Platform Molecules Research Articles

Acetalization strategy in biomass valorization: a review

Acetalization serves as both a synthesis tool for renewable cyclic acetal fuel additives and a protection strategy to improve selectivity in biomass conversion.

Electrocatalytic conversion of biomass-derived furan compounds: mechanisms, catalysts and perspectives.

Renewable biomass, with its abundant resources, provides a viable solution to address the energy crisis and mitigate environmental pollution. Furan compounds, including 5-hydroxymethylfurfural (HMF) and furfural (FF), serve as versatile platform molecules derived from the degradation of lignocellulosic cellulose, offering a crucial pathway for the conversion of renewable biomass. The electrocatalytic conversion of furan compounds using renewable electricity represents an enticing approach for transforming them into value-added chemicals. However, the complex chemistry of furan compounds leads to low selectivity of the target product, and the lower current density and Faraday efficiency make it difficult to achieve molded applications. Therefore, it is crucial to gain a better understanding of the mechanism and conditions of the reaction, enhance reaction activity and selectivity, and indicate the direction for industrial applications. Herein, we provide a comprehensive review of the recent advancements in the electrocatalytic of HMF and FF, focusing on mechanisms and pathways, catalysts, and factors affecting like electrolyte pH, potential, and substrate concentration. Furthermore, challenges and future application prospects are discussed. This review aims to equip researchers with a fundamental understanding of the electrochemical dehydrogenation, hydrogenation, and hydrolysis reactions involving furan compounds. Such insights are expected to accelerate the development of cost-effective electrochemical conversion processes for biomass derivatives and their scalability in large-scale applications.

Aerobic bimetallic catalysis for oxy-alkynylation of allenes

An aerobic double functionalization of 2,3-allenoic acids with terminal alkynes has been achieved affording versatile 4-alkynylfuran-2(5H)-one derivatives, which have been demonstrated as platform molecules for synthesis of useful natural products.

2-Methylimidazole-modulated 2D Cu metal-organic framework for 5-hydroxymethylfurfural hydrodeoxygenation.

Preparation of the high value-added chemical 2,5-dimethylfuran (2,5-DMF) from the biomass-derived platform molecule 5-hydroxymethylfurfural (HMF) is of great significance in the preparation of biofuels. Here, a bottom-up strategy was used to prepare a metal-organic framework (MOF) material with a two-dimensional nanosheet morphology, named CPM, in which an additive 2-methylimidazole was introduced into the hydrothermal process of Cu2+ ions and terephthalic acid. Subsequently, CPM-700 prepared by heat treatment under an inert atmosphere showed excellent catalytic performance in the reaction of HMF hydrodeoxygenation to 2,5-DMF. The materials before and after pyrogenation were characterized by PXRD, XPS, TEM, N2 adsorption and desorption and so on. It was confirmed that compared with the catalyst derived from the cubic MOF material self-assembled by Cu2+ and terephthalic acid, the morphology of 2D nanosheets was beneficial for the reaction of HMF to 2,5-DMF. Combined with the experimental data, the possible reaction path of 2,5-DMF preparation from HMF is that 2,5-dihydroxymethylfuran was formed by hydrogenation of the aldehyde group on the furan ring, and then 2,5-DMF was obtained by hydrogenolysis. This paper provides an effective route for 2D MOF-derived catalytic materials in the selective hydrogenation of HMF.

Synthesis of furfural from xylose using a choline chloride-based deep eutectic solvent and mechanistic insights

Choline chloride-based deep eutectic solvents can be used in the green synthesis of furfural, a platform molecule derived from biomass.

Heterogeneous catalytic oxidation of furfural with hydrogen peroxide over a niobia catalyst

Oxidation of furfural was conducted using niobia as a heterogeneous catalyst, which displayed an unconventional behavior, giving 2,3-dihydroxybutanedioic acid (tartaric acid) as the main oxidation product.

Modulating acid sites in Y zeolite for valorisation of furfural to get γ-valerolactone.

Furfural is a biomass-derived platform molecule that can be converted into a variety of useful products. Catalysts having appropriate balance between Lewis and Brønsted acid sites are suitable for valorisation of furfural. Lewis acidic metal ion incorporated zeolites were studied for this purpose. However, incorporating Lewis acidic metal ions into an alumino-silicate framework of a zeolite is a cumbersome process. Hence, an attempt has been made in this work to modulate the acid sites of Y zeolite via thermal treatment to effect controlled dealumination and use it for valorisation of furfural using isopropyl alcohol, which is a cascade transformation. The thermal treatment of zeolites changed the distribution of acid sites and increased the weak plus moderate to strong acid site ratio. Among the thermally dealuminated Y, beta and mordenite zeolites, with SiO2/Al2O3 ratio 5.2, 25 and 20, only Y zeolite could yield γ-valerolactone, the final product of the aimed cascade transformation. Complete conversion of furfural and 52% γ-valerolactone yield could be achieved under the optimized conditions using NH4Y zeolite thermally dealuminated at 700 °C (TY700). The better catalytic activity of TY700 could be correlated to a combination different factors such as framework structure, suitable weak plus moderate to strong acid site ratio, presence of both penta-coordinated and octahedral Al sites and balance between Brønsted and Lewis acid sites.

1,3-Butadiynyl sulfide-based compact trialkyne platform molecule for sequential assembly of three azides.

A compact trialkyne platform with a silyl-protected 1,3-butadiynyl sulfide moiety and a terminal alkyne group has been developed for sequential regioselective transition metal-catalyzed triazole formation reactions with three azides. This method enabled the facile construction of a low-molecular-weight triazole library and the synthesis of middle-molecular-weight trifunctional probes for protein modification.

Selective hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan over Ni–Ga intermetallic catalysts and its kinetic studies

5-Hydroxymethylfurfural (HMF) has been listed as the “TOP 14” most important biomass-derived platform molecules, which can be converted into 2,5-bis(hydroxymethyl)furan (BHF) via selective hydrogenation of the carbonyl group on HMF.

Directing charge transfer in a chemical-bonded Ni/Cd0.7Mn0.3S Schottky heterojunction for selective photocatalytic oxidation of benzyl alcohol structural organic platform molecules coupled with hydrogen evolution reaction

Solar-energy-driven half-reactions coupling is a vital photocatalysis strategy to simultaneously realize low-value organic platform molecules value-added conversion and hydrogen production. It is essential to design photocatalyst with appropriate band structures and efficient spatial separation of photogenerated hole/electron pairs (h+/e-) to drive reduction/oxidation half-reactions, respectively. Herein, chemical-bonded Ni/Cd0.7Mn0.3S Schottky junction was constructed via hydrothermal-chemical reduction method for sunlight-driven catalytic selective dehydrogenation oxidization of benzyl alcohol (BA) coupling with hydrogen evolution reaction (HER). The optimal 8% Ni/Cd0.7Mn0.3S exhibited excellent BA conversion rate (77%), benzaldehyde (BAD) yield (2.88 mmol·g−1·h−1), selectivity (99%) and HER activity (2.94 mmol·g−1·h−1). The selective oxidation of BA and its para-substituents (-CH3, -OCH3, -Br, -NO2) proceeded a carbon-centred radical mechanism via the cleavage of αC-H bond. Furthermore, the Ni/Cd0.7Mn0.3S exhibits excellent selective oxidation of the other organic platform molecules with benzyl alcohol structure, such as 5-hydroxymethylfurfural (HMF) and vanillyl alcohol (VAL), etc, validating that the chemical-bonded Ni/Cd0.7Mn0.3S possess the excellent performance in αC-H bond activation of benzyl alcohol structure unit. By combining experiment and DFT calculation results, the Ni-S bond formed at Ni/Cd0.7Mn0.3S interface can accelerate the directing charge transfer, thus boosting the organic platform molecules selective oxidation coupling with HER.

Characterization of Potential Dependent Fouling of Cu Electrodes during Electrochemical Hydrogenation and Hydrogenolysis of Furfural in Acid

Furfural (FF) is a platform molecule derived from biomass, that can be electrochemically reduced to produce furfuryl alcohol (FA), a furanic polymer intermediate, and 2-methylfuran (MF), a fuel candidate. On Cu in acidic media, it has been shown that FA and MF are produced via parallel reactions as opposed to a series reaction. Our previous work investigated the reactions for FA and MF production electrochemically with FF concentrations between 10 and 120 mM, showing positive order with respect to FF at low concentrations and zero order rates with respect to FF at higher concentrations. This finding suggesting non-competitive Langmuir-Hinshelwood mechanisms at concentrations of FF between 10 and 120 mM in pH 0 and 1 acidic solutions. At 200 mM concentrations of FF, we have identified fouling on the Cu surface. At moderate potentials, the fouling takes the form of a polymer material, whereas at more negative reduction potentials the fouling takes the form of graphitic coking. Understanding how fouling occurs on Cu electrodes is important in achieving progress towards mitigating or reducing the impact of fouling through reactor setup and catalysts design.In this work, conditions that promote fouling were selected so that the fouling of Cu electrodes could be studied. The conditions were chronoamperometry at -560 or -700 mV RHE, 200 mM FF, 0.5M H2SO4, 20:80 vol% acetonitrile:water, for three hours durations. The Cu electrodes were reused for 3 experiments to further promote fouling and study the impact on the electrochemical performance. We showed that after reuse at -560 mV RHE, a polymeric material formed on the Cu electrode, while when reused at -700 mV RHE the electrode was instead covered in a coke like material. FTIR spectroscopy showed that the polymer formed at -560 mV resembled poly(furfuryl alcohol) while the coking substance showed broad absorbance, expected of coke like materials. To better understand the coke material formed at -700 mV, Raman spectroscopy was used. The material resembled graphitic disorganized carbon, with a D/G band intensity ratio of 0.652.

Electrocatalytic hydrogenation of 5-hydroxymethyfurfural reactions promoted by CuZn catalysts

Electrochemical hydrogenation of 5-hydroxymethylfurfural (HMF) is a particularly important and environmentally friendly route to achieve sustainable high-value chemicals and biomass-based fuels. Herein, electrocatalytic hydrogenation (ECH) reaction of HMF using CuZn catalysts prepared by electrochemical deposition method was declared. The electrochemical hydrogenation of HMF to 5-methyfurfuryl alcohol (MFA) in alkaline aqueous medium has an excellent yield and faraday efficiency, with a maximum of 0.086 mmol cm−2 h−1, which has not been reported before. The selectivity and efficiency of ECH reaction were affected by electrolyte pH. The results indicated that electrocatalytic hydrogenation were not simply related to the type of electrode catalyst, but also sensitive to electrolytes, which can give important guidance for electrocatalytic hydrogenation of biomass-based platform molecules.

Polymers from Cellulosic Waste: Direct Polymerization of Levoglucosenone using DBU as a Catalyst.

The bio-based platform molecule levoglucosenone (LGO) is now produced at multi-ton scale by the pyrolysis of cellulosic waste. As such it has become an industrially viable, non-petroleum-derived chemical feedstock. Herein we report the direct (one-step) and operationally simple polymerization of LGO that provides a highly sustainable method for polymer synthesis. Specifically, the ability of LGO to act as an electrophile has been harnessed so as to deliver high molecular weight polymers (Mn=236,000 g/mol, Đ=2.4) possessing excellent thermal stabilities (TD5 %=249 °C). Furthermore, there is a significant capacity for the effective chemical manipulation of these polymers as exemplified by treatment of them under Baeyer-Villiger conditions and so creating a simple and green route to hydrophilic materials. These one- and two-step transformations provide the most direct route to new, LGO-derived polymer scaffolds yet reported. E-factors of ca. 0.012 and atom economies of up to 99 % have been realized.

Gamma-valerolactone-enabled control chemoselective conversion of glucose to 1,6-anhydroglucose over HZSM-5 zeolite

Unraveling chemoselective catalysis in the upgrading of renewable biomass-derived molecules to fine chemicals and bio-fuels is particularly challenging. Here, we report an innovative strategy for the chemocatalytic conversion of glucose into 1,6-anhydroglucose, a high-value platform molecule, in γ-valerolactone (GVL) over HZSM-5 (50) zeolite. In this case, HZSM-5 (50) zeolite exhibits remarkable shape-selective catalytic performance with a high turn-over frequency (TOF) of 201.6 h−1 and a 1,6-anhydroglucose selectivity of 95.3%. Solvent effect study from both experimental and theoretical results suggests the usage of solvent GVL is particularly beneficial for glucose diffusion into the zeolite pore channel, accelerating the isomerization-dehydration process. Kinetic behavior description of glucose transformation to 1,6-anhydroglucose is developed to monitor the process, whereas a synergistic catalytic mechanism is elucidated in detail by density functional theory calculations. Such solvent-induce and shape-selective catalytic system provides a compelling strategy for highly selective production of 1,6-anhydroglucose as a biomass platform molecule.

Cooperative biomass-derived furfural synthesis and H2 evolution in one photoredox cycle over a MnxCd1-xS/Ti3C2 MXene Schottky junction structure

Selective and efficient photocatalytic transformation of biomass-derived platform molecules to high-value-added fuels or chemicals is a great challenge for green chemistry, especially utilizing visible light energy and earth-abundant catalytic materials. In this work, we report a 1D/2D MnxCd1-xS/Ti3C2 (MCSTC-X) Schottky junction structure to achieve efficient photocharge separation/transfer via in-situ interfacial self-assembly strategy. Under visible light illumination, the optimized MCSTC-7.5 catalyst enables the selective conversion of furfuryl alcohol into furfural with a production rate of 764.3 μmol·g−1·h−1, accompanied by water splitting into H2 with a generation rate of 756.5 μmol·g−1·h−1. Benefiting from the internal electric field in the Schottky junction structure, the efficient separation and transfer of photoinduced charge carriers are realized in one photoredox cycle. Moreover, a plausible reaction mechanism for the photocatalytic selective valorization of furfuryl alcohol to furfural and H2 evolution is proposed. Hopefully, this work would open a new avenue for sustainable and practical production of solar chemicals and fuels by rationally designing 1D/2D Schottky junction.

FexNiy/ SiO2-Al2O3 catalyzed hydrodeoxygenation of biorenewable platform molecules

A series of FexNiy/SA (SA = SiO2-Al2O3) catalysts were synthesized via solvothermal assisted deposition precipitation synthesis method and explored for low-temperature hydrodeoxygenation (HDO) reaction of methyl oleate into n-alkanes and vegetable oils. A comprehensive study on the effects of increasing iron oxide loading in catalyst samples, i.e., Fe1Ni1/SA, Fe3Ni1/SA, Fe5Ni1/SA and Fe7Ni1/SA, on the crystallographic, morphological, textual and surface chemical behavioural were investigated thoroughly using various spectroscopic techniques. The study disclosed excellent surface area, high acidic strength and reducibility of Fe1Ni1/SA catalyst due to the lowest Fe2+ or FeO species. In contrast, higher iron oxide loading leads to the accumulation of Fe2+ ions on the surface with reduced metal acid centres and diminished surface area. The catalytic conversion as well as C17-C18 selectivity in catalytic HDO was also scrutinised with particular reference to Fe2+/Fe3+ ion ratio. The obtained superior catalytic activity and C18 selectivity of Fe1Ni1/SA catalyst are due to the lowest Fe2+/Fe3+ ion ratio. However, the iron oxide loading increased the Fe2+/Fe3+ ion ratio, which ultimately decreased the catalytic activity. Thus, the role of Fe2+ species in the deactivation of catalyst was discussed in detail to establish conversion and selectivity control in the catalytic HDO pathway.

Incorporation of tin oxide nanoparticles on sulfonated carbon microspheres as a bifunctional catalyst for efficient conversion of biomass-derived monosaccharides to 5-Hydroxymethylfurfural and furfural

Effective production of versatile platform molecules 5-Hydroxymethylfurfural (HMF) and furfural (FF) from biomass-derived carbohydrates is of great importance to synthesis of high-value-added bio-based chemicals and fuels. In order to highly efficient synthesis of HMF and FF, in this work, by integrating tin oxide nanoparticles with sulfonated carbon microspheres, a novel solid acid catalyst (SnOx-NPs@SC) with tunable Lewis/Brønsted acidity was developed for the conversion of glucose and xylose to HMF and FF, respectively. Characterization and experiment revealed that optimization of Sn precursor dosage and pyrolysis temperature was beneficial to the integration of SnOx with sulfonated carbon microspheres and formation of appropriate acid strength and balanced Lewis/Brønsted acid, which could enhance the selective conversion of glucose and xylose to HMF and FF. In the H2O/THF biphasic solvent system with 1.5 mol/L NaCl, the optimized catalyst (0.35-SnOx-NPs@SC-500) exhibited excellent catalytic performance by achieving 90.2% selectivity of HMF at 180 ℃ for 2 h and 85.4% selectivity of FF at 170 ℃ for 2 h, and displayed relatively high stability in five consecutive experimental cycles. The mechanism was discussed based on the physicochemical properties of the catalyst and reaction system. The results of this work provide an effective strategy for designing a bifunctional solid acid catalyst for the one-pot production of highly value-added biomass intermediates.

The Role of Surface Complexes in Ketene Formation from Fatty Acids via Pyrolysis over Silica: from Platform Molecules to Waste Biomass.

Fatty acids (FA) are the main constituents of lipids and oil crop waste, considered to be a promising 2G biomass that can be converted into ketenes via catalytic pyrolysis. Ketenes are appraised as promising synthons for the pharmaceutical, polymer, and chemical industries. Progress in the thermal conversion of short- and long-chain fatty acids into ketenes requires a deep understanding of their interaction mechanisms with the nanoscale oxide catalysts. In this work, the interactions of fatty acids with silica are investigated using a wide range of experimental and computational techniques (TPD MS, DFT, FTIR, in situ IR, equilibrium adsorption, and thermogravimetry). The adsorption isotherms of linear and branched fatty acids C1-C6 on the silica surface from aqueous solution have been obtained. The relative quantities of different types of surface complexes, as well as kinetic parameters of their decomposition, were calculated. The formation of surface complexes with a coordination bond between the carbonyl oxygens and silicon atoms in the surface-active center, which becomes pentacoordinate, was confirmed by DFT calculations, in good agreement with the IR feature at ∼1680 cm 1. Interestingly, ketenes release relate to these complexes' decomposition as confirmed by the thermal evolution of the absorption band (1680 cm-1) synchronously with the TPD peak of the ketene molecular ion. The established regularities of the ketenezation are also observed for the silica-induced pyrolysis of glyceryl trimyristate and real waste, rapeseed meals.

Urban waste upcycling to a recyclable solid acid catalyst for converting levulinic acid platform molecules into high-value products

The conversion of levulinic acid (LA) into alkyl levulinates is highly significant due to the wide range of applications for these products, including their use as fuel additives, solvents, and fragrances. In order to meet the growing need for environmentally friendly chemical production, this study takes a circular economy approach by upcycling a common urban waste, i.e., pine needles, to synthesize a robust heterogeneous acid catalyst, subsequently used to efficiently upgrade LA into levulinates. By utilizing a single-step procedure under mild operating conditions, the resulting PiNe–SO3H catalyst demonstrated good performances and flexibility in synthesizing diverse bio-derived levulinates. In fact, the catalyst showed an exceptionally broad range of applicability, resulting in isolated yields ranging from ̴ 46% to ̴ 93%, which is an unprecedented achievement. The catalyst's ability to be reused was tested, revealing remarkable performance for up to 10 consecutive cycles with negligible loss in efficiency. Additionally, a significant focus was directed towards developing a method that minimizes waste during the isolation process. This involved optimizing reaction conditions and rationalizing work-up procedures, resulting in low Environmental factor (E-factor) values ranging from 1.2 to 8.9. To comprehensively assess the overall environmental sustainability of the process, various additional green metrics were calculated, and the Ecoscale tool was employed as well. Furthermore, mechanistic investigations elucidated the favored reaction pathway, underscoring that, under the optimized conditions, the prevailing mechanism entails direct esterification, as opposed to the generation of a pseudo-ester intermediate.

Production of renewable mesitylene as jet-fuel additive: Reaction kinetics of acetone self-condensation over basic (TiO2) and acid (Al-MCM-41) catalysts

Sustainable production of jet fuel additives plays an essential role to decrease greenhouse gas emissions in the aviation industry. Acetone obtained from biomass fermentation is one of the platform molecules of the bio-refinery that can be used as raw material of newly developed sustainable processes. Mesitylene jet fuel additive can be obtained by acetone self-condensation reaction catalyzed by porous solids. In the present work, TiO2 and Al-MCM-41 have been chosen, respectively, as basic and acid catalysts, because of having some tolerance to deactivation. The reaction was studied in a continuous fixed-bed reactor operated in the gas phase at space velocities of 7900 mol/kg h for TiO2 and 5000 mol/kg h for Al-MCM-41. The influence of feed concentration (5–20% acetone and 0–5% mesityl oxide) and temperature (200–350 °C) was studied. First, the reaction scheme was assessed based on the product distribution. It was found that the acid catalyst Al-MCM-41 favors mesityl oxide decomposition to undesired isobutylene and acetic acid. Then, a mechanistic kinetic model of the different steps of the reaction scheme was developed and fitted the experimental results of each catalyst. This model constitutes a valuable tool for the scale-up of this process.