Regulation Of Sulfur Tolerance Of Platinum-based Catalysts For CO Oxidation

Carbon monoxide（CO）is one of the important pollutants in industrial flue gas.With the increasingly stringent emission policy,the emission concentration limits of CO and other pollutants have been reduced,which puts forward higher requirements for the design and preparation of catalysts suitable for CO oxidation elimination in industrial flue gas.Noble metal catalysts have been widely used in the low concentration CO oxidation because of their high activity and stability.Recently,Pt-based catalysts have made great progress in CO oxidation at ambient temperature and humidity.However,Pt-based catalysts are still easily deactivated by residual trace SO₂in industrial flue gas even after desulphurization treatment,which seriously restricts the application of Pt-based catalysts for CO oxidation elimination in industrial flue gas.It is urgent to improve the anti-interference ability such as sulfur tolerance of Pt-based catalysts.In this paper,on the basis of Pt-Fe catalysts with excellent CO oxidation elimination performance developed by our research group,we focused on the effects of SO₂ on the Pt-Fe catalysts.Under the guidance of the obtained information,Pt/Fe₂O₃-Al₂O₃ catalyst with excellent CO catalytic activity,stability and sulfur tolerance was designed.By comparing the structure and surface properties of the catalyst before and after the reaction,the reasons for its outstanding sulfur tolerance was clarified,which provided a reference for the design and development of Pt-based catalysts with high sulfur tolerance for CO oxidation.The specific research contents are as follows:1.The sulfur tolerance of Pt-Fe catalysts including Pt/Fe O_x,Pt/Mg Fe₂O₄ and Pt/Fe O_x/La Fe O₃ with superior CO catalytic activity at ambient temperature and humidity developed by our research group was investigated.These Pt-Fe catalysts showed poor sulfur tolerance and resilience.The catalytic activities of Pt-Fe catalysts were decreased in the presence of SO₂.Moreover,SO₂-poisoned catalysts which were regenerated in a 10%H₂/Ar flow at 200°C for 60 min could not recover the original activity for CO oxidation.The effect of SO₂ on Pt-Fe catalysts was investigated by a series of characterization.When SO₂ contacted with Pt-Fe catalysts,it is adsorbed on the surface of Pt nanoparticles and oxidized to SO₃,which altering the electronic properties of Pt and decreasing the adsorption strength of CO on Pt.At the same time,SO₃ overflows to the support surface and reacts with the iron species to form iron sulfate,which to some extent poisoning the adsorption and activation sites of O₂ and H₂O.These above poisoning behaviors seriously affect the progress of CO oxidation reaction,resulting in irreversible deactivation of Pt-Fe catalysts.2.Fe₂O₃-Al₂O₃ mixed oxide supports were prepared by mechanical grinding assisted sol-gel method.The surface properties of supports were controlled by changing the calcination temperature,and Pt/Fe₂O₃-Al₂O₃ catalysts were synthesized by colloidal deposition method.Pt/Fe₂O₃-Al₂O₃-600 catalyst showed excellent low-temperature CO oxidation activity,stability and sulfur tolerance in the presence of SO₂.Studies have shown that the distribution of iron species on the support surface can be controlled by changing the calcination temperature.The presence of Al₂O₃ in the Fe₂O₃-Al₂O₃-600mixed oxide support inhibits the agglomeration and phase transformation of iron oxide species so that Pt/Fe₂O₃-Al₂O₃-600 catalyst has excellent low-temperature CO oxidation activity.In addition,the presence of highly dispersed Fe₂O₃ species in Fe₂O₃-Al₂O₃-600 mixed oxide support reduces the surface basicity of catalyst,weakening the SO₂ adsorption of on catalyst surface.The formation of surface stable sulfate was blocked,making Pt/Fe₂O₃-Al₂O₃-600 catalyst with excellent sulfur tolerance.