Oxidative Conversion Of Methane Research Articles

Experience of Control over Process of Chemical-Informational Synthesis

Conditions under which various kinds of carbon nanoparticles are obtained by thermal oxidative conversion of methane in chlorine in the temperature range 20-500°C were studied. The influence exerted by conditions of synthesis of nanodispersed carbon on the properties of its samples was analyzed.

A Comparison of LSCF-6428 and Bys for the Oxidative Conversion of Methane and Ethane

Results are reported for a comparative study of Bi1.5Y0.3Sm0.2O3-δ (BYS) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF-6428) in terms of their respective OCM activities, interactions with ethane, and stabilities in reducing environments. The results show that BYS is a superior OCM catalyst, having rates that are nearly 6 times greater and yields that are more than two times higher than those of LSCF-6428. On the other hand, using in situ dynamic XRD, BYS was observed to undergo a phase transformation at about 700 °C when in the presence of methane at pressures as low as 0.1 atm. Higher methane pressures resulted in more severe crystalline changes and could not be inhibited by the addition of 3% oxygen. The catalytically active species appear to be the oxides of BYS constituent cations, all of which are known OCM catalysts. LSCF-6428, on the other hand, is somewhat more resistant to methane and can be stabilized at high methane pressures by the addition of 3% oxygen. At OCM temperatures, neither material catalyzed ethane reactions. Instead, ethane underwent gas-phase oxidative dehydrogenation and thermal cracking reactions.

Influence of SnO 2-doped W-Mn/SiO 2 for oxidative conversion of methane to high hydrocarbons at elevated pressure

The SnO 2-doped 5% Na 2WO 4-2% Mn 2O 3/SiO 2 catalyst for oxidative conversion of methane to high hydrocarbons has been studied in a micro-stainless-steel reactor at elevated pressure. At 1053 K, 1.0×10 5 h −1 GHSV and 0.6 MPa, a CH 4 conversion of 33.0% with C 2+ selectivities of 73.1% is obtained; here the C 2, C 3 and C 4 hydrocarbons selectivities of 36.8, 14.2 and 22.1% are observed. On addition of SnO 2, conversion of methane and selectivities of C 3–C 4 hydrocarbons increase obviously. The observed results show the storage-oxygen capability in Na-W-Mn/SiO 2 catalyst is enhanced with adding SnO 2, for Mn and Na 2WO 4 migrate to near-surface to result in a marked shift to higher molecular weight products. The distribution of products at the operating conditions and content of SnO 2 loading has been described.

CeO2-promoted W-Mn/SiO2 catalysts for conversion of methane to C3-C4 hydrocarbons at elevated pressure.

A CeO2-doped Na-Mn-W/SiO2 catalyst for oxidative conversion of methane has been studied in a micro-stainless-steel reactor under elevated pressure; a CH4 conversion of 47.2% with a C3-C4 selectivity of 47.3% (C2:C3:C4 = 1:1:3.3) was obtained at 983 K with 1.0 x 10(5) ml g-1 h-1 GHSV, CH4/O2 = 2.5 and P = 0.6 MPa.

The direct partial oxidation of methane to organic oxygenates using a dielectric barrier discharge reactor as a catalytic reactor analog

The present work discusses the direct oxidative conversion of methane to organic oxygenates (methanol, formaldehyde, methyl formate, and formic acid) using a dielectric barrier discharge (DBD) reactor. The DBD reactor can be considered an analog to a catalytic reactor because, just as with the catalytic reactor, the DBD reactor reduces the required temperature and pressure needed for reactions to occur within it as well as control product selectivity. In this study, the effects of changing the electrical properties within a methane–oxygen DBD system were investigated. Increasing the gas gap from 4.0 to 12.0 mm caused the reduced electric field to decrease from 30 to 18 V/cm/Torr, which resulted in a shift in the product distribution from organic oxygenate liquids to ethane and acetylene. The effects of temperature on product selectivity were also studied through the use of a water jacket. Lowering the temperature of water within the water jacket from 75 to 28°C resulted in a 54% increase in organic oxygenate selectivity and a 56% decrease in CO x selectivity.

Steam and oxysteam reforming of methane to syngas over Cox Ni1−x O supported on MgO precoated SA‐5205

AbstractCatalytic steam and oxysteam reforming of methane to syngas studied involves coupling of exothermic oxidative conversion and endothermic steam‐reforming processes over Cox Ni1−x O (x = 0.0–0.5) supported on MgO precoated commercial low surface area (<0.01 m2 g−1) macroporous silica‐alumina SA‐5205 catalyst carrier. The influence of the Co/Ni ratio of the catalyst on its performance in steam and oxysteam reforming processes (at 800 and 850°C) was studied. For the steam reforming process, the Co/Ni ratio influences strongly on the methane and steam conversion and CO selectivity and product H2/CO ratio, particularly at lower temperature. When the Co/Ni ratio is increased, the methane and H2 O conversion and CO selectivity are decreased markedly. For the oxysteam reforming process, the influence of the Co/Ni ratio on the performance is smaller and depends on process conditions. When the Co/Ni is increased, the methane conversion passes through a maximum at the Co/Ni ratio of 0.17. The influence of the reaction temperature (800 and 850°C) and CH4/O2 and CH4/H2 O ratios on the conversion, selectivity, H2/CO product ratio, and net reaction heat (ΔHr ) was studied in the oxysteam reforming (at space velocity of 47,000 cm3·g−1·h−1) over the catalyst with an optimum Co/Ni ratio (0.17) and a higher Co/Ni ratio (1.0). The oxysteam reforming process involves coupling the exothermic oxidative conversion of methane and the endothermic methane steam reforming reactions, making the process highly energy‐efficient and nonhazardous. This process can be made thermoneutral, mildly exothermic, and mildly endothermic by manipulating process conditions.

Partial oxidation of methane on potassium-promoted WO 3/SiO 2 and on K 2WO 4/SiO 2 catalysts

The partial oxidation of methane to formaldehyde or ethane and ethylene was studied on K 2WO 4 deposited on various supports, on potassium-promoted WO 3/SiO 2 and for comparison on WO 3/SiO 2 in a fixed-bed continuous-flow reactor at 860–923 K using O 2 as oxidant. The catalysts were characterised by Raman, XP spectroscopy and TPR method. It was found that the original structure of potassium tungstate remained on K 2WO 4/SiO 2, whereas K 2W 2O 7 was very likely formed on K+WO 3/SiO 2. The main products of the reaction besides the carbon oxides were HCHO on WO 3/SiO 2 while on K-containing samples mainly the C 2 hydrocarbons were formed. The product distribution of the oxidation reaction was markedly influenced by the nature of the support. The highest activity was measured for alumina-supported catalyst. In this case, however, only traces of partially oxidised products were formed. Formaldehyde, in a larger quantity, was produced on WO 3/SiO 2 but C 2 in higher selectivity on K 2WO 4/SiO 2 was formed. A possible mechanism for the oxidative conversion of methane is also discussed.

Hydrocarbon conversion on ZSM-5 in the presence of N 2O: relative reactivity and routes of product formation studied by GC-MS and 13C NMR

Oxidative conversion of methane, ethane, propane, benzene, hydrogen and their binary mixtures R1–R2–N 2O–He (where R1, R2 are substances under study) were studied on HZSM-5 at 350–450°C. Relative reactivities were estimated, rate of conversion of hydrocarbons correlating with the strength of CH bond. 13C label distribution in the product of 13CH 4–C 6H 6–N 2O feed was studied by GC-MS, 1H and 13C NMR. It was shown that methane was capable to alkylate the aromatic ring under reaction condition, giving toluene and xylenes from benzene.

Physicochemical and catalytic properties of glass crystal catalysts for the oxidation of methane

Magnetic microspheres and cenospheres recovered from fuel ashes were studied by SEM, XRD, electron probe microanalysis, chemical analysis and Mössbauer spectroscopy. The magnetic microspheres were shown to consist of a crystal phase based on a solid solution of Fe 3O 4–Mg, Mn, Ca-ferrite, α-Fe 2O 3 and a glass phase composed of calcium ferrite, fayalite, wollastonite, ferrous olivines and mullite. The morphology of globules and size of crystallites of active phase were established to depend on the basicity of the glass phase. It was shown that catalytic activity of magnetic microspheres and cenospheres in oxidative conversion of methane is determined by component containing iron and depends on its accessibility and distribution on the surface.

Determination of kinetic parameters for complex heterogeneous catalytic reactions by numerical evaluation of TAP experiments

A numerical method is introduced for deriving kinetic parameters by evaluating responses to transient concentration inputs to a catalytic fixed-bed reactor under vacuum conditions (TAP). Complex reaction networks without restrictions regarding the number of reaction steps and the reaction orders are investigated. The method was successfully applied for the estimation of rate constants of parallel and consecutive surface reactions in the oxidative conversion of methane to syngas over a magnesia-supported Pt catalyst.

Solid state aspects of oxidation catalysis

The main subject of this review is the consideration of catalytic oxidation reactions, which are greatly influenced by solid state effects in the catalyst material. Emphasis is laid upon the correlation between the presence of mobile ionic defects, together with the associated ionic conductivity, and the catalytic performance. Both total and selective oxidation reactions and oxidative conversion reactions are considered. Well-known examples of such behaviour include oxidative methane conversion with lanthanide oxides, carbon monoxide oxidation on fluorite type catalysts, selective olefin oxidation using vanadia based catalysts, etc. Furthermore, because oxygen exchange between gas and solid is always part of the oxidation process, this is considered too. The discussion of the application of the solid oxides under consideration to practically important oxidation processes, together with the influence thereon of their solid state properties, forms a major part of this review. Computational modelling and simulation of catalyst structure and behaviour is also considered. Special attention is given to the potentialities offered by using ionic and mixed conducting oxides either as the electrode material in a solid electrolyte fuel cell (SOFC) or as a separating, dense membrane in a ceramic membrane reactor. The use of porous membranes in such reactors is also taken into consideration. On the one hand these may be used to study the above relationship between catalytic behaviour and solid state properties, on the other hand to obtain a reactor configuration allowing better use of reactants and/or catalysts. Besides the controlled supply of (or removal) of oxygen to (or from) the side where the catalyst and the reactants are located, a promising feature of both experimental approaches is that the oxygen flux may alter the relative presence of different oxygen species (O 2,O,O 2 −,O 2 2−,O 3 −,O −, etc.) on the catalyst surface. In this way species are provided having a strong influence on the selectivity for partial oxidation reactions and oxidative conversion reactions.

Energy efficient conversion of methane to syngas over NiO–MgO solid solution

Methane-to-CO and H 2 conversion reactions, involving partial oxidation by O 2, oxy-steam reforming, oxy-CO 2 reforming, CO 2 reforming, simultaneous steam and CO 2 reforming, over a NiO–MgO solid solution (Ni/Mg =0.5) have been investigated. The calcination (up to 1200°C) temperature of the catalyst has a small but significant effect on its activity/selectivity in the oxidative conversion of methane to syngas. The reduction (by H 2) temperature of the catalyst has no significant effect on the catalyst's performance. The catalyst shows high activity and selectivity in the oxy-steam reforming and oxy-CO 2 reforming reactions, at 800–850°C and high space velocity [(40–50)×10 3 cm 3 g −1 h −1]. These two processes involve coupling of the exothermic oxidative conversion and endothermic steam or CO 2 reforming reactions, making both the processes highly energy efficient and also safe to operate. The catalyst also shows high methane conversion activity (nearly 95% conversion) with 100% selectivity for both CO and H 2 in the simultaneous steam and CO 2 reforming of methane at (800–850°C) at a high space velocity (3.6×10 3 cm 3 g −1 h −1).

Oxidative conversion of methane to syngas over NiO/MgO solid solution supported on low surface area catalyst carrier

Influence of time-on-stream (0.5–15 h), CH 4/O 2 ratio in feed (1.8–8.0), space velocity (6000–510,000 cm 3 g −1 h −1), catalyst particle size (22–70 mesh), and catalyst dilution by inert solid particles (diluent/catalyst weight ratio=4) on the performance at different temperatures (600–900°C) of the NiO/MgO solid solution deposited on SA-5205 [which is a low surface area macroporous silica-alumina catalyst carrier] in the oxidative conversion of methane to syngas (a mixture of CO and H 2) has been investigated. The dependence of conversion and selectivity on the space velocity is strongly influenced by the temperature. Both the conversion and selectivity for H 2 and CO are decreased markedly by increasing the CH 4/O 2 ratio in the feed. The catalyst dilution resulted in a small but significant decrease in both the conversion and selectivity for H 2 and CO. The increase in the catalyst particle size had also a small but significant effect on both the conversion and selectivity in the oxidative conversion process. Both the heat and mass transfer processes seem to play significant roles in the oxidative conversion of methane to syngas at a very low contact time or very high space velocity (5.1×10 5 cm 3 g −1 h −1).

99/01146 The study of composition of novel high temperature catalysts for oxidative conversion of methane : Anshits, A. G. et al. Catal. Today, 1998, 42, (3), 197–203

(Ba, Sr)TiO3-Al2O3-SiO2 glass ceramic system with various SiO2/Al2O3 ratios was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), dielectric spectroscopy and impedance spectroscopy. The XRD results demonstrated that the proper SiO2/Al2O3 ratio could promote the crystallization of the major crystalline phase from the glass matrix. The dielectric property investigations showed that the dielectric constant passes through a maximum value while the dielectric breakdown strength has a minimum value with increasing SiO2/Al2O3 ratio. Meanwhile, the complex impedance analyses suggest the resistance of the glass-crystal interface rapidly decreases and the capacitance of the crystal slightly decreases with the increase of SiO2/Al2O3 ratio. The relaxation mechanisms of the (Ba, Sr)TiO3 glass ceramics changed from localized relaxation to long range conductivity as the SiO2/Al2O3 ratio was increased from 1.43 to 1.83. The variations in the dielectric response and the activation energy of the glass-crystal interface in the (Ba, Sr)TiO3 glass ceramics with the ratio of 2.40 could be attributed to the crystallization of fresnoite phase.

99/01139 Novel microdesign of oxidation catalysts. Part 1. Glass crystal microspheres as new catalysts for the oxidative conversion of methane : Fomenko, E. V. et al. Catal. Today, 1998, 42, (3), 267–272

99/01139 Novel microdesign of oxidation catalysts. Part 1. Glass crystal microspheres as new catalysts for the oxidative conversion of methane : Fomenko, E. V. et al. Catal. Today, 1998, 42, (3), 267–272

99/00361 Process for the preparation of an improved supported catalyst, containing nickel and cobalt, with or without noble metals, useful for the oxidative conversion of methane, natural gas and biogas to syngas

99/00361 Process for the preparation of an improved supported catalyst, containing nickel and cobalt, with or without noble metals, useful for the oxidative conversion of methane, natural gas and biogas to syngas

99/00310 Composite catalysts containing transitional and alkaline earth metal oxides useful for oxidative conversion of methane (or natural gas) to carbon monoxide and hydrogen (or synthesis gas)

99/00310 Composite catalysts containing transitional and alkaline earth metal oxides useful for oxidative conversion of methane (or natural gas) to carbon monoxide and hydrogen (or synthesis gas)

99/00279 Oxidative conversion of methane to CO and H 2 over Pt or Pd containing alkaline and rare earth oxide catalysts

99/00279 Oxidative conversion of methane to CO and H 2 over Pt or Pd containing alkaline and rare earth oxide catalysts

Inhibition of gas-phase oxidation of ethylene in the oxidative conversion of methane and ethane over CaO, La 2O 3/CaO and SrO–La 2O 3/CaO catalysts

The conversion of methane, ethane and ethylene has been investigated either in an empty reactor or in the presence of a series of calcium-based catalysts including unpromoted calcium oxide (C), calcium oxide promoted with lanthane (LC) and with both lanthana and strontium oxide (SLC). It was found that these solids inhibit the gas-phase oxidation of ethylene, probably by trapping chain-carrier radicals. At T>1000 K, the inhibiting effectiveness varies in the order C<LC<SLC which parallels the C 2+ yield sequence in the oxidative coupling of methane (OCM). This strongly suggests that the inhibiting effect, thus observed in separate experiments, is operating in OCM conditions, preventing ethylene from further degradation. This sequence is also found to be similar to that of the strong basicity of solids as deduced from the temperature of CO 2 desorption, indicating that this inhibiting effect might be related to the basicity of the catalyst. Finally the beneficial role of each components in the optimized catalyst (SLC) is discussed: lanthana might be an inhibitor of methyl radical or methane oxidation into CO, calcium oxide a promoter of ethane dehydrogenation into ethylene and strontium oxide might play the role of an inhibitor of the gas-phase oxidation of ethylene.

Oxidative conversion of methane to CO and H2 over Pt or Pd containing alkaline and rare earth oxide catalysts

A number of Pt (1.0 wt%) and Pd (1.0 wt%) containing alkaline earth oxide (namely, MgO and CaO) and rare earth oxide (namely, La2O3, Pr6O11, Nd2O3, Sm2O3, Gd2O3, Dy2O3 and Er2O3) catalysts have been compared for their performance in the oxidative conversion of methane to CO and H2 at 700 and 800°C and at very low contact time [GHSV = 5.0 (±0.2) × 105 cm3.g−1.h−1]. The catalysts are characterized by their specific surface area and H2 chemisorption at 40°C. Among the Pt- and Pd-containing catalysts, the best performance is shown by Pt/Gd2O3 and Pd/Sm2O3, respectively. These catalysts show high selectivity for CO but low selectivity for hydrogen due to reverse water gas shift reaction. Since alkaline and rare earth oxides are basic in nature, they act not only as a support for dispersing noble metals but also play a significant role in deciding the activity/selectivity of the Pt- or Pd-containing catalysts.