微孔材料BET比表面积计算中相对压力应用范围的研究

考察在不同相对压力范围应用BET公式计算中孔材料、含少量微孔材料及纯微孔材料的表面积，结果表明，应用BET公式计算微孔材料的表面积时，相对压力取值0.01～0.10，BET线性关系较为合理。多数微孔材料相对压力取值在005～020计算出的表面积比0.01～0.10小。有少量的分子筛样品经水热老化处理后，其等温线产生低压滞后环，这类微孔材料在相对压力取值为0.05～0.20计算的表面积比0.01～0.10大。催化剂中微孔材料含量越多，两个相对压力范围内计算出的结果差别越大，对于纯分子筛样品二者差值可达15%左右。

Calculation of BET surface area of microporous materials at different relative pressure

BET equation was used to calculate surface area of different powder solids,such as mesoporous Al_2O_3 and microporous zeolites,at different relative pressure(P/P_0).The results showed that when relative pressure is in the range of 0.01-0.10,surface area of microporous materials calculated is more reliable.For most microporous materials,BET surface area calculated at P/P_0=0.05-0.20 is less than that at P/P_0=0.01-0.10.For some hydrothermally-treated ZSM-5 samples,their isotherms have hysteresis loop at lower relative pressure;BET surface area calculated at P/P_0=0.05-0.20 is smaller that that calculated at P/P_0=0.01-0.10.The more microporous material in the catalysts,the larger the difference in BET surface area calculated at the two relative pressure ranges.For some pure zeolites,this difference can be up to 15%.