DE2121732A1 - Process for the preparation of alkoxides - Google Patents

Description

DR, BERG DIPL.-ING. STAPF

PATENT LAWYERS 2 I 2 I 7 3 2

β MUNICH 8O, MAUERKIRCHERSTR. 45

Dr. Berg Dipl.-tng. Darning. 8 MOndian 80, Mauerkircherstraße 45 Your reference your letter Our reference date - 3 | Μδΐ 1971

Attorney's file 20 935 addendum to patent ......

(Patent application 6 6ι

33ty

Monsanto Chemicals Limited London S.W.1 England

"Process for the preparation of alkoxides ¹¹

This invention relates to a method of manufacture

, on alkoxides, _{209810 / m2}

Case No. R-637 -2 «

(Mil) 48 82 72 <9β «2 72) 48 70 43 (W 70 43> 48 3310 (98 3310) Teleflammei BERGSTAPFPATENT Munich TELEX 05 24 5 «IEKG d Bank ι Bavarian · Vertinsbonk MOnchm 453100 Poihdiecki Manchen <53

In the British patent application Fr. 7342/69 (German patent application P 20 05 835.9-42) is a method for Preparation of a silicon alkoxide (alkyl silicate) having 1 to 3 carbon atoms per alkoxy group described in which an electric current is passed through a liquid medium containing a solution in a monohydric alcohol 1 to 3 carbon atoms per molecule of an acid or a metal salt that is compatible with the monohydric alcohol · «· is borrowed, contains and that is ionized to a sufficient extent and that is present in sufficient quantity to the Puncture an IrägerelektοIyts and take over the medium no more than 3 wt. # of water, based on the weight of the monohydric alcohol, containing one Anode, which contains silicon, is used in contact with the liquid medium and electrical current is used until the Silicon alkoxide is present in the liquid medium and still passes through for a further time.

It has now been found that ammonium and quaternary ammonium salts can be used as carrier electrolytes in such processes can serve and that, when these salts are used, the process for the preparation of alkoxides of other elements can be used in addition to silicon alkoxides.

The present process is used to produce an Aiko- xida eia®® elements of group IV or Va of the periodic table Element® MaMele j ew, which has an ordinal number from 14 to

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has or a transition element of the fourth period and group Ib, lib, HIa, Via, VIIa or VIII of the period

x
system of elements, for which an electric current is passed through an essentially anhydrous, liquid medium containing a solution with a monohydric alcohol of 1 to 4 carbon atoms per molecule, an ammonium or a quaternary ammonium salt which ionizes to a sufficient extent and in sufficient quantity is present to serve as a supporting electrolyte using an anode containing the element in contact with the liquid medium

The process according to the invention is particularly useful for the preparation of alkoxides, for example the methoxides, ethoxides and isopropoxides, of silicon, germanium, zirconium, titanium, chromium, iron, zinc and tantalum. The alkoxides of these elements have many uses. For example, silicon alkoxides (alkyl silicates) are suitable as binders for the manufacture of refractory articles such as molds for metal casting. The alkoxides of zirconium, titanium and tantalum can be used as binders in the manufacture of molds for casting metals that are high. Have melting points than silicon, or they can be used for metals that react with silicon dioxide at their casting temperatures. Titanium and zirconium alkoxides are useful as gelling, hardening and drying agents for natural and epoxy resins ^x Mendeleev

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121732

and as components for heat-resistant paints, water-repellent Compounds and antifouling preparations. Alkoxides of titanium, zirconium, chromium and iron are used in the manufacture of catalyst preparations containing these metals, suitable. Well known processes previously used to prepare these alkoxides often resulted over several implementation procedural stages while they in the method according to the invention directly from the Element to be produced.

The monohydric alkanol used in the process can be, for example, methanol, ethanol, propanol, isopropanol, be n-butanol, isobutanol or a mixture of these alkenols, Alkanols having 1 to 3 carbon atoms per molecule are preferred, and particularly good results have been obtained with Obtain ethanol.

The ammonium and quaternary ammonium salts which can be used in the process according to the invention include ammonium chloride, Ammonium nitrate, quaternary ammonium salts of

formula

- κι

E,

in which the Eeste E ..,

E ₂ , E, and E. each is an alkyl, aryl, cycloalkyl or aralkyl radical, or the radicals H. and Ep or E., Ep and E, together with the nitrogen atom, form a heterocyclic input and X is chloride ₉ Broaiet, Iodide or a half

-5-

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sulfate is like tetramethylammonium chloride, tetramethylammonium bromide, Tetraethylammonium chloride, tetraethylammonium bromide, Dimethylpiperidine bromide, methylpyridine chloride, Ethylpyridine chloride, trimethylphenylammonium chloride, Tetramethylammonium sulfate, benzyltrimethylammonium iodide. Tetramethylammonium chloride is the preferred quaternary ammonium salt. The ammonium salt or the quaternary The ammonium salt must be anhydrous and have sufficient solubility and ionization in the liquid medium, under Have formation of a solution that has sufficient conductivity to serve as a current carrier. The amount of salt whose Solution in the liquid medium required to obtain a practical conductivity depends unmistakably on a number of factors. However, there is a practical lower limit for the specific conductivity of the

_cj -1

Liquid given at approximately 2.4 x 10 ohms . If the conductivities are lower, the process is unnecessarily extended. The liquid medium preferably has a specific

-5 fish conductivity of at least 3 »0 χ 10, for example a conductivity in the range of 10 to 10 ^J ohm cm, such as a conductivity of 3 χ 10"" ⁴ to 5 χ 10" ⁴ "ohm" ¹ cm "" ¹ .

Satisfactory results are obtained using essentially saturated solutions of ammonium chloride in ethanol or solutions that are about 6 to 12 grams

Contains tetramethylammonium chloride per liter of ethanol.

'■ -6-

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The anode used can consist of the essentially pure element, but the presence is small of impurities are not detrimental to the process, and alloys are sometimes for economic reasons preferred. Furthermore, in some cases the conductivity of the pure element is too low for practical purposes. In general, the specific resistance of the anode material should not exceed 10 ohm-cm.

In the case of silicon, a compound or alloy of silicon is preferred as a semiconductor grade of the element. Ferrosilicon has been found to be particularly suitable. The silicon content of the ferrosilicon, for example, in the range of 60 to 99 or 70 to 77 wt _# $ and in typical cases in the range of 70 to 80, 90 to 95 or 97 to 99 percent by _e # are. In the case of titanium, zircon, germanium and tantalum, pieces of scrap or pressed scrap can be used, with or without a prior cleaning process.

Any inert, conductive material can serve as the cathode. Graphite is a useful cathode material that a considerable advantage in terms of cost other functionally suitable materials, such as platinum or silver.

The current used in the process according to the invention is a simple direct current or a rectified one AC current that can be balanced. The electricity

_7_

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density at the anode can typically be in the range of 7 to 200 mA / cm, although the operation is possible at current densities outside this range. the end For economic reasons, the voltage used across the decay voltage of the system should be as low as possible being held. In practice, the working voltage is determined by certain factors, such as the design of the cell and the electrolyte concentration, although extensive changes are possible.

The temperature at which the electrolysis is carried out is not critical. Generally, the most convenient method is to equip the electrolytic cell with a reflux condenser to operate the process at the boiling point of the liquid medium. Often the resistance heating by the current is sufficient to keep the liquid medium at its boiling point. However, the method can also at lower temperatures, beispiels- ä from 10 ⁰ C to the boiling point of the liquid medium can be performed, but it is then necessary to provide cooling devices in general.

It is common, however, to carry out the electrolysis in the presence of an inert atmosphere such as nitrogen this is not essential. The liquid medium and the current carrier must be anhydrous because there is some Water would hydrolyze the alkoxide to an oxide sol. An alkoxide could be produced in the manner.

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- ο -

that a current is passed through a liquid medium, which does not contain more than $ 5 water, whereby the Electrolysis until the water is consumed and then carries out to form the alkoxide. However is a obviously such a process is not very effective and the pure product is very difficult to obtain from the crude reaction product to isolate. Also, the presence of water can also reduce the passivity of the element in some cause falls.

If desired, the liquid medium can be an inert, organic liquid which is miscible with the liquid medium is, for example, a ketone, an ether or an ester as a liquid diluent

For example, the presence of up to $ 25 acetone, can be tolerated based on the volume of the liquid medium.

The alkoxides produced by the process according to the invention can be purified by any conventional process usually the excess becomes monovalent Alkanol is evaporated from the reaction product and the residue is distilled under reduced pressure · Optionally the reaction product with an inert, anhydrous, organic solvent, such as diethyl ether, diluted, which precipitated The current carrier is filtered off, the solvent and ethanol are evaporated and the residue is further removed by distillation

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tion cleaned under reduced pressure or used without further cleaning · alkoxides, such as zireonethoxide, which are solid at room temperature can be obtained by recrystallization can be purified from anhydrous solvents or by distillation.

The invention is explained by the following examples. The ethanol used in the examples was ι

dried over molecular sieves. The in the following The yields given in the examples are calculated from the weight of the oxide which is obtained by A sample of known volume is taken from the solution obtained after the electrolysis and hydrolyzed, the precipitate filtered off and burns out.

example 1

The production of germanium ethoxide.

A hot, saturated solution of ammonium chloride in anhydrous ethanol was made under a nitrogen atmosphere Electrolyzed in a flask equipped with a graphite cathode, a germanium anode and a reflux condenser was equipped. A direct current of 2 A was passed through the cell, with the electrolyte being resistively heated was held at its boiling point. Towards the end of the cycle, the current dropped to 0.7A. The used Tension was 40 to 60 yoIt, and it was total supplied to the cell during the course of 32 Α hours

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The solution obtained contained 61 g of germanium ethoxide, which corresponds to a current efficiency of 78 $. The evaporation of the ethanol from an equal part of this solution and the distillation of the residue gave germanium ethoxide, boiling point 80 ° C./13 torr. The alkoxide had a GeO ₂ content of 41 Gewe # after hydrolyzing a sample and pyrolyzing the product, compared to the theoretical GeOp content of 41 »5 $. The nuclear magnetic resonance spectrum of the alkoxide corresponded to the formula Ge (OAtK ₀ The quantitative nuclear magnetic resonance analysis using benzene as an internal standard gave a hydrogen content of $ 7.4 compared to the theoretical content of $ 7.9.

Example 2

Production of tantalum oxide _{or similar}

A hot, saturated solution of ammonium chloride in anhydrous ethanol was electrolyzed under a nitrogen atmosphere in a flask equipped with a graphite cathode, a tantalum anode and a reflux condenser. A direct current between 0.4 and 0.25 ι was used during the sequence and the reversal of the polarity of the electrodes for 20 minutes. The voltage used was 50 volts and a total of 6 3/4 hours was delivered to the cell over the course of the process. The solution obtained contained 17.6 g of tantalum ethoxide, which had a current efficiency of 97%. Evaporation & ®a ethanol from a glei-rope of this solution and the distillation of the residue

-11-

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at 1 torr gave tantalum ethoxide. The alkoxide had a TapOc content of 54 wt * #, compared to the theoretical content of $ 55. The nuclear magnetic resonance spectrum of the alkoxide corresponded to the formula Ta (OAt) ₅ .

Example 3

Manufacture of titanium ethoxide.

Its hot, saturated solution of ammonium chloride in anhydrous ethanol was in a flask equipped with a graphite cathode, a titanium anode and a reflux condenser was. A direct current of 2 A at 55 to 65 YoIt was passed through, with this current after 2 hours dropped to 0.15 A at 80 volts. The electrolyte contained titanium oxide and when mixed with water provided a soft gel.

Example 4

Production of zirconium ethoxide.

A hot, saturated ammonium chloride solution in anhydrous ethanol was in a nitrogen atmosphere in a flask equipped with a graphite cathode, a zirconium anode and a reflux condenser A direct current of 0.5 A was passed through, which slowly decreased to 0.3 A. The electrolysis was continued until the ZrOg content of the electrolyte rose to about 10 wt. #. The solution obtained contained 12.9 g of ziroon ethoxide, which corresponds to a current efficiency of 82 # '

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Evaporation of ethanol from an equal part of the solution and distillation of the residue gave zirconium ethoxide, Boiling point 150 to 2OO ° C / 1 Torr as a waxy pest, the one ZrOg content of 45 »3 $ compared to the theoretical Was worth $ 45.4 *

Example 5

Manufacture of Siliciumäthoxido

A hot, saturated solution of ammonium chloride in anhydrous ethanol was electrolyzed under a nitrogen atmosphere in a flask equipped with a graphite cathode and a ferrosilicon anode. A direct current of 0.7 A at 60 volts was used, this current gradually decreasing. " After a consumption of 11 A-hours, the experiment was stopped, the current flow had dropped to 0.35 A. The solution obtained contained 12 g of silicon ethoxide, corresponding to a current efficiency of 52 $. The ethanol was evaporated from a same part of the solution and the distillation under reduced pressure gave Silieiumäthoxid, boiling point 60 to 80 ⁰ C / 25 Torr and a SiOg content of 25 wt _o $ as compared to the theoretical value for Si (OAT) . from $ 28.8.

Example 6

Manufacture of litanätho ^ id.

A hot solution of anhydrous setramethylammonium chloride (1 g) in anhydrous litkaaol (100 ml) was taken under

-13-

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electrolyzed in a nitrogen atmosphere in a flask, which consists of a graphite cathode and a titanium anode. was allowed. A direct current of 0.75 A was used for Conducted thermoset for 10 Α hours to form a solution which contained 18 g of titanium ethoxide, which has a current efficiency of $ 91 corresponds o The solution was filtered, the ethanol evaporated from the filtrate and the residue under reduced Pressure distilled to form titanium ethoxide, boiling point 136 to H2 ° C / 2 to 3 Torr as a solid. This Material had a TiOg content of $ 33 »3 by comparison to the theoretical value of 35 »$ 1 · The current efficiency of the process was $ 91> based on the TiOg content of the crude reaction product at the end of the run and $ 109 based on the weight loss of the anode.

Example 7

Manufacture of silicon ethoxide.

A hot solution of anhydrous tetramethylammonium ((

chloride (1 g) in anhydrous ethanol (100 ml) was electrolyzed under a nitrogen atmosphere in a flask equipped with a graphite cathode and a ferrosilicon anode. A direct current of 1.2 A was passed through at 70 to 72 volts, the current gradually decreasing. The process was stopped after 15 3/4 hours, the current having dropped to 0.8 A. The resulting solution was filtered, the ethanol evaporated from the filtrate and the residue under reduced pressure with formation of ethyl orthosilicate, which contained some ethyl polysilicate,

distilled. Claims: ₁ ,

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Claims (1)

- 14 patent claims: Process for the preparation of an alkoxide of an element Group IV or Va of the Periodic Table of the Elements (Mendeleev) with an atomic number from 14 "to 82 or one Transition element of the fourth period and group Ib, IIt>, Ilia, Via, VIIa or VIII of the periodic table of Elements (Mendeleev) marked by it e t that one conducts an electric current through a substantially anhydrous, liquid medium, the one Solution in a monohydric alkanol with 1 "to 4 carbon atoms per molecule of an ammonium or a quaternary ammonium salt which ionizes to a sufficient extent and is present in sufficient amount to serve as a supporting electrolyte, one containing the element Anode used in contact with the liquid medium. 2 ο Method according to claim 1, characterized in that the liquid medium is a solution with a specific conductivity of at least R »« 1 -1 3.0 χ 10 * " ^? Ohm" * cm used at the working temperature. 3. The method according to claim 2, characterized in that that the liquid medium has a specific 4. -3 -1 -1 conductivity in the range from 10 ^ to 10 ohm cm having, -15 « 209810/1962 4. The method according to any one of the preceding claims, characterized in that as an element Silicon, germanium, zircon, titanium or tantalum is used β 5. The method according to any one of the preceding claims, characterized in that the monovalent Alkanol Ethanol is 6. The method according to any one of the preceding claims, characterized in that the ammonium or quaternary ammonium salt used chloride, ammonium nitrate or a quaternary ammonium salt of the formula r R ₉ η +, in which the radicals I.
R ₁ -NR ^ R- Rpt R * and R. each is an alkyl, aryl, cycloalkyl or aralkyl radical or the radicals R ^ and R ₂ or R ^, and R, together with the nitrogen atom form a heterocyclic ring and X is a chloride, bromide , Iodide or 1/2 sulfate is o 7 · A method according to claim 6 characterized labeled in characterized in that the ammonium or quaternary ammonium salt _f ammonium chloride or tetramethylammonium chloride is used. 209810/1962 8. The method according to any one of the preceding claims, characterized in that the element used is silicon and the anode is ferrosilicon with a content of 60 to 99 wt _o # silicon. 9 ο Terfahren according to claim 1 essentially as in one of Examples 1 Ms 7 ". 10. Alkoxide of an element of group IV or Va of the period The system of elements with an ordinal number from 14 to 82 or a transition element of the fourth period and of group Ib, lib, IHa, Via, VIIa or VIII of the periodic table characterized in that it is carried out according to a method according to one of the preceding Claims is made. '(Mendeleev) 209810/1962