Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/04—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds
• • 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 continuous process for the preparation of the tert. -Butyl ester of an aliphatic C 1 -C 4 carboxylic acid by reacting the carboxylic acid with isobutene.
• tert-butyl esters of aliphatic C 1 -C 4 -carboxylic acids are widely used.
• the tert-butyl esters of saturated aliphatic carboxylic acids such as tert-butyl acetate are used, for example, as solvents.
• Tert.-butyl esters of (meth) acrylic acid are important starting materials for the production of polymers, which are used, among other things, as a component of paint dispersions, adhesives or paint resins.
• the production of tert-butyl esters is generally carried out by acid-catalyzed addition of the corresponding carboxylic acids to isobutene (Houben-Weyl, Methods of Organic Chemistry, Vol.
• the catalysts used are acids soluble in the reaction mixture, e.g. B. mineral acids or alkyl or arylsulfonic acids (DE-A-12 49 857, US 3,087,962, US 3,088,969) or insoluble catalysts such as acidic exchange resins (US 3,037,052, US 3,031,495, DE-A-31 05 399, EP-A-268 999).
• the carboxylic acids are usually reacted with isobutene in conventional reaction containers or in columns
• the reaction mixture obtained is first freed from the catalyst.
• this is generally carried out by washing with water and / or neutralization with an aqueous alkali solution (DE-A-11 28 428) or by distillation (DE-A-12 49 857).
• the reaction mixture freed from the catalyst is then worked up by distillation.
• the formation of the isobutene oligomers can also be reduced by using gaseous isobutene (DE-A-11 35 897).
• gaseous isobutene DE-A-11 35 897.
• the disadvantage is the necessary evaporation of the liquid isoolefin and the handling of large amounts of gas.
• polymerization inhibitors such as phenothiazine, hydroquinone or tert-butyl catechol or mixtures thereof, are frequently used, optionally with simultaneous addition of air, added. However, this does not completely prevent polymer formation.
• the present invention is therefore based on the object of providing a technically simple, economical and environmentally friendly process for the preparation of tert-butyl esters of aliphatic carboxylic acids.
• the present invention therefore relates to a process for the preparation of the tert-butyl ester of an aliphatic C 1 -C 4 carboxylic acid by reacting the carboxylic acid with isobutene in the liquid phase in the presence of an acidic catalyst and recovering the ester from the reaction mixture obtained, the The reaction is carried out in a reactor divided into several sections and the carboxylic acid, the isobutene and the catalyst are fed into the first zone of the reactor, the reaction temperature in the reactor being controlled so that it is in the range from 10 to 40 ° C. and in the first section is highest.
• the aliphatic C 1 -C 4 -carboxylic acids are in particular formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, acrylic acid or methacrylic acid, acrylic acid or methacrylic acid being particularly preferred.
• the isobutene is preferably fed into the first section of the reactor in liquid form.
• the quantitative ratio of carboxylic acid to isobutene can vary within a wide range. However, the carboxylic acid is preferably used in excess (on a molar basis). The molar ratio of carboxylic acid: isobutene is preferably in the range from 1.1: 1 to 1.5: 1.
• the process is generally carried out in the absence of a solvent.
• the catalysts used are therefore those which are at least partially soluble in the reaction mixture.
• the inorganic catalysts are only partially soluble in the reaction mixture at the start of the reaction.
• Such catalysts are therefore partially finely dispersed in the reaction mixture, especially in the first and second sections.
• the catalyst becomes more soluble (primarily due to the formation of a partial ester of the catalyst, for example the half-ester of sulfuric acid). At least in the last section it is therefore generally dissolved in the reaction mixture.
• Useful catalysts are strong inorganic or organic acids, such as mine ralic acids, for example sulfuric acid, phosphoric acid and polyphosphoric acid, preferably sulfuric acid or sulfonic acids, such as p-toluene, benzene, dodecylbenzene, and methanesulfonic acid.
• mine ralic acids for example sulfuric acid, phosphoric acid and polyphosphoric acid
• sulfuric acid or sulfonic acids such as p-toluene, benzene, dodecylbenzene, and methanesulfonic acid.
• the amount of catalyst is generally about 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the starting materials carboxylic acid and isobutene.
• the reaction is generally also carried out in the presence of an inhibitor which inhibits the polymerization of the unsaturated carboxylic acid or the ester.
• an inhibitor which inhibits the polymerization of the unsaturated carboxylic acid or the ester.
• Particularly suitable inhibitors are hydroquinone, hydroquinone monomethyl ether, p-benzoquinone, p-nitrosophenol, phenothiazine, 4-hydroxy-2,2,6, 6-tetramethyl-1-oxyl-piperidine and methylene blue.
• the inhibitors are generally used in amounts of about 200 to 2000 ppm, based on the weight of the carboxylic acid and isoolefin feedstocks.
• the process according to the invention is carried out in a reactor, which is in particular a cylindrical reactor.
• the reactor is divided into several, preferably 3, 4 or 5, separate sections.
• the sections are separated from one another by dividing walls which run perpendicular to the longitudinal axis of the reactor. These each have at least one opening to allow the reaction mixture to pass from one reactor section to the next.
• the number of openings per partition depends on the size of the reactor.
• the partition walls preferably have an opening, which is located in particular in the middle of the partition wall.
• the total area of the openings per partition is approximately 1/2000 to 1/500 of the reactor cross-sectional area.
• the volume of the reactor sections can be the same or different.
• the volume of the first reactor section is preferably greater than that of the remaining sections. In a reactor with four sections, the following proportions of the individual sections in the total reactor volume have proven to be preferred:
• Reactor section 1 25 to 50%
• the reactor sections can advantageously be equipped with internals in order to improve the mixing of the reaction mixture.
• Suitable internals are known to the person skilled in the art, for example static mixing elements, such as gratings, distributor plates or sieve trays. Is particularly preferred it to equip the first reactor section with such internals, which are provided in particular in the upper half of the reactor section.
• the carboxylic acid and isobutene feedstocks are fed in liquid form into the first section of the reactor, in particular in the region of the bottom of the reactor.
• the feed can directly, e.g. B. via an immersion tube, but it is preferred to provide means which enable a uniform distribution and mixing of the feed materials. Such means are known to the person skilled in the art, for example distribution plates, perforated plates and tubes, nozzles etc.
• the isobutene is preferably fed in via an annular tube with a plurality of outlet openings.
• the carboxylic acid is preferably fed in via a nozzle, which brings about the mixing of a gas and a liquid and the mixing of the reactor contents. It is preferably arranged in the bottom of the reactor.
• Suitable nozzles are known to the person skilled in the art (jet nozzle, mixing nozzle, two-substance nozzle etc.) and z. B. in Ulimann's Encyclopedia of Industrial Chemistry, Vol. B4, 5th ED., 1992, p. 280. In particular when using such a nozzle, the flow in the first two reactor sections is turbulent and in the following reactor sections essentially laminar.
• a part of the reaction mixture can be removed from the first and / or second reactor section and returned to the relevant section. This ensures better mixing of the reaction mixture.
• the partial flow is expediently returned to the first reactor section via the above-mentioned mixing nozzle and / or to the second reactor section in the region of the opening in the partition wall via a further nozzle.
• the further nozzle can be a nozzle of the type mentioned above for the mixing nozzle.
• a conical nozzle is preferably used. It is preferably arranged in such a way that its outlet opening is located approximately at the level of the partition that separates the first from the second section separates. If desired, the partial stream taken in each case can be passed through a heat exchanger to control the temperature.
• the reaction mixture obtained is removed at the top of the reactor and fed to further workup. Unconverted, gaseous isobutene accumulates in the upper area of the reactor. This is returned to the first reactor section, preferably via the nozzle mentioned at the bottom of the first reactor section.
• the isobutene-containing gas stream coming from the reactor is preferably freed of inert gases such as air and butane by condensation of the isobutene.
• the isobutene is then fed in liquid form via the mixing nozzle or together with the fresh isobutene into the first reactor section.
• the catalyst is fed in as a mixture with the carboxylic acid, and fresh catalyst or recovered catalyst or a mixture thereof can be used.
• the overall reaction temperature is in the range of about 10 to 40 ° C. It is preferably controlled so that it is highest in the first reactor section.
• the reaction temperature in the first reactor section is preferably in the range from about 30 to 40 ° C.
• In the second section it is lower, preferably around 5 to 15 ° C.
• the temperature in the sections following the second section can be the same or different. It is generally not higher than in the second section, preferably it is lower, in particular around 3 to 10 ° C.
• the fourth section it is generally as high as in the third section or about 1 to 5 ° C lower.
• the temperature in the last reactor section is preferably in the range from about 10 to 25 ° C.
• the temperature distribution in a 4-section reactor is preferably as follows:
• the temperature in the 3rd and 4th section can be the same or different.
• the process according to the invention can be carried out with positive pressure, negative pressure or preferably without pressure or under slight positive pressure (100-300 mbar).
• the reaction mixture emerging from the reactor contains a high proportion of the desired ester. In addition, it contains unreacted feedstocks, catalyst, inhibitor, ester of catalyst acid and other minor by-products.
• the reaction mixture contains only very small amounts of isobutene oligomerization product, generally ⁇ 2% by weight, based on the reaction mixture.
• the reaction mixture is subjected to a further work-up in order to obtain pure ester.
• the workup is in no way restricted and can be carried out by any customary method for this purpose.
• the procedure is advantageously such that the catalyst is first separated off. This can be done by washing the reaction mixture one or more times with water and / or by neutralizing the catalyst with an aqueous alkali solution (for example sodium hydroxide solution, potassium hydroxide solution, aqueous sodium or potassium carbonate solution or bicarbonate solution).
• an aqueous alkali solution for example sodium hydroxide solution, potassium hydroxide solution, aqueous sodium or potassium carbonate solution or bicarbonate solution.
• the catalyst can be separated off by distillation of the reaction mixture, for example in a distillation unit comprising an evaporator, a column and a condenser.
• top product which essentially comprises the target ester, small amounts of carboxylic acid and low-boiling constituents (tert-butanol and diisoolefin), and a bottom product which comprises the catalyst, the majority of the unreacted carboxylic acid and the high-boiling components, e.g. B. polymeric (meth) acrylic compounds.
• the bottom product is generally at least partially returned to the reactor.
• the low boilers are separated off in a customary distillation unit comprising evaporator, column and condenser.
• the crude ester freed from the low boilers remains as the bottom product and is then subjected to pure distillation in the customary manner.
• the residue the pure distillation, mainly carboxylic acid and some ester, is returned to the first reaction section.
• the isobutene is used in liquid form, so that no energy-intensive evaporation of the isobutene is required;
• the reactor is technically simple, so that the investment costs are low;
• the reactor is low-maintenance due to its simple construction and the absence of moving parts, so that the operating costs are low;
• the process according to the invention can be carried out not only with isobutene. It is advantageous when using an isoolefin of the formula
• R 1 and R 2 are independently methyl or ethyl and R 3 is H, methyl or ethyl. This gives a tert-C 4 -C 8 alkyl ester of an aliphatic C 4 -C 4 carboxylic acid.
• the figure shows a schematic representation of an axial longitudinal section through the reactor according to the invention.
• the reactor 1 with a total volume of about 10 m 3 (diameter about 1.3 m) is divided into four sections R1, R2, R3, R4, which are separated from one another by partitions 2, 2 ', 2''. In the middle of each partition there is a round opening 3, 3 ', 3''(diameter up to about 5 cm) which allows the reaction mixture to pass into the next chamber.
• the first reactor section R1 is equipped in the upper half with a grating (not shown).
• Fresh isobutene is fed in in liquid form via line 5 in the area of the bottom 4 of the reactor 1 or of the reactor section R1 (500 l / h).
• the fresh isobutene is distributed through an annular tube 6, which is arranged symmetrically in the lower region of the reactor section R1 and has a plurality of outlet openings (not shown).
• a mixture is fed into the lower region of the reactor section R1, which consists of fresh acrylic acid 7 (430 1 / h), the sump 11 of the catalyst separation (1150 1 / h, acrylic acid content approx. 40 wt .-%), the bottom 12 of the pure distillation (320 1 / h, acrylic acid content approx.
• the fresh catalyst 13 (3.5 1 / h, sulfuric acid 98%)
• the back isobutene 14 consists of the reactor exhaust gas, the discharge 8 from the reactor section R1 (approx. 75 m 3 / h) and the gaseous re-isobutene 15 (92 m 3 / h) which is obtained in the distillation in the course of working up the reaction mixture obtained.
• the jet nozzle 9 sucks in the gaseous back isobutene 15 and the liquid back isobutene 14.
• the reaction mixture from the reactor R1 passes through the opening 3 (diameter approximately 3 cm) into the reactor section R2.
• part of the reaction mixture (4 m 3 / h) is discharged and passed through the heat exchanger 17 to remove the heat of reaction and returned to the reactor section R2 via a conical nozzle (not shown).
• the nozzle is arranged such that its outlet opening is located in the opening 3 approximately in the plane of the partition 2.
• the reaction temperature in R2 is adjusted to about 25 ° C in this way.
• the additional flow caused by the nozzle mentioned supports the flow of the reaction mixture from R1 to R2 and the contents of R2 are thoroughly mixed.
• the reaction mixture passes from R2 to R3 and from R3 to R4 via the openings 3 'and 3''(diameter 2 cm each).
• the heat dissipation in R3 and R4 takes place via internal lamella coolers (not shown), the temperature being set to 20 ° C in each case.
• the reaction mixture (2.4 m 3 / h) is discharged from the reactor section R4 via a liquid level control via line 18 and fed to further processing.
• the gas phase which forms above the liquid phase in the reactor section R4 is discharged at the top of the reactor and passed through a cooler 18 operated with brine in order to condense the isobutene contained in the exhaust gas and from the inert gases (2.5 m 3 / h, mainly butanes and air).
• the inert gases are disposed of via line 19 and the liquid isobutene is returned to the reactor section R1 via the nozzle 9.
• the reactor discharge essentially has the following composition:
• the reactor discharge is with the aid of a thin-layer evaporator (80 ° C., 60 mbar) into a distillate, which is mainly tert. Butyl acrylate, tert. Contains butyl acetate, butanol and acrylic acid, and a bottom product, which essentially contains acrylic acid, catalyst and phenothiazine and which is returned to the reactor.
• a thin-layer evaporator 80 ° C., 60 mbar
• 25 acrylate is stabilized with 15 ppm hydroquinone monomethyl ether, partly (about 50%) applied as reflux to the top of the column and partly discharged. The tert obtained in this way. Butyl acrylate has a purity of 99.9%.

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• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

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• 2000
  • 2000-07-28 DE DE10036959A patent/DE10036959A1/de not_active Withdrawn
• 2001
  • 2001-07-27 EP EP01958028A patent/EP1305275B1/de not_active Expired - Lifetime
  • 2001-07-27 WO PCT/EP2001/008710 patent/WO2002010109A1/de not_active Ceased
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