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Achieving quantitative conversion of biomass-derived feedstocks under ambient environmental conditions (20°C, atmospheric air, 0.1 MPa) is a critical milestone for sustainability in chemical processes. Herein, the quantitative conversion of glucose to gluconic acid was accomplished under ambient environmental conditions without any additives using a Pt-Zn intermetallic nanoparticle-supported biochar catalyst prepared from raw rice straw (Pt-Zn/strawC) via a straightforward one-pot solvothermal reaction with ethylene glycol solvent. Spectroscopic analyses verified the formation of the Pt-Zn intermetallic alloy and confirmed strong electronic metal-support interactions. The Pt-Zn/strawC catalyst (Pt:Zn molar ratio of 1:6) was highly selective for the conversion of glucose to gluconic acid, whereas yields as high as 99.9% (98.9% gluconic acid, 1.0% glucaric acid) were reached at 20 oC under base-free and additive-free conditions. Isotope measurements and density functional theory revealed synergistic interactions in the Pt-Zn alloy, wherein the alloy tended to absorb glucose and active O2 into superoxide radical (O2·). This work demonstrates a chemocatalytic method that is practical for environmental conditions and provides a new avenue for sustainable conversion of lignocellulosic biomass to chemical products.

An overview of solvent replacement strategies shows that there is great progress in green chemistry for replacing hazardous di-polar aprotic solvents, such as N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), and 1,4-dioxane (DI), used in processing active industrial ingredients (APIs). In synthetic chemistry, alcohols, carbonates, ethers, eucalyptol, glycols, furans, ketones, cycloalkanones, lactones, pyrrolidinone or solvent mixtures, 2-methyl tetrahydrofuran in methanol, HCl in cyclopentyl methyl ether, or trifluoroacetic acid in propylene carbonate or surfactant water (no organic solvents) are suggested replacement solvents. For the replacement of dichloromethane (DCM) used in chromatography, ethyl acetate ethanol or 2-propanol in heptanes, with or without acetic acid or ammonium hydroxide additives, are suggested, along with methanol acetic acid in ethyl acetate or methyl tert-butyl ether, ethyl acetate in ethanol in cyclohexane, CO2-ethyl acetate, CO2-methanol, CO2-acetone, and CO2-isopropanol. Supercritical CO2 (scCO2) can be used to replace many organic solvents used in processing materials from natural sources. Vegetable, drupe, legume, and seed oils used as co-extractants (mixed with substrate before extraction) can be used to replace the typical organic co-solvents (ethanol, acetone) used in scCO2 extraction. Mixed solvents consisting of a hydrogen bond donor (HBD) solvent and a hydrogen bond acceptor (HBA) are not addressed in GSK or CHEM21 solvent replacement guides. Published data for 100 water-soluble and water-insoluble APIs in mono-solvents show polarity ranges appropriate for the processing of APIs with mixed solvents. When water is used, possible HBA candidate solvents are acetone, acetic acid, acetonitrile, ethanol, methanol, 2-methyl tetrahydrofuran, 2,2,5,5-tetramethyloxolane, dimethylisosorbide, Cyrene, Cygnet 0.0, or diformylxylose. When alcohol is used, possible HBA candidates are cyclopentanone, esters, lactone, eucalytol, MeSesamol, or diformylxylose. HBA—HBA mixed solvents, such as Cyrene—Cygnet 0.0, could provide interesting new combinations. Solubility parameters, Reichardt polarity, Kamlet—Taft parameters, and linear solvation energy relationships provide practical ways for identifying mixed solvents applicable to API systems.

Ni–Ru bimetallic porous carbon sphere (Ni–Ru@PCS) catalysts were synthesized via formaldehyde-assisted, metal-coordinated crosslinking sol–gel chemistry, in which biomass-derived tannic acid and F127 surfactant were used as carbon precursor and soft template, respectively, and Ni2+ and Ru3+ were used as cross-linkers. In the developed method, Ni–Ru particles became uniformly dispersed in the carbon skeleton due to strong coordination bonds between metal ions (Ni2+ and Ru3+) and tannic acid molecules and bimetal interactions. The as-synthesized Ni–Ru10:1@PCS catalyst with a loading Ni:Ru mole ratio of 10:1 was applied for the selective hydrogenation of glucose to sorbitol, and provided 99% glucose conversion with a sorbitol selectivity of 100% at 140 °C in 150 min reaction time and exhibited good stability and recyclability in which sorbitol yield remained at 98% after 4 cycles with little or no metal agglomeration. The catalyst was applied to glucose solutions as high as 20 wt% with 97% sorbitol yields being obtained at 140 °C in 20 h. The developed bimetallic porous carbon sphere catalysts take advantage of sustainably-derived materials in their structure and are applicable to related biomass conversion reactions.

Combining terrestrial biomass with submarine-type hydrothermal environments for CO2 reduction is a possible approach for realizing new energies while achieving sustainable circulation of carbon. Herein, carbohydrate-enabled CO2 reduction based on NaHCO3 conversion to formate revealed that hydrothermal environments facilitated direct hydrogen transfer from carbohydrates (glucose, cellulose) to CO2/NaHCO3 with hot water (250–300 °C, 5–20 MPa) acting as homogeneous catalyst in absence of any conventional catalysts giving CO2/NaHCO3 reduction efficiencies as high as 76% for cellulose. Time-resolved operando hydrothermal DRIFTS spectra of glycolaldehyde in hot water (250 °C, autogenous pressure) verified that water catalyzed NaHCO3 reduction by converting the -CHO group in the carbohydrate to its hydrated state as -CH(OH)2, which enabled NaHCO3 reduction by direct hydrogen transfer and that the ratio of hydrogen transfer from water:glycolaldehyde for NaHCO3 reduction was about 13:87 on an atom basis. For cellulose exploited as energy input, a greater than 3.4% solar-to-formate efficiency can be theoretically attained, which is unprecedented compared with present literature values. These findings provide basic data for future studies on biomass-enabled CO2 reduction and broaden the scope of hydrothermal chemistry for developing net-zero emission processes.

Mechanisms of selective hydrolysis of alginates under hydrothermal conditions were investigated by comparing reactivities of sodium alginate (Na-ALG, 960 ku) solutions and calcium alginate (Ca-ALG) gels as substrates. Under hydrothermal conditions (150 °C), hydrolysis of Na-ALG gave product molecular weights of 223, 66, 26 and 17 ku while those of Ca-ALG gave product molecular weights of 340, 102, 45 and 31 ku for reaction times of 10, 20, 30 and 60 min, respectively. The ratios of mannuronic acid (M) to guluronic acid (G) varied only slightly (from 1.3 to 1.2) for Na-ALG over the range of reaction times at 150 °C, while ratios (M/G) for Ca-ALG exhibited a remarkable decrease (from 1.1 to 0.8). Diad sequence of alginate products obtained for Na-ALG were 17%, 23%, 27% and 31% (GG); 30%, 32%, 36% and 38% (MM); and 53%, 46%, 37% and 32% (GM+MG); while for Ca-ALG they were 18%, 22%, 24% and 33% (GG); 26%, 23%, 26% and 18% (MM); and 56%, 54%, 50% and 48% (GM+MG). Reaction mechanisms are proposed for hydrolysis of alginate solutions and alginate gels under hydrothermal conditions; de-polymerization of alginates into monomers and monomeric sequences can be controlled not only by hydrothermal conditions, but also by varying the physical state (solution, gel) of the starting materials.

Article highlights Carbonization (1 h, 400 °C, N2) of mix ball-milled (10 min) waste leaves and humic acid affords weak-acid biochars. As-prepared weak-acid biochars (–COOH, OH, amino groups) were activated solids with adsorptive and catalytic properties. Weak-acid biochar catalyst is reusable and promotes fructose dehydration to 5-HMF in yields of 77.5% (140 °C, 60 min).

Brønsted acid site (S/Cl)-functional carbon materials were prepared by ball-milling (bm) L-cysteine and ammonium chloride to form chemical complex solids, by post-heat treatment (Q) of the solids at 500 °C under a nitrogen gas atmosphere to stabilize and fortify amino and functional group solid structures and by post-oxidative treatment with H2O2 to add Brønsted acidity. The as-prepared carbon materials (S/Cl@bmxQy; x, y in hours) contained Brønsted acid sites (sulfonates, chlorides), oxygen-containing groups (-COOH, -OH) and amino functional groups. The S/Cl@bmxQy materials were applied as catalysts to promote conversion of fructose in ethanol solvent to 5-hydroxymethylfurfural (5-HMF) and 5-ethoxymethylfurfural (5-EMF). Among the carbon materials, S/Cl@bm3Q1 gave 5-EMF and 5-HMF yields of 67.0% and 22.8%, respectively, in pure ethanol at 140 °C for 24 h reaction time, while a reaction time of 18 h gave total 5-EMF and 5-HMF yields of 96.4%. Dimethyl sulfoxide (DMSO) was applied as additive to the ethanol-fructose- S/Cl@bm3Q1 reaction system which showed that 5-HMF product selectivity could be controlled with DMSO concentration. The protocol developed allows simple preparation of functional carbon materials that have high catalytic activity and are effective for conversion of fructose to 5-HMF and 5-EMF in ethanol.

Processes for efficient production of primary, secondary or ternary aminated compounds are constant challenges for chemical and pharmaceutical industries. Here, the authors develop selective and sustainable amination chemistry widely applicable to chemical substrates via formic acid.

A highly CO2-tolerant green alga, Chlorococcum littorale, was investigated at temperatures ranging from 8 to 28 °C, light intensities from 30 to 170 μmol m−2 s−1, a constant CO2 concentration of 5% (v/v) and atmospheric pressure. The experimental results showed that a specific growth rate μ, defined in terms of cell growth rate under a logarithmic growth phase, increased with temperature up to the maximum value (ca. 22 °C), while the μ decreased at higher temperatures. These promotion and inhibition of the cell growth rate were expressed by both a multiple linear regression and a mathematical model taking account of the Arrhenius activation/deactivation energies. Light intensity affected on the cell growth was independently treated in the mathematical model. The proposed growth model agreed well with the experimental data to within 6.6 %, which provides good correlation for both temperature and light intensity effects on the microalgal cell growth.