Process of production of tertiary ethers from C4 or C5 feedstock, including extractive distillation

摘要

A description is given of a process for the production of tertiary ethers (MTBE, ETBE, TAME, ETAE) in which a hydrocarbon feedstock (1) containing four or five carbon atoms is reacted with methanol or ethanol (2, 3) in a reactor (6) and, after distillation (CI), the ethers (11) and a distillate (10) are recovered. A first extractive distillation of the distillate is carried out in the presence of a selective solvent (27) for olefinic hydrocarbons in a column (CII) and a head fraction (15), rich in saturated hydrocarbons, and a bottom fraction (18), rich in olefins, solvent and alcohol, are recovered. The olefins (20) are separated from the solvent and the alcohol (24) by a second extractive distillation (CIII). The olefins are isomerised in a skeletal isomerisation reactor (5) and the isomerisate is recycled (2) to the reactor (6). The alcohol and the solvent are separated in a stripping column (CIV) and the alcohol (26) is recycled to the synthesis reactor (6) whereas the solvent (27) is recycled to CII. The temperature of the bottom of the second column (CIII) can be lowered by addition of fresh alcohol (4) or recycled alcohol (34). Application to additives which increase the octane number of petrols.