Role of Al pairs on effective N2O decomposition over the ZSM-5 zeolite catalyst

Series of ZSM-5 zeolites with diverse contents and locations of Al pairs were synthesized, and Co 2+ ions were subsequently anchored at the Al pairs of ZSM-5 zeolites by wet ion-exchange with H protons. The Co-ZSM-5 sample derived from the mixtures of AlCl 3 and TEOS of Si/Al=30.3 showed the best de N 2 O performance. Analysis on Co (Ⅱ) ion exchange capacity demonstrated the content of Al pairs followed the sequence: AlCl 3 (0.84) > Al(NO 3 ) 3 (0.73) > aluminum isopropoxide (0.65) and TEOS (0.84) > silicic acid (0.57). More Al pairs coordinated with protons or cobalt ions were essentially associated with better performances for N 2 O catalytic dissociation. Moreover, Si source had a significant effect on the location of Al pairs determined by UV–vis–DRS of bare Co (Ⅱ), Al pairs of ZSM-5 zeolite synthesized from TEOS were enriched in the sinusoidal channel (γ site), whereas those synthesized from silicic acid were concentrated in the channel intersections (6-MRs β site). The theoretical calculation revealed that the O 2 desorption at γ-site Co 2+ of ZSM-5 zeolite required to overcome less energy barrier (23.8 kcal/mol) than that at β-site one. • Al pairs in ZSM-5 zeolite was well controlled via adjusting precursor sources as well as Si/Al ratio. • The number of Al pairs follows the sequence: AlCl 3 > Al (NO 3 ) 3 > isopropoxide AIP and TEOS > silicic acid. • Al pairs located at γ-site makes a major contribution on deN 2 O with respect to α-or β site. • The best performance is achieved over Co-ZSM-5 derived from AlCl 3 and TEOS with Si/Al = 30.3.