Oxidation Reforming Of Methane Research Articles

Thermodynamic model: steam and oxidative reforming of methane over nickel catalyst

In this paper, we have used a thermodynamic model for the first time to investigate the steam and oxidative reforming of methane over a nickel catalyst in a wide temperature range, i.e., 400–1200 K. The available literature focus on the kinetic models and hence, thermodynamic models require attention to understand the behaviour of the thermochemistry of the species involved in the mechanism. This study presents the comparison between the species concentration produced using the thermodynamic model against the available kinetic model to validate the results. The investigation is further extended, firstly, to perform the sensitivity analysis of the reactions involved in a thermodynamic model to figure out the most influential reactions at various temperatures and pressures. This allows us to compare the most influencing reactions in reforming process for kinetic and thermodynamic model to optimize the processes. Secondly, the reaction flow analysis is carried out for the thermodynamic model to comprehend the effect of the thermochemistry of the species and the major difference in the reaction pathways for both the models are noted.

Green hydrogen Production from the oxidative reform of clean biogas over Ni/MgO-Nb2O5 catalysts

Synthesis gas has a variety of applications ranging from its transformation into Fischer-Tropsch fuels, its processing to produce pure hydrogen, and even its direct combustion to generate energy, among many other applications. The objective of this work was the conversion of a model of biogas (clean biogas) into synthesis gas, H2 /CO, through oxidative reforming of methane over NiO/MgO/Nb2O5 catalysts. The catalysts in this work were prepared by impregnation and calcination (at 750ºC) and subsequently characterized by Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Nitrogen Adsorption-Desorption (BET method) and Temperature Programmed Reduction with H2 (TPR). Finally, these catalysts were tested in the oxidative reform of methane (molar ratio of 1.5CH4:1CO2:0.25O2) at 750 ºC, 100mg of catalyst at a total flow of 110 mL.min-1, and 1 atm (inside the reactor). According to the results, it was verified that the catalyst composed of the NiO/MgO mixture is composed of the NiO-MgO solid solution, whereas the NiO/MgO/Nb2O5 catalysts are also formed by nickel niobate (NiNb2O6). All catalysts showed catalytic activity in the oxidative form of biogas, NiMg, Ni60NbMg, and Ni40NbMg catalysts showed the highest conversion value. The efficiency of the catalysts in the oxidative reforming of biogas improved gradually as the %MgO increased in the NiO/MgO/Nb2O5 system. The characterization of the catalyst after the reaction demonstrated that the carbon formed is of the filamentous type.

Synthesis-Gas Production from Methane over Ni/CeO2 Catalysts Synthesized by Co-Precipitation Method in Different Solvents

Ni/CeO2 catalysts were synthesized by the coprecipitation method in a basic medium, using different solvents: water, methanol, ethanol, and isopropanol (Ni content, 10% wt.). These catalysts were tested in the production of syngas through the oxidative reforming of methane (ORM), and partial oxidation of methane (POM). The results of this research demonstrated that the use of alcohols (methanol, ethanol, and isopropanol) during the preparation of the Ni/CeO2 catalysts by the coprecipitation method, improved their characteristics such as crystallite size (nm), surface area (m2·g−1), and reducibility (measured by H2-TPR) that influenced on their catalytic performance in ORM and POM reactions. The best solvent of this study was isopropanol. The use of alcohols (methanol, ethanol, isopropanol) in the co-precipitation method led to the formation of filamentous carbon on the catalyst after the reactions. The catalyst synthesized in the water proved to be inefficient in the POM and ORM reactions and led to the formation of amorphous carbon after the reactions.

Syngas production with CO2 utilization through the oxidative reforming of methane in a new cermet-carbonate packed-bed membrane reactor

A series of γ-LiAlO2-Ag cermets was studied to be integrated into a packed-bed membrane reactor with potential application in the selective separation of CO2 and O2; and simultaneous syngas production through the coupling of the oxidative CO2 reforming of methane process.The γ-LiAlO2 was chemically synthesized and incorporated into an Ag matrix, in different amounts, by powder metallurgy using ball milling and uniaxial pressing techniques. The obtained cermets exhibit excellent wettability properties against molten carbonates, facilitating their infiltration and forming dense dual-phase membranes with the molten salts. Moreover, the cermet supports show corrosion resistance against the alkaline molten carbonates and superior thermal stability due to the γ-LiAlO2 suppresses the sintering of the metallic phase.The membrane's performance was evaluated in the selective gas separation at high temperatures. The membranes exhibit simultaneous CO2 and O2 permeation with a flux of 0.78 and 0.43 ml·min-1·cm-2, at 850 °C, respectively. Besides, during the oxidative reforming process, the membrane reactor shows conversion of about 100 % of CO2 under the studied separation and reaction conditions. The syngas (H2+CO) production reaches values of 4.94 ml·min-1·cm-2 at 825 °C using a 10 % Ni/CeO2 catalyst.A long-term permeation test was conducted for 225 h, during which the membrane exhibits excellent thermal and chemical stability properties under continuous reaction conditions of syngas production. This fact is attributed to its outstanding chemical inertness against carbonates as well as the observed sinterability properties of the used cermet support.

Oxidative Reforming of Methane over Rh-Containing Zeolites: Active Species and Role of Zeolite Framework

Oxidative Reforming of Methane over Rh-Containing Zeolites: Active Species and Role of Zeolite Framework

Synthesis of NiO/Y2O3/ZrO2 Catalysts Prepared by One-Step Polymerization Method and Their Use in the Syngas Production from Methane

In this work, the production of Syngas (H2/CO) from oxidative reforming of methane (ORM) and partial oxidation of methane (POM) over NiO/Y2O3/ZrO2 catalysts was studied. The nickel concentration was varied (ranging from 0 to 40 wt.%) aiming to optimize the performance in ORM and POM reactions; these reactions were carried out at 750°C and 1 atm for 6 hours. The catalysts were prepared by the one-step polymerization method (OSP) and characterized by different techniques. This method led to production of materials of smaller crystallite size than others of similar composition prepared under other methods; the catalysts presented good nickel dispersion, well-defined crystalline structure, and well-defined geometrical morphology. Additionally, the OSP method was advantageous because it was carried out in a single calcination step. The catalyst containing 20% wt. of nickel (20Ni20YZ sample) showed the highest methane conversion, high selectivity to H2 and CO, low carbon deposition rates, and, curiously, the best geometric morphology. The results of this paper also demonstrated that the nickel concentration in the mixture strongly influenced the morphology of the catalysts; therefore, the morphology also influenced the catalytic performances during the Syngas production reactions.

Sinter-resistant metal nanoparticle catalysts achieved by immobilization within zeolite crystals via seed-directed growth

Supported metal nanoparticle catalysts are widely used in industry but suffer from deactivation resulting from metal sintering and coke deposition at high reaction temperatures. Here, we show an efficient and general strategy for the preparation of supported metal nanoparticle catalysts with very high resistance to sintering by fixing the metal nanoparticles (platinum, palladium, rhodium and silver) with diameters in the range of industrial catalysts (0.8–3.6 nm) within zeolite crystals (metal@zeolite) by means of a controllable seed-directed growth technique. The resulting materials are sinter resistant at 600–700 °C, and the uniform zeolite micropores allow for the diffusion of reactants enabling contact with the metal nanoparticles. The metal@zeolite catalysts exhibit long reaction lifetimes, outperforming conventional supported metal catalysts and commercial catalysts consisting of metal nanoparticles on the surfaces of solid supports during the catalytic conversion of C1 molecules, including the water-gas shift reaction, CO oxidation, oxidative reforming of methane and CO2 hydrogenation. Supported metal nanoparticles are indispensable catalysts in industry, yet they are often subjected to severe sintering. Now, a general method based on metal immobilization within zeolite is reported for the preparation of highly sinter-resistant catalysts for a broad range of industrially relevant processes.

Dry reforming of methane in a tip–tip arc discharge reactor at very high pressure

Over the last two decades there has been growing research interest in the oxidative reforming of methane using carbon dioxide (CO2), with the aim of producing syngas (mixture of H2 and CO) which can be converted to synthetic fuels via the Fischer–Trospch process. Among the different options investigated, non-thermal plasma technology is considered to have a high potential for natural gas to syngas (and higher hydrocarbons) conversion at relatively lower energy consumption and cost. While many studies on plasma dry reforming of methane have been carried out over the years using different non-thermal plasma technologies, almost all these studies have been undertaken at near-atmospheric pressure. The aim of this paper is to study the influence of the pressure on the plasma dry reforming of methane. For this purpose, a tip–tip plasma batch-reactor connected to a high voltage direct current power supply has been used. This reactor has a maximum pressure limit of 20 MPa. All experiments were carried out with a CH4/CO2 reactant gas ratio of 1.8, a current of 350 mA, an interelectrode gap of 0.4 mm, and discharge duration of 60 s. The results presented in this paper show the variation of the concentration of the different obtained products: CO, H2, C2 and C3 hydrocarbons versus the operating pressure. From these results, the selectivity, chemical yield, H2/CO ratios and energy balances have been determined. The results from this study are compared to other plasma dry reforming studies in the literature. The high pressure reactor shows a high potential in terms of energy efficiency despite the low conversion due to the specific energy consumed by the reactant and the small discharge volume. The conversion could possibly be improved by increasing the interelectrode gap, and thus create a larger arc discharge reaction zone.

Hydrogen production from oxidative reforming of methane on Ni/γ-Al2O3 catalysts: Effect of support promotion with La, La–Ce and La–Zr

Ni/Al2O3 catalysts promoted by adding La2O3, La2O3–CeO2 and La2O3–ZrO2 were investigated on oxidative and steam reforming aiming the hydrogen production. The samples were characterized by surface area estimation (BET), XRD, TPR, TPD-H2 and XANES. Analysis of TEM and TPO was performed as complementary characterization for catalysts after reaction. The oxidative steam reforming of methane at temperatures above 500°C reveals that all the promoted catalysts presented better activities than the unpromoted. Below 500°C, the catalysts presented deactivation due to metallic nickel species oxidation and the TEM analysis of Ni/Al and Ni/La–Al catalysts revealed that the lanthanum addition led to a decrease in the Ni species particle size and also to a better active phase dispersion. The results suggest that below 500°C the activity may be related to differences in the metallic area values, although the Ni/La2O3–Al2O3 catalysts have shown a different behavior.

Ni/Al2O3catalysts: effects of the promoters Ce, La and Zr on the methane steam and oxidative reforming reactions

The influence of the promoters CeO2, CeO2–ZrO2 and CeO2–La2O3 on the reactivity of γ-Al2O3 supported nickel catalysts from steam and oxidative reforming of methane was investigated in this study. At temperatures above 500 °C, promoted catalysts showed the best performance in the methane oxidative reforming reaction. The increase in activity can be attributed to the specific catalyst–promoter interactions such as the capacity of CeO2 to store and release oxygen and the influence of La2O3 on the stability of the support. Below 500 °C, the activity of the catalyst may be related more directly to the exposed metal surface area.

Hydrogen production from oxidative reforming of methane on supported nickel catalysts: An experimental and modeling study

Nickel catalysts supported on Al2O3, CeO2/Al2O3, Ce0.5Zr0.5O2/Al2O3, and Ce0.5Zr0.5O2 were investigated for methane oxidative reforming. BET surface area results showed that the catalysts containing alumina presented higher surface area which favored better nickel dispersion. This was confirmed by X-ray diffraction (XRD) data from the reduced samples. XRD analysis of the calcined catalysts also showed the formation of a ceria–zirconia solid solution. In fact, the addition of CeO2 and CeZrO2 to alumina provided higher oxygen storage capacities as observed by CO2 formation during CO-TPD. Temperature Programmed Reduction and Diffuse Reflectance Spectroscopy experiments revealed that samples containing alumina showed higher interaction between metal and support. Samples supported on alumina showed similar methane conversions during oxidative reforming, which could be related to similar nickel dispersions. A literature based kinetic model was used to compare data predicted by this model with the experimental behavior. The model results of methane conversions and composition profiles indicated that high temperatures should be used in order to obtain a maximum in H2 production. The model predicted smaller methane and oxygen conversions, as well as, lower H2 and CO molar fractions than the ones observed experimentally. This happened probably due to the fact that the kinetic expressions used were obtained at lower temperatures, lower conversions and with a different catalyst. Despite these differences, the general behavior was predicted by the model.

Modeling and simulation of circulating fast fluidized bed reactors and circulating fast fluidized bed membrane reactors for production of hydrogen by oxidative reforming of methane

Modeling and simulation of circulating fast fluidized bed reactors (CFFBR) and circulating fast fluidized bed membrane reactors (CFFBMR) for hydrogen production by oxidative reforming of methane are presented in this paper. The results show that the CFFBR suffers from serious problems of hot spot temperatures. The combined effect of the oxygen distribution and the hydrogen membrane in the CFFBMR eliminates the hot spot temperatures and the danger of the reactor thermal runaway and mitigates nicely the temperature along the length of the CFFBMR. The investigation shows that the oxidative reforming of methane in the CFFBMR with oxygen distribution is cost-effective and inexpensive alternative route to the conventional steam reforming of methane processes due to the in situ heat integration of exothermic and endothermic reactions. The key role of the design parameters on the performance of the reactors are recognized through sensitivity analysis. The simulation results indicate that almost complete conversion of methane (99.99%), high exit hydrogen yield of 3.00 and low exit temperature of 569.8 °C are obtained by proper selection of design parameters of the CFFBMR with oxygen distribution. This achievement occurs at low feed temperature of 350.0 °C, which does not have destructive effects on the catalyst, reactor and membrane.

Oxidative reforming of methane on structured Ni-Al2O3/cordierite catalysts

The catalytic properties of Ni/Al2O3 composites supported on ceramic cordierite honeycomb monoliths in oxidative methane reforming are reported. The prereduced catalyst has been tested in a flow reactor using reaction mixtures of the following compositions: in methane oxidation, 2–6% CH4, 2–9% O2, Ar; in carbon dioxide and oxidative carbon dioxide reforming of methane, 2–6% CH4, 6–12% CO2, and 0–4% O2, and Ar. Physicochemical studies include the monitoring of the formation and oxidation of carbon, the strength of the Ni-O bond, and the phase composition of the catalyst. The structured Ni-Al2O3 catalysts are much more productive in the carbon dioxide reforming of methane than conventional granular catalysts. The catalysts performance is made more stable by regulating the acid-base properties of their surface via the introduction of alkali metal (Na, K) oxides to retard the coking of the surface. Rare-earth metal oxides with a low redox potential (La2O3, CeO2) enhance the activity and stability of Ni-Al2O3/cordierite catalysts in the deep and partial oxidation and carbon dioxide reforming of methane. The carbon dioxide reforming of methane on the (NiO + La2O3 + Al2O3)/cordierite catalyst can be intensified by adding oxygen to the gas feed. This reduces the temperature necessary to reach a high methane conversion and does not exert any significant effect on the selectivity with respect to H2.

Novel Preparation of Uniform Heterogeneous Catalysts Derived from Hydrotalcites

Several heterogeneous catalysts were prepared starting from Mg-Al and Zn-Al hydrotalcites (HTs) and evaluated for oxidation, ozonation, dehydrogenation and reforming of hydrocarbons, and the CO shift reaction. All catalysts exhibited unique and excellent activities in these reactions. Fe/Mg/Al oxide catalysts prepared from Mg-Al(Fe) HT exhibited high activity for Baeyer-Villiger oxidation of various ketones and dehydrogenation of ethylbenzene. Ozonation activity of Cu/Mg/Al oxide catalysts similarly prepared from Mg(Cu)-Al HT was enhanced by the 'memory effect,' as reconstituted HT on the catalyst surface adsorbed oxalic acid and assisted in complete oxidation. Ni/Mg(Al)O catalysts prepared from Mg(Ni)-Al HT exhibited high and stable activity in steam reforming and oxidative reforming of methane and propane. Moreover, the activity of the Ni catalysts was improved by doping a trace amounts of noble metals by adopting the 'memory effect.' Use of these catalysts in the production of hydrogen for the PEFCs under daily start-up and shut-down operation showed that the catalysts were self-activated and the active Ni metal particles were self-regenerated during the reaction, resulting in high and sustainable activity. CO shift activity of Cu/Zn(Al)O catalysts was also improved by doping a trace Pt or Mg by adopting the memory effect of Zn(Cu)-Al HT in the precursor, resulting in the high sustainability.

Effective additives of Ni/α-Al2O3 catalyst at low methane conversion of oxidative reforming for syngas formation

Abstract Oxidative reforming of methane was conducted at 650 ° C, 1 MPa, and GHSV= 2,000,000 N ml/(g h) using Ni/ α -Al2O3 catalyst. Dilution of catalyst bed with α -Al2O3 prevented the formation of hot-spots in the catalyst bed. Element X ( X = B , P, Ca, Mn, Fe, Cd, Ce, Gd and Re) was added to Ni/ α -Al2O3, and the catalyst activities were experimentally observed to obtain training data of an artificial neural network (ANN). Then the physicochemical properties of element X and the observed values (CH4 conversion, H2 selectivity, or CO selectivity) of Ni–X/ α -Al2O3 catalyst were used for ANN training. After the training, the ANN was able to predict the catalytic performance of Ni–Z/ α -Al2O3 based on the physicochemical properties of element Z where Z is a possible additive other than X. In addition to La and Ce, Sc and Nd were predicted to promote the activity of Ni/ α -Al2O3. The experimentally observed activity of Ni–Sc/ α -Al2O3 was five times higher than that of unpromoted Ni/ α -Al2O3 catalyst.

Preparation of supported metal catalysts starting from hydrotalcites as the precursors and their improvements by adopting “memory effect”

Hydrotalcite-like compounds (HTlcs) can be used as the catalysts as it is since they contain various transition metal cations as the catalytically active species well dispersed on the basic support materials. Moreover, increasing numbers of the applications of HTlcs after the heat treatment have been found since the oxides with very small crystal size, stable to thermal treatments, are obtained after the calcination. The oxides possess interesting properties such as high surface area, basic properties and further form small and thermally stable metal crystallites by reduction. Moreover, the calcined oxides show a unique property, i.e., “memory effect,” which allows the reconstitution of the original hydrotalcite structure. We have developed the catalytic applications of hydrotalcites as it is and moreover the mixed oxides derived from hydrotalcites for various catalytic reactions, i.e., oxidation, dehydrogenation and reforming of hydrocarbons, and even for the reforming of methanol and the CO shift reaction. Aerobic oxidation of alcohols, Baeyer−Villiger oxidation of ketones and O3 oxidation of oxalic acid have been successfully carried out with the Mg−Al hydrotalcites containing Ni, Fe and Cu, respectively, as the catalysts in liquid phase. In the O3 oxidation of oxalic acid, the catalytic activity was enhanced by the “memory effect,” i.e., Mg(Cu)–Al hydrotaclite was reconstituted on the surface of Mg(Cu,Al)O periclase particles and oxalic acid was incorporated as anions in the hydrotalcite layer, resulting in an enhanced oxidation of oxalic acid. As the catalysts in the vapor phase reactions, Mg/Fe/Al mixed oxides prepared from Mg–Al(Fe) hydrotalcites and effectively catalyzed the dehydrogenation of ethylbenzene. Supported Ni metal catalysts have been prepared from Mg(Ni)–Al hydrotalcites and successfully used in the steam reforming and the oxidative reforming of methane and propane. Moreover, the Ni catalysts have been improved by combining a trace amount of noble metals by adopting the “memory effect” and used in the production of hydrogen for the PEFC under the daily startup and shutdown operation. Also starting from aurichalcite or hydrotalcite precursor as the precursor, Cu/Zn/Al catalysts with high Cu metal surface area have been prepared and successfully applied in the steam reforming of methanol and dimethyl ether, and moreover in the CO shift reaction.

Feeding of Oxygen Along the Height of a Circulating Fast Fluidized Bed Membrane Reactor for Efficient Production of Hydrogen

The coupling of steam and oxidative reforming of methane has been studied in a circulating fast fluidized bed membrane reactor (CFFBMR). The concept of oxygen distribution has been investigated by employing discrete injection points along the length of the reformer. The addition of oxygen is to supply the necessary heat required by the endothermic reforming reactions from oxidative reforming reactions. An external air membrane separation system is suggested to supply pure oxygen. A mathematical model is used for a systematic simulation in order to investigate the performance of the CFFBMR. Simulation results show that the staging distribution of oxygen and removal of hydrogen by the permselective membrane play an important role in the significant shift of the thermodynamic equilibrium and substantial enhancement of hydrogen yield. It has been shown that the discrete distribution of oxygen has a potential to eliminate the thermal runaway by mitigating the temperature along the length of the CFFBMR. The results indicate that the coupling of endothermic steam reforming and exothermic oxidative reforming reactions allows efficient energy integration without external supply of energy. The exit hydrogen yield shows a maximum value at which the oxygen to methane feed ratio (O/M) is optimal. The locus of maximum exit hydrogen yield is chosen for the sensitivity analysis. The influence of various reformer key parameters is investigated.

Surface modification of Ni catalysts with trace Pd and Rh for oxidative steam reforming of methane

Abstract Bimetallic catalysts (Pd–Ni and Rh–Ni) were prepared by co-impregnation and sequential impregnation methods to investigate catalytic performance in oxidative steam reforming of methane. These bimetallic catalysts gave high methane conversion even at low W / F such as 0.07 g h/mol. The thermographical observation clearly demonstrated that the catalyst bed temperature was strongly dependent on the preparation method. The bimetallic catalyst prepared from the sequential impregnation method exhibited much higher resistance to hot-spot formation in oxidative reforming of methane. In particular, Pd–Ni catalysts prepared by the sequential impregnation method showed higher resistance to hot-spot formation than monometallic Pd and Ni catalysts, and this can be a synergetic effect of Pd and Ni. Temperature-programmed reduction (TPR) with H 2 revealed that the addition of Pd or Rh by a sequential impregnation method greatly promoted the reduction of Ni species. Extended X-ray absorption fine structure (EXAFS) analysis confirmed the formation of Pd–Ni alloy and the preferential location of Pd atoms on the surface of the bimetallic particles over the Pd/Ni catalysts. Surface modification of Ni with Pd by sequential impregnation is effective for promotion of the activity and suppression of hot-spot formation.

Temperature profile of catalyst bed during oxidative steam reforming of methane over Pt-Ni bimetallic catalysts

The catalyst bed temperature during oxidative reforming of methane (CH 4/H 2O/O 2/Ar = 40/30/20/10) at 1123 K and atmospheric pressure was investigated by infrared thermography over γ-Al 2O 3 supported bimetallic Pt-Ni catalysts prepared by different impregnation methods: co-impregnation and sequential impregnation. The thermographical results clearly demonstrated that the catalyst bed temperature was strongly dependent on the preparation method. The bimetallic catalyst prepared from the sequential impregnation method exhibited much higher resistance to hot spot formation in oxidative reforming of methane. Temperature programmed reduction (TPR) with H 2 revealed that the addition of Pt by a sequential impregnation method greatly promoted the reduction of Ni species; furthermore, infrared spectra of CO adsorption suggests that the surface composition of Pt on the catalyst prepared by the sequential method is much higher than that for the catalyst prepared by the co-impregnation method. The surface enrichment of Pt is responsible for the effective overlap between the combustion and reforming zones, and this can enhance the inhibition of hot spot formation.

Promoting Effect of Pt on Self-activation over NiO–MgO Solid Solution in Oxidative Steam Reforming of Methane

The addition of Pt on NiO-MgO solid solution enhanced the performance of oxidative steam reforming of methane, especially, the catalyst can be activated during the oxidative reforming of methane at low reaction temperature like 823 K 0 1 % Pt/ Ni 02 Mg 08 O exhibited much higher performance than 0.1% Pt/MgO and Ni 02 Mg 08 O From the comparisons, the additive effect of Pt to Ni 02 Mg 08 O is to promote both the activity of combustion and reforming of methane. This additive effect can be explained by the high combustion activity caused by the synergy of Pt with NiO-MgO solid solution and the high catalyst reducibility.