The present invention relates to a catalyst composition in the form of a capsule, having walls made of solid material which define a closed volume which contains a liquid phase comprising at least one ionic liquid of formula Q.sup.+A.sup., wherein Q.sup.+ is an organic cation and A.sup. is an anion, and in which a Brnsted acid HB is dissolved.

The present invention relates to a catalytic composition in the form of what is known as a Pickering emulsion, said composition comprising a first non-aqueous liquid phase L1 comprising hydrocarbon compounds, within which droplets of a second liquid phase L2 are stabilized by solid particles, said second liquid phase L2 comprising at least one ionic liquid of formula Q.sup.+A.sup., Q.sup.+ being an organic cation and A.sup. being an anion, and in which a Brnsted acid HB is dissolved.