硅胶的孔径结构对脱附活化能的影响

Effects of Pore Sizes of Silica Gels on Desorption Activation Energy of Water Vapor

该文为研究硅胶孔结构对水蒸气吸附速率／脱附活化能的影响，在吸附水蒸气动力学实验中采用了间歇式吸附方法，用程序升温脱附技术测定了水在硅胶上的程序升温脱附（TPD）曲线并估算了水的脱附活化能。结果表明：A型、B型和C型硅胶的平均孔径分别为2nm、5．28nm和10．65nm。在10％～45％低湿范围内，硅胶的平均孔径越大，其吸附初始阶段的吸附速率越快，平衡吸湿量越小；高湿度条件下，硅胶的平均孔径和孔容越大，其吸附初始阶段的吸附速率越慢，平衡吸湿量越大。水分子在A型、B型和C型硅胶上的脱附活化能分别为35．54kJ／mol、31．41kJ／mol和26．16kJ/mol，说明水分子在硅胶上的脱附活化能随着硅胶的孔径增加而明显减小。与微孔硅胶相比．在中高湿度下中孔硅胶有较大的平衡吸附量和较低的脱附活化能。

The effects of pore sizes of silica gels on the adsorption rate and the desorption activation energy of water vapor are studied. Kinetic experiments of water vapor adsorption on the silica gels are carried out by the method of static adsorption, and the temperature program desorption （TPD） experiments are conducted to estimate the desorption activation energy of water on silica gels. Results show that the average pore diameter of the A-type, the B-type and the C-type silica gel is separately 2. 06 nm, 5.28 nm and 10.65 nm; at low relative humidity （10% -45%） with the increases of the pore diameter of the silica gel, the adsorption rates increase at the initial stage of the adsorption and the amount of equilibrium adsorption decreases; at high relative humidity, with the increase of the pore diameter of the silica gel,the adsorption rates decrease at the initial stage of the adsorption, the amount of equilibrium amount adsorption increases. The desorption activation energy of water on the A-type, the B-type and the C-type silica gel is respectively 35.54 kJ/mol, 31.41 kJ/mol and 26.16 kJ/mol,which suggestes that the desorption activation energy of the water on the silica gel decreases as its pore diameter increases. At medium and higher relative humidity, the amount of equilibrium adsorption of water becomes larger and the activation energy of the water desorption on the mesoporous silica gel becomes lower in comparison with those on the microporous silica gel.