Synthesis of FER membrane on an alumina support and its separation properties

Preparation method was established to synthesize a defect-free FER membrane by a vapor-phase transport (VPT) method. In preparing FER membrane, a porous alumina support was dipped in a gel to coat with the gel. After drying, the gel on the alumina support was crystallized to FER under vapors of ethylenediamine, triethylamine and water. Two types of dipping methods were examined. First, the porous alumina support was dipped in a gel for 1 day. In the second method, after dipping the support in the gel for 1 day we forced the gel to penetrate into the pores of the alumina support by evacuating the support from one side. A permeation test of 1,3,5-triisopropylbenzene (TIPB) through FER membrane was carried out at room temperature to check the compactness of the FER membrane. The permeation of 1,3,5-triisopropylbenzene (TIPB) through FER membrane synthesized using the second dipping method was not detected, indicating that in the FER membrane there was no pinhole as large as the molecular dimension of TIPB. The pervaporation tests for cyclohexane, benzene, p-xylene and o-xylene were carried out at room temperature. The separation factor for a benzene/p-xylene mixture using the FER membrane was 100, which was much greater than 10.3 predicted from the gas-liquid equilibrium. The FER membrane showed a promising potential to separate organic compounds such as aromatic hydrocarbons.