燃料化学学报最新文献

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.

A series of Cu/SiO₂ catalysts modified with lanthanum (La) (30Cu-nLa/SiO₂, n=0, 0.5, 1 and 2) were synthesized using the ethanol (EtOH)-assisted ammonia-evaporation method; their catalytic performance in the gas-phase hydrogenation of methyl acetate (MeOAc) to produce ethanol (EtOH) was investigated. The results indicate that the catalytic performance of Cu/SiO₂ can be greatly enhanced by La modification. In particular, the 30Cu-0.5La/SiO₂ catalyst exhibits excellent performance in the MeOAc hydrogenation; under 230 °C, 2 MPa H₂, an LHSV of 2 h^-1 and an H₂/MeOAc molar ratio of 20, the MeOAc conversion reaches 98.5%, with a total EtOH yield of 97.0%. The N₂-sorption, XRD, ICP-OES, H₂-TPR, FT-IR, TEM, XPS, and AES characterization results reveal that the introduced La metal has a strong interaction with Cu, which can promote the dispersion of the copper species on the SiO₂ support. Moreover, the content of Cu⁺ is increased significantly, which can enhance the electronic interaction with MeOAc via the acyl and methoxide groups and thus promote the hydrogenation of MeOAc to EtOH.

A series of Ce modified CuLDH-Ce_x catalysts were synthesized by adding different amounts of Ce to CuMgAl hydrotalcite (CuLDH) catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), etc. The results showed that the addition of Ce changed the hydrotalcite structure of CuLDH catalyst, and an appropriate amount of Ce increased the surface area of the catalyst and improved the dispersion of Cu particles. At the same time, an appropriate amount of Ce was beneficial for increasing the density of strong alkaline sites and the number of oxygen vacancies on the catalyst surface, promoting the adsorption and conversion of CO₂. Ce was beneficial for adjusting the Cu⁺/Cu⁰ ratio on the catalyst surface, and a higher Cu⁺/Cu⁰ ratio was conducive to the formation of methanol. When the Ce/Cu ratio was 0.3, the catalyst exhibited higher activity with 7.5% CO₂ conversion, 78.4% methanol selectivity and 362.8 g/(kg·h) spatiotemporal yield at 240 °C under 2.5 MPa with a GHSV=9000 mL/(g·h). It was proved by in-situ DRIFTS that CuLDH-Ce0.3 catalyst followed HCOO* reaction path during CO₂ hydrogenation for methanol.

The reasonable matching of zeolite and matrix is one of the most effective strategies to increase the yield of light olefins in naphtha catalytic cracking. However, the influence of the surface Lewis acidity within the matrix on the cracking reactions has remained ambiguous. Therefore, in present study, boron and zinc co-modified γ-Al₂O₃ and tin modified mesoporous silica KIT-6 with tuned surface Lewis acidity were applied to evaluate the cracking reactivity of n-heptane and 1-hexene to light olefins, in which the matrix was used alone and coupled with ZSM-5 zeolite in different packed modes. The effects of the modifiers on the textural properties and surface acidity of γ-Al₂O₃ and KIT-6 were investigated by XRD, TEM, N₂ physical absorption-desorption, and NH₃-TPD. The results showed that B doping reduced the Lewis acidity (both in the amount and acid strength) of γ-Al₂O₃, while the incorporation of Zn doping led to increased Lewis acidity. In addition, the Lewis acidity of ordered mesoporous KIT-6 increased as Sn doping rose. While for pure matrix, the ascend in conversions of n-heptane and 1-hexene was consistent with the increased Lewis acidity of the B and Zn co-modified γ-Al₂O₃ and xSn/KIT-6 rose, along with decreased activation energy. In contrast, when coupled with ZSM-5 zeolite, the highest conversion was achieved in the dual-bed manner of matrix and zeolite, and the conversion increased concomitantly with the increase in the Lewis acidity of the matrix. However, excessive Lewis acidity can accelerate the hydrogen transfer rate while diminishing the selectivity of light olefins.

To investigate the influence of pore structure on the catalytic activity of catalysts, four catalysts including three-dimensionally ordered macroporous-mesoporous (3DOM-m) CeTiO_x, three-dimensionally ordered macroporous (3DOM) CeTiO_x, three-dimensionally ordered mesoporous (3DOm) CeTiO_x and disordered mesoporous (DM) CeTiO_x were synthesized by the sol-gel method. The NH₃-SCR denitration testing results show that the performance of the catalysts with different pore structures follows the sequence of 3DOM-m CeTiO_x>3DOm CeTiO_x>3DOM CeTiO_x>DM CeTiO_x, and the 3DOM-m CeTiO_x shows an excellent catalytic activity, with more than 90% NO conversion in the range of 250–400 °C at a GHSV of 60000 h⁻¹. The characterization of catalysts by XRD, SEM, BET, NH₃-TPD and in-situ DRIFTS indicates that the surface area is not the dominant factor determining the catalytic activity of CeTiO_x. 3DOM-m CeTiO_x has a highly ordered macroporous-mesoporous structure and abundant Bronsted acidic sites, thereby improving the denitrification activity. The NH₃-SCR reaction over the 3DOM-m CeTiO_x mainly follows the L-H and E-R mechanisms.

Cu-Al spinel oxide as a sustained release catalyst gradually releases active metal Cu during the methanol steam reforming reaction, whose catalytic behavior depends strongly on the surface structure of the catalyst. In this context, Cu-Al spinel solid solution is synthesized by a solid phase ball milling method, followed by treating with acidic and basic solutions in order to modulate the surface composition and structure, thereby to further improve the catalytic performance. Nitric acid is effective for the removal of both surface dispersed Cu and Al oxide species, whereas sodium hydroxide is only effective for the removal of Al oxide species, and ammonium hydroxide shows the weakest effect, removing a very small amount of Cu and Al species. Accompanying with the loss of Cu and Al species, the catalyst surface undergoes structural reconstruction, showing a redistribution of Cu species. Consequently, the copper releasing behavior varies drastically. The catalytic testing results show that the nitric acid and ammonium hydroxide treated catalysts present improved activity, where in the former also shows better stability. Sodium hydroxide treatment has a negative effect on the sustained releasing catalytic performance. In combination with the characterization results of the tested catalysts, it is found that both the copper particle dimension and the microstructure strain of sustained released copper play important roles in the catalytic performance. The findings of this report provide a practical method for the improvement of the sustained releasing catalysis.

Carbon nitride (g-C₃N₄) prepared using thermal condensation of urea was pretreated by H₂O₂/NH₃·H₂O and used as support to obtain Fe/g-C₃N₄ catalyst via impregnation method. The catalytic performance of the catalysts both before and after modification was investigated in CO hydrogenation. Combining detailed characterizations, such as XRD, SEM, TEM, FT-IR, TG, CO₂-TPD, CO-TPD, H₂-TPR, contact angle measurement, and N₂ physical adsorption and desorption, we investigated the effects of surface pretreatment on the texture properties of Fe/g-C₃N₄ catalysts and the product distribution of CO hydrogenation. The results demonstrate that various pretreatment techniques have significant influences on the textural properties and catalytic performance of the catalysts. The prepared g-C₃N₄ with a typical honeycomb structure has strong interaction with highly dispersed Fe. Both before and after modification, the materials are hydrophilic, and the hydrophilicity is increased after treatment with H₂O₂ and NH₃·H₂O. Treatment with H₂O₂ enhances surface hydroxyl groups. NH₃·H₂O treatment improves surface amino groups, promotes CO adsorption, and facilitates the formation of Fe(NCN) phase. The surface basicity of all pretreated catalysts is enhanced. The water gas shift (WGS) reaction activity of the two-step modified catalyst Fe/AM-g-C₃N₄ was lower, and the CO₂ selectivity in CO hydrogenation was reduced to 11.61%. Due to the enhanced basicity of Fe/AM-g-C₃N₄, the secondary hydrogenation ability of olefins was inhibited to obtain higher olefin selectivity with C= 2–C= 4 of 32.37% and an O/P value of 3.23.

Catalytic combustion is an effective approach to remove volatile organic compounds, in which the development of highly active and durable catalyst is extremely crucial. Herein, a series of CuMnCe_x/Al₂O₃/cordierite monolithic catalysts were synthesized by using the ultrasonic-assisted impregnation method. The physicochemical properties were comprehensively characterized via the BET, XRD, SEM, EDX, H₂-TPR, O₂-TPD, XPS and EPR techniques. The results showed that the catalytic activity of CuMnCe_x/Al₂O₃/Cor for toluene combustion was strongly affected by the Ce content. The CuMnCe₂/Al₂O₃/Cor monolithic catalyst showed the best catalytic activity with toluene conversion of 90% at 263 °C under toluene concentration of 1 g/L and space velocity of 78000 mL/(g·h). Meanwhile, the well-dispersed CeO₂ in the CuMn matrix not only improved the content of oxygen vacancies and the mobility of oxygen species, but also enhanced the low-temperature reducibility of the catalyst. Moreover, the CuMnCe₂/Al₂O₃/Cor monolithic catalyst exhibited an excellent stability in the long-term test and cycle ability test.