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Currently, the oil sands industry is producing millions of tons of tailings by‐products from the tailings solvent recovery unit (TSRU) into the tailings ponds. TSRU tailings (TTs) consist of water, asphaltene, and minerals, including silica and alumina mixtures. The oil sands sector has expanded efforts to discover solutions to remove the tailings ponds due to growing public concern about the environmental effects of these ponds and stiffer government rules on their disposal. Therefore, this report studied the effect of the different methods for the conversion of the TTs into the activated carbon‐zeolite composite. The TTs were treated with activation followed by hydrothermal, either with or without fusion with NaOH at 800°C for 1 h as a pre‐treatment. Zeolite Na‐P, zeolite A, and zeolite X were identified during the different characterizations, depending on the pre‐treatment of the fusion. The result showed that the fusion with NaOH before the hydrothermal reaction was effective as it increased the porosity and adsorption of the composite. The CO2 capture capacity of the product before fusion was 0.19 mmol/g, and after fusion, it was improved to 0.486 mmol/g. [ABSTRACT FROM AUTHOR]

Calcium looping process is a promising approach for CO2 capture from the flue gas of fossil fuel power plants and the cement industry. Even though the advantages of calcium‐based sorbents are low cost and high uptake capacity, they suffer from low durability during cycles. Modified sorbents were fabricated by adding alumina and zirconia and the mixture of alumina and zirconia to calcium oxide via the co‐precipitation method. The performance of synthesized sorbents in terms of stability and CO2 capture capacity were evaluated using a fixed bed reactor in various CO2 sorption/desorption cycles. The sorbents were fabricated by a co‐precipitation methodology using 10% binders (alumina and/or silica). X‐ray diffraction (XRD), BET/BJH, and scanning electron microscopy (SEM) were conducted for characterization of synthesized sorbents. CaO‐10% ZrO2 showed the best performance among the fabricated sorbents in terms of stability during 5 cycles and CO2 capacity (14 mmol CO2/g sorbent). The formation of CaZrO3 with a perovskite structure and high‐temperature resistance could be attributed to well performance of zirconia‐supported sorbent. On the other hand, no sign of aluminum zirconate formation was approved in XRD analysis for the fabricated sorbent using mixed binders of zirconia and alumina to enhance its stability during cycles. [ABSTRACT FROM AUTHOR]

Calcium oxide (CaO) has been investigated as a high-temperature performance sorption material for carbon capture due to its high carbon dioxide (CO2) capacity, low cost, and environmental benignity. Unfortunately, commercialized application of CaO materials has been hindered by severe capacity loss during cycling operations. In an attempt to overcome these problems, this study investigated the effects of adding zirconia-based ceramic dopants and coating sorbents with highly crystalline zirconium dioxide (ZrO2) layers derived from the hydrolysis of zirconium butoxide to control the growth of ZrO2 crystals. Uncoated natural Cadomin delivered a high CO2 capture capacity of more than 13 mol CO2/kg, while the zirconia-coated sorbents showed excellent cycling stability corresponding to a maximum capacity of retention of 79% after 21 cycles at high temperatures. More importantly, the highly crystalline ZrO2-coated sorbents doped by zirconia-based sorbents exhibited a significantly lower decay capacity compared to the uncoated sorbents, which could be attributed to the formation of a perovskite structure that is resistant at high temperatures and a high-temperature-resistant ceramic layer through the solid-state reaction of the highly mesoporous crystalline ZrO2 layer with CaO. These results shed light on the development of sorbents with special structures and superior chemical and mechanical properties for high-performance calcium looping or regenerative calcium cycle processes. [ABSTRACT FROM AUTHOR]

In this study, a series of core-shell structured spheriform CO2 sorbents were synthesized by using CaO-based pellets as cores and different mesoporous metal oxides (e.g. alumina, ceria, and yttrium-stabilized zirconia) as shells through a repeated wet impregnation coating process. Cyclic CO2 capture performance of the obtained sorbents was investigated using a thermogravimetric analyzer. Among all the core/shell sorbents under study, the pellets coated with a layer of alumina exhibit the best performance in the retention of CO2 uptake over 20 cycles with the lowest activity loss of only 30.4 %, attributed to the existence of the thermal stable porous alumina shell which prevents the sintering and the aggregation of the CaO grains. Moreover, the attrition study using an air-jet apparatus and a standard test method reveals that such sorbents exhibit enhanced attrition resistance due to the protection of the porous shell providing them with a great potential for application in fluidized bed conditions. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) capture is a process that can significantly reduce the amount of CO2 in the atmosphere. In this study, several solid sorbents were examined for their CO2 capturing performance over 30 carbonation-calcination cycles. The sorbents included natural calcined Cadomin limestone (denoted as CD), hydrated calcined Cadomin pellets (denoted as CP), core/shell sorbets with CD and CP as cores, and mesostructured silica (denoted as CD@Si and CP@Si, respectively) and titania (denoted as CD@Ti and CP@Ti) as shells. The core/shell sorbents were prepared with a protective porous shell using the mesoporous silica and titania layers. The surface morphology and porosity of all sorbents were qualified using scanning electron microscopy and were quantified using nitrogen physisorption. X-ray diffraction was also used to identify the crystal phase composition of the sorbents before and after calcination. The CP@Ti pellets showed the best performance in the retention of CO2 uptake over 30 cycles with an activity loss of 50.9%. This is attributed to the formation of a protective layer of thermally stable mesoporous titania using a sol-gel method, which prevented the aggregation of CaO crystals and sorbent sintering. Although the modified core/shell sorbents exhibited an improvement in maintaining the stability of the cyclic operation compared to natural limestone, further study is needed to understand the core/shell sintering phenomenon at high temperatures using other novel materials. [ABSTRACT FROM AUTHOR]

The behavior of the carbonation reactionof the calcined Cadominlimestone used for CO2capture is described using the grainmodel and the changing grain size (CGS) model. To calculate the overallconversion over time, the mathematical modeling was solved semianalytically.The overall sorbent conversion obtained with the CGS model showedbetter agreement with the experimental data than the results obtainedusing the grain model. In the CGS model, the physical structure ofthe sorbent particle changes during the reaction. The CGS model wasmodified by considering a variable diffusion coefficient of the gaseousreactant through the development of the product layer. The modelingresults showed the positive effects of increasing the reaction temperatureand particle porosity on the rate of carbonation reaction. However,the rate of carbonation reaction decreased by increasing the sorbentparticle size. Moreover, the modeling results demonstrated an initialkinetic control stage which was followed by a diffusion control stepin the carbonation reaction of the calcined Cadomin limestone. [ABSTRACT FROM AUTHOR]

Highlights: [•] CaO-based pellet sorbents were tested for 31 carbonation–calcination cycles. [•] Pellet surface characterization was investigated using BET/BJH, XRD, and SEM tests. [•] Pellet sorbents exhibit lower activity loss than natural limestone. [•] Binders decreased the negative effect of sintering. [•] The core/shell pellets had the highest stability among the sorbents. [ABSTRACT FROM AUTHOR]

Thesteam gasification of biomass in the presence of calcium oxideoffers a viable route for the dual purpose of hydrogen productionand carbon dioxide (CO2) capture. Although previous studieshave dealt with experimental and intrinsic rate constants of carbonationand calcination of calcium looping cycles, the data has not been comparedwith thermodynamic or kinetic simulation. In this study, the thermodynamicand kinetic simulation of the CO2capture process usingtwo calcium-based sorbents (i.e., Imasco dolomite and Cadomin limestone)have been studied using Aspen Plus software. The thermodynamic simulationwas able to predict the overall trend of the CO2adsorptionon dolomite and limestone. However, a kinetic model was also appliedto achieve a more accurate analysis. The results show good agreementbetween the modeling and the experimental data obtained using a thermogravimetricanalyzer (TGA). A shift in the reaction mechanism was observed withrespect to temperature. The experimental data and kinetic model illustratedthat the maximum conversion occurred at 650 °C. [ABSTRACT FROM AUTHOR]