Partial Oxidation Of Dimethyl Ether Research Articles

Using Kriging surrogate model to analyze hydrogen generation with dimethyl ether in partial oxidation catalytic fluidized bed reactor

The study aimed to present a fluidized bed reactor filled with 50% platinum catalytic beads and 50% quartz sand for syngas generation via the partial oxidation of dimethyl ether (DME). For obtaining useful information, experiments were carried out using Taguchi orthogonal array method, which cut test run by 75.3%, with the results being used for constructing the Kriging surrogate model. The model was then modified to reduce the mean square error. It is validated that the model can predict the results reasonably well. The outcome shows that the proposed reactor can self-sustain the syngas reforming reaction without incurring extra heat for reactants preheating. In the operation region, the results show that the start-up temperature is most negligible in hydrogen generation. The yield rate of hydrogen increases in sync with the increase of oxygen's molar ratio and DME, thanks to higher reaction temperature. The results also suggest that the higher the molar ratio of oxygen and DME, the more significant the reverse water shift reaction. Playing a key role in the fluidized bed in the proposed reactor for hydrogen generation, the normalized velocity must be at a proper level, in order to induce bubbling fluidization without causing a lower hydrogen yield, the latter due to the short residence time of reaction caused by excessive velocity. The sensitive analysis of independent variables also proved the inference from the measured results. By comparing with the literature, the performance of the proposed reactor in the present study shows a reasonably well performance. Given focused hydrogen generation, the study's findings can be used as a basis for evaluating DME as a hydrogen carrier and the proposed fluidized bed reaction.

Influence of Oxidative Properties of CexZr1−xO2 Catalyst on Partial Oxidation of Dimethyl Ether

Partial oxidation of dimethyl ether (DME) to hydrogen is an efficient route for hydrogen production for application in SOFC. However, quite a large amount of CO2 as a byproduct has been an important obstacle. In this work, cerium–zirconium solid solution (CexZr1−xO2) was applied to determine how the oxidative properties of the catalyst affect the production of CO2 in the partial oxidation of DME. The results show that the catalyst with more adsorbed oxygen (Oads) rather than the lattice oxygen has stronger oxidizability and gives higher DME conversion as well as higher CO2 yield, due to the overoxidation of CO.

Standalone micro-reformer for on-demand hydrogen production from dimethyl ether

Entering a new era of sustainable energy generation and consumption, micro-fuel cells are showing great potential for providing high energy density to consumer electronics, and micro-reactor technology can indeed enable their integration by providing hydrogen on-demand from hydrocarbons. In this work, we present the design and fully scalable wafer-level fabrication of a MEMS-based catalytic micro-reactor tested in real-life operating conditions by means of a 3D printed ceramic housing. The device consists of an array of thousands of vertically aligned micro-channels, 500 μm in length and 50 μm in diameter, for an overall superficial area per unit volume of 120 cm2 cm−3 and it embeds a thin-film heater for efficient reaction start-up. For the first time, functionalization of the micro-reactor is entirely achieved by atomic layer deposition (ALD) and rapid thermal processing (RTP), resulting in the uniform coating of a Pt/Al2O3 heterogeneous catalyst hereby tested for steam reforming (SR) and partial oxidation (POX) of dimethyl ether (DME). Here, conversion rates up to 74% and hydrogen selectivity of ~60% are obtained by steam reforming at 650 °C, while a specific volumetric hydrogen production of 4.5 mLH2 mL−1DME cm−3REACTOR at 600 °C is obtained from DME POX.

Partial oxidation of dimethyl ether by air into synthesis gas over Pt- and Rh/Ce0.75Zr0.25O2–δ catalysts

Dimethyl ether partial oxidation (DME PO) by air was studied over composite oxide Ce0.75Zr0.25O2 supported Pt and Rh catalysts at temperatures 300–650 °C under atmospheric pressure, WHSV = 10 L·gcat−1·h−1 and DME/O2 molar ratio of 2. The BET, XRD, TEM and TPO techniques were used for catalyst characterization. Thermodynamic equilibrium product distribution of DME PO was calculated and used as reference data for interpreting the experimental results. Both catalysts demonstrated stable performance and coking resistance at DME PO. At 650 °C the catalysts provided complete conversion of DME and О2 into a gas mixture of composition close to the thermodynamic equilibrium one. Synthesis gas productivity was >10 L·gcat−1·h−1, its concentration in the outlet gas mixture exceeded 50 vol % that is quite suitable for solid oxide fuel cell feeding applications.

Syngas production via partial oxidation of dimethyl ether over Rh/Ce0.75Zr0.25O2 catalyst and its application for SOFC feeding

Dimethyl ether (DME) partial oxidation (PO) was studied over 1 wt% Rh/Ce0.75Zr0.25O2 catalyst at temperatures 300–700 °C, O2:C molar ratio of 0.25 and GHSV 10000 h−1. The catalyst was active and stable under reaction conditions. Complete conversion of DME was reached at 500 °C, but equilibrium product distribution was observed only at T ≥ 650 °C. High concentration of CH4 and low contents of CO and H2 were observed at 500–625 °C 75 cm3 of composite catalyst 0.24 wt% Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl showed excellent catalytic performance in DME PO at O2:C molar ratio of 0.29 and inlet temperature 840 °C which corresponded to carbon-free region. 100% DME conversion was reached at GHSV of 45,000 h−1. The produced syngas contained (vol. %): 33.4 H2, 34.8 N2, 22.7 CO, 3.6 CO2 and 1.6 CH4. Composite catalyst demonstrated the specific syngas productivity (based on CO and H2) in DME PO of 42.8 m3·Lcat−1·h−1 (STP) and the syngas productivity of more than 3 m3·h−1 (STP) that was sufficient for 3 kWe SOFC feeding. PO of natural gas and liquified petroleum gas can be carried out over the same catalyst with similar productivity, realizing the concept of multifuel hydrogen generation. The syngas composition obtained via DME PO was shown to be sufficient for YSZ-based SOFC feeding.

Low temperature partial oxidation of dimethyl ether to hydrogen-rich gas over CuO-CeO2/γ-Al2O3 catalysts for fuel cell feeding

The promise of СuO-CeO2/γ-Al2O3 catalysts for partial oxidation of dimethyl ether (DME) to hydrogen-rich gas for fuel cell feeding was demonstrated. The catalysts provided complete conversion of DME to hydrogen-rich gas with low (≤ 0,8 vol.%) CH4 content and Н2 productivity ~3,1 l/(gcat · h) at 350 °C under ambient pressure using a reaction mixture (molar ratio): DME : O2 : N2 = 1 : 1 : 4 (DME : air = 1 : 5) at a flow rate 7 l/(gcat · h).

Low-Temperature Partial Oxidation of Dimethyl Ether to Hydrogen-Rich Gas over CuO–CeO2/γ-Al2O3 Catalysts for Fuel Cell Supply

Low-Temperature Partial Oxidation of Dimethyl Ether to Hydrogen-Rich Gas over CuO–CeO2/γ-Al2O3 Catalysts for Fuel Cell Supply

A microreactor with metallic catalyst support for hydrogen production by partial oxidation of dimethyl ether

A microreactor system with porous metallic catalyst support was prepared and its catalytic efficiency and long term stability were compared with those of a conventional pack bed reactor using partial oxidation of DME for production of hydrogen. The microreactor system had a thin layer of γ-Al2O3 on FeCrAl metal foam as catalyst support. The pack bed reactor had γ-Al2O3 balls densely packed in a quartz tube. With enough catalyst materials (0.5wt% Rh), both of the reactors showed good hydrogen yield higher than 90% at reaction temperature up to 750°C. However, with decreasing Rh content, the pack bed reactor showed deteriorating reaction efficiency while the microreactor maintained the efficiency. In the end, in order to maintain similar reaction efficiency for long term hydrogen production, 10 times more Rh content was necessary for the pack bed reactor than that needed for the microreactor. The pack bed reactor maintained hydrogen production only up to about 120h, while the microreactor maintained hydrogen production up to 1200h, 10 times longer than that of pack bed reactors. This comparison shows superior reaction efficiency and stability of metallic support loaded microreactors over conventional ceramic support loaded pack bed reactors for exothermic and high temperature reactions.

Experimental assessment of a plasma-catalyst hybrid reformer for hydrogen production via partial oxidation of dimethyl ether

In this work, hydrogen is produced from partial oxidation reforming of dimethyl ether (DME) by a plasma-catalyst hybrid reformer under atmospheric pressure. The plasma-catalyst hybrid reformer which includes both plasma and catalyst reactors is designed. A spark discharge is used as a non-equilibrium plasma source, and it is used to ionize the mixture of DME and air. The performances of the reformer are characterized experimentally in terms of gas concentrations, hydrogen yield, DME conversion ratio, and specific energy consumption. The effects of discharge frequency, reaction temperature, air-to-DME ratio and space velocity are investigated. The experimental results show that the plasma-catalyst hybrid reformer enhances hydrogen yield when reaction temperature drops below 620 °C. At 450 °C, hydrogen yield of hybrid reforming is almost three times that of catalyst reforming. When space velocity is 510 h−1, hydrogen yield is 67.7%, and specific energy consumption is 12.2 kJ/L-H2.

Hydrogen production from partial oxidation of dimethyl ether by plasma-catalyst reforming

Hydrogen was produced from partial oxidation reforming of DME (dimethyl ether) by spark discharge plasma at atmospheric pressure. A plasma-catalyst reformer was designed. A series of experiments were carried out to investigate its performance of hydrogen-rich gas production. The effects of reaction temperature, catalyst and flow rate on gas concentrations (volume fraction), hydrogen yield, DME conversion ratio, specific energy consumption and thermal efficiency were investigated, respectively. The experimental results show that hydrogen concentration and the flow rate of produced H2 are improved when temperature increases from 300 °C to 700 °C. Hydrogen yield, hydrogen concentration and the flow rate of produced H2 are substantially improved in the use of Fe-based catalyst at high temperature. Moreover, hydrogen yield and thermal efficiency are improved and change slightly when flow rate increases. When catalyst is 12 g, and flow rate increases from 35 mL/min to 210 mL/min, hydrogen yield decreases from 66.4% to 57.7%, and thermal efficiency decreases from 35.6% to 30.9%. It is anticipated that the results would serve as a good guideline to the application of hydrogen generation from hydrocarbon fuels by plasma reforming onboard.

Mechanism Reduction of Hydrogen Production from Dimethyl Ether Partial Oxidation by Plasma Reforming

Chemical reaction kinetic model of hydrogen production from DME partial oxidation by plasma reforming was found. Mole fractions of main products of DME partial oxidation by spark plasma as the function of inlet gas flow rate were calculated at atmospheric pressure and ambient temperature. Comparing the results of calculation and experiment, the model was proved to be correct. The mechanism research was done by the method of sensitivity analysis and rate of production. The reduced mechanism which includes 16 species and 13 radical reactions was done. The calculation results of reduced mechanism and detailed mechanism were close. The result shows that the reduced mechanism can be used in chemical reaction kinetic calculation of hydrogen production from DME partial oxidation by spark plasma reforming.

Hydrogen production from partial oxidation of dimethyl ether by spark discharge plasma

Experiments involving hydrogen production from dimethyl ether (DME) were performed with a multistage plasma converter at atmospheric pressure. The results of these experiments show that the DME conversion and H 2 yield initially increase and then decrease with the pulse duty ratio increasing. The maximal values of the DME conversion and H 2 yield are 87.6% and 39.4% at a pulse duty ratio of 80%, respectively. As the increase in voltage of the electric source, the conversion and H 2 yield increase significantly, since both the spark energy and the resident time of a spark in chamber are enhanced. When the heat preservation configuration or reactant is employed, the DME conversion and the H 2 yield are enhanced, while the energy consumption is much lower than standard situation at each discharge frequency and the thermal efficiency is enhanced. Owing to insufficient oxygen, the carbon deposit is formed on the electrodes. With the increase in the A/D ratio, the carbon deposit on both the electrodes is clearly reduced.

Partial Oxidation of Dimethyl Ether Using the Structured Catalyst Rh/Al<SUB>2</SUB>O<SUB>3</SUB>/Al Prepared Through the Anodic Oxidation of Aluminum

The partial oxidation of dimethyl ether (DME) was investigated using the structured catalyst Rh/Al2O3/Al. The porous Al2O3 layer was synthesized on the aluminum plate through anodic oxidation in an oxalic-acid solution. It was observed that about 20 nm nanopores were well developed in the Al2O3 layer. The thickness of Al2O3 layer can be adjusted by controlling the anodizing time and current density. After pore-widening and hot-water treatment, the Al2O3/Al plate was calcined at 500 degrees C for 3 h. The obtained delta-Al2O3 had a specific surface area of 160 m2/g, making it fit to be used as a catalyst support. A microchannel reactor was designed and fabricated to evaluate the catalytic activity of Rh/Al2O3/Al in the partial oxidation of DME. The structured catalyst showed an 86% maximum hydrogen yield at 450 degrees C. On the other hand, the maximum syngas yield by a pack-bed-type catalyst could be attained by using a more than fivefold Rh amount compared to that used in the structured Rh/Al2O3/Al catalyst.

Reducing the operation temperature of a solid oxide fuel cell using a conventional nickel-based cermet anode on dimethyl ether fuel through internal partial oxidation

Dimethyl ether (DME)-oxygen mixture as the fuel of an anode-supported SOFC with a conventional nickel-cermet anode for operating at reduced temperatures is systematically investigated. The results of the catalytic tests indicate that sintered Ni-YSZ has high activity for DME partial oxidation, and DME conversion exceeds 90% at temperatures higher than 700 °C. Maximum methane selectivity is reached at 700 °C. Cell performance is observed between 600 and 800 °C. Peak power densities of approximately 400 and 1400 mW cm −2 at 600 and 800 °C, respectively, are reached for the cell operating on DME-O 2 mixture. These values are comparable to those obtained using hydrogen as a fuel, and cell performance is reasonably stable at 700 °C for a test period of 340 min. SEM results demonstrate that the cell maintains good geometric integrity without any delimitation of respective layer after the stability test, and EDX results show that carbon deposition occurrs only at the outer surface of the anode. O 2-TPO analysis shows that carbon deposition over the Ni-YSZ operating on DME is greatly suppressed in the presence of oxygen. Internal partial oxidation may be a practical way to achieve high cell performance at intermediate-temperatures for SOFCs operating on DME fuel.

Onboard hydrogen production from partial oxidation of dimethyl ether by spark discharge plasma reforming

A spark discharge plasmatron was designed. Hydrogen was produced through partial oxidation reforming of DME by spark discharge plasma at atmospheric pressure and ambient temperature. The effects of voltage of electric source, arc frequency, air-to-DME ratio (by mole), DME feed flow rate and arc length on gas concentrations (Vol%), output power of electric source, energy consumption and thermal efficiency were investigated. The experimental results show that when arc frequency is 120 Hz, air-to-DME ratio is 2, DME feed flow rate is 20 mL/min, voltage of electric source is 12 V and arc length is 9 mm, hydrogen concentration is 7%, hydrogen yield is 8.5%, energy consumption is 75.5 kJ/L-H 2 and thermal efficiency is 4.2%. The output power of electric source is different at different arc frequency.

Numerical Simulation of Fuel Processor for Fuel Cell Vehicles

In this paper, a two-dimensional mathematical model of a processor for fuel cell vehicles was presented in order to predict the effect of the parameters on the hydrogen content of the processor. The structure of the processor and the operating parameters were taken into account in the model. The complex physical and chemical process in the processor of dimethyl ether partial oxidation was well described by this model. The mathematical model was introduced into the commercial software star-cd, and then numerical simulations were also performed based on this model. In order to accounting for the effect of the processor temperature and volume fraction field, TGrid mesh method and laminar flow model were selected. Experimental verification of the two-dimensional mathematical model was implemented on self-designed equipment. The result indicates that the computed data is in good agreement with the experiment one. Finally, on the basis of the mathematical model, the effect of the parameters on the hydrogen content of the processor were investigated.

Partial oxidation of dimethyl ether to H 2/syngas over supported Pt catalyst

Dimethyl ether (DME) is a non-toxic fuel with high H/C ratio and high volumetric energy density, and could be served as an ideal source of H 2/syngas production for application in solid oxide fuel cells (SOFC). This study presents results of DME partial oxidation over a 1.5 wt% Pt/Ce 0.4Zr 0.6O 2 catalyst under the condition of gas hourly space velocity (GHSV) of 15000-60000 ml/(g·h), molar ratio of O 2/DME of 0.5 and 500-700 °C, and this temperature range was also the operation temperature range for intermediate temperature SOFC. The results indicated that the catalyst showed good activity for the selective partial oxidation of DME to H 2/syngas. Under the working conditions investigated, DME was completely converted. Increase in reaction temperature enhanced the amount of syngas, but lowered the H 2/CO ratio and yield of methane; while increase in reaction GHSV resulted in only slight variation in the distribution of products. The good catalytic activity of Pt supported on Ce 0.4Zr 0.6O 2 for the partial oxidation of DME may be directly associated with the good oxygen storage capacity of the support, which is worth of further investigation to develop materials for application in SOFC.

DFT study on pathways of partial oxidation of DME under cold plasma conditions

Pathways of partial oxidation of dimethyl ether under cold plasma conditions have been studied by density functional theory method in this work. Total energies, energy barriers and reaction enthalpies at 0 K or 298.15 K have been calculated at GGA/PW91/DNP level. The calculation shows that, with the presence of O 2, the energy barrier of dimethyl ether conversion is reduced and the conversion from dimethyl ether to H 2 and CO is promoted under cold plasma conditions. The formation of syngas is through a multi-step pathway via the conversions of methoxymethyl radical (CH 3OCH 2·), formaldehyde, HCO·, CH 3·, CH 3O·, while the recombination of H generates extra hydrogen. The formation and effect of dimethyl ether anions have been also investigated in this work.

Hydrogen production from partial oxidation of dimethyl ether using corona discharge plasma

Dimethyl ether (DME), with its non-toxic character, high H/C ratio and high-energy volumetric density, is an ideal resource for hydrogen production. This work presents a hydrogen production from partial oxidation of DME using corona discharge plasma performed at ambient conditions. The partial oxidation can avoid the undesired carbon deposit existing in the decomposition of DME and a stable operation has been obtained. The carbon deposit is completely avoided when the O 2/DME ratio is 1.05. Partial oxidation can also greatly improve the conversion rate and energy efficiency. The optimal O 2/DME ratio is 1.38, with which the rate of H 2 production is 1.33 times higher and the energy efficiency is 1.72 times higher than that of DME decomposition. The higher O 2/DME ratio results in complete oxidation and reduces the rate of H 2 production. AC plasma is more efficient than the DC plasma and the optimum frequency is 2 kHz. The order of desired waveform is: sinusoid > sinusoid triangular > square > ramp.

Partial oxidation of dimethyl ether over various supported metal catalysts

Partial oxidation of dimethyl ether (DME) on various metal catalysts was investigated. DME was highly active for oxidation and could be partially oxidized into CO and H 2 at a temperature lower than 600 K on most of the examined supported metal catalysts. The products of partial oxidation of DME depended strongly not only on the metal catalyst but also on the oxide support. Formation of CO, H 2, CH 4, HCHO, CO 2, and H 2O were observed on Al 2O 3-supported catalysts. However, no HCHO was formed on the catalysts supported on SiO 2, MgO, Y 0.16Zr 0.84O 2 (YSZ), Ce 0.85Sm 0.15O 3, and LaGaO 3 based oxide, i.e. La 0.8Sr 0.2Ga 0.8Mg 0.15Co 0.05O 3 (LSGMC). The activity to partial oxidation of DME on catalysts supported on Al 2O 3 increased in the order of Ni>Rh>Co⪢Ru>Fe>Pt⪢Ag. In particular, Ni supported on LaGaO 3 based oxide was active and selective for partial oxidation of DME into synthesis gas. Effects of reaction conditions were further studied on Ni/LSGMC. Selectivity to CO and H 2 increased with decreasing contact time. Therefore, primary products of this reaction are CO and H 2 and the byproduct CH 4 seems to be a secondary product. A small amount of coke was formed on Ni/LSGMC at low reaction temperatures; however, the amount was tiny at high temperatures.