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


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Effects of Pore Sizes of Silica Gels on Desorption Activation Energy of Water Vapor
LI XinLI Zhong
The Key Lab of Enhanced Heat Transfer and Energy Conservation,South China University of Technology,Guangzhou 510640,China
silica gels adso rpt ion k inetics pore sizes w a ter vapor adsorption desorption activat ion energy
The effects of pore sizes o f silica ge ls on the adso rption rate and the desorption activat ion energy ofw ater vapor are studied. K inet ic experiments o fw ater vapor adsorption on the silica gels are carried ou t by themethod of stat ic adso rption, and the temperature program desorption (TPD ) exper-i ments are conducted to est imate the desorption activat ion energy o fw ater 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 2106 nm, 5. 28 nm and 10. 65 nm; at low relative hum idity ( 10% ~ 45% ) w ith the increases o f the pore diameter of the silica ge,l the adsorption rates increase at the initial stage of the adsorption and the amount o f equ ilibrium adsorption decreases; at h igh relative hum id ity, w ith the increase of the pore d-i ameter of the silica ge,l the adsorption rates decrease at the initial stage of the adsorption, the amount of equ ilibrium amount adsorption increases. The desorption activation energy o fw ater on the A-type, the B-type and the C-type silica gel is respect ively 35. 54 kJ/mo,l 31. 41 kJ/mol and 26. 16 kJ/mol ,w hich suggestes that the desorption act ivation energy of thew ater on the silica ge ldecreases as its pore diameter increases. A tmedium and h igher relative hum idity, the amount o f equilibrium adsorpt ion o f w ater becomes larger and the act ivation energy of thew ater desorption on themesoporous silica gel becomes lower in comparison w ith those on the m icroporous silica gel.


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Last Update: 2006-12-30