Efficient, low-cost, minimal reagent syntheses of high silica zeolites using extremely dense gels below 100 °C

By using very dense, minimal water content synthesis gels, it is possible to prepare highly siliceous ZSM-5 (MFI) zeolite at temperatures below 100 °C using very simple apparatus and experimental procedures in short reaction times. The materials are highly crystalline and can be made using both fumed silica and Ludox reagents under both high alkali and fluoride synthesis conditions. Aluminium is easily incorporated into the framework in the high-alkali syntheses.Preliminary experiments on ZSM-11 suggest that the method may be applicable to other high silica zeolite frameworks.

Graphical abstractThe powder XRD pattern in the figure demonstrates the high quality of MFI samples prepared from very dense gels with stochiometric quantities of silica and template together with appropriate mineralization agents and minimal water content in simple polypropylene bottles at 90 °C in times similar to those involved in conventional syntheses at much higher temperatures.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of high-silica zeolites below 100 °C using very dense synthesis gels. ► Example: very high-quality MFI zeolite at 90 °C in 3–5 days in high yield. ► Simple, efficient, static reactions using very simple non-pressurized equipment. ► Suitable for bulk syntheses or laboratory demonstration experiments.