Preparation and application of highly oriented MFI zeolite membranes for efficient pervaporation recovery of organic solvents.

Membrane-based pervaporation (PV) is highly efficient and energy-saving, and is poised to emerge as a promising technology for recovering biofuels from aqueous solutions. In this study, we prepared two versions of zeolite membranes, randomly oriented and highly (h0h)-oriented silicalite-1, with similar thicknesses on α-alumina tubes, and performed the first-reported systematic comparison of their PV performances in recovering organic solvents such as methanol, ethanol, acetone, n-propanol, isopropanol, and n-butanol from water. The contribution of the intrinsic properties of these membranes to PV was explored through permeance and selectivity analysis. The highly (h0h)-oriented membrane exhibited a significantly higher level of PV performance. In addition, the permeation behavior of PV and single-gas molecules through the highly (h0h)-oriented membranes was investigated, along with the influence that operating conditions (feed temperature and concentration) exert on PV. The results suggest that the PV permeation mechanism of organic solvent/water systems through the (h0h)-oriented silicalite-1 membranes involves a combination of adsorption-diffusion and molecular sieving. Furthermore, compared with other MFI-based membranes reported in the literature, the highly (h0h)-oriented silicalite-1 membrane demonstrated outstanding comprehensive separation performance due to its highly hydrophobic, preferentially oriented, and uniform silicalite-1 layer. For example, the separation factors for 10 wt% binary aqueous solutions of methanol, ethanol, acetone, and n-propanol were 12 at 50 °C, 32 at 70 °C, 145 at 70 °C, and 37.7 at 50 °C, respectively, with corresponding total flux values of 4.18, 2.63, 2.5, and 0.29 kg/(m2 h), respectively. These unique properties suggest its potential for PV recovery of organic solvents in sustainable chemical engineering. Figure. Schematic diagrams of the structure, pore size, and pervaporation process of (a) highly (h0h)-oriented MFI membranes and (b) randomly oriented MFI membranes with intercrystalline defects, (c) molecular size dependency of the permeance on single-gas permeation and pervaporation in organic solvent/water mixtures (water permeance was obtained from the MeOH/water mixture). [Display omitted] • A highly (h0h)-oriented silicalite-1 zeolite membrane was successfully prepared. • This is the first systematic study of (h0h)-oriented silicalite-1 membranes for PV recovery of organic solvents. • The (h0h)-oriented membrane exhibited excellent pervaporation separation performance. • The PV permeation mechanism was controlled by adsorption-diffusion and molecular sieving. [ABSTRACT FROM AUTHOR]