MECHANISM OF PREFERENTIAL CO_2 PERMEATION OF AMINE-CONTAINING POLYMERIC MEMBRANE

摘要

H_2 is industrially produced by steam reforming and following water-gas shift reaction of light hydrocarbons in Japan. This process emits CO_2 but can be carbon-free, if CO_2 in the off-gas is separated over H_2 after H_2 purification by pressure-swing adsorption. We have developed polymeric membranes containing various amines including poly(amidoamine)s (PAMAMs) for preferential CO_2 permeation over H_2. [1-4]. The PAMAM immobilized membranes show excellent CO_2 separation properties in the separation. However, the CO_2 permeability of the polymeric membranes should be elevated for implementation of the membrane, for example, from 5 (current) to 30 GPU in CO_2 capture at on-site H_2 station. Recently, we found that alkanolamines, such as (2-aminoethyl)ethanolamine (AEEA), exhibit higher CO_2 separation properties than PAMAM in the same polymeric matrices. Hydroxyl group adjacent to amino group forms hydrogen bonding to CO_2 in the interaction between amine and CO_2, which reduces the interaction and/or dissociation energy to facilitate CO_2 diffusion in the membrane. In this presentation, immobilization of various alkanolamines in poly(vinyl alcohol) (PVA) matrix was studied to formulate polymeric membranes, and the CO_2 separation performance was examined. The mechanism of preferential CO_2 permeation of the amine-containing PVA membranes will be discussed.