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Graphene oxide (GO), as a 2-dimensional material, has shown great promise in the removal of emerging contaminants from water, yet the separation and recycling challenges have limited its practical use. To overcome these challenges, GO was first thermally reduced to form a porous nanostructured hydrogel, which was then functionalized with polydopamine (PDA). The PDA with abundant functional groups, therefore, act as both adsorption and nucleation sites for the in-situ formatio [Detail] ...
Download coverIn the present study, a sustainable pretreatment methodology combining liquid hot water and deep eutectic solvent is proposed for the efficient fractionation of hemicellulose, cellulose, and lignin from sugarcane bagasse, thereby facilitating the comprehensive utilization of both C5 and C6 sugars. The application of this combined pretreatment strategy to sugarcane bagasse led to notable enhancements in enzymatic saccharification and subsequent fermentation. Experiment results demonstrate that liquid hot water-deep eutectic solvent pretreatment yielded 85.05 ± 0.66 g·L–1 of total fermentable sugar (glucose: 60.96 ± 0.21 g·L–1, xylose: 24.09 ± 0.87 g·L–1) through enzymatic saccharification of sugarcane bagasse. Furthermore, fermentation of the pretreated sugarcane bagasse hydrolysate yielded 34.33 ± 3.15 g·L–1 of bioethanol. These findings confirm the effectiveness of liquid hot water-deep eutectic solvent pretreatment in separating lignocellulosic components, thus presenting a sustainable and promising pretreatment method for maximizing the valuable utilization of biomass resources.
Regulation of aluminum distribution in zeolite framework is an effective method for improving its catalytic performance for propane aromatization. Herein, we found that recrystallization and post-realuminization of ZSM-5 cannot only create hollow structures to enhance the diffusion ability, but also adjust the content and position of paired aluminum species in its framework. Various characterizations results confirmed that increase of paired aluminum content and inducement of more aluminum atoms sited in the intersection cavity are beneficial to the formation of aromatic products in propane aromatization. As a result, the hollow-structured ZSM-5 zeolite with more paired aluminum (H-200-hollow) showed higher propane conversion and aromatics selectivity than other samples at the same conditions. The catalytic performance of H-200-hollow can be further improved by ion-exchanging with a small amount of Ga(III) species. The propane conversion and aromatics selectivity of Ga-200-hollow reached as high as 95% and 70%, respectively, at 540 °C and 1 atm.
Unraveling the structure-activity relationship and improving the catalytic performance is paramount in propane dehydro-aromatization reactions. Herein, a tandem catalyst with high propane dehydro-aromatization reaction performance was prepared via coupling the PtFe@S-1 with Zn/ZSM-5 zeolites (PtFe@S-1&1.0Zn/ZSM-5), which exhibits high dehydrogenation activity, aromatics selectivity (~60% at ~78% propane conversion), and stability. The addition of zinc inhibits the cleavage of C6= intermediates on ZSM-5 and promotes the aromatization pathway by weakening zeolite acid strength, significantly improving the selectivity to aromatics. This understanding of the structure-activity relationship in propane dehydro-aromatization reaction helps develop future high-performance catalysts.
Epoxidation of propylene to propylene oxide (PO) with hydrogen peroxide (HPPO) is an environmentally friendly and cost-efficient process in which titanosilicates are used as catalysts. Ti-MWW is a potential industrial catalyst for this process, which involves the addition of HPPO to PO. The silanol groups generated during secondary crystallization unavoidably result in ring-opening of PO and inefficient decomposition of HPPO, which diminish the PO selectivity and the lifespan of Ti-MWW. To address this issue, we conducted post-treatment modifications of the structured Bf-Ti-MWW catalyst with potassium fluoride aqueous solutions. By quenching the silanol groups with potassium fluoride and implanting electron-withdrawing fluoride groups into the Ti-MWW framework, both the catalytic activity and HPPO utilization efficiency were increased. Moreover, the ring opening reaction of PO was prohibited. In a continuous fixed-bed liquid-phase propylene epoxidation reaction, the KF-treated structured Ti-MWW catalyst displayed an exceptionally long lifespan of 2700 h, with a PO yield of 590 g·kg−1·h−1.
Graphene oxide is a promising adsorption material. However, it has been difficult to recycle and separate graphene oxide in the solution. To alleviate this problem, graphene oxide was thermally reduced to produce porous hydrogel which was then functionalized with polydopamine. The functional groups act as not only adsorption sites but also nucleation sites for in situ crystallization of cobalt-doped zeolitic-imidazolate-framework-8 nano-adsorbents. The effects of cobalt-doping contents on the physicochemical and adsorption properties of the resulting aerogel were also evaluated by varying the cobalt concentration. For instance, the reduced graphene oxide-polydopamine/50cobalt-zeolitic-imidazolate-framework-8 aerogel exhibited a high surface area of 900 m2·g–1 and maintained the structure in water after ten days. The as-synthesized aerogels showed an ultrahigh adsorption capacity of 1217 ± 24.35 mg·g–1 with a removal efficiency of > 99% of lead, as well as excellent adsorption performance toward other heavy metals, such as copper and cadmium with adsorption capacity of 1163 ± 34.91 and 1059 ± 31.77 mg·g–1, respectively. More importantly, the lead adsorption stabilized at 1023 ± 20.5 mg·g–1 with a removal efficiency of > 80% after seven cycles, indicating their potential in heavy metal removal from industrial wastewater.
The oxidative condensation between renewable furfural and fatty alcohols is a crucial avenue for producing high-quality liquid fuels and valuable furan derivatives. The selectivity control in this reaction process remains a significant challenge. Herein, we report the strategy of confining well dispersed gold species within ZSM-5 structure to construct highly active Au@ZSM-5 zeolite catalysts for the oxidative condensation of furfural. Characterization results and spectroscopy analyses demonstrate the efficient encapsulation of isolated and cationic Au clusters in zeolite structure. Au@ZSM-5(K) catalyst shows remarkable performance with 69.7% furfural conversion and 90.2% furan-2-acrolein selectivity as well as good recycle stability. It is revealed that the microstructure of ZSM-5 zeolite can significantly promote oxidative condensation activity through confinement effects. This work presents an explicit example of constructing zeolite encaged noble metal catalysts toward targeted chemical transformations.
With the rapid iteration and update of wearable flexible devices, high-energy-density flexible lithium-ion batteries are rapidly thriving. Flexibility, energy density, and safety are all important indicators for flexible lithium-ion batteries, which can be determined jointly by material selection and structural design. Here, recent progress on high-energy-density electrode materials and flexible structure designs are discussed. Commercialized electrode materials and the next-generation high-energy-density electrode materials are analyzed in detail. The electrolytes with high safety and excellent flexibility are classified and discussed. The strategies to increase the mass loading of active materials on the electrodes by designing the current collector and electrode structure are discussed with keys of representative works. And the novel configuration structures to enhance the flexibility of batteries are displayed. In the end, it is pointed out that it is necessary to quantify the comprehensive performance of flexible lithium-ion batteries and simultaneously enhance the energy density, flexibility, and safety of batteries for the development of the next-generation high-energy-density flexible lithium-ion batteries.
Higher alcohol synthesis directly from syngas is highly desirable as one of the efficient non-petroleum energy conversion routes. Co0–CoO catalysts showed great potential for this reaction, but the alcohol selectivity still needs to be improved and the crystal structure effect of CoO on catalytic behaviors lacks investigation. Here, a series of tetrahedrally coordinated CoO polymorphs were prepared by a thermal decomposition method, which consisted of wurtzite CoO and zinc blende CoO with varied contents. After diluting with SiO2, the catalyst showed excellent performance for higher alcohol synthesis with ROH selectivity of 45.8% and higher alcohol distribution of 84.1 wt % under the CO conversion of 38.0%. With increasing the content of wurtzite CoO, the Co0/Co2+ ratio gradually increased in the spent catalysts, while the proportion of highly active hexagonal close packed cobalt in Co0 decreased, leading to first decreased then increased CO conversion. Moreover, the higher content of zinc blende CoO in fresh catalyst facilitated the retention of more Co2+ sites in spent catalysts, promoting the ROH selectivity but slightly decreasing the distribution of higher alcohols. The catalyst with 40% wurtzite CoO obtained the optimal performance with a space time yield toward higher alcohols of 7.9 mmol·gcat–1·h–1.
A facile synthesis of hierarchical ZSM-5 with the three-dimensionally ordered mesoporosity (3DOm ZSM-5) was achieved by solid conversion (SC) of SiO2 colloidal crystals to high-crystalline ZSM-5. The products of 3DZ5_S/C and 3DZ5_S, which were severally transformed from the carbon-padded SiO2 colloidal crystals and the initial SiO2 colloidal crystals, exhibited not only a similar ordered structure and acidity but also higher crystallinity and more balanced meso-/micropore combination in comparison with 3DZ5_C obtained by the conventional confined space crystallization approach. All three synthesized 3DZ5 catalysts showed improved methanol-to-propylene performance than the commercially microporous ZSM-5 (CZ5), embodied in five times longer lifetime, higher propylene selectivity and Spropylene/Sethylene ratio (P/E), and superior coke toleration with lower formation rate of coke (Rcoke). Moreover, the 3DZ5_S catalyst in situ converted from SiO2 colloidal crystals presented the highest selectivities of propylene (42.51%) and light olefins (74.6%) among all three 3DZ5 catalysts. The high efficiency in synthesis and in situ utilization of SiO2 colloidal crystals demonstrate the proposed SC strategy to be more efficiently and eco-friendly for the high-yield production of not only 3DOm ZSM-5 but also other types of hierarchical zeolites.
Reactant gas and liquid water transport phenomena in the flow channels are complex and critical to the performance and durability of polymer electrolyte membrane fuel cells. The polymer membrane needs water at an optimum level for proton conductivity. Water management involves the prevention of dehydration, waterlogging, and the cell’s subsequent performance decline and degradation. This process requires the study and understanding of internal two-phase flows. Different experimental visualization techniques are used to study two-phase flows in polymer electrolyte membrane fuel cells. However, the experiments have limitations in in situ measurements; they are also expensive and time exhaustive. In contrast, numerical modeling is cheaper and faster, providing insights into the complex multiscale processes occurring across the components of the polymer electrolyte membrane fuel cells.
This paper introduces the recent design of flow channels. It reviews the numerical modeling techniques adopted for the transport phenomena therein: the two-fluid, multiphase mixture, volume of fluid, lattice Boltzmann, and pressure drop models. Furthermore, this work describes, compares, and analyses the models’ approaches and reviews the representative results of some selected aspects. Finally, the paper summarizes the modeling perspectives, emphasizing future directions with some recommendations.
