Abstract: The present invention provides a process for changing the given mean molecular weight Mn in the continuous preparation of polytetrahydrofuran or tetrahydrofuran copolymers, the mono- or diesters of polytetrahydrofuran or of tetrahydrofuran copolymers by polymerizing tetrahydrofuran in the presence of a telogen and/or of a comonomer over an acidic catalyst, wherein a) the molar ratio of telogen to tetrahydrofuran or to tetrahydrofuran and comonomer is changed, b) then the mean molecular weight of at least one sample is determined, c) until the mean molecular weight thus determined differs from the molecular weight to be achieved by the change, the already formed polytetrahydrofuran or the tetrahydrofuran copolymers, the mono- or diesters of polytetrahydrofuran or tetrahydrofuran copolymer is at least partly depolymerized over an acidic catalyst and d) the tetrahydrofuran recovered by depolymerization is recycled at least partly into the polymerization.

Abstract: A process for preparing polyester alcohols by condensation of polytetrahydrofuran with aromatic dicarboxylic acids and/or their anhydrides and/or their esters, preferably isophthalic acid, phthalic acid and terephthalic acid and more preferably isophthalic acid, in the presence of a transesterification catalyst in a multi-stage operation at different pressure levels with at least one reaction stage at atmospheric pressure and at least one reaction stage at reduced pressure, where distillate is removed from the reaction system, comprises deactivating the catalyst after the polycondensation by using phosphoric acid in a molar ratio of 1:1 to 1:3.5 for catalyst to phosphoric acid.

Abstract: The subject of the present invention is a process for preparing polyester alcohols by condensation of polytetrahydrofuran with aromatic dicarboxylic acids and/or their anhydrides in the presence of a transesterification catalyst in a multi-stage operation at different pressure levels with at least one reaction stage at atmospheric pressure and at least one reaction stage at reduced pressure, where distillate is removed from the reaction system, which process comprises heating the reaction mixture in two or more phases in the atmospheric-pressure reaction stage wherein the heating phases are interrupted by at least one phase in which the temperature is kept constant.

Abstract: The present invention relates to a process for preparing polytetrahydrofuran or tetrahydrofuran copolymers by polymerization of tetrahydrofuran in the presence of a telogen and/or a comonomer over a fixed bed of an acid catalyst, in which the temperature of the polymerization mixture increases in the direction of flow through the catalyst bed.

Abstract: The invention relates to an apparatus for separating a liquid substance mixture by distillation, a method for producing a tetrahydrofuran homopolymer and copolymer in which the oligomers in a liquid starting mixture containing oligomers are separated by distillation in such an apparatus, tetrahydrofuran homopolymers and copolymers which can be obtained using said method and have a narrow distribution of the relative molar mass, and the use thereof.

Abstract: The present invention provides a catalyst comprising a mixture of at least one acid-activated sheet silicate with a transition metal oxide of groups 8 and/or 9 of the Periodic Table of the Elements and also a process for preparing polytetrahydrofuran, polytetrahydrofuran copolymers, diesters or monoesters of these polymers, in which tetrahydrofuran is polymerized in the presence of at least one telogen and/or comonomer over such a catalyst.

Abstract: The present invention provides a process for changing the given mean molecular weight Mn in the continuous preparation of polytetrahydrofuran or tetrahydrofuran copolymers, the mono- or diesters of polytetrahydrofuran or of tetrahydrofuran copolymers by polymerizing tetrahydrofuran in the presence of a telogen and/or of a comonomer over an acidic catalyst, wherein a) the molar ratio of telogen to tetrahydrofuran or to tetrahydrofuran and comonomer is changed, b) then the mean molecular weight of at least one sample is determined, c) until the mean molecular weight thus determined differs from the molecular weight to be achieved by the change, the already formed polytetrahydrofuran or the tetrahydrofuran copolymers, the mono- or diesters of polytetrahydrofuran or tetrahydrofuran copolymer is at least partly depolymerized over an acidic catalyst and d) the tetrahydrofuran recovered by depolymerization is recycled at least partly into the polymerization.

Abstract: The present invention relates to a process for preparing polytetrahydrofuran or tetrahydrofuran copolymers by polymerization of tetrahydrofuran in the presence of a telogen and/or a comonomer over a fixed bed of an acid catalyst, in which the temperature of the polymerization mixture increases in the direction of flow through the catalyst bed.

Abstract: The present invention relates to a process for preparing N-(1-alkenyl)carboxamides of the formula I, which comprises reacting a carboxamide of the formula II with an alkyne of the formula III in the presence of a catalyst selected from among carbonyl complexes, halides and oxides of rhenium, manganese, tungsten, molybdenum, chromium and iron.

Abstract: The present invention relates to a solid, acid catalyst for the preparation of polytetrahydrofuran, polytetrahydrofuran copolymers, diesters or monoesters of these polymers by polymerization of tetrahydrofuran in the presence of at least one telogen and/or comonomer, which has a BET surface area of at least 160 m2/g and an acid center density of at least 0.05 mmol/g for pKa values of from 1 to 6, to a process for preparing it and to a process for the polymerization of cyclic ethers over this catalyst.

Abstract: The present invention provides a catalyst comprising a mixture of at least one acid-activated sheet silicate with a transition metal oxide of groups 8 and/or 9 of the Periodic Table of the Elements and also a process for preparing polytetrahydrofuran, polytetrahy-drofuran copolymers, diesters or monoesters of these polymers, in which tetrahydrofuran is polymerized in the presence of at least one telogen and/or comonomer over such a catalyst.

Abstract: The present invention relates to a solid, acid catalyst for the preparation of polytetrahydrofuran, polytetrahydrofuran copolymers, diesters or monoesters of these polymers by polymerization of tetrahydrofuran in the presence of at least one telogen and/or comonomer, which has a BET surface area of at least 160 m2/g and an acid center density of at least 0.05 mmol/g for pKa values of from 1 to 6, to a process for preparing it and to a process for the polymerization of cyclic ethers over this catalyst.

Abstract: The present invention provides a process for preparing mono- or diesters of polytetrahydrofuran or of tetrahydrofuran copolymers by polymerizing tetrahydrofuran in the presence of at least one telogen and/or of a comonomer over an acidic catalyst, wherein the polymerization reactor is started up using a mixture of polytetrahydrofuran, the mono- or diesters of polytetrahydrofuran and/or of the THF copolymers, tetrahydrofuran, any comonomer and at least one carboxylic acid and/or one carboxylic anhydride.

Abstract: The present invention relates to a process for the preparation of N-substituted 2,6-dialkylmorpholines of the formula I in which R1 and R2, independently of one another, are hydrogen, alkyl or cycloalkyl, or R1 and R2 together with the carbon atom to which they are bonded are a 5- to 14-membered carbocycle, and R3 and R4, independently of one another, are alkyl or cycloalkyl, by reacting at least one carbonyl compound of the formula II in which R1 and R2 have the meanings given above, with at least one morpholine of the formula III in which R3 and R4 have the meanings given above, in the presence of hydrogen and at least one metal-containing catalyst, wherein the active component of the catalyst consists essentially of platinum group metals.

Abstract: The invention relates to a process for the continuous preparation of THF by reaction of a 1,4-butanediol-containing reaction mixture over a heteropolyacid catalyst which has not been predried, wherein the reaction mixture comprises 2-(4-hydroxybutoxy)tetrahydrofuran.

Abstract: In a process for the single-stage preparation of polytetrahydrofuran and/or tetrahydrofuran copolymers having a mean molecular weight of from 650 to 5000 dalton by polymerization of tetrahydrofuran over an acid catalyst in the presence of at least one telogen and/or comonomer, the telogen and/or comonomer is added at at least two addition points in different segments of the polymerization apparatus.

Abstract: The invention relates to a process for the continuous preparation of THF by reaction of a 1,4-butanediol-containing reaction mixture over a heteropolyacid catalyst which has not been predried, wherein the reaction mixture comprises 2-(4-hydroxybutoxy)tetrahydrofuran.

Abstract: The present invention provides a process for preparing mono- or diesters of polytetrahydrofuran or of tetrahydrofuran copolymers by polymerizing tetrahydrofuran in the presence of at least one telogen and/or of a comonomer over an acidic catalyst, wherein the polymerization reactor is started up using a mixture of polytetrahydrofuran, the mono- or diesters of polytetrahydrofuran and/or of the THF copolymers, tetrahydrofuran, any comonomer and at least one carboxylic acid and/or one carboxylic anhydride.

Abstract: The present invention relates to a solid, acid catalyst for the preparation of polytetrahydrofuran, polytetrahydrofuran copolymers, diesters or monoesters of these polymers by polymerization of tetrahydrofuran in the presence of at least one telogen and/or comonomer, which has a BET surface area of at least 160 m2/g and an acid center density of at least 0.05 mmol/g for pKa values of from 1 to 6, to a process for preparing it and to a process for the polymerization of cyclic ethers over this catalyst.

Abstract: In a process for the single-stage preparation of polytetrahydrofuran and/or tetrahydrofuran copolymers having a mean molecular weight of from 650 to 5000 dalton by polymerization of tetrahydrofuran over an acid catalyst in the presence of at least one telogen and/or comonomer, the telogen and/or comonomer is added at at least two addition points in different segments of the polymerization apparatus.