Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/04—Hydrides of silicon
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/04—Hydrides of silicon
  • C01B33/046—Purification
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

• the present invention relates to a process for the purification of low molecular weight hydridosilanes or their mixtures.
• Hydridosilanes or their mixtures in particular low molecular weight hydridosilanes or their mixtures, are discussed in the literature as possible starting materials for the production of silicon layers. Hydridosilanes are compounds which contain only silicon and hydrogen atoms and which have a linear, branched or (optionally bi- / poly-) cyclic structure with Si-H bonds.
• EP 1 087 428 A1 describes e.g. Process for producing silicon films in which hydridosilanes having at least three silicon atoms are used.
• EP 1 284 306 A2 describes inter alia. Mixtures comprising a hydridosilane compound having at least three silicon atoms and at least one hydridosilane compound selected from cyclopentasilane, cyclohexasilane and silylcyclopentasilane, which can also be used for the production of silicon films.
• low molecular weight hydridosilanes are understood as meaning hydridosilanes having a maximum of 20 silicon atoms.
• Hydridosilanes can e.g. by dehalogenation and polycondensation of halosilanes with alkali metals (GB 2 077 710 A).
• hydridosilanes are based on a dehydropolymerization reaction of hydridosilanes, in which thermal (US Pat. No. 6,027,705 A) or by using catalysts such as hydridic cyclopentadienyl complexes of scandium, yttrium or rare earths (US Pat. No. 4,965,386 A, US Pat. No. 5,252,766 A) and hydridosilane adducts are formed from transition metals or their complexes (JP 02-184513 A) from the hydridosilane starting materials with formal H 2 cleavage.
• thermal US Pat. No. 6,027,705 A
• catalysts such as hydridic cyclopentadienyl complexes of scandium, yttrium or rare earths
• hydridosilane adducts are formed from transition metals or their complexes (JP 02-184513 A) from the hydridosilane starting materials with formal H 2 cleavage
• the synthesis of linear hydridosilanes of the general formula H- (SiH 2 ) n -H (where n> 2) can be carried out by a process in which one or more hydridosilanes, hydrogen and one or more transition metal compounds comprising elements of the 8th, 9th or Group 10 of the Periodic Table (Fe, Co, Ni, Ru, Rh, Pd, Re, Os, Ir, Pt) and the lanthanides (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho , He, Tm, Yb, Lu), reacted at a pressure of more than 5 bar absolute reaction, subsequently relaxed and the hydridosilanes formed are separated from the resulting reaction mixture (not yet disclosed EP 08158401.3).
• the separation can be carried out by the methods known to those skilled in the art, in particular via distillation or via the use of adsorptive processes.
• the catalyst is generally prepared under protective gas atmosphere in situ in a suitable dried solvent (eg, toluene, reflux over Na, benzophenone) and transferred to a reactor while maintaining a protective gas atmosphere.
• a suitable dried solvent eg, toluene, reflux over Na, benzophenone
• the mixture is then reacted.
• the desired hydridosilanes are then formed.
• the resulting mixture consisting of the hydridosilanes formed, solvents and optionally unreacted educts can after removal of the homogeneous catalyst and relatively high molecular weight secondary components (ie those having more than 20 Si atoms, in particular corresponding polysilins and polysilanes) for use in semiconductor or photovoltaic field are used, since at a given purity of the starting materials no contamination of interfering secondary components are to be expected.
• relatively high molecular weight secondary components ie those having more than 20 Si atoms, in particular corresponding polysilins and polysilanes
• hydridosilanes produced by a thermal dehydropolymerization reaction or by dehalogenation and polycondensation of halosilanes with alkali metals to produce relatively high molecular weight by-products, ie. those having more than 20 Si atoms, in particular corresponding hydridosilanes and polysilins, can be separated from the reaction mixture, since they have the disadvantage, especially at high molecular weights, of leading to inhomogeneities in the production of silicon layers.
• adsorptive purification methods such as separation processes based on zeolites, have the disadvantage that they require a complex purification step of the adsorbent.
• the object of the present invention was a process for the separation of impurities selected from the group of compounds with more than 20 Si atoms, in particular the corresponding hydridosilanes and polysilines, and / or the group of ( to provide at least one metal of the transition metal series or lanthanides and at least one ligand) homogeneous-catalyst systems of low molecular weight hydridosilanes, which does not have the disadvantages of the prior art.
• the present object is achieved by a process for the purification of low molecular weight hydridosilane solutions in which a solution to be purified comprising at least one low molecular weight hydridosilane, at least one solvent and at least one impurity selected from the group of compounds having at least 20 Si.
• Atoms (in particular high molecular weight hydridosilanes and polysilins) and / or the group of homogeneous catalyst systems are subjected to a cross-flow membrane process with at least one membrane separation step using a permeation membrane.
• a pressure-driven membrane process in which the solution to be purified at a pressure p ⁇ is brought into contact with one side of a permeation membrane, and on the other side of the permeation membrane on the the pressure p M prevails, which is smaller than the pressure p ⁇ , a purified solution is removed, ie a solution containing a lower concentration of at least one contaminant compared to the solution to be purified.
• the purified solution after the first purification step is brought into contact with the permeation membrane, and taken on the oth er n S ei te beieinem D ru ckp M p ⁇ at a pressure again.
• the number of h to be added to further purification steps increases accordingly.
• ultra or nanofiltration membranes and reverse osmosis membranes can be used as permeation membranes in such a membrane process.
• These usable membrane types comprise either porous permeable polymer or ceramic layers or permeable polymer or ceramic layers on a porous substructure, whereby reverse osmosis membranes are distinguished by a separation limit of ⁇ 250 g / mol, nanofiltration membranes. Distinguish membranes by a separation limit of 250 - 1000 g / mol and ultrafiltration membranes by a separation limit of 1,000 - 100,000 g / mol.
• organophilic nanofiltration membranes as they are known from the workup of organic solvents, because with this method dissolved impurities in a molecular weight range of 250 to 1000 g / mol can be removed particularly efficiently.
• the inventive method also offers the advantage that it is structurally simple in manufacturing processes for low molecular weight hydridosilanes, in particular Manufacturing method based on the metal I catalyzed dehydropolymerization can be integrated. Particularly in the case of integration into a metal-catalyzed dehydropolymerization setup, the catalyst-containing retentate stream from a downstream membrane separation step may be recycled to the reactor for recycling while the purified product is being removed.
• the purification process according to the invention further offers the surprising advantage that contaminated low molecular weight hydridosilane solutions containing both impurities with more than 20 Si atoms and impurities based on homogeneous catalysts - especially in the case of reaction product solutions of a synthesis of low molecular weight hydridosilanes over metal I catalyzed Dehydropolymerization process - can be removed through a single purification process.
• the impurity or the impurities can be removed particularly well if at least two membrane separation steps, preferably at least three membrane separation steps are carried out.
• Hydridosilanes or polysilines having molecular weights above 600 g / mol, preferably greater than 1000 g / mol, are particularly easily removable via the process according to the invention. It is observed that the larger the molar mass ratio of impurity and product to be purified, the better can be removed impurities.
• impurities selected from the group of homogeneous catalyst systems which contain a metal selected from the 4th, 5th, 6th, 7th, 8th, 9th or 10th group of the group can be removed by the process according to the invention Periodic table, particularly preferably a metal selected from Fe, Co, Ni, Ru, Rh, Pd, Re, Os, Ir, Pt, W and Mo.
• Homogeneous catalyst systems ie a ligand selected from halogen, hydrogen, alkyl, aryl, alkylsilane, arylsilane, olefin, alkylcarboxyl, arylcarboxyl, acetylacetonatoalkoxyl, aryloxy, alkylthio, arylthio, substituted are particularly well removable via the purification process according to the invention or unsubstituted cyclopentadienyl, cyclooctadiene, cyanoalkane, aromatic cyano compounds, CN, CO, NO, alkylamine, arylamine, pyridine, bipyridine, (hetero) -alkylphosphine, (hetero) arylphosphine, (hetero) alkylarylphosphine, (hetero) alkyl phosphite, (Hetero) aryl phosphite, alkylsti
• the inventive method is suitable for the purification of solutions based on a variety of solvents.
• the best compatibility with the conventionally used membranes results when the at least one solvent of the solution to be purified is selected from the group of aprotic nonpolar solvents, ie the alkanes, substituted alkanes, alkenes, alkynes, aromatics without or with aliphatic or aromatic substituents, halogenated hydrocarbons, tetramethylsilane, or the group of aprotic polar solvents, ie the ethers, aromatic ethers, substituted ethers, esters or acid anhydrides, ketones, tertiary amines, nitromethane, DMF (dimethylformamide) DMSO (dimethylsulfoxide) or propylene carbonate is.
• the process according to the invention can particularly preferably be carried out with solutions of toluene, n-hexane or tetradecane.
• Membranes which can preferably be used for the cross-flow membrane process are those which have as a permeable layer a polymer layer of polydimethylsiloxane (PDMS) or other polysiloxanes, polyimide (PI), polyamideimide (PAI), acrylonitrile / glycidyl methacrylate (PANGMA), polyamide ( PA), polyethersulfone (PES), polysulfone (PSU), cellulose acetate (CA), polyetherimide (PEI), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyetheretherketone (PEEK), polycarbonate (PC), polybenzimidazole (PBI), polyacrylates, Polyetheramide (PIA), polyethylene oxide amide (PEBAX), polyisobutylene (PIB), polyphenylene oxide (PPO), polyvinyl alcohol (PVA), sulfonated polyetheretherketones (SPEEK) or cellulose. Further advantageously us
• Preferred membranes are those based on PET / PAN / PDMS, which are commercially available under the designation oNF2 from GMT, Rheinfelden, or PET / PAN / PI, which are commercially available under the name Starmem, from Grace Davison, Littleton, CO, US.
• the membranes are preferably in the form of membrane modules, in particular in the form of open-channel pillow module systems, in which the membranes are thermally welded to membrane pockets, or in the form of coil modules in which the membrane bonds to membrane covers Feed-s pa ce rn are wound around a Permeatsammelrohr used.
• membranes are those which are permeable to molecules up to a molecular weight of 400 g / mol.
• ne Mem is brantren nsch step of cross-flow membrane process to achieve a particularly good purification, preferably at a temperature from 10 to 120 0 C, particularly preferably at 15 - 45 0 C performed.
• the at least one membrane separation step of the cross-flow membrane process is further preferably carried out at an excess flow rate at the membrane of 0.1 to 15 m / s in order to achieve equally good and rapid purification.
• the purification process according to the invention is particularly well suited for the purification of low molecular weight hydridosilane solutions which can be prepared by a process for the synthesis of linear hydridosilanes of the general formula H- (SiH 2 ) n -H (where n> 2) in which one or more hydridosilanes, hydrogen and one or more transition metal compounds comprising elements of the 8th, 9th or 10th group of the Periodic Table (Fe, Co, Ni, Ru, Rh, Pd, Re, Os, Ir, Pt) and the lanthanides (Ce, Pr, Nd , Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) are reacted at a pressure of more than 5 bar absolute.
• H- (SiH 2 ) n -H where n> 2
• the purification process according to the invention can be advantageously integrated into production processes for low molecular weight hydridosilanes, in particular production processes based on metal-catalyzed dehydropolymerization. Especially in case of Integration in production processes via metal-catalyzed dehydropolymerization can advantageously be fed back from a reactor downstream membrane separation step, catalyst-containing retentate to the reactor for recycling, while the purified product can be removed in the permeate stream.
• FIG. 1 shows a schematic illustration of an experimental setup for an embodiment of the method according to the invention.
• the reactants 1 and a recycle stream 6 are fed to the dehydrogenation reactor R in which the polysilane synthesis takes place.
• the reactor may be a stirred tank or a tubular reactor.
• the reaction mixture 2 is passed directly to the membrane M.
• the retentate stream 3 obtained at the membrane is returned to the reaction.
• the permeate stream 4 obtained on the membrane M is passed into a thermal separation device D, for example into a thin-film evaporator.
• a separation into polysilane product which leaves the thermal separation device as stream 5, and a stream 6, the high boilers, solvents and not separated in the membrane separation complex catalyst, solvent and / or free ligand and is recycled to the reactor R.
• Polymer membranes from PET / PAN / PDMS and PET / PAN / PI are inserted in after completion of a dehydropolymerization obtained from monosilane, not further purified reaction systems consisting of 1) a mixture of lower hydridosilanes having two to ten silicon atoms, 2) den the dehydropolymerization higher molecular weight impurities comprising polysilins and hydridosilanes having more than 20 Si atoms, 3) the solvent toluene and 4) the catalyst system consisting of i) the metal precursor Nickelacetylacetetonat or rhodium acetate and ii) a phosphine or phosphite ligands
• 0.1 mmol of nickel acetylacetonate and a 2.1-fold excess of ( ⁇ ) -2,2'-bis (diphenylphosphino) -1, 1'-binaphthyl are weighed out to obtain a protective gas atmosphere (argon), and in about 30 ml dissolved in dry toluene.
• the catalyst solution is introduced into an inertized stainless steel autoclave equipped with a glass liner, thermocouple, pressure transducer, liquid sampling point, gas feed and gas discharge.
• the reactor is additionally filled with 120 ml of dry toluene.
• the autoclave is charged with monosilane until a pressure of about 60 bar is reached. Subsequently, the reactor is additionally subjected to hydrogen until reaching a pressure of about 70 bar. Subsequently, the reactor is heated to the desired temperature and the stirrer (700 rev / min) started. After a reaction time of 20 h, the reaction is stopped, the reactor is expanded and the liquid phase is analyzed by gas chromatography. Table 1 below shows the results of gas chromatographic studies at 0.5, 1, 2, 3, and 20 hours after the start of the short chain hydridosilane distribution reaction.
• the pump When the valve position is open, the pump is switched on and the reaction mixture is passed directly to the membrane. After reaching a system pressure of 10 bar, the circulation pump is additionally switched on. The pressure is maintained via the built-in pressure relief valve. From the nanofiltration, the permeate is obtained on the membrane, which consists mainly of dissolved hydridosilanes in solvent. The resulting in the nanofiltration retentate contains the catalyst dissolved in the solvent consisting of Metallprecursor and ligands and impurities with more than 20 Si atoms. These are concentrated in the retentate. example 1
• the reaction mixture to be purified reaches the membrane module as a flat membrane test cell from Dauborn Membransysteme, Ratzeburg, with an area of 80 cm 2 .
• this module was a PDMS membrane of the type oNF2 GMT, Rheinfelden, D, which was overflowed with a transmembrane pressure of 15 bar at 100 L / h.
• the permeate flow rate was determined and the system retention was determined based on the catalyst constituents phosphorus and nickel in the mixed permeate and retentate.
• the reaction mixture to be purified enters the membrane module as a flat membrane test cell from Dauborn Membrane Systems, Ratzeburg, with an area of 80 cm 2 .
• This module was a Pl membrane of the type Starmem 240 of the company Grace, Littleton, CO, US, which was overflowed with a transmembrane pressure of 20 bar with 100 L / h. After obtaining 225 ml of permeate, the permeate flow rate was determined and the system retention was determined based on the catalyst constituents phosphorus and nickel in the mixed permeate and retentate.
• the reaction mixture to be purified reaches the membrane module as a flat membrane test cell from Dauborn Membransysteme, Ratzeburg, with an area of 80 cm 2 .
• this module was a Pl membrane of the type Starmem 240 of the company Grace, Littleton, CO, US, which was overflowed with a transmembrane pressure of 15 bar with 100 L / h.
• the permeate flow rate was determined and the system retention was determined based on the catalyst constituents phosphorus and nickel in the mixed permeate and retentate.
• Table 2 The results of the membrane separation of Examples 1, 2 and 3 are shown in Table 2 below.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Silicon Compounds (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Catalysts (AREA)

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• 2008
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