Calcium/strontium chloride impregnated zeolite A and X granules as optimized ammonia sorbents.

Calcium chloride (CaCl 2 ) impregnated zeolite A and strontium chloride (SrCl 2 ) impregnated zeolite A and X composite granules were evaluated as ammonia sorbents for automotive selective catalytic reduction systems. The SrCl 2 -impregnated zeolite A granules showed a 14% increase in ammonia uptake capacity (8.39 mmol g -1 ) compared to zeolite A granules (7.38 mmol g -1 ). Furthermore, composite granules showed 243% faster kinetics of ammonia sorption (0.24 mmol g -1 min -1 ) compared to SrCl 2 (0.07 mmol g -1 min -1 ) in the first 20 min. The composite CaCl 2 /SrCl 2 impregnated zeolite A granules combined the advantages of the zeolites and CaCl 2 /SrCl 2 , where the rapid physisorption from zeolites can reduce the ammonia loading and release time, and chemisorption from the CaCl 2 /SrCl 2 offers abundant ammonia capacity. Moreover, by optimizing the content of SrCl 2 loading, the composite granules maintained the granular form with a crushing load of 17 N per granule after ammonia sorption-desorption cycles. Such structurally stable composite sorbents offer an opportunity for fast ammonia loading/release in automotive selective catalytic reduction systems.