Green Carbon最新文献

Zeolites are typically synthesized in alkaline or fluoride-containing near-neutral media. Sophisticated organic structure-directing agents have been investigated for such systems with the aim of discovering materials with unprecedented structures and properties for novel technical applications. In contrast, zeolite crystallization in strongly acidic media has yet to be explored. This study demonstrates that a zeolitic silicate phase crystallizes from acidic gels using trimethylamine as an organic additive with the composition 1 SiO₂:0.3 TMA:0.3 HCl: 0.15 HF:55 H₂O:(0.1–0.4) GeO₂. This phase has an interrupted four-connected framework analog to the octahedron/tetrahedron-mixed framework of the mineral family pharmacosiderite. In comparison to the pharmacosiderite-type HK₃(Ge₇O₁₆)(H₂O)₄, the four GeO₆-octahedra forming the central [HGe₄O₄O₁₂]-cluster are replaced by four SiO₄-tetrahedra in a [Si₄O₆(OH)_2.89]-unit in the new phase. However, the structure is distorted and may contain connectivity and point defects; thus, healing by the occasional incorporation of GeO₆-units is necessary. The refined unit cell has a cubic symmetry, space group P-43m (#215), with a = 7.7005(1) Å. Acidic-medium synthesis is a useful way to find new zeolites that move in a fundamentally different direction from sophisticated organic structure-directing agents.

Clothing and textiles are very challenging to recycle due to the fact that they are nearly always a blend of fibres from different types of polymers. There are some promising early indications that new green solvents including Cyrene^TM and TMO as well as some simple ionic liquids can be used to aid recycling of complex fabrics by selective dissolution of one of the component polymers. A viable process for the future valorisation of many waste fabrics should be designed to maximise the creation of valuable product streams while also minimising any waste.

Reactive crystallization plays an essential role in the synthesis of high-quality precursors with a narrow particle size distribution, dense packing, and high sphericity. These features are beneficial in the fabrication of high-specific-capacity and long-cycle-life cathodes for lithium-ion and sodium-ion batteries. However, in industrial production, designing and scaling-up crystallizers involves the use of semi-empirical approaches, making it challenging to satisfactorily meet techno-economic requirements. Furthermore, there is still a lack of in-depth knowledge on the theoretical models and technical calculations of the current co-precipitation process. This review elaborates on critical advances in the theoretical guidelines and process regulation strategies using a reactive crystallizer for the preparation of precursors by co-precipitation. The research progress on the kinetic models of co-precipitation reactive crystallization is presented. In addition, the regulation strategies for the reactive crystallization process of lithium-ion ternary cathodes are described in detail. These include the influence of different reactive crystallizer structures on the precursor's morphology and performance, the intelligent online measurement of efficient reactive crystallizers to ensure favorable conditions of co-precipitation, and preparing the precursor with a high tap density by increasing its solid holdup. A controllable reactive crystallization process is described in terms of the structural design with concentration gradient materials and bulk gradient doping of advantageous elements (such as magnesium ion) in lithium-ion cathodes and the fabrication of sodium-ion cathodes with three typical materials—Prussian blue analogues, transition metal oxides, and polyanionic phosphate compounds being involved.

In this study, we present the development of microtubular solid oxide fuel cells (MT-SOFC) with a two-layer cathode: a composite cathode functional layer (CFL) adjacent to the buffer layer (BL) and a cathode current-collecting layer (CCCL). CFL consists of a mixture of BL material Ce_0.9Sm_0.2O_1.95 (SDC) and perovskite Ba_0.5Sr_0.5Co_0.75Fe_0.2Mo_0.05O_3-δ (BSCFM5), which has a high exchange rate with oxygen. The widely used cathode material La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) with high electrical conductivity was used as the CCCL. A significant increase in the peak power density of the MT-SOFC to 1.2 W/cm² at 850 °C was achieved using the proposed two-layer cathode.

This review article critically compares two widely used types of catalysis, chemo- and biocatalysis, and provides insights on their greenness according to specified parameters. A comparative analysis of the environmental impact of chemo- and biocatalytic oxyfunctionalisation reactions based on published experimental data reveals that both methods produce comparable amounts of waste, with the majority stemming from the solvent used. However, it is emphasised that the synthesis of the catalysts themselves, including biocatalysts, should also be considered when assessing their environmental impact. The review underscores the complexity of assessing the environmental impact of catalytic oxyfunctionalisation reactions. The article also discusses the relationship between solvent properties and the energy demands for chemical transformations and downstream processing, underlining that the choice of solvent can significantly influence the environmental impact of a catalytic process. Additionally, the review highlights the importance of considering the recyclability of reagents and the secondary CO₂ emissions caused by the energy requirements of the reaction when evaluating the environmental impact of a catalytic process. Each chemo- and biocatalysis produce a certain environmental impact, the greenness of either method is dependent on several factors, including the type of waste generated, the recyclability of reagents, and secondary CO₂ emissions. This review therefore recommends using consistent metrics and a comprehensive life cycle assessment approach to evaluate this environmental impact, and highlights the importance of considering the synthesis of the catalysts themselves.

The oxygen reduction reaction (ORR) activity of carbonized ZIF-8 (CZ) and its Fe-doped derivatives, CZ-A (doped with ammonium iron (II) sulphate) and CZ-B (doped with iron (II) acetate), were examined in both acidic (0.5 M H₂SO₄) and basic (0.1 M KOH) electrolytes using a rotating disk electrode setup. These data show that the ORR activity of the Fe-doped catalysts is higher than that of pure CZ, with a higher activity in basic than acidic electrolyte. Extensive materials characterization highlights important differences in the sample crystallinity, morphology, porosity, and chemical composition as a function of the deployed precursor. The performance of the prepared catalysts is also impacted by the Fe precursor selection, highlighting the importance of such synthetic parameters in controlling the density and identify of Fe-Nx active sites. These results demonstrate the potential application of Fe-doped carbonized ZIF-8 catalysts for the ORR in basic electrolyte and offer important knowledge for the future design of non-precious metal fuel cell electrocatalysts.

L-malic acid (L-MA) is an important intermediate in the tricarboxylic acid cycle and a crucial bulk chemical with various applications in the food, pharmaceutical, and chemical industries. With the rapid advancements in metabolic engineering technology and the global commitment toward fostering a green economy and sustainable development, the large-scale production of L-MA is gradually transitioning from conventional petroleum-based approaches to microbial fermentation. This comprehensive review aims to provide a thorough overview of the historical background and recent advancements in the microbial fermentation production of L-MA, encompassing an in-depth introduction to diverse biosynthetic pathways and host strains. Moreover, this review elucidates the challenges encountered in the industrialization of microbial fermentation production of L-MA, offering a summary of potential solutions and prospects for future research directions. The anticipated outcome of this review is to contribute valuable theoretical guidance toward promoting technological innovation in L-MA production.

Owing to excessive carbon dioxide (CO₂) emissions, which cause severe environmental issues, the conversion and utilization of CO₂ have received increasing attention. Owing to its high efficiency and potential for industrial applications, converting CO₂ into high value-added chemicals via thermocatalytic hydrogenation is a highly effective route among electrocatalytic, photocatalytic, and thermocatalytic CO₂ conversion. In the past two decades, our group has developed novel CO₂ hydrogenation technologies to produce chemicals such as aliphatic hydrocarbons, methanol (MeOH), ethanol, and aromatics (especially para-xylene, PX). In this review, we summarize the strategy for CO₂ hydrogenation conversion and the novel rational design of catalysts, including low-temperature MeOH synthesis and capsule catalysts for tandem catalysis. We also discuss the challenges and opportunities of CO₂ hydrogenation, such as CO₂ capture, H₂ prices, and carbon taxes. We hope to inspire new ideas for CO₂ hydrogenation to produce high value-added chemicals through the design of catalysts and the exploration of reaction paths.

Photocatalytic oxidation coupling of amines represents a green and cost-effective method for the synthesis of highly value-added imines under visible light irradiation. However, the catalytic efficiency was severely limited by poor visible light response and easy recombination of photogenerated charge carriers. Herein, we report a g-C₃N₄/α-Bi₂O₃ Z-scheme heterojunction via electrostatic self-assembly of g-C₃N₄ nanosheets and oxygen-vacancy-rich α-Bi₂O₃ microsphere for visible-light driven oxidative coupling of amines to imines in H₂O as green solvent at room temperature. Amines with diverse functional groups were efficiently converted into the corresponding imines in good to excellent yields. Impressively, this photocatalytic protocol is applicable for the challenging hetero-coupling of two structurally different amines to construct complicated asymmetric imines, which is the first report of photocatalytic hetero-coupling of amines to imines to our knowledge. Furthermore, the Z-scheme heterojunction also demonstrated high stability and could be readily separated and reused without obvious decay in activity and selectivity. Comprehensive characterizations and control experiments reveal the construction of Z-scheme heterojunction with intimate interface between g-C₃N₄ and α-Bi₂O₃ greatly boosts the transfer and separation of photogenerated charge carries and enhances the redox capability. Meanwhile, the surface oxygen vacancies in α-Bi₂O₃ also benefits the separation of photogenerated charge carriers and activation of reactants. These jointly contributed to an enhanced photocatalytic performance for oxidative coupling of amines to imines.