燃料化学学报最新文献

A series of Mn/CeO₂ catalysts modified with different Fe contents were prepared by impregnation method and tested for their low-temperature performance for simultaneous de-nitrification and toluene removal. It was found that the Fe₅Mn/CeO₂ catalyst showed the best catalytic performance and the conversion efficiency of toluene reached 90% at 175 °C and NO conversion reached 90% at 95−300 °C. The physical and chemical properties of the catalysts were characterized by BET, SEM, XRD, XPS, H₂-TPR, NH₃-TPD and O₂-TPD. XPS results showed that the increased content of Ce³⁺ and Mn⁴⁺ in the Fe₅Mn/CeO₂ catalyst promoted the formation of oxygen vacancies and unsaturated chemical bonds, providing more active sites, thus facilitating the efficient removal of NO and toluene at low temperatures. Compared with other catalysts, H₂-TPR, NH₃-TPD and O₂-TPD indicate that Fe₅Mn/CeO₂ catalyst has great redox ability, stronger acidity and better oxygen migration ability. In addition, this paper explores the effects between selective catalytic reduction (NH₃-SCR) and catalytic oxidation reaction of toluene over Fe₅Mn/CeO₂ catalyst. NH₃ preferentially reacts with the active site on the catalyst to inhibit the toluene oxidation process, while NO promotes the toluene removal process. Toluene can promote the NH₃-SCR process in a certain temperature range. While NO promotes the formation of NO₂, NO₂ effectively promotes the combination of toluene and active sites, which is conducive to the catalytic oxidation of toluene; The inhibition of toluene on the NH₃-SCR process weakens with the increase of temperature. At 100 °C, the inhibition of toluene on the NH₃-SCR process disappears. When the temperature exceeds 225 °C, toluene reacts with NO as a reducing agent and promotes the formation of NO₂, thus promoting the NH₃-SCR reaction.

Aqueous phase reforming (APR) of methanol is a potential pathway for the effective hydrogen production under relatively mild conditions. The Pt/CeO₂ and a series of Pt-MO_x/CeO₂ (M = Fe, Cr, Mg, Mn) catalysts were prepared by sequential impregnation method and their APR reaction performances were studied. The catalyst properties including valence state of the promoters, the amount of oxygen vacancies, the metal distributions, the adsorption properties of CO and the acidity/basicity of catalysts were characterized and analyzed by XPS, XRD, TEM, CO-TPD, NH₃-TPD, CO₂-TPD, etc. It was found that the addition of MO_x weakened the Pt-CeO₂ interaction and promoted the generation of Pt^δ+ species with lower valence state, which contribute to the C–H bond cleavage and facilitate methanol conversion. The highest hydrogen production (164.78 mmol) and relatively low CO and CH₄ selectivities were obtained over the Pt-MgO/CeO₂, while the highest CH₄ selectivity was obtained over the Pt-CrO_x/CeO₂ (2.21%). Over the Pt/CeO₂ and Pt-MO_x/CeO₂ (M = Fe, Cr, Mg, Mn) catalysts, CO₂/CH₄ ratio correlated well with the catalyst basicity, indicating that the basicity promotes the dissociation adsorption of H₂O as well as the water-gas shift (WGS) reaction activity and decreases the methanation activity.

The photocatalysis of direct dehydrogenation of benzyl alcohol to benzaldehyde is an energy saving way to synthesize fine chemicals and pure hydrogen by using solar energy. The CdS-based catalysts were one of the typical kinds of photocatalysts for this reaction. The morphology of CdS could be easily tuned, which could greatly influence the photocatalytic performances. However, the morphology effect of CdS on the photocatalytic behaviour of the direct dehydrogenation of benzyl alcohol has not been investigated yet. In this work, we synthesized CdS with two different morphologies (nanosheet (NS) and nanowire (NW)) and found the CdS-NS showed much higher photocatalytic activity for converting the benzyl alcohol than the CdS-NW, but the selectivity to benzaldehyde over the two supports was very low. By depositing Au₂₅ nanoclusters on the CdS-NW and CdS-NS, the morphology effect of the CdS support could be mitigated and their catalytic activity and selectivity could be greatly boosted for the photocatalytic anaerobic dehydrogenation of benzyl alcohol to benzaldehyde and H₂. The results of this work would provide new insight into the design of efficient photocatalysts for synthesizing fine chemicals.

The Cu/SiO₂ catalysts were prepared by co-precipitation and tested for hydrogenation of furfural to furfuryl alcohol in a fixed bed reactor. The deactivation mechanism of the catalysts was investigated by characterization of H₂-TPR, ICP-OES, XPS, TG, Raman and TEM. Under the conditions of atmospheric pressure, reaction temperature of 140 °C, mass space velocity of 2.4 h^–1 and the molar ratio of hydrogen to furfural of 9.7, the furfural conversion was higher than 97% in the first 5 h. However, the conversion of furfural decreased rapidly from 96% to 32% after 21 h of reaction, indicating that Cu/SiO₂ catalyst was rapidly deactivated. The factors for the deactivation of Cu/SiO₂ catalyst were the agglomeration and sintering of the active component copper. Moreover, the carbon deposition on the catalyst surface resulted in the covered active site Cu⁰.

H₂S and CO₂, two harmful acid waste gases, often co-exist in important chemical production such as coal-chemical industry, natural gas chemical industry and petrochemical industry, causing corrosion of industrial equipment and pipelines, and must be treated innocuously. Co-conversion of H₂S-CO₂ mixed acid gas to syngas has been carried out using dielectric barrier discharge (DBD) plasma-catalysis, which renders the highly corrosive and toxic H₂S and greenhouse gas CO₂ harmless, and produces syngas. The effects of various parameters of the DBD plasma on the reaction of one-step conversion of H₂S-CO₂ to syngas were studied. Moreover, a comparative study of the different parameters of DBD plasma was carried out. The intrinsic correlation between the reaction performance of syngas production via H₂S-CO₂ conversion and these parameters, including specific energy input (SEI), discharge shape, discharge frequency, discharge gap and discharge length, was investigated and revealed. On this basis, a multi-tube parallel DBD plasma reaction system was designed and constructed.

Dimethyl carbonate (DMC) is a widely used environment-friendly green chemical, and the direct synthesis of DMC from CO₂ and CH₃OH has become one of the research focuses on the clean conversion of CO₂ in recent years. The design of efficient and stable catalysts and reaction processes to promote the conversion of CO₂ is the key to realize the direct synthesis of DMC in industry. In this paper, the research progress of catalytic systems for the direct synthesis of DMC from CO₂ and CH₃OH is reviewed and the reaction mechanism of different types of catalysts is summarized, mainly including the ionic liquid catalyst, alkali metal carbonate catalyst, transition metal oxide catalyst, etc. The operation principle of various dehydrating agents and their promoting effect on the production of DMC are expounded, while the advantages and disadvantages of different catalytic-dehydration systems are analyzed. It is predicted that the development of efficient and stable catalysts and membrane materials with strong permeability to water as well as the construction and implementation of new dehydration processes will be the focus of future research on the direct synthesis of DMC from CO₂ and CH₃OH.

The catalytic performance of zeolites is closely related to their framework structure and a clear understanding of such a structure-performance relationship is of great significance in revealing catalytic reaction mechanism as well as in developing efficient zeolite catalysts. Herein, ZSM-11 and ZSM-5 zeolites with similar morphology, crystal size, textural properties and acidity were hydrothermally synthesized; the effects of their differences in the 10-ring channels on the catalytic performance in the conversion of methanol to olefins (MTO) were investigated by using various characterization techniques. The results indicate that in comparison with the straight channel of ZSM-11, the sinusoidal channel of ZSM-5 has stronger diffusion resistance, which promotes the hydrogen-transfer in higher olefins, leads to forming more polymethylbenzene species and then raises the contribution of aromatic-based cycle. In contrast, ZSM-11 with straight channel can reduce the formation of polymethylbenzene species and enhance the alkene-based cycle. As a result, compared with ZSM-5-60 with similar morphology and acidity, ZSM-11-60 as a catalyst in MTO exhibits longer lifetime (98.3 h vs. 65.4 h) and higher selectivity to propene (34.6% vs. 27.4%). The insight shown in this work helps to have a better understanding of the relation between zeolite structure and catalytic performance in MTO and is then beneficial to the development of better catalysts and processes for MTO.

Fischer-Tropsch synthesis (FTS) is the key technology of indirect coal liquefaction. Iron-based catalysts are commonly used. Due to the complexity of phase transition and the difficulty of in-situ characterization, density functional theory (DFT) has become a necessary means to study the adsorption and reaction of surface species on iron-based catalysts. In this review, the formation of different iron carbide phases and the adsorption properties of surface species were discussed based on the surface chemical properties of iron-carbon compounds. Then, the elementary reactions involved in the current DFT calculation research are briefly described. The research of chain initiation, chain growth, and chain termination under different mechanisms is summarized. Combined with the experimental research progress, the regulation mechanism of the promoters on the structure and performance of iron-based catalysts was reviewed. Finally, the existing problems of iron-based catalysts are summarized. The role of surface carbon in the reactions and the effects of various phases are prospected combined with recent results.

Shifting products of Fischer-Tropsch Synthesis (FTS) from paraffins to value-added higher alcohols receives great attention but remains great challenge. Herein, metal oxides of Mn, Zn, La and Zr are investigated as promoters to tune the activity and product distributions of Co/AC catalyst for syngas conversion. It is found that these promoters show different promotion effect on CO dissociation rate, the formation of Co₂C phase and the alcohols selectivity. The formed Co₂C/Co⁰ constitutes the dual active site for higher alcohols synthesis. The strongest CO dissociation rate is observed for Zn-promoted Co/AC catalyst, resulting in the highest activity and space-time yield (STY) of alcohols. The Mn promoter is most conducive to the formation of Co₂C, but slightly decreases the activity. The similar CO dissociation rate and CO conversion are obtained over both Zr- and La-promoted Co/AC catalysts, but the Zr-promoted Co/AC catalyst exhibits the highest alcohols selectivity due to the function balance between CO non-dissociative insertion and CO dissociation.

Conversion of saturated straight-chain alkanes generated in the deep desulfurization process of fluid catalytic cracking (FCC) gasoline and the coal-to-oil processes into aromatics via alkane aromatization is an important non-petroleum route for the preparation of aromatics that effectively improves the quality of oil. The aromatization technology of C₂–C₅ light hydrocarbons is relatively mature and has been used in industry. However, for the aromatization of${\text{C}}_{\text{6}}^{\text{+}}$ n-alkanes, the aromatics yield is still very low due to the complex reaction process and the competition of various elemental reactions. In addition, the catalysts usually suffer from rapid deactivation. In this work, we summarize the recent advances in the aromatization of${\text{C}}_{\text{6}}^{\text{+}}$ n-alkanes. The reaction mechanism of aromatization of${\text{C}}_{\text{6}}^{\text{+}}$ alkanes and the effects of the dispersion of metal sites, electronic state, and acidity, morphology and pore structure of the support on the catalytic performance are discussed in detail.