Use of multifunctional nanoporous TiO(OH)2 for catalytic NaHCO3 decomposition-eventually for Na2CO3/NaHCO3 based CO2 separation technology

摘要

In general, CO2 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 Na2CO3. It has been well studied as a sorbent, and it is understood that the theoretical energy penalty of use of Na2CO3 for CO2 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 CO2 during adsorption and the slow Na2CO3 regeneration process. In an effort to reduce the energy penalty of post-combustion CO2 capture, the catalytic decomposition of NaHCO3 is studied. Nanoporous TiO(OH)2 is examined as a potential catalytic support for a cyclic Na2CO3/NaHCO3 based CO2 capture process. FT-IR, SEM, and XRD characterization of NaHCO3 supported on nanoporous TiO(OH)2 treated with different processes indicate that Ti0(0H)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 NaHCO3, 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 Na2CO3. The reaction rate of NaHCO3 decomposition, or CO2 desorption, is observed to increase by as much as a factor of ten due to this decrease in activation energy.