The objective of this work was to evaluate the fundamentals of the currently available CO2
separation technologies and provide a solution for the efficient capture of carbon dioxide from
various point source emitting industries. In order to realize a robust approach to advancing the
solution to this global issue, the versatility of the process to the range of compounds contained
within the stream(s) to be processed must be maintained.
It is clear that adsorption, membrane, and aqueous amine based processes are all capable.
However, only aqueous amine scrubbing appears economically viable at the current stage of
development. In order to challenge this, and potentially drive the separation costs lower, this
work centered on hybridizing aqueous amine chemistry and dry adsorption based separations to
produce a novel nano-porous material capable of efficient removal of CO2 from flue gas (5%
CO2 balance N2 with moisture).
In order to combine aqueous amine scrubbing with dry adsorption, a few approaches
were considered and evaluated. These included, amine impregnation within the vast pore
volume of PE-MCM-41, surface grafting of various amino silane compounds, and finally, a novel
approach of volume based amine functionalization (3D grafting).
Application of pore-expanded MCM-41 (PE-MCM-41) mesoporous silica coated with
3-[2-(2-aminoethyl-amino)ethylamino]propyltrimethoxysilane (TRI) has been extensively
examined for the adsorption of CO2 from N2. A systematic study of the amine loading as a
function of the relative amounts of TRI and water used during the grafting procedure, and the
temperature of the grafting reaction was carried out. Extremely high levels of active amine
content were achieved using prehydrated silica surfaces at grafting temperatures below reflux in
order to facilitate thermally controlled water-aided surface polymerization of the aminosilanes.
Abstract iii
The CO2 adsorption capacities and rates were determined for all materials as a function
of the amount of TRI and water per gram of support added to the grafting mixture. The optimal
TRI grafted PE-MCM-41 adsorbent exhibited a 2.65 mmol/g adsorption capacity at 25 °C and
1.0 atm for a dry 5% CO2 in N2 feed mixture, which exceeded all literature reported values, for
both meso- and microporous materials under the conditions used in this study. Further, the
apparent adsorption and desorption rates with the amine functionalized materials were
exceedingly high. When considering the grafted amine quantity, the adsorption capacity and rate
were found to be mutually dependent on each other, exhibiting an apparent optimal
combination.
In comparison to zeolite 13X, the optimally loaded TRI-PE-MCM-41 was far superior
in terms of dynamic adsorption and desorption performance. These results were further
enhanced when the adsorbents were challenged with a humid stream of 5% CO2/N2. The TRIPE-MCM-41
exhibited a 10% increase in CO2 adsorption capacity, whereas the 13X zeolite did
not retain any significant CO2 adsorption capacity.
The novel concept of an internally variably staged permeator was introduced. A
theoretical model was developed and used as the basis for simulation studies. The advantage of
the internal variably staged design was shown to permit a very high extent of separation similar
to a two stage permeator for purity, while maintaining similar flux rates as per a single stage
permeator. This IVSP concept has also taken existing membrane materials and mechanically
translated their process performance to a higher level. As such, the unit should prove effective
for front end process stream cleanup requirements prior to an adsorption process with the novel
TRI-PE-MCM-41 nano-porous adsorbent.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/32974 |
| Date | January 2015 |
| Creators | Harlick, Peter |
| Contributors | Tremblay, Andre |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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