Plasma Reforming Research Articles

(Invited) Plasma Reforming of Liquid Hydrocarbons

Engineering systems that more sustainably use our natural resources is central to both reducing the risks associated with CO2 emissions and making the long-term transition to a more circular, sustainable, and electrified economy. In particular, developing electrically driven technologies to leverage the energy density of liquids to produce clean fuels, e.g., H2, without making CO2, could be game changing. Here, we investigate the potential of directly exciting plasmas in liquid hydrocarbons to create multi-phase reaction environments, i.e., environments where plasma (ionized gas), H2, gaseous and liquid hydrocarbons, and solid carbon are all present simultaneously, to produce H2, unsaturated C2s, and carbon. The ultimate target is direct transformation of liquid hydrocarbons to gaseous H2 and solid, easy-to-separate carbon using electricity that can be provided from any source and/or points of use.This talk will focus on our recent experiments to strike and sustain low and high frequency plasma discharges in liquid hydrocarbon jets to simultaneously generate gaseous H2, C2s, and solid carbon at high rates. Preliminary experiments show that (i) input energy is not wasted in simply vaporizing the liquid - so the system’s specific energy input preferentially drives hydrocarbon cracking; (ii) discharge drive frequency and plasma space time have a big effect on the H2 specific energy requirement (SER) and H2 generation rate, respectively; (iii) feedstock chemistry affects the H2 and C2 products observed; (iv) carbon particulates rapidly form in the liquid hydrocarbon, but they can be separated easily; and (v) the SER for H2 production is 25-30 kWhr/kg, roughly two times less than water electrolysis in practice (60 kWhr/kg). Hydrocarbon conversion, reaction rates, and characterization of the plasma (OES, high speed imaging), gas (MS), liquid (GC/MS), and solid phase (SEM, Raman) products as a function of plasma operating conditions (high and low AC drive frequency; liquid-plasma contact time) and hydrocarbon source will be discussed.

The plasma reforming of methane in rocket engines under multiple working conditions and its effect on ignition delay

The dielectric barrier discharge (DBD) plasma reforming of methane is ideal for fuel upgrading in rocket engine. However, the working conditions such as high flow rate, high pressure, and low temperature in the propellant supply system significantly affect the reforming performance. This research explores the performance of plasma methane reforming under extreme conditions, examining the characteristics of four kinds of structures, with aims to make reasonable engine design and settings based on actual needs. Simulation is conducted to investigate the effect of plasma reforming on methane ignition delay. The results indicate that prolonging the gas residence could promote methane decomposition. The methane conversion rate under Nanosecond pulsed (NP) excitation is 9.6% higher than that under AC excitation, and the energy utilization efficiency is 1.8% higher. However, the carbon deposition of NP excitation is more severe. As the pressure increases, the cracking reaction intensity decreases by 5%. NP excitation has ideal adaptability to high work pressure. Low temperature has little effect on methane plasma conversion but could affect product distribution, promoting the transformation towards H2 and C2H6. The ignition delay could be shortened by 71 ms with C3H8 adding. The results of this study provide theoretical guidance for the ignition improving of the rocket engine.

Factors affecting the economy of green hydrogen production pathways for sustainable development and their challenges.

In a hydrogen economy, the primary energy source for industry, transportation, and power production is hydrogen gas. Green hydrogen can be generated and utilized in an environmentally friendly and sustainable manner; it seeks to displace fossil fuels. Finding a clean alternative energy source is becoming more crucial due to the depletion of fossil fuels and the major environmental pollution issues they bring when utilized extensively. The paper's objective is to analyze the factors affecting the economy of green hydrogen production pathways for sustainable development to decarbonize the world and the associated challenges faced in terms of technological, social, infrastructure, and people's perceptions while adopting green hydrogen. To achieve this, the research looked at a variety of areas relevant to green hydrogen, such as production techniques, industry applications, benefits for society and the environment, and challenges that need to be overcome before the technology is widely used. The most recent methods of producing hydrogen from fossil fuels, such as steam methane, partial oxidation, autothermal, and plasma reforming, as well as renewable energy sources including biomass and thermochemical reactions and water splitting. Grey hydrogen is now the least expensive type of hydrogen, but, in the future, green hydrogen's levelized cost of hydrogen (LCOH) is expected to be less than $2 per kilogram of hydrogen.

Reforming of ammonia and ammonia-air mixtures in a homogenous plasma reactor: Parametric study of hydrogen yields

Plasma-assisted reforming shows great promise for making ammonia compatible with current engine technology, with minimal modifications required. This study examines the impact of various discharge, flow, and composition parameters on ammonia conversion into hydrogen using a new well-stirred homogeneous plasma reactor. Gas chromatography was used to measure hydrogen and oxygen, while ICCD imaging evaluated plasma homogeneity. Initial mixture composition significantly influences the response to plasma conditions. Relative to the initial ammonia composition, the conversion of pure ammonia yields a lower hydrogen percentage when compared to air-diluted mixtures. Introducing air changes the relationship between pulsed energy deposition and hydrogen production, resulting in a more substantial increase in conversion. Efficiency calculations demonstrate that high ammonia content and high pulse frequencies improve yields, while longer residence times in the reactor result in higher temperatures, also increasing yields. These findings provide insights into the underlying mechanisms of ammonia cracking and reforming in a discharge, and will serve to promote further investigation into plasma reforming strategies.

Comparative analysis of methane conversion: pyrolysis, dry and steam thermal plasma reforming

Methane reforming is gaining attention because of its potential to be converted into energy-dense fuels or high-value chemicals. In addition to the production of syngas (H2+CO), the utilization of CO2 can help reduce greenhouse gases. Water steam is typically used to increase the output of H2. This study evaluated the potential of thermal plasma technology to produce clean hydrogen, carbon monoxide, and carbon black from methane by applying a thermodynamic equilibrium model. A comparative analysis of three cases of methane processing (pyrolysis, dry reforming, and steam reforming) is presented to provide a comprehensive understanding of the potential of thermal plasma technology for methane conversion.

(Invited) Utilization of Bio-CO2 and Bio-Methane for Fuel Production: Integration Solid Oxide Electrolyzer, Low Energy Plasma Reformer with Fischer-Tropsch Synthesis

Transition to renewable energy is essential to achieve climate protection objectives. Besides storing electricity for later use, fuel production using renewable energy is an essential part of reducing fossil dependance. Hydrogen production is receiving the greatest attention as a carbon free energy carrier with the potential to fuel future fleets of hydrogen fuel cell vehicles, to store grid electricity to accommodate asynchronous generation and load, and to a lesser extent to displace heating fuels. However, the highest value application in current markets is the production of liquid transportation fuels such as sustainable aviation fuels (SAF) and low (fossil) carbon diesel fuel. However, liquid hydrocarbon fuels only achieve the decarbonization goals if they displace fossil fuels and are produced from sustainable, ideally biogenic carbon resources.Solid oxide electrolysis cell (SOEC) stack developed by OxEon team for MOXIE, the Mars OXygen ISRU Experiment has demonstrated the use of CO2 as an electrolysis feedstock aboard the Perseverance rover which as of this writing has operated thirteen times on Mars, splitting the Mars atmosphere CO2 to carbon monoxide and oxygen, as the first ever demonstration of In Situ Resource Utilization (ISRU) on another planet. The technology is applicable to efficient resource utilization on this world and OxEon is actively developing power to fuels technology to maximize the conversion of biogenic carbon to high value, energy dense, liquid transportation fuels that are needed by an existing vehicle fleet that will be on the road and in the air decades to come.OxEon’s technologies are being applied to bridge the electrical and materials energy sectors. In this project OxEon processes the bio-CO2 through an SOEC and the bio-CH4 through a low energy plasma reformer. The combined synthesis gas is supplied to a Fischer-Tropsch reactor. The combination offers several advantages: the yield of biofuel nearly doubles by use of the bio-CO2 compared to the bio-methane alone, cooling the FT reactor generates all the steam needed in the SOEC system reducing the effective operating voltage (accounting for raising steam) from > 1.5 V/cell to < 1.3 V/cell, oxygen by-product from the SOEC is used in the autothermal reformer, as is some of the FT produced water. The product fuel is all bio-carbon, but it also embodies renewable electric energy in a high-value, storable and transportable liquid hydrocarbon that will be usable in the current air and ground fleets.

(Invited) Utilization of Bio-CO2 and Bio-Methane for Fuel Production: Integration Solid Oxide Electrolyzer, Low Energy Plasma Reformer with Fischer-Tropsch Synthesis

Transition to renewable energy is essential to achieve climate protection objectives. Besides storing electricity for later use, fuel production using renewable energy is an essential part of reducing fossil dependance. The highest value application in current markets is the production of liquid transportation fuels such as sustainable aviation fuels (SAF) from sustainable, ideally biogenic carbon resources. A system is presented for processing anaerobic digester gas for liquid hydrocarbon production. Bio-CO2 is processed through a solid oxide electrolysis cell and bio-CH4through a low energy plasma reformer. The combined synthesis gas is supplied to a Fischer-Tropsch reactor for the production of liquid hydrocarbons. The combination of technologies nearly doubles the yield of biofuel by utilizing the bio-CO2 in addition to the bio-CH4. The product fuel is all bio-carbon but it also embodies renewable electric energy in a high-value, storable and transportable liquid hydrocarbon.

Scale Up and Coupling of the MOXIE Solid Oxide Electrolyzer for Both Terrestrial and Space Applications

The Mars Oxygen ISRU Experiment (MOXIE) is a first of its kind demonstration of in-situ resource utilization technology to produce propellant and breathable oxygen from the Mars ambient carbon dioxide. The use of Lunar and Martian resources represents a significant opportunity to reduce the cost of launch from Earth, enabling propellant production for space refueling, and allowing for life support of manned missions to the Lunar and Martian surfaces.Since developing the Solid OXide Electrolysis (SOXE) stacks for the Mars 2020 MOXIE program in 2017, the OxEon team has made significant advancements in scale and capabilities of the SOXE stack technology used in that system. Newer variants have a five-fold larger cell area and a 6.5-fold increase in cells per stack, for a stack scaled 33-times the 0.5% scale of the device in MOXIE. Six of these OxEon mission-scale SOXE stacks will produce 30 tons of propellant oxygen to fuel a Mars Ascent Vehicle (MAV) in the 19-month window between landing an unfueled MAV pre-supply mission and the next launch opportunity for the first crewed Mars Mission, meeting target requirements for a return mission. OxEon has built and demonstrated systems with mission-scale stacks for both Lunar and Martian applications. A system for the production of propellant H2 and O2 from Lunar ice was successfully tested in a cryo-vac chamber at the Colorado School of Mines in 2022. Another mission-scale demonstration system is scheduled to demonstrate production of O2 and methane from Martian H2O and atmospheric CO2 at Jet Propulsion Laboratory in 2022.In addition to SOXE/SOFC systems, the OxEon technology portfolio also consists of a low energy plasma reformer capable of producing sygnas from a variety of hydrocarbons and a modular-scale Fischer-Tropsch reactor for the production of liquid fuels from syngas. These technologies allow OxEon to provide a wide range of terrestrial energy solutions. A DOE Bioenergy Technologies Office (BETO) funded system is currently being fabricated to demonstrate the conversion of both CO2 and CH4 in anaerobic digester gas to liquid transportation fuels. This will be accomplished using an SOEC system to convert steam and CO2 to synthesis gas. OxEon’s plasma reformer will be used to convert methane to synthesis gas, using the plasma to catalyze the reaction of methane with steam and oxygen, supplied in part by the byproduct oxygen from the electrolysis system. The syngas from the plasma reformer and electrolysis systems are then combined to produce liquid fuels in the Fischer-Tropsch (FT) reactor. Figure 1

Reversible SOFC/SOEC System Development and Demonstration

The OxEon Energy team continues its 30+ year solid oxide fuel cell (SOFC) development history with the design, fabrication, and installation of two reversible solid oxide electrolysis (SOEC)/SOFC demonstration modules (rSOC), at Idaho National Laboratory (INL) and a private, stand-alone microgrid, scheduled for installation and commissioning in early 2023. OxEon’s SOEC/SOFC technology builds on the success of the SOEC stack installed on NASA’s Mars Perseverance Rover that has produced high-purity O2 by electrolyzing Mars atmosphere CO2 nine times to date.OxEon Energy’s technology space integrates cross-sector coupling to produce hydrogen or syngas from SOEC, electricity via SOFC, and transportation fuels from syngas through Fischer-Tropsch synthesis. A low energy plasma reformer provides an alternative approach of producing syngas from low value hydrocarbons. OxEon’s four complementary technologies enable a flexible approach to leveling fluctuating energy from renewables and converting it to accessible, storable, and higher value fuels and chemicals. The reversible SOEC/SOFC systems described in this work demonstrate the opportunity to generate and store H2 fuel as a method to stabilize and capture excess production from renewable or nuclear energy sources.The two demonstration units described in this work integrate OxEon’s reversible SOEC/SOFC stacks with an effective and reliable balance of plant (BOP) system. The high temperature electrolysis (HTE) systems produce hydrogen through electrolysis using solid oxide cell (SOC) technology derived from OxEon’s heritage stack technology and the advancements made during the development of stacks for NASA’s Mars2020 mission.The two demonstration units described in this work use the same modular system design based on 4-stack quad assemblies. The INL system consists of three 4-stack quad assemblies to meet the 30 kW SOEC/ 10 kW SOFC target. OxEon also designed the manifold and plenum assembly to interface with INL’s existing 50 kW test stand and scaled the hot section unit (HSU) to enclose the system. Pressure drop across the system is minimized by supplying even flow to each of the three stack quads, and allows for air delivery in SOFC mode with a blower rather than an air compressor. INL system installation and testing is scheduled for early 2023. A previous 10 kW SOEC system demonstration at INL exceeded project objectives with 14.5 kW system power output, with uniform performance measured from each of 4 stacks.OxEon is scheduled to deliver a 20 kW SOEC/ 10 kW SOFC system to the private microgrid at Stone Edge Farm in early 2023. The system is comprised of 2 quad modules and BOP that will connect with onsite hydrogen storage and renewable energy generation plant. The system will generate hydrogen in SOEC mode using renewable energy supplied by the farm’s solar array. Hydrogen produced in SOEC mode will be compressed and stored by a system designed by HyET Hydrogen B.V. During times of low renewable power generation, the SOFC system will use stored hydrogen to generate power.The Stone Edge Farm system includes two heat exchangers (one for air, one for fuel) that raise the gas feeds to within 50 ⁰C of operating conditions, and minimize pre-heating required for operation. Pre-heating is accomplished with heaters in the HSU enclosure. The feed path is routed to use a portion of the exotherm generated in SOFC mode. The air heat exchanger is oversized for SOEC mode but sized to accommodate the excess flow required for cooling in SOFC mode. The fuel heat exchanger is sized appropriately to deliver H2 in SOFC operation and steam in SOEC operation.Both systems apply mechanical compression to the stacks outside of the HSU enclosure. This design produces greater force than if the springs are enclosed in the hot zone and reduces the insulation envelope size. The end load is applied through a loading rod, an upper load plate, layers of insulation, and an additional outer load plate, placing the springs outside the insulation package that surrounds the hot region where the stacks are located. Low thermal conductivity ceramic rods minimize heat loss through the load transmission path.The materials set used in the rSOC systems uses a scandia-stabilized zirconia electrolyte-supported cell design with nickel-cermet fuel electrode and perovskite air electrodes. Green electrolyte is tape cast, cut, and fired to produce a dense electrolyte of about 250 microns thickness. Electrode inks are applied via screen printing, then fired to form porous electrode layers. Recent advancements in the air side electrode barrier layer, air electrode layers, and fuel electrode catalyst have improved stack performance and stability. Figure 1

Bench-scale NO removal using in-situ fuel-based reductant under rotating arc plasma conditions

Nitrogen oxide (NOx) emissions pose major human health and environmental concerns. Gliding arc plasma is a promising technology for reforming various chemicals. To the best of our knowledge, the application of rotating arc plasma for the reforming of diesel fuel as a reductant coupled to selective catalytic reduction (SCR) on the scale of real-world conditions has not been reported yet. This study aimed to investigate the reduction of NOx using hydrocarbons, as reducing agents, supplied through a rotating arc plasma reformer for SCR. Dodecane (C12H26) was selected as hydrocarbon fuel to represent diesel. The effects of the carbon-to-oxygen ratio and its associated products with ozone addition over different catalyst temperatures from room temperature (22 ± 4 °C) to 300 °C were investigated. After investigating fuel-based reductants, NO was supplied to the bench-scale system as a NOx source. Moreover, NOx removal using plasma-derived hydrocarbon species was investigated using in-situ fourier transform infrared spectroscopy. We found that an optimal carbon-to-oxygen ratio (1.4) was critical for NOx removal. Additionally, up to 95% De-NOx could be achieved as the catalyst temperature increased. Besides, additional ozone injection increased the De-NOx performance at a catalyst temperature <250 °C because of the enhanced oxygenated hydrocarbon species.

Hydrogen-rich syngas generation through microwave plasma reforming of greenhouse gases

This study examined the effectiveness of a 915 MHz atmospheric pressure microwave torch for bulk syngas or hydrogen generation via noncatalytic greenhouse gas (GHG) reforming and its flexibility regarding the amount of soot formed by the process. The investigation shows that plasma-GHG reforming for mass hydrogen generation is feasible without a catalyst at high gas flow rate and microwave power.The best hydrogen production rate and energy yield were 1672 g (H2)/h and 41.8 g (H2)/kWh, respectively, at 160 lpm gas flow rate and 40 kW microwave power at a CH4/CO2 ratio of 1. The conversion rates of CH4 and CO2 under the same conditions were 95.59% and 95.59%, respectively. The plasma reforming method employed in this study shows its excellent potential for industrial application.

Biomass volatiles reforming by integrated pyrolysis and plasma-catalysis system for H2 production: Understanding roles of temperature and catalyst

Biomass utilization is considered a carbon–neutral way to simultaneously tackle the energy crisis and environmental contamination. Challenges still exist to hinder its application, such as low products yield, tar blockage, harsh condition and inferior stability. This paper aims to study whether the newly developed integrated pyrolysis and plasma-catalysis system can be applied into practice of H2 production from real biomass volatiles, and to understand roles of temperature and catalyst. The experiments were performed in a two-stage reactor embedded with a coaxial dielectric barrier discharge plasma zone. Impacts of operating conditions (i.e. discharge power, steam input, heat supply and catalyst packing) on H2 production were investigated. The results show that proper input of discharge power and steam can promote H2 production. Heating supply is recognized as two different effects on plasma-only and plasma-catalysis systems, since reaction temperature elevation acts as inhibitor to plasma characters and cut down the contribution of plasma reforming. After packing bimetallic Ni-Fe/γ-Al2O3 catalyst into plasma, optimal 47.65 mmol/g of H2 can be attained at reforming temperature of 500 ℃, with synergy effects observed. Plasma-catalysis system also outperformed in tar cracking, tar elimination and stability test, attributed to plasma assistance. This work provides an alternative to construct a new plasma-catalysis process for H2 production from biomass volatiles or to couple plasma technology with existing biomass conversion industries for preferable energy and fuel production, highlighting its promising commercialization prospects.

Enhanced hydrogen production by microwave liquid-phase discharge plasma reforming of methanol solution without catalyst

Improved hydrogen production efficiency by microwave liquid-phase discharge plasma reforming of methanol solution without catalyst is investigated in this study. The ethanol solution was added to the methanol solution as accelerator for plasma reforming hydrogen production. The features of radicals and gas-phase products generated by discharge in different mixed solutions were studied by the optical emission spectrum (OES) and gas chromatography (GC). The study found that adding a small amount of ethanol to methanol solution could promote the production of hydrogen by microwave liquid-phase discharge plasma reforming of alcohols. The maximum flow rate of total gas was 30.8 NL/min when discharge in a mixed solution of Seth/meth1:4, which was 11.6% higher than discharge in Smeth1:1.

Mechanism study on gliding arc (GA) plasma reforming: Reaction and energy pathways for H2 production from methanol steam reforming

Aiming on deeply understanding the gliding arc methanol steam reforming (GA-MSR), its reaction mechanism was studied in terms of reaction and energy transfer pathways by combining experiment and plasma kinetics simulation in CH3OH concentration (CME) range of 5%-100%. Via monitoring the consumption and production rates of each species, the roles of species play during GA-MSR are revealed. The important reactive species are identified as H, OH and CH3, which induce the main dehydrogenation pathway of CH3OH→(CH2OH + CH3O) → CH2O → HCO → CO for CH3OH converting to syngas. With the increase of CME, the concentrations of H and CH3 are enhanced, but OH concentration is weakened. The concentration variation trends of the important reactive species regulate that CO2 by-produces at low CME and hydrocarbons do at high CME. In addition, the energy pathways, which are very important but always ignored for plasma reforming, are disclosed advancedly for the energy-strongly coupling GA-MSR. The positive effect of CME on the energy transfer from plasma to chemical energy and the major energy loss pathway of heat loss are uncovered. The energy pathways studies also show why a very high energy efficiency (>80%) could be achieved in GA-MSR, which could be further improved by avoid energy loss from the system.

Reaction mechanism explorations on non-thermal plasma reforming of CO2-CH4 by combining kinetics modeling and emission spectroscopy measurements

Plasma-based dry reforming in an atmospheric dielectric barrier discharge (DBD) reactor has been thoroughly studied by combination of experiments and detailed kinetics simulation. With the assistances of in-situ optical emission spectroscopy (OES) measurements and reaction pathway analysis based on plasma kinetic simulation considering non-constant electric field and thermal effects, this study provided deep insights into the reaction mechanism of plasma-based dry reforming under varied feeding gas composition, gas residence time and operation temperature. A CH4 conversion as high as 44.76 % could be achieved without catalyst at 300 °C, with an SEI of 78 J/cm3 and feeding CH4 ratio of 50 %. Increase of feeding CH4 proportions were found to enhance the generation of C2 and C3 hydrocarbons. Consistently, the OES analysis showed that the relative intensities of spectra bands induced by deexcitation of CH, CO, and C2 also increased monotonically. With the same increment in SEI, increasing gas residence time led to larger promotions in CH4 and CO2 conversion, as being compared to increase of input power. The reason could be explained as that CH4 and CO2 molecules experienced more successive micro-discharges with a longer gas residence time, so more energy would be devoted into CH4/CO2 conversion, whereas more energy was dissipated into heat as rudely increased the discharge power due to the limit of reaction time. CO2 conversion continuously decreased with increasing gas temperature, owing to the recombination of CO and O enhanced at higher gas temperatures. Reaction pathway analysis showed that CH4 conversion was mainly induced by electronic dissociation and ionization at the discharge stage, while CO2 was mainly converted by recombination reaction CO2 + CH2 → CH2O + CO and also electron collision vibrational reaction e + CO2 → e + CO2(vn). The formation of C2 hydrocarbon products was supposed to follow the path of CH4 ↔ CH3/CH → C2H6 ↔ C2H5 ↔ C2H4 → C2H2.

Plasma-catalytic reforming of biogas into syngas over Ni-based bimetallic catalysts

Biogas reforming to syngas is an attractive route for the efficient utilization of biogas. In this work, plasma-catalytic dry reforming of biogas into value-added fuels and chemicals over Ni-based bimetallic catalysts was achieved using dielectric barrier discharge (DBD). The coupling DBD with 10Ni3Co exhibited the best reaction performance, reflected by the highest gas conversion, main gas product yield and selectivity, and fuel production efficiency (FPE). This hybrid process also favored the suppression of carbon deposition on the catalyst surface and the reduction of energy cost for both gas conversion and product formation. The maximum CO2 and CH4 conversion (29.8% and 49.1%) was obtained when the discharge power was 60 W, while a low discharge power (30 W) led to the highest FPE of 12.3%. By using Ni-based catalysts, we were able to tune the product distribution, favoring the generation of C3-C4 hydrocarbons and syngas while reducing the production of C2 hydrocarbons, with 10Ni3Co providing the most favorable results. Compared to other spent catalysts, the lowest carbon deposition (2.9%) was detected on the spent 10Ni3Co after 150 min of plasma reforming. Catalyst characterizations and density functional theory (DFT) calculations showed that the 10Ni3Co catalyst was superior due to a combination of factors such as a higher specific surface area, improved capability to adsorb CO2, strong interactions between the metals and the support, enhanced reducibility and the formation of a Ni-Co alloy. Furthermore, a simplified kinetics model was developed to better understand the effects of Ni-based bimetallic catalysts on the overall energy constant for the conversion of reactants in plasma-catalytic reforming of biogas.

A State-of-The-Art Review on the Latest trends in Hydrogen production, storage, and transportation techniques

The transportation sector is one of the major consumers of fuel i.e., mostly relying on fossil-based fuels. With the rising energy demand and consumption of fossil fuels, the concentration of pollutants and greenhouse gases (GHGs) are increasing in the atmosphere. Hydrogen (H2) is a well-known source of clean energy options and a better alternative to fossil fuels. It has the potential to become a promising fuel for renewable transportation by providing safe, efficient, stable, accessible, and customer-friendly energy. This is due to its many characteristics, such as energy density, high calorific value, affordability, and a wide variety of production methods. H2 has the potential to completely replace the use of fossil fuel in internal combustion engines. The review highlights the recent advances in H2 production, storage, and transportation. Apart from the conventional steam reforming technique i.e., producing around 85% of the world’s grey H2, several clean techniques such as partial oxidation, plasma reforming, water electrolysis, pyrolysis, and photoelectrolysis are comprehensively discussed. Despite its many advantages, H2 storage is a significant issue. Hence, the recent advances and challenges in H2 storage i.e., physical, and material-based techniques have been deliberated. Further, the risks involved during the production, handling, and transportation of H2 fuel is highlighted, and the latest trends in its safety recommendations have been suggested. Finally, the techno-economic feasibility challenges and its outlook has been discussed.

One-step plasma reforming of CO2[sbnd]CH4 into hydrogen and liquid fuels: The roles of Cu and Fe sites on products distribution

Low-carbon plasma-catalysis technology has shown emerging potential for direct conversion of CO2/CH4 into H2 energy and value-added oxygenates at low temperatures. Nevertheless, how to efficiently regulate the distribution of the products and further reveal the catalytic roles of the active sites in plasma-catalysis remains a major challenge. Herein, we exploited 5A zeolite supported catalysts with varied Cu/Fe active sites and further investigated the effects of Ar/H2O additives in this reaction to tune the products distribution. Comprehensive characterization together with the evaluation tests revealed that Cu0 species in Cu/5A was favorable to the formation of CH3OH (18.0%), and Fe2+ in Fe/5A promoted the CH3COOH (7.9%) production. Noted that the addition of Ar greatly enhanced the conversions of CO2 (30.3%) and CH4 (55.6%) and the H2O additive significantly improved the H2 selectivity (56.6%). Upon systemic in-situ DRIFTS and kinetic modelling, the synergistic conversion routes involving the crucial radicals adsorption process over the catalysts surface were proposed. This work provides new insights into the design of highly selective catalysts for tuning the products distribution in the plasma-catalytic co-conversion of CO2/CH4.

Mechanism study on gliding arc (GA) plasma reforming: Unraveling the decisive role of CH4/CO2 ratio in the dry reforming reaction

AbstractAiming at understanding the role of CH4/CO2 ratio on gliding arc (GA)‐based dry reforming of methane (GA‐DRM), the GA‐DRM at CH4/CO2 ratio range of 0.11 to 1 was studied with kinetics simulation. The radicals of H, OH, and CH3 are identified as the main reactive species to induce the reactant conversion and product formation in GA‐DRM. The increase of CH4/CO2 raises the concentrations of H and CH3 and reduces the OH concentration. Subsequently, the CH4/CO2 ratio regulates the main reaction routes of GA‐DRM. The dehydrogenation coupling reaction enhances with CH4/CO2 and thus raises the selectivities of C2 hydrocarbons. The OH‐induced reactions for OH to H2O weaken with CH4/CO2, thereby increasing the H2 selectivity.

Technological solution for distributing vehicular hydrogen using dry plasma reforming of natural gas and biogas

The biggest challenge facing the energy sector today is how to achieve a faster transition from fossil fuel economy to sustainable energy sources. Hydrogen is a clean chemical element that can be associated to high-efficiency fuel cells. However, most industrial H2 production processes are obtained from thermochemical processes that generate large amounts of CO2, such as natural gas (NG) steam reforming and coal gasification. An option to CO2-free H2 production is by water electrolysis based on renewable electricity, however it has technical-economic limitations that make its wide use difficult. This article presents a new plasma reformer as an alternative for H2 production that uses NG with CO2 or biogas as feedstock. Conversions of 90% of NG were experimentally obtained, producing H2, CO and reduced graphene oxide in a single pass through the reactor, without catalysts or heat regeneration. The Energy Conversion Efficiency of the prototype presented values close to 50%, without regard the energy of the carbonaceous nanomaterials obtained and depending on the losses between the power supply and the plasma torch. The proposed technology contributes to the transition from fossil fuel to renewable sources, suggesting the production of H2 in a decentralized way for fuel cell electric vehicles.