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Multiscale modelling of adsorption by MOFs - CO2-separation from flue gas and Olefin/Paraffin-separation as examples
Citation Link: https://doi.org/10.15480/882.3159
Publikationstyp
Doctoral Thesis
Date Issued
2020
Sprache
English
Author(s)
Advisor
Keil, Frerich Johannes
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2020-07-21
Institut
TORE-DOI
TORE-URI
Citation
Technische Universität Hamburg (2020)
A methodology for the design of adsorption processes by a multi-scale approach is developed, using the two separation problems of CO2 sequestration from flue gas and olefin/paraffin-separation as examples for this ansatz.
Out of all greenhouse gases CO2 is emitted the most, in particular from the energy generating industry. Currently, the state-of-the-art technology to remove CO2 from flue gases is amine scrubbing, which has the disadvantage
of high energy consumption because of the solvent regeneration step. The adsorption process is a potential replacement for this technology, using metalorganic frameworks (MOFs) as adsorption material. Mg-MOF-74 has been
identified in the literature as one of the best materials for the removal of CO2 from flue gas because of its open metal sites, which strongly interact with CO2 and water. In order to predict the adsorption accurately in molecular simulations a force field for both species is developed. Adsorption isotherms and self-diffusivity were calculated for each pure component and for mixtures using molecular simulations. We show that in order to use Mg-MOF-74 to its fullest potential, water has to be removed from the system almost completely. Fixed-bed adsorber simulations show as a proof of principle that an adsorption process using Mg-MOF-74 is a promising alternative.
Ethene and propene are the two most important chemical feedstocks for the chemical industry. The separation of those two components from their respective paraffin-counterpart is very difficult because of their similar structure and molecular and thermophysical properties. The state-of-the art process to separate olefin/paraffin-mixtures is the cryogenic distillation, which is carried out at temperatures as low as -100°C, and therefore, has a high energy consumption. The advantage of adsorption processes is that they can run at ambient conditions using MOFs as adsorbent, making it a potential replacement technology. In this work, ZIF-8, ZIF-9, ZIF-71, IFP-1, IFP-3, IFP-5, and IFP-7 are investigated regarding their separation potential for the separation of olefin/paraffin-mixtures. Adsorption isotherms are calculated by molecular simulations and compared to experiments, showing a very good agreement for the C2 and C3 molecules. In most crystals, the selectivity is slightly in favor of the olefin. Diffusion studies show that the flexibility of the frameworks plays an important role during diffusion processes. The simulation of a fixed-bed adsorption process indicates that the separation is feasible with ZIF-8 as adsorption material.
This work demonstrates that the developed methodology can be applied to complex separation problems successfully, modelling the process on an atomistic scale all the way up to an industrial sized fixed-bed apparatus.
Out of all greenhouse gases CO2 is emitted the most, in particular from the energy generating industry. Currently, the state-of-the-art technology to remove CO2 from flue gases is amine scrubbing, which has the disadvantage
of high energy consumption because of the solvent regeneration step. The adsorption process is a potential replacement for this technology, using metalorganic frameworks (MOFs) as adsorption material. Mg-MOF-74 has been
identified in the literature as one of the best materials for the removal of CO2 from flue gas because of its open metal sites, which strongly interact with CO2 and water. In order to predict the adsorption accurately in molecular simulations a force field for both species is developed. Adsorption isotherms and self-diffusivity were calculated for each pure component and for mixtures using molecular simulations. We show that in order to use Mg-MOF-74 to its fullest potential, water has to be removed from the system almost completely. Fixed-bed adsorber simulations show as a proof of principle that an adsorption process using Mg-MOF-74 is a promising alternative.
Ethene and propene are the two most important chemical feedstocks for the chemical industry. The separation of those two components from their respective paraffin-counterpart is very difficult because of their similar structure and molecular and thermophysical properties. The state-of-the art process to separate olefin/paraffin-mixtures is the cryogenic distillation, which is carried out at temperatures as low as -100°C, and therefore, has a high energy consumption. The advantage of adsorption processes is that they can run at ambient conditions using MOFs as adsorbent, making it a potential replacement technology. In this work, ZIF-8, ZIF-9, ZIF-71, IFP-1, IFP-3, IFP-5, and IFP-7 are investigated regarding their separation potential for the separation of olefin/paraffin-mixtures. Adsorption isotherms are calculated by molecular simulations and compared to experiments, showing a very good agreement for the C2 and C3 molecules. In most crystals, the selectivity is slightly in favor of the olefin. Diffusion studies show that the flexibility of the frameworks plays an important role during diffusion processes. The simulation of a fixed-bed adsorption process indicates that the separation is feasible with ZIF-8 as adsorption material.
This work demonstrates that the developed methodology can be applied to complex separation problems successfully, modelling the process on an atomistic scale all the way up to an industrial sized fixed-bed apparatus.
Subjects
molecular simulations
adsorption
Monte Carlo simulation
molecular dynamics
Metal-organic frameworks
DDC Class
540: Chemie
600: Technik
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Dissertation_Stephan_Bendt.pdf
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