Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
  • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
  • C07D307/04—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having no double bonds between ring members or between ring members and non-ring members
  • C07D307/06—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having no double bonds between ring members or between ring members and non-ring members with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, directly attached to ring carbon atoms
  • C07D307/08—Preparation of tetrahydrofuran

Definitions

• the present invention relates to processes for the preparation of tetrahydrofuran by absorption of C4-dicarboxylic acids and / or derivatives thereof from a gaseous crude product mixture in an organic solvent or water as an absorbent, separation of the absorbent, catalytic hydrogenation of the thus obtained C4-dicarboxylic acids and / or their Derivatives and distillation of the hydrous crude tetrahydrofuran, in which the thus-obtained bottom product of the pure distillation of tetrahydrofuran is catalytically hydrogenated with complete or partial recycling in the process.
• the process according to the invention serves to improve the industrial production of tetrahydrofuran from maleic anhydride.
• Maleic anhydride is a valuable starting material, a raw material for polymers or is used for the hydrogenation of maleic anhydride (MSA) via the intermediate succinic anhydride (BSA) to produce gamma-butyrolactone (GBL), butanediol (BDO) and tetrahydrofuran (THF).
• MSA maleic anhydride
• BSA succinic anhydride
• GBL gamma-butyrolactone
• BDO butanediol
• THF tetrahydrofuran
• Maleic anhydride can be obtained by partial oxidation of hydrocarbons such as butane or benzene. From the maleic anhydride-containing exhaust gas of the partial oxidation, the desired product is usually absorbed in a solvent.
• DE-A 37 26 805 and DE-A 10 209 632 disclose distillation processes in which the crude tetrahydrofuran is passed through three distillation columns and the pure tetrahydrofuran is recovered via the side draw of the third column which serves for the purifying distillation or as its top product.
• a specification-compliant THF can also be obtained by these methods only if a still high THF-containing waste stream is withdrawn as the bottom product. This was previously classified as waste Ström accumulating bottom product contains up to 0.5 wt .-% of said minor components even more than 90 wt .-% THF.
• the present invention was based on the object of avoiding the high THF losses in the production of specification-compliant THFs.
• the process according to the invention makes it possible to almost completely avoid the THF losses of the distillation by recycling THF-containing waste streams from the distillation into the separation of the absorption medium or the hydrogenation of the C 4 -dicarboxylic acids and / or their derivatives, the recycling being carried out in the separation of the Absorbent is preferred.
• the majority (> 95%) of the THF contained in these streams is recovered without the specification of the pure product deteriorating.
• the theoretically expected accumulation of butyraldehyde resulting in the hydrogenation and contained in the THF-containing waste stream remains.
• C 4 -dicarboxylic acids and their derivatives are understood to mean maleic acid and succinic acid, optionally having one or more C 1 -C 6 -alkyl substituents, as well as the anhydrides of these optionally alkyl-substituted acids.
• An example of such an acid is citraconic acid.
• the respective anhydrides of a given acid are used.
• the educt used is maleic anhydride (MSA).
• the process of the invention may comprise an upstream step comprising preparing a MSA-containing crude product mixture by partial oxidation of a suitable hydrocarbon.
• suitable hydrocarbon streams are benzene, C4 olefins (eg n-butenes, C4 raffinate streams) or n-butane.
• N-butane is particularly preferred because it is a low-cost, economical starting material. Methods for the partial oxidation of n-butane are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 6 th Edition, Electronic Release, Maleic and Fumaric Acids-Maleic Anhydrides.
• the crude product mixture is then added as an absorbent or a mixture thereof in water or preferably in a suitable organic solvent, wherein the organic solvent spheres pressure at atmos- preferably has a higher by at least 30 0 C boiling point than MSA.
• the maleic anhydride-containing gas stream from the partial oxidation can be brought into contact in many ways at pressures (absolute) of 0.8 to 10 bar and temperatures of 50 - 300 0 C in one or more absorption stages with the solvent (absorbent): ( i) introducing the gas stream into the solvent (eg, via gas inlet nozzles or gassing rings), (ii) spraying the solvent into the gas stream, and (iii) countercurrently contacting between the upwardly flowing gas stream and the downwardly flowing solvent in a bottom or packed column.
• the apparatus known to those skilled in the gas absorption can be used.
• Suitable absorbents are: tricresyl phosphate, dibutyl maleate, butyl maleate, high molecular weight waxes, aromatic hydrocarbons having a molecular weight between 150 and 400 and a boiling point above 140 ° C, such as dibenzylbenzene; Alkyl phthalates and dialkyl phthalates having C 1 -C 6 -alkyl groups, for example dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-propyl and diisopropyl phthalate, undecyl phthalate, diundecyl phthalate, methyl phthalate, ethyl phthalate, butyl phthalate, n-propyl or iso - Propyl phthalate; Di-C 1 -C 4 -alkyl
• the resulting solution after treatment with the absorbent generally has an MSA content of about 5 to 400 grams per liter.
• the waste gas stream remaining after the treatment with the absorption medium contains, in addition to water, mainly the by-products of the preceding partial oxidation, such as carbon monoxide, carbon dioxide, unreacted butanes, acetic and acrylic acid.
• the exhaust stream is virtually free of MSA.
• the dissolved MSA is expelled from the absorbent or separated by distillation.
• the separation of the absorbent is preferably carried out by Stripping (stripping) with hydrogen at a maximum of 10% above the pressure of a subsequent hydrogenation of MSA to THF, BDO or GBL preferably at 100 to 250 0 C and pressures (absolute) from 0.8 to 30 bar carried out.
• Stripping stripping
• hydrogen is circulated between hydrogenation and stripping column (circulating gas).
• the thus obtained hydrogen / maleic anhydride stream is now fed to the hydrogenation zone.
• the catalytic hydrogenation of the C4-dicarboxylic acids and / or derivatives thereof is preferably carried out according to the process described in detail in WO 02/48 128, to which reference is expressly made.
• the hydrogenation is then preferably in the gas phase with a catalyst containing ⁇ 80 wt .-%, preferably ⁇ 70 wt .-%, in particular 10 to 65 wt .-% CuO and> 20 wt .-%, preferably> 30 wt.
• % in particular 35 to 90 wt .-% of an oxidic support with acidic centers, wherein the method at a hot-spot temperature of 240 to 310 0 C, preferably 240 to 280 ° C, and catalyst loads of 0.01 to 1, 0, preferably 0.02 to 1, in particular 0.05 to 0.5 kg Edukt / I catalyst hour performed.
• the catalyst according to WO 02/48 128 has copper oxide as the main catalytically active constituent. This is applied to an oxidic support which must have an appropriate number of acidic sites. The required amount of oxidic support depends on the amount of acidic sites contained therein.
• a suitable carrier material having a sufficient number of acidic sites is alumina, the use of which according to one embodiment of the present invention is preferred.
• the lower limit of the amount of carrier consisting of such material is 20% by weight.
• the amount of copper oxide is ⁇ 80% by weight.
• Preferred catalyst compositions comprise ⁇ 70% by weight of copper oxide and> 30% by weight of carrier, particularly preferred catalysts of from 10 to 65% by weight of copper oxide and from 35 to 90% by weight of carrier.
• the catalysts used in the invention which are chromium-free, one or more other metals or a compound thereof, preferably an oxide, from groups 1 to 14 (IA to VIIIA and IB to IVB of the old IUPAC nomenclature) of the Periodic Table of the Elements , If such a further oxide is used, it is preferable to use TiO 2, ZrO 2, SiO 2 and / or MgO.
• the catalysts used can also contain an auxiliary in an amount of 0 to 10 wt .-%.
• Auxiliaries are understood as meaning organic and inorganic Substances which contribute to improved processing during catalyst preparation and / or to an increase in the mechanical strength of the shaped catalyst bodies. Such aids are known in the art; Examples include graphite, stearic acid, silica gel and copper powder.
• the catalysts can be prepared by methods known to those skilled in the art, which are described in WO 02/48 128.
• An important parameter of the hydrogenation is the maintenance of a suitable reaction temperature. This is achieved on the one hand by a sufficiently high inlet temperature of the educts. This is at values of> 220 to 300 0 C, preferably 235 to 270 0 C. In order to obtain an acceptable or high THF selectivity and yield, the reaction must be carried out so that the catalyst bed on which the actual reaction takes place, a suitably high reaction temperature prevails.
• This so-called hot-spot temperature is set in the reactor after the entry of reactants and is at values of 240-310 0 C, preferably 240 to 280 ° C. The process is carried out so that the inlet temperature and the outlet temperature of the reaction gases are below this hot spot temperature.
• the hot-spot temperature is advantageously in the first half of the reactor, in particular in the presence of a tube bundle reactor.
• the hot spot temperature is 5 to 15 ° C, in particular 10 to 15 ° C, above the inlet temperature.
• the hydrogenation is carried out below the minimum temperatures of the hot spot temperature, in the case of using MSA as the starting material, the amount of GBL increases while the amount of THF decreases.
• deactivation of the catalyst by occupying with succinic acid, fumaric acid and / or BSA can be observed at such a temperature in the course of the hydrogenation.
• the catalyst loading of the hydrogenation according to the invention is in the range of 0.01 to 1.0 kg of starting material / liter of catalyst hour.
• a low hydrogen / reactant ratio is desirable.
• the lower limit is a value of 5, but generally higher hydrogen / reactant molar ratios of 20 to 400 are used.
• the use of the catalysts according to the invention described above and the observance of the above-described temperature values allow the use of favorable, low hydrogen / educt ratios, which are preferably from 20 to 200, preferably 40 to 150. The most favorable range is from 50 to 100.
• a part, advantageously the bulk, of the hydrogen is circulated.
• the cycle gas compressor known to those skilled in the art is generally used.
• the amount of hydrogen chemically consumed by the hydrogenation is supplemented.
• a portion of the cycle gas is discharged to remove inert compounds, such as n-butane.
• the one in the circle Guided hydrogen can also be used, optionally after preheating, to evaporate the educt stream.
• the volume flow of the reaction gases is an important factor of the method according to the invention.
• the GHSV values of the process according to the invention are values of 100 to 10,000 Nm 3 / m 3 h, preferably 1000 to 3000 Nm 3 / m 3 h, in particular 1100 to 2500 Nm 3 / m 3 h.
• the pressure at which the hydrogenation according to the invention is carried out is at values of 1 to 30 bar, preferably 2 to 9 bar, in particular 3 to 7 bar.
• the hydrogenation step according to the invention is preferably carried out in one or more separate reactors.
• the hydrogenation is preferably at least one tubular reactor such as at least one shaft reactor and / or at least one tube reactor used, with a single reactor can be operated in liquid or trickle mode. If two or more reactors are used, at least one can be operated in sump mode and at least one in trickle mode.
• the gas stream leaving the reactor is cooled to 10 to 60 ° C.
• the reaction products are condensed out and passed into a separator.
• the non-condensed gas stream is withdrawn from the separator and fed to the cycle gas compressor.
• a small amount of circulating gas is discharged.
• the condensed hydrogenation effluent, the crude hydrous THF, is continuously removed from the system and fed to the workup.
• the crude hydrous THF obtained by gas-phase hydrogenation of MSA is generally 61% by weight THF, 4% by weight n-butanol (n-BuOH), 0.7% by weight methanol (MeOH), 0.5% by weight of ethanol (EtOH), 1% by weight of propanol (ProOH), 400 ppm of gamma-butyrolactone (GBL), 120 ppm of butyraldehyde (BA), 100 ppm of butyl methyl ether (BME), further O-functionalized CH Compounds in concentrations ⁇ 200 ppm, as well as water.
• the crude hydrous THF is then purified by distillation in at least one distillation column.
• the waste streams of the distillation obtained during the distillative workup of the crude hydrous THF containing THF-containing can according to the inventive method to 0.1 to 99%, preferably 75% in the above-described production method of THFs, in particular in the separation of the Absorptionsmit- means or the hydrogenation of the C4-dicarboxylic acids and / or their derivatives are recycled.
• These THF-containing waste streams of the distillation generally contain up to 99% by weight of THF, up to 2% by weight of butanol, ethanol, propanol, GBL and 3-methyl THF and up to 5% n-butyraldehyde and butyl methyl ester.
• the crude hydrous THF is preferably purified by distillation with three columns as described, for example, in DE-A 37 26 805 and DE-A 102 09 632.
• THF-containing waste streams of the distillation of the crude hydrous THFs are preferably the bottom products in question.
• Distillation columns are the bottom product of the first and third column into consideration, wherein the bottom product of the third column is particularly preferred.
• the bottom product of the third column of the distillation process according to DE-A 37 26 805 or DE-A 102 09 632 which in each case serves for purifying the THF by itself, is particularly preferably used in the process according to the invention.
• This bottom product generally has up to 99% by weight of THF, up to 0.5% by weight of butanol, ethanol, propanol, GBL and water and up to 2% of n-butyraldehyde and butyl methyl ester and traces of methyl -THF on.
• This bottom product of the third column is particularly preferably obtained according to DE-A 102 09 632 by passing the crude hydrous tetrahydrofuran through three distillation columns, withdrawing water from the bottom of the first column, adding hydrous tetrahydrofuran from the top of the second column to the first column. , a side draw of the first column into the second column passes, the
• the bottom product of the third column of the distillation of the hydrous crude THF can be recycled as THF-containing waste stream in the separation of the absorbent or the hydrogenation of C4-dicarboxylic acids and / or their derivatives.
• the bottom product is preferably recirculated to the above-described removal of the absorbent before the hydrogenation of the C 4 -dicarboxylic acids and / or their derivatives and together with the C 4 -dicarboxylic acids and / or their derivatives obtained after separation of the absorbent into the catalytic hydrogenation to the THF be guided.
• This type of recycling is advantageous because a separate evaporator unit for the bottom product of the third column and a separate hydrogenation is saved.
• the bottom product of the third column of the distillation of the hydrous crude THF directly into the catalytic hydrogenation of the C4 dicarboxylic acids and / or derivatives thereof in the hydrogenation zone.
• the bottom product first evaporated and then preferably mixed with the hydrogen / maleic anhydride stream from the Absorptionsstoffabtrennung before or in the hydrogenation zone.
• the bottom product of the third column can also be catalytically dissolved in a separate hydrogenation zone, which may consist of one or more separate hydrogenation reactors. be hydrogenated and then recycled to the distillation.
• a separate hydrogenation zone which may consist of one or more separate hydrogenation reactors. be hydrogenated and then recycled to the distillation.
• the separate hydrogenation reactor for the hydrogenation stage of the process according to the invention is fed with exhaust gas hydrogen from the MSA hydrogenation to give THF.
• the recirculation preferably takes place in the first column, but recirculation into the second column is likewise possible.
• the hydrogenation of the bottom product in the separate hydrogenation takes place in the liquid phase of heterogeneous catalysts which may be fixed or suspended, with fixed catalysts (fixed bed catalysts) are preferred.
• the catalysts which can be used preferably contain at least one metal from the 7th, the 8th, the 9th, the 10th or the 11th group of the Periodic Table of the Elements or their compounds, for example oxides.
• the catalysts which can be used according to the invention more preferably contain at least one element selected from the group consisting of Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu and Au.
• the catalysts which can be used according to the invention comprise at least one element selected from the group consisting of Ni, Pd, Pt, Ru and Cu.
• the catalysts which can be used according to the invention furthermore preferably contain Pd, Pt, Ru or Ni.
• At least one heterogeneous catalyst is suitable, wherein at least one of the abovementioned metals (active metals) can be used as metal as such, as Raney catalyst and / or applied to a conventional support. If two or more active metals are used, they may be present separately or as an alloy. In this case, it is possible to use at least one metal as such and at least one other metal as Raney catalyst or at least one metal as such and at least one other metal applied to at least one support, or at least one metal as Raney catalyst and at least one other metal applied to at least one support, or at least one metal as such and at least one metal other than Raney's catalyst and at least one other metal applied to at least one support.
• active metals active metals
• the catalysts used may, for example, also be so-called precipitation catalysts.
• Such catalysts can be prepared by reacting their catalytically active components from their salt solutions, in particular from the solutions of their nitrates and / or acetates, for example by adding solutions of alkali metal and / or alkaline earth metal hydroxide and / or carbonate.
• Solutions for example, sparingly soluble hydroxides, oxide hydrates, basic salts or carbonates precipitates, the resulting precipitate then dries and then by calcination at generally 300 to 70O 0 C, in particular 400 to 600 0 C in the corresponding oxides, mixed oxides and / or mixed-valent oxides, which by treatment with hydrogen or hydrogen-containing gases in the range of generally 50 to 700 ° C, in particular 100 to 400 0 C are reduced to the respective metals and / or oxide compounds lower oxidation state and converted into the actual catalytically active form. This is usually reduced until no more water is formed.
• the precipitation of the catalytically active components can be carried out in the presence of the relevant support material.
• the catalytically active components can advantageously be precipitated simultaneously with the carrier material from the relevant salt solutions.
• Hydrogenation catalysts are preferably used which contain the hydrogenation-catalyzing metals or metal compounds deposited on a support material.
• such carrier materials are generally suitable for the process according to the invention, in which the catalytically hydrating component has been applied to a carrier material, for example by impregnation.
• the manner of applying the catalytically active metal to the support is generally not critical and can be accomplished in a variety of ways.
• the catalytically active metals can be applied to these support materials, for example, by impregnation with solutions or suspensions of the salts or oxides of the elements concerned, drying and subsequent reduction of the metal compounds to the respective metals or compounds of lower oxidation state by means of a reducing agent, preferably with hydrogen or complex hydrides .
• a reducing agent preferably with hydrogen or complex hydrides
• Another possibility for applying the catalytically active metals to these carriers is to impregnate the carrier with solutions of thermally easily decomposable salts, for example with nitrates or thermally easily decomposable complex compounds, for example carbonyl or hydrido complexes of the catalytically active metals, and the like impregnated carrier for thermal decomposition of the adsorbed metal compounds to temperatures in the range of 300 to 600 ° C to heat.
• This thermal decomposition is preferably carried out under a protective gas atmosphere.
• Suitable shielding gases are, for example, nitrogen, carbon dioxide, hydrogen or the noble gases.
• the catalytically active metals can be deposited on the catalyst support by vapor deposition or by flame spraying.
• the content of these supported catalysts on the catalytically active metals is in principle not critical to the success of the process according to the invention. In general, higher levels of catalytically active metals of these supported catalysts result in higher space-time conversions than lower levels.
• the supported catalysts whose content of catalytically active metals in the range of 0.01 to 90 wt .-%, preferably in the range of 0.1 to 40 wt .-% based on the total weight of the catalyst, is.
• these content data refer to the entire catalyst including carrier material, but the different carrier materials have very different specific weights and specific surface areas, it is also conceivable that these data can be exceeded or exceeded, without adversely affecting the result of the process according to the invention.
• the catalytically active metals may be applied to the respective carrier material.
• the catalytically active metals can be applied to the support, for example, by the process of DE-A 25 19 817, EP-A 1 477 219 or EP-A 0 285 420.
• the catalytically active metals are present as alloys which are produced by thermal treatment and / or reduction of, for example, by impregnation of the support material with a salt or complex of the abovementioned metals.
• chromium-containing catalysts Due to the toxicity of chromium-containing catalysts, preference is given to using chromium-free catalysts.
• chromium-free catalysts are also suitable for use in the process according to the invention, which, however, does not give rise to the desired advantages, which are, in particular, of environmental and operational nature.
• Both the activation of the precipitation catalysts and of the supported catalysts can also be carried out in situ at the beginning of the reaction by the hydrogen present. Preferably, these catalysts are activated separately before use.
• Suitable support materials both for precipitation catalysts and for supported catalysts are the oxides of aluminum and titanium, zirconium dioxide, silicon dioxide, clays such as montmorillonites, bentonites, silicates such as magnesium or aluminum silicates, zeolites such as the structural types ZSM-5 or ZSM-10, or activated carbon can be used.
• Preferred support materials are aluminas, titanium dioxides, silica, zirconia and activated carbon.
• carrier materials can also serve as carriers for catalysts which can be used in the process according to the invention.
• metallic supports on which the hydrogenation-active metal has been deposited for example Cu on the e.g. Pd, Pt or Ru was separated from the corresponding metal salts dissolved in water.
• catalysts according to the invention are supported catalysts which contain Ni, Pt and / or Pd, particular preferred supports being activated carbon, aluminum oxide, titanium dioxide and / or silicon dioxide or mixtures thereof.
• An inventively employable heterogeneous catalyst can be used as a suspension catalyst and / or as a fixed bed catalyst in the process according to the invention.
• the process according to the invention can be carried out batchwise, semi-continuously or continuously. Continuous performance is preferred.
• the experimental plant consists of an oxidation reactor, an absorption column for separating the MSA from the exhaust gas of the oxidation reactor by means of dibutyl phthalate (DBP) as a solvent, a column for stripping the maleic anhydride (MSA) from the solvent by means of hydrogen, the hydrogenation reactor, in the MSA to THF and the secondary components is hydrogenated and an interconnection of three columns according to DE 10209632 for purifying the THF.
• DBP dibutyl phthalate
• MSA maleic anhydride
• FIG. 1 experimental system is shown schematically.
• a stream of 99.8% by weight of THF, 0.1% by weight of butanol and 0.1% by weight of n-BA ("n BA metering") is fed into the absorption column.
• the composition of this stream corresponds to the actual composition of a bottom product of the third column of the pilot plant and simulates the return of this bottom product as THF-containing waste stream.
• the oxidation reactor was operated at a pressure of 2.9 bar and a temperature of 403 0 C with 41, 2 kg / h of air and 1, 4% butane at a conversion of about 83%.
• the MSA prepared in the oxidation was absorbed in the absorption column in dibutyl phthalate.
• the resulting solution consisting of 9.5% by weight MSA in dibutyl phthalate was charged at a flow rate of 60 g / h consisting of 99.8% THF, 0.1% butanol and 0.1% n-BA (n-butyraldehyde ), so that an n-BA concentration in the feed to the stripper of about 0.3 wt .-% n-BA was established.
• the result was a concentration of 0.0125 wt .-% n-BA in the discharge of the hydrogenation and a concentration of 1, 7 - 2 wt .-% in the bottom of the third column, at a take-off amount of a simulated THF-containing waste stream ( Bottom product of the third column) of 60 g / h corresponded.
• the maximum concentration of n-BA in the hydrogenation discharge is thus lower than the simulated concentration in the THF-containing waste stream.
• n-BA is converted into harmless compounds by this type of recycling.
• the yield of THF in the distillation was 97.5%.
• the experimental apparatus in this experiment corresponds to the scrubbing apparatus described under 1a), but no stream of 99.8% by weight of THF, 0.1% by weight of butanol and 0.1% by weight of nitrogen is introduced into the absorption column. BA (“n BA dosage”) fed.
• the yield of THF in the distillation was 99. 5%.
• the comparison of inventive and comparative example shows that no adjustment of the by-products by the recycling takes place.
• the THF yield could be recovered by recovering THF from waste streams by 2%. could be increased.

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• 2009
  • 2009-11-05 EP EP09744694A patent/EP2356098A1/de not_active Withdrawn
  • 2009-11-05 WO PCT/EP2009/064660 patent/WO2010054976A1/de active Application Filing
  • 2009-11-05 US US12/740,468 patent/US20110245517A1/en not_active Abandoned
  • 2009-11-05 CN CN200980101073.7A patent/CN101868449B/zh not_active Expired - Fee Related
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