Pt and Pt based catalysts are the most commonly used catalysts of this category and shows better results than other noble metal catalysts. Ayastuy et al. [53] used MnOx/Pt/Al2O3 and reported that high CO conversion at high temperature range. Ceria supported Pt with alumina also reported high activity and selectivity for CO-PROX [54-59]. Many works [60-65] have been done over Pt-Fe/mordenite catalysts and concluded that these catalysts gives good result even in presence of H2O. Alkali metal modified catalyst increases the activity but not effect the selectivity of CO-PROX [66]. Guerrero et al. [67] studied the promotional effect of Nb on Pt supported on alumina or on niobia, for the preferential oxidation of CO (PROX) in hydrogen.The results show a unique effect of Nb as a promoter to Pt. At low Nb loadings on Pt/alumina, the CO oxidation activity and selectivity are significantly increased. The CO selectivity is 100% at conversions up to about 60%. Pt-Co silica or alumina aerogel catalyst exhibited excellent ability for the carbon monoxide removal but at comparatively higher temperature [68, 69].