| 1. |
- Suarez Corredor, Andres Felipe, 1988, et al.
(författare)
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Characterization Method for Gas Flow Reactor Experiments-NH3 Adsorption on Vanadium-Based SCR Catalysts
- 2021
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 60:30, s. 11399-11411
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Tidskriftsartikel (refereegranskat)abstract
- In this study, NH3 adsorption isotherms for a commercial vanadium-based SCR catalyst coated on a monolith substrate were obtained using a gas flow reactor over a wide range of parameters which have not been performed before in a single study. The isotherms were obtained under different conditions, where adsorption temperature, NH3 concentration, water concentration, washcoat loading, and catalyst oxidation state were varied. For this purpose, a systematic data processing method was developed, which characterizes the dispersion and delay effects in the experimental setup using a residence time distribution model, and artifacts such as NH3 adsorbed in the experimental setup and uncertainties in the washcoat loading were removed. As a result, data from different catalyst samples were integrated, and adsorption isotherms with low data spread and well-defined regions were obtained. This allows the identification of the complex nature of the catalyst and dynamics, where multiple types of adsorption sites are present. For instance, the oxidized catalyst has 50% higher NH3 storage capacity compared to the reduced state of the sample. Moreover, water reduces the NH3 storage capacity at high concentrations (5.0%), whereas at low concentration (0.5%), water increases the NH3 adsorption capacity for an oxidized catalyst. The proposed data processing method can be extended for the analysis of further phenomena in catalysts studied using gas flow reactors, complementing current methods and providing information for models with extended validity and lower parameter correlations.
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| 2. |
- Suarez Corredor, Andres Felipe, 1988, et al.
(författare)
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Understanding the NH3 adsorption mechanism on a vanadium-based SCR catalyst : A data-driven modeling approach
- 2022
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 262
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia adsorption is a precondition for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) to take place and it influences catalyst performance under transient conditions. For a vanadium-based SCR catalyst NH3 adsorption takes place on multiple adsorption sites over the catalyst surface with different behaviours depending on temperature, gas concentration and catalyst oxidation state. In this study, a mechanistic NH3 adsorption model within the framework of Langmuir adsorption models was developed for describing the NH3 adsorption isotherms obtained with a gas flow reactor for a vanadium-based SCR. The model was created by a data-driven modeling process, which involves different steps. First, a large set of candidate models was created systematically by combining multiple feasible adsorption mechanisms. Then, a parameter estimation workflow was performed using three different objective functions with increased complexity. Finally, a model reconciliation step was executed and a quality assessment was done for creating a unified robust model with a high degree of validity. As a result of this method, an NH3 adsorption model with five adsorption sites with different mechanisms was obtained that captures the main features from the experimental data. Furthermore, the model parameters have physical significance and relate to the adsorption strength and spatial arrangement for NH3 and water molecules. The proposed model can be used in the development of transient models with increased validity over a wide experimental region.
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