Superhydrophilic ZSM-5 zeolite-coated membrane for enhancing water coalescence in water-in-oil emulsions

The filtration efficiency of coalescent filter elements used in gasoline and diesel oil dehydration in refineries is unsatisfactory and not sufficient to meet downstream water-content requirements. Thus, it was necessary to improve the internal filter medium of traditional oil-water coalescent filter elements. Zeolite membrane is a kind of material with superhydrophilicity and strong adsorption for and permeability to water. In this study, ZSM-5 zeolite membrane with superhydrophilic properties was successfully prepared by an in situ hydrothermal synthesis. Two experiments with zeolite membranes were performed, including membrane filtration and membrane coalescence tests. Membrane filtration tests showed that it possessed strong adsorption for and permeability to water and that the oil-water filtration efficiency for 32(#) turbine oil, kerosene, and corn oil were all > 95 %. In the second part of this study, composite filtration was carried out using the membrane as well as hydrophilic glass fiber and hydrophobic polypropylene (PP) membranes. Membrane coalescence test demonstrated that, when the oil contained a phenol/water combination, the water rejection rate of the composite filtration with ABACBA (A, PP fiber; B, glass fiber; and C, molecular sieve membrane) was 90.8 %, with the downstream water content controlled within 100 mg/L and the quality factor increased from 0.18 to 0.23, relative to other systems. These experimental results showed potential for improving the current oil-water coalescent filters.