CZ20003731A3 - Process for selective removal of inorganic halides - Google Patents

Abstract

The method comprises a mixture comprising one or more inorganic hydrates and one or more inorganic ones halides are contacted with one containing one or more inorganic hydroxides. Inorganic hydride it may be, for example, diborane and an inorganic fluoride halide boric acid.

Description

Process for the selective removal of inorganic halides

Technical field

The present invention relates to the production and purification of diborane.

BACKGROUND OF THE INVENTION

Diborane (B2H ₆ ) is a flammable gas that is used as a p-type dopant in the semiconductor industry and also used in the production of borophosphate-silicate glass. Diborane forms a wide range of complexes including Lewis bases such as borantetrahydrofuran, borane dimethyl sulfide and a number of aminoborans. These compounds are widely used as selective reducing agents in the synthesis of drugs, organic compounds, and electroplating baths.

At room temperature, diborane slowly decomposes into higher 15 boranes, whose physical state ranges from gaseous to solid. This causes the process parameters to change and the device to malfunction. In order to reduce decomposition, diborane is sometimes supplied as a mixture with a non-reactive gas or at low temperature, such as dry ice temperature. Another way to avoid degradation problems is to use diborane formation directly at the point of use. However, the on-site synthesis of diborane was hampered by the synthesis and purification difficulties currently used.

A number of possible methods for the synthesis of diborane have been reported in the literature. The most typical and commercially used synthesis method is the reaction of sodium borohydride with boron trifluoride in ether solvents such as diglyme. Since highly flammable solvents are used in this process, it requires considerable safety

9 measures. In addition, diborane forms complexes with solvents. These complexes make it difficult to purify diborane.

A preferred dry process for the synthesis of diborane is described in US Patent 4,388,248. The method comprises reacting lithium or sodium borohydride with boron trifluoride (BF ₃ ) in the absence of a solvent. As a preferred method, this patent describes the condensation of boron trifluoride gas at liquid nitrogen temperature to sodium borohydride, then heating the resulting mixture to a reaction temperature of 0 to 50 ° C and maintaining the mixture at this reaction temperature for 4 to 12 hours. The present method 10 provides a composition comprising about 95% diborane which also contains unreacted boron trifluoride. Under similar conditions, the reaction of lithium borohydride with boron trifluoride proceeds only slowly and provides low yields.

Although the dry process provides diborane free from solvent contamination, the product obtained contains a substantial amount of unreacted boron trifluoride. To obtain high purity diborane, strenuous distillation is necessary to separate diborane from boron trifluoride. This process is slow for commercial scale production and is a batch process. Based on thermodynamic considerations, the reaction of lithium borohydride with boron trifluoride should be preferable to a comparable reaction with sodium borohydride, but the observations described in US Patent 4,388,284 show that the lithium borohydride reaction does not work well in practice.

SUMMARY OF THE INVENTION

The present invention, in one embodiment, provides methods of treating compositions comprising diborane and boron trihalides such as boron trifluoride by contacting the composition with a reagent comprising one or more inorganic hydroxides.

This aspect of the invention is based on the discovery that inorganic 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 ··. 9 9 9 9

9999 9999 999 ········

- 3 hydroxides selectively capture boron trihalides and especially BF3 from diborane-containing gas mixtures. The reagent may comprise one or more alkali metal hydroxides such as sodium, potassium or lithium hydroxides; alkaline earth metal hydroxides such as beryllium, calcium, strontium and barium hydroxide; ammonium hydroxide; and transition metal hydroxides. Mixtures of these materials may be used. Desirably, the reagent comprises a substantial amount of inorganic hydroxide, i.e. greater than 10%, and preferably greater than 20%, of the hydroxides. The reagent is preferably predominantly composed of hydroxide or hydroxides, i.e. the reagent contains more than 50 mol% of hydroxides. Most preferably, the reagent consists essentially of hydroxide or hydroxides. The reagent is typically present in a solid form such as a powder, pellet, granule, or coating on an inert carrier such as alumina or silica. The reagent may be pretreated by placing it at an elevated temperature before use, such as by heating under an inert atmosphere before use.

The temperature of the contacting step is preferably room temperature (about 20 ° C) or less, and more preferably about 0 ° C or less.

Even more preferred are temperatures below about -20 ° C, suitably below about -40 ° C. The use of such low temperatures minimizes diborane decomposition in the process. Most preferably, the diborane-containing composition is in gaseous contact with the reagent. Therefore, the temperature in the contacting step is suitably higher than the boiling point of diborane at the pressure used. In other words, the pressure prevailing in the contacting step is lower than the equilibrium vapor pressure of diborane at the temperature used for the contacting step. The boiling point of diborane is at atmospheric pressure of about -92 ° C, and therefore the temperature of the contacting step is suitably higher than about -92 ° C when this contacting step is carried out at about atmospheric pressure. Dry ice temperature (about -80 ° C) is particularly preferred.

· · ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ··· ··· «··· ·« ·· ·· ··

The contact time between the diborane-containing composition and the reagent may be from a few seconds to several hours, although very short contact times of several seconds are preferred. The contacting step may be carried out batchwise, or preferably continuously, by conducting the mixture continuously through a vessel containing the reagent. The rate of flow through the vessel and the dimensions of the vessel and the amount of reaction mixture can be selected to achieve the desired contact time. Suitably, the cleaning, and in particular the contacting step, is carried out at the point where the purified diborane is to be used and if the diborane is cleaned approximately 4 hours or less before use. Most preferably, diborane is purified immediately prior to use.

Although this embodiment of the invention has been summarized above in connection with the purification of diborane, the process can also be used to purify other inorganic hydrides and remove inorganic halides other than boron trihalides such as BF3. Thus, the method is useful for removing inorganic halides from inorganic hydrides selected from diborane, silane (SiH ₄ ), german (GeH ₄ ), phosphine (PH ₃ ), arsine (AsH ₃ ), stibine (SbH ₃ ), and mixtures thereof. Inorganic halides are removed preferably from the group consisting of BF _3, SiF _4, GEF _4, PF _3, PF _5, AsF _3, AsF _5, SbF _3, SbF ₅ and mixtures thereof.

A further embodiment of the invention includes the finding that contact of the diborane-containing composition with the hydroxide-containing reagent will also serve to remove carbon dioxide if carbon dioxide is present in the composition. Thus, the methods of this embodiment of the invention include the steps of bringing the diborane-containing or other inorganic hydride-containing composition as mentioned above and carbon dioxide into contact with the hydroxide-containing composition. The process conditions may, as mentioned above, be related to the removal of halides. If the gas mixture contains both halides and carbon dioxide, both substances can be removed in a single contacting step.

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Yet another embodiment of the invention provides methods for synthesizing diborane which comprise reacting a borohydride reagent including potassium borohydride (KBH ₄ ) with boron trihalide, most preferably BF _3, to form a reaction product. The reaction is suitably carried out at a reaction temperature of from about -130 ° C to about 20 ° C. The reagent (reactant) suitably comprises at least 20% potassium borohydride, preferably consists exclusively of potassium borohydride, or comprises potassium borohydride together with sodium borohydride (NaBH ₄ ). The reaction step is conveniently carried out in the absence of a solvent and is therefore referred to herein as a " dry " process. The reaction is suitably carried out by continuously conducting the boron trihalide in gaseous form with a vessel containing the borohydride reagent (reactant) in solid form. The reaction can also be carried out batchwise, such as by condensing the boron halide on the reagent in the vessel and then heating the reaction vessel, reagent and boron halide. This embodiment of the invention includes the finding that a higher conversion of boron trifluoride to diborane is achieved by its reaction with potassium borohydride than with lithium or sodium borohydride. The reaction with potassium borohydride proceeds particularly well at preferred temperatures from about -130 ° C to about 20 ° C. Most preferably, the reaction conditions are selected such that liquid BF ₃ is present in contact with the borohydride reagent during at least a portion of the reaction. Thus, it is preferred that BF ₃ condenses on the borohydride reagent.

Still further embodiments of the invention provide apparatus for carrying out the methods described above. Thus, one embodiment of the invention provides a cleaning device for selectively removing inorganic halides such as BF ₃ and carbon dioxide from diborane-containing or other inorganic hydride-containing compositions, and also provides a system for forming diborane using such a cleaning device. Another embodiment of the invention provides a generator for producing diborane using the reaction with potassium borohydride described above, which

- 6 · · 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 The cleaning device described above may also be included. The apparatus according to these embodiments of the invention may be installed at the point of use and suitably attached directly to the diborane utilizing device for continuous or batch transfer of the diborane produced or cleaned in the diborane producing device to the diborane utilizing device.

BRIEF DESCRIPTION OF THE DRAWINGS

Giant. 1 is a diagram of an apparatus according to an embodiment of the invention.

FIG. 2b is an infrared spectrum of a mixture comprising diborane and BF ₃ .

Giant. 2a is an infrared spectrum of the composition of FIG. 2b after purification according to one embodiment of the invention.

Giant. 3b is an infrared spectrum of another mixture containing diborane and BF ₃ .

Giant. 3a is an infrared spectrum of the composition of FIG. 3b after purification according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Description of the methods of carrying out the invention

The device according to one embodiment of the present invention comprises a vacuum-tight closed stainless steel system. The gas cylinder S provided with a pressure reducing valve V0 is connected to the reaction cylinder R containing the borohydride reagent in solid form. The reaction cylinder R has an inlet and an outlet valve V1 and an outlet valve V1 at the inlet and outlet. The reaction cylinder is provided with a jacket to allow cooling and low temperature reactions to proceed. The outlet valve _V2 cylinder R is connected to a T-piece, one branch of the T-piece T is connected ♦ _± 4

- 7 for a cleaning cylinder or bubbler P provided with an inlet valve V3 and an outlet valve V3. The cleaning roller contains the solid reagent of the hydroxide reagent. The purge cylinder outlet valve P is connected via another T-piece T ₂ and a valve V5 to the gas collection device F. The device F may be a collection cylinder for storing diborane or may be part of a device for performing a diboran-consuming process such as a storage system. thin film at a semiconductor or other reactor.

The bypass valve V6 and the bypass pipe B connect the T-piece Τχ ίο to another T-piece T3, which is connected to the T-piece T ₂ . The remaining branch T's T3 is connected via a further valve V ₂ to a vacuum manifold M equipped with devices for measuring pressure and vacuum. This manifold is provided with a waste connection W coupled to a pump and a scrubber. The splitter is also connected to the cell of the infrared spectrophotometer [and the piping is provided with additional valves Vg, Vg and V10. Flow meters and / or control elements (not shown) may be provided at source S, valve V3, and other locations as required to monitor the process to obtain the desired generator capacity. The bypass line and the spectrophotometer are used for evaluation purposes in the examples below; these elements and the associated valves can be omitted in production systems.

In operation, the reaction cylinder R is charged with the borohydride reagent as described above and the cleaning cylinder P with the hydroxide-containing reagent as described above.

The complete system is evacuated through the drain line W and the connected pump. Once the desired reaction temperature in cylinder R and the desired contact temperature in the purification cylinder P are maintained, the gas cylinder S and the pressure reducing valve Vo are opened to allow boron trifluoride to enter the reaction cylinder R via the valve V1. BF ₃ is reacted in cylinder R with borohydride to give a mixture containing diborane and BF ₃ . The outlet valve V ₂ and the purifier valves V3 and V4 remain open so that the mixture from the cylinder R passes through the purifier P to form a purified diborane.

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8 which passes further into the collecting cylinder or is used in the apparatus F. A certain amount of purified diborane is diverted by the valve Vy to the distributor M and the infrared spectrophotometer L To monitor the composition of the reactor mixture R, valves V ₃ , V4 and V5 are closed, / θ is open to divert the mixture around cleaner P.

The use of potassium borohydride reagent in reactor R optimizes the conversion of BF ₃ to diborane at a reaction temperature of from about -120 to about 30 ° C. If the reaction is carried out at a higher temperature, a higher concentration of boron trifluoride in the diborane / boron trifluoride mixture obtained in the reaction is observed. Similarly, the boron trifluoride content of the mixture is higher when sodium borohydride is used instead of potassium borohydride. Since the hydroxide in purifier P effectively takes up boron trifluoride from the mixture, sodium or lithium borohydride can also be used in reactor R while maintaining a highly pure diborane at the outlet of the purifier. However, this is less advantageous because the capacity of the cleaner is reduced. Optimum uptake selectivity using lithium, sodium or potassium hydroxide is achieved in the scrubber. The most preferred hydroxide for use in the cleaner is lithium hydroxide. As mentioned above, P is suitably used at a temperature below room temperature, more preferably at dry ice temperature.

Illustrative examples

Some embodiments of the invention will be illustrated in the following examples:

Example 1 g of potassium borohydride was introduced in a helium atmosphere inside a gloved bellows into a stainless steel cylindrical reactor R (195 cm ³ volume) fitted with flanges at both ends. The reactor was closed by mounting the flanges with valves. 4 4444 4 4444 4 4444 4 ·· ··· ···· ·· ··

- 9 closed. This composite reactor was placed in an empty, jacketed, cylindrical vessel. Stainless steel bubbler (972 cm ³ ) with submerged tube and welded top with inlet and outlet valves equipped with VCR couplings was used as P purifier.

The cleaner was more than half filled with potassium hydroxide pellets through the fill port. The cleaner was filled inside the glove bellows with helium flow. The filling opening was closed with a 12.7 mm diameter VCR valve. The reactor and cleaner were connected as shown in Figure 1. All parts of the assembly 10 including the reactor and cleaner were evacuated. Cleaner P was warmed slightly during evacuation to dry the potassium hydroxide. The jacketed vessel around the reactor was filled with dry ice. The cleaner was cooled using a dry ice-filled Dewar vessel into which the cleaner was placed.

Boron trifluoride was fed to the reactor R from a gas cylinder S with a pressure reducing valve set to maintain an inlet pressure of 1100 torr (146.7 kPa) to the reactor. The reactor inlet valve V2 was closed and the outlet valve V2 was opened to allow a sample of the reacted mixture to pass through the purifier P. A sample passing through the purifier P at an outlet pressure of 24 torr (3.20 kPa) was collected in a pre-evacuated IR cell. on Buck Scientific IR spectrophotometer. Giant. 2a shows an infrared spectrum of a sample; shows pure diborane. The IR cell was reconnected to the manifold and evacuated.

Both V3 and V4 valves on the cleaner were closed. Another sample of the reactor mixture at 19 torr (2.53 kPa) was collected into the IR cell by opening the reactor outlet valve V2 and the bypass valve Vq into the bypass line B. The IR spectrum of the sample is shown in Figure 2b. This spectrum shows diborane and also shows the absorption at 1450 cm ^-1 characteristic of BF ₃ . These results show that the cleaner successfully removed BF3 from the mixture, leaving diborane substantially intact.

• · ··

- 10 Example 2

The procedure of Example 1 was substantially repeated except that the potassium hydroxide purifier P was maintained at room temperature. The sample passed through the purifier was collected at 53 torr and an IR scaffold was performed. The spectrum shows only a small amount of diborane and no BF ₃ . Although another sample was collected through bypass line B at 14 torr, i.e. passed outside the purifier P, it contained diborane and some boron trifluoride. The spectrum of this sample was similar to Figure 2b. These results show that at w room temperature the boron trifluoride scrubber removes completely, but some decomposition of diborane occurs.

Example 3

The process described in Example 1 was repeated essentially with the exception that the cleaner was filled with soda lime (a mixture of sodium hydroxide, calcium oxide and calcium hydroxide). The reactor and the scrubber were cooled to dry ice temperature. A sample from the reactor passing through the scrubber was collected at 51 torr (6,80 kPa) and another sample not passing through the scrubber was collected at 19 torr (2.53 kPa). Comparison

IR scans for these samples confirmed that the scavenger taken up boron trifluoride from the diborane / boron trifluoride mixture. However, in the case of soda lime, some decomposition of diborane to non-condensable hydrogen was observed.

Comparative Example 4

The reactor used in Example 1 was cleaned, dried and then charged with 62.4 g of sodium borohydride and connected to the assembly of Fig. 1 and a vacuum distributor. Purifier P used in Example 1 was charged with 247 g of lithium hydroxide. Purifier P used in Example 1 was heated to 60 ° C, repeatedly flushed with helium and evacuated. Reactor jacket R a

3o Dewar's purifier P was filled with dry ice and left

Cool to dry ice. Boron trifluoride was charged to the reactor at 760 torr. The inlet valve V _{± of the} reactor was closed and the outlet valve V2 was opened to the bypass line B and manifold. The sample was collected at 50 torr to a pre-evacuated IR cell. Giant. 3b shows the IR scaffold of the sample showing diborane and a substantially higher amount of unreacted boron trifluoride than found in Example 1 in the presence of potassium borohydride.

Example 5

The IR cell was evacuated again and a sample was taken from the reactor of Comparative Example 4 by opening it through a purifier P at a pressure of 22.4 torr. The IR scape obtained shown in Figure 3a shows only diborane in the absence of any boron trifluoride.

^{15 Dec}

Comparative example 6

The procedure of Comparative Example 4 was essentially repeated except that the reactor R was maintained at room temperature. Boron trifluoride was fed into the reactor at 800 torr and a closed inlet valve. A 50 torr sample was taken into an IR cell outside the purifier. The IR spectrum showed predominantly boron trifluoride, meaning that little or no diborane was formed.

Example 7

The procedure of Comparative Example 6 was repeated, but using a reactor containing potassium borohydride. The IR spectrum shows a significantly higher diborane content than that obtained in Comparative Example 6.

Example 8

In this arrangement, the conversion efficiency and the yield of diborane from the reaction of BF 3 and potassium borohydride were measured. 7.75 g (0.1437 mol) of potassium borohydride was placed in a 75 ml stainless steel sample cylinder inside a helium-coated glove. The cylinder was sealed with a diaphragm valve and connected to a vacuum distributor. Boron trifluoride, which was condensed in six different experiments, was transferred to the cylinder. The cylinder was filled with liquid nitrogen. The amount of boron trifluoride converted in these experiments varied from 0.01 to 0.077 mol. In each case, boron trifluoride was transferred to a sample cylinder, weighed and stored at 0 ° C in a refrigerator. The reaction mixture present in the cylinder was analyzed at 30 torr each using an IR scan. After analysis, the product was transferred and the sample cylinder was weighed and refilled with boron trifluoride. In each of these six experiments, the full yield of diborane in the reaction was observed by IR scan. A total of 0.19 moles of boron trifluoride was completely reacted to diborane. In the next experiment, 0.01 mol of boron trifluoride was added and left in the refrigerator for one week, the product mainly containing boron trifluoride, indicating the depletion of potassium borohydride. The experiment showed that 4 moles of boron trifluoride completely reacted with 3 moles of potassium borohydride to obtain diborane.

Example 9

In this experiment, 21.1 g of potassium borohydride was transferred to a 175 ml stainless steel cylinder (reactor cylinder), which was then sealed with a stainless steel membrane valve. The cylinder was evacuated and weighed and mounted back on the vacuum distributor. Boron trifluoride was condensed in the cylinder at an amount of liquid nitrogen

8.2 g (0.1209 mol) and the cylinder was placed in a refrigerator at -40 ° C

for one week. The cylinder was removed from the refrigerator and mounted on the inlet side of the lithium hydroxide cleaner. The outlet side of the vacuum divider was connected to a pre-evacuated 175 ml stainless steel cylinder (receiver). The cleaner was cooled with dry ice and the receiver was cooled with liquid nitrogen. The steam (diborane) from the above-described cylinder was transferred through a cleaner and into a cooled collecting cylinder. A total of 1.6 g of sample was transferred as determined by weight loss in the reactor cylinder. A weight gain in the collection cylinder of 1.6 g was also observed. Sample analysis showed pure diborane with a CO ₂ impurity content of less than 10 ppm. Thus, the experiment shows the efficiency of the scrubber in removing the carbon dioxide impurity.

The cleaner in the example would also effectively remove any higher boranes.

Within the scope of the invention as defined in the claims, both the foregoing and other possible variations and combinations of the above-described parameters may be utilized, and the foregoing description of the preferred embodiments should be considered merely illustrative and not limiting of the invention defined in the claims.

Industrial applicability

The present invention can be used in the synthesis and purification of hydrides, for example, in semiconductor manufacturing, glass manufacturing or other syntheses of industrial chemicals.

Represented by:

Claims (9)

PATENT CLAIMS A process for the selective removal of inorganic halides from a mixture comprising one or more inorganic hydrides and one or more inorganic halides, characterized in that the mixture is contacted with a composition comprising one or more inorganic hydroxides. The process according to claim 1, wherein the one or more inorganic hydrides are selected from the group of diborane, silane, german, phosphine, arsine, stibine and mixtures thereof. 15 Dec The process according to claim 2, wherein the one or more inorganic halides consists essentially of one or more inorganic fluorides selected from the group of BF ₃ , SiF ₄ , GeF ₄ , PF ₃ , PF ₅ , AsF ₃ , AsF ₅ , SbF ₃ , SbF ₅ and mixtures thereof. A process according to claim 3, wherein the inorganic hydride consists essentially of diborane and the one or more inorganic fluorides consists essentially of BF ₃ . 5. The process of claim 1 wherein said composition consists essentially of said one or more hydroxides. • · - 15 6. The process of claim 1 wherein said composition comprises one or more alkali metal hydroxides. The method of claim 6, wherein the composition comprises lithium hydroxide. 8. The method of claim 6, wherein the composition comprises sodium hydroxide. 9. The method of claim 6, characterized by wherein the composition comprises potassium hydroxide. 15 Dec 10. The method of claim 1, characterized by that the composition comprises one or more metal hydroxides alkaline earths. 11. The method of claim 1, characterized by 20 May wherein the composition comprises ammonium hydroxide. 12. The method of claim 1, characterized by that the composition comprises one or more hydroxides transition metals. 25 13. The method of claim 4, characterized by wherein said contacting step is carried out at a temperature below about 0 ° C. - 16 e e β ♦ * e * * * * * * * The method of claim 13, wherein a temperature of between about -90 ° C and -40 ° C is used. The method of claim 14, wherein a temperature of about -80 ° C is used. The method of any one of claims 1 to 15, further comprising the step of using purified diborane at the point of consumption, said contacting step being performed at the point of consumption. The method of claim 16, wherein the diborane is purified and used within 4 hours after purification. The method of claim 17, wherein the diborane is used immediately after purification. A method according to any one of claims 1 to 15, 20, characterized in that said contacting step is carried out by passing said mixture through said composition, said composition being in the solid phase. A method according to claim 19, characterized in that 25 wherein said contacting step is carried out at a pressure below the equilibrium vapor pressure of diborane at a temperature prevailing in the contacting step. * · 9 9 9 9 9 9 9 • 9 9 9 9 9 9 9 9 9 9 · 9 9 9 · · · 9999 9999 999 9999 99 99 21. The method of claim 19, wherein said contacting step is performed by passing a continuous flow of said mixture through a vessel containing said composition. 22. The method of claim 19 wherein said composition is in the form of a powder, pellet or granule. The method of any one of claims 1 to 15, wherein said composition is in the form of a coating on a substantially inert carrier. 24. The method of any one of claims 1 to 15, further comprising the step of pre-treating the reagent with heat, wherein the reagent is located in an inert atmosphere. The method of any one of claims 1 to 15, wherein the mixture comprises carbon dioxide and the reagent removes carbon dioxide from the mixture at the contacting step. 26. A method for removing carbon dioxide from a mixture of carbon dioxide and an inorganic hydride, characterized in that it comprises a step _25, wherein said mixture is brought into contact with a reagent composition comprising one or more inorganic hydroxides. - 18 • · 4 · 4 4 * 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 * 4 4 4 4 4 4 4 4 4444 27. The process of claim 26 wherein said inorganic hydride consists essentially of diborane. 28. A process for producing diborane comprising reacting a potassium borohydride-containing reactant with boron trihalide to form a reaction product. 10 29. Method according to Claim 28 characterized by that is stated reactant se basically composed borohydride potassium. 30. Method according to Claim 28 characterized by ₁₅ wherein said reactant comprises potassium borohydride together with sodium borohydride. Process according to any one of claims 28 to 30, characterized in that said reaction is carried out The step 20 is carried out in the absence of a solvent at a reaction temperature of from about -130 ° C to about 20 ° C. Process according to one of Claims 28 to 30, characterized in that the boron trihalide is 25 boron trifluoride. 33. The process of claim 32 wherein the boron trifluoride is present in contact with said reactant during at least a portion of the reaction in the liquid state. - 19 • · ·· The method of any one of claims 28 to 30, further comprising the step of removing unreacted boron trihalide from the reaction product with a reagent comprising one or more inorganic hydroxides to obtain purified diborane. 35. The method of claim 34, further comprising the step of utilizing said purified diborane at the point of consumption, wherein the reaction and removal steps are performed at that point of consumption. 36. The process of claim 35 wherein said reaction and removal steps are carried out 15 in parallel to the recovery step so that diborane is purified and used within approximately 4 hours after its formation. 37. The process of claim 36 wherein the diborane is purified immediately after formation 20 and used immediately after cleaning. 38. A method for producing diborane, comprising reacting an alkali metal borohydride with boron trihalide and removing unreacted. 25, by contacting the reaction product with a reagent comprising one or more inorganic hydroxides to obtain purified diborane. 39. A diborane synthesis apparatus comprising (a) a boron trihalide source; and (b) a reaction vessel containing the reagent comprising 5 of potassium borohydride connected to said source. 40. The apparatus of claim 39, wherein the reagent consists essentially of potassium borohydride. 41. The apparatus of claim 39, wherein the reagent comprises potassium borohydride together with sodium borohydride. The apparatus of any one of claims 39 to 41, further comprising a cooling apparatus adapted to maintain the reaction vessel at a temperature between -130 ° C and 20 ° C. 20. The apparatus of claim 39, further comprising a cleaning vessel comprising a composition comprising one or more inorganic hydroxides, wherein the cleaning vessel is attached to the reaction vessel such that said reaction products from the reaction vessel can 25 to the cleaning vessel. An apparatus for cleaning a composition comprising an inorganic hydride and one or more inorganic halides, characterized in that it comprises a cleaning agent. 99 a container comprising a composition comprising one or more inorganic hydroxides and a source of said mixture connected to said cleaning container. 45. The apparatus of claim 43 or 44, further comprising a cooling device adapted to cool the cleaning vessel. 46. The method according to claim 2, characterized in, that the one or more inorganic halides comprises one or more inorganic fluorides selected from the group consisting of BF 3, SiF _4, GEF _4, PF _3, PFS, AsF _3, AsF _5, SbF _3, SbF ₅ and mixtures thereof. The method of claim 46, wherein the inorganic hydride comprises diborane and the one or more inorganic fluorides comprises BF ₃ . 48. The method of claim 47, wherein said contacting step is performed at a temperature below 0 ° C. The method of claim 48, wherein said temperature is between -92 ° C and -40 ° C. 50. The method of claim 48, wherein said temperature is about -80 ° C. 9. 9 51. The method of claim 47, further comprising the step of using the purified diborane at the point of consumption, said contacting step being performed at that point of consumption. 52. The method of claim 51, wherein said diborane is purified and used within 4 hours of purification. 53. The method of claim 51 wherein said diborane is fed directly to a plant in which it is used after cleaning. 54. The method of claim 53, 15 that this conversion is carried out continuously. 55. The method of claim 53 wherein said conversion is performed in a single dose. 6. The method according to claim 16, wherein the diborane is, after cleaning, transferred directly to the apparatus for its use. 57. The method of claim 56, 25 that this conversion is carried out continuously. 58. The method of claim 56, wherein said conversion is performed in a single dose. - 23 99 99 99 99 99 99 • 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 · · · · 9999 9999 999 9999 9 · 8 · 59. The method of claim 5, wherein said composition consists essentially of one or more alkali metal hydroxides. 60. The method of claim 59, wherein said inorganic hydride consists essentially of diborane and said one or more inorganic fluorides consists essentially of BF3. 61. The method of claim 60, wherein the contacting step is conducted at a temperature below about 0 ° C. 62. The method of claim 60 wherein said temperature is between about -92 ° C and -40 ° C. 63. The process of claim 60 wherein said mixture consists essentially of lithium hydroxide. 64. The method of claim 63, wherein said contacting step is performed at a temperature of less than about 0 ° C. 65. The method of claim 63 wherein said temperature is between about -92 ° C and -40 ° C.