燃料化学学报最新文献

It is essential to investigate the influence of alkaline earth metals on the pyrolysis mechanism and resulting products of lignin to enhance the efficient thermochemical conversion and utilization of lignin or biomass. In this study, the density functional theory method was used to simulate the pyrolytic reaction pathways of a β-O-4 type lignin dimer model compound (1-methoxy-2-(4-methoxyphenethoxy)benzene, mc) affected by alkaline earth metal ions Ca²⁺ and Mg²⁺. The computational findings suggest that Ca²⁺ and Mg²⁺ tend to combine with the oxygen atom at the C_β position and the oxygen atom on the methoxy group of the lignin dimer model compound, forming stable complexes that modify the bond lengths of the C_α–C_β and C_β–O bonds and affect their pyrolysis energy barriers. During the catalytic pyrolysis process, the presence of Ca²⁺ and Mg²⁺ can promote the concerted decomposition reaction, leading to increased production of products like 1-methoxy-4-vinylbenzene, 2-methoxyphenol and catechol. Meanwhile, they can suppress homolytic cleavage reactions of the C_β–O and C_α–C_β bonds, thereby hindering the formation of other products such as 1-ethyl-4-methoxybenzene and 2-hydroxybenzaldehyde.

Chemical looping oxidative dehydrogenation (CL-ODH) provides a multifunctional conversion platform that can take advantage of the selective oxidation of lattice oxygen in oxygen carrier to achieve high-valued ethane to ethylene conversion. In this study, we explored the effect of B-site element in MgX₂O₄ (X=Cr, Fe, or Mn) spinel-type oxygen carriers on the performance of ethane CL-ODH. The properties test and characterization of MgX₂O₄ spinel were tested by fixed bed and H₂-TPR, O₂-TPD, TG, in-situ Raman, SEM, and TEM. The results showed that because MgCr₂O₄ only released a small amount of adsorbed surface oxygen, it tended to catalyze the conversion of ethane to coke and hydrogen. MgFe₂O₄ facilitated the deep oxidation of ethane into CO₂ by providing more surface lattice oxygen. Meanwhile, since a significant amount of bulk lattice oxygen was released by the MgMn₂O₄ oxygen carrier, it could burn hydrogen in a targeted manner to advance the reaction and increased ethylene’s selectivity. Thereby, MgMn₂O₄ achieved an ethane conversion of 73.72% with an ethylene selectivity of 81.46%. Furthermore, the MgMn₂O₄ catalyst demonstrated stable reactivity and an ethylene yield of about 62.00% in ethane CL-ODH over the 30 redox cycles. The screening tests indicated that the B-site elements in MgX₂O₄ spinel oxides could significantly influence their ability to supply lattice oxygen, thereby affecting their performance in ethane CL-ODH reaction.

Pyrolysis, an economically viable method, thermochemically converts solid fuel into transportation fuels and value-added chemicals, such as clean gas, liquid fuels, and chemicals, alongside undesirable by-products. Photoionization mass spectrometry (PIMS) is a versatile technique for real-time process analysis, offering ‘soft’ ionization for complex analytes, detecting and analyzing ions during in-situ pyrolysis. This review focuses on recent applications of PIMS during pyrolysis of solid fuels (i.e. coal, biomass and energetic materials). It summarizes studies on mass spectrometric analysis combined with different reactors and highlights the benefits through online PIMS as a diagnostic tool for in-situ analysis. It provides an overview of interplay between experimental advancements and models and discusses future perspectives, potential applications in support of mechanistic studies.

Formic acid (FA) is a sustainable liquid organic hydrogen carrier and the catalyst for hydrogen production from FA has received significant attention. However, the development of efficient non-noble metal catalysts still remains challenges. In this work, we provide a technologically rather simple and environmental-friendly strategy to synthesize Co₂P catalyst for dehydrogenation of FA by pyrolyzing soybean powder and cobalt salt. The K-containing solid bases in catalyst could act as Lewis acid sites for the HCOO⁻ intermediate adsorption while the self-doped N could act as Lewis base sites to enhance the H⁺ adsorption. The P contained in soybean could combine with Co to form Co₂P for H−C bond cleavage of HCOO⁻. At a Co(NO₃)₂·6H₂O/soybean mass ratio of 1:15, the as prepared Co₂P catalyst demonstrated a gas production rate of 237.47 mL/(g·h) and a good stability. This study provides a novel strategy to develop non-noble metal heterogeneous catalysts for FA dehydrogenation.

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.