A thermodynamic analysis of methanation reactions of carbon oxides for the production of synthetic natural gas
TL;DR: In this paper, a comprehensive thermodynamic analysis of reactions occurring in the methanation of carbon oxides (CO and CO2) is conducted using the Gibbs free energy minimization method.
Abstract: Synthetic natural gas (SNG) can be obtained via methanation of synthesis gas (syngas). Many thermodynamic reaction details involved in this process are not yet fully understood. In this paper, a comprehensive thermodynamic analysis of reactions occurring in the methanation of carbon oxides (CO and CO2) is conducted using the Gibbs free energy minimization method. The equilibrium constants of eight reactions involved in the methanation reactions were calculated at different temperatures. The effects of temperature, pressure, ratio of H-2/CO (and H-2/CO2), and the addition of other compounds (H2O, O-2, CH4, and C2H4) in the feed gas (syngas) on the conversion of CO and CO2, CH4 selectivity and yield, as well as carbon deposition, were carefully investigated. In addition, experimental data obtained on commercial Ni-based catalysts for CO methanation and three cases adopted from the literature were compared with the thermodynamic calculations. It is found that low temperature, high pressure, and a large H-2/CO (and H-2/CO2) ratio are favourable for the methanation reactions. Adding steam into the feed gas could alleviate the carbon deposition to a large extent. Trace amounts of O-2 in syngas is unfavourable for SNG generation although it can lower carbon deposition. Additional CH4 in the feed gas almost has no influence on the CO conversion and CH4 yield, but it leads to the increase of carbon formed. Introduction of a small amount of C2H4, a representative of hydrocarbons in syngas, results in low CH4 yield and serious carbon deposition although it does not affect CO conversion. CO is relatively easy to hydrogenated compared to CO2 at the same reaction conditions. The comparison of thermodynamic calculations with experimental results demonstrated that the Gibbs free energy minimization method is significantly effective for understanding the reactions occurring in methanation and helpful for the development of catalysts and processes for the production of SNG.
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TL;DR: The motivation to develop CO2-based chemistry does not depend primarily on the absolute amount of CO2 emissions that can be remediated by a single technology and is stimulated by the significance of the relative improvement in carbon balance and other critical factors defining the environmental impact of chemical production in all relevant sectors in accord with the principles of green chemistry.
Abstract: CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...
1,346 citations
TL;DR: A comprehensive overview of methanation research conducted during the last century is presented in this paper, where application-oriented research focusing on reactor developments, reactor modeling, and pilot plant investigation is reviewed.
973 citations
TL;DR: In this paper, a review of the progress in gasification techniques and key generation pathways for biofuel production, process design and integration and socio-environmental impacts of biofuel generation are discussed, with the goal of investigating gasification-to-biofuels credentials as a sustainable and eco-friendly technology.
478 citations
TL;DR: In this article, the authors provide an overview of advances in CO2 hydrogenation to hydrocarbons that have been achieved recently in terms of catalyst design, catalytic performance and reaction mechanism from both experiments and density functional theory calculations.
Abstract: CO2 hydrogenation to hydrocarbons is a promising way of making waste to wealth and energy storage, which also solves the environmental and energy issues caused by CO2 emissions Much efforts and research are aimed at the conversion of CO2 via hydrogenation to various value-added hydrocarbons, such as CH4, lower olefins, gasoline, or long-chain hydrocarbons catalyzed by different catalysts with various mechanisms This review provides an overview of advances in CO2 hydrogenation to hydrocarbons that have been achieved recently in terms of catalyst design, catalytic performance and reaction mechanism from both experiments and density functional theory calculations In addition, the factors influencing the performance of catalysts and the first C–C coupling mechanism through different routes are also revealed The fundamental factor for product selectivity is the surface H/C ratio adjusted by active metals, supports and promoters Furthermore, the technical and application challenges of CO2 conversion into useful fuels/chemicals are also summarized To meet these challenges, future research directions are proposed in this review
436 citations
TL;DR: In this paper, a comprehensive review of methanation catalysts for coal-or biomass-derived carbon oxides for production of synthetic natural gas (SNG) is provided, covering reaction thermodynamics, mechanism and kinetics, the effects of catalyst active components, supports, promoters and preparation methods.
Abstract: Methanation of coal-or biomass-derived carbon oxides for production of synthetic natural gas (SNG) is gaining considerable interest due to energy issues and the opportunity of reducing greenhouse gases by carbon dioxide conversion. The key component of the methanation process is the catalyst design. Ideally, the catalyst should show high activity at low temperatures (200-300 degrees C) and high stability at high temperatures (600-700 degrees C). In the past decades, various methanation catalysts have been investigated, among which transition metals including Ni, Fe, Co, Ru, Mo, etc. dispersed on metal oxide supports such as Al2O3, SiO2, TiO2, ZrO2, CeO2 etc. have received great attention due to their relatively high catalytic activity and selectivity. Furthermore, over the past few years, great efforts have been made both in methanation catalysts development and reaction mechanism investigation. Here we provide a comprehensive review to these most advancements, covering the reaction thermodynamics, mechanism and kinetics, the effects of catalyst active components, supports, promoters and preparation methods, hoping to outline the pathways for the future methanation catalysts design and development for SNG production.
396 citations
References
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TL;DR: A review of the processes developed for the production of SNG from coal during the sixties and seventies and the recent developments for SNG production from coal and from dry biomass can be found in this paper.
878 citations
TL;DR: In this article, the authors investigated the causes of deactivation of supported metal catalysts by carbon or coke formation, and found that deactivation can occur due to fouling of the metal surface, blockage of catalysts pores and voids, and actual physical disintegration of the catalyst support.
Abstract: Deactivation of supported metal catalysts by carbon or coke formation is a problem of serious magnitude in steam reforming, methanation, and other important catalytic processes. Its causes are generally threefold: (1) fouling of the metal surface, (2) blockage of catalysts pores and voids, and/or (3) actual physical disintegration of the catalyst support. Since loss of catalytic activity and physical destruction of the catalyst by carbon deposits can occur rapidly (within hours or days) under unfavorable conditions, understanding and control of these effects are of major technological and economical importance.
760 citations
TL;DR: In this paper, the authors focus on recent developments in catalytic materials, novel reactors, and reaction mechanism for methanation of CO2, which is a particularly promising technique for producing energy carrier or chemical.
Abstract: Although being very challenging, utilization of carbon dioxide (CO2) originating from production processes and flue gases of CO2-intensive sectors has a great environmental and industrial potential due to improving the resource efficiency of industry as well as by contributing to the reduction of CO2 emissions. As a renewable and environmentally friendly source of carbon, catalytic approaches for CO2 fixation in the synthesis of chemicals offer the way to mitigate the increasing CO2 buildup. Among the catalytic reactions, methanation of CO2 is a particularly promising technique for producing energy carrier or chemical. This article focuses on recent developments in catalytic materials, novel reactors, and reaction mechanism for methanation of CO2.
466 citations
TL;DR: In this article, a thermodynamic equilibrium analysis on the multi-reaction system for carbon dioxide reforming of methane in view of carbon formation was performed with Aspen plus based on direct minimization of Gibbs free energy method.
455 citations
TL;DR: In this article, a reverse microemulsion synthesis of palladium and magnesium in silica was used for CO2 methanation, and the Pd-Mg/SiO2 catalyst had greater than 95% selectivity to CH4 at a carbon dioxide conversion of 59%.
396 citations