Abstract
The silicalite membranes were grown hydrothermally on the surface of porous mullite tubes ( 12mm outer diameter, 9mm inner diameter, 500mm length, 1.0µm average pore size and ca. 40% porosity). Hydrothermal synthesis (SiO2:0.17TPAOH:120H2O) was made at 185°C for 40 h. In order to remove the TPA+ template, the membranes were calcined at 500°C for 10 h. The membranes displayed excellent ethanol-permselective performance in pervaporation (PV) for ethanol solution. With an increase in temperature, the permeation flux Q increased and the separation factor α slightly decreased. In PV of 5 wt% ethanol solution at 50°C, Q values were 400 gm-2h-1 and α values were above 80.
Two tubular-type modules (double tube-type module, tubular-type module) with 9 pieces of silicalite membrane were designed in order to make the silicalite membranes viable for fermentative application. These membranes used in the two modules are sealed at one end of a support tube. The double tube-type module is composed of a membrane inserted in the steel tube and group of these modules are put in a vacuum vessel. In the tubular-type module, these membranes are inserted alternatively at the designed pitch from both tube sheet and fixed at the tube sheet. In both modules, ethanol solution is fed to the outer side of the membrane and the permeate through the inside of the membrane is collected by condenser.
The efficiency of both module on Q and α increased in proportion to the feed flow rate and was not almost dependent on the feed flow rate > 2 l/h per a piece of membrane ( for double tube-type module) or 5.6 l/h per one ( for tubular-type module).
In the module efficiency that was not influenced by the feed flow rate, the module efficiency of the double tube-type was ca. 1, and that of the tubular-type was ca. 0.9
