燃料化学学报最新文献

Ammonia is not only the main raw material of nitrogen fertilizer production, but also one of the energy carriers for the storage and conversion process of renewable energy. Therefore, the development of a mild ammonia synthesis technology has become an important research topic in recent years. The chemical looping ammonia synthesis technology decouples the ammonia synthesis reaction into several steps, including the nitrogen fixation and the ammonia release, which has the advantages of easy operation, mild reaction, and low energy consumption. As the key to the chemical looping ammonia synthesis, nitrogen carriers play the role of transferring energy and nitrogen species. However, the current low nitrogen fixation efficiency of nitrogen carriers severely limits the development of the chemical looping ammonia synthesis technology. Therefore, this article reviews the research on the design, preparation and application of nitrogen carriers for the chemical looping ammonia synthesis. Firstly, the design theory of nitrogen carrier is summarized; secondly, the current research status of nitrogen carrier is introduced, with a focus on how to improve the ammonia production rate of nitrogen carrier and the utilization rate of lattice nitrogen; finally, the opportunities and challenges of chemical looping ammonia synthesis technology are discussed, which provide a reference for the design and development of nitrogen carrier in the future.

Calcium cerium-based catalysts with different Ca:Ce molar ratio prepared by sol-gel method were characterized by XRD, N₂ adsorption-desorption, FT-IR, XPS and CO₂-TPD, and evaluated the activity for dimethyl carbonate (DMC) synthesis from propylene carbonate (PC) and methanol. The results indicated that more surface oxygen vacancies and more moderate basic sites are beneficial for methanol activation and thus leading to better catalytic activity. The PC conversion was 91.1% with DMC selectivity of 91.7% over 0.9CaCe under the reaction conditions-reaction time of 2 h, reaction temperature of 40 °C, methanol to propylene carbonate molar ratio of 15:1 and catalyst amount of 4% relative to the amount of PC.

A series of Cu-Mn-Zn/ZrO₂ catalysts with different Zn contents were prepared by sol-gel method and characterized by XRD, BET, TPR, N₂O-adsorption, XPS, TPD and in-situ DRIFTS. It was found that by increasing a certain amount of Zn, the catalytic activity for CO₂ hydrogenation increased. Among all samples, Cu₃MnZn_0.5Zr_0.5 (CMZZ-0.5) possessed the best CO₂ conversion (6.5%) and methanol selectivity (73.7%) at 250 °C and 5 MPa. Characterization results showed that Zn entered the Cu_1.5Mn_1.5O₄ spinel structure, forming ZnO_x and thus more surface OH groups. This increased the content of Cu⁰ and Cu^α, which improved the activation of H₂ and CO₂. The pathway of CO₂ to methanol was also clarified through in-situ DRIFTS.

The reaction mechanism of methanol/dimethyl ether (DME) carbonylation catalyzed by isomorphously substituted B-, Al-, and Ga-MOR zeolites (B/Al/Ga-MOR) was comparatively investigated by the density functional theory (DFT) calculations. The commonalities and differences between methanol and dimethyl ether as the reactant as well as among various MOR zeolites in the catalytic reaction pathways were disclosed, where one Si atom was substituted by B, Al or Ga at the 8-ring side pockets T3 sites or the 12-ring channels T4 sites of MOR. The results indicate that the insertion of CO into methoxy group to form acetyl groups follows the S_N2 mechanism and is the rate-determining step in the carbonylation reactions. Under 473 K, either methanol or dimethyl ether is used as feedstock, the formed acetyl group prefers to interact with CH₃O in methanol to form methyl acetate. The T3 sites show better carbonylation selectivity, whereas T4 sites display better trimethoxonium ions selectivity which favors the generation of aromatics and leads to the catalyst deactivation. Comparing with Al-MOR, the introduction of Ga and B at the T3 sites increases the free energy barriers of carbonylation, whereas the introduction of Ga and B in particular at the T4 sites can substantially increase the energy barriers of generating trimethyloxonium ions, which can effectively suppress the side reaction and improve the catalyst stability. This work contributes to the understanding of the catalytic roles of various acidic sites in different channels of the MOR zeolites and provides certain theoretical support for tailoring and designing efficient MOR zeolite catalysts for methanol/dimethyl ether carbonylation.

Red mud is a solid waste in aluminum industry and has been proven to be an efficient alternative to NO_x selective catalytic reduction (SCR) catalysts. Acid washing treatment to red mud can improve its alkalinity and surface properties, and increase the conversion rate of NO_x. In this paper, Cu, Ce, and Cu/Ce was supported on acid washed red mud and NO_x catalytic conversion performance on metal modified red mud catalysts was studied. The research results indicate that Cu⁺ and Cu²⁺ in the Cu supported catalyst effectively promote NO conversion rate of red mud in low-temperature (200–300 °C) flue gas, reaching a maximum of 90.7%; Ce³⁺ and Ce⁴⁺ in Ce supported catalysts effectively promote the NO conversion rate of red mud in flue gas at 200–400 °C, reaching a maximum of 94.0%; Cu/Ce supporting exhibits better NO conversion rate than single metal supported catalysts at low-temperatures, the optimal Cu:Ce ratio for supporting is 1:1; and also exhibits better NO conversion rate than Cu supported catalysts at high-temperature (300–400 °C), reaching a maximum of 95.5%. The reason may be that under the synergistic effect of Cu/Ce, ACRM-Cu1Ce1 has stronger low-temperature redox ability, higher weak acidic peaks, higher average oxidation state of Fe ions, and higher Cu⁺ content.

In this paper, layered porous carbon sheet (LPCS) was obtained through high temperature calcination under argon atmosphere by using coal pitch as carbon material, sodium chloride as template agent and potassium carbonate as activator. Then, the active component Ru was loaded onto the LPCS support by impregnation to synthesize Ru/LPCS catalyst whose catalytic performance for hydrogen production by hydrolysis of ammonia borane was studied. The results showed that in the presence of light, the maximum value of the turnover frequency (TOF), 334.8 min^–1, was obtained at a calcination temperature of 1123 K and a loading of 2% of Ru which is 1.38 times higher than that in the absence of light. The activation energy (E_a) of the catalyst decreased from 90.60 to 70.33 kJ/mol in the presence of light. The hydrogen production rate order with respect to ammonia borane concentration was 0.75, which is first-order relation to the amount of the catalyst.

An AgY molecular sieve modified by Ag⁺ ion was characterized by XRD, FT-IR and N₂ adsorption and desorption and used to the adsorption denitrogenation from model fuels containing pyridine, aniline and quinoline basic nitrides. The adsorption capacity for N with the AgY molecular sieve was obviously better than that with the NaY molecular sieve. The effects of adsorption temperature and adsorption time on the adsorption capacity of three kinds of nitrides by AgY molecular sieve were investigated. The experimental results show that the adsorption capacity for N is aniline>quinoline>pyridine. To study the adsorption mechanism of AgY, the 12T cluster model of AgY molecular sieve was established by Materials Studio software and the adsorption of three kinds of nitride molecules on the AgY molecular sieve was simulated at 303, 323 and 343 K. The adsorption energy, the distance between the active center and pyridine, aniline and quinoline molecules, the frontier orbit, the isodensity distribution, the radial distribution function and other relevant parameters were calculated. The calculated results show that the adsorption of aniline by AgY molecular sieve is better than that of quinoline and pyridine, which is consistent with the experimental results. Moreover, the adsorption is mainly the chemical adsorption, and the S and W sites of AgY molecular sieve are the main adsorption sites. The results of isothermal adsorption show that the adsorption of pyridine on the AgY follows the Langmuir-Freundlich mixed adsorption model, and the adsorption of aniline and quinoline follows the Freundlich adsorption model. The results of adsorption kinetics and thermodynamics show that the adsorption of pyridine on the AgY molecular sieve conforms to the quasi-second-order kinetic model, while the adsorption of aniline and quinoline conforms to the quasi-first-order kinetic model, and all adsorption processes are spontaneous entropy increasing process.

Using strong-caking coking coal as raw material, coal-based carbon foam (NCF) was prepared by constant pressing and self-foaming method and used as carbon base to produce coal-based active carbon foamed (HPCs) together with KOH activator, which was used as electrode material for double-layer capacitor. The effects of KOH added by mechanical mixing, aqueous solution impregnation and ethanol solution impregnation methods on microstructure and electrochemical properties of the prepared materials were studied. The results show that formation of pore structure, crystal structure, surface chemistry and electrochemical performance of HPCs are significantly affected by KOH dispersion and adhesion. The NCF itself has a three-dimensional connected bubble pore structure, which is conducive to the activator (KOH) penetrating into the bubble pore and providing a large number of attachment sites, thus increasing the contact area between the activator and the carbon matrix and resulting in efficient activation. The good fluidity of KOH solution can make K⁺ more effectively interspersed in the bubble structure of NCF, act on the defect site during activation, and generate more micropores and mesoporous structures on the internal matrix of carbon matrix, effectively amplifying the activation effect. ACF-W obtained by KOH aqueous impregnation has the highest specific surface area (3098.35 m²/g), total pore volume (1.68 cm³/g), mesoporous volume ratio (59.13%). It shows excellent specific capacitance (310 F/g) and cycle stability when used as electrode material.

An Fe-based hydrodesulfurization (HDS) catalyst modified by Y zeolite was developed using Fe as the main active metal and Zn as a promoter. The change of morphology, pore structure, dispersity, reducibility, electronic defect structure and acidity of the Fe-based catalysts before and after modification were investigated using low-temperature nitrogen physical adsorption, X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR), NH₃-temperature programmed desorption (NH₃-TPD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and pyridine infrared spectroscopy (Py-IR). Meanwhile, the HDS performance of the Fe-based catalyst was evaluated using a fixed-bed reactor. The results showed that the introduction of Y zeolite provided the Brønsted (B) acid sites, which increased the sulfur removal rates of Fe based catalysts by 10.7%–34.1%. Meanwhile, the B acid sites improved the selectivity of the direct desulfurization (DDS) reaction pathway. In addition, the B acid sites not only promoted the increase of DDS selectivity but also inhibited further deep hydrogenation of tetrahydrodibenzothiophene (THDBT) and hexahydrodibenzothiophene (HHDBT) in the hydrogenation (HYD) reaction pathway, thereby ensuring an increase in desulfurization efficiency while reducing hydrogen consumption. The fundamental reason was that the introduction of Y zeolite enhanced the acidity of the modified catalyst, especially the interaction between B acid sites and active metal promoted electron transfer, which adjusted the electronic defect structure of Fe species, resulting in the improvement of HDS performance.

A series of Cu_1–xZr_xO₂ bimetallic oxides with different Cu-Zr molar ratios for glycerol carbonate synthesis from glycerol and CO₂ were prepared by hydrothermal method. The results found that the performance was significantly affected by the Zr doping amounts. Under the optimal reaction conditions, the Cu_0.99Zr_0.01O₂ catalyst had the best catalytic performance. The conversion of glycerol and the selectivity of glycerol carbonate reached 64.1% and 85.9%, respectively. Cu_1–xZr_xO₂ complex oxide exhibited better activity than pure CuO and pure ZrO₂. The structures, morphologies and surface properties of the catalysts were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption and desorption, Temperature programmed reduction (H₂-TPR), Temperature programmed desorption (TPD) and Fourier Transform Infrared Spectroscopy (FT-IR). It is speculated that the high activity is related to the degree of dispersion of Zr on the surface of CuO, the surface content of oxygen species and the number of acidic-basic sites. In addition, catalytic activity did not change significantly after six cycles, indicating the excellent stability of the catalyst.