Studies on Catalysis in Partial Oxidation of Methane to Syngas(Ⅰ)──Performance and Characterization of Ni-based Catalysts

IntroductionWiththedevelopmentofanewgenerationofhighlyactivecatalysts,therehasbeenrenewedinterestinthecatalyticpartialoxidationofmethane(POM)tosyngasasapotentialcommercialalternativetosteam-reformingofmethaneinthepastfourorfiveyears.lncontrasttosteam~reforming,thecatalyticpartialoxidationofmethanetosyngas,ismildlyexothermicandmorese1ective,andtheoreticallyyieldsaH,/COratioof2,whichislowerthanthat0btainedbysteam-reforming,andthusismoreappli-cabletotheFischer-TropschSynthesis(FTS)ofhigherhyd…     

Studies on the Performance and Structure of Supported Catalysts for the Partial Oxidation of Methane to Syngas

The catalytic properties of several supported metal catalysts on different carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst performances were significantly influenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also affected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.     

Effect of Ni Loading and Reaction Conditions on Partial Oxidation of Methane to Syngas

The partial oxidation of methane to synthesis gas is studied in this paper over Ni/Al2O3 catalysts under atmospheric pressure. The effects of Ni loading on the activity and stability of catalysts with 5 mm α-Al2O3 and θ-Al2O3 pellets as supports were measured in a continuous fixed bed reactor. It is found that the optimum Ni loading is 10%. And the effect of reaction conditions on partial oxidation of methane is also studied. The methane conversion and CO selectivity increase with the increase of the reaction temperature and the space velocity on 10%Ni/α-Al2O3 catalysts. The best CH4/O2 mole ratio is 2 for CO selectivity, and the optimum space velocity is 5.4x105 h-1.     

Coke-Resistant Ni-based Catayst for Partial Oxidation and CO_2-Reforming of Methane to Syngas

Ｃｏｋｅ┐ＲｅｓｉｓｔａｎｔＮｉ┐ｂａｓｅｄＣａｔａｙｓｔｆｏｒＰａｒｔｉａｌＯｘｉｄａｔｉｏｎａｎｄＣＯ２┐ＲｅｆｏｒｍｉｎｇｏｆＭｅｔｈａｎｅｔｏＳｙｎｇａｓ＊ＣＨＥＮＰｉｎｇ,ＺＨＡＮＧＨｏｎｇ－ｂｉｎ＊＊,ＬＩＮＧｕｏ－ｄｏｎｇ,ＧＵＯＺｈｏ...     

Advances in the Partial Oxidation of Methane to Synthesis Gas

The conversion and utilization of natural gas is of significant meaning to the national economy,even to the everyday life of people. However, it has not become a popular industrial process as expected due to the technical obstacles. In the past decades, much investigation into the conversion of methane,predominant component of natural gas, has been carried out. Among the possible routes of methane conversion, the partial oxidation of methane to synthesis gas is considered as an effective and economically feasible one. In this article, a brief review of recent studies on the mechanism of the partial oxidation of methane to synthesis gas together with catalyst development is wherein presented.     

Recent Progress in Direct Partial Oxidation of Methane to Methanol

The direct conversion of methane to methanol has attracted a great deal of attention for nearly a century since it was first found possible in 1902, and it is still a challenging task. This review article describes recent advancements in the direct partial oxidation of methane to methanol. The history of direct oxidation of methane and the difficulties encountered in the partial oxidation of methane to methanol are briefly summarized. Recently reported developments in gas-phase homogeneous oxidation, heterogeneous catalytic oxidation and liquid phase homogeneous catalytic oxidation of methane axe reviewed.     

In-Situ FT-IR Investigation Methane to Syngas over of Partial Oxidation of Rh/SiO2 Catalyst

Partial oxidation of methane to syngas （POM） over Rh/SiO2 catalyst was investigated using in-situ FT-IR. When methane interacted with 1.0wt%Rh/SiO2 catalyst, it was dissociated to adsorbed hydrogen and CHx species. The adsorbed hydrogen atoms were transferred to SiO2 surface by ＂spill-over＂ and reacted with lattice oxygen to form surface -OH species. POM mechanism was investigated over Rh/SiO2 catalyst using in-situ FT-IR. It was found that CO2 was formed before CO could be detected when CH4 and O2 were introduced over the preoxidized Rh/SiO2 catalyst, whereas CO was detected before CO2 was formed over the prereduced Rh/SiO2 catalyst.     

In-Situ FT-IR Investigation of Partial Oxidation of Methane to Syngas over Rh/SiO_2 Catalyst

Partial oxidation of methane to syngas(POM)over Rh/SiO_2 catalyst was investigated using in-situ FT-IR.When methane interacted with 1.0wt%Rh/SiO_2 catalyst,it was dissociated to adsorbed hydrogen and CH_x species.The adsorbed hydrogen atoms were transferred to SiO_2 surface by"spill-over"and reacted with lattice oxygen to form surface -OH species. POM mechanism was investigated over Rh/SiO_2 catalyst using in-situ FT-IR.It was found that CO_2 was formed before CO could be detected when CH_4 and O_2 were introduced over the preoxidized Rh/SiO_2 catalyst,whereas CO was detected before CO_2 was formed over the prereduced Rh/SiO_2 catalyst.     

Advances in the Partial Oxidation of Methane to Sy thesis Gas

The conversion and utilization of natural gas is of significant meaning to the national economy, even to the everyday life of people. However, it has not become a popular industrial process as expected due to the technical obstacles. In the past decades, much investigation into the conversion of methane, predominant component of natural gas, has been carried out. Among the possible routes, of methane conversion, the partial oxidation of methane to synthesis gas is considered as an effective and economically feasible one. In this article, a brief review of recent studies on the mechanism of the partial oxidation of methane to synthesis gas together with     

Partial Oxidation of Methane to Formaldehyde over Superfine Mo/ZrO_2 Catalysts

Superfine Mo/ZrO_2 catalysts were prepared for partial oxidation of methane to HCHO and characterized by BET, XRD, LRS, H2-TPR and XPS. Mo existed mainly in the form of Zr(MoO4)2, and the catalytic performance and physicochemical properties of the Mo/ZrO2 catalysts were closely related to this species.     

Microwave Effect On Partial Oxidation of Methane to Syngasover Ni/ZrO_2

MicrowavedielectricheatingisfoundtobeanalternativeproceduretoconventionalconductiveheatingforintroducingenergyintocheInicalreactionsandseemstobeawell-suitedprocessforactivatingsolidcatalystS'-'.TheoriginofthendcrowavecouplingdielectricheatingIiesinthecapacityofanelectricfieldtopolarizechargesinamaterial.TheheatingeffectismoreemphasizedwhentheirradiatedmaterialhasastrongdipoIarcharacter.ThisisparticularlythecasewiththosecatalystswhosesupportisanoxidewithnumerouspoIarOHgroups.Moreover,whenpol…     

Partial Oxidation of Methane to Formaldehyde over Superfine Mo／ZrO2 Catalysts

Superfine Mo/ZrO2 catalysts were prepared for partial oxidation of methane to HCHO and characterized by BET,XRD,LRS,H2-TPR and XPS,Mo existed mainly in the form of Zr(MoO4)2,and the catalytic performance and physicochemical properties of the Mo/ZrO2 catalysts were closely related to this species.     

Kinetics of Methane Partial Oxidation to Syngas over a LiLaNiO/γ -Al2O3 Catalyst

The kinetic behavior of partial oxidation of methane to syngas over a LiLaNiO/γ -Al₂O₃ catalyst was investigated under steady-state conditions. Under kinetic control, syngas, to a large extent, is formed via a direct partial oxidation (DPO) scheme. CO and CO₂ are formed in parallel by oxidation reaction over the catalyst. The active sites in the kinetically controlled regime are different from those in the non-kinetic regime, thus the CO selectivity in the former may not increase with temperature. This revised version was published online in June 2006 with corrections to the Cover Date.     

Partial Methane Oxidation to Methanol on Ru-Porphyrins – on the Role of Non-Innocent Ligands and Spin Crossover

The partial oxidation reaction of CH₄ led to the formation of CH₃OH in the presence of Ru-porphyrin oxo complexes (denoted as POR, POR-O and POR-OH where in the case of the last two, oxygen atom and the OH group were attached to the active site, respectively), in which Ru was present on different oxidation states. The simulations were performed based on Density Functional Theory (DFT) with extended geometric and electronic structure analyses of each reaction step. Moreover, the reaction pathways were investigated in different spin states. The Spin Crossover (SCO) phenomenon was found to play an important role in the kinetics of the reaction in the presence of POR and POR-O. Harmonic Oscillator Model of Aromaticity (HOMA) index was applied for different spin states to estimate the aromaticity changes of the pyrrole rings in the Ru-porphyrin complexes. In order to characterize the nature of bonding, the Natural Bond Orbitals (NBO) analysis including the Wiberg Bond Index (WBI) and Natural Population Analysis (NPA) was carried out. Finally, the Non-Covalent Interactions (NCI) index was employed to gain insight into interactions between the components of the reaction. It was found that the non-covalent interactions cannot be neglected in the studied reaction paths.     

Kinetics and Mechanism of Oxidation of Lactic Acid by Dihydroxyditelluratoargentate（Ⅲ）in Alkaline Medium

The kinetics of the oxidation of lactic acid(Lac) by dihydroxyditelluratoargentate(Ⅲ）[abbreviated as DDA of Ag(Ⅲ）]anions was studied in an aqueous alkaline medium by conventional spectrophotometry in a temperature range of 25-40℃.The order of the redox reaction of lactic acid and DDA was found to be first-order.The rates increased with the increase in [OH^-]and decreased with the increase in [tellurate].No free radical was detected.In the view of this the dihydroxymonotelluratoargentate(Ⅲ）species(DMA) is assumed to be the active species.A plausible mechanism involving a two-electron transfer is proposed,and the rate equation derived from the mechanism can be used to explain all the experimenttal results.The activation parameters(25℃）and the rate constants of the rate-determining step along with the preequilibrium constants at different temperatures were evaluated.     

Kinetics and Mechanism of Oxidation of Ethylene Glycol Monoethylether by Diperiodatonickelate（IV） in Alkaline Medium

The kinetics of oxidation of ethylene glycol monoethylether (EGE) by diperiodatonickelate(IV) ion (DPN) was studied by spectrophotometry in alkaline medium. The reaction rate showed first order dependence on Ni(IV) and positive fractional order with respect to EGE. The pseudo-first order rate conslants, kobs increased with the increase of [OH^-] and decreased with the increase of [IO4^- ]. Added salts had little effect on the rate and no free radical was detected. Based on these,the mechanism including the equilibrium between DPN and EGE was proposed. Furthermore, the activation parameters of the reaction were calculated.