °C-4 h; over 200 °C, degradation of the products in the liquid fraction starts to take place. Homogeneous basic and acid catalysts were used to improve the yields of the reaction. The kinetics of the hydrolysis of lignocellulosic structures to sugars were also analyzed and described, and reaction orders of 1 (LHW), 3 (HTC), and their respective reaction rate equations were reported.

The Impact of Sulfur-Containing Inorganic Compounds during the Depolymerization of Lignin by Hydrothermal Liquefaction of Black Liquor.

Lignin is a promising resource for the sustainable production of platform chemicals and biofuels. The paper industry produces large quantities of lignin every year, mostly dissolved in a black liquor. With the help of hydrothermal liquefaction, black liquor can be used directly as a feedstock to depolymerize the lignin to desired products. However, because various cooking chemicals (e.g., NaHS, NaOH) used in the Kraft process, dominant in the paper industry, are also dissolved in the black liquor, it is necessary to study in detail their influence on the process as well as their fate. In this work, the focus was on the fate of sulfur and the influence of sulfide (HS-). For this purpose, hydrothermal liquefaction experiments (250-400 °C) were carried out with black liquor and self-prepared model black liquor with different sulfide concentrations (0-3 g·L-1 HS-) in batch reactors (V = 25 mL), and the products were analyzed to understand the chemical pathways involving sulfur. It was found that the inorganic sulfur compounds react with organic matter to produce organic sulfur compounds. Dimethyl sulfide is the most abundant of these products. The HS- concentration correlates with the amount of dimethyl sulfide produced. Because methanethiol has also been qualitatively detected, the reaction mechanism of Karnofski et al. for the formation of dimethyl sulfide in the Kraft process also applies to the hydrothermal liquefaction of black liquor. Increased sulfide concentration in the feed leads to an accelerated depolymerization of lignin. In contrast, the yields of some aromatic monomers decrease slightly, possibly as a result of repolymerization reactions also occurring more quickly.

Integrated preparation of functional lignin nanoparticles and levulinic acid directly from the pre-hydrolysis liquor of poplar wood

The pre-hydrolysis liquor (PHL) produced during pulp dissolution and biomass refining is mainly composed of hemicellulose and lignin, and it is a potential source for production of value-added materials and platform chemicals; however, their utilization has been a serious challenge. In this study, we proposed a green and simple strategy to simultaneously prepare size-controlled functional lignin nanoparticles (LNPs) and levulinic acid (LA) from PHL as the raw material. The as-prepared LNPs exhibited remarkable stability thanks to the presence of saccharides with abundant oxygen-containing groups and surface charges, which prevented aggregation and maintained long-term storage stability. Trace amounts of the LNPs (≤ 0.2 wt%) could stabilize various Pickering emulsions, even with oil-to-water ratios as high as 5:5 (v/v). Subsequently, the remaining PHL was directly used to produce LA without adding a catalyst; under optimal conditions (160 °C and 1 h), the yield of LA was 56.3 % based on the dry saccharide content in the raw PHL. More importantly, p-toluenesulfonic acid (p-TsOH), the only reactive reagent used during the entire preparation process, including the two preparation steps of the LNPs and LA, was reusable, and the recovery rate was >70 % after five cycles. Overall, this green and simple strategy effectively and comprehensively utilized the PHL and showed potential for producing biobased nanomaterials and platform chemicals.

Emergence of biomass-derived single-atom catalysts for platform chemicals production

Emergence of biomass-derived single-atom catalysts for platform chemicals production

Semi-continuous subcritical hydrolysis of orange waste biomasses for integrated production of fermentable sugars and platform chemicals

Results for the obtaining of fermentable sugars (FSs) and platform chemicals (PCs) from the subcritical hydrolysis of orange wastes (peel and bagasse) are presented. Unlike what is typically reported in similar studies involving lignocellulosic biomasses, the hydrolysis process was performed in a semi-continuous configuration, which allowed the examination of how temperature (180 to 220 °C) and pressure (15 to 25 MPa) influenced the compounds’ kinetic profile. Furthermore, studies have been found that evaluated these points for such biomasses. The best yields of hydrolyzed solution were obtained for biomasses pretreated by soxhlet with hydrolysis conducted at 180 °C and 15 MPa (orange peel, OP) and 200 °C and 20 MPa (orange bagasse, OB), yielding 5.31 and 4.26 g (100 g biomass)−1, respectively. Among the FSs, xylose was the monosaccharide predominantly obtained for both biomasses: 21.12 g L−1 for OP pretreated with SCO2 (hydrolysis at 180 °C and 15 MPa); and 24.45 g L−1 for untreated OB (hydrolysis at 220 °C and 25 MPa). Regarding the PCs, furfural was the main compound obtained for both biomasses: 10.86 g L−1 for untreated OP and 7.33 g L−1 for OB pretreated with SCO2, with both hydrolysis conducted at 220 °C and 25 MPa.

Biofilms for Production of Chemicals and Energy.

The twenty-first century will be the century of biology. This is not only because of breakthrough advances in molecular biology tools but also because we need to reinvent our economy based on the biological principles of energy efficiency and sustainability. Consequently, new tools for production routines must be developed to help produce platform chemicals and energy sources based on sustainable resources. In this context, biofilm-based processes have the potential to impact future production processes, because they can be carried out continuously and with robust stationary biocatalysts embedded in an extracellular matrix with different properties. We review productive biofilm systems used for heterotrophic and lithoautotrophic production and attempt to identify fundamental reasons why they may be particularly suitable as future production systems. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering , Volume 15 is June 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Efficient tunable approach for 5-(hydroxymethyl)furfural and 2,5-diformylfuran production from fructose in DMSO with bromide catalysis

This work describes a simple method for the preparation of 5-hydroxymethylfurfural (HMF) by dehydrating fructose in DMSO, either with the use of an affordable catalyst or in a catalyst-free manner. This process can be accompanied, under harsh conditions, by the bromide-catalyzed Kornblum oxidation of the hydroxyl group by the solvent, resulting in the formation of 2,5-diformylfuran (DFF). The optimized techniques presented in this study can serve as a foundation for the production of valuable biobased furanic platform chemicals from renewable sources in any laboratory, stimulating the development of sustainable chemistry and research in related fields worldwide.

Green Chemistry of the Future: Co-Electrosynthesis of Biobased Platform Chemicals and Hydrogen

The European Green Deal sends a strong signal for a climate-friendly and CO2-neutral economy. An important aspect to support this is a sustainable and reduced use of resources as well as efficient and green conversion technologies for renewable value-added products. For this reason, electrosynthetic approaches become increasingly important, as electrochemistry fulfils several criteria of green chemistry and offers the possibility to directly use current from renewable energy sources [3]. However, electrolysis and electrosynthesis currently often require the use of platinum group metals (PGM) and need separators, which are mostly based on perfluorinated and polyfluorinated alkyl substances (PFSA). Classical water electrolysis for production of green hydrogen also requires high overvoltage’s, which is due to the oxygen evolution reaction (OER). This is where coupling systems come in, in which the sluggish OER is replaced by a thermodynamically more efficient reaction, such as the electrooxidation of organic substances (EOO). An example of this is the electrooxidation of biobased 5-HMF or various sugars (xylose, glucose) to platform chemicals. When coupled with the hydrogen evolution reaction (HER), the EOO of 5-HMF to 2,5-furandicarboxylicacid (FDCA) requires a theoretical cell voltage of 0.3 V. In contrast, theoretical cell voltages of 1.23 V are required for the OER/HER [5]. With the focus on sustainable and energy-efficient systems, the simultaneous production of platform chemicals and green H2 via paired electrolysis offers high potential. [1-7]Previous studies have mainly focused on electrode materials, morphology and its electrocatalytic activity in divided batch cells. A strongly alkaline environment is considered advantageous for the electro-organic oxidation reaction, while the HER is reported to be kinetically slower in alkaline than in acidic conditions. Overall, the coupled electrolysis of H2 and platform chemicals is described as a promising technology in the development stage. [5-7]In this context, the present research explores paired electrosynthesis of platform chemicals and H2 to advance sustainable and efficient energy sources. A central goal is the prototype development of an undivided flow reactor in TRL4. Particular attention will be paid to mild operating conditions (such as a mild-alkaline environment, low operating pressures and low temperatures), PGM-free catalysts and the elimination of PFSA materials. To achieve this goal, various milestones have been defined. Among them is the development of 3D electrodes with suitable and selective catalysts. These are to be electrochemically tested in a flow-through test cell on a laboratory scale. In order to create a basis for analysis, the electrode reactions were first investigated electrochemically in a typical divided H-cell and reference measurements were carried out on nickel-based materials. In this work, NiOOH sheet and foam electrodes were electrochemically produced and subsequently investigated by cyclic voltammetry (CV) followed by bulk electrolysis. On this basis, suitable analytics (HPLC, UV-VIS) were also determined to quantify and classify the derivatives of the electrosynthesis process. These pre-experiments form the basis for the ongoing development of initial concept ideas for a modular test cell that allows various materials and structures to be electrochemically investigated.Overall, this research contributes to advancing sustainable and efficient energy sources and enabling the production of platform chemicals from renewable raw materials. Acknowledgments The authors thank the European Union’s Horizon Europe research and innovation programme under grant agreement N° 101070856 ELOBIO (Electrolysis of Biomass) for funding.

Recovery of Bio-Based Fumaric Acid By Electrochemically Induced pH Shift Crystallization

The heterotrophic microbial production of platform chemicals is gaining increasing interest due to the growing need to replace fossil resources by renewable alternatives. Carboxylic acids such as fumaric acid are important building blocks for high-value bio-based chemicals [1]. Fumaric acid is used as an acidulant, as an antibacterial agent, and as a precursor for polymers and pharmaceuticals [2,3].A major challenge commercializing the microbial production route is the recovery and the purification of fumaric acid after fermentation. Bio-production of fumaric acid has not yet reached industrial scale due to high additive consumption during the acid- and base-induced pH shift in the downstream process. The inevitable co-production of saline waste deteriorates process economics further and raises ecological concerns.Therefore, we propose a new electrochemical downstream process, which reduces the use of pH adjustment agents [4]. This downstream process incorporates an electrolysis cell to adjust the pH value. During electrolysis, protons are produced at the anode and hydroxide ions are produced at the cathode by the electrochemical splitting of water. In conventional water electrolysis, protons or hydroxide ions migrate through a membrane to balance the charge in the electrolysis cell. Consequently, the pH value is constant in the electrolysis cell chambers. In pH shift electrolysis, a salt is added to the electrolyte. The salt provides additional ions to maintain electroneutrality in both electrolysis cell chambers. In this way, protons and hydroxide ions are retained in their respective chambers of the electrolysis cell and a pH difference is created between the anode and cathode. During acidification in the anode chamber, the fumaric acid salt from the fermentation is protonated. Subsequently, fumaric acid crystallizes in the electrolysis cell in high yields due to its low solubility. Afterwards, fumaric acid crystals can be easily separated from fermentation broth. Simultaneously, a base is produced at the cathode, which can be used to maintain a neutral pH in the fermentation. Consequently, saline waste production and its drawbacks are avoided.This work presents the pH shift with an electrolysis cell and the simultaneous crystallization of fumaric acid in the anode chamber. Next, the process is analyzed using on-line and off-line analytics such as Raman spectroscopy and high-performance liquid chromatography.[1] Bozell, J. J., & Petersen, G. R. (2010). Technology development for the production of biobased products from biorefinery carbohydrates - The US Department of Energy’s “Top 10” revisited. Green Chem, 12(4), 525-728. DOI: 10.1039/B922014C[2] Xu, Q., Li, S., Huang, H., & Wen, J. (2012). Key technologies for the industrial production of fumaric acid by fermentation. Biotechnol Adv, 30(6), 1685-1696. DOI: 10.1016/j.biotechadv.2012.08.007[3] Roa Engel, C. A., Straathof, A. J., Zijlmans, T. W., van Gulik, W. M., & van der Wielen, L. A. (2008). Fumaric acid production by fermentation. Appl Microbiol Biotechnol, 78, 379-389. DOI: 10.1007/s00253-007-1341-x[4] Kocks, C., Wall, D., & Jupke, A. (2022). Evaluation of a Prototype for Electrochemical pH-Shift Crystallization of Succinic Acid. Materials, 15(23), 8412. DOI: 10.3390/ma15238412

Modulating the Product Distribution of the Electrochemical Reduction of CO2 on Copper at Relevant Current Densities

The electrochemical reduction of CO2 (CO2RR) has the potential to be an economically-viable method to produce platform chemicals synergistically with renewable energy sources. Copper is one of the most used electro-catalysts for this purpose, as it allows carbon-carbon bond formation, crucial for broader product distribution. Despite great achievements, controlling selectivity is yet a stepping stone between R&D and an actual industrial application. Among others, a kinetic resolution could be applied to enhance the selectivity toward targeted products, for which exploiting available and inexpensive additives or co-electrolytes such as ionic liquids is a promising direction. Herein, we present an initial systematic analysis of the effect of various tetra alkyl ammonium salts on the CO2RR products distribution with the aim on ethylene, important industrial feedstock or building block. A selected ammonium salts of different alkyl chain length and number of charges provided very concise but sufficient chemical space to overview a structure-activity relationships, including changes in the reactions’ onset potentials and limiting currents. The overall experimentation progress was intensified by the employing a developed in our lab a gas diffusion electrode (GDE) cell, coupled to a mass spectrometer. This enabled to scan the selected library of salts during CO2RR under dynamic operations with detection of transients in real-time at relatively high current densities, between 10 to 400 mA/cm2, within further quantitative validation over standard long-term steady-state experiments. These results have broad implications for effectively stirring the CO2RR selectivity towards products containing either one or two carbon atoms.Key words: CO2, Electroreduction, Copper, Electrocatalysis, Modifiers, Real-time, GDE

Biorefining Twin Transition: Digitalisation for Bio-based Chemicals/Materials - Discovery, Design and Optimisation.

The article discusses the production of platform chemicals from various biological sources, including glycerol, lignin, cellulose, bio-oils, and sea products. It presents the results of catalytic and downstream processes involved in the conversion of these biomass-derived feedstocks. The experimental approaches are complemented by numerical descriptions, ranging from density functional theory (DFT) calculations to kinetic modellingof the experimental data. This multi-scale modelling approach helps to understand the underlying mechanisms and optimize the production of platform chemicals from renewable resources.

Semi-continuous hydrothermal processing of pine sawdust for integrated production of fuels precursors and platform chemicals

This research reports data for the integrated obtaining of fermentable sugars (FSs), bio-oil (BO), and hydro-char (HC) – all fuel precursors – as well as platform chemicals (PCs – acetic, formic, and levulinic acid, besides furfural, and hydroxymethylfurfural) through semi-continuous hydrothermal processing of sawdust from pine wood. The influence of temperature (260, 300, and 340 °C) and the water-to-biomass ratio (25 and 50 g H2O (g biomass)−1) were the parameters considered to evaluate the mass yields, kinetic profiles, and BO properties. For FSs (and PCs), a detailed analysis considering the kinetic profiles of obtaining cellobiose, glucose, xylose, and arabinose is presented. For the conditions evaluated, a distinct behavior concerning the process parameters was observed, where 7.11 and 9.28 g (100 g biomass)−1 of FSs and PCs were synergistically obtained, respectively, after 30 min, 20 MPa, 260 °C, and 50 g H2O (g biomass)−1. Contextually, 17.59 g (100 g biomass)−1 of BO was obtained at 340 °C and the same water/biomass ratio. FTIR analysis of the BO samples suggested the presence of aldehydes, carboxylic acids, ketones, hydrocarbons, ethers as well as aromatic, alcohols, and nitrogenous compounds. Similar HC yields were achieved among the conditions analyzed, where 24.68 g (100 g biomass)−1 were obtained at 340 °C and 50 g H2O (g biomass)−1 for a higher heating value of 29.14 MJ kg−1 (1.5 times higher than the in natura biomass).

FlowPhotoChem platform for sustainable chemical production

Current methods of producing platform chemicals like ethylene lead to the creation of a significant amount of pollution. Researchers in the FlowPhotoChem project are working to develop a new, more sustainable method of producing platform chemicals using carbon dioxide and concentrated sunlight, as Dr Pau Farràs explains.

Techno-economic analysis of developing miscanthus biorefinery for the production of platform chemicals and renewable resins

Biorefining to produce chemical materials is a viable path to a renewable and sustainable future. The energy crop Miscanthus is grown with high yield and low cost. In this study, platform chemicals (acetic acid, glycolaldehyde, and acetol) and novolac resins were produced using Miscanthus at a baseline plant capacity of 15 t/h. The profitability of different biochar applications (soil amendment, heat supply, and activated carbon) was investigated by mass balance and energy consumption analysis and economic assessment. The heat supply scenario had the best profitability with an internal rate of return (IRR), payback period, levelized cost, and minimum selling price of 24.5%, 4.32 years, CNY 8,480/t, and CNY 10,840/t. Sensitivity analysis showed that IRR was most sensitive to resin price, plant capacity, and capital costs. The minimum plant capacity with an IRR over 25% was 25 t/h. Monte-Carlo simulation results showed a low investment risk for soil amendment and heat supply scenarios.

Catalytic Conversion of Cellulose to 5‐Hydroxymethylfurfural: Advancements in Heterogeneous Catalysts and Cutting‐Edge Hydrolysis Strategies

AbstractThe catalytic conversion of lignocellulose‐derived carbohydrates, particularly cellulose, into 5‐hydroxymethylfurfural (HMF), holds significant potential as a crucial step in the sustainable production of valuable platform chemicals. This review presents the remarkable progress made in the field, with a specific emphasis on the role of heterogeneous catalysts, innovative methods for accelerating cellulose hydrolysis, and the design of flow reactor technologies. The distinctive properties and surface functionalities of catalysts facilitate the efficient breakdown of cellulose's intricate structure, thereby promoting selective hydrolysis leading to HMF formation. Therefore, this review comprehensively examines various categories of heterogeneous catalysts, including metal oxides/phosphates, zeolites, functionalized silica/carbon‐based materials, heteropolyacids (HPAs), and metal‐organic frameworks (MOFs), highlighting their unique mechanisms and performance in cellulose conversion. Furthermore, the review describes the intriguing progress in hydrolysis strategies (pretreatment techniques and advanced heating systems) that have been crucially involved in overcoming the challenges associated with cellulose recalcitrance and achieving enhanced HMF yields. The synergistic interactions between catalysts and innovative hydrolysis methods have played a central role in the breakthroughs within cellulose conversion technology. Another aspect covered in this work is the advancement in using fixed‐/fluidized‐bed reactors and slug microreactors for the continuous production of HMF. Lastly, the current challenges and future perspectives are presented to propose the dilemma and development direction for efficient cellulose‐to‐HMF conversion.

Elimination of editing plasmid mediated by theophylline riboswitch in Zymomonas mobilis.

Zymomonas mobilis is regarded as a potential chassis for the production of platform chemicals. Genome editing using the CRISPR-Cas system could meet the need for gene modification in metabolic engineering. However, the low curing efficiency of CRISPR editing plasmid is a common bottleneck in Z. mobilis. In this study, we utilized a theophylline-dependent riboswitch to regulate the expression of the replicase gene of the editing plasmid, thereby promoting the elimination of exogeneous plasmid. The riboswitch D (RSD) with rigorous regulatory ability was identified as the optimal candidate by comparing the transformation efficiency of four theophylline riboswitch-based backbone editing plasmids, and the optimal theophylline concentration for inducing RSD was determined to be 2 mM. A highly effective method for eliminating the editing plasmid, cells with RSD-based editing plasmid which were cultured in liquid and solid RM media in alternating passages at 37 °C without shaking, was established by testing the curing efficiency of backbone editing plasmids pMini and pMini-RSD in RM medium with or without theophylline at 30 °C or 37 °C. Finally, the RSD-based editing plasmid was applied to genome editing, resulting in an increase of more than 10% in plasmid elimination efficiency compared to that of pMini-based editing plasmid. KEY POINTS: • An effective strategy for curing CRISPR editing plasmid has been established in Z. mobilis. • Elimination efficiency of the CRISPR editing plasmid was enhanced by 10% to 20% under the regulation of theophylline-dependent riboswitch RSD.

Heterogeneous catalytic oxidation for lignin valorization into aromatic compounds over acid-redox bifunctional polyoxometalates

Lignin, as the largest renewable aromatic resource on the planet, has significant potential for the production of value-added platform chemicals. In this work, we synthesized a series of cesium-exchanged acid-redox bifunctional polyoxometalates (POMs) and evaluated their performance as catalysts for the depolymerization of birch lignin into low molecular weight aromatic compounds. The Cs3H2PMOV2O40 catalyst exhibited the highest activity, resulting in a monomer yield of approximately 13.6 %. Gel permeation chromatography (GPC), heteronuclear single quantum coherence (HSQC) spectroscopy, and gas chromatography-mass spectrometry (GC-MS) analysis confirmed the effective cleavage of β-O-4, β-5, and β-β linkages in the lignin polymer. The proposed reaction mechanism for the lignin depolymerization over cesium-exchanged POMs was also discussed. Our results demonstrate the potential of cesium-exchanged POMs as effective catalysts for the conversion of lignin into value-added chemicals, thereby contributing to the complete sustainable utilization of lignocellulose.

Metal catalyst-free selective acetosyringone synthesis from rice straw lignin.

In recent decades, due to abundance (second most abundant natural polymer after cellulose) and sustainability, lignin has attracted much interest from different researchers to use as a raw material for producing various value-added materials such as polymer and fuel. In addition to that, the aromatic structure of lignin makes it a suitable candidate for producing platform chemicals with aromatic rings. As a result, lignin depolymerization has become an interesting process to derive different phenolic monomers like vanillin, acetosyringone, and guaiacol. Among them, due to the bioactive characteristics and efficiency of acetosyringone in plant regulatory systems, the production of acetosyringone from lignin has been presented in this work. A green and cost-effective method was developed for the selective formation of acetosyringone via depolymerization of isolated rice straw lignin (RSL) by using metal catalyst-free conditions in the biphasic medium and described. The RSL was characterized with various spectroscopic techniques such as FT-IR, solid-state 13C NMR, XPS, and TGA. The selectivity of synthesized acetosyringone during depolymerization of RSL was checked from GC-MS analysis. The molecular structure and purity of acetosyringone isolated from preparative thin layer chromatography (TLC) were confirmed with the help of 1H NMR and HRMS, respectively.