Potential sources of CO2 and the options for its large-scale utilisation now and in the future
Abstract
The current emissions of CO2 to the atmosphere through man-made activities are outlined and the options for recycling CO2 for some useful purpose, as distinct from simply storing or disposing it in an environmentally-benign manner, are discussed. It is shown that for CO2 recycling to have any significant impact on reducing emissions of this gas, it must form part of some large-scale energy conversion process which is based on a non-fossil-fuel energy source such as solar or nuclear energy. Since the quantities of undiluted CO2 available for recycling are relatively small, the cost of recovering CO2 from sources such as power station flue gas must be taken into account in the overall CO2 recycling/energy conversion scheme.
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Advances in catalytic dry reforming of methane (DRM): Emerging trends, current challenges, and future perspectives
2023, Journal of Cleaner ProductionThe escalating levels of atmospheric carbon dioxide (CO2) and methane in recent decades have generated significant interest among researchers worldwide to identify expeditious solutions to this issue. A feasible alternative entails the utilization of CO2 in conjunction with methane to generate syngas by means of catalytic reforming. Extensive research has been conducted on the method, but there is a lack of literature on determining the reaction pathway network using an effective catalyst and optimizing the reactions. This article presents a current evaluation of advancements made in the reaction chemistry associated with the dry reforming of methane (DRM). Additionally, it summarizes recent breakthroughs achieved through the utilization of different catalysts in the DRM process, employing advanced experimental and theoretical methodologies. The efficacy of catalysts utilized in the process of DRM is heavily reliant on the choice of support materials, active phases, synthetic techniques, and reactor configurations. The present study investigates the impact of mentioned factors on the performance and stability of specific catalysts. The development of a cost-effective catalyst that exhibits both sustained catalytic activity and stability can be accomplished through the strategic utilization of synergistic interactions between noble and/or non-noble metals, resulting in the formation of bi- and tri-metallic catalysts that are both highly active and stable. The present investigation offers insights into the catalytic characteristics and their correlation with catalytic efficacy, which are essential for the systematic development of catalysts that are appropriate for DRM.
Novel catalyst configuration to boost the yield of longer hydrocarbons from methanol-mediated CO<inf>2</inf> hydrogenation
2023, Journal of CO2 UtilizationVarious C1 feedstocks and lower hydrocarbons (C2-C4) can be produced from CO2 hydrogenation, which is an important way to utilize excess CO2 and provide alternative fuel options for dwindling fossil fuels. Herein, a novel two-bed catalytic system was developed to increase the yield of liquid range hydrocarbons, where the first catalytic bed was composed of In2O3-ZrO2 (13 wt. In %)/HZSM-5 and the second bed was a desilicated HZSM-5 placed downstream from the first bed. A maximum hydrocarbon selectivity was found to be about 86% with 7.2% CO2 conversion at 533 K, while conversion increased up to 19.3% with 71.2% hydrocarbon selectivity at 623 K while keeping the pressure at 4.0 MPa. The selectivity of longer liquid range hydrocarbons (C8-C12) was increased from 29.2% to 42.4% using the oligomerization process in which the produced lower olefins from the first bed were oligomerized to enhance the liquid range hydrocarbon over desilicated HZSM-5. Additionally, a comparative study was carried out to examine the effect of desilication over HZSM-5 having different silica-to-alumina ratios of 24 and 59. Moreover, detailed characterizations were carried out before and after the desilication of the HZSM-5 to correlate catalytic activities with physical and chemical properties of the catalysts. The results suggest that a two-bed catalytic system is a promising option to increase the yield of liquid range hydrocarbons from methanol-mediated CO2 hydrogenation while there was a negligible effect on CO2 conversion due to the second bed.
Decarbonization roadmaps for ASEAN and their implications
2022, Energy ReportsThe objective of this paper is to derive, for the first time, decarbonization roadmaps for the ten nations of ASEAN. This study first presents a regional view of ASEAN’s fossil and renewable energy usage and energy-related CO2 emission. Results show that renewable energies have been losing ground to fossil energies in the last two decades and fossil fuels will likely continue to be an important part of ASEAN’s energy mix for the next few decades. Therefore, decarbonizing efforts should focus not only on increasing the share of renewable energies in electricity generation, but also on technologies to reduce CO2 emission from fossil power and industrial plants. This study next performs a technology mapping exercise for all ten ASEAN countries to determine decarbonization technologies that have high impact and high readiness for individual countries. Besides installing more sustainable renewable energies, common themes coming from these roadmaps include switching from coal to gas for power generation, using carbon capture and storage (CCS) technologies to decarbonize fossil and industrial plants, replacing internal combustion vehicles by electric vehicles, and for countries that have coal and natural gas resources, upgrading them to blue hydrogen by chemical processes and using CCS to mitigate the emitted CO2. Blue hydrogen can be used to decarbonize hard-to-decarbonize industries. Policy implications of these roadmaps include imposing a credible carbon tax, establishing a national hydrogen strategy, intergovernmental coordination to establish regional CCS corridors, funding research and development to improve carbon capture efficiency on a plant level and resolving sustainability issues of hydropower and bioenergy in ASEAN.
CO<inf>2</inf> Decomposition Using Activated Rh- and Ru-SrFeO<inf>3-δ</inf> for Cyclic Production of CO
2021, Journal of CO2 UtilizationAs global warming problem caused by greenhouse gas (GHG) emissions accelerates, many methods to remove carbon dioxide (CO2) have been proposed. In particular, CO2 decomposition has been developed for GHG emission reduction and CO2 upcycling. Our group previously reported on the results of efficient CO2 decomposition using SrFeO3-δ (perovskite-type metal oxide). According to the results of the isothermal test of SrFeO3-δ, reaction for a long time at high temperatures is necessary for effective CO2 decomposition, and this may lead to inefficient energy use. Therefore, in this study, Rh and Ru were impregnated as catalysts to SrFeO3-δ. As a result of CO2 decomposition using these catalysts, CO2 decomposition appeared at a low temperature of ∼200 °C. The maximum produced CO concentration was 3 times higher due to the spillover phenomenon of the precious metal catalysts. The cyclic tests showed catalyst stabilities of Rh- and Ru-SrFeO3-δ as well as the potential for continued and improved CO production. In additions, this study demonstrated that the decomposition of CO2 and the production of CO are performed by reverse Boudouard reactions as well as oxygen vacancies. It is expected that these results will contribute to GHG emission reduction.
Thermodynamic analysis of tri-reforming of oxy-fuel combustion exhaust gas
2020, Journal of CO2 UtilizationA thermodynamic equilibrium analysis of the tri-reforming of oxy-combustion exhaust gases based on the minimisation of the Gibbs energy, was performed. To capture the effect of air leakage into the oxy-combustion boiler, two cases were investigated, representing 10 % and 1% combustion air leakage. The effects of temperature, pressure, and the ratio of methane to carbon dioxide (CH4/CO2) on the tri-reforming of the exhaust gases was studied. The domain of the practical operating regime for the tri-reforming of exhaust gases which is circumscribed by the maximum operating temperature, minimum CO2 conversion and zero-coke equilibrium was identified. In addition, three reactions (steam reforming, dry reforming and reverse water gas shift) were identified to be dominating in the temperature domain above the zero-coke equilibrium temperature. Within the boundaries of the practical operating regime, the tri-reforming of coal oxy-combustion exhaust gas results in more than three times the net conversion of CO2/kg CH4, when compared to the tri-reforming of conventional coal combustion exhaust gas.