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用柠檬酸溶胶-凝胶法制备了La0.8M0.2CoO(3M=Sr,Ce,Ba,Ca)4种钙钛矿型复合氧化物催化剂。通入相对湿度为70%的甲苯测试表明,相比较于没有水蒸气存在的情况,4种催化剂的催化活性都有所下降。同时还可发现,A位部分取代的离子不同,催化剂的催化活性下降程度不同,即抗水蒸气性能也不同。所制备的四种催化剂的抗水蒸气性能依次为La0.8Sr0.2CoO3>La0.8Ce0.2CoO3≈La0.8Ca0.2CoO3>La0.8Ba0.2CoO3,其ΔT50%分别为12℃、20℃、20℃和50℃左右,说明除La0.8Ba0.2CoO3外,其它3种对水蒸气具有一定的抗中毒性能。XRD、BET和SEM表征结果证实,水蒸气分子与甲苯分子竞争吸附占据催化剂表面部分活性位,使用于催化氧化甲苯的有效活性位相对减少;同时其与活性组分在高温下发生反应生成新物质,在催化剂表面形成一层致密的涂层,堵塞了原来的孔道结构,从而使催化剂比表面积减少而活性下降。
Four types of perovskite-type composite oxide catalysts La0.8M0.2CoO (3M = Sr, Ce, Ba, Ca) were prepared by citric acid sol-gel method. Toluene access to 70% relative humidity showed that the catalytic activity of the four catalysts decreased compared to the absence of water vapor. At the same time, it can also be found that the partial substitution of ions in A site is different, and the catalytic activity of the catalyst is decreased to a different extent, that is, the properties of resistance to water vapor are also different. The water vapor resistance of the prepared four catalysts were La0.8Sr0.2CoO3> La0.8Ce0.2CoO3≈La0.8Ca0.2CoO3> La0.8Ba0.2CoO3, the ΔT50% of which was 12 ° C, 20 ° C, 20 ° C And about 50 ℃, indicating that in addition to La0.8Ba0.2CoO3, the other three have certain anti-toxic to water vapor. XRD, BET and SEM characterization confirmed that water vapor molecules competed with toluene molecules to occupy some active sites on the catalyst surface, and the effective active sites for the catalytic oxidation of toluene were relatively reduced. At the same time, the active components reacts with the active components at high temperature to generate new substances , Forming a dense coating on the surface of the catalyst, blocking the original pore structure, thereby decreasing the specific surface area of the catalyst and reducing the activity.