Molecular gate membrane: Poly(amidoamine) dendrimer/polymer hybrid membrane modules for CO₂ capture

Japanese government declared a goal to reduce CO₂ emissions to half of those in 2005 as the objective "Cool Earth 50". One promising means of reducing CO₂ emission is the development of integrated coal gasification combined cycle with CO₂ capture & storage (IGCC-CCS). In the IGCC-CCS process, CO₂ separation membranes will play an important role for reducing CO₂ capture costs. Estimates indicated that the CO₂ capture cost from a pressurized gas stream using a membrane would be 1,500 JPY/ton- CO₂ or less. We are currently developing CO₂ molecular gate membrane, with the goal of producing a new, high-performance separation membrane modules. In the concept of the molecular gate membrane, the pathway for gas molecules is occupied solely by CO₂, which acts as a gate to block the passage of other gases. Consequently, the amount of H₂ permeating to the permeate side of the membrane is greatly limited and high concentrations of CO₂ can be obtained. Poly(amidoamine)(PAMAM) dendrimers, candidate materials for molecular gate membranes, shows high separation performance in separation of CO ₂/N₂ and CO₂/H₂. In RITE, PAMAM dendrimer/polymer hybrid membranes were developed for CO₂ separation from flue gas (CO₂/N₂) and from IGCC process (CO ₂/H₂). Although dendrimer itself is viscous liquid, the dendrimer/polymer hybrid membranes are stable under pressure difference conditions, and thus suitable for practical use. The CO₂/H ₂ selectivity of the membrane showed more than 30, which is required to apply membrane modules for IGCC process. From these results, a PAMAM dendrimer/polymer hybrid membrane is a promising candidate for IGCC process with CO₂ capture. Based on these materials, modification of membrane materials is ongoing to improve CO₂ separation performance further. In the development of commercial membrane modules using the PAMAM dendrimer/polymer hybrid materials, RITE, Kuraray Co., Ltd., Nitto Denko Corporation and Nippon Steel Engineering Co., Ltd. established Molecular Gate Membrane module Technology Research Association, and membrane materials, membrane modules and separation systems are being developed with collaboration in the research association.