Preparation of b-oriented MFI films on porous stainless steel substrates

The preparation of smooth mesoporous silica layers on rough, porous stainless steel supports and the subsequent synthesis of well-intergrown b-oriented MFI films on these intermediate layers were investigated. Parameters such as surfactant-silica sol dilution, number of coating cycles, drying, and calcination were systematically varied to optimize mesoporous silica deposition results. Multiple slip- and aerosol-coating cycles with intermediate drying/calcination steps had to be employed to prepare mesoporous layers with adequate thickness and minimal cracking. b-Oriented MFI seed monolayers could be covalently attached to these mesoporous layers with high coverage using 3-chloropropyltrimethoxysilane as the coupling agent. Sonication during the final step of seed deposition was found to be necessary to achieve high seed coverage and orientation. Finally, highly b-oriented and intergrown MFI films could be produced by secondary growth of b-oriented seed layers using trimer tetrapropylammonium iodide as the structure-directing agent.