摘要:
Crude water-containing tetrahydrofuran is purified by distillation by a process in which the crude tetrahydrofuran is passed through three distillation columns, water being removed from the bottom of the first column, water-containing tetrahydrofuran being recycled from the top of the second column into the first column, the top product of the third column being recycled to the first column, a distillate being removed at the top of the first column, and pure tetrahydrofuran being distilled off from the bottom product of the second column, in the third column, and the pure tetrahydrofuran being removed from the side take-off of the third column.
摘要:
Cyclic ethers, especially tetrahydrofuran, are manufactured by dehydrating diols in the liquid phase in the presence of a bleaching earth as the catalyst and of a minor amount of an alkali metal or alkaline earth metal carbonate or bicarbonate.
摘要:
A process for the preparation of polybutylene glycol carboxylic acid diesters of the formulaR-CO-O--CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 -O).sub.n CO-R.sup.1by polymerizing pretreated tetrahydrofuran in the presence of one or more carboxylic acids and/or carboxylic acid anhydrides and of a polymerization catalyst, especially antimony pentachloride or a bleaching earth containing less than 3% by weight of water, wherein the tetrahydrofuran is treated with a strong mineral acid, an organic sulfonic acid, silica gel and/or a bleaching earth prior to the polymerization.
摘要:
A process for depolymerizing polytetramethylene glycol ethers, wherein the latter are heated at from 90.degree. to 180.degree. C. in the presence of a bleaching earth.
摘要:
Polytetramethylene ether glycols with molecular weights of from 300 to 4500 are produced by polymerizing tetrahydrofuran with an adduct of antimony pentachloride with carboxylic acids or carboxylic acid esters as the catalyst in the presence of a carboxylic acid anhydride, e.g., acetic anhydride, as the promoter. Esterified, e.g., acetylated, polytetramethylene ether glycols produced are subsequently converted to polytetramethylene ether glycols by saponification or transesterification. The process causes substantially less environmental pollution than do prior art methods, yet it is both economical and flexible.
摘要:
A process for the preparation of polybutylene glycol carboxylic acid diesters of the formulaR--CO--O--CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 --O).sub.n CO--R.sup.1by polymerizing pretreated tetrahydrofuran in the presence of one or more carboxylic acids and/or carboxylic acid anhydrides and of a polymerization catalyst, especially antimony pentachloride or a bleaching earth containing less than 3% by weight of water, wherein the tetrahydrofuran is treated with a strong mineral acid, an organic sulfonic acid, silica gel and/or a bleaching earth prior to the polymerization.
摘要:
Cyclic ethers are manufactured by eliminating water from corresponding diols in the presence of aluminum oxide which has been obtained by precipitating aluminum hydroxide from an alkali metal aluminate solution by means of an acid and calcining the hydroxide at from 300.degree. to 1,000.degree. C.