posted on 2021-01-21, 17:08authored byJianzhou Wu, Kaimin Du, Jianwei Che, Shihui Zou, Liping Xiao, Hisayoshi Kobayashi, Jie Fan
The
treatment of lean methane from sulfur-containing exhausts of
natural gas vehicles is important, but challenging, because of the
strong and irreversible catalyst poisoning by sulfur species. Herein,
sulfur-tolerance enhanced NiO nanocatalysts (NiO-SPP) are prepared
via surface polymeric phosphate (SPP) modification of NiO NPs, and
a self-catalyzed sulfation (SCS) mechanism is proposed to reveal the
insights on the boosted sulfur-tolerance capacity. In the SCS mechanism,
the sulfation process is divided into two steps, namely, (1) the initial
sulfation process and (2) the self-catalyzed sulfation process accelerated
by previously formed sulfates. Stability and durability tests of NiO
NPs and NiO-SPP reveal that the improved sulfur-tolerance capacity
via SPP modification should be attributed to two reasons, namely,
the external reason as the protection on the surface structure of
NiO-SPP, and the internal reason as the deceleration of the initial
sulfation rate. Specifically, characterizations and analyses of the
catalysts before and after stability tests indicate that the SPP modification
could efficiently cut down the interaction possibility of active sites
with sulfur species. On the basis of the SCS mechanism, the initial
sulfation rate of NiO NPs under long-term deactivation tests is calculated
to be 12.8 times that of NiO-SPP, and the self-catalyzed sulfation
rate constant for NiO NPs is twice that of NiO-SPP. The SPP modification
of catalysts and the SCS mechanism provide a reference for the improvement
of catalyst durability on the perspective of deactivation.