Monoliths with MFI zeolite layers prepared with the assistance of 3D printing: Characterization and performance in the gas phase isomerization of α-pinene

• Published in: Applied catalysis. A, General General, 2019-06, Vol.579, p.75-85
• Main Authors: Hędrzak, E., Węgrzynowicz, A., Rachwalik, R., Sulikowski, B., Michorczyk, P.
• Format: Article
• Language: English
• Subjects: 3-D printers; 3D printing; Aluminum; Ammonia; Catalysis; Catalysts; Deposition; Gas phase; Heat treatment; Isomerization; Macroporosity; MFI layers; Monoliths; Morphology; NMR spectroscopy; Phase composition; Porosity; Selectivity; Shrinkage; Silicon; Three dimensional printing; Vapor phases; X-ray diffraction; Zeolites; α-pinene
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2019.04.017

[Display omitted] •Monoliths prepared with the assistance of 3D printing templates could be functionalized by deposition of zeolite (MFI) layers.•One-step hydrothermal process of a preparation and deposition was developed to control the Si/Al ratio of the zeolite layer.•Acidity and catalytic performance could be conveniently controlled by adjusting the Si/Al ratio in a starting gel.•Monoliths containing the MFI layers revealed an excellent catalytic performance and thermal stability. Three-dimensional (3D) printing represents a promising technology of solid catalysts/reactors preparation with almost unlimited architecture. A casting route applied in this work for preparation of catalysts with the assistance of a 3D-printed template using the high-resolution Digital Light Processing (DLP) technology renders a possibility to control at the micron-scale macroporosity of the monolithic catalysts, their shape and size, with a very small shrinkage occurring during thermal treatment. We have demonstrated that the monoliths prepared with the assistance of 3D printing templates could be readily functionalized by deposition of ZSM-5 type zeolite (MFI) layers. The one-step hydrothermal process of a preparation and deposition was developed to control the Si/Al ratio and thickness (20–50 μm) of the zeolite layer. In all the cases, the phase composition (X-ray diffraction), porosity (low-temperature sorption of nitrogen), morphology and the Si/Al molar ratio in the layers (SEM/EDS), were studied. Moreover, the status of silicon and aluminium nuclei was followed by solid-state 29Si and 27Al MAS NMR, while the acidity of the zeolite layers was estimated using thermodesorption of ammonia. The catalytic performance of the monoliths was tested in the gas-phase isomerization of α-pinene. It was shown that the acidity and catalytic performance could be conveniently controlled by adjusting the Si/Al ratio in a starting gel. Over the sample with the lowest Si/Al ratio in MFI layer (Si/Al = 30), during 4 h on stream, the conversion of α-pinene changed between 97-79%, while the selectivity to limonene and camphene varied between 7–27 % and 31–39 %, respectively. Moreover, it was found that the monolithic catalyst can be regenerated by short treatment with air at 700 °C.