Novel Solid Amine Sorbents and Their Uses in Fluidized-Bed Process for Carbon Dioxide Separation

Arizona State University, Scottsdale AZ

Investigators

Abstract

Abstract The increasing use of fossil fuels to meet energy needs during the past three decades has led to much higher carbon dioxide emissions into the atmosphere. Rising CO2 concentrations have been reported to account for half of the greenhouse effect that causes global warming. It is therefore essential to develop efficient and cost-effective CO2 management schemes to curb its emission into the atmosphere. The very high costs associated with current CO2 separation technologies require research and development of new technologies that will allow for economically acceptable methods for the capture and sequestration of CO2. Because of their unique properties due to their large porosity, open pore structure, very large surface area and very small primary particle size per unit mass, we believe that nanostructured, high surface area, high porosity, aerogels and/or silica nanopowders modified with amine groups will act as efficient super sorbents to separate CO2 from a flue gas stream. The adsorbed CO2 can then be desorbed at higher temperature, so as to regenerate the sorbents so that they can be reused over many cycles. However, no work has been reported on using these types of supports to immobilize amine to act as sorbents for CO2 capture. We also plan to configure the nanostructured sorbents in a micro-jet assisted fluidized bed rather than a packed bed. Using a fluidized bed has many advantages over a packed bed, such as low pressure drop, good mixing, temperature uniformity, continuous powder handling, and higher catalyst or sorbent effectiveness factors, which heretofore have not been utilized because of the difficulty in obtaining smooth, bubble-less fluidization of ultra-fine powders or nanostructured aerogels. Intellectual Merit: The research project will include synthesizing the amine surface-modified aerogels and silica nanopowders using a variety of chemicals with active amine functionalities, either chemically bonded to the support or immobilized within the porous support, and using different coating methods to produce an optimum amine modified sorbent. We will study the amount of amine loading and its interaction with the support by TGA/DSC and FTIR. CO2 adsorption/desorption equilibrium and kinetics on these super sorbents will be studied using a Cahn microbalance. We will then configure the most promising amine modified sorbents, first in a packed bed (for comparison purposes) and then in a fluidized bed, to measure their ability to separate carbon dioxide from simulated flue gas. We will regenerate the sorbents by raising the temperature and determining the effect of cycling the sorbent over many cycles on their adsorption/desorption and stability properties. Modeling will focus on understanding the sorption equilibrium and sorption kinetics of amine modified sorbents and predicting the performance of the fluidized bed under different operating conditions. Broader Impacts: Undergraduate and graduate students working on the research will receive broad education and training in particle technology, nanotechnology, fluidization, separation processes, and environmental science. They will also have an additional advantage of gaining an industrial perspective by interacting with Cabot and AVEKA engineers who have agreed to lend their expertise, and provide guidance and advice to the project. The Co-PIs will serve as guest lecturers in appropriate ASU undergraduate or graduate courses, where they will present different aspects of the research to ASU students in the classroom. The Co-PIs will also strive to target the large ASU undergraduate minority and woman talent pool to join the project as research students. The unique combination of using amine modified, very high surface area, nanostructured aerogels or silica nanopowders rather than micron-sized solid supports with a fluidized bed process is a transformational approach in developing a new technology for the efficient capture of CO2 from flue gas. The existing technologies for CO2 separation from flue gas consume at least 20% of the energy generated by burning coal or natural gas and also involve substantial equipment and operation costs. The successful implementation of the proposed research should offer substantial energy saving for CO2 capture because of improved CO2 sorption capacity, recyclability of the sorbent, reduced pressure drop of the fluidized bed and the ability for continuous operation. It will also serve to increase industry?s awareness of the myriad opportunities that exist for using nanostructured and nano-size particles in unique applications and will contribute to ensuring US competitiveness and technological lead in the area of CO2 capture, the reduction of greenhouse gases, and the preservation of the environment.