Physicochemical properties of amide–AlCl3 based ionic liquid analogues and their mixtures with copper salt

Abstract

Abstract The physicochemical properties of three different amide–AlCl3 based ionic liquid (IL) analogues and their mixtures with copper salt, such as conductivity, viscosity, density and isobutane solubility were determined over a wide range of temperatures. The effects of amide structure, amide/AlCl3 molar ratio and CuCl modification on these physicochemical properties were investigated. Results showed that the conductivity of amide–AlCl3 based IL analogues was much lower than that of traditional Et3NHCl–AlCl3 IL with same ligand/AlCl3 molar ratio due to incomplete splitting of AlCl3, whereas the density and viscosity of amide–AlCl3 based IL analogues were slightly higher. The viscosity of amide–AlCl3 based IL analogues was closely related to the amide structure, and followed the order of DMA–AlCl3 > AA–AlCl3 > NMA–AlCl3 with same amide/AlCl3 molar ratio. Meanwhile, the density of amide–AlCl3 based IL analogues ranked in the following order: AA–AlCl3 > NMA–AlCl3 > DMA–AlCl3. Increasing the amide/AlCl3 molar ratio decreased the conductivity and density, while increased the viscosity. The solubility experiment indicated that the isobutane solubility in NMA–AlCl3 was highest than that in two other IL analogues. Under the modification of CuCl, the conductivity, viscosity and density of these IL analogues increased, whereas the isobutane solubility decreased. These results provide the foundation for the development of a suitable IL analogue catalyst for isobutane alkylation.