CeO_(2)-WO_(3)/TiO_(2)同时催化脱除氮氧化物与氯苯研究

Synergistic catalytic removal of nitrogen oxides and chlorobenzene by CeO_(2)-WO_(3)/TiO_(2)

氯苯(CB)和氮氧化物(NO_(x))作为恶化大气质量的主要原因,已成为新时期大气污染治理的重点。V_(2)O_(5)/TiO_(2)催化剂虽然能够催化还原NO_(x)和催化氧化CB,但其活性温度窗口重合区间较窄。为此,通过浸渍法制备了CeO_(2)-WO_(3)/TiO_(2)催化剂,考察了焙烧温度对催化性能的影响,以及催化剂在250~550℃同时脱硝脱氯苯的性能。结果表明:高温焙烧会促进TiO_(2)由锐钛矿相向金红石相转变,降低比表面积、表面酸量以及氧化还原性能,这会严重降低催化剂活性;CW/T-600催化剂由于具有优异的氧化还原性能、大的比表面积、丰富的表面酸性位点,使其在同时脱硝脱氯苯反应中具有优异的性能;选择性催化还原(SCR)反应中NH_(4)^(+)和-NH_(2)是主要的氨物种,而-NO_(2)是主要的NO吸附物种,因此SCR在CW/T-600催化剂上的反应遵循L-H机理;催化降解氯苯时醌类、酚类以及乙酸盐型羧酸盐是主要的中间物种。

Chlorobenzene(CB)and nitrogen oxides(NO_(x))are the main reasons for deteriorating air quality and become the focus of air pollution control in the new era.Although the V_(2)O_(5)/TiO_(2) catalyst can catalytically reduce NO_(x) and oxidize CB,its active temperature window overlaps in a narrow range.In this paper,the CeO_(2)-WO_(3)/TiO_(2)catalyst was prepared by impregnation method,and the effect of calcination temperature on the catalytic performance,as well as the performance of the catalyst for synergistic removal of NO_(x) and CB at 250~550℃ were investigated.The results showed that,high temperature calcination promoted the transformation of TiO_(2) from anatase phase to rutile phase,reduced the specific surface area,surface acid content and redox performance,which seriously reduced the catalyst activity.CW/T-600 catalyst had excellent redox performance,large specific surface area and abundant surface acidic sites,so it exhibited excellent performance for synergistic removal of NO_(x) and chlorobenzene.At the same time,NH_(4)+and-NH_(2) were the main ammonia species in theselective catalytic reaction(SCR),and-NO_(2) was the main NO adsorption species,so the reaction on the CW/T-600 catalyst followed the L-H mechanism.Quinones,phenols and acetate-type carboxylates were the main intermediate species in the catalytic degradation of chlorobenzene.