Novel High Capacity Oligomers for Low Cost CO2 Capture

Abstract

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. 3 Executive SummaryThe novel concept of using a molecule possessing both physi-sorbing and chemi-sorbing properties for post-combustion CO2 capture was explored. A variety of candidate materials with physi-sorbing backbones and chemically reactive peripheral groups were considered with the final selection primarily focusing on aminosilicones. A small effort was also devoted to derivatized plant oils.None of the plant oil derivatives were effective in absorbing CO2 in laboratory experiments. Model reactions suggest that both intra-molecular H-bonding between adjacent hydroxyl and amino groups and potential micelle formation suppressed reactions with CO2. This route was abandoned in favor of the aminosilicones.A variety of aminosilicones with differing architectures and type and placement of amine groups were examined both experimentally and computationally for physical properties as well as CO2 capture efficacy. Modeling indicated that the heat reaction of sterically hindered amines with CO2 was lower than for unhindered amines and that less basic amines also decreased the heat of reaction. This provided options to tune the heat of reaction for optimal plant performance. Physical property predictions were also made for viscosity, vapor pressure, density and CO2 solubility. Limited experimental data confirmed the accuracy of the density and solubility models as well as trend predictability in heats of reaction. However, viscosity predictions were not accurately modeled and vapor pressure data was unavailable.Synthetically, GEN 1 aminosilicone solvents with linear, branched, cyclic and star architectures were made that possessed mono and di-amine groups while other solvent candidates had varying degrees of steric hindrance. Oligomers as well as discrete small molecules were prepared and evaluated. These included solvents with covalently bound polyether units. CO2-capture experiments were performed using both high throughput screening (HTS) techniques as well as small-scale laboratory testing. Mass transfer issues prevented the HTS methodology from being as useful as anticipated. However, efficient mixing on the lab-scale provided reliable data. These experiment...