Use of multifunctional nanoporous TiO(OH) 2 for catalytic NaHCO 3 decomposition-eventually for Na 2CO 3/NaHCO 3 based CO 2 separation technology

Abstract

In general, CO 2 capture from flue gas is a costly procedure, usually due to the energy required for regeneration of the capture medium. One potential medium which could reduce such an energy consumption, however, is Na 2CO 3. It has been well studied as a sorbent, and it is understood that the theoretical energy penalty of use of Na 2CO 3 for CO 2 separation is low, due to the relatively low heat of reaction and low heat capacity of the material. While it offers some advantages over other methods, its primary downfall is the slow reaction with CO 2 during adsorption and the slow Na 2CO 3 regeneration process. In an effort to reduce the energy penalty of post-combustion CO 2 capture, the catalytic decomposition of NaHCO 3 is studied. Nanoporous TiO(OH) 2 is examined as a potential catalytic support for a cyclic Na 2CO 3/NaHCO 3 based CO 2 capture process. FT-IR, SEM, and XRD characterization of NaHCO 3 supported on nanoporous TiO(OH) 2 treated with different processes indicate that TiO(OH) 2 is stable within the temperature range necessary for such a process, up to about 200 °C. More importantly, the TiO(OH) 2 has a catalytic effect on the decomposition of NaHCO 3, reducing the activation energy from about 80 to 36 kJ/mol. This significant drop in activation energy could translate into a much lower operating cost for regenerating Na 2CO 3. The reaction rate of NaHCO 3 decomposition, or CO 2 desorption, is observed to increase by as much as a factor of ten due to this decrease in activation energy.