Pyrolysis Of Natural Gas Research Articles

CO2-free production of hydrogen via pyrolysis of natural gas: influence of non-methane hydrocarbons on product composition, methane conversion, hydrogen yield, and carbon capture

Methane pyrolysis represents a CO2-free hydrogen production route that enables simultaneous carbon capture. While the majority of previous studies in the field focus on pure CH4 as feed gas stream, commercial processes will typically rely on natural gas as feedstock that contains also non-methane hydrocarbons such as ethane, propane, and n-butane. Therefore, the present study evaluates how CH4 conversion, H2 selectivity, product composition, and solid carbon yield evolve when using either pure CH4 or synthetic natural gas (SNG) as feed gas stream for a thermal pyrolysis process in a lab-scale high-temperature reactor. For this, industrially viable conditions are applied, namely temperatures between 1000 °C and 1600 °C, residence times between 1 s and 7 s, and molar H2 dilution ratios between 1:1 and 4:1. Although the use of SNG results in slightly lower hydrocarbon conversions because the additional components in SNG result in a higher effective H2 dilution ratio compared to a CH4-only feed, the non-methane hydrocarbons in the SNG have a positive effect on both H2 selectivity and solid carbon yield. Taking existing mechanistic understanding into account, these positive effects are attributed to radicals formed from the non-methane hydrocarbons, which facilitate dehydrogenation steps from ethane to ethylene and hereby increase the relative amount of H2 originating from CH4. The introduction of a carbonaceous fixed bed further benefits the performance of the pyrolysis process and ultimately enables to capture more than 98% of carbon in its solid form under industrially viable process conditions.

CH4 and CO2 Reductions from Methanol Production Using Municipal Solid Waste Gasification with Hydrogen Enhancement

This study evaluates the greenhouse gas (GHG) impacts of converting municipal solid waste (MSW) into methanol, focusing on both landfill methane (CH4) emission avoidance and the provision of cleaner liquid fuels with lower carbon intensity. We conduct a life cycle assessment (LCA) to assess potential GHG reductions from MSW gasification to methanol, enhanced with hydrogen produced via natural gas pyrolysis or water electrolysis. Hydrogen enhancement effectively doubles the methanol yield from a given amount of MSW. Special attention is given to hydrogen production through natural gas pyrolysis due to its potential for lower-cost hydrogen and reduced reliance on renewable electricity compared to electrolytic hydrogen. Our analysis uses a case study of methanol production from an oxygen-fired entrained flow gasifier fed with refuse-derived fuel (RDF) simulated in Aspen HYSYS. The LCA incorporates the significant impact of landfill methane avoidance, particularly when considering the 20-year global warming potential (GWP). Based on the LCA, the process has illustrative net GHG emissions of 183 and 709 kgCO2e/t MeOH using renewable electricity for electrolytic hydrogen and pyrolytic hydrogen, respectively, for the 100-year GWP. The net GHG emissions using 20-year GWP are −1222 and −434 kgCO2e/t MeOH, respectively. Additionally, we analyze the sensitivity of net GHG emissions to varying levels of fugitive methane emissions.

Comparative analysis of methane and natural gas pyrolysis for low-GHG hydrogen production

Methane pyrolysis is emerging as an attractive clean hydrogen production method. As its commercialization proceeds, the pyrolysis of natural gas (NG) becomes pertinent. In this work, the decomposition of pure methane and a realistic NG mixture are compared experimentally and numerically. Methane and NG pyrolysis are performed between 600 and 1200 °C over a fluidized bed of carbon particles heated by microwaves. Experimentally, no conclusive difference is observed in methane conversion between methane and NG pyrolysis. Numerically, the methane conversion rate is 8.5% higher for NG at 950 °C. The difference diminishes past 950 °C, becoming 0 past 1050 °C. The simulations showed that the enhanced methane decomposition in NG pyrolysis is due to an attack on methane by radicals generated during ethane and propane decomposition. The CO2 in our NG mixture decomposes into CO. This work validates the longstanding use of methane pyrolysis as a surrogate for NG pyrolysis.

Investigation of Carbon Products Produced by Catalytic Pyrolysis of Natural Gas

Investigation of Carbon Products Produced by Catalytic Pyrolysis of Natural Gas

Technical Aspects of Natural Gas Pyrolysis in Liquid Metal Bubble Column Reactors

The pyrolysis of low alkanes (in the following short “pyrolysis”) has already been investigated during the 1960s. However, none of the reactor systems used at the time are capable of continuous operation. Therefore, the Karlsruhe Institute of Technology has intensified the development of the promising liquid metal bubble column technology in recent years, which is capable of continuous operation. Various key aspects have been addressed, such as scale‐up and the pyrolysis of high‐caloric natural gas. Herein, further developments for a pilot scale system have been investigated, which concern increased throughput and long‐term operation capabilities. Careful evaluation of the impact of according measures has been done, which shows that the achieved scale‐up has only negligible effects on the pyrolysis outcome. The effects of the scale‐up on residence times are negligible. The bubble formation behavior depends on the throughput and the characteristics of the orifice. Wall effects are marginal. Fundamental minimization of weeping could not be confirmed. Reactor pre‐chambers in combination with tin collection chambers are recommended for further scale‐up. An increase in the volume flow should be examined. In terms of long‐term operation , head as well as feed pressure control is recommended.

Temperature effects on the properties of solid carbon from natural gas pyrolysis in molten tin

Temperature effects on the properties of solid carbon from natural gas pyrolysis in molten tin

Integration assessment of turquoise hydrogen in the European energy sector

Turquoise hydrogen from natural gas pyrolysis has recently emerged as a promising alternative for low-carbon hydrogen production with a high-value pure carbon by-product. However, the implications of this technology on the broader energy system are not well understood at present. To close this literature gap, this study presents an assessment of the integration of natural gas pyrolysis into a simplified European energy system. The energy system model minimizes the cost by optimizing investment and hourly dispatch of a broad range of electricity and fuel production, transmission, and storage technologies, as well as imports/exports on the global market. Norway is included as a major natural gas producer, and Germany as a major energy importer. Results reveal that pyrolysis is economically attractive at modest market shares where the carbon by-product can be sold into high-value markets for 400 €/ton. However, pyrolysis-dominated scenarios that employ methane as a hydrogen carrier also hold promise as they facilitate deep decarbonization without the need for vast expansions of international electricity, hydrogen, and CO2 transmission networks. The simplicity and security benefits of such pyrolysis-led decarbonization pathways justify the modest 11 % cost premium involved for an energy system where natural gas is the only energy trade vector. In conclusion, there is a strong case for turquoise hydrogen in future energy systems and further efforts for commercialization of natural gas pyrolysis are recommended.

Characterization of solid carbon from hydrocarbon pyrolysis in molten aluminum

This study analyzed the synthesized solid carbon from the pyrolysis of methane, ethane, propane, and natural gas using molten aluminum at 1000 °C. Microscopic examination revealed the formation of spherical structures and capped-carbon nanotubes with average primary particle sizes of 0.18–1.29 μm for the spheres and 0.31–0.39 μm for the capped-carbon nanotubes. Methane and ethane pyrolysis generated spherical carbon exclusively, while propane and natural gas pyrolysis produced spheres and capped-carbon nanotubes. The analysis of interlayer spacing indicated the presence of nanocrystalline properties in all carbon samples. X-ray diffraction analysis indicated broad graphitic phases in methane, ethane, and natural gas-derived carbon, and a broad and sharp graphitic carbon peak in propane-derived carbon. Raman spectroscopy confirmed the presence of graphitic structures and disorder, with capped-carbon nanotubes demonstrating more ordered structures than spheres. The thermogravimetric analysis uncovered differences in oxidation behavior, with the mixture of spherical carbon and capped-carbon nanotubes resulting from propane pyrolysis displaying superior thermal stability compared to samples composed solely of spherical carbon. Additionally, the solid carbon samples from the pyrolysis of methane, ethane, and natural gas displayed a final decomposition curve corresponding with commercial carbon black N991. The surface area analysis unveiled that carbon samples derived from ethane and natural gas exhibited surface areas that were 2.4–5.2 times larger than those of commercial carbon black N991 and graphite flakes. These findings underscore the adaptability of tailoring solid carbon materials by selecting the appropriate feed gas to suit specific applications.

Economic analysis of hydrogen production and refueling station via molten-medium-catalyzed pyrolysis of natural gas process

The urgent need for sustainable energy solutions has been underscored by escalating greenhouse gas emissions and the global commitment to net-zero emissions. Clean hydrogen energy, despite its potential for the global low-carbon transition, faces challenges such as high production and transport costs and significant carbon emissions. Herein, we investigate the molten-medium-catalyzed pyrolysis of natural gas (MPN) for hydrogen production and refueling. We highlight the urgent environmental and economic motivations for cleaner energy, specifically addressing the existing challenges faced by traditional hydrogen production methods. Our research introduces an innovative integrated system for onsite hydrogen production, showcasing its economic advantages, carbon emission reduction potential, and compatibility with current infrastructures. The study meticulously evaluates the MPN technology's economic feasibility, including a detailed analysis of cost drivers and the market value of by-product carbon materials. Furthermore, we stress the importance of further research to optimize the technology and promote its adoption for a low-carbon future. This investigation presents MPN as a promising alternative, potentially revolutionizing the hydrogen supply chain and contributing significantly to global decarbonization efforts.

Graphitizable Pitch from Microwave Plasma Pyrolysis of Natural Gas.

An innovative approach of microwave plasma was utilized to convert natural gas into tar, from which a highly graphitizable pitch was derived using fractional distillation. The natural gas-derived pitch (NGDP) was thoroughly characterized, and the graphitizability of the carbonized NGDP was assessed using polarized light microscopy. The NGDP and, for comparison, needle coke, petroleum coke, and shot coke were subjected to graphitization heat treatment (GR) at 2500 °C. Results indicate that the graphitizability of the NGDP exceeds those of all industrial standard cokes. The GR-NGDP showed the highest degree of graphitization and crystallite size among all samples.

Transient analysis of solar pyrolysis and hydrogen yield via interband cascade laser absorption spectroscopy of methane, acetylene, ethylene, and ethane

A mid-infrared laser absorption sensing method has been developed to measure species concentrations of four hydrocarbons and gas temperature over a range of temperatures in mixture compositions relevant to the pyrolytic decomposition of natural gas. The four measured species (methane, acetylene, ethylene, and ethane) are the most abundant hydrocarbons during the pyrolysis of natural gas, and provide a means to monitor decomposition progress and hydrogen yield through molar balance. In this work, time-division multiplexed signals of three distributed-feedback interband cascade lasers are used to make simultaneous measurements of select C-H stretch rovibrational transitions of the target hydrocarbons in the 3.00–3.34 μm range. The sensor was validated over a range of temperatures and pressures (300–1000 K, 0.03–1 atm) at relevant mixture compositions, with correction methods developed to mitigate cross-species interference. The sensor was demonstrated on a solar-thermal pyrolysis reactor, where time-resolved measurements of species mole fractions were performed across a range of insolation conditions to capture the transient response of the reactor.

Technoeconomic assessment of hydrogen production from natural gas pyrolysis in molten bubble column reactors

Natural gas pyrolysis to produce carbon and hydrogen, known as “turquoise hydrogen, using molten metals and salts is a promising route to clean hydrogen production. Methane pyrolysis produces significantly less or near-zero CO2. Additionally, the solid carbon can be separated and sold as a valuable co-product, making industrial-scale production of hydrogen via pyrolysis economically attractive. To better understand the potential of turquoise hydrogen, this study presents a comparative techno-economic assessment of molten media pyrolysis processes in bubble column reactors using Ni0.27Bi0.73, Ga, and KCl–MnCl2 (33:67). The study evaluates techno-economic assessment with a clear understanding of kinetics of natural gas pyrolysis and reactor process modeling. According to the modeling results, Ga had the lowest reactor cost and total bare erected cost. Nevertheless, the pyrolysis process that used inexpensive KCl–MnCl2 molten salt was more economically advantageous. Due to uncertainties in the density separation of solid carbon in the molten salt at temperatures above 1000 °C, Ni0.27Bi0.73 was selected as the promising molten medium for the long term. Sensitivity analyses were carried out to assess the impact of the costs of natural gas, hydrogen, and electricity on the industrial concept. In regions where gas is produced, such as Saudi Arabia, mature molten pyrolysis plants that use grid electricity at a rate of $48/MWh and solar photovoltaic systems with storage at a rate of $24/MWh can be economically feasible at natural gas prices of $132/ton and $198/ton, respectively, even if carbon is not sold. The cost of producing turquoise H2 is comparable to the global average for grey H2 and selling carbon can generate additional revenue or improve the profitability of the plant. The net energy demand of the molten pyrolysis plant is found to be approximately 21% of the energy requirement for current methods of green hydrogen production through PEM (proton exchange membrane) electrolysis.

CHALLENGES FOR THE DEVELOPMENT OF NUMERICAL MODELS FOR METHANE PYROLYSIS WITH LIQUID METAL REACTORS

Methane pyrolysis is a technology that is being postulated as an option within the Hydrogen economy. Pyrolysis allows gaseous hydrocarbons to be processed without directly emitting CO2, as it is carried out in the absence of oxygen, allowing its integration into the circular economy concept by producing two recoverable elements, such as solid carbon and hydrogen. It is currently classified as a form of turquoise hydrogen generation, as it shares characteristics of green hydrogen, as it does not emit carbon dioxide in the process, and blue hydrogen, as its primary resource is natural gas. There are several technological options to carry out the pyrolysis of natural gas, ranging from direct thermolysis, through the use of catalysts, the use of plasma arcs, or the development of hydrocarbon decomposition in liquid reaction media, such as molten salts or liquid metals. This communication will describe the main remains for the development of pyrolysis reactors with liquid metals, which are currently at Technology Readiness Level around TRL4, in order to advance towards industrially viable and competitive prototypes and demonstrators. That development requires creating numerical models that can be used for the engineering design of pyrolysis reactors. The design tools for this case must be capable of coupling multiphase and multicomponent fluid-mechanical evaluation, which takes into account the evolution of a gaseous phase (natural gas) into a liquid phase (liquid metal) with the formation of solids (carbon). The fluid dynamic calculation runs into the lack of experimental data that allow its validation, which becomes a critical aspect to be able to estimate the chemical kinetics of the reaction itself. This kinetics strongly depends on the residence time of the gas in the medium, and on the temperature. In this communication, those relations between the fluid-mechanical and chemical model that would allow the evaluation of the conversion of natural gas to hydrogen and carbon in the design of the reactor are analyzed. As a result, a series of experiments are proposed to validate these design tools for the pyrolysis process in liquid metal. Keywords: Decarbonization, Hydrogen, Circular economy, Carbon

Catalytic CH4 pyrolysis promoted by the interface of a molten metal–salt hybrid system

Hydrogen is an important chemical feedstock and energy carrier. A promising idea for a bridging technology for net-zero carbon emission is the catalytic pyrolysis of natural gas into hydrogen and solid carbon. However, the activation of methane and recovery of the produced carbon with high purity are the main hurdles for process commercialization. In the present study, molten metal–salt layered reaction beds for methane pyrolysis were investigated to determine the effect of the interface and the optimal ratio of metal and salt. These layered catalyst beds had several advantages over pure molten metal or molten salt catalyst beds. First, the length of the molten metal layer could be minimized to a level where the methane bubbles only touch the metal–salt interface, enhancing the economic feasibility of the process. Second, the metal–salt interface could delay bubble rising in proportion to the interfacial tension. Third, the molten salt layer could wash out the residual metal traces from the produced carbon, improving the carbon purity. This study would provide hints for building economically viable catalytic pyrolysis of methane based on molten metal-salt layered reaction bed.

A low carbon methanol process using natural gas pyrolysis in a catalytic molten metal bubble reactor

Due to its abundance and relatively low cost, natural gas will continue to be a common feedstock for methanol production, at least in the near to medium term. The present work focuses on natural gas pyrolysis in a catalytic liquid metal bubble reactor, combined with CO2utilization, as an alternative to traditional steam reforming processes. The pyrolysis reactor consists of multiple vertical tubes filled with molten Cu0.45Bi0.55alloy and heated in the radiant zone of a fired heater. The reactor geometry and operating conditions are optimized by rigorously accounting for the coupling of bubble flow hydrodynamics with the catalytic and non-catalytic kinetics of methane pyrolysis in molten metals. Pyrolysis generates hydrogen and solid carbon, which rise first through the liquid metal and then through a layer of molten salt (e.g., NaBr) whose purpose is to minimize the loss of liquid metal entrained with the carbon. The carbon forms a recoverable layer above the salt, and the hydrogen reacts with captured CO2in aseparate methanol synthesis reactor. The cradle-to-gate and cradle-to-grave CO2emissions are 0.074 and 1.45 t CO2-eq/t methanol, respectively, for median supply chain emissions of natural gas and captured CO2. This is a lower carbon footprint than other practical pyrolysis and steam methane reforming processes. Negative cradle-to-gate CO2emissions are achievable if natural gas and captured CO2are sourced from supply chains with low emissions. The estimated carbon production cost of $0.27/kg iswell below the recent market price of carbon black in the United States. The production cost of carbon is most sensitive to the fixed capital investment of the plant, the captured CO2cost, the natural gas and methanol costs, and the discount rate.

Low carbon hydrogen production in Canada via natural gas pyrolysis

Large scale, low cost, and low carbon intensity hydrogen production is needed to reduce emissions in the energy and transportation sectors. We present a techno-economic analysis and life cycle assessment of natural gas pyrolysis technologies for hydrogen production, with carbon black (CB) as a co-product. Four designs were considered based on the source of heat to the pyrolysis system, the combustion medium, and use of carbon capture (CC) technology. The oxygen-fired-CB design with CC is the most attractive from financial and environmental perspectives, superior to a conventional steam methane reformer (SMR) process with CC. The estimated pre-tax minimum hydrogen selling prices for the pyrolysis technologies range between $1.08/kg and $2.43/kg when natural gas (NG) costs $3.76/GJ. Key advantages include near-zero onsite GHG emissions of the oxygen-fired-CB design with CC and up to 41% lower GHG emissions compared to the SMR + CC process. The results indicate that natural gas pyrolysis may be a feasible pathway for hydrogen production.

Modern Technologies of Hydrogen Production

Transitioning to energy-saving and renewable energy sources is impossible without accelerated development of hydrogen energy and hydrogen technologies. This review summarizes the state-of-the-art and recent advances of various hydrogen production processes, including but not limited to thermochemical and electrolytic processes. Their opportunities and limitations, operating conditions, and catalysts are discussed. Nowadays, most hydrogen is still produced by steam reforming of methane, its partial oxidation, or coal gasification. Considerable attention is also paid to natural gas pyrolysis. However, hydrogen produced using these technologies has a lot of impurities and needs additional purification. A series of technologies for hydrogen purification, including its filtration through palladium alloy membranes, and membrane catalysis, allowing hydrogen production and purification in one stage, are discussed. The main way to produce carbon-free hydrogen is water electrolysis using low-cost energy from nuclear or renewable sources. Both conventional and novel methods of hydrogen storage and transportation, which are an important part of the hydrogen economy, are reviewed. Biohydrogen production technologies are also discussed. Finally, prospects for further work in this field are provided. This review will be useful to researchers and manufacturers working in this field.

Techno-economic and environmental assessment of LNG export for hydrogen production

A critical requirement of a widely contemplated hydrogen economy is the development of a low carbon hydrogen supply chain that is cost competitive. This comprehensive techno-economic assessment demonstrates, for the first time, the viability of a complete hydrogen supply chain based on the transport of liquefied natural gas (LNG). This is demonstrated via the established LNG trade route from Australia to Japan against three key performance indicators (KPIs): delivered hydrogen cost, CO2 emissions intensity (EI) across the entire supply chain, and technology readiness level (TRL). The hydrogen supply chain entails LNG export to Japan where it is used for blue hydrogen production; the by-product CO2 is then liquefied and repatriated to Australia for sequestration or utilisation. Within this supply chain, various hydrogen production technologies are assessed, including steam methane reforming (SMR), autothermal reforming (ATR) and natural gas pyrolysis (NGP). SMR with carbon capture and storage (CCS) resulted in the lowest total hydrogen supply cost of 19 USD/GJ (2.3 USD/kgH2) which comfortably meets the 2030 Japanese hydrogen cost target of 25 USD/GJ (3 USD/kgH2) and is very close to the 17 USD/GJ 2050 Japanese hydrogen cost target. This technology also obtained the lowest CO2 emission intensity (EI) of 38 kgCO2/GJ (4.5 kgCO2/kgH2); this was surprisingly lower than ATR with CCS primarily due to the emissions associated with ATR electricity provision for air separation. Future technologies and strategies are detailed so as to further reduce cost and supply chain emissions; these were shown to be able to reduce total CO2 EI to 14 kgCO2/GJ (1.6 kgCO2/kgH2). Hence this analysis indicates that this supply chain can act to significantly reduce CO2 emissions whilst uniquely meeting targeted hydrogen supply costs up to 2050. As such it is proposed here as an eminently viable hydrogen export option deploying both existing technology and capacity, at least until other hydrogen supply chain vectors (such as liquid hydrogen and ammonia) derived from green hydrogen production become competitive across all the KPIs.

Is hydrogen production through natural gas pyrolysis compatible with ambitious climate targets in the United States? A location-specific, time-resolved analysis

Pyrolysis of natural gas to produce H2 and solid carbon through methane cracking can be characterized as a high-CH4, low-CO2 process. It results in low CO2 emissions because no direct CO2 is generated at the point of H2 generation if solid carbon is not combusted further. However, it results in high CH4 emissions because of its higher natural gas consumption compared to the direct use of natural gas and, thus, higher CH4 losses along the natural gas supply chain. Here, I analyzed whether this process can provide climate benefit in comparison to the direct, unabated utilization of natural gas and also in comparison with H2 produced from water electrolysis with grid electricity. To this end, Monte Carlo simulations of time-resolved and US state-specific emission profiles and their impact on mid-century global warming under different CH4 mitigation scenarios were conducted. It was found that the climate benefit of natural gas pyrolysis is highly dependent on plant location and the speed at which CH4 emissions can be abated. New York, Pennsylvania, and Ohio emerged as the most promising locations. This is because of their projected long reliance on natural gas for power generation, which renders electrolysis using grid electricity less attractive, as well as the relatively low estimate of current CH4 emissions from the natural gas supply chain. However, without fast action on CH4 emission mitigation, the climate benefit of natural gas pyrolysis is small or non-existent, irrespective of the plant location. Overall, the uncertainty in the relative climate benefit of natural gas pyrolysis was found to be large; however, this study developed an easy-to-adapt MS Excel/visual basic for applications (VBA) tool that can be updated as soon as more accurate data on CH4 emissions becomes available. Policymakers, businesspeople, and scholars can use this tool to estimate the climate impact within their own scenarios and locations.

Flexible methanol production process using biomass/municipal solid waste and hydrogen produced by electrolysis and natural gas pyrolysis

Biomass-derived liquid fuels with low greenhouse gas emissions are an integral part of decarbonization plans. Three pathways for enhancing production of methanol from biomass and municipal solid waste (MSW), natural gas, and renewable electricity are explored using hydrogen produced from water electrolysis, natural gas pyrolysis, or combinations of these inputs. A combined electrolysis and natural gas pyrolysis process is designed to be flexible, changing operation modes depending on the cost of feedstocks (i.e. electricity and natural gas). A techno-economic analysis is performed to assess and compare the economic attractiveness of these processes. Hydrogen produced from natural gas pyrolysis could potentially be more economically attractive than electrolytic hydrogen using renewable electricity. Moreover, natural gas pyrolysis CO2 emissions could be substantially lower than emissions from conventional steam methane reforming (e.g., CO2 emissions which are 25 % or lower compared to CO2 emission from steam methane reforming). Hydrogen enhancement of the methanol production process results in increase of around a factor of two in carbon conversion efficiency (e.g. from 44% to 94 %). Methane pyrolysis shows high economic potential assuming the technical challenges to its commercialization are successfully addressed. Given an installed cost of electrolyzer of 1000 $/kW, electricity price of 50 $/MWh, natural gas price of 5 $/GJ and 100 $/ton selling price of carbon black, the natural gas pyrolysis design results in the lowest methanol production cost. Our analysis indicates that methanol could be produced in a price range of 300–1000$/ton depending on feedstock price (particularly electricity) and the chosen process.