The present invention relates to a process for workup of a methanol/water mixture which is employed in the production of alkali metal methoxides in a reaction column. The mixture is distillatively separated in a rectification column. The vapours obtained at the upper end of the rectification column are compressed in at least two stages and the energy of the vapours compressed in each case is advantageously transferred to bottoms and side streams of the rectification column. This allows particularly energy-efficient use of the energy of the compressed vapours in the process according to the invention.

The process for workup of a methanol/water mixture is employed in the production of alkali metal methoxides in a reaction column, wherein methanol and alkali metal hydroxide solution are reacted with one another in countercurrent in a reaction column. Alkali metal methoxide dissolved in methanol is withdrawn at the lower end and a methanol/water mixture which is worked up with the workup process according to the invention is withdrawn at the upper end. The energy of the compressed vapours may additionally be used for operating the reaction column or for operating a reaction column in which a process for transalcoholization of alkali metal alkoxides is performed.

The invention relates to a process for manufacturing bis(fluoro sulfonyl)imide salt(s) (MFSI) comprising at least a step of reacting an ammonium salt of bis(fluorosulfonyl)imide (NH.sub.4FSI) with a fluorine-containing alkoxide. The invention also relates to a process for preparing the fluorine-containing alkoxide.

The present invention relates to a process for depolymerising polyethylene terephthalate (PET), in which method PET is reacted with sodium glycolate or potassium glycolate, which has been obtained by reactive distillation, to form a mixture M.sub.1 including Bis(2-hydroxyethyl) terephthalate (BHET). The process according to the invention is distinguished by the fact that BHET makes up a particularly high proportion of the decomposition products in the mixture M.sub.1. The process according to the invention thus provides a high yield of BHET that can be used directly for producing PET again. The present invention thus also relates to a process for recycling PET, in which the BHET obtained in the process for depolymerising PET is polymerised again to form PET, optionally after being further purified from M.sub.1.

The present invention relates to a process for depolymerising polyethylene terephthalate (PET), in which method PET is reacted with sodium glycolate or potassium glycolate, which has been obtained by reactive distillation, to form a mixture M.sub.1 including Bis(2-hydroxyethyl) terephthalate (BHET). The process according to the invention is distinguished by the fact that BHET makes up a particularly high proportion of the decomposition products in the mixture M.sub.1. The process according to the invention thus provides a high yield of BHET that can be used directly for producing PET again. The present invention thus also relates to a process for recycling PET, in which the BHET obtained in the process for depolymerising PET is polymerised again to form PET, optionally after being further purified from M.sub.1.