燃料化学学报最新文献

A series of Mo/Sn (1:20, molar ratio) catalysts were prepared by two-step hydrothermal synthesis method, and the effect of calcination temperature of tin precursors on the reaction performance of methanol oxidation to dimethoxymethane (DMM) was investigated. The crystal structure, surface properties, redox property and valence change of molybdenum species of the catalyst were characterized by XRD, Raman, FT-IR, XPS, NH₃-TPD and H₂-TPR. The results showed that Mo1Sn20-600°CSn catalyst exhibited better performance than other catalysts, achieving DMM selectivity of 90% with methanol conversion of 30% at 140 °C. From the characterization results, the surface properties of the tin precursors affected the structure of catalyst, the degree of molybdenum oxide dispersion and valence of molybdenum species, and further influenced the performance of the catalysts. The high temperature calcination of tin precursors is more favorable for the generation of Mo⁶⁺ in the Mo1Sn20 catalyst.

To develop adsorbents suitable for the storage of natural gas by adsorption, activated carbon SAC-02, HKUST-1 and MIL-101(Cr) were synthesized and characterized in terms of structural morphology observation, nitrogen physisorption at 77.15 K, and methane adsorption at 293.15–313.15 K and 0–4 MPa. The methane adsorption isotherms were comparatively correlated with the Toth, D-A and Ono-Kondo equations and the performances of the adsorbent samples were evaluated in terms of the isosteric adsorption heat and the adsorbed phase density. The results indicate that, in comparison with the D-A and Ono-Kondo equations, the Toth equation displays much smaller relative errors in correlating the methane adsorption data and is more suitable for the adsorption equilibrium analysis on the adsorbed natural gas (ANG) system. MIL-101(Cr) exhibits the largest mean isosteric heat for methane adsorption and the density of the adsorbed phase of methane is smaller than that of the liquid methane but increases with the equilibrium pressure; overall, MIL-101(Cr) with the highest adsorption capacity is more suitable for methane adsorption than activated carbon and HKUST-1.

The selective catalytic reduction (SCR) NH₃ catalyst is mainly used in industrial production and automobile exhaust cleaning. In this study, a novel α%Fe₂O₃/ZrTiO₄ (α=0, 8, 12, 15) catalyst was prepared by the coprecipitation impregnation method. The results show that the NO_x conversion rate of 12%Fe₂O₃/ZrTiO₄ catalyst with the optimal composition is high above 80% at 250−400 °C, close to 100% at 300 °C, and N₂ selectivity is high above 90% at 200−450 °C. The redox properties, surface acidity, and O_β/(O_α + O_β) ratio of ZrTiO₄ catalysts are improved after loading Fe₂O₃ on the ZrTiO₄ surface, which is attributed not only to the porous structure of α%Fe₂O₃/ZrTiO₄ catalyst but also to the synergistic interaction between the active component Fe₂O₃ and the support ZrTiO₄. In addition, in-situ DRIFT reactions show that the NH₃-SCR reaction of 12%Fe₂O₃/ZrTiO₄ catalyst follows the Eley-Rideal mechanism. A clear reaction mechanism is conducive to a deeper understanding of the reaction process of NO_x conversion during SCR. This work provides a feasible strategy for Fe-based SCR catalysts to replace V-based catalysts in the medium temperature range in the future.

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.