Yanfang Fan

Aminosilane-Grafted Polymer/Silica Hollow Fiber Adsorbents for CO2 Capture from Flue Gas

Amine/silica/polymer composite hollow fiber adsorbents are produced using a novel reactive post-spinning infusion technique, and the obtained fibers are shown to capture CO2 from simulated flue gas. The post-spinning infusion technique allows for functionalization of polymer/silica hollow fibers with different types of amines during the solvent exchange step after fiber spinning. The post-spinning infusion of 3-aminopropyltrimethoxysilane (APS) into mesoporous silica/cellulose acetate hollow fibers is demonstrated here, and the materials are compared with hollow fibers infused with poly(ethyleneimine) (PEI). This approach results in silica/polymer composite fibers with good amine distribution and accessibility, as well as adequate porosity retained within the fibers to facilitate rapid mass transfer and adsorption kinetics. The CO2 adsorption capacities for the APS-infused hollow fibers are shown to be comparable to those of amine powders with similar amine loadings. In contrast, fibers that are spun with presynthesized, amine-loaded mesoporous silica powders show negligible CO2 uptake and low amine loadings because of loss of amines from the silica materials during the fiber spinning process. Aminosilica powders are shown to be more hydrophilic than the corresponding amine containing composite hollow fibers, the bare polymer as well as silica support. Both the PEI-infused and APS-infused fibers demonstrate reduced CO2 adsorption upon elevating the temperature from 35 to 80 °C, in accordance with thermodynamics, whereas PEI-infused powders show increased CO2 uptake over that temperature range because of competing diffusional and thermodynamic effects. The CO2 adsorption kinetics as probed via TGA show that the APS-infused hollow fiber adsorbents have more rapid uptake kinetics than their aminosilica powder analogues. The adsorption performance of the functionalized hollow fibers is also assessed in CO2 breakthrough experiments. The breakthrough results show a sharp CO2 front for APS-grafted fibers, indicating fast kinetics with comparable pseudo-equilibrium capacities to the CO2 equilibrium capacities measured via thermogravimetric analysis (TGA). The results indicate the post-spinning infusion method provides a new platform for synthesizing composite polymer/silica/amine fibers that may facilitate the ultimate scale-up of practical fiber adsorbents for flue gas CO2 capture applications.

Poly(amide-imide)/Silica Supported PEI Hollow Fiber Sorbents for Postcombustion CO2 Capture by RTSA

Amine-loaded poly(amide-imide) (PAI)/silica hollow fiber sorbents are created and used in a rapid temperature swing adsorption (RTSA) system for CO2 capture under simulated postcombustion flue gas conditions. Poly(ethylenimine) (PEI) is infused into the PAI/mesoporous silica hollow fiber sorbents during fiber solvent exchange steps after fiber spinning. A lumen-side barrier layer is also successfully formed on the bore side of PAI/silica hollow fiber sorbents by using a mixture of Neoprene with cross-linking agents in a post-treatment process. The amine loaded fibers are tested in shell-and-tube modules by exposure on the shell side at 1 atm and 35 °C to simulated flue gas with an inert tracer (14 mol % CO2, 72 mol % N2, and 14 mol % He, at 100% relative humidity (RH)). The fibers show a breakthrough CO2 capacity of 0.85 mmol/g-fiber and a pseudoequilibrium CO2 uptake of 1.19 mmol/g-fiber. When tested in the temperature range of 35-75 °C, the PAI/silica/PEI fiber sorbents show a maximum CO2 capacity at 65 °C, owing to a trade-off between thermodynamic and kinetic factors. To overcome mass transfer limitations in rigidified PEI infused in the silica, an alternate PEI infusion method using a glycerol/PEI/methanol mixture is developed, and the CO2 sorption performance is improved significantly, effectively doubling the functional sorption capacity. Specifically, the glycerol-plasticized sorbents are found to have a breakthrough and equilibrium CO2 capacity of 1.3 and 2.0 mmol/g of dry fiber sorbent at 35 °C, respectively. Thus, this work demonstrates two PAI-based sorbents that are optimized for different sorption conditions with the PAI/silica/PEI sorbents operating effectively at 65 °C and the PAI/silica/PEI-glycerol sorbents operating well at 35 °C with significantly improved sorption capacity.

Bayesian estimation of parametric uncertainties, quantification and reduction using optimal design of experiments for CO 2 adsorption on amine sorbents

Abstract Uncertainty quantification plays a significant role in establishing reliability of mathematical models, while applying to process optimization or technology feasibility studies. Uncertainties, in general, could occur either in mathematical model or in model parameters. In this work, process of CO2 adsorption on amine sorbents, which are loaded in hollow fibers is studied to quantify the impact of uncertainties in the adsorption isotherm parameters on the model prediction. The process design variable that is most closely related to the process economics is the CO2 sorption capacity, whose uncertainty is investigated. We apply Bayesian analysis and determine a utility function surface corresponding to the value of information gained by the respective experimental design point. It is demonstrated that performing an experiment at a condition with a higher utility has a higher reduction of design variable prediction uncertainty compared to choosing a design point at a lower utility.

Rapid Temperature Swing Adsorption using Polymeric/Supported Amine Hollow Fibers

This project is a bench-scale, post-combustion capture project carried out at Georgia Tech (GT) with support and collaboration with GE, Algenol Biofuels, Southern Company and subcontract to Trimeric Corporation. The focus of the project is to develop a process based on composite amine-functionalized oxide / polymer hollow fibers for use as contactors in a rapid temperature swing adsorption post-combustion carbon dioxide capture process. The hollow fiber morphology allows coupling of efficient heat transfer with effective gas contacting, potentially giving lower parasitic loads on the power plant compared to traditional contacting strategies using solid sorbents.