Effect of core-shell structuring of chabazite zeolite with a siliceous zeolite thin layer on the separation of acetone-butanol-ethanol vapor in humid vapor conditions

Due to its shape selective properties, the narrow pore chabazite zeolite is an interesting material for the separation and purification of 1-butanol from ABE (acetone-butanol-ethanol) fermentation broth, as it selectively traps ethanol from the mixture of acetone, ethanol and butanol. In order to improve the separation performance of chabazite zeolite in humid conditions, we synthesized a core-shell structured chabazite type zeolite, with a chabazite aluminosilicate core coated with a pure silica chabazite layer. This material was evaluated in the vapor phase separation of 1-butanol using a model ABE vapor mixture. Unexpectedly, a broader breakthrough profile of ethanol was obtained on the coated chabazite, resulting in a lower 1-butanol recovery. It was found that the adsorption rate of 1-butanol was decreased by the pure silica chabazite coating. In breakthrough experiments, the coated chabazite showed an even more pronounced exclusion of 1-butanol as compared to the parent material, resulting in a larger separation factor of ethanol over 1-butanol. The pure silica chabazite coating layer acts as a kind of diffusion barrier against 1-butanol rather than ethanol, enhancing the molecular sieving effect.