Partial Oxidation Reforming Of Methane Research Articles

NiO/κ-CeZrO4 functional oxygen carriers with Niδ+ and oxygen vacancy synergy for chemical looping partial oxidation reforming of methane

Chemical looping partial oxidation reforming (CLPOR) technology is an economically attractive, sustainable, and environmental-friendly process strategy of CH4 conversion. In this study, NiO-promoted κ-CeZrO4 functional oxygen carriers (OCs) were designed and synthesized for the CLPOR of methane, with excellent lattice oxygen (LO) transmission performance and structural stability, aiming to reduce the energy penalty and temperature required for methane conversion. The crystalline phase, reaction performance, surface properties and reaction mechanism of the OC were systematically analyzed. In-situ CH4-XPS analysis was further carried out to reveal the internal mechanism with NiO/κ-CeZrO4 and the reason for higher CO selectivity at a low temperature. The methane conversion rate (≥ 80%) and syngas selectivity (≥ 93%) can be obtained under the most of reported reaction conditions (over 850 °C). More importantly, a higher methane conversion rate (52–72%) with syngas selectivity (88–92%) was even able to be achieved at a relative low temperature range 700–800 °C. The excellent performance was attributed to the reducing transmission temperature of the LO and a synergetic effect of Niδ+ and the oxygen vacancies (existed on the surface), thereby inhibiting carbon deposition caused by the excessively fast methane cracking rate under high temperature atmosphere.

Hydrogen Production via Partial Oxidation Reforming of Methane with Gliding Arc Discharge Plasma

AbstractHydrogen production from partial oxidation reforming of methane in a gliding arc discharge (GAD) reactor is investigated. The effects of input power, the oxygen‐carbon molar ratio (O/C), and residence time are studied, respectively. Products such as H2, CO, CO2, and C2‐C4 hydrocarbons can be detected in the outlet gas. The experimental result shows that the input power of 36.4 W, the relitively low O/C of 0.705 and the 13.8 s residence time in this system will bring the highest H2 energy yield. Compared to the decomposition of methane, partial oxidation of methane with air can maintain a stable discharge state and no carbon deposition on electrodes is observed during the reaction process. Optical emission spectroscopy (OES) is also employed to characterize this methane‐air plasma. Based on the results of the experiment and OES, a possible mechanism of methane partial oxidation process was proposed, which points out that collisions of high‐energy electrons and excited N2 species (mainly N2(A)) with other species (such as O2, CH4) in the plasma region are two main ways for the activation of this reforming system. Hydrogen is generated principally through the H‐abstraction reaction and the H‐coupling reaction.

Hydrogen Production by Partial Oxidation Reforming of Methane over Ni Catalysts Supported on High and Low Surface Area Alumina and Zirconia

The catalytic activity of the partial oxidation reforming reaction for hydrogen production over 10% Ni supported on high and low surface area alumina and zirconia was investigated. The reforming reactions, under atmospheric pressure, were performed with a feed molar ratio of CH4/O2 = 2.0. The reaction temperature was set to 450–650 °C. The catalytic activity, stability, and carbon formation were determined via TGA, TPO, Raman, and H2 yield. The catalysts were calcined at 600 and 800 °C. The catalysts were prepared via the wet-impregnation method. Various characterizations were conducted using BET, XRD, TPR, TGA, TPD, TPO, and Raman. The highest methane conversion (90%) and hydrogen yield (72%) were obtained at a 650 °C reaction temperature using Ni-Al-H-600, which also showed the highest stability for the ranges of the reaction temperatures investigated. Indeed, the time-on-stream for 7 h of the Ni-Al-H-600 catalyst displayed high activity and a stable profile when the reaction temperature was set to 650 °C.

Catalytically enhanced methane-rich combustion by porous media reactor

Syngas production by the partial oxidation reforming of methane is a promising technology with a simple setup and quick dynamic response, which has great potential for application in small-scale fuel cells and portable power units. In this study, a catalytically enhanced porous media combustor for partial oxidation reforming is designed and tested. In the combustor, fuel-rich combustion in porous media and catalytic partial oxidation are integrated, benefitting from the merits of both technologies. Without external heat source, the combustor is directly ignited with a stoichiometric gas mixture during the cold startup process, and then adjusted to the partial oxidation conditions. Three zones, a preheating zone, an oxidation zone involving exothermic reactions, and a reforming zone involving endothermic reactions, are observed, which significantly affect the temperature profile in the axial direction. Considering both the methane conversion and reforming efficiency, the optimal equivalence ratio range for self-sustained operation is found to be 2.0–2.4. At an equivalence ratio of 2.0, the effect of the gas velocity on the temperature profile and gas composition of products are studied experimentally. At an equivalence ratio of 2.4 and a gas velocity of 0.13 m/s, the reforming efficiencies of the reactor reach 61.5% and 64.8% when 0.5 wt% Pd and 0.5 wt% Rh, respectively, are introduced to the second layer of the porous media. The carbon deposition at different axial positions of the reactor is analyzed, and the results indicate that carbon deposition by methane pyrolysis in the high-temperature oxidation zone is the dominating cause of carbon deposition. A re-ignition process at stoichiometric condition is helpful for the elimination of carbon.

Internal Partial Oxidation Reforming of Butane and Steam Reforming of Ethanol for Anode‐supported Microtubular Solid Oxide Fuel Cells

AbstractInternal partial oxidation reforming of butane and steam reforming of ethanol were investigated using microtubular solid oxide fuel cells (SOFCs) supported on nickel‐gadolinia doped ceria (Ni‐GDC) anodes for portable power sources in emergency situations and for mobilities, such as vehicles, robots and drones. At an oxygen/carbon (O/C) ratio of 1.0, which is a coking condition in the equilibrium, the Ni‐GDC anode deteriorated for 28 h by internal partial oxidation of butane at 650 °C. However, power generation was also impossible after 8 h and 79 h at steam/carbon (S/C) = 1.0 and 1.5, respectively, by internal steam reforming of ethanol despite of no carbon deposition condition in the equilibrium at 650 °C. Power can be generated for more than 100 h at O/C = 1.5 in butane and at S/C = 2.0 in ethanol. For internal partial oxidation reforming of methane and steam reforming of ethanol in SOFCs, the O/C and S/C ratios are significantly important to prevent carbon deposition on the Ni‐GDC anode.

Development of a Portable SOFC System with Internal Partial Oxidation Reforming of Butane and Steam Reforming of Ethanol

Internal partial oxidation reforming of butane and steam reforming of ethanol were investigated using microtubular solid oxide fuel cells (SOFCs) supported on nickel-gadolinia doped ceria (Ni-GDC) anode for portable power sources in an emergency situation and mobilities such as vehicles, robots and drones. At oxygen/carbon (O/C) ratio of 1.0, which is a coking condition in the equilibrium, the Ni-GDC anode deteriorated for 28 h by internal partial oxidation of butane at 650 oC. However, power generation was also impossible after 8 and 79 h at S/C = 1.0 and 1.5, respectively, by internal steam reforming of ethanol in spite of no carbon deposition condition in the equilibrium at 650 oC. Power can be generated over a period of more than 100 h at O/C = 1.5 in butane and at S/C = 2.0 in ethanol. The O/C and S/C ratios are significantly important to prevent carbon deposition on the Ni-GDC anode for internal partial oxidation reforming of methane and steam reforming of ethanol in SOFCs.

Process Modelling, Thermodynamic Analysis and Optimization of Dry Reforming, Partial Oxidation and Auto-Thermal Methane Reforming for Hydrogen and Syngas production

Abstract In this work, process modelling, thermodynamic analysis and optimization of stand-alone dry and partial oxidation reforming of methane as well as, the auto-thermal reforming processes were investigated. Firstly, flowsheet models were developed for both the stand-alone systems and auto-thermal reforming process using ASPEN HYSYS®. Furthermore, thermodynamic studies were conducted for the stand-alone and auto-thermal reforming processes for temperatures range of 200–1000°C and pressure range of 1–3 bar using Gibbs free energy minimization methods which was also performed using ASPEN HYSYS®. The simulation of the auto-thermal reforming process was also performed at 20 bar to mimic industrial process. Process parameters were optimized in the combined reforming process for hydrogen production using desirability function. The simulation results show that 84.60 kg/h, 62.08 kg/h and 154.7 kg/h of syngas were produced from 144 kg/h, 113 kg/h and 211 kg/h of the gas fed into the Gibbs reactor at CH4/CO2/O2 ratio 1:1:1 for the stand-alone dry reforming, partial oxidation reforming and auto-thermal processes respectively. Equilibrium conversion of CH4, CO2, O2 were thermodynamically favoured between 400 and 800°C with highest conversions of 100%, 95.9% and 86.7% for O2, CO2 and CH4 respectively. Highest yield of 99% for H2 and 40% for CO at 800°C was obtained. The optimum conditions for hydrogen production were obtained at CH4/CO2, CH4/O2 ratios of 0.634, 0.454 and temperature of 800°C respectively. The results obtained in this study corroborate experimental studies conducted on auto-thermal reforming of methane for hydrogen and syngas production.

Study of partial oxidation reforming of methane to syngas over self-sustained electrochemical promotion catalyst

A self-sustained electrochemical promotion (SSEP) catalyst is synthesized for partial oxidation reforming (POXR) of CH4 to produce syngas (H2 and CO) at a relatively low temperature ranging from 350 to 650 °C. The SSEP catalyst is comprised of 4 components: microscopic Ni/Cu/CeO2 anode, La0.9Sr0.1MnO3 cathode, copper as electron conductor, and yttria-stabilized-zirconia as oxygen ion conductor, which form microscopic electrochemical cells to enable the self-sustained electrochemical promotion for the POXR process. The SSEP catalyst exhibited much better catalytic performance in POXR of CH4 than a Ni–Cu–CeO2 catalyst and a commercial Pt–CeO2 catalyst. The CH4 conversion over the SSEP catalyst is 29.4% at 350 °C and reaches 100% at 550 °C and the maximum selectivity to H2 is on the level of 90% at 450–650 °C under a GHSV of 42,000 h−1. The mechanism of the SSEP is discussed.

Assessment of ceramic membrane reforming in a solid oxide fuel cell stack

Partial oxidation reforming of methane using a ceramic mixed ionic (oxygen)/electronic conducting dense ceramic membrane within a solid oxide fuel cell (SOFC) stack is potentially attractive as it allows direct operation on methane. We have analysed this process using a simple model of a counter-flow fuel system in which steam and carbon dioxide from the anode channel of the SOFC provide oxygen which passes through the mixed conducting membrane to partially oxidise methane on the other side of the membrane. The model shows that the concept is feasible and that the efficiency is the same as direct methane operation. The model also gives target values for the properties of the membrane. Tracer oxygen diffusion and exchange have been measured in the family of oxides La1−xSrxFe0.8Cr0.2O3−δ under reducing conditions. The data show that these materials have the mass transport characteristics and stability required for this concept.