Photocatalytic Synthesis of Oxygenates from Gaseous CO2 and CH4 over Semiconductor

Photoinduced synthesis of CO2 and CH4 was investigated using a batch reaction system on several photoactive materials supported on silicon dioxide. Single semiconductor showed higher selectivity to C1 compounds. The production of C2-C3 oxygenates took place preferentially on composite semiconductor photocatalysts. In particular, it was found that acetone was the primary product over Cu/CdS-TiO2/SiO2.     

Review of proton conductors for hydrogen separation

There is a global push to develop a range of hydrogen technologies for timely adoption of the hydrogen economy. This is critical in view of the depleting oil reserves and looming transport fuel shortage, global warming, and increasing pollution. Molecular hydrogen (H₂) can be generated by a number of renewable and fossil-fuel-based resources. However, given the high cost of H₂ generation by renewable energy at this stage, fossil or carbon fuels are likely to meet the short- to medium-term demand for hydrogen. In view of this, effective technologies are required for the separation of H₂ from a gas feed (by-products of coal or bio-mass gasification plants, or gases from fossil fuel partial oxidation or reforming) consisting mainly of H₂ and CO₂ with small quantities of other gases such as CH₄, CO, H₂O, and traces of sulphur compounds. Several technologies are under development for hydrogen separation. One such technology is based on ion transport membranes, which conduct protons or both protons and electrons. Although these materials have been considered for other applications, such as gas sensors, fuel cells and water electrolysis, the interest in their use as gas separation membranes has developed only recently. In this paper, various classes of proton-conducting materials have been reviewed with specific emphasis on their potential use as H₂ separation membranes in the industrial processes of coal gasification, natural gas reforming, methanol reforming and the water–gas shift (WGS) reaction. Key material requirements for their use in these applications have been discussed.     

Fe-ZSM-5杂原子分子筛的合成与表征

采用静态水热法分别以正丁胺、四丙基溴化铵为模板剂合成ZSM-5分子筛及Fe-ZSM-5杂原子分子筛；利用XRD与FT-IR对其结构进行表征；考察了Mo改性后分子筛催化剂上甲烷脱氢芳构化的反应性能。结果表明，Fe部分进入了分子筛的骨架，导致分子筛的结晶度及表面酸强度的下降，使Mo／Fe-ZSM-5催化剂的反应性能较Mo／HZSM-5显著下降。     

Nanostructured perovskite oxides as promising substitutes of noble metals catalysts for catalytic combustion of methane

In this review, we summarize the recent development of nanostructured perovskite oxide catalysts for methane combustion, and shed some light on the rational design of high efficient nanostructured perovskite catalysts via lattice oxygen activation, lattice oxygen mobility and materials morphology engineering.     

Decomposition of methane over alumina supported Fe and Ni–Fe bimetallic catalyst: Effect of preparation procedure and calcination temperature

Catalytic decomposition of methane has been studied extensively as the production of hydrogen and formation of carbon nanotube is proven crucial from the scientific and technological point of view. In that context, variation of catalyst preparation procedure, calcination temperature and use of promoters could significantly alter the methane conversion, hydrogen yield and morphology of carbon nanotubes formed after the reaction. In this work, Ni promoted and unpromoted Fe/Al₂O₃ catalysts have been prepared by impregnation, sol–gel and co-precipitation method with calcination at two different temperatures. The catalysts were characterized by X-ray diffraction (XRD), N₂ physisorption, temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) techniques. The catalytic activity was tested for methane decomposition reaction. The catalytic activity was high when calcined at 500 °C temperature irrespective of the preparation method. However while calcined at high temperature the catalyst prepared by impregnation method showed a high activity. It is found from XRD and TPR characterization that disordered iron oxides supported on alumina play an important role for dissociative chemisorptions of methane generating molecular hydrogen. The transmission electron microscope technique results of the spent catalysts showed the formation of carbon nanotube which is having length of 32–34 nm. The Fe nanoparticles are present on the tip of the carbon nanotube and nanotube grows by contraction–elongation mechanism. Among three different methodologies impregnation method was more effective to generate adequate active sites in the catalyst surface. The Ni promotion enhances the reducibility of Fe/Al₂O₃ oxides showing a higher catalytic activity. The catalyst is stable up to six hours on stream as observed in the activity results.     

Enhanced photocatalytic activity of thin TiO2 films dotted with ZnS nanoparticles

The effect of Ni loading on the catalytic activity of Ni/ZrO₂ catalyst for methane steam reforming was investigated. The sample containing 15 wt.% Ni exhibited the highest activity as well as stability at 600°C. An erratum to this article is available at .     

Equilibrium conditions for clathrate hydrates formed from methane and aqueous propanol solutions

Equilibrium conditions for clathrate hydrates formed from methane and different concentrations of 1-propanol or 2-propanol aqueous solutions were experimentally determined at temperatures of 274.0–287.1 K and pressures up to 11.0 MPa. Each propanol has an inhibiting and/or promoting effect on hydrate formation depending on the propanol concentration. A structural transition from a structure I to a different hydrate structure occurred at concentrations between 3 and 5 mass% for 1-propanol and between 2 and 3 mass% for 2-propanol.     

Methane formation from CaCO3 reduction catalyzed by high pressure

Under high pressures of several giga-pascals using hydrothermal diamond anvil cell,methane generated directly from CaCO3 reduction in gold-lined chamber is in situ measured by Raman spectroscopy at the temperature of 550℃ Fhe reducing agents include FeO,SiO and natural fayalite（Fe2SiO4）,and the resource of hydrogen are water and natural serpentine（Mg3Si2O5（OH）4）. The study demonstrates the existence of abiogenic formation of methane under high pressures in the Earth＇s interior and that the application of high pressure to catalyze multicomponent reactions is a very promising method.     

贵金属及其掺杂团簇与甲烷反应研究进展

贵金属在甲烷活化与转化中呈现出优良的反应性。研究气态条件下贵金属物种与甲烷的反应,可以从分子水平上揭示凝聚相贵金属催化体系的活性位点与基元反应机理,为理性设计和改进催化剂提供理论基础。本文综述了贵金属原子、离子、团簇、氢化物、卤化物、氧化物、甲基配合物以及掺杂团簇活化、转化甲烷取得的新进展,并针对不同贵金属体系的甲烷活化机理展开讨论。     

Molecular dynamics simulations of pure methane and carbon dioxide hydrates: lattice constants and derivative properties

ABSTRACT

We report extensive molecular dynamics simulation results of pure methane and carbon dioxide hydrates at pressure and temperature conditions that are of interest to various practical applications. We focus on the calculation of the lattice constants of the two pure hydrates and their dependence on pressure and temperature. The calculated lattice constants are correlated using second order polynomials which are functions of either temperature or pressure. Finally, the obtained correlations are used in order to calculate two derivative properties, namely the isothermal compressibility and the isobaric thermal expansion coefficient. The current simulation results are also compared against reported experimental measurements and other simulation studies and good agreement is found for the case of isothermal compressibility. On the other hand, for the case of isobaric thermal expansion coefficient good agreement is found only with other simulation studies, while the simulation studies are in disagreement with experiments, particularly at low temperatures.