Production of Hydrogen-Rich Syngas from Biogas Reforming with Partial Oxidation Using a Multi-Stage AC Gliding Arc System

The aim of this research work was to evaluate the possibility of upgrading the simulated biogas (70?% CH₄ and 30?% CO₂) for hydrogen-rich syngas production using a multi-stage AC gliding arc system. The results showed that increasing stage number of plasma reactors, applied voltage and electrode gap distance enhanced both CH₄ and CO₂ conversions, in contrast with the increases in feed flow rate and input frequency. The gaseous products were mainly H₂ and CO, with small amounts of C₂H₂, C₂H₄ and C₂H₆. The optimum conditions for hydrogen-rich syngas production using the four-stage AC gliding arc system were a feed flow rate of 150?cm³/min, an input frequency of 300?Hz, an applied voltage of 17?kV and an electrode gap distance of 6?mm. At the minimum power consumption (3.3?×?10^?18?W?s/molecule of biogas converted and 2.8?×?10^?18?W?s/molecule of syngas produced), CH₄ and CO₂ conversions were 21.5 and 5.7?%, respectively, H₂ and CO selectivities were 57.1 and 14.9?%, respectively, and H₂/CO (hydrogen-rich syngas) was 6.9. The combination of the plasma reforming and partial oxidation provided remarkable improvements to the overall process performance, especially in terms of reducing both the power consumption and the carbon formation on the electrode surface but the produced syngas had a much lower H₂/CO ratio, depending on the oxygen/methane feed molar ratio. The best feed molar ratio of O₂-to-CH₄ ratio was found to be 0.3/1, providing the CH₄ conversion of 81.4?%, CO₂ conversion of 49.3?%, O₂ conversion of 92.4?%, H₂ selectivity of 49.5?%, CO selectivity of 49.96?%, and H₂/CO of 1.6.     

Dry Reforming of Methane by DC Spark Discharge with a Rotating Electrode

A novel type of plasma reactor having a rotating electrode is proposed for CO₂ reforming of methane without catalyst at room temperature and atmospheric pressure. Results indicated that employing rotating ground electrode leads to a stable discharge for any period of time. Effects of feed composition, feed flow rate, applied power and electrodes separation on the carbon dioxide and methane conversions as well as the products selectivity were investigated. Increasing CO₂/CH₄ molar ratio in the feed favors the reagents conversion and consequently promotes the formation of hydrogen and carbon monoxide. If the target product is hydrogen, it is proposed to operate the reactor at CO₂/CH₄ = 1 molar ratio and if the target product is carbon monoxide then CO₂/CH₄ = 3 molar ratio is the preferred option for feed composition. This reactor system has advantages of stable operation and high conversion ability. Also, the obtained syngas with flexible molar ratio of H₂ to CO is suitable for vast industrial applications.     

Reforming of CO<Subscript>2</Subscript>-Containing Natural Gas Using an AC Gliding Arc System: Effects of Operational Parameters and Oxygen Addition in Feed

In this research, the reforming of simulated natural gas containing a high CO₂ content under AC non-thermal gliding arc discharge with partial oxidation was conducted at ambient temperature and atmospheric pressure, with specific regards to the concept of the direct utilization of natural gas. This work aimed at investigating the effects of applied voltage and input frequency, as well as the effect of adding oxygen on the reaction performance and discharge stability in the reforming of the simulated natural gas having a CH₄:C₂H₆:C₃H₈:CO₂ molar ratio of 70:5:5:20. The results showed marked increases in both CH₄ conversion and product yield with increasing applied voltage and decreasing input frequency. The selectivities for H₂, C₂H₆, C₂H₄, C₄H₁₀, and CO were observed to be enhanced at a higher applied voltage and at a lower frequency, whereas the selectivity for C₂H₂ showed an opposite trend. The use of oxygen was found to provide a great enhancement of the plasma reforming of the simulated natural gas. For the combined plasma and partial oxidation in the reforming of CO₂-containing natural gas, air was found to be superior to pure oxygen in terms of reactant conversions, product selectivities, and specific energy consumption. The optimum conditions were found to be a hydrocarbons-to-oxygen feed molar ratio of 2/1 using air as an oxygen source, an applied voltage of 17.5 kV, and a frequency of 300 Hz, in providing the highest CH₄ conversion and synthesis gas selectivity, as well as extremely low specific energy consumption. The energy consumption was as low as 2.73 × 10⁻¹⁸ W s (17.02 eV) per molecule of converted reactant and 2.49 × 10⁻¹⁸ W s (16.60 eV) per molecule of produced hydrogen.     

Optimizing the parameters of the steam-carbon dioxide conversion of methane by Gibbs energy minimization

The thermodynamic equilibrium for the steam-carbon dioxide conversion of methane was studied by Gibbs energy minimization. The degree of coke formation, the content of methane and carbon dioxide in the synthesis gas, and the synthesis gas H₂/CO ratio were plotted as functions of the molar ratios of CO₂/CH₄ and H₂O/CH₄ in the initial mixture at different temperatures and pressures. The regions of the optimum CH₄/CO₂/H₂O molar ratios for steam-carbon dioxide conversion were discovered, with no coke formation taking place in these regions. The optimized CH₄/CO₂/H₂O molar fractions characterized by the minimum content of methane and carbon dioxide in the synthesis gas were found for each region.     

Dry Reforming of Methane with Carbon Dioxide Using Pulsed DC Arc Plasma at Atmospheric Pressure

Dry reforming of CH₄ with CO₂ to produce syngas was investigated in a plasma reactor without catalysts at atmospheric pressure. The reactants passed through the plasma zone and reacted in milliseconds with high conversions and selectivity due to the localized high temperature. The results showed that both conversions and selectivity were higher when using a DC arc discharge than using a pulsed DC arc. Increasing the input energy density promoted the conversions of reactants. At an input power of 204 W, the conversions of CO₂ and CH₄ reached 99.3 and 99.6%, respectively, and the selectivity to products was almost 100%, where the molar ratio of CO₂/CH₄ was 1 with the reactants flow rate of 100 ml/min. Very little coke was formed during the course of reaction. Key parameters such as the pulse frequency, the input power and the total feed flow rate were studied to find the optimum operating condition.     

Synthesis Gas Production from CO2-Containing Natural Gas by Combined Steam Reforming and Partial Oxidation in an AC Gliding Arc Discharge

In this study, a technique of combining steam reforming with partial oxidation of CO₂-containing natural gas in a gliding arc discharge plasma was investigated. The effects of several operating parameters including: hydrocarbons (HCs)/O₂ feed molar ratio; input voltage; input frequency; and electrode gap distance; on reactant conversions, product selectivities and yields, and power consumptions were examined. The results showed an increase in either methane (CH₄) conversion or synthesis gas yield with increasing input voltage and electrode gap distance, whereas the opposite trends were observed with increasing HCs/O₂ feed molar ratio and input frequency. The optimum conditions were found at a HCs/O₂ feed molar ratio of 2/1, an input voltage of 14.5?kV, an input frequency of 300?Hz, and an electrode gap distance of 6?mm, providing high CH₄ and O₂ conversions with high synthesis gas selectivity and relatively low power consumptions, as compared with the other processes (sole natural gas reforming, natural gas reforming with steam, and combined natural gas reforming with partial oxidation).     

Effect of Nonthermal Plasma on the Methanation of Carbon Monoxide over Nickel Catalyst

Reduction of carbon monoxide to methane by hydrogen was investigated with a nonthermal plasma reactor in which Ni/alumina catalyst pellets was filled. The effect of reaction temperature, pressure and voltage on the conversion of CO was examined. It was found that the nonthermal plasma significantly enhanced the catalytic conversion of CO. The effect of the nonthermal plasma was especially remarkable at lower temperatures and pressures. At high temperatures, the catalyst itself exhibited very high catalytic activity for the conversion of CO. Since high pressure is unfavorable for creating electrical discharge plasma, the increase in pressure lowered the discharge power, thereby weakening the effect of the nonthermal plasma. With the nonthermal plasma alone, there was no conversion of CO. The reaction products identified by FTIR spectra were CH₄, CO₂ and H₂O. FTIR spectra also showed that CO was converted primarily into CH₄ with high selectivity above 90% at most experimental conditions.     

Syngas production in a novel perovskite membrane reactor with co-feed of CO2

Partial oxidation of methane（POM） co-fed with CO₂ to syngas in a novel catalytic BaCo_0.6Fe_0.2Ta_0.2O_3-δ oxygen permeable membrane reactor was successfully reported.Adding CO₂ to the partial oxidation of methane reaction not only alters the ratio of CO/H₂,but also increases the oxygen permeation flux and CH₄ conversion.Around 96%CH₄ conversion with more than 93%CO₂ conversion and 100%CO selectivity is achieved,which shows an excellent reaction performance.A steady oxygen permeation flux of 15 mL/（cm² min） is obtained during the 100-h operation,which shows good stability as well.     

DC-Pulsed Plasma for Dry Reforming of Methane to Synthesis Gas

The carbon dioxide reforming of methane to synthesis gas under DC-pulsed plasma was investigated. The effects of specific input energy and feed ratio on the product distribution and also feed conversion was studied. At the input energy of about 11 eV/molecule per methane and/or carbon dioxide the feed conversion of 38% for CH₄ and 28% for CO₂ and product selectivity of 74% has been attained for H₂ and CO at feed flow rate of 90 ml/min. The energy consumption in this work displays potential to further study and optimization of the process. The importance of the electron impact reactions in the process was discussed. The results show that by prudent tuning of system variables, the process be able to run in the way of synthesis gas, instead of hydrocarbon production.     

NiCe bimetallic nanoparticles embedded in hexagonal mesoporous silica (HMS) for reverse water gas shift reaction

Reverse water gas shift (RWGS) reaction is a crucial process in CO₂ utilization. Herein, Ni- and NiCe-containing hexagonal mesoporous silica (Ni-HMS and NiCe-HMS) catalysts were synthesized using an in-situ one-pot method and applied for RWGS reaction. At certain reaction temperatures 500-750 °C, Ni-HMS samples displayed a higher selectivity to the preferable CO than that of conventionally impregnated Ni/HMS catalyst. This could be originated from the smaller NiO nanoparticles over Ni-HMS catalyst. NiCe-HMS exhibited higher activity compared to Ni-HMS. The catalysts were characterized by means of TEM, XPS, XRD, H₂-TPR, CO₂-TPD, EPR and N₂ adsorption-desortion technology. It was found that introduction of Ce created high concentration of oxygen vacancies, served as the active site for activating CO₂. Also, this work analyzed the effect of the H₂/CO₂ molar ratio on the best NiCe-HMS. When reaction gas H₂/CO₂ molar ratio was 4 significantly decreased the selectivity to CO at low temperature, but triggered a higher CO₂ conversion which is close to the equilibrium.     

析因设计结合响应面法分析甲烷干重整过程中通过形成碳纳米管进行二氧化碳减排(英文)

A factorial experimental design was combined with response surface methodology(RSM) to opti-mize the catalyzed CO2 consumption by coke deposition and syngas production during the dry re-forming of CH4. The CH4 /CO2 feed ratio and the reaction temperature were chosen as the variables, and the selected responses were CH4 and CO2 conversion, the H2 /CO ratio, and coke deposition. The optimal reaction conditions were found to be a CH4 /CO2 feed ratio of approximately 3 at 700 °C, producing a large quantity of coke and realizing high CO2 conversion. Furthermore, Raman results showed that the CH4 /CO2 ratio and reaction temperature affect the system's response, particularly the characteristics of the coke produced, which indicates the formation of carbon nanotubes and amorphous carbon.     

The oxidative stream reforming of methane to syngas in a thin tubular mixed-conducting membrane reactor

The oxidative stream reforming of methane (OSRM) to syngas, involving coupling of exothermic partial oxidation of methane (POM) and endothermic steam reforming of methane (SRM) processes, was studied in a thin tubular Al₂O₃-doped SrCo_0.8Fe_0.2O_3−δ membrane reactor packed with a Ni/γ-Al₂O₃ catalyst. The influences of the temperature and feed concentration on the membrane reaction performances were investigated in detail. The methane and steam conversions increased with increasing the temperature and high conversions were obtained in 850–900 °C. Different from the POM reaction, in the OSRM reaction the temperature and H₂O/CH₄ profoundly influenced the CO selectivity, H₂/CO and heat of the reaction. The CO selectivity increased with increasing the temperature or decreasing the H₂O/CH₄ ratio in the feed owing to the water gas shift reaction (H₂O + CO → CO₂ + H₂). And the H₂ selectivity based on methane conversion was always 100% because the net steam conversion was greater than zero. The H₂/CO in product could be tuned from 1.9 to 2.8 by adjusting the reaction temperature or H₂O/CH₄. Depending on the temperature or H₂O/CH₄, furthermore, the OSRM process could be performed auto-thermally with idealized reaction condition.     

Application of non-thermal atmospheric pressure ac plasmas to the carbon dioxide reforming of methane

Methane conversions of 11.9%, yields of hydrogen as high as 23.3% and energy yields of 1.0 mol H₂/kWh have been achieved from CO₂ reforming of CH₄ in non-thermal, atmospheric pressure plasma reactors with Pt coated electrodes. Two reactors have been studied. A novel fan type reactor consisting of a movable rotor and immobile stator produced the highest yields in contrast to a tube type (silent discharge) reactor with a glass dielectric barrier. Conversions, yields of hydrogen and energy yields (expressed as mol H₂/kWh) were studied for CO₂/CH₄ concentrations of 1.1% and 5.0% in He as a function of flow rate and input voltage. Hydrogen yields are observed to increase as the input voltage is increased from 411 V to 911 V and the flow rate is decreased from 100 cc/min to 30 cc/min. Energy yields vary only slightly with input voltage and flow rate. Hydrogen yields show little dependence on CO₂/CH₄ concentrations, but energy yields are approximately five times greater for the 5.0% mixture than the 1.1% mixture. Selectivities to H₂, CO, coke, and low molecular weight hydrocarbons were also evaluated and compared to data obtained without CO₂ in the feed. Hydrogen selectivities of nearly 100% were obtained, with small amounts of ethane and propane as the only observed side products and the selectivites were approximately the same whether CO₂ was present or absent in the mixture. However, the reaction proceeds much more cleanly when CO₂ is present, producing CO. The syngas product has an H₂ : CO ratio of 1.5 with the fan type reactor and 0.67 with the tubular reactor. In the absence of CO₂, coke is the main carbonaceous product. Under all conditions studied the fan type reactor demonstrated higher methane conversions (up to 11.9%) and selectivities to hydrogen.     

Influence of Helium on the Conversion of Methane and Carbon dioxide in a Dielectric Barrier Discharge

We have studied the production of synthesis gas and other hydrocarbons in a dielectric barrier discharge using mixtures of helium, methane and carbon dioxide. It was found that helium has a significant influence on the discharge, decreasing the breakdown voltage and increasing the rate of conversion of CH₄ and CO₂. However it also decreases the selectivities and the range of stable operating conditions for the discharge. The main products obtained were H₂, CO, C₂H₆ and C₃H₈ but traces of other hydrocarbon, carbon deposition and the formation of condensable products were also detected. The rate of conversion and conversion abilities were obtained by fitting the conversion results to a model.     

Autothermal reforming of methane to syngas for Fischer-Tropsch synthesis with promoted palladium and a fast start-up device

In this study, a Pd catalyst was prepared with promoters such as CeO₂, BaO and SrO in a washcoated form on a metallic monolith for autothermal reforming of methane to syngas for the Fischer-Tropsch synthesis. A reactor was installed with an electric heater in the form of the metallic monolith as a start-up device instead of a burner with which stable and fast start-ups (within 4 min) were achieved. Gas hourly space velocity and O₂/CH₄ governed, methane conversion, while H₂O/CH₄ controlled H₂/CO ratio. A methane conversion of approx. 96%, H₂+CO selectivity of approx. 85%, and H₂/CO of approx. 2.6 were obtained under the conditions of gas hourly space velocity (GHSV) at 103000 h^?1, O₂/CH₄=0.7 and H₂O/CH₄=0.35.     

Combined Reforming and Partial Oxidation of CO<Subscript>2</Subscript>-Containing Natural Gas Using an AC Multistage Gliding Arc Discharge System: Effect of Stage Number of Plasma Reactors

The effect of stage number of multistage AC gliding arc discharge reactors on the process performance of the combined reforming and partial oxidation of simulated CO₂-containing natural gas having a CH₄:C₂H₆:C₃H₈:CO₂ molar ratio of 70:5:5:20 was investigated. For the experiments with partial oxidation, either pure oxygen or air was used as the oxygen source with a fixed hydrocarbon-to-oxygen molar ratio of 2/1. Without partial oxidation at a constant feed flow rate, all conversions of hydrocarbons, except CO₂, greatly increased with increasing number of stages from 1 to 3; but beyond 3 stages, the reactant conversions remained almost unchanged. However, for a constant residence time, only C₃H₈ conversion gradually increased, whereas the conversions of the other reactants remained almost unchanged. The addition of oxygen was found to significantly enhance the process performance of natural gas reforming. The utilization of air as an oxygen source showed a superior process performance to pure oxygen in terms of reactant conversion and desired product selectivity. The optimum energy consumption of 12.05 × 10²⁴ eV per mole of reactants converted and 9.65 × 10²⁴ eV per mole of hydrogen produced was obtained using air as an oxygen source and 3 stages of plasma reactors at a constant residence time of 4.38 s.     

High-Efficient Conversion of CO<Subscript>2</Subscript> in AC-Pulsed Tornado Gliding Arc Plasma

An AC-pulsed tornado gliding arc plasma was employed for CO₂ conversion via CO₂ decomposition and dry reforming reactions. A stable and high-efficient constant arc length discharge mode was obtained in this plasma reactor. And then, CO₂ conversion was studied under this discharge mode. In the case of CH₄/CO₂ = 0, CO₂ was converted to CO and O₂ via the CO₂ decomposition reaction. Energy efficiency of 29 % was attained at CO₂ conversion of 6 %. With strong reducing agent CH₄ added into CO₂, the main contributor of CO₂ conversion changed from CO₂ decomposition to dry reforming of CH₄. Conversions of CH₄ and CO₂, energy efficiency and energy cost changed sharply at CO₂/CH₄ ratios lower than 1/4, while they changed slowly at CH₄/CO₂ ratios above 1/4. In the case of CH₄/CO₂ = 2/3, energy efficiency of 68 % and syngas energy cost of 1.6 eV/mole were achieved at CH₄ conversion of 29 % and CO₂ conversion of 22 %.     

Gas-chromatographic determination of impurities of organic and chlorinated organic compounds and carbon monoxide and dioxide in high-purity hydrogen chloride

A gas-chromatographic procedure was developed for determining impurities (CH₄, C₂H₆, C₃H₈, C₄H₁₀, iso-C₄H₁₀, C₅H₁₂, iso-C₅H₁₂, neo-C₅H₁₂, CH₃Cl, C₂H₅Cl, CH₂Cl₂, CHCl₃, CO, and CO₂) in hydrogen chloride using two columns and a column switching technique in an isothermal mode with a flame ionization detector; the detection limits were 0.01–0.1 ppm. The matrix was separated in a precolumn packed with urea. CO and CO₂ were determined by reaction gas chromatography with their conversion into methane.     

FeMn、FeMnNa和FeMnK催化剂上合成气制低碳烯烃的比较

研究了钠、钾助剂对FeMn 合成低碳烯烃催化剂结构及性能的影响. 低温N₂吸附、X射线光电子能谱（XPS）、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、CO/CO₂程序升温脱附（CO/CO₂-TPD）、Mössbauer 谱和CO+H₂反应的研究结果表明,增加Mn助剂含量促进了活性相的分散和低碳烯烃的生成,而过多锰助剂在催化剂表面的富集则降低了费托合成反应的CO转化率;钾助剂和钠助剂的加入均抑制了催化剂的还原并且促进了CO₂和CO的吸附. 比较还原后（H₂/CO摩尔比为20）和反应后（H₂/CO摩尔比为3.5）催化剂的体相结构可以发现,在FeMn、FeMnNa和FeMnK催化剂中,由于钾助剂的碱性和CO吸附能力较强,因此体相中FeC_x的含量相对较高;而活性测试结果表明,FeMnNa催化剂拥有最好的CO转化率（96.2%）和低碳烯烃选择性（30.5%,摩尔分数）.     

大气压下甲烷火花放电制乙炔和合成气

用大气压下火花放电方法和发射光谱原位诊断技术, 对CH₄直接转化制乙炔和间接转化制合成气进行了研究, 并与介质阻挡放电进行了比较。结果表明, 火花放电具有能量效率高的突出优点, 能够高效地将CH₄活化成C原子、H原子和C₂等活泼物种。当CH₄单独进料时, 能得到以C₂H₂为主的烃类产物。当CH₄与CO₂和O₂共进料时, 能得到H₂/CO比值可调的合成气产物。在用火花放电转化CH₄和CO₂制合成气时, 添加O₂能够避免反应器的结炭问题, 反应温度只需225 ℃, 与常规催化法相比具有明显的低温优势。