Structure sensitivities of SAPO zeolites on catalytic oxidation of nitric oxide

NO_x emissions from increasing coal consumption associated with ozone depletion, photochemical smog, acid rain, ambient particulate matter and respiratory diseases has triggered global interest in exploring new catalysts and technologies for NO_x abatement. Catalytic NO oxidation combined with subsequent liquid absorption is a possible alternative to current selective catalytic and non-catalytic reduction. Compared to existing abatement strategies, NO oxidation operates at a lower temperature (< 100°C) and can potentially be used for simultaneous control of multiple pollutants. Porous zeolites including SAPO-11 and SAPO-34 as NO oxidation catalysts were investigated. The bench-scale reactor used 2.4 x l0⁴ mL/g-hr, 0.25 g of packed zeolite catalyst, 25 °C, 50 °C, and inlet gases of 380 ppm_v NO, 10 vol % O₂, and balance N₂. At 25 °C, higher conversion efficiency (39.78 ∓ 0.48%) was achieved on SAPO-34 than on SAPO-11 (7.85 ∓ 0.3 3%). At 50°C the conversion efficiency for SAPO-34 was 16.2 ∓ 0.7%, higher than 3.9 ∓ 0.4%. Transient kinetic experiments combined with tests investigating the impacts of pre-sorbed NO_x species showed that the NO oxidation mechanism over zeolite catalysts was consistent with the carbon-catalyzed process. Conversion efficiency of the catalyst was controlled by the catalyst's pore structure, including cavity size and channels. The pore width must be large enough to adsorb NO and formed intermediates, but narrow enough to provide the necessary energy benefits associated with increased adsorption in micropores. This is an abstract of a paper presented at the 106th AWMA Annual Conference and Exhibition (Chicago, IL 6/25-28/2013).