NOx emitted from diesel engines is one of the major air pollutants in most countries. To reduce NOx emission, NOx storage/reduction (NSR) catalysts have been developed for diesel systems. The catalyst for NSR is strongly poisoned with sulfur. This paper reports the synthesis of Na-doped CaCO3 as a new material for SO2 adsorption. Measurements of the desulfurization breakthrough characteristics using monolith washcoated Na-doped CaCO3 were investigated at 450 degrees C. The Na-doped CaCO3 absorbed similar to 77.6-90.6 mg-SO2/g(-material) of SO2 at 450 degrees C (where CaCO3 is 8 mg-SO2/g(-material)). Investigation of the source of the improved sulfur absorption capacity of the Na-doped CaCO3 relative to the parent material via x-ray diffraction (XRD) and scanning electron microscopy-energy-dispersive x-ray spectroscopy (SEM-EDX) analyses revealed that the new material forms a composite partially composed of Na2Ca(CO3)(2). The enhanced SO2 absorption capacity derived from the formation of composite materials is demonstrated herein. SO2 contained in the exhaust gas is absorbed at a lower temperature than with previously reported systems. In order to elucidate the SO2 absorption mechanism of the composite materials, further studies and synthesis of materials with greater absorption capacity are required.