Reduction Characteristics of Carbon Dioxide Using a Plasmatron

To decompose carbon dioxide, which is a representative greenhouse gas, a 3-phase gliding arc plasmatron device was designed and manufactured to examine the decomposition of CO₂, either alone or in the presence of methane with and without water vapour. The changes in the amount of carbon dioxide feed rate, the methane to carbon dioxide ratio, the steam to carbon dioxide ratio, and the methane to steam ratio were used as the parameters. The carbon dioxide conversion rate, energy decomposition efficiency (EDE), carbon monoxide and hydrogen selectivity, and produced gas concentration were also investigated. The maximum values of the carbon dioxide conversion rate, which is a key indicator of carbon dioxide decomposition, in different cases were compared. The maximum carbon dioxide conversion rate was 12.3 % when pure carbon dioxide was supplied; 34.5 % when methane was injected as a reforming additive; 7.8 % when steam was injected as a reforming additive; and 43 % when methane and steam were injected together. Therefore, this could be explained that the methane-and-steam injection showed the highest carbon dioxide decomposition, showing low EDE as 0.01 L/min W. Furthermore, the plasma produced carbon-black was compared with commercial carbon-black chemicals through Raman spectroscopy, surface area measurement and scanning electron microscopy. It was found that the carbon-black that was produced in this study has the high conductivity and large specific surface area. Our product makes it suitable for special electric materials and secondary battery materials applications.     

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.     

Pressure swing adsorption for CO<Subscript>2</Subscript> capture in Fischer-Tropsch fuels production from biomass

Environmental concerns and oil price rises and dependency promoted strong research in alternative fuel sources and vectors. Fischer-Tropsch products are considered a valid alternative to oil derivatives having the advantage of being able to share current infrastructures. As a renewable source of energy, synthesis gas obtained from biomass gasification presents itself as a sustainable alternative. However, prior to hydrocarbon conversion, the bio-syngas must be conditioned, which includes the removal of carbon dioxide for subsequent sequestration and capture. A pressure swing adsorption cycle was developed for the removal and concentration of CO₂ from the bio-syngas stream. Activated carbon was chosen as adsorbent. The simulation results showed that it was possible to produce a (H₂ + CO) product with a H₂/CO stoichiometric ratio of 2.14 (suitable as feed stream for the Fischer-Tropsch reactor) and a CO₂ product with a purity of 95.18%. A CO₂ recovery of 90.3% was obtained. A power consumption of 3.36 MW was achieved, which represents a reduction of about 28% when compared to a Rectisol process with the same recovery.     

Syngas Production from Propane Using Atmospheric Non-thermal Plasma

Propane steam reforming using a sliding discharge reactor was investigated under atmospheric pressure and low temperature (420 K). Non-thermal plasma steam reforming proceeded efficiently and hydrogen was formed as a main product (H₂ concentration up to 50%). By-products (C₂-hydrocarbons, methane, carbon dioxide) were measured with concentrations lower than 6%. The mean electrical power injected in the discharge is less than 2 kW. The process efficiency is described in terms of propane conversion rate, steam reforming and cracking selectivity, as well as by-products production. Chemical processes modelling based on classical thermodynamic equilibrium reactor is also proposed. Calculated data fit quiet well experimental results and indicate that the improvement of C₃H₈ conversion and then H₂ production can be achieved by increasing the gas fraction through the discharge. By improving the reactor design, the non-thermal plasma has a potential for being an effective way for supplying hydrogen or synthesis gas.     

Carbon Dioxide Destruction with Methane Reforming by a Novel Plasma-Catalytic Converter

A novel plasma-catalyst converter (NPCC) was engineered in applying the carbon capture utilization technology for the destruction of carbon dioxide (CO₂), which is a cause of global warming and is generated from the combustion of fossil fuels. The NPCC has an orifice-type baffle to improve an amount of gas feed with the higher CO₂ destruction for a stationary point sources application . To examine its ability for the CO₂ destruction, the performance analysis was conducted on the effects of methane additive, nozzle injection velocity, total gas feed, and catalyst type. The product gas from the NPCC was combustible components like CO, H₂, CH₄, THCs. The CO₂ destruction and the CH₄ conversion at a 1.29 CH₄/CO₂ ratio were 37 and 47 %, respectively, and the energy decomposition efficiency was 0.0036 L/min W. The nickel oxide catalyst among other catalysts showed the most effectiveness for the CO₂ destruction and CH₄ conversion at a lower temperature. The carbon-black produced without the catalytic bed has carbon nanoparticles with diverse shapes, such as spherical carbon particles and carbon nanotubes; and its high conductivity and specific surface area were suitable for special electronic materials, fuel cells, and nanocomponents.     

Wet Conversion of Methane and Carbon Dioxide in a DBD Reactor

The influence of water on the plasma assisted conversion of methane and carbon dioxide in a dielectric barrier discharge (DBD) plug flow reactor was studied. The plasma at atmospheric pressure was ignited by a power supply at a frequency of 13.56?MHz. Product formation was studied at a power range between 35 and 70?W. The concentrations of the three gases were altered and diluted with helium to 3?%. FTIR spectroscopy and mass spectroscopy were applied to analyze the inlet and the product streams. The main product of this process are hydrogen, carbon monoxide and ethane. Ethene, ethine, methanol and formaldehyde are generated beside the main products in this DBD in lower concentrations. The conversion of methane, the ratio of the synthesis gas components (n(H₂):n(CO)), and the yield of oxygenated hydrocarbons and hydrogen increases by adding water. The total consumed energy reaches lower values for small amounts of water. Additional water does not influence the generated amount of C2 hydrocarbons and of CO, but decreases the carbon dioxide conversion.     

Effect of Electrical Pulse Forms on the CO2 Reforming of Methane Using Atmospheric Dielectric Barrier Discharge

Methane conversion using an electric discharge has been studied for many years. Recently, many research groups have developed high-frequency pulsed plasma reaction for methane conversion to higher hydrocarbons and synthesis gas. CO₂ reforming of methane to synthesis gas has also attracted considerable interest as a method of utilization of the greenhouse gases, CO₂ and CH₄, which occupy most of man-made greenhouse gases. In this study, the influence of pulse form of applied voltage on methane and carbon dioxide conversions and product selectivity has been investigated using a cylindrical type DBD reactor. For this purpose, two kinds of power supply were compared, that is, AC power supply which has a high-frequency sinusoidal wave form, and AC pulse power supply which has modified AC pulse wave form. The conversions of methane and carbon dioxide were enhanced using pulsed plasma. The lower pulse width was more profitable economically.     

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).     

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.     

Research On a Ceramics Membrane Reactor for Natural Gas Conversion

We explore the new concept for a ceramics membrane reactor including the investigation of the nickel-based catalysts for methane conversion into synthesis gas and the exploitation of an oxide ionic and electronic mixed conductor. When Ca_0.8Sr_0.2Ti_1−xFe_xO_3−α exhibiting the ionic and electronic mixed conduction was used as a support material of Ni based catalyst, coke formation over the catalyst under the methane conversion with air or carbon dioxide was strongly depended on the iron (III) ion contents, x. From the relationship between the amount of carbon deposited on the catalyst and the mixed conduction in support oxide materials, it was suggested that the self-migration of lattice oxygen inside the support regulated by the balance between the oxide ionic and electronic conductivities played an important role to prevent from accumulating the deposited carbon over the catalysts. In addition, we demonstrated the methane conversion into synthesis gas at 1173 K with one component ceramics membrane reactor constructed with the same type of perovskite-type oxide for both the catalyst supported and mixed conductor.     

Conversion of Methane and Carbon Dioxide in a DBD Reactor: Influence of Oxygen

A continuous plug flow reactor supported by a dielectric barrier discharge (DBD) is used to study the conversion of methane, carbon dioxide, and oxygen at different compositions. The three studied gases were diluted with helium to 3 % with an overall flow rate of 200 sccm. The 13.56 MHz plasma was ignited at atmospheric pressure. The product stream and the inlet flow were analyzed by a FTIR spectrometer equipped with a White-cell and by a quadrupole mass spectrometer. The DBD reactor generates hydrogen, carbon monoxide, ethane, ethene, acetylene, formaldehyde, and methanol. Additional oxygen in the feed has positive effects on the yield of methanol, formaldehyde and carbon monoxide and reduces the total consumed energy. The hydrogen yield reaches its maximum at medium amounts of oxygen in the inlet flow. The conversion of methane increases to a limiting value of about 35 %. Methane rich feeds increase the yield of hydrogen, ethane and methanol. On the other hand, additional oxygen has a negative influence on the produced amount of C2 hydrocarbons. The conversion of methane and carbon dioxide as well as the yield of synthesis gas components and C2 hydrocarbons increases by changing the plasma power to higher values.     

Carbon Dioxide Reforming of Methane over Ni Catalysts Supported on Al2O3 Modified with La2O3, MgO, and CaO

The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MO_x/Al₂O₃ (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La₂O₃, MgO, and CaO have been found. The addition of promoters to Al₂O₃-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH₄ and CO₂ conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La₂O₃/Al₂O₃ catalyst, the highest CH₄ conversion (96%) and CO₂ conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al₂O₃ catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH₄ conversion (91%) and CO₂ conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al₂O₃ catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH₄ conversion (89%) and CO₂ conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al₂O₃-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al₂O₃ and the basic property of metal oxide to prevent carbon formation.     

用无声放电转化甲烷和二氧化碳同时制备合成气与烃

在低温常压条件下,研究了在无声放电反应器中以A型分子筛为催化剂从甲烷和二氧化碳合成烃和合成气,实现了在无声放电反应器中同时合成烃和合成气。实验在原料气流量200－600ml/min、原料气甲烷和二氧化碳摩尔比1／1－3／1及输入功率100－500W的范围内进行。研究结果表明,低原料气流量有利于甲烷和二氧化碳的转化,而高原料气流量有利于烃的生成;原料气甲烷和二氧化碳摩尔比对制得合成气的H2／CO摩尔比的影响最显著;甲烷和二氧化碳转化率及合成气和烃的产率均随输入功率的增加而提高。而所研究的范围内,当原料气流理为200ml/min、甲烷和二氧化碳摩尔比为1／1、输入功率为500S时,甲烷和二氧化碳转化率达到最高值,分别为64％和39％。以此法制备的合成气的H2／CO摩尔可以在很宽的范围内变化,本研究合成气H2／CO摩尔比的变化范围是0.7-3.1。     

Steam Plasma Methane Reforming for Hydrogen Production

Reactions of methane with water and CO₂ in thermal plasma generated in a special plasma torch with a water-stabilized arc were investigated. Steam plasma with very high enthalpy and low mass flow rate was produced in a dc arc discharge which was in direct contact with water vortex surrounding the arc column. Composition of produced gas, energy balance of the process and its efficiency were determined from measured data. The output H₂/CO ratio could be adjusted by a choice of feed rates of input reactants in the range 1.1–3.4. Depending on experimental conditions the conversion of methane was up to 99.5%, the selectivity of H₂ was up to 99.9%, and minimum energy needed for production of 1 mol of hydrogen was 158 kJ/mol. Effect of conditions on process characteristics was studied. Comparison of measured data with results of theoretical computations confirmed that the reforming process produces gas with composition which is close to the one obtained from the thermodynamic equilibrium calculations. Relations between process enthalpy, composition of produced syngas and process characteristics were determined both theoretically and experimentally.     

Optimization of equilibrium carbon dioxide methane reforming parameters by the Gibbs free energy minimization method

The thermodynamic equilibrium in the carbon dioxide conversion of methane is studied by Gibbs energy minimization. The curves that represent the dependences of the degree of coke formation, the content of methane and carbon dioxide in syngas, and the syngas module on the CO₂/CH₄ mole ratio in the initial mixture and on temperature at various pressures, are plotted. The regions in which the CO₂/CH₄ mole ratio is optimal for carbon dioxide conversion and no coke formation occurs, and which are characterized by a minimal content of methane and carbon dioxide in syngas, are revealed.     

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.     

Catalytic Conversion of Simulated Biogas Mixtures to Synthesis Gas in a Fluidized Bed Reactor Supported by a DBD

The catalytic conversion of methane and carbon dioxide was studied in a fluidized bed reactor supported by a 13.56?Hz driven coaxial DBD-reactor. Palladium or cupper catalyst which are covered on Al₂O₃ particles were used. The goal was to test whether biogas can be used for the production of synthesis gas. The influences of discharge power, catalysts and temperature of the catalyst bed on the product yield were studied. The starting material and product stream was analyzed by quadrupole mass spectrometry and infrared spectroscopy. H₂/CO ratios can be adjusted in a range between 0.65 (without a catalyst) and 1.75 (using a copper catalyst). The process is highly selective for hydrogen production (up to 83%, using a Palladium catalyst). A copper catalyst increases the H₂/CO ratio can from 1.04 to 1.16 and the palladium catalyst from 1.11 to 1.43 by heating the catalyst to a temperature of 250°C.     

Reforming of Carbon Dioxide to Methane and Methanol by Electric Impulse Low-Pressure Discharge with Hydrogen

Basic phenomena of the reduction of carbon dioxide to reusable organic materials including methane and methanol were investigated by using a radio frequency impulse discharge in a low gas pressure range without catalysis. The discharge took place under different discharge parameters such as voltage, gas flow rate, gas-mixing ratio, and gas residence time, where the carbon dioxide was mixed with hydrogen at total gas pressure of 1–10 Torr. Organic materials such as methane and methanol were observed. Carbon monoxide was a major product from carbon dioxide. Methane was the dominant organic species produced by the discharge. The concentration of methane increased with discharge voltage, and its volume fraction attained 10–20% of the products containing carbon that came from carbon dioxide. This fraction was also dependent on the mixing ratio of carbon dioxide and hydrogen. We also observed the formation of methanol, though its fraction was low, a few %, compared with methane.     

Coupling of methane under pulse corona plasma (I)

At normal temperature and pressure, pulse corona plasma was used as a new method for the dehydrogenative coupling of methane in the absence of oxygen. The effects of voltage polarity and input energy on the dehydrogenative coupling of methane were investigated. The parameter “energy efficiency” was introduced to examine the coupling of the input energy and the dehydrogenative coupling of methane. The experimental results show that positive corona gives higher energy efficiency than negative corona. When the positive corona was chosen, C₂ yield per pass was 31.6% and acetylene yield per pass was 30.1% with 44.6% methane conversion at an input energy density of 1788kJ/mol and a pulse repetition frequency of 66Hz. The function of input energy density towards methane conversion may be expressed as a formula of-In(1-X) =k (PIF). In the range of input energy employed, C₂ yield is proportional to input energy density, but energy efficiency drops off with increasing input energy density.     

From Solar Energy to Fuels: Recent Advances in Light‐Driven C1 Chemistry

Catalytic C₁ chemistry based on the activation/conversion of synthesis gas (CO+H₂), methane, carbon dioxide, and methanol offers great potential for the sustainable development of hydrocarbon fuels to replace oil, coal, and natural gas. Traditional thermal catalytic processes used for C₁ transformations require high temperatures and pressures, thereby carrying a significant carbon footprint. In comparison, solar‐driven C₁ catalysis offers a greener and more sustainable pathway for manufacturing fuels and other commodity chemicals, although conversion efficiencies are currently too low to justify industry investment. In this Review, we highlight recent advances and milestones in light‐driven C₁ chemistry, including solar Fischer–Tropsch synthesis, the water‐gas‐shift reaction, CO₂ hydrogenation, as well as methane and methanol conversion reactions. Particular emphasis is placed on the rational design of catalysts, structure–reactivity relationships, as well as reaction mechanisms. Strategies for scaling up solar‐driven C₁ processes are also discussed.