Preparation of chabazite with mesopores templated from a cationic polymer

Abstract

Mesoporous chabazite zeolites were prepared by using the cationic polymer polydiallyldimethylammonium chloride (PDADMAC) as template for mesopores and N,N,N-trimethyl-1-adamantammonium hydroxide as structure directing agent for the chabazite framework. The prepared zeolites had large surface areas and significant mesopore volumes that increased with high PDADMAC loading. Nitrogen sorption isotherms of chabazite zeolites with low loadings of PDADMAC (0.8–2.3 wt.%) displayed a composite of Type I and II with a broad H4 hysteresis loop at p/po=0.8–1.0. At a high polymer loading (3.1 wt.%) the resulting zeolite displayed the Type IV sorption isotherm and H3 hysteresis. The chabazite zeolites prepared with 0.8–2.3 wt.% polymer had exponentially decaying mesopore size distribution curves ranging from 2 to 30 nm centred around 4–5 nm. A polymer loading of 3.1 wt.% gave a zeolite with a multimodal meso- and macropore size distribution curve ranging from 2 to 140 nm. Adjusting the synthesis gel composition made it possible to prepare mesoporous chabazite zeolites with PDADMAC loadings up to 3.1 wt.% at Si/Al = 20–70.