Evaluation of hybrid polysaccharide membranes for gas dehydration using on-line mass spectrometry

The removal of water from gas streams, in particular flue gas and biogas, is an important industrial operation. To mimic these industrial dehydration processes, permeation of water vapour, pure gases (CO₂, CH₄ and N₂) and gas mixtures containing 20 vol% CO₂ + 80 vol% N₂ and 70 vol% CH₄ + 30 vol% CO₂, at different conditions of relative humidity, was monitored by mass spectrometry. The potential of using hybrid polysaccharide membranes obtained from a low cost carbon source (glycerol) and crosslinked using (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as silica precursor by a sol-gel method was evaluated. The hybrid membranes developed showed barrier properties to all gases studied, with a gas permeability below 1 barrer, while exhibiting high water permeabilities and selectivities. When process in a biogas mixture, the water permeability was found to be three times higher than water permeability in a flue gas mixture, leading to a H₂O/CH₄ selectivity much higher than H₂O/N₂ selectivity. These membranes showed, under close-to-real conditions, that they have the ability to dehydrate mixtures, with the advantage of not losing N₂ or CH₄, due to the low permeability values of these gases.