Abstract: A continuous process for converting by transesterification the diester of polytetramethylene ether (PTMEA) to the corresponding polytetramethylene ether glycol (PTMEG). The process is characterized by the fact that the feed, consisting of PTMEA along with an alkanol (preferably methanol) and with an alkali metal oxide, hydroxide or alkoxide catalyst (preferably sodium methaoxide) is made to react in two multistaged reactions in series. In the first reactant, including stages of retention in association with distillation trays of high efficiency, the bulk of conversion is achieved by stripping the alkanol ester formed in the transesterification with vapors of hot alkanol having a reduced content of alkanol ester. The transesterification is completed in the second reaction by stripping the effluent from the first reactor with vapors of hot alkanol almost free of alkanol ester.

Abstract: An improved process for the production of high quality unsaturated dimethylesters by reacting dicarboxylic anhydrides, typically maleic anhydride or phthalic anhydride, with methanol. The process is characterized by the fact that the esterification is performed in two steps, the step 1 consisting in a non catalytic reaction of formation of monomethylesters, and the step 2 consisting in the catalytic reaction of formation of dimethylesters from the monomethylester, the said catalytic reaction taking place in a reactor consisting of a multi-tray column where the liquid phase containing the mono and diester mixture flows downwards from each tray coming to contact with a progressively drier upflowing stream of vapors in countercurrent, which continuously removes the water formed in the reaction from the liquid phase. The process uses an alkylbenzene sulfonic acid with an alkyl radical containing from 10 to 13 carbon atoms as esterification catalyst.

Abstract: An improved process for the production of dimethylesters by reacting dicarboxylic acids or anhydrides, typically maleic anhydride or phthalic anhydrides, with methanol. The process uses an alkylbenzene sulfonic acid with an alkyl radical containing from 8 to 16 carbon atoms, preferably from 10 to 13 carbon atoms as esterification catalyst.