Green Chemical Engineering最新文献

The electrochemical reduction of CO₂ is an extremely potential technique to achieve the goal of carbon neutrality, but the development of electrocatalysts with high activity, excellent product selectivity, and long-term durability remains a great challenge. Herein, the role of metal-supports interaction (MSI) between different active sites (including single and bimetallic atom sites consisting of Cu and Ni atoms) and carbon-based supports (including C₂N, C₃N₄, N-coordination graphene, and graphdiyne) on catalytic activity, product selectivity, and thermodynamic stability towards CO₂ reduction reaction (CRR) is systematically investigated by first principles calculations. Our results show that MSI is mainly related to the charge transfer behavior from metal sites to supports, and different MSI leads to diverse magnetic moments and d-band centers. Subsequently, the adsorption and catalytic performance can be efficiently improved by tuning MSI. Notably, the bimetallic atom supported graphdiyne not only exhibits a better catalytic activity, higher product selectivity, and higher thermodynamic stability, but also effectively inhibits the hydrogen evolution reaction. This finding provides a new research idea and optimization strategy for the rational design of high-efficiency CRR catalysts.

Benzene (BEN) and cyclohexane (CYH), which have very close boiling points and a binary azeotrope, are the most difficult binary components in the separation of aromatic and non-aromatic hydrocarbons. This study further explored the separation mechanism and industrial application prospects of BEN ​+ ​CYH mixtures separated by a dicationic ionic liquid (DIL) [C₅(MIM)₂][NTf₂]₂ based on experimental research. The calculation results of the Conductor-like Screening model Segment Activity Coefficient (COSMO-SAC) model show that selectivity and solvent capacity of the DIL are significantly improved. The effects of different anions and cations on the microstructure distribution and diffusion behavior of BEN ​+ ​CYH system were investigated by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. The results indicate that the anion [NTf₂]⁻ has low polarity, uniform charge distribution, and a dual role of hydrogen bonding and π-π bonding, and the cation [C₅(MIM)₂]²⁺ has stronger interaction with BEN and higher selectivity than conventional cations. The liquid-liquid extraction and extractive distillation (LLE-ED) process using an optimized 65 mol/mol DIL ​+ ​35 mol/mol H₂O mixed solution as the extractant was proposed, which solved the problem of low product purity in the LLE process and high energy consumption in the ED process. Under the best operating conditions, the purity of CYH product was 99.9%, the purity of BEN product was 99.6%, the recovery rate of BEN reached 99.9%, and the recovery rate of DIL reached 99.9%. The heat-integrated LLE-ED process reduced total annual cost by 21.6%, and reduced CO₂ emissions by 48.0%, which has broad industrial application prospects.

Cooked rice and the vegetables like lettuce are common kitchen waste, which are carbonaceous materials and have the potential as feedstock for the production of activated carbon. Cooking is similar to hydrothermal treatment (HTC), which might impact the subsequent activation of kitchen waste. In this study, the HTC of lettuce, rice, or their mixture and the activation of the resulting hydrochars were conducted. The results indicated that cross-polymerization between the N-containing organics from lettuce and the sugar derivatives from rice took place in their co-HTC, which significantly increased the hydrochar yield. Activation of the hydrochar from the co-HTC generated the AC with a yield of 2 times that from direct activation of mixed lettuce/rice. However, the co-HTC facilitated aromatization, reducing reactivity with K₂C₂O₄ in activation and producing the AC with main micropores and low specific surface area. Activation of the hydrochar from HTC of rice followed the above trend, while that from lettuce was the opposite. The organics in lettuce were thermally unstable and could not undergo sufficient aromatization. The activation of hydrochar from HTC of lettuce thus generated the AC with the lowest yield, but the highest specific surface area (1684.9 m²/g), abundant mesopores, and superior capability for adsorption of tetracycline. However, the environmental impacts and energy consumption for the production of AC from the hydrochar of lettuce were higher than that from hydrochar of co-HTC.

While the industry has produced sugar-derived ethanol from the conventional method of fermentation for hundreds of years, other effective routes involving the direct transformation of carbohydrates still remain extremely rare. Very recently, an innovative chemo-catalytic method driven by the aqueous-phase catalysis was created for the synthesis of cellulosic ethanol, making a great breakthrough in the common ways as it can theoretically utilize all of the carbon atoms in sugars with faster kinetics; up to now, results from the relevant studies have been accumulated to a certain extent, but the periodic conclusions in this field are unfortunately absent. For this reason, this work tries to offer an overview of the cellulosic ethanol produced by chemo-catalytic routes, highlighting the present knowledge in relation to the technical efficiency, catalytic mechanisms as well as practical applications. At first, the advanced progress on the increasing efficiency from a varied type of catalytic systems are extensively discussed, which involves the specific functions of hybrid components from different strategies; meanwhile, the general influences of processing conditions, such as the hydrothermal severity and aqueous environments, are also identified. Subsequently, possible mechanisms behind the chemo-catalytic processes are widely elaborated by analyzing a number of experimental cases associated with the reaction network and its kinetic models. After that, the actual effects of this technique on the real biomass are collected to identify the positive/negative interactions between multiple components, together with the potential solutions on the semi-continuous processes of pilot scale application. The techno-economic analysis (TEA) is also calculated and compared with other similar methods, such as fermentation and gasification. Finally, several proposals aimed at upgrading the whole chain of chemo-catalytic processes are clearly provided, which may function as a guideline for future studies on the production of bio-ethanol from lignocellulosic materials.

Zinc and cadmium pollutants cause a significant environmental effect that cannot be ignored. Due to their considerable amount in an aqueous environment, industries are seeking suitable adsorbents that are environmentally friendly and inexpensive for removing metals from wastewater before disposing of them in surface waters. This research employed original MXene (MX) and chitosan-modified MXene (CSMX) to extract zinc (Zn(II)) and cadmium (Cd(II)) metal ions from water-based solutions. The composite material produced was analyzed using techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). The effects of contact duration, pH of the solution, and initial concentration of metal ions on the adsorption process of Zn(II) and Cd(II) onto both MX and CSMX composites were investigated. MX and prepared CSMX composite presented a high adsorption capacity for both studied heavy metals, which were 91.55 and 73.82 mg/g for Zn(II) and Cd(II) onto MX, 106.84 and 93.07 mg/g for Cd(II) and Zn(II) onto CSMX composite, respectively. Furthermore, the maximum competitive adsorption capacities for Zn(II) onto MX and CSMX composites are 77.29 and 93.47 mg/g, and for are Cd(II) 60.30 and 79.66 mg/g, respectively. Hence, the removal capacities for both single and competitive metal ions were superior to CSMX composite. However, the adsorption capacities after five successive regeneration sequences were only dropped by 13.2% for Zn(II) and 17.4% for Cd(II) onto the CSMX composite compared to the first cycle. These results confirm that both metals could be efficiently terminated from wastewater, which makes the prepared CSMX composite a favorable candidate adsorbent in practical applications.

Metal-organic frameworks (MOFs) are favored in the fields of adsorption, separation, catalysis, electrochemistry, and magnetism due to their advantages of large specific surface area, high porosity, controllable pore size adjustment, and dispersion of metal active sites. The application of MOFs involves multiple fields, which requires that MOFs have good water stability, as gaseous and liquid water inevitably exist in industrial processes. In this paper, the research status of the stability of MOFs in aqueous solutions was reviewed in recent years, including the design and synthesis, the influencing factors, and the applications of MOFs in water stability.

The development of ultrafine particles provided a new way to solve problems in the fields of energy, environment, and medicine, and had become one of the most promising technologies. Therefore, the application of ultrafine particles required the development of cleaner, greener, and more efficient preparation methods. The new freeze-dissolving technology has been applied in manufacturing of KHCO₃ ultrafine particles, with an aqueous solution of 0.02–0.1 g KHCO₃/g water. Frozen ice particles were formed after dripping the solution into liquid nitrogen. The antisolvent ethanol was used to dissolve the ice spherical template at a temperature below 273.15 K, and the pre-formed KHCO₃ ultrafine particles inside the ice template remained in the ethanol aqueous solution. The ice particles were put into the freeze dryer to isolate the ultrafine KHCO₃ particles. Compared with the particles produced with traditional freeze-drying technology, the ultrafine powder/particles produced by the freeze-dissolving technology were smaller with narrower size distribution. The freeze-dissolving technology has demonstrated a much more sustainable and efficient manufacturing process than the traditional freeze-drying process. In addition, the influence of the concentrations of KHCO₃ and the sizes of ice particles were investigated with the discussions of mechanisms.

Dendritic mesoporous silica nanoparticles (DMSNs) are a new class of solid porous materials used for enzyme immobilization support due to their intrinsic characteristics, including their unique open central–radial structures with large pore channels and their excellent biocompatibility. In this review, we review the recent progress in research on enzyme immobilization using DMSNs with different structures, namely, flower-like DMSNs and tree-branch-like DMSNs. Three DMSN synthesis methods are briefly compared, and the distinct characteristics of the two DMSN types and their effects on the catalytic performance of immobilized enzymes are comprehensively discussed. Possible directions for future research on enzyme immobilization using DMSNs are also proposed.