Oriented MFI Membranes by Gel‐Less Secondary Growth of Sub‐100 nm MFI‐Nanosheet Seed Layers

Abstract

A zeolite membrane fabrication process combining 2D-zeolite nanosheet seeding and gel-free secondary growth is described. This process produces selective molecular sieve films that are as thin as 100 nm and exhibit record high permeances for xylene- and butane-isomers.

Zeolite membranes – a review and comparison with MOFs

“…9 Recent reports of 100-200 nm zeolite membranes are promising advances for their commercial viability. 10,11 There have been some recent industrial projects that use zeolite membranes, such as for ethanol dehydration, but so far these projects have been limited. A major constraint has been the low flux and high cost, which make the required membrane area to be economically unviable.…”

Zeolite Membranes in Catalysis—From Separate Units to Particle Coatings

“…Nevertheless, no industrial commercialization of zeolite membrane reactors has been occurring until now. However, recent pioneering developments towards sub-µm membranes [33][34][35][36][37][38] or the reduction of defects [39][40][41] promise a revival of zeolite membrane applications. Furthermore, novel cost reduction concepts [42] will make zeolite membranes more attractive for industry.…”

“…Seeds can be prepared either by bottom-up approaches [15] or by top-down techniques ex situ. The latter include template assisted nanoscale zeolite syntheses [68,69], exfoliation of zeolite sheets [34,70,71] or simply crushing. The nature of the obtained zeolite membrane depends strongly on the seeding and the subsequent secondary growth technique applied.…”

“…Figure 1 displays two examples of MFI membranes obtained by the two-step hydrothermal preparation procedure. Figure 1a illustrates the outcome of a recent development resulting in the most probable thinnest membrane ever reported [34]. In detail, MFI-nanosheets were prepared by exfoliation of multilamellar MFI.…”

“…This approach could be a more powerful strategy for the preparation of sub-µm membranes compared to the alternative Langmuir through assembly [36,72]. Scanning electron micrographs of (a) MFI film prepared by gel-less growth of MFI-nanosheets on a Stöber silica support (Reprinted with permission from [34]. Copyright (2015) John Wiley and Sons.…”