Performance of Ba0.5Sr0.5Co0.8Fe0.2O3 + δ membrane after laser ablation for methane conversion

A cross-shaped pattern was formed on the surface of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3 − δ oxygen permeation membrane by laser ablation. A membrane reactor made from this membrane was operated for partial oxidation of methane to syngas in the presence of Ni/ZrO₂ catalyst. The CH₄ conversion and CO selectivity of the membrane reactor were 98.8% and 91.5%, respectively, and the oxygen permeation flux through the membrane was 11.0 ml/cm² min at 850 °C. The effects of space velocity (SV) on CH₄ conversion and CO selectivity in such reactor were discussed. The mechanism of POM in such membrane reactor may follow the combustion and reforming mechanism.     

Hydrogen production from oxidative steam reforming of ethanol in a palladium-silver alloy composite membrane reactor

In this investigation, we studied the oxidative steam reforming reaction of ethanol in a Pd-Ag/PSS membrane reactor for the production of high purity hydrogen. Palladium and silver were deposited on porous stainless steel (PSS) tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. An ethanol-water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2, 0.7 or 1.0) were fed concurrently into the membrane reactor packed with Zn-Cu commercial catalyst (MDC-3). The reaction temperatures were set at 593-723 K and the pressures at 3-10 atm. The hydrogen flux in the permeation side increased proportionately with increasing pressure; however, it reduced slightly when increasing oxygen input. This is probably due to the fast oxidation reaction that consumes hydrogen before the onset of the steam reforming reaction. The effect of oxygen plays a vital role on the ethanol oxidation steam reforming reaction, especially for a Pd-Ag membrane reactor in which a higher flux of hydrogen is required. The selectivity of CO₂ increased with increasing flow rate of oxygen, while the selectivity of CO remained almost the same.     

Partial oxidation of methane to syngas in BaCe0.15Fe0.85O3−δ membrane reactors

Dense planar Ba_0.15Ce_0.85FeO_3−δ (BCF1585) membrane reactors were investigated to produce syngas from methane. Firstly, the membrane itself catalytic activity to methane was investigated using a blank BCF1585 without any catalysts. Then a LiLaNi/γ-Al₂O₃ catalyst was packed on the BCF1585 membrane surface to test the synergetic effects of the membrane and catalyst. It was found that the membrane itself has a poor catalytic activity to methane. The main products are CO₂ and C₂, and methane conversion is low due to the low oxygen permeation flux. However, after the catalyst was packed on the membrane surface, both methane conversion and oxygen permeation flux were greatly improved by the synergetic effect between the membrane and catalyst. Carbon monoxide selectivity reached at 96% with methane conversion of up to 96%. The oxygen permeation flux reached at 3.0 mL/cm² min at 850 °C for a 1.5 mm disk membrane and can effectively be increased by reducing the thickness of the membranes. After operation for 140 h at 850 °C, the used membrane was examined with SEM and EDXS. The results revealed that the decomposition of the membrane materials could not be avoided under such conditions. Oxygen partial pressure gradient across the membranes is suggested as a critical factor to accelerate the kinetic decomposition of the materials.     

Partial oxidation of methane in BaCe0.1Co0.4Fe0.5O3−δ membrane reactor

A new perovskite material, BaCe_0.1Co_0.4Fe_0.5O_3?δ used as dense oxygen permeable membrane for partial oxidation of methane (POM) reaction was investigated. In order to improve the synergetic effects between membrane and catalyst, LiLaNiO/γ-Al₂O₃ catalyst was directly packed onto the surface of the membrane to carry out POM. In BaCe_0.1Co_0.4Fe_0.5O_3?δ membrane reactor, high oxygen permeation flux, high CH₄ conversion and CO selectivity were obtained. At 950 °C, oxygen flux of 9.5 ml cm^?2 min^?1, CH₄ conversion of 99% and CO selectivity of 93% were achieved with a membrane thickness of 1.0 mm. There was an induction process at the initial stage of POM, which was related to the reduction of NiO to Ni⁰ in LiLaNiO/γ-Al₂O₃ catalyst. Experiments illustrated that higher reaction temperature would shorten the induction time. During continuously operating for 1000 h at 875 °C, no degradation of performance of the membrane reaction was observed. SEM characterization also demonstrated that the membrane disc maintained an integral structure without any cracks after long-term operation.     

Partial oxidation of methane in hollow‐fiber membrane reactors based on alkaline‐earth metal‐free CO2‐tolerant oxide

The U‐shaped alkaline‐earth metal‐free CO₂‐stable oxide hollow‐fiber membranes based on (Pr_0.9La_0.1)₂(Ni_0.74Cu_0.21Ga_0.05)O_4+δ (PLNCG) are prepared by a phase‐inversion spinning process and applied successfully in the partial oxidation of methane (POM) to syngas. The effects of temperature, CH₄ concentration and flow rate of the feed air on CH₄ conversion, CO selectivity, H₂/CO ratio, and oxygen permeation flux through the PLNCG hollow‐fiber membrane are investigated in detail. The oxygen permeation flux arrives at approximately 10.5 mL/min cm² and the CO selectivity is higher than 99.5% with a CH₄ conversion of 97.0% and a H₂/CO ratio of 1.8 during 140 h steady operation. The spent hollow‐fiber membrane still maintains a dense microstructure and the Ruddlesden‐Popper K₂NiF₄‐type structure, which indicates that the U‐shaped alkaline‐earth metal‐free CO₂‐tolerant PLNCG hollow‐fiber membrane reactor can be steadily operated for POM to syngas with good performance. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3587–3595, 2014     

Improving the POM performance of YBa2Cu3O7−δ membrane reactor by Co doping

The performance of Co doped YBa₂Cu₃O_7−δ (YBCO) membrane reactor have been investigated in a process of the partial oxidation of methane (POM) to syngas. The results shows that doping YBCO membrane with a little Co can enhance its oxygen permeation flux and improve its stability in reducing atmosphere noticeably. At 900 °C, with feed flow at 50 ml/min, CH₄ 6.0 v%, SV = 12,000 h⁻¹, and Ni/ZrO₂ catalyst, CH₄ conversion rate, CO selectivity, and oxygen permeation flux can reach to 98%, 92% and 1.41 ml min⁻¹ cm⁻² respectively.     

Synthesis gas production in methane conversion using the P|yttria-stabilized zirconia|Ag electrochemical membrane system

The electrochemical membrane reactor of YSZ (yttria-stabilized zirconia) solid electrolyte coated with Pd and Ag as anode and cathode, respectively, has been applied to the partial oxidation of methane to synthesis gas (CO + H₂). The Pd|YSZ|Ag catalytic system has shown a remarkable activity for CO production at 773 K, and the selectivity to CO was quite high (96.3%) under oxygen pumping condition at 5 mA. The H₂ production strongly depended on the oxidation state of the Pd anode surface. Namely, the H₂ treatment of the Pd anode at 773 K for 1 h drastically reduced the rate of H₂ production, while air treatment enhanced the H₂ production rate. From the results of the partial oxidation of CH₄ with molecular oxygen, it is considered that the reaction site of the electrochemical oxidation of CH₄ to synthesis gas was the Pd–YSZ–gas-phase boundary (triple-phase boundary). In addition, it is found that the oxygen species pumped electrochemically over the Pd surface demonstrated similar activity to adsorbed oxygen over Pd, PdO_ad, for the selective oxidation of CH₄ to CO, when the Pd supported on YSZ was used as a fixed-bed catalyst for CH₄ oxidation with the adsorbed oxygen. The difference with respect to the H₂ formation between the electrochemical membrane system and the fixed-bed catalyst reactor results from differences in the average particle size of Pd and the way of the oxygen supply to the Pd surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

钙钛矿型混合导体透氧膜SrFe0.6Cu0.3Ti0.1O3－δ的制备与表征

Dense membrane with the composition of SrFe0.6Cu0.3Ti0.1O3-δ （SFCTO） was prepared by solid state reaction method. Oxygen permeation flux through this membrane was investigated at operating temperature ranging from 750℃ to 950℃ and different oxygen partial pressure. XRD measurements indicated that the compound was able to form single-phased perovskite structure in which part of Fe was replaced by Cu and Ti. The oxygen desorption and the reducibility of SFCTO powder were characterized by thermogravimetric analysis and temperature programmed reduction analysis, respectively. It was found that SFCTO had good structure stability under low oxygen pressure at high temperature. The addition of Ti increased the reduction temperature of Cu and Fe. Performance tests showed that the oxygen permeation flux through a 1.5 mm thick SFCTO membrane was 0.35-0.96 ml·min ^-1·cm^-2 under air/helium oxygen partial pressure gradient with activation energy of 53.2 kJ·mol^-1. The methane conversion of 85%, CO selectivity of 90% and comparatively higher oxygen permeation flux of 5 ml·min^-1·cm^- 2 were achieved at 850℃, when a SFCTO membrane reactor loaded with Ni-Ce/Al2O3 catalyst was applied for the partial oxidation of methane to syngas.     

Hydrogen separation by dense cermet membranes

Novel cermet (i.e. ceramic-metal composite) membranes have been developed to separate hydrogen from mixed gases, particularly product streams generated during coal gasification and/or methane reforming. Hydrogen separation with these membranes is non-galvanic, i.e. it does not use electrodes or an external power supply to drive the separation, and hydrogen selectivity is nearly 100% because the membranes contain no interconnected porosity. The hydrogen permeation rate has been measured as a function of temperature (500-900 °C), membrane thickness (≈22-210 μm), and partial pressure of hydrogen (0.04-1.0 atm) in the feed gas. The hydrogen flux varied linearly with the inverse of membrane thickness, and reached ≈20 cm³(STP)/min cm² for a membrane with a thickness of ≈22 μm at 900 °C with 100% H₂ (at ambient pressure) as the feed gas. The results indicate that the hydrogen flux is limited by bulk diffusion and might be higher for a thinner (<22 μm) membrane. Some of the membranes were tested in a simulated syngas mixture containing H₂, CO, CO₂, and CH₄, and showed no degradation in performance. Hydrogen flux measurements made in H₂S-containing atmospheres for times approaching ≈270 h showed that a 200-μm-thick cermet membrane was stable in gases containing up to ≈400 ppm H₂S. While longer-term studies are needed, these results suggest that the cermet membranes may be suitable for practical hydrogen separation applications.     

Fluidised bed membrane reactor for ultrapure hydrogen production via methane steam reforming: Experimental demonstration and model validation

Hydrogen is emerging as a future alternative for mobile and stationary energy carriers in addition to its use in chemical and petrochemical applications. A novel multifunctional reactor concept has been developed for the production of ultrapure hydrogen from light hydrocarbons such as methane for online use in downstream polymer electrolyte membrane fuel cells. A high degree of process intensification can be achieved by integrating perm-selective hydrogen membranes for selective hydrogen removal to shift the methane steam reforming and water-gas-shift equilibriums in the favourable direction and perm-selective oxygen membranes for selective oxygen addition to supply the required reaction energy via partial oxidation of part of the methane feed and enable pure CO₂ capture without costly post-treatment. This can be achieved in a proposed novel multifunctional bi-membrane bi-section fluidised bed reactor [Patil, C.S., van Sint Annaland, M., Kuipers, J.A.M., 2005. Design of a novel autothermal membrane assisted fluidized bed reactor for the production of ultrapure hydrogen from methane. Industrial and Engineering Chemistry Research 44, 9502-9512]. In this paper, an experimental proof of principle for the steam reforming/water-gas-shift section of the proposed novel fluidised bed membrane reactor is presented. A fluidised bed membrane reactor for steam reforming of methane/water-gas-shift on a commercial noble metal-based catalyst has been designed and constructed using 10 H₂ perm-selective Pd membranes for a fuel cell power output in the range of 50-100 W. It has been experimentally demonstrated that by the insertion of the membranes in the fluidised bed, the thermodynamic equilibrium constraints can indeed be overcome, i.e., increased CH₄ conversion, decreased CO selectivity and higher product yield (H₂ produced/CH₄ reacted). Experiments at different superficial gas velocities and also at different temperatures and pressures (carried out in the regime without kinetic limitations) revealed enhanced reactor performance at higher temperatures and pressures (3-4 bar). With a phenomenological two-phase reactor model for the fluidised bed membrane reactor, incorporating a separately developed lumped flux expression for the H₂ permeation rate through the used Pd-based membranes, the measured data from the fluidised bed membrane reactor could be well described, provided that axial gas back-mixing in the membrane-assisted fluidised bed reactor is negligible. This indicates that the membrane reactor behaviour approached that of an ideal isothermal plug flow reactor with maximum H₂ permeation.     

La1−xSrxFeO3−δ perovskites as redox materials for application in a membrane reactor for simultaneous production of pure hydrogen and synthesis gas

This work reports on the preparation and characterization of perovskitic materials with the general formula La_1−xSr_xFeO₃ (x = 0, 0.3, 0.7, 1) for application in a dense mixed conducting membrane reactor process for simultaneous production of synthesis gas and pure hydrogen. Thermogravimetric experiments indicated that the materials are able to loose and uptake reversibly oxygen from their lattice up to 0.2 oxygen atoms per “mole” for SrFeO₃ with x = 1 at 1000 °C. The capability of the prepared powders to convert CH₄ during the reduction step, in order to produce synthesis gas, as well as their capability to dissociate water during the oxidation step, in order to produce hydrogen were evaluated by pulse reaction experiments in a fixed bed pulse reactor. The high sintering temperatures (1100-1300 °C) required for the densification of the membrane materials result in decreased methane conversion and H₂ yields during the reduction step compared to the corresponding values obtained with the perovskite powders calcined at 1000 °C. Addition of small quantities of NiO, by simple mechanical mixing, to the perovskites after their sintering at high temperatures, increases substantially both their methane decomposition reactivity, their selectivity towards CO and H₂ and their water splitting activity. Maximum H₂ yield during the reduction step is achieved with the La_0.7Sr_0.3FeO₃ sample mixed with 5% NiO and is 80% of the theoretically expected H₂, based on complete methane decomposition. In the oxidation - water splitting step, 912 μmol H₂ per gr solid are produced with the La_0.3Sr_0.7FeO₃ sample mixed with 5% NiO. The experimental results of this work can be equally well applied for the “chemical-looping reforming” process since they concern using the lattice oxygen of the perovskite oxides for methane partial oxidation to syngas, in the absence of molecular oxygen, and subsequent oxidation of the solid.     

CO preferential oxidation over Au/MnOx-CeO2 catalysts prepared with ultrasonic assistance: Effect of calcination temperature

The Au/MnO_x-CeO₂ catalysts used for CO preferential oxidation were prepared by deposition-precipitation with ultrasonic assistance. The effect of calcination temperature (150-350 °C) on the structures and catalytic performance of the catalysts was systematically investigated. It is found that the catalyst Au/MnO_x-CeO₂ calcined at 250 °C exhibits the best catalytic performance, giving not only the highest CO conversion of 90.9% but also the highest selectivity of oxygen to CO₂ at 120 °C. The results of XRD, TEM and XPS indicate that this catalyst possesses the smallest particle size, the highest dispersion of Au species and the largest amount of surface adsorbed oxygen species, which are favorable to CO oxidation. The H₂-TPR results reveal that the selectivity of oxygen to CO₂ is mainly determined by the reducibility of Au species in the catalysts. The strong interaction between Au species and the support in Au/MnO_x-CeO₂-250 decreases its capability for H₂ dissociation and oxidation, leading to high selectivity of oxygen to CO₂.     

La0.6Sr0.4Co0.8Ga0.2O3‐δ (LSCG) hollow fiber membrane reactor: Partial oxidation of methane at medium temperature

In this study, La_0.6Sr_0.4Co_0.8Ga_0.2O_3‐δ (LSCG) hollow fiber membrane reactor was integrated with Ni/LaAlO₃‐Al₂O₃ catalyst for the catalytic partial oxidation of methane (POM) reaction. The process was successfully carried out in the medium temperature range (600–800°C) for reaction of blank POM with bare membrane, catalytic POM reaction and swept with H₂:CO gas mixture. For the catalytic POM reaction, enhancement in selectivity to H₂ and CO is obtained between 650–750°C when O₂:CH₄ <1. High CH₄ conversion of 97% is achieved at 750°C with corresponding H₂ and CO selectivity of about 74 and 91%. The oxygen flux of the membranes also increased with the increase in oxygen partial pressure gradient across the membrane. The postreacted membranes were tested via XRD and FESEM‐EDX for their crystallinity and surface morphology. XPS analysis was further used to investigate the O1s, Co 2p and Sr 3d binding energies of the segregated elements from the reducing reaction environment. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3874–3885, 2013     

Carbon dioxide separation and dry reforming of methane for synthesis of syngas by a dual‐phase membrane reactor

High‐temperature CO₂ selective membranes offer potential for use to separate flue gas and produce a warm, pure CO₂ stream as a chemical feedstock. The coupling of separation of CO₂ by a ceramic–carbonate dual‐phase membrane with dry reforming of CH₄ to produce syngas is reported. CO₂ permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO₂–N₂ mixture as the feed and CH₄ as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO₂ permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ‐alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO₂ permeation flux of 0.17 mL min^?1 cm^?2, hydrogen production rate of 0.3 mL min^?1 cm^?2 with a H₂ to CO formation ratio of about 1, and conversion of CO₂ and CH₄, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207–2218, 2013     

Reaction and oxygen permeation studies in Sm0.4Ba0.6Fe0.8Co0.2O3 − δ membrane reactor for partial oxidation of methane to syngas

A disk-type Sm_0.4Ba_0.6Co_0.2Fe_0.8O_3 − δ perovskite-type mixed-conducting membrane was applied to a membrane reactor for the partial oxidation of methane to syngas (CO + H₂). The reaction was carried out using Rh (1 wt%)/MgO catalyst by feeding CH₄ diluted with Ar. While CH₄ conversion increased and CO selectivity slightly decreased with increasing temperature, a high level of CH₄ conversion (90%) and a high selectivity to CO (98%) were observed at 1173 K. The oxygen flux was increased under the conditions for the catalytic partial oxidation of CH₄ compared with that measured when Ar was fed to the permeation side. We investigated the reaction pathways in the membrane reactor using different membrane reactor configurations and different kinds of gas. In the membrane reactor without the catalyst, the oxygen flux was not improved even when CH₄ was fed to the permeation side, whereas the oxygen flux was enhanced when CO or H₂ was fed. It is implied that the oxidation of CO and H₂ with the surface oxygen on the permeation side improves the oxygen flux through the membrane, and that CO₂ and H₂O react with CH₄ by reforming reactions to form syngas.     

Partial Oxidation of Methane to Syngas in a Packed Bed Catalyst Membrane Reactor

The planar membrane reactor configuration was explored for partial oxidation of methane (POM) to syngas. A supported membrane composed of yttria‐stabilized zirconia and La_0.8Sr_0.2Cr_0.5Fe_0.5O_3‐δ was sealed to a stainless holder, and a Ni/Al₂O₃ catalyst bed was placed under the membrane plane with a small slit between them. This reactor configuration would facilitate the POM reaction via oxidation‐reforming mechanism: the oxidation reaction occurring at the membrane surface and the reforming reaction taking place in the catalyst bed. At 800°C and a methane feed rate of 32 mL min^?1, the reactor attained methane throughput conversion over 90%, CO and H₂ selectivity both over 95%, and an equivalent oxygen permeation rate 1.4 mL cm^?2 min^?1. The membrane and catalyst remained intact after the POM testing. The planar membrane reactor configuration explored in this study may lead to the development of a compact reactor for syngas production. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2170–2176, 2016     

Partial oxidation of methane to synthesis gas over corundum supported mixed oxides: One channel studies

Catalytic partial oxidation of methane (POM) over the monolithic catalyst LaNiO_x/CeO₂–ZrO₂/α-Al₂O₃ has been studied. Experiments were conducted with one channel of a monolith at a varied channel length, contact time (1–6 ms) and temperature using the diluted gas mixture (1% CH₄ + 0.5% O₂ in He). At increasing temperature and contact time, CO selectivity rises within the whole temperature range whereas the contact time dependence of H₂/CO ratio varies with the temperature. These results support the POM reaction scheme including primary formation of CO and H₂ followed by their oxidation in the presence of gas-phase O₂. Steam and dry methane reforming reactions occur in the part of monolithic channel where oxygen is absent, thus increasing syngas yield.     

Oxy-CO2 reforming of methane to syngas over CoOx/MgO/SA-5205 catalyst

The oxy-CO₂ methane reforming reaction (OCRM) has been investigated over CoO_x supported on a MgO precoated highly macroporous silica–alumina catalyst carrier (SA-5205) at different reaction temperatures (700–900 °C), O₂/CH₄ ratios (0.3–0.45) and space velocites (20,000–100,000 cc/g/h). The reaction temperature had a profound influence on the OCRM performance over the CoO/MgO/SA-5205 catalyst; the methane conversion, CO₂ conversion and H₂ selectivity increased while the H₂/CO ratio decreased markedly with increasing reaction temperature. While the O₂/CH₄ ratio did not strongly affect the CH₄ and CO₂ conversion and H₂ selectivity, it had an intense influence on the H₂/CO ratio. The CH₄ and CO₂ conversion and the H₂ selectivity decreased while the H₂/CO increased with increasing space velocity. The O₂/CH₄ ratio and the reaction temperature could be used to manipulate the heat of the reaction for the OCRM process. Depending on the O₂/CH₄ ratio and temperature the OCRM process could be operated in a mildly exothermic, thermal neutral or mildly endothermic mode. The OCRM reaction became almost thermoneutral at an OCRM reaction temperature of 850 °C, O₂/CH₄ ratio of 0.45 and space velocity of 46,000 cc/g/h. The CH₄ conversion and H₂ selectivity over the CoO/MgO/SA-5205 catalyst corresponding to thermoneutral conditions were excellent: 95% and 97%, respectively with a H₂/CO ratio of 1.8.     

Role of the surface state of Ni/Al2O3 in partial oxidation of CH4

The effect of gas phase O₂ and reversibly adsorbed oxygen on the decomposition of CH₄ and the surface state of a Ni/Al₂O₃ catalyst during partial oxidation of CH₄ were studied using the transient response technique at atmospheric pressure and 700°C. The results show that, when the catalyst surface is completely oxidized under experimental conditions, only a small amount of CO and H₂ can be produced from non‐selective oxidation of CH₄ by reversibly adsorbed oxygen which is more active in oxidizing CH₄ completely than NiO via the Rideal–Eley mechanism and both the conversions of CH₄ and O₂ and the selectivities to CO and H₂ are very low. Therefore, keeping the catalyst surface in the reduced state is the precondition of high conversion of CH₄ and high selectivities to CO and H₂. The surface state of the catalyst decides the reaction mechanism and plays a very important role in the conversions and selectivities of partial oxidation of CH₄. During partial oxidation of CH₄, no oxygen species but a small amount of carbon exists on the catalyst surface, which is favorable for maintaining the catalyst in the reduced state and the selectivity of CO. The results also indicate that direct oxidation is the main route for partial oxidation of CH₄, and the indirect oxidation mechanism is not able to gain dominance in the reaction under the experimental conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Coupling and reforming of methane by means of low pressure radio-frequency plasmas

Non-oxidative coupling of CH₄/H₂ mixtures was carried out by means of radio frequency (rf) glow discharges for the first time. A central composite design was employed to determine the best experimental conditions for methane transformation into higher hydrocarbons and to fit the experimental data. rf power was the factor showing the highest effect on the results while CH₄/H₂ mole ratio showed the lowest. Conversion was 46.4% at 100 W, 0.07 mbar and CH₄/H₂ mole ratio of 1/2. Selectivity was 56.9% for C₂, 6.9% for C₃, and 36.2% for C₄ hydrocarbons. Least squares fits of quadratic equations yielded approximating functions permitting to predict results of random experiments with errors of about 5%. The same rf system was used for the reforming of methane with CO₂, O₂, and steam plasmas, respectively. The highest oxidation was observed with oxygen whilst steam plasma produced the best results. H₂/CO mole ratio was adjusted by setting specific experimental parameters of the latter. CO₂ free synthesis gas was produced at higher H₂O and CH₄ flow rates, i.e. 0.8 mmol/h and higher power, i.e. 100 W. CO₂ and CO free H₂ was produced at 0.3 and 0.6 mmol/h flow rates of H₂O and CH₄, respectively, and 50 W.