Green Chemistry最新文献

Enhancing the production of biochemicals from lignocellulosic biomass is one potential way to decrease society's dependence on fossil fuels. Aromatic compounds obtained from plant biomass can be used as substrates for microbial production of dicarboxylic acids such as 2-pyrone-4,6-dicarboxylic acid (PDC) and cis,cis-muconic acid, which are building blocks for the manufacturing of polymer-based fibers and materials. In this study, we used an engineered strain of the bacterium Novosphingobium aromaticivorans to investigate how to increase PDC productivity in flow-through bioreactors receiving aqueous solutions of aromatics. At the best operational conditions tested, we achieved stable PDC production rates of 0.77 g_PDC L⁻¹ h⁻¹ with p-hydroxybenzoic acid, 1.93 g_PDC L⁻¹ h⁻¹ with syringic acid, and 1.53 g_PDC L⁻¹ h⁻¹ with the products from alkaline pretreated poplar biomass. PDC titers in these reactors ranged from 7.7 to 15 g L⁻¹ (42 to 80 mM) and were limited by aromatic solubility in the case of syringic acid, or by accumulation of protocatechuic acid from p-hydroxybenzoic acid when high aromatic loading rates were used. The use of high aromatic loading rates, hollow-fiber membranes to concentrate the microbial cells, and NH₄OH for pH control were factors that contributed to this study achieving the highest PDC productivities reported to date. Overall, our findings demonstrate strategies that can be used to increase bioreactor productivity when aromatic substrates are delivered in aqueous form. These findings may also provide useful insight for production of other biochemicals from aromatic streams using N. aromaticivorans or other microbial chassis.

The use and consumption of electrodes is a crucial aspect regarding the overall efficiency and sustainability of electrochemical reactions. When metal electrodes are used, the cost of the material combined with the processing costs assumes relevance in terms of economics and sustainability. Herein we report a case study that aims to define an electrochemical synthetic protocol using electrodes prepared from recovered aluminium scrap. We approached the problem by evaluating and comparing the different carbon footprints associated with the use of different electrode materials from primary sources and secondary (recycled) sources. We optimized the use of electrodes made from secondary aluminium to develop a simple, oxidant-free protocol for the representative synthesis of 2-oxazolines from amino alcohols and aldehydes using generally elusive concentrated conditions and a recoverable reaction media. A further evaluation of the developed process using green metrics allowed us to quantify the waste distribution of our procedure in comparison with the literature processes as well as the progress in terms of sustainability and intrinsic reaction efficiency.

Fluoroform (CHF₃) is a byproduct of CHF₂Cl with high global warming potential and long atmospheric lifetime, and its efficient utilization is a great challenge. The mechanochemical reaction between CHF₃ and AlCl₃ was studied for the first time, and the resultant ACFs (AlCl_xF_3−x, x ≈ 0.1) were characterized by ion chromatography, X-ray photoelectron spectroscopy and X-ray diffraction. The reaction mechanism is revealed via experiments and DFT calculation. Here, the reactivity of AlCl₃ is slightly higher than that of AlCl₂F and AlClF₂, while the reactivity of CHF₂Cl and CHFCl₂ is 2 to 6 orders of magnitude higher than that of CHF₃. The reaction is self-accelerated until CHF₃ is fully converted to CHCl₃ and ACFs with controllable F-content. The present work provides a viable approach to convert CHF₃ to CHCl₃ and ACFs at ambient temperature and pressure, which is superior to the mainstream incineration technique with great energy demand and environmental pollution, and sacrifice of the precious F-resource.

Derived from lignocellulosic biomass, sustainable hard carbon has emerged as a promising low-cost anode material for sodium-ion batteries (SIBs). However, the intricate formation process of the hard carbon microstructure remains unclear. This study investigates the structural differences and pyrolysis behaviors of pine lignin and its graded variants obtained through a lignin molecular sieving engineering strategy. Moreover, it delves into the relationship between the microstructure of lignin-derived hard carbon and its sodium-ion storage characteristics. Pristine pine lignin, along with ethanol-isolated lignin, acetone-isolated lignin, and residual lignin, serves as a precursor for synthesizing hard carbon materials. Quantitative analysis via³¹P NMR spectroscopy reveals the highest content of polar functional groups in ethanol-isolated lignin. Interestingly, hard carbon derived from ethanol-isolated lignin exhibits the smallest closed pore volume, leading to the lowest plateau capacity of sodium-ion storage. Conversely, hard carbon derived from acetone-dissolved lignin displays the highest plateau capacity owing to its largest closed pore volume formed in the carbonization process. The origin of open and closed pore structures of hard carbons is thoroughly analyzed.

Selective oxidation of alcohols to aldehydes/ketones is an important reaction in the fine and bulk chemicals fields. However, the classical alcohol oxidation methods are often performed under unfriendly conditions or use stoichiometric oxidants. Herein, we report an ingenious system that enables high selectivity (up to 99%) and high conversion (up to 97%) with high reaction rates in the aerobic oxidation of alcohols to aldehydes/ketones for a broad range of alcohols, proceeding smoothly via mixing the solvent ethyl acetate and HBr under ambient conditions with visible light irradiation. Experimental characterization and theoretical calculations reveal that solvated dispersion intermediates are formed spontaneously in situ through noncovalent interactions among the molecules in the reaction system, which is proposed to be the origin of the high selectivity and high activity of this reaction. The dispersion system provides a feasible activation approach for aerobic oxidation of alcohols to aldehydes/ketones with high performance under visible light.

Biomass provides a promising source of carbon for obtaining environment-friendly carbon materials, but obtaining heteroatom-doped carbon materials (HDCMs) from biomass directly by a green method still remains challenging. This study successfully synthesized nitrogen and phosphorus co-doped porous carbon materials (Y-NPC) by the simple in situ pyrolysis of renewable yeast mixed with water from 800 to 950 °C. Various characterization methods show that nitrogen and phosphorus are doped into the carbon skeleton and mainly exist in the forms of graphite-N, pyridine-N, C–P, P–N, and P–O states. The catalyst Y-NPC-900 °C with a 3D hierarchical porous structure and high P–N content exhibited superior nitro hydrogenation performance and reaction stability using molecular hydrogen and hydrazine hydrate as hydrogen sources under mild conditions. Density functional theory (DFT) calculations and experiments attributed the exceptional catalytic performance to hydrogen activation and the good adsorption ability of substrates over N, P co-doped carbon (NPC). Therefore, this research proposes an eco-friendly and simple synthesis strategy for in situ N, P co-doping metal-free carbon catalysts derived from biomass, showing the significance of N, P co-doping and single N- or P-monodoping in the charge distribution of carbon materials.

2,5-Furandicarboxylic acid (FDCA) is one of the most promising biodegradable substitutes for fossil-derived terephthalic acid (PTA) and adipic acid. The production of FDCA from biomass-derived 5-hydroxymethylfurfural (HMF) is significant and has attracted great attention. However, the major challenge lies in the development of a non-precious metal-based catalyst system without employing a homogeneous base. Herein, we successfully prepared an atomically dispersed Fe–N–C/γ-Al₂O₃ catalyst, which affords superior catalytic performance in terms of activity and stability with a FDCA yield of 99.8% and reusability of five recycle times in the catalytic oxidation of HMF to FDCA under base-free mild conditions. Based on controlled experiments and complementary characterization studies, we found that the atomically dispersed medium-spin Fe–N₅ active sites together with the surface acidic/basic sites of alumina synergistically enhanced the catalytic activity and selectivity towards FDCA under base-free conditions. Our process eliminates the employment of expensive oxidants and corrosive bases, leading to economic and green biomass transformations.

N-Nitrosamines represent a class of bifunctional nitrogen-radical precursors, but their application potential remains largely unexplored. This study reports the highly atom-economical production of diverse α-oximino sulfonamides via direct photo-mediated radical relay oximinosulfonamidation of activated or unactivated alkenes with N-nitrosamines triggered by organic sulfide. N-Nitrosamines worked as bifunctional reagents in this transformation, simultaneously generating aminyl radicals and NO radicals. The organic sulfide was designed to act as a radical decaging agent as well as a source of sulfonyl. Its strong radical capturing ability and affinity for alkenes enable the rapid capturing of the aminyl radicals, thereby inhibiting the rapid recombination of radical pairs in the solvent cage. The synthesized oxime units could also be easily converted into other functional groups, leading to selective downstream transformations. The mild photodegradation reaction of harmful N-nitrosoamines showed high functional group tolerance and compatibility, facilitating the late-stage functionalization of natural products and drug molecules, expanding the biologically relevant chemical space.

A simple and recyclable homogeneous catalytic system for the hydrogenation of carbon monoxide to methanol was established. The reaction is catalyzed by a molecular manganese complex using a high-boiling alcohol as the solvent for catalyst immobilization. The CO hydrogenation is assisted by the product itself and the solvent through the formation of a methyl or dodecyl formate ester intermediate mediated by catalytic amounts of NaOMe as the base. This allows the catalytic formation of methanol in alcohols combined with facile product separation and catalyst recycling via distillation. Initial turnover frequencies (TOF) of 2250 h⁻¹ were reached under optimized conditions in 1-dodecanol/methanol as the reaction medium (T = 160 °C, p(H₂/CO) = 80/10 bar). The performance was stabilized in batch-wise recycling over 6 runs achieving a total turnover number (TTON) of >12 000 corresponding to an enhancement of more than five times compared to single batch operation under identical conditions. Minimal leaching of the components of the organometallic catalyst was observed during distillative product separation and catalyst activity could be fully restored by re-addition of the base NaOMe.

The development of electrocatalysts that convert CO₂ and N₂ in flue gas to directly usable urea does not only explore the hidden value of exhaust gas but also alleviates the global environmental issues caused by excessive CO₂ emissions; yet, related research studies are still in their infancy. Herein, multi-porous Cu–W₁₈O₄₉@ZIF-8, composed of ultra-small nanosized ZIF-8 on Cu-doped W₁₈O₄₉ nanowires, was fabricated as a urea-generation electrocatalyst in flue gas. It exhibits an appealing Faraday efficiency of urea up to 16.1% at −0.9 V (vs. RHE) and an outstanding yield of 1.33 mmol g⁻¹ h⁻¹ at −1.0 V (vs. RHE) under the flue gas atmosphere. The catalytic performance was maintained for a wide range of N₂ : CO₂ ratios. Theoretical calculations indicate that the doped copper regulates the electron density around the adjacent W–W, which facilitates N₂ adsorption, partly suppresses the HER side reaction, and decreases the ΔG of the following multi-step hydrogenation after *CO insertion until urea production.