不同超稳Y沸石的酸性质及其催化性能

Acidic and Catalytic Properties of Dealuminated Y Zeolites with Different Preparation Methods

用NH_3-TPD、FTIR和脉冲微反技术,以正庚烷.正十六烷和α-甲基萘三种探针反应研究了不同超稳化方法对Y沸石酸性质和催化性能的影响,并与各超稳Y沸石的骨架铝(N_(Al))_F和非骨架铝(N_(Al))_(EF)相关联,发现,B酸和L酸量均与(N_(Al))_F有关,而与(N_(Al))_(EF)无关;除SSY外,三探针反应在USY,US-SSY和DAY上的裂解活性与(N_(Al))_F,B酸量有关,但并非线性关系,SSY的B酸量最多,酸性最强.但其活性最小.值得注意的是三探针反应的裂解活性与(N_(Al))_(EF)呈很好的线性关系,但DAY例外,它的非骨架铝含量最高,但其活性最低.对SSY和DAY的例外结果亦进行了讨论.

The NH3-TPD, FT-IR and the pulse microreactor techniques were used to study the influence of different methods of dealumination on the acidic and catalytic properties of Y zeolites. The cracking of n-heptane, n-hexadecane and α-methyl-naphthalene were chosen as the probe reactions. The acidic and catalytic properties were related to the framework aluminium (NA1)Fand the extra framework composition (NA1)EF. It was found that both Bronsted and Lewis acid sites correspond to (NAI)F instead of (NAl)EF. Apart from SSY(treated by (NH4)2SiF6), the activities of cracking reactions for three probe reactions on USY( deep-bed calcination), US-SSY(SSY further treated by steam) and DAY (deep-bed calcination and then extraction by acid) are related to the (NAl)For the number of Bronsted acid sites, but not linearly. The amount and strength of the Bronsted acid sites of SSY are the largest as well as the strongest, but its activity is the lowest. It is worth noting that the plot of cracking activity of the three probe reactions on SSY, USY, US-SSY against (NAl)EFis a good straight line. However, for DAY, its amount of (NAl)EFis the largest among the four dealuminated Y zeolites,but its activity is the lowest. The reason for these results is also discussed.