A large number of different processes are available to purify the synthesis gas by removing H2S, COS and CO2. The Rectisol process of Lurgi and Linde for example is widely used and involves pressurized washing with methanol. Another example is the Selexol process (Allied; now UCC) which exploits the pressure-dependent solubility of the acidic gases in the dimethyl ethers of poly(ethy1ene glycol). The Shell Sulfinol process employs mixtures of sulfolan/diisopropylamine/ water, while the Lurgi Purisol process uses N-methylpyrrolidone. Also employed in other processes are diethanolamine, diglycolamine, propylene carbonate or alkali salts of amino acids such as N-methylaminopropionic acid (Alkazid process).