燃料化学学报最新文献

Chemical-looping oxidative coupling of methane (CL-OCM) is a promising methodology for ethylene production from methane. This article utilizes molecular dynamics (MD) simulation to assess the performance of eight metal oxide catalytic oxygen carriers in CL-OCM reactions. It also investigates the impact of reaction time and particle size on the efficiency of the most effective Mn₂O₃ COC. The results indicate that extending the reaction time appropriately enhances C₂H₄ selectivity and a C/O ratio of 1 is found to be the optimal size for Mn₂O₃-based CL-OCM. Furthermore, surface reactions and lattice oxygen transfer are analyzed by MD simulation in Mn₂O₃-based CL-OCM, providing deeply insights into the reaction mechanism. The findings reveal that the gas-phase dimerization of${\text{CH}}_{\text{3}}^{\text{*}}$ to form C₂H₆ serves as the primary carbon coupling pathway in CL-OCM. In addition, there are two other carbon coupling pathways, both initiated by${\text{CH}}_{\text{2}}^{\text{*}}$. Methanol formation through surface combination of${\text{CH}}_{\text{3}}^{\text{*}}$ and OH* represents an initial step in CL-OCM side reactions. Therefore, inhibiting methanol formation is crucial for enhancing C₂ selectivity in CL-OCM. There exists a transformation of lattice oxygen and surface lattice oxygen plays a key role in methane activation. The quantity of lattice oxygen and difference in bulk lattice oxygen migration resistance are major factors influencing CH₄ conversion and C₂ selectivity. This study provides a new way to reaction mechanism exploration related to CL-OCM catalytic oxygen carriers.

The main components of power plant flue gas are N₂, CO₂ and part O₂. Injecting power plant flue gas into mine goaf can achieve CO₂ storage and replace nitrogen injection to prevent spontaneous combustion of left coal. However, O₂ in flue gas is one of the factors causing spontaneous combustion of left coal. Therefore, it is urgent to develop an economical and effective catalyst to remove O₂ from power plant flue gas. In this study, four types of copper-based catalysts were prepared using a controllable modulating support and loading capacity through co-precipitation method. Additionally, a series of CuO/CeO₂ catalysts were prepared. The catalysts were characterized using BET, XRD, ICP, TEM, H₂-TPR and XPS to establish a structure-activity relationship of catalyst. The results showed that the addition of CeO₂ enhanced the dispersion of CuO, increased the oxygen vacancy in the catalyst, and improved the activity and reduction-oxidation performance of the catalyst. Moreover, the synergistic effect of Cu-Ce interface structure promoted the redox process, showing good activity and cycle stability. Among the catalysts, the 30CuO/CeO₂ sample showed the best catalytic deoxidation performance owing to its smallest CuO particle size, highest dispersion and oxygen vacancy concentration. The results of this study provide a reference for the development of low cost, recyclable, high activity and stability deoxidation catalysts.

Catalytic decomposition of NO by Cu-ZSM-5 has potential application. In order to reveal the mechanism of the process, the adsorption of NO over short-range Cu⁺ pairs in Cu-ZSM-5 was simulated based on density functional theory. The reaction pathways of NO decomposition assisted by the by-products N₂O and NO₂ were also proposed. The results showed that the double nuclear copper-oxygen species was an important active centre. During the reaction, the highest activation energy (171.39 kJ/mol) was required for the decomposition of the by-product NO₂ on the binuclear copper-oxygen species. While that for the decomposition of N₂O was 86.92 kJ/mol, suggesting that the decomposition of NO₂ was more difficult. The desorption energy of N₂ and O₂ were 28.43 and 100.78 kJ/mol, respectively. The rate determining step was O₂ desorption. NO acted both as a reactant and a key reductant for the redox cycle of the active centre of Cu-ZSM-5 during the process.

A series of small crystal Y-xNi zeolites with different amounts of Ni doping were synthesized by in-situ introducing the Ni precursors during the synthesis, through which the active Ni metal was incorporated into the framework of the Y zeolites. With the mechanical mixture of Y-xNi zeolites and amorphous silica-alumina (ASA) as the support, a series of Cat-xNi catalysts were prepared through loading the Ni and W components by incipient wet impregnation and the catalytic performance of Cat-xNi in the hydrocracking of n-hexadecane was then investigated. In addition, the effect of Ni doping on the physicochemical properties of Y zeolite and Cat-xNi catalysts was elucidated with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂-adsorption desorption, NH₃ temperature programmed desorption (NH₃-TPD), H₂ temperature programmed reduction (H₂-TPR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and so on. The results indicate that Ni can replace Al to enter the framework of the Y zeolites. The incorporation of appropriate amount of Ni into the Y zeolites can increase their relative crystallinity and the number of Br⊘nsted and Lewis acid sites; however, excessive Ni incorporation is detrimental to the crystallization of Y zeolite and excessive non-framework Ni species will cover the surface Br⊘nsted acid sites. Moreover, Ni doping can weaken the metal-support interaction, increase the sulfation extent of the active metal and the stacking number and dispersion of the active NiWS phase, and then improve the matching between the metal and acid sites on the Cat-xNi catalysts. As a results, in comparison with the counterpart Cat-0Ni catalyst, the Cat-xNi catalysts display more Br⊘nsted acid sites and active NiWS sites as well as improved the synergy between the metal sites and acid sites, which can enhance the conversion of n-hexadecane whereas inhibit the over-cracking, and then booster the yield of the middle distillate products (C₈–C₁₂). In particular, for the n-hexadecane hydrocracking at 360 °C, the Cat-0.2Ni catalyst exhibits a C₈–C₁₂ product yield of 65.4%, with a much higher n-C₁₆ conversion than the Cat-0Ni counterpart. All these suggest that the pre-impregnation of active metal Ni on the Y zeolites can effectively regulate the balance between the hydrogenation and cracking performance and improve the catalytic activity and the yield of middle distillate products in the hydrocracking of paraffins.

Light olefins are of great importance as chemical raw materials, and ethylene is a crucial symbol to evaluate the development level of petrochemical industry. Catalytic hydrogenation of CO₂ to light olefins is one of the most vital approaches to utilize CO₂ with high added valued. InZr/SAPO-34 composite catalyst shows prominent potential in research and application because of their high light olefins selectivity and high stability in CO₂ hydrogenation. In this study, the effects of different preparation methods of InZr/SAPO-34 composite catalyst for CO₂ hydrogenation to light olefins were studied in depth. The catalyst prepared by co-precipitation method showed the highest catalytic activity, and the catalyst prepared by sol-gel-precipitation method showed the highest light olefins selectivity. The structure-activity relationship of InZr/SAPO-34 catalysts were revealed by various characterization methods.

In this study, a composite photocatalyst BiOCl@CNC was prepared by simple stirring with BiOCl at room temperature using nanocellulose (CNC) as a carrier. Comprehensive characterizations (XRD, FT-IR, SEM, TEM, XPS) reveal that the abundant hydroxyl groups in CNC can form strong hydrogen bonds with BiOCl, leading to the creation of numerous oxygen vacancies in the material and thereby significantly enhancing its visible light-driven photocatalytic performance. The performance of the BiOCl@CNC was evaluated using the C-N coupling reaction of benzylamine as the target reaction under visible light, and the underlying mechanism was investigated. The results show that the optimal reaction process is that 1.0 mmol of benzylamine and 20 mg of BiOCl@CNC are added to CH₃CN under an oxygen atmosphere to react for 20 h using a 30 W white LED lamp as the light source. In the substrate expansion experiments, the BiOCl@CNC exhibits remarkable adaptability and exceptional stability towards reactants with diverse substituents. The free radical capture experiments demonstrate that the electrons can effectively generate superoxide radicals in the presence of oxygen vacancies and subsequently form the ultimate product through amine cation radical intermediates. This study not only expands the application potential of Bi-based composite semiconductors but also presents novel insights for synthesizing N-benzylene butylamine.

Biomass-based 2,5-bis(hydroxymethyl)furan (BHMF) is one of the important high value-added chemicals, which can be prepared from inexpensive and renewable carbohydrates through the way of catalytic conversion and selective hydrogenation, and as a widely used chemical intermediate and fuel precursor, it has unique advantages in improving the performance of traditional polyesters and synthesizing new biodegradable bio-based polyesters. In recent years, the research on the production of high value-added chemicals such as BHMF from carbohydrate has been attracting much attention from both academia and industry. However, cleanliness, high efficiency, high selectivity and low-cost remain key challenges in this area, especially for practical applications. In the process of BHMF production, the traditional hydrogenation method consumed a large amount of high-grade energy of hydrogen, and an excessive investment in infrastructure would be generated due to the security risks of higher pressure of hydrogen. On account of the advantages of catalytic transfer hydrogenation, the advances in selective hydrogenation to prepare BHMF using formic acid, alcohols and other types of hydrogen donors by the approach of catalytic transfer hydrogenation is systematically discussed in this review. In view of the features and problems of different types of hydrogen donors, catalysts and reaction processes during the catalytic transfer hydrogenation process, the effects of reaction conditions and process intensifications on the selectivity and yield of BHMF, and the merits and demerits of the reaction system were all investigated. On this basis, the future directions of new catalytic systems for preparation of BHMF by transfer hydrogenation is proposed, and the cleaner, more efficient and essential safety technologies for the production of BHMF is predicted, which will provide some scientific reference for the research and development of related catalytic systems in biomass conversion.

The mechanism of nitrogen oxide (NO) reduction over graphite carbon-supported single-atom iron (Fe) catalyst (Fe/G) was investigated by density functional theory (DFT) and transition state theory (TST). The catalyst deactivation was also analyzed. The results revealed that the NO reduction, based on the Eley-Rideal (E-R) mechanism, underwent four stages including N₂O formation and release as well as N₂ formation and release. However, the NO reduction only involved two stages according to Langmuir-Hinshelwood (L-H) mechanism: N₂ formation and release. Furthermore, for the E-R mechanism, the rate-controlling step was NO reduction, where a NO molecule was adsorbed on an Fe atom with an N, O-down structure with energy barrier of 15.5 kJ/mol, lower than that of other paths. Energy barrier analysis indicated that the energy barrier for the reduction of reactive oxygen species was higher than that for the formation of N₂. Reactive oxygen species remaining on the surface of Fe atoms after NO decomposition inhibited the adsorption and reduction of NO, leading to catalyst deactivation due to the absence of active sites. The single-atom Fe species promoted the NO reduction. Kinetic analysis results suggested that, upon increasing the reaction temperature, the NO reduction rate increased more significantly than the reactive oxygen transfer rate.

A series of spinel catalysts, including ZnFe₂O₄, MgFe₂O₄, CuFe₂O₄, and MnFe₂O₄, were prepared and applied to the Fischer-Tropsch synthesis (FTS). Zn, Mg, Cu and Mn easily form spinels with Fe. Among them, Zn and Mg can significantly maintain the spinel structure during the pretreatment and reaction, resulting in a low CO conversion. Cu and Mn are beneficial to the formation of iron carbide during the reaction, resulting in an apparent influence on FTS performance. ZnFe₂O₄ has little effect on the hydrocarbon distribution and the olefin/paraffin (O/P) ratio of C₂–C₄. MgFe₂O₄ exhibits low selectivity for C₅₊ hydrocarbons, and the selectivity of C= 2−C= 4 and the O/P ratio of C₂–C₄ in the product are increased due to the alkaline effect of Mg. Cu can promote the carbonization of the catalyst, so that CuFe₂O₄ has higher activity. Meanwhile, CuFe₂O₄ can significantly improve the selectivity of C₅₊ hydrocarbons. Moreover, Cu can promote the dissociation and activation of H₂, which is beneficial to the secondary hydrogenation of olefins, thereby reducing the selectivity of C= 2−C= 4 and the O/P ratio of C₂–C₄. Mn promotes carbonization during the reaction, but MnFe₂O₄ has little effect on the chain growth of hydrocarbon. However, Mn can promote the generation of a certain amount of ɛ-Fe₂C, which may explain the higher selectivity of C= 2−C= 4 and the O/P ratio of C₂–C₄ for MnFe₂O₄. All spinel catalysts exhibit low CO₂ selectivity, which meets the current green environmental protection requirements.

Coal gasification fine slag is one of the by-products from clean and efficient utilization of coal, and its resource utilization is extremely urgent. In this work, a high carbon fraction with a fixed carbon content higher than 60% was obtained by simple sieving of gasification fine slag, from which a porous material was prepared by ultrasonic acid leaching method. The adsorption performance of porous materials, being used as treatment of radioactive iodine in nuclear wastewater, is characterized by iodine adsorption value. The effects of ultrasound time, ultrasound power, acid concentration, and temperature on the iodine adsorption performance and compositional structure of the porous materials were systematically investigated by combining the results of SEM, BET, XRD, and FT-IR. The mechanisms of ultrasound-enhanced acid leaching on compositional structure of residual carbon and migration and transformation laws of the ash constituents were explored and summarized. The results show that the porous material prepared under conditions of acid concentration of 4 mol/L, acid immersion temperature of 50 °C, ultrasonic power of 210 W, and ultrasonic time of 1.5 h has the best iodine adsorption performance of 468.53 mg/g, with a specific surface area of 474.97 m²/g, and possesses a rich pore structure with predominant mesopores. The order of each factor on the iodine adsorption performance is: sonication time > acid concentration > sonication power > acid immersion temperature. The mechanism of ultrasonic enhanced acid leaching is that ultrasonic cavitation and mechanical wave action firstly enhance dissociation of carbon-ash adherent particles, thus making desorption of ash particles blocked in pore channels of the gasification slag to increase its connectivity; secondly, lead to generation of cracks on surface of the carbon and ash particles to enhance accessibility of inorganic components inside the carbon particles; and thirdly, enhance the acid leaching process by increasing mass transfer rate to strengthen leaching effect of inorganic components in the gasification slag.