Super-dry reforming of methane intensifies CO2 utilization via Le Chatelier’s principle
28 Oct 2016-Science (American Association for the Advancement of Science)-Vol. 354, Iss: 6311, pp 449-452
TL;DR: A “super-dry” CH4 reforming reaction for enhanced CO production from CH4 and CO2 was developed, which resulted in higher CO production as compared with that of conventional dry reforming, by avoiding back reactions with water.
Abstract: Efficient CO2 transformation from a waste product to a carbon source for chemicals and fuels will require reaction conditions that effect its reduction. We developed a “super-dry” CH4 reforming reaction for enhanced CO production from CH4 and CO2. We used Ni/MgAl2O4 as a CH4-reforming catalyst, Fe2O3/MgAl2O4 as a solid oxygen carrier, and CaO/Al2O3 as a CO2 sorbent. The isothermal coupling of these three different processes resulted in higher CO production as compared with that of conventional dry reforming, by avoiding back reactions with water. The reduction of iron oxide was intensified through CH4 conversion to syngas over Ni and CO2 extraction and storage as CaCO3. CO2 is then used for iron reoxidation and CO production, exploiting equilibrium shifts effected with inert gas sweeping (Le Chatelier’s principle). Super-dry reforming uses up to three CO2 molecules per CH4 and offers a high CO space-time yield of 7.5 millimole CO per second per kilogram of iron at 1023 kelvin.
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18 Oct 2018
TL;DR: In this article, the authors describe the mechanisms by which oxygen carriers undergo redox reactions and how these carriers can be incorporated into robust chemical looping reactors, central to which are redox cycles of metal oxides.
Abstract: Chemical looping offers a versatile platform to convert fuels and oxidizers in a clean and efficient manner. Central to this technology are metal oxide materials that can oxidize fuels, affording a reduced material that can be reoxidized to close the loop. Recent years have seen substantial advances in the design, formulation and manufacture of these oxygen carrier materials and their incorporation into chemical looping reactors for the production of various chemicals. This Review describes the mechanisms by which oxygen carriers undergo redox reactions and how these carriers can be incorporated into robust chemical looping reactors. One promising technology for modern energy and chemical conversions is chemical looping, central to which are redox cycles of metal oxides. This Review describes chemical looping schemes and the mechanisms by which metal oxide particles enable these technologies.
320 citations
TL;DR: Experimental and computational studies reveal that isolated Ni atoms are intrinsically coke-resistant due to their unique ability to only activate the first C-H bond in CH4, thus avoiding methane deep decomposition into carbon and offers new opportunities to develop large-scale DRM processes using earth abundant catalysts.
Abstract: Dry reforming of methane (DRM) is an attractive route to utilize CO2 as a chemical feedstock with which to convert CH4 into valuable syngas and simultaneously mitigate both greenhouse gases. Ni-based DRM catalysts are promising due to their high activity and low cost, but suffer from poor stability due to coke formation which has hindered their commercialization. Herein, we report that atomically dispersed Ni single atoms, stabilized by interaction with Ce-doped hydroxyapatite, are highly active and coke-resistant catalytic sites for DRM. Experimental and computational studies reveal that isolated Ni atoms are intrinsically coke-resistant due to their unique ability to only activate the first C-H bond in CH4, thus avoiding methane deep decomposition into carbon. This discovery offers new opportunities to develop large-scale DRM processes using earth abundant catalysts.
320 citations
TL;DR: In this article, the use of oxygen carriers or redox catalysts for chemical production has been investigated and shown to offer significant opportunities for process intensification and exergy loss minimization.
Abstract: As a promising approach for carbon dioxide capture, chemical looping combustion has been extensively investigated for more than two decades. However, the chemical looping strategy can be and has been extended well beyond carbon capture. In fact, significant impacts on emission reduction, energy conservation, and value-creation can be anticipated from chemical looping beyond combustion (CLBC). This article aims to demonstrate the versatility and transformational benefits of CLBC. Specifically, we focus on the use of oxygen carriers or redox catalysts for chemical production – a $4 trillion industry that consumes 40.9 quadrillion BTU of energy. Compared to state-of-the-art chemical production technologies, we illustrate that chemical looping offers significant opportunities for process intensification and exergy loss minimization. In many cases, an order of magnitude reduction in energy consumption and CO2 emission can be realized without the needs for carbon dioxide capture. In addition to providing various CLBC examples, this article elaborates on generalized design principles for CLBC, potential benefits and pitfalls, as well as redox catalyst selection, design, optimization, and redox reaction mechanism.
295 citations
TL;DR: A disruptive approach to a fundamental process is described by integrating an electrically heated catalytic structure directly into a steam-methane–reforming (SMR) reactor for hydrogen production, which could correspond to a reduction of nearly 1% of all CO2 emissions.
Abstract: Electrification of conventionally fired chemical reactors has the potential to reduce CO2 emissions and provide flexible and compact heat generation. Here, we describe a disruptive approach to a fundamental process by integrating an electrically heated catalytic structure directly into a steam-methane-reforming (SMR) reactor for hydrogen production. Intimate contact between the electric heat source and the reaction site drives the reaction close to thermal equilibrium, increases catalyst utilization, and limits unwanted byproduct formation. The integrated design with small characteristic length scales allows compact reactor designs, potentially 100 times smaller than current reformer platforms. Electrification of SMR offers a strong platform for new reactor design, scale, and implementation opportunities. Implemented on a global scale, this could correspond to a reduction of nearly 1% of all CO2 emissions.
234 citations
TL;DR: C1 catalysis refers to the conversion of simple carbon-containing compounds, such as carbon monoxide, carbon dioxide, methane, and methanol into high-value-added chemicals, petrochemical intermediates, and clean fuels as mentioned in this paper.
Abstract: C1 catalysis refers to the conversion of simple carbon-containing compounds, such as carbon monoxide, carbon dioxide, methane, and methanol into high-value-added chemicals, petrochemical intermediates, and clean fuels. Because of the rising oil price and the apprehension of fossil fuel depletion in the future, C1 catalysis has been attracting widespread academic and industrial interest and became one of the most attractive research fields in heterogeneous catalysis. Especially in recent years, benefiting from advanced technology development, precise and controllable material synthesis methods, and powerful computational simulation capabilities, C1 catalysis has achieved remarkable progress in many aspects, including insights into the reaction mechanism, identification of active-site structures, highly efficient catalysts and reaction process, and the reactor designs. This Review highlights the latest developments (from 2012 to 2018) in highly efficient catalyst systems and reaction processes in this field...
206 citations
References
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TL;DR: Modular optimization of covalent organic frameworks (COFs) is reported, in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO.
Abstract: Conversion of carbon dioxide (CO2) to carbon monoxide (CO) and other value-added carbon products is an important challenge for clean energy research. Here we report modular optimization of covalent organic frameworks (COFs), in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO. The catalysts exhibit high Faradaic efficiency (90%) and turnover numbers (up to 290,000, with initial turnover frequency of 9400 hour(-1)) at pH 7 with an overpotential of -0.55 volts, equivalent to a 26-fold improvement in activity compared with the molecular cobalt complex, with no degradation over 24 hours. X-ray absorption data reveal the influence of the COF environment on the electronic structure of the catalytic cobalt centers.
1,844 citations
TL;DR: In this article, the authors review the leading CO2 capture technologies, available in the short and long term, and their technological maturity, before discussing CO2 transport and storage, as well as the economic and legal aspects of CCS.
Abstract: In recent years, Carbon Capture and Storage (Sequestration) (CCS) has been proposed as a potential method to allow the continued use of fossil-fuelled power stations whilst preventing emissions of CO2 from reaching the atmosphere. Gas, coal (and biomass)-fired power stations can respond to changes in demand more readily than many other sources of electricity production, hence the importance of retaining them as an option in the energy mix. Here, we review the leading CO2 capture technologies, available in the short and long term, and their technological maturity, before discussing CO2 transport and storage. Current pilot plants and demonstrations are highlighted, as is the importance of optimising the CCS system as a whole. Other topics briefly discussed include the viability of both the capture of CO2 from the air and CO2 reutilisation as climate change mitigation strategies. Finally, we discuss the economic and legal aspects of CCS.
1,752 citations
TL;DR: In this paper, the authors proposed to use CO2 for environmentally-benign physical and chemical processing that adds value to the process, using CO2 as an alternate medium or solvent or co-reactant or a combination of them.
1,541 citations
TL;DR: Dry (CO2) reforming of methane literature for catalysts based on Rh, Ru, Pt, and Pd metals is reviewed, including the effect of these noble metals on the kinetics, mechanism and deactivation of these catalysts.
Abstract: Dry (CO2) reforming of methane (DRM) is a well-studied reaction that is of both scientific and industrial importance. This reaction produces syngas that can be used to produce a wide range of products, such as higher alkanes and oxygenates by means of Fischer–Tropsch synthesis. DRM is inevitably accompanied by deactivation due to carbon deposition. DRM is also a highly endothermic reaction and requires operating temperatures of 800–1000 °C to attain high equilibrium conversion of CH4 and CO2 to H2 and CO and to minimize the thermodynamic driving force for carbon deposition. The most widely used catalysts for DRM are based on Ni. However, many of these catalysts undergo severe deactivation due to carbon deposition. Noble metals have also been studied and are typically found to be much more resistant to carbon deposition than Ni catalysts, but are generally uneconomical. Noble metals can also be used to promote the Ni catalysts in order to increase their resistance to deactivation. In order to design catalysts that minimize deactivation, it is necessary to understand the elementary steps involved in the activation and conversion of CH4 and CO2. This review will cover DRM literature for catalysts based on Rh, Ru, Pt, and Pd metals. This includes the effect of these noble metals on the kinetics, mechanism and deactivation of these catalysts.
1,472 citations
TL;DR: A composite catalyst circumvents conventional limitations on the Fischer-Tropsch synthesis of light olefins from syngas and achieves higher conversions and avoids deactivation through carbon buildup, by enabling a bifunctional catalyst affording two types of active sites with complementary properties.
Abstract: Although considerable progress has been made in direct synthesis gas (syngas) conversion to light olefins (C2(=)-C4(=)) via Fischer-Tropsch synthesis (FTS), the wide product distribution remains a challenge, with a theoretical limit of only 58% for C2-C4 hydrocarbons. We present a process that reaches C2(=)-C4(=) selectivity as high as 80% and C2-C4 94% at carbon monoxide (CO) conversion of 17%. This is enabled by a bifunctional catalyst affording two types of active sites with complementary properties. The partially reduced oxide surface (ZnCrO(x)) activates CO and H2, and C-C coupling is subsequently manipulated within the confined acidic pores of zeolites. No obvious deactivation is observed within 110 hours. Furthermore, this composite catalyst and the process may allow use of coal- and biomass-derived syngas with a low H2/CO ratio.
991 citations