Abstract: A process for the recovery of sulphur trioxide, solutions of sulphuric acid, or organic derivatives thereof, using organic compounds and/or supercritical fluids, and catalyst. The process comprises the steps of passing a mixture of SO2 and an oxygen-containing gas over an activated carbon catalyst at a temperature of at least 15° C. and preferably at a pressure of 1-200 atmospheres, and stripping the activated carbon with either (i) a liquid organic compound selected from the group consisting of ketones, ethers, decalin, tetrahydrofurans, sulpholanes, glymes and formamides and which is non-reactive with sulphur trioxide or sulphuric acid, or (ii) a liquid organic compound capable of forming organic sulphates or sulphonates by reaction with sulphur trioxide or sulphuric acid. The process may be used to obtain sulphuric acid, or organic sulphates or sulphonates.