Structure-directing study of 1-methylimidazolium-based dication with tetramethylene as spacer length in the synthesis of microporous silicoaluminophosphates

The molecular sieves, AFO, AEI and CHA-t, were synthesized using the 4BI cation as OSDAs. The crystallization of AEI and AFO phases was through in hydroxide media, while in the presence of fluoride induces the formation of triclinic chabazite (CHA-t).

Zeolite Synthesis Using Imidazolium Cations as Organic Structure-Directing Agents

Imidazolium-derivative cations are very interesting molecules used as organic structure-directing agents (OSDAs) for zeolite synthesis, widening the possibilities of new materials and applications in this research area. In this review, the studies performed at LABPEMOL using this kind of compound are presented after a quick overview on imidazolium derivatives. The first zeolite synthesis results that started this research study were obtained with 1-butyl-3-methylimidazolium chloride. Then, the design of new OSDAs based on the imidazolium cation, such as 1,2,3-triethylimidazolium, 2-ethyl-1,3-dimethylimidazolium and 1,2,3-triethyl-4-methylimidazolium, is reported. Afterwards, the structure-direction effect caused by the introduction of heteroatoms with already-published imidazolium derivatives (for example, the Al3+ insertion into zeolite frameworks with two different OSDAs and the silicoaluminophosphate (SAPO) synthesis using 2-ethyl-1,3,4 trimethylimidazolium cations) is discussed. Finally, we also present a quick overview of some achievements of other laboratories.

Introduction of Al into the HPM-1 Framework by In Situ Generated Seeds as an Alternative Methodology

An alternative method for the introduction of aluminum into the STW zeolitic framework is presented. HPM-1, a chiral STW zeolite with helical pores, was synthesized in the pure silica form, and an aluminum source was added by in situ generated seeds. Displacements of the peak positions in the Al samples were found in the X-ray diffractograms, indicating the possible incorporation of the heteroatom into the framework. Using an analysis of the 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra, we concluded that the aluminum was effectively introduced into the framework. The (AlTETRAHEDRAL/AlOCTAHEDRAL) ratio and its textural properties were studied to explain the catalytic ethanol conversion results at medium temperatures. The sample with the lowest Si/Al ratio showed the best results due to its higher surface area and pore volume, in comparison to those observed for the sample with the highest Si/Al ratio, and due to its higher bulk tetrahedral aluminum content, in comparison to the intermediate Si/Al ratio sample. All catalysts were selective to ethylene and diethyl ether, confirming the presence of acidic sites.