Application of core-shell-structured K2CO3-based sorbents in postcombustion CO2 capture: Statistical analysis and optimization using response surface methodology

11 Figuras, 6 Tablas.-- Información suplementaria disponible en línea en la página web del editor.-- This document is the Accepted Manuscript version of a Published Work that appeared in final form in Energy and Fuels, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.energyfuels.9b03442This study investigates the effect of core-shell-structured supports prepared with alumina as the core on the CO2 capture performance of K2CO3. One main issue in using alumina-based-supported K2CO3 is the high moisture uptake of the sorbent, which converts active sites of K2CO3 to hydrated byproducts with a very low CO2 capture capacity. To address this issue, the support was shelled with a less hydrophilic material using a core-shell technique. Six core-shell-structured supports were prepared using alumina-based cores (γ-alumina and boehmite), and TiO2, ZrO2, and SiO2 shells. K2CO3 was impregnated on each support and tested in a thermogravimetric analyzer over ten cycles. K2CO3/boehmite/TiO2 showed the lowest moisture uptake and the highest surface area, and thus the best CO2 capture performance. A semiempirical model was developed using a response surface methodology to optimize the CO2 capture capacity of K2CO3/boehmite/TiO2. The optimal amounts of the operating parameters including carbonation temperature, carbonation time, and H2O-to-CO2 flow rate ratio, were 61 °C, 40 min, and 1.15, respectively. The maximum CO2 capture capacity at the optimal point was 6.61 mmol CO2/g K2CO3, which is equal to 92% of the theoretical value. Therefore, the use of K2CO3/boehmite/TiO2 at the obtained optimal condition is proposed as a suitable option for postcombustion processes.The authors would like to acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding this study through its Industrial Research Chairs (IRC) program.Peer reviewe

Photocatalytic removal of 2-nitrophenol using silver and sulfur co-doped TiO2 under natural solar light

To overcome the drawback of poor solar light utilization brought about by the narrow photoresponse range of TiO2, a silver and sulfur co-doped TiO2 was synthesized. Using the prepared catalyst, solar photocatalytic degradation of 2-nitrophenol (2-NP) by a TiO2-based catalyst was studied for the first time. Effects of the co-doping on the structural, optical and morphological properties of the synthesized nanoparticles were investigated by different characterization methods: X-ray diffraction, N2 adsorption-desorption measurements, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy. Solar experiments showed that the co-doping with silver and sulfur significantly increased the photocatalytic activity. In various initial concentrations of 2-NP more than 99% of the contaminant was decomposed by Ag-S/TiO2 in less than 150 minutes, while the degradation efficiency was much less in the presence of bare TiO2. Kinetic studies suggested that solar photocatalytic degradation of 2-NP is consistent with the Langmuir-Hinshelwood model. The rate constant of the reaction and adsorption constant of the modified photocatalyst were found to be 2.4 and 4.1 times larger than that of bare TiO2, respectively

Investigation of 2-nitrophenol solar degradation in the simultaneous presence of K\u3csub\u3e2\u3c/sub\u3eS\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e8\u3c/sub\u3e and H\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e: Using experimental design and artificial neural network

In this study, the interaction effect of K2S2O8 (PDS) and H2O2 (as two powerful oxidants) was investigated on the solar degradation of 2-nitrophenol (2-NF) in the two systems, i.e. absence and presence of Ag/S/TiO2 photocatalyst. Experiments were designed based on the central composite design, and two methods of response surface methodology (RSM) and artificial neural network (ANN) were developed for modeling of the systems. Concentrations of PDS and H2O2 were considered as independent variables and 2-NF degradation efficiency was selected as the response. It was revealed that the predictive capacity of ANN model is more than RSM model according to their corresponding R2, R2adj, RMS, MAE, and AAD values. Therefore, ANN model was utilized to analyze the effects of the independent variables. Moreover, it was found that, by increasing the amount of either PDS or H2O2, less amount of the other oxidant was required to reach the highest degradation efficiency which shows the contributive effect of the oxidants on each other. By adding Ag/S/TiO2 visible-light-sensitive photocatalyst to the solution containing PDS and H2O2, a significant enhancement in the 2-NF degradation efficiency was observed. Using an ANN-genetic algorithm (ANN-GA) approach, the values of 172.1 mg/l and 80.9 mg/l were respectively obtained as optimum concentrations for PDS and H2O2 (in the presence of the photocatalyst). Under this condition, 2-NF degradation efficiency was predicted to be 96% after only 45 min of solar light irradiation that is in a good agreement with the actual degradation efficiency of 97.1% obtained at the optimum concentrations. In addition, the relative importance of the independent variables was studied using Garson method and it was found that PDS had more impact on the response in comparison with H2O2

Performance evaluation of a Cu-based oxygen carrier impregnated onto ZrO2 for Chemical-Looping Combustion (CLC)

11 figures, 3 tables.-- This document is the Accepted Manuscript version of a Published Work that appeared in final form in Industrial and Engineering Chemistry Research, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.iecr.9b05835Chemical-looping combustion (CLC) has been introduced as a promising technique with inherent advantages for efficient, low-cost CO2 separation. The type of oxygen carrier employed plays a vital role in improving the overall efficiency and economic penalty of the system. This study investigates the performance of a CuO oxygen carrier impregnated onto ZrO2 in a continuously operated 500 Wth CLC unit over 30 h of CH4 combustion. A decrease in combustion efficiency was observed during the initial 10 h followed by stabilization. A loss of CuO of between 13 and 5 wt % was recorded during the first 5 h of combustion before the CuO content was kept constant. This loss was due to the Cu layer peeling off the surface of particles and the clustering and migration of CuO from internal areas to the surface and then attrited. The effect of the oxygen carrier-to-fuel ratio (ϕ) on the combustion efficiency of the impregnated Cu-based oxygen carrier was studied. In order to reach a combustion efficiency of 99%, ϕ values of 3.9 were needed. The particle attrition rate was stabilized after 30 h of operation at 0.06%/h, and the estimated lifetime was 1500 h of operation. XRD and TPR analyses confirmed very low interaction between CuO and the support (ZrO2), which was unable to retain CuO inside the particles. Therefore, the lack of interaction between CuO and the ZrO2 support is not positive for oxygen carrier behavior in the CLC process.The work presented in this article is partially funded by the Spanish Research Council (CSIC) through the Intramural Project (201980E043) and by the European Commission Seventh Framework Programme under Grant 608571 (Project acronym SUCCESS). S. Toufigh Bararpour is grateful to Mitacs Globalink Research for the award received (Mitacs Globalink Research Award IT13491 for students studying in Canadian universities).Peer reviewe