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Japanese government declared a goal to reduce CO 2 emissions to half of those in 2005 as the objective “Cool Earth 50”. One promising means of reducing CO 2 emission is the development of integrated coal gasification combined cycle with CO 2 capture & storage (IGCC-CCS). In the IGCC-CCS process, CO 2 separation membranes will play an important role for reducing CO 2 capture costs. Estimates indicated that the CO 2 capture cost from a pressurized gas stream using a membrane would be 1,500 JPY/ton- CO 2 or less. We are currently developing CO 2 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 CO 2 , which acts as a gate to block the passage of other gases. Consequently, the amount of H 2 permeating to the permeate side of the membrane is greatly limited and high concentrations of CO 2 can be obtained. Poly(amidoamine)(PAMAM) dendrimers, candidate materials for molecular gate membranes, shows high separation performance in separation of CO 2 /N 2 and CO 2 /H 2 . In RITE, PAMAM dendrimer/polymer hybrid membranes were developed for CO 2 separation from flue gas (CO 2 /N 2 ) and from IGCC process (CO 2 /H 2 ). Although dendrimer itself is viscous liquid, the dendrimer/polymer hybrid membranes are stable under pressure difference conditions, and thus suitable for practical use. The CO 2 /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 CO 2 capture. Based on these materials, modification of membrane materials is ongoing to improve CO 2 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.

The COCS (Cost Saving CO2 Capture System) Project had been carried out by RITE in collaboration with four Japanese companies from April 2004 to March 2009. It was the R&D project to reduce CO2 capture cost by half compared to the cost of a conventional technology for CO2 removal from a blast furnace gas in an integrated steel works. One of the main research issues in this project was to develop a novel absorbent which could be regenerated with a low thermal energy. RITE especially led the development of new absorbents. Initially amine solvents were investigated through laboratory-scale experiments, and then some selected solvents were evaluated at the 1t-CO2/d test plant. RITE successfully developed innovative amine absorbents, which have high absorption rate and low desorption energy of about 2.5–2.65 GJ/t-CO2 for CO2 capture from a blast furnace gas.

In the framework of the COCS (Cost Saving CO 2 Capture System) project we continue to develop high performance CO 2 absorbents to reduce the regeneration energy cost to almost half the current cost. To achieve this target we investigated twenty five tertiary amine based CO 2 absorbents with different chemical structures. Solvent selection procedures were carried out based on their CO 2 absorption rate, loading capacity and heat of reaction measurements. We found several high performance absorbents with advantages of high absorption rate and low heats of reaction compared to MDEA.