Journal of Natural Gas Chemistry最新文献

Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La₂O₃, ZnO, Y₂O₃ or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH₃ temperature-programmed desorption (NH₃-TPD), H₂ temperature-programmed reduction (H₂-TPR), N₂ adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrAl. The addition of ZnO or Y₂O₃ promoted the conversion of CH₄. In the absence of water vapor, Pd/ZnZrAl exhibited the best activity for CH₄ conversion with the light-off temperature (T₅₀) of 275 °C and the complete conversion temperature (T₉₀) of 314 °C, respectively. However, in the presence of water vapor, Pd/YZrAl was the best one over which the light-off temperature (T₅₀) of methane was 339 °C and the complete conversion temperature (T₉₀) was 371 °C. These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H₂O poisoning for the exhaust purification of lean-burn natural gas vehicles.

An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction by simple oxalic acid treatment was investigated. The samples were characterized by XRD, SEM, N₂ adsorption-desorption, XRF, TG, ²⁹Si MAS NMR and NH₃-TPD techniques. The results indicated that the external surface acidity of SAPO-34 was finely tuned by oxalic acid treatment, and the selectivity to C₂H₄ on SAPO-34 and the catalyst lifetime in the methanol-to-olefin reaction were greatly improved.

Catalytic decomposition of methane using a Fe-based catalyst for hydrogen production has been studied in this work. A Fe/Al₂O₃ catalyst previously developed by our research group has been tested in a fluidized bed reactor (FBR). A parametric study of the effects of some process variables, including reaction temperature and space velocity, is undertaken. The operating conditions strongly affect the catalyst performance. Methane conversion was increased by increasing the temperature and lowering the space velocity. Using temperatures between 700 and 900 °C and space velocities between 3 and 6 L_N/g_cat.h), a methane conversion in the range of 25%–40% for the gas exiting the reactor could be obtained during a 6 h run. In addition, carbon was deposited in the form of nanofilaments (chain like nanofibers and multiwall nanotubes) with similar properties to those obtained in a fixed bed reactor.

Promoted catalytic reaction between methanol and CO₂ for dimethyl carbonate (DMC) synthesis is conducted over K₂CO₃/CH₃I catalyst in the presence of ionic liquid under microwave irradiation. The effect of ionic liquids incorporated with microwave irradiation on the yield of DMC is investigated. DMC was found to form at lower temperature in a relative short time, which indicated an enhanced catalytic process by ionic liquid. Among the ionic liquids used, 1-butyl-3-methylimidazolium chloride is the most effective promoter. Density functional theory calculations indicate that CO₂ bond lengths and angles changed due to the molecular interaction of ionic liquid and CO₂, resulting in the activation of CO₂ molecules and consequently the acceleration of reaction rate.

A novel particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen is constructed comprising of the upper-layer 5 wt%Na₂WO₄-2 wt%Mn/SiO₂ particle catalyst and the under-layer 3 wt%Ce-5 wt%Na₂WO₄-2 wt%Mn/SBA-15/Al₂O₃/FeCrAl metal-based monolithic catalyst as well as a side tube in the interspaces of two layers for supplementing O₂. The reaction performance of oxidative coupling of methane (OCM) in the dual-bed reactor system is evaluated. The effects of the reaction parameters such as feed CH₄/O₂ ratio, reaction temperature and side tube feed O₂ flowrate on the catalytic performance are investigated. The results indicate that the suggested mode of dual-bed reactor exhibits an excellent performance for OCM. CH₄ conversion of 33.2%, C₂H₄ selectivity of 46.5% and C₂ yield of 22.5% could be obtained, which have been increased by 6.4%, 4.1% and 5.5%, respectively, as compared with 5 wt%Na₂WO₄-2 wt%Mn/SiO₂ particle catalyst in a single-bed reactor and increased by 10.7%, 31.9% and 17.7%, respectively, as compared with 3 wt%Ce-5 wt%Na₂WO₄-2 wt%Mn/SBA-15/Al₂O₃/FeCrAl metal-based monolithic catalyst in a single-bed reactor. The effective promotion of OCM performance in the reactor would supply a valuable reference for the industrialization of OCM process.

Clathrate hydrate can be used in energy gas storage and transportation, CO₂ capture and cool storage etc. However, these technologies are difficult to be used due to the low formation rate and long induction time of hydrate formation. In this paper, ZIF-61 (zeolite imidazolate framework, ZIF) was first used in hydrate formation to stimulate hydrate nucleation. As an additive of clathrate hydrate, ZIF-61 promoted obviously the acceleration of tetrahydrofuran (THF) hydrate nucleation. It shortened the induction time of THF hydrate formation from 2–5 h to 0.3–1 h mainly due to the template function of ZIF-61 by which the nucleation of THF hydrate has been promoted.

In this topic, we first discussed the requirement and performance of supercapacitors using carbon nanotubes (CNTs) as the electrode, including specific surface area, purity and cost. Then we reviewed the preparation technique of single walled CNTs (SWNTs) in relatively large scale by chemical vapor deposition method. Its catalysis on the decomposition of methane and other carbon source, the reactor type and the process control strategies were discussed. Special focus was concentrated on how to increase the yield, selectivity, and purity of SWNTs and how to inhibit the formation of impurities, including amorphous carbon, multiwalled CNTs and the carbon encapsulated metal particles, since these impurities seriously influenced the performance of SWNTs in supercapacitors. Wish it be helpful to further decrease its product cost and for the commercial use in supercapacitors.

Tars and alkali ashes from biomass gasification processes currently constitute one of the major problems in biomass valorisation, generating clogging of filters and issues related with the purity of syngas production. To date, these waste residues find no useful applications and they are generally disposed upon generation in the gasification process. A detailed analysis of these residues pointed out the presence of high quantities of Ca (>30 wt%). TG experiments indicated that a treatment under air at moderate temperatures (400–800°C) decomposed the majority of carbon species, while XRD indicated the presence of a crystalline CaO phase. CaO enriched valorized materials turned out to be good heterogeneous catalysts for biodiesel production from vegetable oils, providing moderate to good activities (50%–70% after 12 h) to fatty acid methyl esters in the transesterification of sunflower oil with methanol.

Cobalt phthalocyanine-graphene (CoPc-Gr) complex are fabricated through π-π interaction of each components, with CoPc adsorbed/inserted on/in the graphene sheets. The obtained complex could be used in the electro-chemical detection of various medicines. CoPc-Gr modified glassy electrode shows excellent response to the electro-oxidation of dopamine (DA) and ascorbic acid (AA), much better than those of CoPc, graphene oxide (GrO) or graphene (Gr) modified electrode. Significantly, the detection of dopamine is a diffusion-controlled process, highly selective, and has a low detection limit and broad linear range.