燃料化学学报最新文献

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.

The TiO₂ nanotubes arrays/SnO₂-Sb (TNTs/SnO₂-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO₂-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.

Phenolic derivatives, crucial components of bio-oil, require thorough understanding of their electrocatalytic hydrogenation (ECH) properties for efficient bio-oil utilization. This study investigated guaiacol, a representative phenolic derivative in bio-oil, focusing on its ECH mechanism, conversion, and product selectivity under varied conditions (temperature: 40–80 °C, perchloric acid concentration: 0.2–1.0 mol/L, current intensity: ((–10)–(–150) mA). Additionally, this study also explored the influence of intermediate products (2-methoxycyclohexanone and cyclohexanone) on both the conversion rate and the selectivity of the products. The experiment had revealed that guaiacol's ECH conversion rate improved with higher temperature and current intensity, whereas an increase in perchloric acid concentration negatively affected the conversion. Significantly, the presence of intermediate products, especially 2-methoxycyclohexanone, markedly enhanced the ECH conversion of guaiacol. Investigating further into the ECH mechanism of other phenolic derivatives, including phenol, pyrocatechol, guaiacol eugenol, and vanillin, as well as their combination, revealed a trend where conversion rates inversely correlated with the complexity of the functional groups on the benzene ring. Specifically, phenol, with its simpler structure, showed the highest conversion rate at 89.34%, in stark contrast to vanillin which, owing to its more complex structure, exhibited the lowest at 46.79%. In our multi-component mixture studies, it was observed that synergistic and competitive interactions significantly alter ECH conversion rates, with some mixtures showing enhanced conversion rate indicative of synergistic effects.

Cuprous oxide (Cu₂O) is an ideal visible light catalyst owing to its narrow band gap, environmental benignity and abundant storage; however, the fast recombination of photogenerated charge carriers and poor stability of Cu₂O has impeded its application in photocatalysis. Herein, we demonstrate that Cu₂O@C nanocomposite can spontaneously evolve from a methanol aqueous solution containing cupric ions under the induction of irradiation. Compared with the traditional carbon coating method, the Cu₂O@C nanocomposite obtained by the photo-induced in-situ synthesis can reserve superior original characteristics of the semiconductor under mild reaction conditions, promote the charge transfer and enhance the separation efficiency of charge carriers; in addition, the carbon shells can also effectively prevent Cu₂O from photo-corrosion. As a result, the Cu₂O@C nanocomposite exhibits excellent photocatalytic activity in the hydrogen evolution in comparison with the Cu₂O particles; the H₂ evolution rate over the Cu₂O@C nanocomposite reaches 1.28 mmol/(g·h) under visible light, compared with the value of 0.065 mmol/(g·h) over Cu₂O. Moreover, the Cu₂O@C nanocomposite displays good cycle stability, viz., without any deactivation in the catalytic activity after five cycles.

A stable metal-organic framework (MOF), MIL-101(Fe), was successfully synthesised using a solvothermal method and employed as a novel photocatalyst for degrading crude oil in oilfield wastewater. Through optimisation of reaction conditions, the following optimal parameters were determined: a dark reaction time of 30 min, a light reaction time of 30 min, a pH of 5.5, a catalyst amount of 150 mg/L, and a reaction temperature of 303.15 K. Under these reaction conditions, an impressive removal of 94.73% was achieved. This study represents the first application of Fe-based MOFs in the photocatalytic degradation of oilfield wastewater. MIL-101(Fe) notably demonstrated excellent stability under mild acid conditions and can be efficiently recycled. These findings offer valuable insights into using MIL-101(Fe) as a promising material for industrial applications in removing crude oil from oil-polluted water through photocatalytic degradation.

Coal and residuum are first co-pyrolyzed, and then hydrogenated into small molecule products during co-liquefaction. Therefore, clarifying influence of residuum on coal pyrolysis performance is an important thermochemical basis for regulating the process. The co-pyrolysis behavior of atmospheric residuum (AR) and Naomaohu coal (NMH) were investigated by TG, TG-FTIR and distributed activation energy model. The results showed that the peak temperature of the maximum rate of weight loss for the co-pyrolysis process was reduced by 7 °C compared with the theoretical value calculated by weighted average of AR and NMH pyrolysis alone, while the weight loss increased by 3%, the average activation energy decreased by 23.6 kJ/mol. In addition, the peak area of alkyl O-containing functional groups such as alcohols and ethers increased, whereas those of CO and CO₂ decreased, suggesting that AR had a positive effect on NMH pyrolysis. Meanwhile, alkyl radicals from AR decomposition would combine with O-containing radicals generated from coal pyrolysis, thus resulting in a decrease of CO and CO₂ by inhibiting breakage of carboxyl groups. This work will provide a scientific evaluation basis for revealing the influence of residuum on composition of coal liquefaction product during co-liquefaction.

The costly separation of 1,2-propanediol (1,2-PDO), an unavoidable byproduct in the hydrogenation of dimethyl oxalate (DMO), significantly hampers the economic viability of coal-to-ethylene glycol (EG) technology. To address this challenge, the formation mechanism of the side product 1,2-PDO on the Cu(111) and Cu₂O(111) surfaces during DMO hydrogenation was investigated, which focused on the active sites of copper catalyst and the dominant pathway through density functional theory calculation. The thermodynamics of each elementary step and the adsorption behavior of various species involved in the reaction network along with the local density of states and charge density difference were systematically analyzed. The results indicate that 1,2-PDO is generated more favorably on the Cu₂O(111) surface than that on the Cu(111) surface, owing to the Lewis acid-base pairs, i.e. Cu+ us and O– suf sites, present on the Cu₂O(111) surface, which strengthens the binding of reactants, products, and reaction intermediates to the substrate. EG reacts primarily with methanol (MeOH) to form 1,2-PDO through Guerbet alcohol condensation reaction through three consecutive steps: alcohol dehydrogenation, aldol condensation, and unsaturated aldehyde hydrogenation. The O– suf sites promote the dehydrogenation of alcohols into aldehydes, the generation of enolates during aldol condensation and the hydrogenation of unsaturated aldehydes, while the Cu+ us sites are responsible for the C–C coupling reaction. These findings may shed light on the mechanism of 1,2-PDO formation over Cu catalyst and provide fundamental knowledge for the development of more efficient catalysts and process optimization.

Aromatic hydrocarbons, especially monocyclic aromatic hydrocarbons such as benzene, toluene, and xylene (BTX), are important basic raw materials in the chemical industry, which are mainly derived from the catalytic reforming and thermal cracking of fossil fuels. The co-catalytic pyrolysis of biomass and plastic to produce aromatics has the advantages of high efficiency, environmental protection, low cost, and high selectivity. It can solve the problems of pyrolysis products such as high oxygen content, low aromatics yield, and low selectivity, which are caused by the characteristics of biomass rich in oxygen and poor in hydrogen. This article reviewed the research progress of co-catalytic pyrolysis of biomass and plastics to prepare aromatic compounds. Firstly, the types of raw materials for co-catalytic pyrolysis were introduced, and then the co-catalytic pyrolysis catalysts were emphasized. The reaction mechanisms of co-catalytic pyrolysis of biomass and plastics, such as the synthesis of dienes and hydrocarbon pool synergy were summarized. Finally, the future research focus and development direction of co-catalytic pyrolysis of biomass and plastics were proposed, which is developing the highly active and stable modified molecular sieve catalysts in order to improve the aromatics yield.