Fast microwave synthesis of Pt-MFI zeolite coatings on silicon micromonoliths: application to VOC catalytic combustion

Abstract

This paper describes the preparation of a ZSM-5 zeolite layer onto conventional Si wafers and Si micromonoliths, by using microwave-assisted seeded hydrothermal synthesis. A homogeneous ZSM-5 zeolite layer up to 680 nm was obtained over the external surface of a Si micromonolith (surface to volume ratio > 300,000 m -1 ) after only 4 min of hydrothermal synthesis at 453 K. As a proof of concept, the catalytic activity of the prepared ZSM-5 coated micromonoliths, after a conventional Pt ion-exchange process, was demonstrated in the combustion of traces of n-hexane (200 ppmV) in air.

Pt based catalytic coatings on poly(benzimidazole) micromonoliths for indoor quality control

“…The T 50 is 210°C, almost 70°C higher than the exhibited by ETS-10/Pt in powder form but working at a higher contact time, 565 ms. However, it is almost identical to the previously reported [27] for Pt exchanged ZSM-5 zeolite layers hydrothermally grown onto Si micromonoliths with surface to volume ratio above 300000 m -1 (i.e. 215°C at 34 ms as contact time).…”

“…For such purposes, the micromonolith was properly assembled and sealed on a reaction chamber following the procedures already described in our previous works [26][27]. …”

“…Given the unique properties of microporous zeolites and related materials, significant efforts have been carried out in our group to combine the experience gathered in growing zeolites and the fabrication methods used in the IC industry to prepare microstructured supports with new functionalities [23][24][25]. In particular, Si substrates providing external area for the zeolite films around 300000-750000 m 2 /m 3 of reactor volume have been tested for VOC catalytic removal due to mass transfer limitations are controlling the reaction rate [26][27]. In our recent work [27], regular structures of SiO 2 micro monoliths with a diameter of 3-5 microns, created on silicon wafers, were covered with a uniform MFI type film after only 4 min of hydrothermal synthesis at 453 K assisted by microwave heating.…”

“…In particular, Si substrates providing external area for the zeolite films around 300000-750000 m 2 /m 3 of reactor volume have been tested for VOC catalytic removal due to mass transfer limitations are controlling the reaction rate [26][27]. In our recent work [27], regular structures of SiO 2 micro monoliths with a diameter of 3-5 microns, created on silicon wafers, were covered with a uniform MFI type film after only 4 min of hydrothermal synthesis at 453 K assisted by microwave heating. The thin Pt-ZSM5 zeolite coating (< 1 micron) provided a short diffusion path length, underlying the potential of these microstructures as highly efficient contactors.…”

Mathematical model of thermal storage catalytic combustion process of ethyl acetate on platinum/palladium molecular sieve support reaction system

“…In catalytic combustion process, a catalyst is used to promote the oxidation reaction of ethyl acetate at a low temperature of 200°C–400°C, and the heat is recovered by periodically changing the gas flow to maintain self‐heating operation . 4–6 This process has the advantages of flame less combustion, NOx‐free combustion by‐products, energy saving, and consumption reduction 7–9 . However, the temperature of the VOCs gas in the catalytic section and the entrained solids of the catalyst cannot be detected, and the more dangerous phenomenon of ‘flying temperature' and ‘fire out' on the reactor cannot be eliminated.…”