Separation of pentane isomers using MFI zeolite membrane

A BZSM-5 zeolite membrane layers supported on a porous tubular alpha alumina support were prepared by hydrothermal synthesis. Permeation of single and binary mixture of normal pentane (nC5) and 2-methylbutane (2 MB) through BZSM-5 zeolite membrane was studied as a function of total pressure, temperature and feed composition using total pressure difference and concentration gradient methods. The nC5/2 MB selectivity decreased with increasing of temperature. The rapid decrease in separation selectivities with increase in temperature indicated that preferential adsorption was responsible for the selectivity. The selectivity decreased as the feed pressure increased in total pressure difference method. The performance of membrane in concentration gradient method is higher than that in total pressure drop method. It can be addressed by decreasing of non-zeolite effect on membrane permeation in the concentration gradient method. In addition, in contrast of pressure drop method, the nC5/2 MB selectivity of membrane increased with increase in feed pressure for concentration gradient method.

► A BZSM-5 zeolite membrane was prepared for separation of pentane isomers.
► Permeations were performed by concentration gradient and total pressure drop methods.
► The highest nC5/2 MB selectivity (65) was obtained in concentration gradient method.
► nC5/2 MB selectivity increased over two times with decreasing temperature about 50 K.
► Preferential adsorption is responsible for the separation of pentane isomers.