Catalysts obtained by the immobilisation of acidic ionic liquids (ILs) on solid supports offer several advantages compared to the use of catalytically active ILs themselves. Immobilisation may result in an increase in the number of accessible active sites of the catalyst and a reduction of the amount of the IL required. The ionic liquid films on the carrier surfaces provide a homogeneous environment for catalytic reactions but the catalyst appears macroscopically as a dry solid, so it can simply be separated from the reaction mixture. As another advantage, it can easily be applied in a continuous fixed bed reactor. In the present review the main synthetic strategies towards the preparation of supported Lewis acidic and Brønsted acidic ILs are summarised. The most important characterisation methods and structural features of the supported ionic liquids are presented. Their efficiency in catalytic reactions is discussed with special emphasis on their recyclability.

Brønsted acidic ionic liquids, supported on silica gel, have been used effectively in oligomerisation of isobutene. The supported catalysts could be used several times without loss of activity or change in selectivity. The ratio of the products could be influenced by the proper choice of the ionic liquid component of the catalyst and the reaction temperature.

The use of [bmim]⁺[BF₄]⁻, [bmim]⁺[PF₆]⁻ and [emim]⁺[PF₆]⁻ ionic liquids as solvents in homogeneous catalytic aminocarbonylation of 17-iodo-5α-androst-16-ene at atmospheric carbon monoxide pressure has been investigated. It has been proved that after the extraction of the product with toluene, the ionic liquid–catalyst mixture could be recycled several times. Although there was a loss of catalytic activity in the further cycles, even 94% conversion can be achieved after the fifth run by using [bmim]⁺[BF₄]⁻ ionic liquid. The conversion depended strongly both on the properties of the ionic liquid and those of the catalyst. The activities of the in situ palladium(0) catalysts prepared from Pd(OAc)₂ and various phosphine ligands (PPh₃, TPPTS, DPPBA) have been compared. The method can be effectively used for the aminocarbonylation of other steroids with 17-iodo-16-ene functionality.