相对压力点的设定对比表面积和孔隙分布测量值的影响

Influence of setting up relative pressure points on measured value of surface area and pore distribution

利用美国康塔Autosorb-1MP分析仪,对果壳活性炭的比表面积和孔隙分布进行了表征。为简化等温吸附脱附线上的数据采集点、减少实验成本和缩短测试时间、提高实验效率,对单点BET法、多点BET法和BJH法的基本理论模型和测试结果两方面进行了对比分析,从测试方法的基理上探究数据采集点的分布和数量对实验结果的影响,得到了简化实验数据点前后最小相对误差下相对压力值的变化规律。结果表明:对于比表面积的测定,取5个分析点时BET直线拟合效果较好,相对压力p/p0为0.20附近时,单点和多点比表面积的相对误差在5%左右,且多点比表面积大于单点比表面积;而对于孔隙分布的分析,当以相对压力小于滞后环始点处p/p0的测试点为BJH脱附分析线的终止点时,对其孔比表面积、孔容和最优孔径的测试值无影响。

Specific surface area（S） and pore distribution of shell activated carbon were tested by U.S.Quantachrome Autosorb 1MP analyzer.To simplify test points of the adsorption and desorption isotherm,reduce the experimental cost,shorten the test time and improve the experimental efficiency,a comparative analysis between the basic theoretical model and the test results was made by the single-point BET method,multipoint BET method and BJH method,the influence of distribution and amount of test points on measured value was studied through fundamental test methods,and the change law of relative pressure points of minimum relative error before and after simplifying test points was found.The results show that to the test of surface area,the BET curve fitting is better with 5 measured points,and the relative error between single-point S and multipoint S is about 5 ％,when P/P0 is set at 0.20,besides,the value of single-point S is higher; on the pore distribution,after considering P/P0 points,which are less than the value of P/P0 of start point of hysteresis loop,as ending point of the BJH desorption curve,the test value of surface area,pore volume and optimal aperture remain relatively unchanged.