Ultra-thin MFI zeolite films: Synthesis, Characterization and Progress Toward Industrial Applications

Abstract

Separation processes account for 10-15% of US energy consumption. A large fraction of that energy is consumed by energy-inefficient thermal separation processes like distillation. If membranes could perform these separations, up to 90% of that energy could be saved. Zeolites have ideal properties for separations, which include their high thermal and chemical stability. However, there are currently very few examples of industrial zeolite membrane separation processes. This is due to the high cost associated with their manufacture, industrially unattractive throughput and lack of membrane separation experiments at industrially relevant conditions. This dissertation aims to make progress on some of these fronts. The recent advances in zeolite membranes are reviewed, with an emphasis on industrial applications. A membrane fabrication procedure using 3.2 nm-thick MFI zeolite “nanosheets” is reported, resulting in high-flux and high separation efficiency membranes. High performance membrane separations at industrially relevant conditions have also been achieved for the first time. Moreover, further progress towards synthesis of even thinner films and membranes has been made. The discovery of a novel deposition technique enables the transfer of monolayers of nanosheets to silicon wafers. By intergrowing them, the thinnest-ever MFI films have been synthesized. In future, this technique could be extended to fabricate even higher-flux membranes. An application of zeolite films on silicon wafers as a low-dielectric constant material is also described. Superior insulating properties and mechanical strength compared to previously reported MFI films is achieved. Such a film could save energy and promote the development of the next generation of computer chips.