Robert James Perry

A Computational Study of the Heats of Reaction of Substituted Monoethanolamine with CO2

Various amines have been considered as materials for chemical capture of CO(2) through liquid-phase reactions to form either carbamate or carbamic acid products. One of the main challenges in these CO(2)-amine reactions lies in tuning the heat of reaction to achieve the correct balance between the extent of reaction and the energy cost for regeneration. In this work, we use a computational approach to study the effect of substitution on the heats of reaction of monoethanolamine (MEA). We use ab initio methods at the MP2/aug-cc-pVDZ level, coupled with geometries generated from B3LYP/6-311++G(d,p) density functional theory along with the conductor-like polarizable continuum model to compute the heats of reaction. We consider two possible reaction products: carbamate, having a 2:1 amine:CO(2) reaction stoichiometry, and carbamic acid, having a 1:1 stoichiometry. We have considered CH(3), NH(2), OH, OCH(3), and F substitution groups at both the α- and β-carbon positions of MEA. We have experimentally measured heats of reaction for MEA and both α- and β-CH(3)-substituted MEA to test the predictions of our model. We find quantitative agreement between the predictions and experiments. We have also computed the relative basicities of the substituted amines and found that the heats of reaction for both carbamate and carbamic acid products are linearly correlated with the computed relative basicities. Weaker basicities result in less exothermic heats of reaction. Heats of reaction for carbamates are much more sensitive to changes in basicity than those for carbamic acids. This leads to a crossover in the heat of reaction so that carbamic acid formation becomes thermodynamically favored over carbamate formation for the weakest basicities. This provides a method for tuning the reaction stoichiometry from 2:1 to 1:1.

Aminosilicone Solvents for CO2 Capture

This work describes the first report of the use of an aminosilicone solvent mix for the capture of CO(2). To maintain a liquid state, a hydroxyether co-solvent was employed which allowed enhanced physisorption of CO(2) in the solvent mixture. Regeneration of the capture solvent system was demonstrated over 6 cycles and absorption isotherms indicate a 25-50 % increase in dynamic CO(2) capacity over 30 % MEA. In addition, proof of concept for continuous CO(2) absorption was verified. Additionally, modeling to predict heats of reaction of aminosilicone solvents with CO(2) was in good agreement with experimental results.

Organosilicon Fragrance Carriers

Five different organosilicon carriers, with various molecular architectures - [(poly-(dimethylsiloxane-co- methylsiloxane) (containing 61 % of [–SiMeHO-] monomeric units) (P), silicone resin (Q), tetramethyldisiloxane (M) tetramethylcyclotetrasiloxane (D) and tris (dimethylsilyl)methane [HC(SiMe2H)3, (T)] were covalently bonded with model fragrant systems, including 1- and 2-phenylethyl alcohol, acetophenone, 2-phenylpropionic aldehyde, geraniol, 2-phenyl-1-propyl alcohol, 2-octanone and octyl aldehyde in order to obtain novel controlled fragrance release systems. Hydrolytic release of the fragrances was studied under base (NaOH) and acid (HCl) catalysis. It has been shown that polymer carriers allow for a controlled slow release of the relevant fragrant ingredients from the conjugates, whereas the low molecular weight systems (M, D and T) more easily cleave off fragrant moieties.

Novel High Capacity Oligomers for Low Cost CO2 Capture

The novel concept of using a molecule possessing both physi-sorbing and chemi-sorbing properties for post-combustion CO2 capture was explored and mixtures of aminosilicones and hydroxyterminated polyethers had the best performance characteristics of materials examined. The optimal solvent composition was a 60/40 blend of GAP-1/TEG and a continuous bench-top absorption/desorption unit was constructed and operated. Plant and process models were developed for this new system based on an existing coal-fired power plant and data from the laboratory experiments were used to calculate an overall COE for a coal-fired power plant fitted with this capture technology. A reduction in energy penalty, from 30% to 18%, versus an optimized 30% MEA capture system was calculated with a concomitant COE decrease from 73% to 41% for the new aminosilicone solvent system.

Carbon dioxide-in-oil emulsions stabilized with silicone-alkyl surfactants for waterless hydraulic fracturing

The design of surfactants for CO2/oil emulsions has been elusive given the low CO2-oil interfacial tension, and consequently, low driving force for surfactant adsorption. Our hypothesis is that waterless, high pressure CO2/oil emulsions can be stabilized by hydrophobic comb polymer surfactants that adsorb at the interface and sterically stabilize the CO2 droplets. The emulsions were formed by mixing with an impeller or by co-injecting CO2 and oil through a beadpack (CO2 volume fractions (ϕ) of 0.50-0.90). Emulsions were generated with comb polymer surfactants with a polydimethylsiloxane (PDMS) backbone and pendant linear alkyl chains. The C30 alkyl chains are CO2-insoluble but oil soluble (oleophilic), whereas PDMS with more than 50 repeat units is CO2-philic but only partially oleophilic. The adsorbed surfactants sterically stabilized CO2 droplets against Ostwald ripening and coalescence. The optimum surfactant adsorption was obtained with a PDMS degree of polymerization of ∼88 and seven C30 side chains. The emulsion apparent viscosity reached 18 cP at a ϕ of 0.70, several orders of magnitude higher than the viscosity of pure CO2, with CO2 droplets in the 10-150 µm range. These environmentally benign waterless emulsions are of interest for hydraulic fracturing, especially in water-sensitive formations.