Microporous Nickel-Coordinated Aminosilica Membranes for Improved Pervaporation Performance of Methanol/Toluene Separation

The nickel-doped bis [3-(trimethoxysilyl) propyl] amine (BTPA) derived membrane has a microporous coordinated network that has high potential to be an ideal separation barrier for methanol-toluene azeotropic mixtures via the pervaporation process. Ni-BTPA membranes were modified by employing a nickel dopant over amine groups in mole ratios (mol/mol) that ranged from 0.125 to 0.50. The incorporation of different amounts of nickel dopant into flexible amine-rich organosilica precursors of BTPA increased the rigidity and resulted in a porous structure with a large specific surface area (increased from 2.36 up to 282 m2 g-1) and a high pore volume (from 0.024 up to 0.184 cm3 g-1). Methanol-toluene separation performance by the nickel-doped BTPA (Ni-BTPA) membranes was increased with increases in the nickel concentration. Ni-BTPA 0.50 showed separation performance that was superior to other types of membranes, along with a high-level of flux at 2.8 kg m-2 h-1 and a separation factor higher than 900 in a 10 wt % methanol feed solution at 50 °C. These results suggest that the balance between the microporosity induced by amine-nickel coordination and an excessive amount of nickel-ion facilitates high levels of flux and separation of methanol.