High yield synthesis and catalytic performance of aluminogermanosilicate IWV zeolite with tunable Ge content

Abstract

The chemical composition of IWV-type zeolite has extended from traditional aluminosilicate to germanosilicate. Due to the unique 12 × 12-ring channel system and the feasibility of structural transformation based on the lability of Ge-O bonds, the synthesis of Ge-containing IWV zeolite has aroused continuous interest. Despite all the progress, it's still challenging to prepare Ge-IWV zeolite with tunable Ge content and high product yield. In this contribution, we report the high yield (>85 %) synthesis of aluminogermanosilicate IWV zeolite using commercially available 1,1,3,5-tetramethylpiperidinium hydroxide (1,1,3,5-TMPOH) as organic structure-directing agent (OSDA). The effects of synthesis parameters, such as the Si/Ge molar ratio, Al content and dilution of the initial gel are investigated. Highly crystalline IWV zeolites can be obtained in the Si/Ge ratio range of 2.5–10. The physicochemical properties of IWV zeolites with various Ge contents are studied using multiple characterization techniques. Like in most germanosilicate zeolites, Ge atoms are preferentially incorporated into the double-four-ring (D4R) units. The IWV zeolites are endowed with nanoplate-like crystal morphology, high specific surface area and strong acidity, thus can be utilized as catalysts for the conversion of bulky molecules. In the catalytic cracking of 1,3,5-triisopropyl benzene (TiPB), IWV zeolites show high conversion and prolonged lifetime, superior to Beta zeolite. Moreover, the catalytic performance strongly depends on the Ge content and acidity of the IWV zeolites.