1-alkyl-3-methyl imidazolium bromide ionic liquids in the ionothermal synthesis of aluminium phosphate molecular sieves

The systematic increase in alkyl chain length from 2 to 5 carbons in 1-alkyl-3-methyl imidazolium bromide ionic liquids is investigated in the ionothermal synthesis of aluminophosphate (AlPO) zeolite materials in sealed autoclaves. The effect of alkyl chain branching and the use of an imidazolium dication ionic liquid are also investigated. On addition of HF to the reaction mixture, a small amount of 1,3-dimethylimidazolium cation is formed in all cases (except when the alkyl chain length is 2), which acts as the structure directing agent (SDA) in the formation of AlPO molecular sieves with the CHA framework (SIZ-10). For 1-ethyl-3-methyl imidazolium bromide ionic liquids, the cation is incorporated intact into the SIZ-4 structure. The resulting materials are characterized by single-crystal X-ray diffraction and C-13 MAS NMR.