EP1297051A1

EP1297051A1 - Improved catalyst and method for producing polytetrahydrofurane

Info

Publication number: EP1297051A1
Application number: EP01960445A
Authority: EP
Inventors: Ulrich Steinbrenner; Thomas Narbeshuber; Martin Haubner; Christoph Sigwart; Gerd Linden; Gerhard Cox; Rolf-Hartmuth Fischer; Michael Hesse; Gerd Bohner; Hartmut Hibst; Ekkehard Schwab; Andreas Tenten
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-07-03
Filing date: 2001-07-02
Publication date: 2003-04-02
Also published as: AU2001281937A1; JP2004502807A; KR20030045770A; WO2002002671A1; MY134052A; US20030186806A1; CA2414989A1; CN1451023A; US6870014B2

Abstract

The invention relates to a catalyst which contains a catalytically active quantity of at least one oxygen-containing molybdenum and/or wolfram compound on an oxidic support material and which has been calcinated at temperatures of 400 to 900 °C after the precursor compound of the catalytically active compounds have been applied to the support material or to a support material precursor. The transport pores for this catalyst each have a diameter of > 25 nm and a volume of at least 50 mm 3/g. The catalyst contains x νmol (wolfram and/or molybdenum)/m2 molybdenum and/or wolfram, with 10.1 < x < 20.9 in relation to the finished catalyst, with the oxidic support material having a BET surface area of 135 to 220 m2/g. Catalysts of this type are characterized by an acidity of at least 70 νmol/g at pKs < -3 in the dry state and are therfore very active. The invention also relates to a method for producing a catalyst of this type and to the preferred use thereof.

Description

Improved catalyst and process for making polytetrahydrofuran

The present invention relates to a catalyst which contains a catalytically active amount of at least one oxygen-containing molybdenum and / or tungsten compound on an oxidic support material and which, after the precursor compounds of the catalytically active compounds have been applied to the support material or a support material precursor at temperatures of 400 ° C has been calcined to 900 ° C, and a process for its preparation. This catalyst is used in processes for the production of polytetrahydrofuran, tetrahydrofuran copolymers and diesters or monoesters of these polymers.

Polytetrahydrofuran - hereinafter referred to as PTHF for short - which is also known under the name polyoxybutylene glycol, is used in the plastics and synthetic fibers industry as a versatile intermediate and is used, among other things, for the production of polyurethane, polyester and polyamide elastomers. In addition, it is, optionally in the form of its derivatives, a valuable adjuvant in diverse applications, such as. B. as a dispersant or when decolorizing ("deinking") of waste paper.

PTHF is advantageously produced industrially by polymerizing tetrahydrofuran over suitable catalysts. In addition, reagents are also used, the addition of which enables the control of the chain length of the polymer chains and thus the adjustment of the average molecular weight to the desired value. Such chain termination reagents are also called “telogens”. The chain length is controlled by selecting the type and amount of the telogen. By selecting suitable telogens, additional functional groups can be introduced at one end or at both ends of the polymer chain. For example, using Carboxylic acids or carboxylic anhydrides as telogens which are mono- or diesters of PTHF are produced.Other telogens not only act as chain terminating reagents, but are also incorporated into the growing polymer chain of PTHF and have the function of a telogen as well as that of a comonomer, examples of such Comonomers are telogens with two hydroxyl groups, such as the dialcohols, examples of such dialcohols are ethylene glycol, propylene glycol, butylene glycol, 1,4-butanediol, 2-butyn-l, 4-diol, 1,6-hexanediol or low molecular weight PTHF. The use of such comonomers leads to the preparation of tetrahydrofuran copolymers. In this way, the PTHF can also be chemically modified. An example of this is the use of the telogen 2-butyne-1,4-diol, the addition of which leads to the presence of a proportion of CC triple bonds in the polymer chains of the PTHF. Such modified PTHF can be further chemically refined by the reactivity of these triple bonds at these points, e.g. B. by hydrogenation of the triple to double bonds, by subsequent polymerisation of other monomers ("props") to adjust the properties of the polymer, crosslinking to form polymers with a comparatively rigid structure or other common measures in polymer chemistry. The complete hydrogenation of the existing triple bonds is also possible and generally leads to PTHF with a particularly low color number.

On an industrial scale, the production of PTHF is mainly carried out by two-stage processes, in which tetrahydrofuran z. B. polymerized in the presence of fluorosulfonic acid to PTHF esters and then hydrolyzed to PTHF. In a further two-stage process, tetrahydrofuran is polymerized with acetic anhydride in the presence of acidic catalysts to give PTHF diacetate and then transesterified with methanol to give PTHF. In addition to the fact that work has to be carried out in two stages, it is particularly disadvantageous that by-products such as hydrofluoric acid or methyl acetate are obtained.

Single-stage processes for the preparation of PTHF are also known, in which the polymerization of tetrahydrofuran with diols, water or low molecular weight PTHF is carried out as a telogen on acidic catalysts. The catalyst or the catalyst system can be homogeneous, dissolved in the reaction system, or heterogeneous, largely undissolved catalyst systems can be used.

DE-A-44 33 606 describes a process for the preparation of PTHF, PTHF diesters of C ₂ to C ₂₀ monocarboxylic acids or PTHF monoesters of C to C _t o-monocarboxylic acids by the polymerization of tetrahydrofuran over a heterogeneous catalyst in the presence of a the telogenic water, 1,4-butanediol, PTHF with a molecular weight of 200 to 700 daltons, a Cj _. - To C ₁₀ monocarboxylic acid or a carboxylic anhydride from C - to C ₂ o-monocarboxylic acids or mixtures of these telogens, the catalyst being a supported catalyst which contains a catalytically active amount of an oxygen-containing tungsten or molybdenum compound or mixtures of these compounds on an oxidic support material and after application of the precursor compounds of the oxygen-containing molybdenum and / or tungsten compounds has been calcined at temperatures of 500 ° C to 1000 ° C on the substrate precursor.

DE-A-196 41 481 discloses a process for the preparation of polytetrahydrofuran, copolymers of tetrahydrofuran and 2-butyn-1,4-diol, diesters of these polymers with C ₂ to C ₂ o-monocarboxylic acids or monoesters of these polymers with - to C ₁₀ - Monocarboxylic acids from the polymerization of tetrahydrofuran in the presence of one of the telogens water, 1,4-butanediol, 2-butyn-l, 4-diol, polytetrahydrofuran with a molecular weight of 200 to 700 daltons, a - to C ₁₀ -monocarboxylic acid or a carboxylic acid anhydride C ₂ - to C ₂₀ -monocarboxylic acids or mixtures of these telogens on a heterogeneous supported catalyst. The supported catalyst contains a catalytically active amount of an oxygen-containing molybdenum and / or tungsten compound on an oxidic support material and was calcined after the application of the precursor compounds of the oxygen-containing molybdenum and / or tungsten compounds to the support material precursor at temperatures of 500 ° C. to 1000 ° C. and activated by treatment with a reducing agent before being used as a polymerization catalyst.

Starting from this prior art, the object of the present invention was to provide a catalyst which has a higher activity than the known catalysts in order to achieve higher polymer yields and / or space-time yields.

This object is achieved by a catalyst which contains a catalytically active amount of at least one oxygen-containing molybdenum and / or tungsten compound on an oxidic support material and which, after the precursor compounds of the catalytically active compounds have been applied to the support material or a support material precursor at temperatures of 400 ° C to 900 ° C has been calcined, the catalyst having a porosity with transport pores each having a diameter of> 25 nm and a volume of these transport pores of at least 50 mm ³ / g.

According to a further embodiment, the catalyst according to the invention has a molybdenum and / or tungsten content, based on the finished catalyst, of x μmol (tungsten and / or molybdenum) / m ² , 10.1 <x <20.9. This targeted adjustment of the ratio of the tungsten and / or molybdenum content to the BET surface area again significantly increased the catalyst activity. This targeted setting is achieved in that the calcining conditions are adapted to the tungsten and / or molybdenum content of the catalyst. According to a preferred embodiment, the catalyst according to the invention has a BET surface area of 25-200 m ² / g, preferably 40-150 m ² / g and particularly preferably 50-120 m ² / g. The oxidic carrier material to which the catalytically active amount of the molybdenum and / or tungsten compound is applied has a BET surface area of 135-220 m ² / g.

It has been shown that catalysts whose oxidic support material has a BET surface area of the order of magnitude mentioned are particularly acidic and active. Laboratory tests have shown that both the acidity and the activity of the catalysts decrease if the BET surface area is smaller than the range given above. Surprisingly, the acidity and the activity of the catalysts also decrease again if the BET surface area of the oxidic support material used is greater than the range claimed here. According to a preferred embodiment of the catalyst according to the invention, the BET surface area of the oxidic support material is 170-220 m ² / g and particularly preferably 190-220 m ² / g.

The catalyst according to the invention can have an acidity at pKs <-3 of at least 10 μmol / g. If such an oxidic support material is used, the BET surface area of which is in the ranges specified above, even catalysts are obtained whose acidity at pKs <-3 in the dry state is at least 70 μmol / g and preferably at least 90 μmol / g. The pKs value was determined using the Hammett titration method.

Suitable catalytically active compounds are those molybdenum or tungsten compounds which, without the addition of a carrier, are mainly in the form of MoO ₃ or WO ₃ after prolonged heating to 600 ° C. in moist air, or mixtures of these compounds. Examples of the compounds mentioned are all types of tungsten and molybdic acids, such as WO ₃ , WO ₃ 'H ₂ O, WO ₃ "2H ₂ O, meta and paratungstic acid and the isopolyacids and the corresponding analog molybdenum compounds Context to name the heteropolyacids, such as H ₃ PWι ₂ O ₄₀ , H SiWι ₂ O ₄ o, H GeWι ₂ θ ₄ o and correspondingly up to H ₆ P ₂ Wι ₈ O ₅₆ or the corresponding molybdenum compounds and the salts of the acids mentioned above such as the ammonium ortho-, ammonium meta and ammonium paratungstates, the corresponding Molybdenum compounds and reduced tungsten and molybdenum compounds as well as organomolybdenum or tungsten compounds.

Preference is given to using oxygen-containing tungsten compounds or mixtures of oxygen-containing tungsten compounds with oxygen-containing molybdenum compounds, in which the proportion of tungsten compounds predominates. It is particularly preferred to use catalysts whose catalytically active compounds, apart from usual impurities, consist practically only of oxygen-containing tungsten compounds. WO ₃ , tungstic acid and ammonium paratungstate are particularly worth mentioning here.

Oxidic supports are generally suitable as the support material, for example zirconium dioxide, titanium dioxide, hafnium oxide, yttrium oxide, iron (III) oxide, aluminum oxide, tin (IV) oxide or mixtures of these oxides. The use of zirconium dioxide or titanium dioxide is preferred, titanium dioxide being particularly preferred and titanium dioxide with a proportion of> 65% being particularly suitable in the anatase modification. The carrier material can be freshly felled, dried or calcined. The respective carrier material can by hydrolysis of the corresponding halides, nitrates, sulfates or alkoxides, for. B. can be obtained from titanium tetraisopropoxide, titanyl chloride, titanyl nitrate, titanium tetrachloride or titanyl sulfate.

For the purposes of the present invention, the specification of the catalyst content of catalytically active compounds is based on the trioxides of tungsten and / or molybdenum. The catalysts generally contain 0.1 to 70% by weight, preferably 5 to 40% by weight and particularly preferably 10 to 35% by weight, of the catalytically active compounds, in each case calculated as MoO ₃ and / or WO ₃ and based on the total weight of the fully calcined and dry catalyst.

After the application of the oxygen-containing molybdenum and / or tungsten compound, the BET surface area of the finished catalyst exceeds a maximum specific surface area of

BET [Kat, max] = BETrX] / (l ~ loss on ignition [X]). (1 - Y) Not. X means the oxidic carrier material and Y the oxygen-containing molybdenum and / or tungsten compound, each in g. This calculation is based on the fact that both H ₂ O and the oxygen-containing molybdenum and / or tungsten compound that was used occupy the surface of the oxidic carrier material.

In addition, pore formers can be used, such as. B. tartaric acid, oxalic acid, citric acid, ammonium nitrate, ammonium formate, ammonium oxalate,

Guanidinium salts, urotropin, proteins such as gelatin, polyvinyl alcohol, polyethylene oxide, polymethylene oxide, carbohydrates such as glucose, sucrose (sugar) and soluble starch, PTHF, surfactants and sulfonic acids. Tartaric acid, citric acid and oxalic acid, especially oxalic acid, are preferred.

With regard to the proportion of the pore former with which it is contained in the catalyst, the content of pore former in% by weight, based on the fully calcined and dry catalyst, is given for the purposes of the present invention. Therefore, the sum of the weight percentages of the compounds contained in the catalyst exceeds 100%. According to the invention, the catalysts contain up to 200% by weight, preferably up to 100% by weight and particularly preferably up to 60% by weight, of pore formers.

In addition, the catalyst can also contain a sulfur and / or phosphorus compound. Since it is assumed that the sulfur in the catalysts according to the invention is present as sulfate and the phosphorus as phosphate, the proportion of these compounds in the catalyst is calculated as sulfate or phosphate, based on the total weight of the fully calcined and dry catalyst. Thereafter, the catalysts can contain up to 15% by weight, preferably up to 10% by weight and particularly preferably up to 8% by weight of sulfate and / or phosphate.

Sources for the corresponding phosphorus and / or sulfur compounds are e.g. As sulfuric acid, soluble sulfates such as ammonium sulfate or ammonium hydrogen sulfate or the corresponding sulfites or hydrosulfites, phosphoric acid, soluble phosphates such as ammonium phosphate or the ammonium hydrogen phosphates or the corresponding phosphites. As a further additive, the catalysts can also contain a binder, such as silica sol, clays, boric acid or AlPO ₄ .

The invention also relates to a process for producing a catalyst which contains a catalytically active amount of at least one oxygen-containing molybdenum and / or tungsten compound on an oxidic support material, in which the following steps are carried out:

Cases of the oxidic carrier material, thermal treatment of the oxidic carrier material to set a BET surface area of 135-220 m ² / g,

Application of the catalytically active compound (s) or their precursor compound (s) to the support material and

Calcining the catalyst thus produced at temperatures from 400 ° C to 900 ° C to the finished catalyst.

It has been shown that catalysts with the specified BET surface area can be prepared by the process according to the invention by freshly precipitated oxidic support material, such as. B. preferably TiO ₂ * aq, is not used directly as an oxidic support material for the catalysts to be produced, but is first treated thermally. Freshly precipitated oxidic carrier material has a high specific surface. It was found that such a high specific surface area reduces the acidity and activity of the finished catalysts. If the surface of the oxidic carrier material is targeted by thermal treatment, for. B. by calcining at temperatures from about 300 ° C to about 550 ° C to BET values of 135-220 m ² / g, preferably 170-220 m ² / g and particularly preferably 190-220 m ² / g catalysts are produced which have a particularly high activity and an acidity at pKs <-3 of at least 70 μmol / g and preferably of at least 90 μmol / g in the dry state. It is also advantageous that a uniform carrier material with a defined BET surface is obtained. Zirconium dioxide or titanium dioxide, preferably titanium dioxide, are used as the carrier material. Since the process according to the invention preferably serves to produce the catalyst according to the invention already mentioned, in relation to the properties of the catalyst thus produced, for. B. with respect to the proportion of catalytically active compounds, optionally added pore formers, added sulfate and / or phosphate referred to what has already been said above. In a preferred embodiment of the production process according to the invention, catalysts can be produced which are distinguished by a particular mechanical stability. This mechanical stability could be achieved by carrying out the thermal treatment of the freshly precipitated TiO ₂ * aq in order to set a desired BET surface in a water-containing or water-vapor-containing atmosphere. The water-containing or steam-containing atmosphere should contain more than 10% by volume, preferably more than 20% by volume and particularly preferably more than 30% by volume of water or water vapor. The process can also be carried out under a pressure other than atmospheric pressure.

When carrying out the process according to the invention, it is preferred to apply the catalytically active compound (s) in a molar ratio of carrier material to catalytically active compound of 5.0-7.5, preferably 6.0-7.0. The calcination of the catalyst is then preferably carried out stepwise, the catalyst first being calcined at temperatures of 100-600 ° C. and then finally calcined at temperatures up to 900 ° C., preferably up to 700 ° C., to give the finished catalyst. When calcining with increasing the temperature gradually. B. calcining first at a low initial temperature, such as. B. 200 ° C, then increasing the temperature to z. B. 500 ° C and a final calcination with a further increase in temperature.

The invention also relates to a process for the preparation of polytetrahydrofuran, tetrahydrofuran copolymers, diesters or monoesters of these polymers by polymerizing tetrahydrofuran in the presence of at least one telogen and / or comonomer using the aforementioned catalyst in one of its embodiments according to the invention, the catalyst for example the likewise claimed manufacturing method has been obtained in one of its configurations according to the invention.

The production of polytetrahydrofuran and tetrahydrofuran copolymers and polytetrahydrofuran dicarboxylate deserve special mention, and in the production of polytetrahydrofuran the preparation from tetrahydrofuran and 1,4-butanediol or H ₂ O as telogen or using short-chain PTHF. The polytetrahydrofuran dicarboxylate is prepared from THF and carboxylic anhydride, preferably acetic anhydride. The invention will be explained in more detail below with the aid of examples.

I. Methods of measurement and determination used

1.1. Measurement of the BET surface

The BET surfaces were determined by adsorbing N _{2 in} accordance with DIN 66131.

1.2. Measurement of the tungsten content

200 mg of the homogenized sample are mixed with approx. 25 g borax lithium fluoride as a melting agent and melted in a platinum crucible at 1000 ° C. The melt is subjected to an X-ray fluorescence analysis. The evaluation is done via external calibration with matrix-adapted comparisons.

1.3. Measurement of the loss on ignition of the TiO ₂ carrier

The loss on ignition was calculated from the initial weight (m ₂₀ ) and the weight after five hours of annealing at 900 ° C in air (m ₉₀ o) as follows:

Loss on ignition [TiO ₂ ] = 1 - m ₉ oo / m ₂ o

1.4. Hammett acidity measurement

The amount of acidic centers with pKs <-3 (“acidity”) was determined by titration with pyrazine as the base in absolute toluene as the solvent with dicinnamalacetone (CAS 622-21-9) as an indicator. The finely ground catalyst is run at 200 ° C. under the exclusion of light under vacuum (<1 mbar) overnight, then about 50 ml of absolute toluene and 1 mg of dicinnamalacetone (dissolved in 1 ml of absolute toluene) are added under argon. 1% by weight solution of pyrazine in absolute toluene, equilibrating for at least 5 hours after each addition of pyrazine, the end point of the titration can be recognized by a color change from blue to red, which becomes clearer if one again shortly before the end point of the titration 1 mg of dicinnamalcetone Wn In general, the titration was carried out as described, for example, in “H. Benesi and B. Winquist, Advances in Catalysis, Vol. 27, 1978, Academic Press, ISBN 0-12-007827-9 " and the references contained therein. 1.5. Cutting hardness measurement

The measurement of the cutting hardness was carried out as follows: 25 randomly selected, optically crack-free extrudates with an average length of 2 to 3 times the diameter are successively loaded with increasing force by a cutting edge of 0.3 mm thickness until the respective extrudate is cut. The force required for this is the cutting hardness N.

1.6. Porosity measurement

The porosity of the catalysts was determined using the mercury intrusion method in accordance with DIN 66133.

1.7. Setting the BET surface area of the TiO ₂ support

Precipitated TiO ₂ * aq with a BET surface area of 275 m ² / g is calcined in a continuously operated rotary tube with a residence time of approx. 1 h at temperatures from 350 to 500 ° C. in air. A uniform material with a defined BET surface area between 135 and 220 m ² / g is obtained.

II. Starting compounds

II.1. Titanium oxides and hydroxides

Possible titanium oxides or hydroxides, which are suitable as support materials for the preparation of the catalysts according to the invention and have been used optionally, are those which are known as S 150, S 140 and S 240 from Kemira, under the designation P 25 from Degussa, as VKR 611, Hombikat UV100 and Hombifine N from Sachtleben, XT 25376 from Norton, DT 51 from Thann et Mulhouse, and Bayoxide T A-DW-1, Bayoxide T AKl from Bayer, are commercially available. II.2. Zirconium oxides and hydroxides

As zirconium oxides or hydroxides for the preparation of the catalysts according to the invention are S97 / 718 from MEL, D9-89 from BASF, XZ 16052 from Norton and HC 15 from SEPR.

II.3. Tungsten and molybdenum compounds

WO ₃ , MoO ₃ , H ₂ WO and ammonium meta- and paratungstate from HC Starck are used as tungsten or molybdenum compounds.

III. General information on the manufacture of the catalyst

iπ.la. Soak the support with the catalytically active compound

To produce the catalyst, the support is soaked in water with the corresponding molybdenum and / or tungsten compound. A soluble pore former, as exemplified above, can also be added to this impregnation solution. In addition, a binder in the form of a powder or in the form of a suspension can optionally be added.

Hl.lb. Mix the carrier with the catalytically active compound

As an alternative to this impregnation process, the carrier can also be mixed with the molybdenum and / or tungsten compound and water. This can e.g. B. in a pan mill or kneader. In addition, a water-soluble or insoluble pore former and a binder in the form of a powder or a suspension can be added. This procedure is compared to watering, as under la. described, preferred. III.2. Spray the obtained mash

An optional intermediate stage is the spraying of the mash thus obtained, the drying and precalcination of the spray material at about 80 to 600 ° C., preferably at 100 to 500 ° C., under oxidizing, inert or reducing, either still or flowing atmosphere oxidizing atmosphere can be air or the like, as inert atmosphere N ₂ , Ar, CO ₂ and as reducing atmosphere organic compounds in inert gas, CO or H ₂ can be used.

III.3. Rolling or kneading the material

The next manufacturing step is followed by the rolling or kneading of the catalyst, in which case a water-soluble or insoluble pore former and a binder can optionally be added.

iπ.4. Deforming the catalyst

Then the catalyst is z. B. deformed by extrusion, extrusion or tableting to shaped bodies such as cylinders, balls, rings, spirals, strands or grit.

III.5. precalcination

Precalcination can now optionally be carried out at approximately 80 to 600 ° C., preferably at 100 to 500 ° C., under an oxidizing, inert or reducing, respectively still or flowing atmosphere.

III.6. final calcination

The final calcination is then carried out at 400 to 900 ° C., preferably at 550 to 850 ° C. and particularly preferably at 600 to 800 ° C., again under an oxidizing, inert or reducing, in each case still or flowing atmosphere and using a Gases such as B. given as an example under 2.. At a temperature of 600 to 800 ° C there is a catalyst with a particularly high space-time yield.

Also used catalysts that have been regenerated by the usual methods, e.g. B. by treatment with solvents, steam or calcining for 0.1 to 10 hours at 300 ° C to 600 ° C in air, CO ₂ or a reducing atmosphere, such as H ₂ or CO, can be used. Furthermore, catalyst powder, shaped bodies and / or catalyst chips can be reused by adding them to the production steps described above.

This final calcination can optionally be followed by a targeted reduction, as has been described in DE-A-196 41 481.

In principle, the catalyst is prepared analogously to the methods described in DE-A-44 33 606 or DE-A-196 49 803, to which reference is hereby expressly made.

IV. Production of PTHF

Since the activities of the respective catalysts according to the invention were checked on the basis of the production of PTHF, this production process is first discussed here and the process variants used in principle are presented.

IV.l. General

In principle, any THF can be used as a monomer for producing PTHF. However, preference is given to using commercially available THF which has been pre-cleaned by acid treatment, as described for example in EP-A 003 112, or by distillation. Suitable telogens in the one-step process are saturated or unsaturated, unbranched or branched alpha, omega-C ₂ to C ₁₂ diols, water, polytetrahydrofuran with a molecular weight of 200 to 700 dartons, cyclic ethers or mixtures thereof. Water, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polytetrahydrofuran with a molecular weight of 200 to 700 daltons, 1,6-hexanediol, 1,8-octanediol are preferred , 1,10-decanediol, 2-butyn-l, 4-diol and neopentyl glycol or mixtures thereof, water, 1,4-butanediol and / or polytetrahydrofuran having a molecular weight of 200 to 700 daltons being particularly preferred.

Carboxylic anhydrides and / or carboxylic anhydride / protonic acid mixtures serve as telogens for the production of PTHF and THF copolymers by the two-stage process. Preference is given to carboxylic anhydrides which are derived from aliphatic or aromatic, poly- and / or monocarboxylic acids which contain 2 to 12, preferably 1 to 8, carbon atoms. Acetic anhydride is particularly preferred. The protonic acids are preferably organic and inorganic acids which are soluble in the reaction system. Preferred carboxylic acids are aliphatic or aromatic poly- and / or monocarboxylic acids which contain 2 to 12, preferably 1 to 8, carbon atoms. Examples of aliphatic carboxylic acids are acetic acid, lactic acid, propionic acid, valeric acid, caproic acid, caprylic acid and pelargonic acid. Examples of aromatic carboxylic acids are phthalic acid and naphthalene carboxylic acid. Of these carboxylic acids, acetic acid is preferably used.

As comonomers, cyclic ethers which can be polymerized to open the ring are preferably three-membered, four- and five-membered rings such as the THF derivatives, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran, cyclic ethers such as 1,3-dioxolane, trioxane, oxetane, substituted oxetanes such as 3,3-dimethyloxetane, 1,2-alkylene oxides, for example ethylene oxide or propylene oxide, are suitable, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran being particularly preferred.

The telogen is expediently fed to the polymerization in solution in the THF, a telogen content of 0.04 to 17 mol%, based on tetrahydrofuran, being preferred. Comonomers are also expediently fed to the polymerization in solution in THF, the comonomer content being up to 30 mol%, preferably 20 mol%, based on tetrahydrofuran. However, it is also possible to separate the polymerization reactor THF and the telogen and / or the comonomer supply. Since the telogen stops the polymerization, the average molecular weight of the PTHF or THF copolymer can be controlled via the amount of telogen used. The more telogen the reaction mixture contains, the lower the average molecular weight of the PTHF or the THF copolymers in question. Depending on the telogen content of the polymerization mixture, PTHF and THF copolymers with average molecular weights of 650 to 5000 Daltons, preferably from 650 to 3000 Daltons and particularly preferably from 1000 to 3000 Daltons can be produced.

The polymerization is generally carried out at temperatures from 0 to 80 ° C., preferably at 25 to 75 ° C., and particularly preferably at 40 to 70 ° C. The pressure used is generally not critical to the result of the polymerization, which is why work is generally carried out at atmospheric pressure or under the autogenous pressure of the polymerization system.

To avoid the formation of ether peroxides, the polymerization is advantageously carried out under an inert gas atmosphere. As inert gases such. B. nitrogen, carbon dioxide or the noble gases are used, nitrogen is preferably used.

The polymerization can be carried out in the presence of hydrogen at hydrogen pressures of 0.1 to 10 bar.

The process according to the invention is preferably operated continuously. However, it is also possible to operate the polymerization stage and / or one, more or all of the work-up stages of the process according to the invention batchwise, but preferably at least the polymerization is preferably carried out continuously.

The reaction can preferably be carried out in conventional reactors or reactor arrangements suitable for continuous processes in suspension or fixed bed mode, in suspension mode for example in loop reactors or stirred reactors, or in fixed bed mode in tubular reactors or fixed bed reactors. Fixed bed mode is preferred. In the fixed bed mode of operation, the polymerization reactor can be operated in the bottom mode, ie the reaction mixture is conducted from bottom to top, or in the trickle mode, ie reaction mixture is passed through the reactor from top to bottom. The starting material mixture (feed) of THF and telogen and / or comonomer is fed continuously to the polymerization reactor, the catalyst loading being 0.05 to 0.8 kg THF / (1 h), preferably 0.1 to 0.6 kg THF / (1 h) and particularly preferably 0.15 to 0.5 kg THF / (1 h).

In addition, the polymerization reactor can be operated in a single pass, that is to say without product recirculation, or in circulation, that is to say the polymerization mixture leaving the reactor is circulated. In the circulation mode, the ratio of circulation to inlet is <100: 1, preferably <40: 1 and particularly preferably <30: 1.

IV.2. Continuous THF polymerization: variant A

150 g of catalyst were installed in a fixed bed reactor without circulation and this was then dried in a stream of N at 24 ° C. for 24 hours. The reactor was then cooled to 60 ° C. and started up at a load of 45 g / h with a mixture of 4000 pp of 1,4-butanediol in THF (tetrahydrofuran). The discharge was collected daily and THF and butanediol were removed by heating in vacuo (0.3 mbar, 120 ° C.). The number average molecular weight was then measured for the PTHF thus obtained. The butanediol content in the starting material (feed) was then varied until the average molecular weight of the PTHF was M = 2000 + 200 on three successive days. THF sales were averaged over these three days.

IV.3. Continuous THF polymerization: variant B

In a fixed bed reactor without circulation, 200 g of catalyst were installed and this was then dried for 24 hours at 200 ° C. in a stream of N ₂ . The reactor was then cooled to 60 ° C. and started up at a load of 50 g / h with a mixture of 4000 ppm of 1,4-butanediol in THF. The discharge was collected daily and THF and butanediol were removed by heating in vacuo (0.3 mbar, 120 ° C.). The weight average of the molecular weight was then measured for the PTHF contained in this way. The added butanediol content was then varied until three consecutive days mean molecular weight of the PTHF was 2000 + 200. THF sales were averaged over these three days.

IV.4. Discontinuous THF polymerization

The batch polymerization experiments were carried out in 40 ml GC vials under an argon atmosphere. 5 g of catalyst strands which had been dried in an O ₂ / N ₂ stream (“synthetic air”) at 400 ° C. for 18 hours at 400 ° C. before being used to remove adsorbed water were dissolved in 20.75 g of butanediol-containing THF (butanediol concentration The mixture was cooled, the catalyst was filtered off and washed three times with 10 g of THF each time, the filtrates were combined, concentrated at 70 ° C./20 mbar on a rotary evaporator and weighed ,

rV.5. Measurement of the PTHF molecular weight

The molecular weight is determined by determining the hydroxyl number in polytetrahydrofuran. The hydroxyl number is understood to mean that amount of potassium hydroxide in mg which is equivalent to the amount of acetic acid bound in the acetylation of 1 g of substance. The hydroxyl number is determined by the esterification of the hydroxyl groups present with an excess of acetic anhydride.

H- [O (CH ₂ ) ₄ ] "- OH + (CH ₃ CO) ₂ O -" CH ₃ CO- [O (CH ₂ ) ₄ ] _n -O-COCH ₃ + H ₂ O

After the reaction, the excess acetic anhydride is hydrolyzed with water according to the following reaction equation

(CH ₃ CO) ₂ O + H ₂ O → 2 CH ₃ COOH

and back titrated as acetic acid with sodium hydroxide solution. Catalysts - examples

I. Examples of setting a transport pore size of> 25 nm and one

Pore volume of at least 50 mm / g in the finished catalysts

Comparative Example 1

130 kg TiO ₂ * aq (= 100 kg TiO ₂ ), 26.7 kg tungstic acid (= 25 kg WO ₃ ) with 1.52 kg H ₃ PO ₄ (85%) and 46.7 kg H ₂ O compacted, the resulting paste extruded and shaped into strands of 4 mm in diameter. These were dried at 170 ° C and then calcined at 690 ° C for 2 hours.

example 1

119 kg TiO ₂ * aq (= 95.6 kg TiO ₂ ), 25.6 kg tungsten acid (= 23.9 kg WO ₃ ) with 1.46 kg H3PO4 (85%) and 48 kg H ₂ O compacted, the resulting paste is extruded and shaped into strands of 4 mm in diameter. These were dried at 170 ° C and then calcined at 690 ° C for 2 hours.

Example 2 150.2 g TiO ₂ * aq (= 115.7 g TiO ₂ ), 40.46 g tungstic acid (= 37.63 g WO ₃ ) with 94 g stearic acid, 9.4 g tartaric acid, 2 , 2 g of H ₃ PO ₄ (85%) and 92 g of H ₂ O are kneaded and the resulting paste is shaped into strands of 4 mm in diameter. These were dried in a stream of N ₂ at 400 ° C. for 4 hours and then calcined in air at 650 ° C. for 3 hours.

Example 3

In a laboratory kneader, 200 g TiO ₂ * aq (= 160 g TiO ₂ ), 43 g tungstic acid (= 40 g WO ₃ ) with 48.6 g stearic acid, 12.2 g tartaric acid, 38.6 g aqueous silica sol (15.8 % SiO ₂ ) and 40 g of H ₂ O and kneaded the resulting paste into strands of 4 mm in diameter. These were then air dried at 350 ° C for 2 hours and air calcined at 700 ° C for 3 hours. Example 4

128.7 g of TiO ₂ * aq (= 99 g of TiO), 35.4 g of tungstic acid (= 33 g of WO ₃ ), 65.9 g of oxalic acid, 6.9 g of methyl cellulose and 70 g of H ₂ O were kneaded in a laboratory kneader and the resulting paste is deformed into strands of 4 mm in diameter. These were then calcined in air at 650 ° C. for 2 hours.

Example 4a

100 g of TiO ₂ * aq (= 80 g of TiO ₂ ), 31.3 g of ammonium paratungstate (= 28.2 g of WO ₃ ), 91.9 g of oxalic acid, 4 g of polyvinyl alcohol, 4 g of polyethylene oxide and 80 g of H were mixed in a laboratory kneader ₂ O kneaded and the resulting paste formed into strands of 4 mm in diameter. These were then calcined in air at 650 ° C for 1.5 hours.

Example 5

143.2 g of TiO ₂ * aq (= 110 g of TiO ₂ ), 29.6 g of tungstic acid (= 27.5 g of WO ₃ ), 68.7 g of stearic acid, 6.9 g of tartaric acid and 60.8 g were mixed in a laboratory kneader Guanidinium carbonate, 1.6 g H ₃ PO ₄ (85%) and 80 g H ₂ O kneaded and the resulting paste is deformed into strands of 4 mm in diameter. These were dried in a stream of N ₂ at 400 ° C. for 4 hours and then calcined in air at 650 ° C. for 3 hours.

Example 6

217.5 g of TiO ₂ * aq (= 167.6 g of TiO ₂ ), 44.9 g of tungstic acid (= 41.8 g of WO ₃ ), 104.4 g of ammonium citrate, 10.4 g of tartaric acid, 2 , 5 g of H ₃ PO ₄ (85%) and 41.5 g of 25% NH ₃ solution, kneaded and the resulting paste was deformed into strands of 4 mm in diameter. These were calcined in air at 650 ° C for 3 hours.

Example 7

143 g TiO ₂ * aq (= 110 g TiO ₂ ), 29.6 g tungstic acid (= 27.5 g WO ₃ ), 68.7 g guanidinium carbonate, 35 g formic acid, 6.9 g tartaric acid, 1 , 6 g of H3PO4 (85%) and 15 g of H ₂ O kneaded and the resulting paste deformed into strands of 4 mm in diameter. These were calcined in air at 650 ° C for 3 hours. Example 8

150 g of TiO ₂ * aq (= 115.7 g of TiO ₂ ), 40.46 g of tungstic acid (= 37.63 g of WO ₃ ) with 94 g of gelatin, 9.4 g of tartaric acid, 2.2 g of H were mixed in a laboratory kneader ₃ PO ₄ (85%) and 117 g H ₂ O kneaded and the resulting paste is deformed into strands of 4 mm in diameter. These were then calcined in air at 700 ° C for 3 hours.

Example 9

150.2 g of TiO ₂ * aq (= 115.7 g of TiO ₂ ), 40.46 g of tungstic acid (= 37.63 g of WO ₃ ) with 94 g of pure, soluble starch, 9.4 g of tartaric acid were mixed in a laboratory kneader. 2.2 g of H ₃ PO ₄ (85%) and 140 g of HO were kneaded and the resulting paste was shaped into strands of 4 mm in diameter. These were then calcined in air at 700 ° C for 3 hours.

Example 10

150.2 g of TiO ₂ * aq (= 115.7 g of TiO ₂ ), 40.46 g of tungstic acid (= 37.63 g of WO ₃ ) with 93.9 g of cold-ground paraffin, 9.4 g of tartaric acid were mixed in a laboratory kneader , 2.2 g H ₃ PO ₄ (85%) and 100 g H ₂ O kneaded and the resulting paste is deformed into strands of 4 mm in diameter. These were then dried in a stream of N ₂ at 400 ° C. for 4 hours and calcined in air at 700 ° C. for 3 hours.

Example 11

160 g of TiO ₂ * aq (= 128 g of TiO ₂ ), 34.4 g of tungstic acid (= 32 g of WO ₃ ) with 77.8 g of carbon black (Printex 75, from Degussa), 9.8 g of tartaric acid were mixed in a laboratory kneader , 2.3 g of H ₃ PO ₄ (85%), 20.4 g of alkali-free lutensol and 120 g of H ₂ O kneaded and the resulting paste deformed into strands of 4 mm in diameter. These were then dried in a stream of N ₂ at 400 ° C. for 4 hours and calcined in air at 600 ° C. for 8 hours.

Example 12

In a beaker, 200 g TiO ₂ * aq (= 160 g TiO ₂ ), 41.4 g H ₃ PW ₁₂ O ₄₀ * aq (= 33.2 g WO ₃ ) were stirred with 520 g H ₂ O and at 60 ° C evaporated in vacuo. The material was then heated to 500 ° C. in a stream of N ₂ and calcined in air at this temperature for 2 hours. The product was finely ground in an analytical mill, kneaded in a laboratory kneader with 120.8 g of H ₂ O and the resulting paste was shaped into strands of 4 mm in diameter. These were then calcined in air at 700 ° C for 3 hours. Example 13

375 g TiO ₂ * aq (= 300 g TiO ₂ ), 103.4 g H ₃ PW ₁₂ O ₄₀ * aq (= 82.9 g WO ₃ ) were stirred in a beaker with 1040 g H ₂ O and at 60 ° C evaporated in vacuo. The material was then heated to 500 ° C. in a stream of N ₂ and calcined in air at this temperature for 2 hours. The product was ground in a Spkalsfrahlmühle at 8 bar to particles of an average size of 0.8 microns, kneaded in a laboratory kneader with 120.8 g H ₂ O and the resulting paste was molded into strands of 4 mm in diameter. These were then calcined in air at 650 ° C. for 1 hour.

Example 14

8.38 kg TiO ₂ * aq (= 6.44 kg TiO ₂ ) and 2.00 kg H ₃ PW ₁₂ O ₄₀ * aq (= 1.61 kg WO ₃ ) were mixed with 138 kg H ₂ O and mixed in one Spray tower sprayed at 120 ° C to a powder with an average particle size of 2.7 microns, which was then calcined at 500 ° C for 2 hours. 200 g of this spray powder were kneaded with 10 g of methyl cellulose and 120 g of H ₂ O in a laboratory kneader and the resulting paste was shaped into strands of 4 mm in diameter. These were then calcined in air at 700 ° C for 3 hours.

Example 15

7.86 kg TiO ₂ * aq (= 6.04 kg TiO ₂ ) and 2.50 kg H ₃ PW ₁₂ O ₄₀ * aq (= 2.01 kg WO ₃ ) were mashed with 138 kg HO and added in a spray tower Sprayed 120 ° C to a powder with an average particle size of 2.6 microns, which was then calcined at 500 ° C for 2 hours. 200 g of this spray powder were kneaded with 10 g of methyl cellulose and 120 g of H ₂ O in a laboratory kneader and the resulting paste was shaped into strands of 4 mm in diameter. These were then calcined in air at 650 ° C. for 3 hours.

Example 16

7.86 kg TiO ₂ * aq (= 6.04 kg TiO ₂ ) and 2.50 kg H ₃ PWι ₂ O ₄ o * aq (= 2.01 kg WO ₃ ) were mixed with 138 kg H ₂ O and mixed in a spray tower at 120 ° C to a powder with an average particle size of 2.6 microns, which then for 2 hours 500 ° C was calcined. 200 g of this spray powder were kneaded with 6 g of polyethylene oxide and 116 g of H ₂ O in a laboratory kneader and the resulting paste was shaped into strands of 4 mm in diameter. These were then calcined in air at 650 ° C. for 2 hours.

A comparison of the catalysts according to Comparative Example 1 and Examples 1 to 16 with regard to the use in the polymerization of THF is given in Table 1. THF was polymerized batchwise, as described above under IV.4. explained. The experiments show that the use of catalysts with a high proportion of transport pores> 25 nm in the process according to the invention leads to an increase in activity in all cases. When using the method according to the invention, the capacity of existing plants for the production of PTHF can therefore be significantly increased without retrofitting, or future plants can be built correspondingly smaller and therefore with a correspondingly reduced investment volume.

Table 1: Comparison of the example catalysts

II. Examples for the setting of a tungsten content of> 10.1 to <20.9 μmol / m ²

Comparative Example II. 1

100 g of TiO ₂ * aq (= 78 g of TiO ₂ ), 15.5 g of ammonium paratungstate (= 13.8 g of WO ₃ ) and 80.9 g of anhydrous oxalic acid were compressed with 75 g of H ₂ O in a laboratory kneader, the resulting mass extruded and shaped into strands of 4 mm in diameter. These were calcined at 200 ° C for 2 hours, at 500 ° C for 3 hours and at 600 ° C for 3 hours.

Comparative Example II. 2

184.7 g of TiO ₂ * aq (= 144 g of TiO ₂ ), 29 g of tungstic acid (= 27 g of WO ₃ ) and 67 g of H ₂ O were compressed in a laboratory kneader, the resulting mass was extruded and shaped into strands of 4 mm in diameter , These were dried at 105 ° C and then calcined at 775 ° C for 24 hours.

Comparative Example II. 3

In a pan mill, 123.1 kg TiO ₂ * aq (= 96 g TiO ₂ ), 25.7 kg tungsten acid (= 24 kg WO ₃ ) and 6.09 kg tartaric acid with 2.95 kg aqueous H ₃ PO ₄ (= 1.764 kg of P ₂ O ₅ ) and 45 kg of H ₂ O are compressed, the resulting mass is extruded and shaped into strands with a diameter of 4 mm. These were dried at 105 ° C and then calcined at 690 ° C for 2 hours.

Comparative Example II. 4 180 g of TiO ₂ * aq (= 144.4 g of TiO ₂ ), 38.7 g of tungstic acid (= 36.1 g of WO ₃ ) and 9.02 g of tartaric acid were mixed with 2.21 g of water in a laboratory kneader H ₃ PO ₄ (= 1.32 g P ₂ O ₅ ) and 73 ml H ₂ O compressed, the resulting mass extruded and formed into strands of 4 mm in diameter. These were dried at 105 ° C and then calcined at 690 ° C for 48 hours.

Comparative Example II. 5

180 g of TiO ₂ * aq (= 140 g of TiO ₂ ), 69.9 g of ammonium paratungstate (= 62.2 g of WO ₃ ) and 37.5 g of anhydrous oxalic acid with 53 g of H ₂ O were mixed in a laboratory kneader compacted, the resulting mass extruded and formed into strands of 4 mm in diameter. These were dried at 35 ° C and then calcined for 2 hours at 200 ° C and 3 hours at 500 ° C.

Comparative Example II. 6

125 g of TiO ₂ * aq (= 97.5 g of TiO ₂ ), 48.5 g of ammonium paratungstate (= 43.2 g of WO ₃ ) and 43.4 g of anhydrous oxalic acid were compressed with 56 g of H ₂ O in a laboratory kneader resulting mass extruded and shaped into strands of 4 mm in diameter. These were dried at 40 ° C and then calcined for 2 hours at 200 ° C and 7 hours at 500 ° C and 3 hours at 670 ° C.

Comparative Example II. 7

In a pan mill 66.6 kg TiO ₂ * aq (= 51.5 kg TiO ₂ ), 31.1 kg ammonium paratungstate (= 27.7 kg WO ₃ ) were compressed with 20.4 kg oxalic acid dihydrate and 15 kg HO, the resulting Extruded mass and shaped into strands of 4 mm in diameter. These were dried at 90 ° C and then calcined for 2 hours at 200 ° C, 3 hours at 500 ° C and 3 hours at 510 ° C.

Comparative Example II. 8 The catalyst from Example 7 was additionally calcined at 690 ° C. for 12 hours.

Example II. 1

184.7 g of TiO ₂ * aq (= 144 g of TiO ₂ ), 29 g of tungstic acid (= 27 g of WO ₃ ) and 67 g of H ₂ O were compressed in a laboratory kneader, the resulting mass was extruded and shaped into strands of 4 mm in diameter , These were dried at 105 ° C and then calcined at 675 ° C for 16 hours.

Example II. 2

119.1 kg of TiO ₂ * aq (= 95.6 kg of TiO ₂ ), 25.6 kg of tungstic acid (= 23.9 kg of WO ₃ ) and 5.97 kg of tartaric acid were mixed with 1.46 kg of aqueous H _{3 in a} pan mill PO ₄ (= 0.872 kg P ₂ O ₅ ) and 48 kg H ₂ O compressed, the resulting mass extruded and shaped into strands of 4 mm in diameter. These were dried at 105 ° C and then calcined at 690 ° C for 2 hours. Example II.3

119.1 kg of TiO ₂ * aq (= 95.6 kg of TiO ₂ ), 25.6 kg of tungstic acid (= 23.9 kg of WO ₃ ) and 5.97 kg of tartaric acid were mixed with 1.46 kg of aqueous H _{3 in a} pan mill PO ₄ (= 0.872 kg P ₂ O ₅ ) and 48 kg H ₂ O compressed, the resulting mass extruded and shaped into strands of 4 mm in diameter. These were dried at 120 ° C and then calcined at 400 ° C for 2 hours and at 750 ° C for 3 hours.

Example II. 4 180 g of TiO ₂ * aq (= 140 g of TiO ₂ ), 71.7 g of ammonium paratungstate (= 63.8 g of WO ₃ ) and 37.8 g of anhydrous oxalic acid were compressed with 48 g of H ₂ O in a laboratory kneader , the resulting mass is extruded and shaped into strands of 4 mm in diameter. These were dried at 90 ° C for 2 hours and then calcined at 200 ° C, 5 hours at 500 ° C and 3 hours at 650 ° C.

Example II. 5

180 g of TiO ₂ * aq (= 140 g of TiO ₂ ), 71.7 g of ammonium paratungstate (= 63.8 g of WO3) and 37.8 g of anhydrous oxalic acid were compressed with 48 g of H ₂ O in a laboratory kneader, and the resulting mass was extruded and deformed into strands of 4 mm in diameter. These were dried at 35 ° C and then calcined at 200 ° C, 5 hours at 500 ° C and 3 hours at 620 ° C for 2 hours.

Example II. 6

In a pan mill, 66.6 kg TiO ₂ * aq (= 51.5 kg TiO ₂ ), 31.1 kg ammonium paratungstate (= 27.7 kg WO ₃ ) were compressed with 20.4 kg oxalic acid dihydrate and 15 kg H ₂ O, the resulting mass is extruded and shaped into strands with a diameter of 4 mm. These were dried at 90 ° C. and then calcined at 200 ° C. for 2 hours, at 500 ° C. for 3 hours and at 610 ° C. for 3 hours.

The catalysts thus prepared were in the above under IV.3. Continuous THF polymerisation indicated as variant B is used. The results obtained are listed in Table 2, the last column of which shows the THF conversion in percentages. Table 2: Comparison of the example catalysts

III. Examples for the setting of a defined BET surface of the oxidic carrier material

Example HI. 1: Preparation of the catalyst variant 1

720 g of precalcined TiO ₂ * aq with the BET surface areas specified in Table 1, ammonium paratungstate - corresponding to a molar ratio of Ti to W of 6.77 - and 156.4 g of anhydrous oxalic acid with a suitable amount of H were mixed in a laboratory kneader ₂ O compacted, the resulting mass extruded and formed into strands of 4 mm in diameter. The amount of water required depends on the type of kneader used and the TiO ₂ material, it has no effect on activity and acidity. It is typically 240 to 340 g. The modeling clay was dried at 35 ° C. overnight, then calcined stepwise for 2 hours at 200 ° C. and for a further 3 hours at 500 ° C. in an air stream. Then, the final catalyst was calcined at the temperature shown in Table 3 for one hour. Table 3 gives the respectively determined ignition losses of the TiO ₂ * aq, the temperatures used for the final calcination to the finished catalyst, the maximum BET surface area and the BET surface area of the catalysts thus obtained, and the calculated BET loss, the acidity at pKs < -3 and the turnover of the PTHF polymerization. It can be clearly seen from the values given in Table 3 that the reduced surface of the thermally pretreated TiO * aq is less susceptible to further sintering and leads to catalysts based on Wθ ₃ -TiO ₂ , which have a significantly increased number of centers with pKs Have <- 3. Particularly in the area of a BET surface area of the treated TiO ₂ * aq support around 200 m ² / g, there are maximum acidities and activities for acid catalysis. The PTHF polymerization was carried out according to the above under IV.2. Continuous process specified as variant A is carried out.

Table 3: Comparison of the catalysts

Example HI.2: Preparation of the catalyst under water vapor atmosphere variant 2a

2 kg of freshly precipitated and dried at 100 ° C TiO ₂ * aq (78% TiO ₂ ) was at 400 ° C in a non-air-flow rotary tube - ie under the water vapor atmosphere escaping from the TiO ₂ * aq - for 3 hours at 400 ° C in discontinuous procedure (batch procedure) calcined. The result was a material with a BET surface area of 143 m ² / g and a loss on ignition of 9%. 720 g of this material were then kneaded with 322 g of ammonium paratungstate (88% WO ₃ ), 156 g of oxalic acid and 290 g of HO and shaped into strands with a diameter of 4 mm. These were then calcined stepwise at 200 ° C. for 2 hours and at 500 ° C. for 3 hours, and finally calcined at 575 ° C. for one hour to give the finished catalyst. The catalyst strands had an average cutting hardness of 34 N and achieved a conversion of 5.2% in the continuous THF polymerization test.

Example III.2: Preparation of the catalyst under steam atmosphere variant 2b

1.2 kg of freshly precipitated and dried at 100 ° C. TiO ₂ * aq (78% TiO ₂ ) was precalcined within 5 hours in a continuously operated rotary tube with a 4 cm inner diameter at 400 ° C. and a residence time of 20 minutes. The rotary tube was flowed through with 400 standard liters of air per hour. In addition, 60 ml of liquid H ₂ O per hour were metered into the air stream. The result was a material with a BET surface area of 195 m ² / g and a loss on ignition of 8%. 216 g of this material were then kneaded with 96.6 g of ammonium paratungstate (88% WO ₃ ), 46.8 g of oxalic acid and 80 g of H ₂ O and shaped into strands with a diameter of 4 mm. These were then calcined stepwise at 200 ° C. for 2 hours and at 500 ° C. for 3 hours, and finally calcined at 575 ° C. for one hour.

The catalyst strands had an average cutting hardness of 20 N and achieved a conversion of 6.0% in the continuous THF polymerization test.

The comparative examples given below show the influence of the addition of water during the pre-calcination of the carrier material on the cutting hardness and, on the other hand, the influence of the pre-calcination as such on the activity of the finished catalyst. Comparative Example III. 1 in terms of cutting hardness

1.2 kg of freshly precipitated and dried at 100 ° C. TiO ₂ * aq (78% TiO ₂ ) was precalcined as above, but no H ₂ O was metered into the rotary tube. The result was a material with a BET surface area of 211 m ² / g and a loss on ignition of 9%. 720 g of this material were then kneaded with 322 g of ammonium paratungstate (88% WO ₃ ), 156 g of oxalic acid and 350 g of HO and shaped into strands with a diameter of 4 mm. These were then calcined stepwise at 200 ° C. for 2 hours and at 500 ° C. for 3 hours, and finally calcined at 575 ° C. for one hour. The catalyst strands had an average cutting hardness of 8 N and achieved a conversion of 7.5% in the continuous THF polymerization test.

In this comparative example, the carrier material TiO ₂ * aq was produced according to the invention, but was precalcined according to variant 1 without the addition of water. The catalysts produced with this support proved to be mechanically unstable in comparison to the catalysts produced according to variants 2a and 2b

Comparative Example III. 2 in terms of catalyst activity

750 g of freshly precipitated and dried at 100 ° C. TiO ₂ * aq (78% TiO ₂ ) were kneaded with 230 g of ammonium paratungstate (88% WO ₃ ), 156 g of oxalic acid and 190 g of H ₂ O and shaped into strands with a diameter of 4 mm , These were then calcined gradually at 200 ° C for 2 hours and at 500 ° C for 3 hours and at 575 ° C for 1 hour.

The catalyst strands had an average cutting hardness of 26 N and achieved a conversion of 3.2% in the continuous THF polymerization test.

In this comparative example, the base material TiO ₂ * aq was not precalcined at all. Compared to the catalysts produced according to the invention according to variants 1 and 2a, 2b, a catalyst with lower activity was obtained.

Claims

claims

1. A catalyst which contains a catalytically active amount of at least one oxygen-containing molybdenum and / or tungsten compound on an oxidic support material and which, after the precursor compounds of the catalytically active compounds have been applied to the support material or a support material precursor at temperatures of 400 ° C. to 900 ° C has been calcined, characterized by a porosity of the catalyst

Transport pores each with a diameter of> 25 nm, and a volume of these transport pores of at least 50 mm ³ / g.

2. Catalyst according to claim 1, characterized by a content of molybdenum and / or tungsten, based on the finished catalyst, of:

x μmol (tungsten and / or molybdenum) / m ²

with 10, l <x <20.9.

3. Catalyst according to claim 1 or 2, characterized by a BET surface area of 25 to 200 m ² / g, preferably 40 to 150 m ² / g and particularly preferably 50 to 120 m ² / g.

4. Catalyst according to one of claims 1 to 3, characterized in that the oxidic support material has a BET surface area of 135 to 220 m ² / g.

5. Catalyst according to claim 4, characterized in that the oxidic support material has a BET surface area of 170 to 220 m ² / g, preferably 190 to 220 m / g.

6. Catalyst according to one of claims 1 to 5, characterized by an acidity at pKs <-3 of at least 10 μmol / g.

7. Catalyst according to one of claims 1 to 6, characterized by an acidity at pKs <-3 of at least 70 μmol / g, preferably of at least 90 μmol / g, in the dry state.

8. Catalyst according to one of claims 1 to 7, characterized in that the catalyst contains a catalytically active amount of at least one oxygen-containing tungsten compound.

9. Catalyst according to one of claims 1 to 8, characterized in that the oxidic support material is zirconium dioxide or titanium dioxide, preferably titanium dioxide.

10. Catalyst according to one of claims 1 to 9, characterized in that the catalyst contains 0.1 to 70% by weight, preferably 5 to 40% by weight, particularly preferably 10 to 35% by weight, of the catalytically active compound (s) , calculated as M0O ₃ and / or WO ₃ and based on the total weight of the catalyst.

11. Catalyst according to one of claims 1 to 10, characterized by a content of pore formers of up to 200% by weight, preferably up to 100% by weight, particularly preferably up to 60% by weight, in each case based on the proportion of the catalytically active

Connection together with the carrier material.

12. Catalyst according to one of claims 1 to 11, characterized in that the catalyst contains up to 15% by weight, preferably up to 10% by weight, particularly preferably up to 8% by weight of sulfate and / or phosphate.

13. A process for producing a catalyst which contains a catalytically active amount of at least one oxygen-containing molybdenum and / or tungsten compound on an oxidic support material, with the following steps: - precipitating the oxidic support material, thermal treatment of the oxidic support material to adjust a BET surface from 135 - 220 m ² / g,

Application of the catalytically active compounds) or their precursor compound (s) to the support material and - calcining the catalyst thus produced at temperatures from 400 ° C to

900 ° C to the finished catalyst.

14. The method according to claim 13, characterized in that the thermal treatment of the oxidic carrier material is carried out in a water-containing atmosphere, the more than 10 vol.%, Preferably more than 20 vol.% And particularly preferably more than 30

Vol.% Contains water.

15. The method according to claim 13 or 14, characterized in that the catalytically active compound (s) is applied in a molar ratio of carrier material to catalytically active compound of 5.0-7.5, preferably 6.0-7.0 or become.

16. The method according to any one of claims 13 to 15, characterized in that the catalyst is calcined first at 100 - 600 ° C and then at temperatures up to 900 ° C, preferably up to 700 ° C to the finished catalyst.

17. The method according to any one of claims 13 to 16, characterized in that the calcining is carried out with a gradual increase in temperature.

18. A process for the preparation of polytetrahydrofuran, tetrahydrofuran copolymers, diesters or monoesters of these polymers by polymerizing tetrahydrofuran in the presence of at least one telogen and / or comonomer using a catalyst according to any one of claims 1 to 12.

19. A process for the preparation of polytetrahydrofuran, tetrahydrofuran copolymers, diesters or monoesters of these polymers by polymerizing tetrahydrofuran in the presence of at least one telogen and / or comonomer using a catalyst which has been obtained by a process according to any one of claims 13 to 17 ,

20. The method according to claim 18 or 19 for the production of polytetrahydrofuran.

21. The method according to any one of claims 18 to 20 for the production of polytetrahydrofuran from tetrahydrofuran and 1,4-butanediol or H ₂ O as telogen.

22. The method according to claim 18 or 19 for the production of polytetrahydrofuran from tetrahydrofuran and carboxylic anhydride.