Frontiers of Chemical Science and Engineering最新文献

The photocatalytic reduction of CO₂ into formic acid is a feasible approach to alleviate the effects of global climate change and achieve chemical energy storage. It is important to design highly active photocatalysts to improve the selectivity and yield of formic acid. In this study, TiO₂-based catalysts were prepared and loaded with Pd nanoparticles via an impregnation process. The Pd/H-TiO₂ catalyst demonstrated superior CO₂ reduction activity and a high formic acid production rate of 14.14 mmol_cat·g⁻¹·h⁻¹. The excellent catalytic performance observed in the presence of a Pd/H-TiO₂ catalyst is ascribed to the synergy between O_v and Pd. The presence of O_v led to increase in CO₂ adsorption while Pd loading enhanced the photogenerated electron-hole pair separation. Electron transfer from H-TiO₂ to Pd also contributed to CO₂ activation.

A novel carboxylated lactose/sodium lignosulfonate/polyacrylic acid hydrogel composites with self-reduction capacity was successfully synthesized by self-assembly method. The hydrogel with well-developed porous structure provided abundant anchoring points and reduction capacity for transforming Ag⁺ into silver nanoparticles. Silver nanoparticles dispersed among the network of hydrogel and the composites exhibited catalytic capacity. The catalytic performance was evaluated via degradation of p-nitrophenol, rhodamine B, methyl orange and methylene blue, which were catalyzed with corresponding reaction rate constants of 0.04338, 0.07499, 0.04891, and 0.00628 s^–1, respectively. In addition, the catalyst exhibited stable performance under fixed-bed condition and the corresponding conversion rate still maintained more than 80% after 540 min. Moreover, the catalytic performance still maintained effective in tap water and simulated seawater. The catalytic efficiency still remained 99.7% with no significant decrease after 8 cycles.

An onboard facility shows promise in efficiently converting floating plastics into valuable products, such as methanol, negating the need for regional transport and land-based treatment. Gasification presents an effective means of processing plastics, requiring their transformation into gasification-compatible feedstock, such as hydrochar. This study explores hydrochar composition modeling, utilizing advanced algorithms and rigorous analyses to unravel the intricacies of elemental composition ratios, identify influential factors, and optimize hydrochar production processes. The investigation begins with decision tree modeling, which successfully captures relationships but encounters overfitting challenges. Nevertheless, the decision tree vote analysis, particularly for the H/C ratio, yielding an impressive R² of 0.9376. Moreover, the research delves into the economic feasibility of the marine plastics-to-methanol process. Varying payback periods, driven by fluctuating methanol prices observed over a decade (ranging from 3.3 to 7 yr for hydrochar production plants), are revealed. Onboard factories emerge as resilient solutions, capitalizing on marine natural gas resources while striving for near-net-zero emissions. This comprehensive study advances our understanding of hydrochar composition and offers insights into the economic potential of environmentally sustainable marine plastics-to-methanol processes.

The reliance on fossil fuels intensifies CO₂ emissions, worsening political and environmental challenges. CO₂ capture and conversion present a promising solution, influenced by industrialization and urbanization. In recent times, catalytic conversion of CO₂ into fuels and chemical precursors, particularly methane, are gaining traction for establishing a sustainable, carbon-neutral economy due to methane’s advantages in renewable energy applications. Though homogeneous and heterogeneous catalysts are available for the conversion of CO₂ to methane, the efficiency is found to be higher in heterogeneous catalysts. Therefore, this review focuses only on the heterogeneous catalysts. In this context, the efficient heterogeneous catalysts with optimum utility are yet to be obtained. Therefore, the quest for suitable catalyst for the catalytic conversion of CO₂ to CH₄ is still continuing and designing efficient catalysts requires assessing their synthetic feasibility, often achieved through computational methods like density functional theory simulations, providing insights into reaction mechanisms, rate-limiting steps, catalytic cycle, activation of C=O bonds and enhancing understanding while lowering costs. In this context, this review examines the conversion of CO₂ to CH₄ using seven distinct types of catalysts, including single and double atom catalysts, metal organic frameworks, metalloporphyrins, graphdiyne and graphitic carbon nitrite and alloys with some case studies. The main focus of this review is to offer a detailed and extensive examination of diverse catalyst design approaches and their utilization in CH₄ production, with a specific emphasis on computational aspects. It explores the array of design methodologies used to identify reaction pathways and investigates the critical role of computational tools in their refinement and enhancement. We believe this review will help budding researchers to explore the possibilities of designing catalysts for the CO₂ to CH₄ conversion from computational framework.

Framework materials such as zeolites and mesoporous silicas are commonly used for many applications, especially catalysis and separation. Here zeolite-mesoporous silica composite catalysts (employing zeolite Y, ZSM-5, KIT-6, SBA-15 and MCM-41 mesoporous silica) were prepared (with different weight percent of zeolite Y and ZSM-5) and assessed for catalytic cracking (using n-heptane, as the model compound at 550 °C) with the aim to improve the selectivity/yield of light olefins of ethylene and propylene from n-heptane. Physicochemical properties of the parent zeolites and the prepared composites were characterized comprehensively using several techniques including X-ray diffraction, nitrogen physisorption, scanning electron microscopy, fourier transform infrared spectroscopy, pulsed-field gradient nuclear magnetic resonance and thermogravimetric analysis. Catalytic cracking results showed that the ZY/ZSM-5/KIT-6 composite (20:20:60 wt %) achieved a high n-heptane conversion of 85% with approximately 6% selectivity to ethylene/propylene. In contrast, the ZY/ZSM-5/SBA-15 composite achieved a higher conversion of 95% and an ethylene/propylene ratio of 8%, indicating a more efficient process in terms of both conversion and selectivity. Magnetic resonance relaxation analysis of the ZY/ZSM-5/KIT-6 (20:20:60) catalyst confirmed a micro-mesoporous environment that influences n-heptane diffusion and mass transfer. As zeolite Y and ZSM-5 have micropores, n-heptane can move and undergo hydrogen transfer reactions, whereas KIT-6 has mesopores that facilitate n-heptane’s accessibility to the active sites of zeolite Y and ZSM-5.

Herein, we introduced a nitrogen-alkali lignin-doped phenolic resin (N@AL_nPR) to produce palladium nanoparticles through an in situ reduction of palladium in an aqueous phase, without the need for additional reagents or a reducing atmosphere. The phenolic resin nanospheres and the resulting palladium nanoparticles were extensively characterized. Alkali lignin created a highly conducive environment for nitrogen incorporation, dispersion, reduction, and stabilization of palladium, leading to a distinct catalytic performance of palladium nanoparticles in vanillin hydrodeoxygenation. Under specific conditions of 1 mmol of vanillin, 40 mg of catalyst, 1 MPa H₂, 90 °C, and 3 h, the optimized Pd/N@AL₃₀PR catalyst exhibited a nearly complete conversion of vanillin, 98.9% selectivity toward p-creosol, and good stability for multiple reuses. Consequently, an environmentally friendly lignin-based catalyst was developed and used for the efficient hydrodeoxygenation conversion of lignin-based platform compounds.

The Fe-Mn bimetallic catalyst is a potential candidate for the conversion of CO₂ into value-added chemicals. The interaction between the two metals plays a significant role in determining the catalytic performance, however which remains controversial. In this study, we aim to investigate the impact of tuning the proximity of Fe-Mn bimetallic catalysts with similar nanoparticle size. And its effect on the physicochemical properties of the catalysts and corresponding performance were investigated. It was found that closer Fe-Mn proximity resulted in enhanced CO₂ hydrogenation activity and inhibited CH₄ formation. The physiochemical properties of prepared catalysts were characterized using X-ray diffraction, H₂ temperature programmed reduction, and X-ray photoelectron spectroscopy, revealing that a closer Fe-Mn distance promoted electron transfer from Mn to Fe, thereby facilitating Fe carburization. The adsorption behavior of CO₂ and the identification of reaction intermediates were analyzed using CO₂-temperature programed desorption and in situ Fourier transform infrared spectroscopy, confirming the intimate Fe-Mn sites contributed to CO₂ adsorption and the formation of HCOO* species, ultimately leading to increased CO₂ conversion and hydrocarbon production. The discovery of a synergistic effect at the intimate Fe-Mn sites in this study provides valuable insights into the relationship between active sites and promoters.

With the advantages of low raw material cost and 100% atom utilization, the synthesis of high value-added chemical product cyclic carbonates by the cycloaddition of CO₂ to epoxides has become one of the most prospective approaches to achieve the industrial utilization of CO₂. In the reported catalytic systems, the complexity of the catalyst synthesis process, high cost, separation difficulties, and low CO₂ capture limit the catalytic efficiency and its large-scale application. In this paper, Ag nanoparticles loaded on polyethyleneimine (PEI)-modified UiO-66-NH₂ (Ag/PEI@UiO-66-NH₂) are successfully synthesized by in situ immersion reduction. The Ag nanoparticles and the amino groups on the surfaces of PEI@UiO-66-NH₂ contribute to the adsorption of CO₂ and polarization of C–O bonds in epoxides, thereby boosting the conversion capability for the CO₂ cycloaddition reaction. At the amount of propylene oxide of 0.25 mol and the catalyst dosage of 1% of the substrate, the yield and selectivity of propylene carbonate are up to 99%. In addition, the stability and recyclability of Ag/PEI@UiO-66-NH₂ catalyst are attained. The Ag/PEI@UiO-66-NH₂ catalyst also demonstrates a wide range of activity and distinctive selectivity toward cyclo-carbonates in the cycloaddition of CO₂ to epoxides. This work provides a guide to designing a highly efficient catalyst for in situ capture and high-value utilization of CO₂ in industrial applications.

Separating monomeric cycloalkanes from naphtha obtained from direct coal liquefaction not only facilitates the valuable utilization of naphtha but also holds potential for addressing China’s domestic chemical feedstock market demand for these compounds. In extractive distillation processes of naphtha, relative volatility serves as a crucial parameter for extractant selection. However, determining relative volatility through conventional vapor-liquid equilibrium experiments for extractant selection proves challenging due to the complexity of naphtha’s compound composition. To address this challenge, a prediction model for the relative volatility of n-heptane/methylcyclohexane in various extractants has been developed using machine-learning quantitative structure-property relationship methods. The model enables rapid and cost-effective extractant selection. The statistical analysis of the model revealed favorable performance indicators, including a coefficient of determination of 0.88, cross-validation coefficient of 0.94, and root mean square error of 0.02. Factors such as α, E_HOMO, ρ, and logP_oct/water collectively influence relative volatility. Analysis of standardized coefficients in the multivariate linear regression equation identified density as the primary factor affecting the relative volatility of n-heptane/methylcyclohexane in the different extractants. Extractants with higher densities, devoid of branched chains, exhibited increased relative volatility compared to their counterparts with branched chains. Subsequently, the process of separating cycloalkane monomers from direct coal liquefaction products via extractive distillation was optimized using Aspen Plus software, achieving purities exceeding 0.99 and yields exceeding 0.90 for cyclohexane and methylcyclohexane monomers. Economic, energy consumption, and environmental assessments were conducted. Salicylic acid emerged as the most suitable extractant for purifying cycloalkanes in direct coal liquefaction naphtha due to its superior separation effectiveness, cost efficiency, and environmental benefits. The tower parameters of the simulated separation unit provide valuable insights for the design of actual industrial equipment.

In this study, the combustion characteristics and kinetics of cotton straw (CS) particles mixed with polyethylene (PE) film and coal gangue (CG) were investigated. The co-combustion characteristics of CS mixed with PE and CG at different heating rates were revealed by the thermogravimetric method and differential thermogravimetric method. The ignition temperature, burnout temperature, and maximum weight loss rate were measured, and the comprehensive combustion and flammability indexes were calculated. The results showed that the composite combustion characteristic index and flammability index increased with the increase in heating rate. The addition of PE and CG additives could effectively extend the combustion time. The Coats-Redfern (C-R) reaction model and N-order reaction model were used to evaluate the kinetic parameters of the blends. The results showed that 12.5% PE + 12.5% CG particles had the lowest activation energy (Ea = 103.73 kJ·mol⁻¹) at the volatile combustion stage. The dynamics conform to the third-order dynamics model. In addition, the applicability of C-R model, Flynn-Wall-Ozawa (FWO) model, and Starink model in the calculation of activation energy was explored, and it was found that the FWO model is not suitable for the calculation of activation energy of biomass pellet combustion kinetics. This study provides a new method for the development and utilization of mixed fuel particles of cotton stalk and solid waste and expands the application prospect of biomass.