A process for removing sulphur-containing, nitrogen-containing and halogen-containing impurities including H2S, COS, CS2, HCN, NH3, HF, HCl, HBr or HI, contained in a synthesis gas, said process comprising:
- a) joint hydrolyzing of COS and HCN and collecting halogen-containing compounds using a TiO2-based catalyst comprising between 10% by weight and 100% by weight of TiO2 and between 1% by weight and 30% by weight of at least one sulphate of an alkaline earth metal that is calcium, barium, strontium or magnesium,
- b) washing using at least one solvent,
- c) desulphurization on a collecting or adsorbing mass.