Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C68/00—Preparation of esters of carbonic or haloformic acids
  • C07C68/02—Preparation of esters of carbonic or haloformic acids from phosgene or haloformates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
  • B01J31/0234—Nitrogen-, phosphorus-, arsenic- or antimony-containing compounds
  • B01J31/0235—Nitrogen containing compounds
  • B01J31/0244—Nitrogen containing compounds with nitrogen contained as ring member in aromatic compounds or moieties, e.g. pyridine
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
  • B01J31/0234—Nitrogen-, phosphorus-, arsenic- or antimony-containing compounds
  • B01J31/0271—Nitrogen-, phosphorus-, arsenic- or antimony-containing compounds also containing elements or functional groups covered by B01J31/0201 - B01J31/0231
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C68/00—Preparation of esters of carbonic or haloformic acids
  • C07C68/08—Purification; Separation; Stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
  • C07C69/96—Esters of carbonic or haloformic acids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
  • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
  • B01J2231/49—Esterification or transesterification
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/001—General concepts, e.g. reviews, relating to catalyst systems and methods of making them, the concept being defined by a common material or method/theory
  • B01J2531/002—Materials
• • 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
• • 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
  • Y02P20/584—Recycling of catalysts

Definitions

• the invention relates to a process for the preparation of diaryl carbonates from monophenols and phosgene or aryl chloroformates in the presence of at least one optionally substituted pyridine or its hydrochloride salt as a catalyst, and its recovery and recycling in the process.
• the process is carried out, at least in part, in the liquid phase without the use of additional solvents, the catalyst being separated by crystallization and recovered.
• diaryl carbonates processes for the preparation of diaryl carbonates from monophenols and phosgene are known.
• the preparation of diaryl carbonates (such as diphenyl carbonate, "DPC") is usually carried out by a continuous process, by preparing phosgene and then reacting monophenols and phosgene in an inert solvent in the presence of alkali and a nitrogen catalyst in the interface.
• DPC diphenyl carbonate
• diaryl carbonates e.g. by the phase boundary process is described in principle in the literature, see e.g. in Chemistry and Physics of Polycarbonates, Polymer Reviews, I i. Schnell, Vol. 9, John Wiley and Sons, Inc. (1964), p. 50/51.
• US Pat. No. 2,362,865 (A) describes a process for preparing diaryicarbonates by direct phosgenation of monophenols at temperatures of 170 ° C. to 250 ° C. using Al or Ti phenolates, but without recycling the catalyst let alone a separation method is described.
• Both EP 2 371 806 A1 and EP 2 371 807 A1 likewise disclose processes for the preparation of diaryic carbonates by direct phosgenation of monophenols at from 20 ° C. to 240 ° C. using metal halides or metal phenates described. Recycling of the catalyst in the process has also not been described.
• EP 1 234 845 A likewise describes the reaction of monophenols in the melt at temperatures of 120 ° C. to 190 ° C. with a particularly pure phosgene.
• nitrogen-containing compounds e.g. Pyridine in amounts of 0.1 to 10 mol% based on the Monophenoi used. Also, this publication gives no indication of recycling of catalyst in the process.
• JP 10-077250 A, JP 09-24278 A and EP 1 234 845 A there is evidence for a possible recycling of catalyst, but without a specific separation of the catalyst from the product and a work-up method of the catalyst with regard to a return enter into.
• aqueous solutions in particular water and / or sodium hydroxide solution, in the course of neutralization and washing of the reaction mixture.
• No. 5,239,106 teaches the separation of diphenyl carbonate from catalyst-containing reaction solutions by crystallization of the 1: 1 adduct with phenol. However, no catalyst separation and recycle is described here.
• Feedstocks for further chemical processes are.
• the invention therefore provides a process for the preparation of diaryl carbonate, preferably diphenyl carbonate by reaction of a monophenol with phosgene and / or at least one aryl chloroformate in the presence of at least one optionally substituted pyridine, in free form and / or in the form of its hydrochloride salt, as catalyst, wherein
• reaction is carried out in a reactor under pressures of 1 to 50 bar (absolute),
• the catalyst-containing mother liquor is at least partially recycled to the reactor of step a).
• steps a) to e) uses an aqueous solution.
• the reaction in step a) is preferably carried out at temperatures above 80 ° C., in order to avoid deposits of formed diaryl carbonates in solid form.
• the reaction of the educts can be carried out both at atmospheric pressure or slightly reduced pressure and at elevated pressures of up to 50 bar (absolute).
• the phosgene may be present in the condensed phase or dissolved in the liquid phase. Due to their high purity, the diaryl carbonates prepared by this process are particularly suitable for the production of high-purity polycarbonates by the melt transesterification process from diaryl carbonates and bisphenols.
• the hydrogen chloride obtained in the reaction can be subjected to one or more purification steps, so that it is suitable for a large number of other possible uses, in particular for electrochemical or thermal oxidation to chlorine.
• This chlorine thus obtained can be used with carbon monoxide for the production of phosgene; the phosgene obtained can be used in the process according to the invention.
• the end product which is liquid under the reaction conditions is separated in a plurality of separation steps comprising steps b) to d) from by-products and the catalyst or its HCl adduct. Thereafter, it preferably has a content of more than 95%, preferably more than 99.0%, more preferably more than 99.5%> diaryl carbonate and optionally phenol.
• the end product preferably contains a majority of diaryl carbonate.
• the catalyst used in the reaction is worked up so that it can be at least partially recycled to the reaction (step e)).
• the method according to the invention consists of the three method sections:
• the starting materials are mixed together in an upstream process step in such a way that a substantially homogeneous solution of phosgene is present in the molten monophenol; This may optionally be done by applying increased pressures at the predetermined melt temperatures.
• Diaryl carbonates prepared in the context of the invention are preferably those of the general formula (I) wherein R 'and R "independently of one another may be hydrogen, halogen or a branched or unbranched C to Cg-alkyl radical or a branched or unbranched C to C9-alkoxycarbonyl radical, preference being given to R, R' and R" on both sides of the formula (I) the same.
• diphenyl carbonate Particularly preferred is diphenyl carbonate.
• Monophenol (s) suitable for the invention are preferably those of the general formula
• C 1-8 -alkyl is, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, "G-C 1-4 -alkyl” for example, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, neo-pentyl, 1-ethylpropyl, cyclohexyl, cyclopentyl, n-hexyl, 1, 1-dimethylpropyl, 1,2-dimethylpropyl, 1, 2 Dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1, 1-dimethylbutyl, 1, 2-dimethylbutyl, 1, 3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3, 3-dimethylbuty
• Suitable monophenols are, for example: phenol, alkylphenols such as cresols, p-tert-butylphenol, p-cumyliphenol, pn-octylphenol, p-iso-octylphenol, pn-nonylphenol and p-isononylphenol, halophenols such as p-chlorophenol, 2,4-dichlorophenol, p-bromophenol, 2,4,6-tribromophenol, anisole and salicylic acid methyl or phenyl ester. Particularly preferred is phenol.
• the monophenols used should have a purity of at least 99.90% by weight.
• the educts preferably contain less than 300 vol. ppm water as the presence of water favors corrosion of the equipment materials.
• the monophenol used here in addition to the introduced from the outside in the overall process phenol, the so-called fresh phenol from storage tanks, also recycled monophenol from condensate streams of the process s steps II) and III) or from washing liquid streams of the process s step II) included.
• Such recirculated monophenol may contain by-products from the process, e.g. Residual amounts of diaryl carbonate, hydrogen chloride or aryl chloroformate, which are harmless to the reaction.
• the monophenol is preferably present in more than the stoichiometrically required amount based on phosgene.
• the molar ratio of monophenol to phosgene may vary from 1.5: 1 to 4: 1, preferred is a molar ratio of 2: 1 to 3: 1, more preferably a molar ratio of 2.5: 1 to 3: 1.
• Chloroformic acid aryl ester is used below for compounds which arise in the preparation of diaryl carbonates from monophenols and phosgene as an intermediate.
• Aryl chloroformates suitable for the purposes of the invention are preferably those of the general formula (III)
• phenyl chloroformate Particularly preferred is phenyl chloroformate.
• the phosgene used should have a purity of at least 99.80% by weight, preferably of 99.96% by weight, in order to avoid undesired by-products in the end products of the preparation process; the content of carbon tetrachloride should be less than 50 vol. ppm. preferably less than 15 vol. be ppm.
• a substituted or unsubstituted pyridine is used as the catalyst.
• This can be in the form of the free base or completely or partially in the form of its hydrochloride.
• “In the form of the free base” or “in free form” in the sense of the invention means that the nitrogen of the pyridine ring is not present in protonated form.
• At most 10 mol%, particularly preferably at most 1 mol%, of the optionally substituted pyridine are in free form.
• the remainder is in the form of the hydrochloride.
• the pyridines serving as catalyst according to the invention are preferably those of the general formula (IV)
• R 1 and R are independently H, branched or unbranched ci to »alkyl, C or Ce-cycloalkyl, OH.
• OR 3 NHR 3 or R 'R' '* may, where R 3 and R 4 independently represent Ci to (VAlkyl.
• R 1 and R is H.
• Suitable pyridines are for example, pyridine, 2-Picoiin , 3-picoline, 4-picoline, 2-ethylpyridine,
• 3-ethylpyridine 4-ethylpyridine, 2-isopropylpyridine, 3-isopropylpyridine, 4-isopropylpyridine, 2-butylpyridine, 4-tert-butyipyridine, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2, 6-lutidine, 3,4-lutidine, 3,5-lutidine, 3,4-diethylpyridine, 3,5-diethylpyridine, 3-ethyl-4-methylpyridine, 2- (3-pentyl) pyridine,
• the catalyst is pyridine hydrochloride.
• the catalysts to be used according to the invention can be used in amounts of from 0.001 mol% to 10 mol%, preferably in amounts of from 0.01 mol% to 5 mol%, based on the amount of monophenol present.
• the catalysts are used as a solution in the monophenol Schmeize. According to the invention, such solutions contain at least partly amounts of catalyst which are recycled from the process section III), with or without separate catalyst workup, into the reaction as process section I). A catalyst workup is therefore not necessarily required for the recycling of the catalyst in the process section I) but quite possible.
• the addition of the catalysts is carried out at the earliest after complete mixing of the reactants, preferably in the reactor, in order to avoid premature Reakti n of the reactants during mixing and thus premature hydrogen chloride evolution in an inappropriate process section.
• a return of amounts of catalyst from the process section III) can be made as often as desired;
• a partial amount of the catalyst can be recycled continuously, while optionally a partial amount is discharged from the process cycle in order to prevent impurities in the catalyst or possibly to take into account a deactivation of the catalyst.
• fresh catalyst can be added to the recycled catalyst charge.
• at least 25% by weight of the catalyst is recycled, more preferably at least 50% by weight, most preferably at least 75% by weight, and most preferably at least 85% by weight.
• at most 99% by weight of the catalyst are recycled, preferably at most 95% by weight.
• the educts monophenol and phosgene are mixed together in the abovementioned molar ratios or in the abovementioned preferred molar ratios, the
• Monophenol is always present as a melt and the phosgene is gaseous or liquid depending on the prevailing Dmck.
• the solubility of phosgene in monophenols, as well as in diaryl carbonates decreases with increasing temperature. Therefore, mixtures of molten monophenols and phosgene must be very intensively mixed and redispersed in the reaction phase in order to ensure a sufficient conversion of the educts via a sufficient renewal of the phase boundary surfaces.
• the conversion of phosgene with phenol in a condensed homogeneous phase can be significantly increased.
• the increase in temperature has an accelerating effect on the reaction rate, so that elevated temperatures in the range of 100 ° C to 250 ° C, preferably 110 ° C to 220 ° C may be advantageous. Since such temperatures, as mentioned above, however, counteract the solubility of phosgene in phenol, a reaction at elevated temperature under pressure is particularly advantageous.
• the starting materials are mixed at elevated temperature under atmospheric pressure, preferably under elevated pressure up to 50 bar (absolute), more preferably at elevated pressure to 30 bar (absolute) and most preferably at pressures of 4 to 25 bar (absolute) and reacted.
• the temperature in the mixing zone should be at least the melting temperature of the monophenol, but a reaction temperature is advantageous in the
• one of the abovementioned catalysts is added to the mixture, preferably in the preferred amount, as a solution in monophenol. Since at the abovementioned temperatures and pressures the catalyzed reaction of monophenol with phosgene to give the aryl chloroformate as an intermediate proceeds very rapidly with elimination of gaseous hydrogen chloride, the reaction can preferably be carried out in several stages. The reaction can be conducted under adiabatic conditions since it has only a slight heat of reaction.
• the so-called main reactor formed particularly at elevated pressure and preferably at temperatures of 120 ° C to 230 ° C, more preferably at temperatures of 130 ° C to 210 ° C and for the preparation of diphenyl carbonate most preferably in a Temperature of 170 ° C to 200 ° C and at reactor-liquid residence time of 15 to 120 minutes, preferably from 45 to 90 minutes, predominantly Arylchlorkohlenquiper in addition to already further reacted diaryl carbonate.
• the aryl chloroformate reacts at somewhat higher temperatures of preferably 170 ° C. to 250 ° C., particularly preferably 190 ° C. to 230 ° C., and very particularly preferably 200 ° C.
• the pressure in the second stage in the so-called post-reactor can also be lowered to 2 to 20 bar.
• Such a lowering of the pressure can be advantageously carried out in a so-called flash stage, in which, as a result of the pressure reduction, the hydrogen chloride gas produced in the main reactor particularly well from the reaction melt can be separated.
• Also behind the second reaction stage in the post-reactor can optionally be a flash stage for the separation of the residual amounts of hydrogen chloride.
• continuous reactors are well suited, but it is also possible to use stirring cakes as batch reactors.
• Particularly suitable continuous reactors are e.g. Rrockkesselkaskaden, Biasen yarnlen columns, bottom columns, packed Koionnen or columns with fixed internals for mixing the reaction medium or reaction distillation columns.
• Such columns may also be combined with each other, e.g. a bubble column column with an attached rectification column, wherein deviating from the above-described mixture of the reactants, the starting materials can be introduced separately at different points of the column combination.
• the phosgene in the lower bubble column and the monophenol are introduced together with the catalyst in the upper rectification column with about 10 theoretical plates.
• the resulting diaryl carbonate is removed from the bubble column column.
• a correspondingly separate metering of the educts can also be carried out in a reaction distillation column in such a way that the phosgene is introduced in the middle of the column and that the monophenol is introduced together with catalyst at the top of the column.
• the reaction mixture is removed from the column bottom.
• Such columns may have at least 5, preferably about 20 trays.
• the starting materials can be used in one
• Main reactor at pressures of 1 to 25 bar (absolute) at sufficiently high, possibly longer residence time but lower temperatures in the lower part of the reactor of preferably 120 ° C to 190 ° C, more preferably from 160 ° C to 180 ° C are fully implemented.
• an additional heating is required in order to realize somewhat higher temperatures up to 250 ° C., preferably up to 230 ° C.
• the extensive degassing of the reaction mixture and separation of the low boilers can then be carried out by a flash evaporation or other degassing.
• bias column columns which are flowed through from bottom to top with the educt mixture as described above.
• the gaseous hydrogen chloride and at the upper end of the column shaft the reaction mixture are removed at the column head of the bubble column column.
• the completely reacted reaction mixture is removed at the end of a rejection reactor and fed to the subsequent process section III), product purification and catalyst separation by suspension crystallization.
• the respectively withdrawn at the top of the bubble column columns hydrogen chloride gas is combined in the subsequent process section II), the hydrogen chloride work-up.
• An additional separation of chlorine gas is also possible between the individual stages by relaxing in a flash and then increasing the pressure.
• the apparatus materials must meet the high requirements for resistance to hydrogen chloride and phosgene at high temperatures and are preferably selected from the group of materials black steel, stainless steel, steel alloys, nickel-based alloys (eg Hastelloy C), ceramics, graphite, Enamel-coated materials, PTFE-clad materials.
• the gas phase formed in the reaction A) is collected and the hydrogen chloride gas separated from the other components, optionally for a further conversion to diaryl carbonate can be ceremoniesge leads.
• the by-product hydrogen chloride can be distilled to increase the purity.
• the gas-shaped partial flow from process section III) can be admixed.
• the HCl-haitigen material streams from process section I) are combined and purified together.
• the hydrogen chloride is not neutralized.
• the major product among the low boiling components is 94% or more by weight of the hydrogen chloride gas;
• By-products are the excess monophenol at more than 3% by weight, as well as traces of aryl chloroformate, diaryl carbonate and phosgene, and by-product from the phosgene traces of carbon monoxide and carbon tetrachloride.
• the by-products can largely be separated off by various steps from the main product chlorine gas, so that a hydrogen chloride gas having a purity of more than 99.0% by volume, preferably more than 99.8% by volume and a residual content of phosgene and or chlorine-Kohienhoffm of less than 1000 vol. ppm, preferably less than 500 vol. ppm is obtained.
• a hydrogen chloride gas having a purity of more than 99.0% by volume, preferably more than 99.8% by volume and a residual content of phosgene and or chlorine-Kohienklam of less than 1000 vol. ppm, preferably less than 500 vol. ppm is obtained.
• the content of organic compounds in Chlorwas s réelleo ff smaller than 1000 vol. ppm, preferably less than 50 vol. ppm, in particular the content of chlorine-containing hydrocarbons should be less than 50 vol. be ppm.
• This object is achieved by one or more steps, which are described below.
• this object is
• first condensation stage the by-products are condensed out at a higher boiling point than that of hydrogen chloride at a suitable temperature.
• higher-boiling components which are present in greater concentration such as monophenols and diaryl carbonates, are largely removed from the chlorine gas, which can be recycled to the reaction.
• This separation succeeds particularly well when, in addition to the lower temperature optionally also increased pressures are applied.
• Preferred temperatures in the first condensation stage are at least 80 ° C, and for the preparation of diphenyl carbonate particularly preferably 90 ° C.
• the pressure is preferably set in a range of 8 to 25 bar (absolute), a particularly preferred pressure for the preparation of diphenyl carbonate is 12 bar (absolute).
• the condensation of the by-products from the hydrogen chloride gas stream can optionally also be carried out in several stages at different temperatures and / or pressures.
• this first condensation stage can also be skipped to remove the by-products in a subsequent so-called HCl washing stage in a suitable apparatus with molten diaryl carbonate from the To wash out hydrogen chloride stream.
• this HCl wash step represents the first hydrogen chloride purification step, bypassing the first condensation step, this HCl wash step can also be multistage and operate at various, decreasing temperature levels to increase the efficiency of the wash , In particular, monophenols dissolve very well in the diaryl carbonate. Even traces of chloroformate and phosgene can still be converted into the diaryl carbonate in this process step when the diaryl carbonate used for washing z. B.
• diaryl carbonate is taken on processing.
• every diaryl carbonate stream of this process is suitable up to the distilled diaryl carbonate for the HCl scrubbing step; it is advantageous for the reaction of said organic chlorine compounds to have a diaryl carbonate stream containing catalyst and phenol for the HCl washing stage, the process section III) to take in order to bring in a short time the remaining in the hydrogen chloride gas organic chlorine compounds to react.
• Such a suitable diaryl carbonate is Process Section I) (Reaction) leaving
• Diaryl carbonate can be used in any way for the HCl washing step, since the physical solubility of the by-products to be washed in the DPC is sufficiently high.
• a pure distilled diaryl carbonate is used for the HCl wash step.
• monophenol can also be used instead of the diaryl carbonate as the washing medium, since the physical solubility of the by-products to be washed out is also sufficiently high in monophenol.
• This monophenol may e.g. be a partial stream of the monophenol-educt current. If a reaction of chloroesters or phosgene to diaryl carbonate is desired, then the monophenol used for washing may contain catalyst in any manner.
• the HCl wash with diaryl carbonate or with monophenol is preferably carried out at temperatures above the melting point of the diaryl carbonate; in the preparation of diphenyl carbonate, a melt temperature of 80-95 ° C is particularly preferred.
• the HCl wash can be carried out at atmospheric pressure or at elevated pressure of 8 to 25 bar (absolute); in the preparation of diphenyl carbonate 12 bar (absolute) are particularly preferred.
• a hydrogen chloride gas having a purity of more than 99.8% by weight can be obtained.
• the proportion of phosgene is less than 500 vol. ppm of chloroformate below the detection limit and the phenol content is reduced to less than 10 vol. ppm reduced.
• This HCl wash step is not mandatory and can be bypassed with any combination of other process steps.
• a hydrogen chloride distillation is particularly well suited.
• the preceding cooling of the chlorine water to be purified which is to lower temperatures in an upstream second condensation stage, makes sense, but is not absolutely necessary. If this step is omitted, a correspondingly higher energy at low temperatures is required in the subsequent hydrogen chloride distillation.
• this second condensation stage which can optionally also operate at a plurality of different temperature and / or pressure levels, the traces of higher-boiling by-products still present in the hydrogen chloride gas are separated, in particular when higher pressures in the range from 8 to are used 25 bar (absolute), with diphenyl carbonate preferably 12 bar (absolute).
• the temperatures can vary over a very wide range from plus 25 ° C to minus 50 ° C.
• This second condensation stage is particularly highly recommended if the laundry was carried out in the HCl washing stage with monophenol, since in this way the im HCl gas stream present concentration of monophenol can be significantly lowered and thus the HCi distillation is relieved. If this second condensation stage is omitted, the requirements for the energy requirement in the HCl distillation are correspondingly much higher.
• the condensates may also be fed to the reaction as in the first condensation stage.
• the hydrogen chloride distillation in a particularly preferred embodiment is particularly well suited for the production of a highly pure hydrogen chloride. It should preferably be carried out at elevated pressure, since otherwise the energy expenditure for setting alternatively required sufficiently low temperatures would be disproportionately high. If previous cleaning stages have been carried out at normal pressure, then at the latest in this purification stage, a compression of the hydrogen chloride stream to higher pressures of 8 to 25 bar (absolute) is highly recommended; for the preparation of diphenyl carbonate 12 bar (absolute) are particularly preferred. Under these conditions, a hydrogen chloride gas having a purity of 99.95% by weight is available.
• All of the four above-mentioned stages of the hydrogen chloride purification in process stage II) are, in the order described, particularly suitable for producing a high-purity hydrogen chloride gas according to the invention.
• the observance of certain sequences or the execution of all stages of the process is not absolutely necessary, but depends on the degree of contamination of the hydrogen chloride separated from the reaction and on the desired purity of the hydrogen chloride gas as the end product. For example, it may well be possible to achieve the desired result with individual purification stages or a single purification stage, as shown below using the example of HCi distillation.
• a combination of the purification stages can certainly be carried out in a specific sequence which is independent of the above-mentioned list in order to achieve specific degrees of purity.
• Ais apparatuses for carrying out the first and second condensation stage are classic cold traps with a sufficiently high heat exchanger surface for the process conditions and a device for feeding the condensates into the reaction. Falling such cooling can also be carried out in several stages and optionally tempered differently.
• Suitable apparatuses for the HCl washing stage are, in particular, continuously operated apparatuses, such as, for example, bubble column columns, bubble tray columns, packed columns, packed columns, columns with fixed internals, in which the scrubbing liquid from above opposes the ascending hydrogen chloride gas be guided.
• continuously operated agitators such as mixer-settler or discontinuously operated stirring apparatus are suitable in principle.
• the hydrogen chloride distillation can be carried out in customary distillation or rectification columns with suitable column internals.
• Resistance to hydrogen chloride at high temperatures are and are preferably selected from the group of black steel, stainless steel, steel alloys, nickel base alloys (e.g., Hastelloy C), ceramics, graphite, enamel coated materials, PTFE clad materials.
• the Prodii klau free n i gun g and catalyst separation, the higher boiling components formed in the reaction I) are collected, separated and the catalyst, in the form of the free base or in the form of Hydrochlordids, recycled into the reaction.
• the main product is purified to such an extent that a Diaiylcarbonat having a purity of more than 99.0% by weight, preferably of more than 99.8% by weight, particularly preferably more than 99.95% by weight is obtained.
• a suspension crystallization step Preferably, a thennischer separation step is inserted before the crystallization, particularly preferably a combination of a distillative separation step with a suspension crystallization step. With the aid of the distillative separation step, the ratio of monophenol to diaryl carbonate can be adjusted for the subsequent suspension crystallization (step c).
• the ratio of monophenol to diaryl carbonate in the solution used in step c) is preferably at least 0.5: 1, particularly preferably at least 1: 1, very particularly preferably at least 1.5: 1.
• the ratio of monophenol to diaryl carbonate in the solution obtained in step a) is at least 0.5: 1, particularly preferably at least 1: 1, very particularly preferably at least 1.5: 1.
• the suspension crystallization in step c) is initiated by lowering the temperature.
• the temperature is lowered to below 70 ° C, preferably below 60 ° C.
• dissolved hydrogen chloride is largely separated in a degassing.
• This can be achieved with a flash (A in Figure 1), a distillation column, a combination of these apparatuses, or another conventional degassing technique (e.g., stripping).
• pressures of 20 mbar to 1 bar (absolute) and temperatures of 140 ° -205 ° C are selected, preferably pressures of 0.1 bar to 1 bar (absolute) and temperatures of 165-205 ° C and more preferably pressures of 0 , 3-0,7 bar (absolute) and temperatures of 180-200 ° C.
• a distillation column can be used for the separation of chiorrous sulphide at pressures of from 200 mbar to 2 bar (absolute), preferably from 0.5 bar to 1 bar (absolute), more preferably from 0.8 to 1.5 bar. 1.0 bar (absolute) is operated.
• the catalyst is recovered from the diaryl carbonate-containing, hydrogen chloride-purified reaction solution by suspension crystallization to obtain a catalyst system containing mother liquor and a crystallizate.
• the mother liquor may be at least partially recycled to the reactor for the preparation of the diaryl carbonate or further worked up.
• the mother liquor is at least partially treated and this recycled mother liquor at least partially recycled to the reactor for the preparation of the diaryl carbonate.
• the crystals can be worked up to pure diaryl carbonate and pure monophenol
• the reaction solution from the reaction part I) is removed and recovered in a suspension crystallization of the reaction product, optionally by seeding the reaction solution with Diaiylcarbonat monophenol adduct crystals, a catalyst-containing mother liquor. Any residues of the catalyst can be washed from the crystals with an anhydrous wash solution, preferably a mixture of diaryl carbonate and aromatic hydroxy compound.
• anhydrous wash solution preferably a mixture of diaryl carbonate and aromatic hydroxy compound.
• the thus liberated from the catalyst system and other impurities crystallizates, consisting of a mixture of diaryl carbonate and aromatic hydroxy compound can be worked up lossless by crystallization or distillation in high purity diaryl carbonate and the reaction system containing the catalyst system are recycled to the reactor.
• the washing solution can then be fed without further treatment of the reaction as feed supplement of the aromatic hydroxy compound.
• FIG. 1 shows a particularly preferred embodiment of the method according to the invention.
• the letters in FIG. 1 have the following meanings:
• this suspension crystallization can be used to fulfill the task of separating the pyridine-HG catalyst from the reaction solution, and its exhaust slaughterun in process section I).

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• 2015
  • 2015-05-05 WO PCT/EP2015/059774 patent/WO2015169775A1/de not_active Ceased
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