A Hybrid experimental and theoretical investigation into the multi-component gas adsorption properties of selected porous materials
| dc.contributor.advisor | Esterhuysen, Catharine | en_ZA |
| dc.contributor.author | Costandius, Jan | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. | en_ZA |
| dc.date.accessioned | 2021-05-06T07:01:01Z | |
| dc.date.available | 2021-05-06T07:01:01Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The importance of advancements in multi-component gas adsorption (MGA) techniques, with respect to combating climate change, is that these methods can help treat the problem at the cause: selective capture of CO2 from mixtures of gases. Unfortunately, new MGA techniques are rarely developed, because the experimental and theoretical methods are much more complex than the single-component gas adsorption (SGA) alternatives. Consequently, most research is focused on studying the SGA properties of novel CO2 adsorbers, while the MGA properties of these materials are often only investigated briefly, predicted qualitatively, or overlooked entirely. This offers an opportunity to develop new experimental and theoretical MGA techniques, such as those presented in this study. Furthermore, by virtue of simply studying the MGA properties of some adsorbents comprehensively, a new predictive method for MGA was developed and new insights were gathered about the cause of ideal vs. non-ideal adsorption. The development of a new volumetric MGA method is reported in the first section of this study. The design of the method is discussed and the benchmarking of the instrument against previously published SGA data is shown. The MGA equilibria of CO2 and N2, when adsorbed by zeolite 13X, are reported. These data are compared to the results of the predictive ideal adsorbed solution theory (IAST) method, where it is found that IAST performs well with predicting the uptake of CO2 but fails to correctly predict the uptake of N2. Additionally, an empirical model, namely the extended Sips isotherm, performs surprisingly well with predicting the mixed uptakes of both CO2 and N2 accurately around 1 bar, where IAST does not. Using the findings of the first section as inspiration, the extended Sips is utilized alongside the non-ideal (real) case of the adsorbed solution theory (RAST), to create a new predictive MGA method named PRAST-S. This method is used to predict the mixed uptakes of CO2 and N2 by Cu-HKUST-1, Mg-MOF-74, MOF-14, and UiO-66. Furthermore, the MGA equilibria of CO2 and N2 obtained using the instrument described in the first section are also reported for Cu-HKUST-1 to confirm that PRAST-S correctly predicts the adsorbed amounts. However, what was not anticipated was that the experimental measurements and PRAST-S prediction both show that Cu-HKUST-1 exhibits ideal adsorption of CO2 and N2. This is in contrast with the other materials studied, which all exhibit non-ideal adsorption. A series of in silico simulations of CO2 and N2 within the pores of 13X and Cu-HKUST-1 to probe the differences in ideal and non-ideal behavior shows that a sudden shift in the mean interaction energy upon mixing is the telltale sign of non-ideal adsorption. Furthermore, the mechanism that led to the shift in the mean interaction energy – or the lack thereof, in the ideal cases – is shown to be dependent on the mode with which the adsorbates interact with the adsorbent. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Klimaatsverandering kan bestry word deur multi-komponent gas adsorpsie (MGA) tegnieke te verbeter, omdat hierdie tegnieke gebruik kan word om materiale wat CO2 selektief uit gasmengsels adsorbeer in diepte te bestudeer. Ongelukkig word nuwe tegnieke – wat gebruik kan word vir die bestudering van gasmengseladsorpsie – selde ontwikkel, omdat hierdie tegnieke meer kompleks is as die tegnieke wat gebruik word om die adsorpsie van enkele gasse te bestudeer. Meeste navorsing fokus gevolglik slegs op die ondersoek van die adsorpsie van enkele gasse, terwyl die adsorpsie van gasmengsels hoofsaaklik geïgnoreer word. Daarom word nuwe eksperimentele- and teoretiese tegnieke ontwikkel in hierdie studie. Alhoewel hierdie studie hoofsaaklik fokus op die ontwikkeling van nuwe tegnieke, is 'n nuwe voorspellingsmodel ook ontwikkel wat gelei het tot nuwe insigte ten opsigte van ideale en nie-ideale adsorpsie. 'n Nuwe volumetriese tegniek vir gasmengsels is in die eerste afdeling van hierdie studie gerapporteer. Die ontwerp van die instrument en die relavante maatstaftoetse is bespreek aan die hand van data wat voorheen gepubliseer was. Die adsorpsieëwewigte van CO2 en N2 is gemeet vir seoliet 13X. Die ideale adsorbeerde- oplossingsteorie kan die adsorpsie van CO2 in die teenwoordigheid van N2 voorspel, maar kan nie die adsorpsie van N2 in die teenwoordigheid van CO2 korrek voorspel nie. 'n Onverwagse ontdekking is gemaak: 'n eenvoudige empiriese model, naamlik die uitgebreide Sips isoterm, het die adsorpsie van beide CO2 en N2 rondom atmosferiese druk korrek voorspel. Die ontdekkings in die eerste afdeling van hierdie studie, is gebruik as die inspirasie agter die volgende studie: om die uitgebreide Sips isoterm te kombineer met die nie-ideale adsorbeerde-oplossingteorie om 'n nuwe voorspellingsmetode te ontwikkel (PRAST-S) vir die adsorpsie van gasmengsels. PRAST-S is gebruik om die opname van mengsels van CO2 en N2 deur Cu-HKUST-1, Mg-MOF-74, MOF-14, en UiO-66 te voorspel. Die instrument wat in afdeling een ontwikkel is, is gebruik om te bevestig dat MGA adsorpsie van CO2 en N2 deur Cu-HKUST-1 akkuraat deur PRAST-S voorspel is. 'n Onverwagse ontdekking is wel gemaak: die opname van mengsels van CO2 en N2 is ideaal wanneer hulle deur Cu-HKUST-1 geadsorbeer is. Hierdie is in teenoorstelling met die ander stowwe bestudeer wat almal nie-ideale adsorpsie toon. 'n Reeks rekenaar-gebaseerde berekeninge van CO2 en N2 in die poriëe van 13X en Cu-HKUST-1 is uitgevoer om die verskille tussen die ideale- en nie-idealegedrag te bestudeer. Dit is ontdek dat nie-ideale adsorpsie gepaard gaan met 'n skielike verandering in die gemiddelde interaksieënergie tussen 'n gasspesie en die adsorberende materiaal, indien die gasspesie met 'n tweede gasspesie gemeng word. 'n Verdere ontdekking is dat die meganisme wat lei tot hierdie versteuring in die gemiddelde interaksieënergie van die interaksiemodes tussen die gasspesies en die adsorberende materiaal afhang. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | 154 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110449 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Combating climate change | en_ZA |
| dc.subject | Porous materials | en_ZA |
| dc.subject | Adsorption -- Properties | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | A Hybrid experimental and theoretical investigation into the multi-component gas adsorption properties of selected porous materials | en_ZA |
| dc.type | Thesis | en_ZA |