Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C231/00—Preparation of carboxylic acid amides
  • C07C231/02—Preparation of carboxylic acid amides from carboxylic acids or from esters, anhydrides, or halides thereof by reaction with ammonia or amines

Definitions

• the present invention relates to a process for the preparation of N, N-dimethylacetamide (DMAC) by continuous reaction of methyl acetate (MeOAc) with dimethylamine (DMA) in the presence of a basic catalyst.
• DMAC N, N-dimethylacetamide
• DMAC finds use as a polar solvent, e.g. for polymers and for gases, as stripper, extractant, catalyst and crystallization aid.
• polar solvent e.g. for polymers and for gases
• stripper extractant
• catalyst catalyst
• crystallization aid e.g. for polymers and for gases
• DMAC because of its high boiling temperature, is used for special binder-based coatings of polymers such as polymers. Polyamides and polyurethanes.
• DMAC is also used to make fibers and films and as a reaction medium. DMAC is used in the spinning of Spandex® fibers as an excipient and then at least partially recovered.
• DMAC can be prepared from acetic acid and dimethylamine, e.g. according to FR-A-1, 406,279.
• Carboxylic acid amides are also accessible by aminolysis of corresponding carboxylic acid esters, cf. e.g. .Organik ⁇ m ', VEB German publishing house of the sciences, 1963, pages 374-375.
• CA-A-1 073 467 and CA-A-1 073 468 (both General Electric Comp.) Describe the preparation of diols and N, N-dialkylamides by reaction of carboxylic acid diesters with dialkylamines.
• Example 1 a "20% methanol-methyl acetate azeotropic" for the reaction at 155 - 160 0 F (68.4 - 71, 2 0 C) is used.
• JP-A-02 160749 (Lion Akzo KK) relates, according to Patent Abstracts of Japan, the reaction of aliphatic Carbonklad with ammonia or an amine such as Mo nomethylamin, ethylenediamine, diethylenetriamine, in the presence of an "alkali catalyst” at 50 to 180 0 C, in particular 80 to 16O 0 C, and in the pressure range of atmospheric pressure to 9.81 bar (10 kg » cm 2» G).
• NaOMe sodium methoxide
• the present invention has for its object to provide an improved economical, selective, energy and resource-saving process for the preparation of N, N-dimethylacetamide (DMAC).
• DMAC N, N-dimethylacetamide
• the process should provide DMAC in high yield and space-time yield and in high purity (e.g., free or quasi-free of acetic acid, high color quality).
• a process for the preparation of N, N-dimethylacetamide (DMAC) by continuous reaction of methyl acetate (MeOAc) with dimethylamine (DMA) was found in the presence of a basic catalyst, characterized in that MeOAc as the methanolic solution used in the preparation of PolyTHF is obtained by transesterification of polyTHF diacetate with methanol as a byproduct.
• DMAC dimethylamine
• MeOAc methyl acetate
• Per mole of methyl acetate are preferably in the range of 0.2 to 2.0 mol, especially 0.5 to 1, 5 mol, very particularly 0.8 to 1, 2 mol, for example 0.9 to 1, 1 mol or 1, 0 to 1, 05 mol, dimethylamine (DMA) used.
• the DMA used preferably has a purity of ⁇ 99% by weight, in particular ⁇ 99.4% by weight, and is, for example, in the range from 99.5 to 99.8% by weight.
• the methanolic MeOAc solution preferably has a concentration in the range of 65 to 90 wt .-%, preferably 70 to 85 wt .-%, in particular 75 to 82 wt .-%, Me- OAc on.
• the methanolic MeOAc solution according to the invention is an appropriate by-product stream which is used in the production of polyTHF (polytetrahydrofuran), e.g. according to the two-stage BASF process according to EP-A-3112, DE-A-197 58 296 and / or DE-A-198 17 113, is used.
• polyTHF polytetrahydrofuran
• the methanolic MeOAc solution preferably has the following contents:
• MeOAc 65 to 90 wt .-%, preferably 70 to 85 wt .-%, in particular 75 to
• methanol 10 to 30 wt .-%, preferably 14.8 to 25 wt .-%, in particular 17.6 to 22 wt .-%,
• Dimethyl ether 0 to 2 wt .-%, preferably 0.1 to 1, 5 wt .-%, in particular 0.2 to 1, 2 wt .-%,
• THF 0 to 4 wt .-%, preferably 0.1 to 3.5 wt .-%, in particular 0.2 to
• 1, 5 wt .-%, and H 2 O 0 to 0.1 wt .-%, preferably 0 to 0.01 wt .-%, in particular 0 to
• the methanolic MeOAc solution consists of MeOAc, MeOH, dimethyl ether, THF and water in the amounts indicated above.
• the continuous reaction is preferably carried out at an absolute pressure in the range from 1 to 200 bar, preferably from 3 to 100 bar, in particular from 10 to 30 bar, very particularly from 12 to 25 bar, e.g. 15 to 20 bar, carried out.
• the reaction temperature is preferably in the range of 20 to 200 0 C 1 is preferably 60 to 140 0 C, particularly 80 to 12O 0 C, very especially 90 to 110 0 C, for example 95 to 105 0 C.
• Reactors used for the reaction according to the invention are, in particular, back-mixing reactors, such as, for example, stirred tank reactors or jet loop reactors.
• back-mixing reactors such as, for example, stirred tank reactors or jet loop reactors.
• VWZ residence time
• the reaction is particularly preferably carried out in a jet loop reactor.
• the jet loop reactor is preferably equipped with a plug-in tube and bottom nozzle.
• DMA is preferably added together with the catalyst through the pumped propulsion jet and the MeOAc through the jacket jet.
• the main reactor e.g. the jet loop reactor
• a post-reactor e.g. a flow tube or a cascaded residence time tank, downstream.
• the basic catalyst used in the process according to the invention is preferably an alkali metal hydroxide, alkaline earth metal hydroxide, alkali metal alcoholate, alkaline earth metal alcoholate, alkali metal carbonate, alkaline earth metal carbonate, alkali metal hydrogencarbonate, alkaline earth metal bicarbonate and / or an amine, in particular a tertiary amine.
• the alkali metal is Li, Na, K, Rb or Cs, especially Na or K.
• the alkaline earth metal is Be, Mg, Ca, Sr or Ba, in particular Mg or Ca.
• the alkoxide is preferably a especially methanolate.
• the particular aliphatic amine is preferably a C 3 . 12 -
• Alkylamine e.g. Triethylamine, tri-n-propylamine, tri-n-butylamine, dimethylethylamine, diethylmethylamine, N-methyl-piperidine, triethylenediamine (TEDA).
• Triethylamine tri-n-propylamine
• tri-n-butylamine dimethylethylamine
• diethylmethylamine diethylmethylamine
• N-methyl-piperidine triethylenediamine
• Very particularly preferred catalyst in the process according to the invention is sodium methoxide (NaOMe).
• the catalyst is homogeneous and / or suspended in the reaction mixture. Preference is given to using in a continuous process per mole of methyl acetate used in the range from 0.0002 to 0.09 mol, preferably from 0.002 to 0.05 mol, in particular from 0.003 to 0.02 mol, of the catalyst or of the catalyst mixture.
• the catalyst or the catalyst mixture is advantageously used as a solution and / or suspension in a solvent or suspending agent.
• Preferred solvents and / or suspending agents are water and alcohols (e.g., C 1-4 alcohols such as methanol, ethanol, n-propanol, n-butanol) or mixtures thereof.
• the catalyst or catalyst mixture is added to the o.g. preferred amounts are preferably used as 1 to 35 wt .-%, in particular 5 to 30 wt .-% solution or suspension.
• a catalyst NaOMe in the o.g. preferred amounts as methanolic solution, in particular as 1 to 35 wt .-% solution, especially as 25 to 30 wt .-% solution used.
• the reaction of MeOAc in the process of the invention is preferably in the presence of less than 1 wt .-%, particularly less than 0.5 wt .-%, especially in the range of 0 to 0.3 wt .-%, water, respectively based on the weight of the two feedstocks MeOAc and DMA (in total).
• the removal of the reaction heat of the reaction preferably takes place via an external heat exchanger.
• the vapor generated in the external heat exchanger e.g. 1, 5-bar steam, used in a synthesis plant for methylamines from methanol and ammonia.
• the liquid reactor discharge from the synthesis stage is in the range from 45 to 74.5% by weight, especially 50 to 70% by weight, DMAC, in the range from 25 to 45% by weight, especially 29 to 40 Wt .-%, methanol and a total of 0.5 to 6 wt .-%, especially 1 to 5 wt .-%, DMA, methyl acetate, catalyst (eg sodium methoxide), if necessary, Katalysatoratesstoffavantpensionsstoff and by-products.
• tetrahydrofuran (THF) and / or dimethyl ether may be such by-products.
• the liquid reactor discharge can be released directly into a bubble of a distillation column.
• the effluent is advantageously water or an aqueous or anhydrous protic acid such as sulfuric acid, methanesulfonic acid, carboxylic acid (eg Ci. 4 carboxylic acid), particularly phosphoric acid, preferably in an amount that a complete conversion of the basic catalyst used for the corresponding acid and the corresponding alkali metal , Alkaline earth metal or ammonium salt of the protonic acid ensured added. That is to say that the basic catalyst used and present in the reactor effluent is completely neutralized by reaction with H + .
• an aqueous or anhydrous protic acid such as sulfuric acid, methanesulfonic acid, carboxylic acid (eg Ci. 4 carboxylic acid), particularly phosphoric acid, preferably in an amount that a complete conversion of the basic catalyst used for the corresponding acid and the corresponding alkali metal , Alkaline earth metal or ammonium salt of the protonic acid ensured added. That is to say that the basic catalyst used and present in the reactor effluent is
• the organic product mixture is preferably separated from existing salts by evaporation (at normal pressure or in vacuo, e.g., in a reboiler), e.g. until a precipitating salt significantly reduces the heat exchanger performance and leads to clogging.
• the bubble for the reactor discharge is then preferably changed and the residue of the old bubble evaporated as far as possible.
• the precipitated solid salt residue can be dissolved in water and disposed of as a solution in a sewage treatment plant.
• the solids-removed and partially or totally condensed reactor effluent is worked up by distillation, e.g. in one, two, three, four or more, possibly interconnected, columns.
• a column A at preferably 0.8 to 1.2 bar of methanol and optionally other low boilers (DMA, water, THF, methyl acetate and the like) are separated off via the top.
• DMA low boilers
• a possibly aqueous methanol stream which may contain DMA, is enriched, e.g. advantageous for use in a methylamine synthesis plant (in particular for DMA production) is recycled.
• the bottom product of column A is fed to a column B.
• a column B At preferably 100-500 mbar abs. is here pure DMAC ( ⁇ 99.5 wt .-%, in particular ⁇ 99.7 wt .-%, especially ⁇ 99.8% by weight, for example in the range from ⁇ 99.9 to 99.99% by weight), preferably via a liquid side draw, which is preferably in the reinforcing part, separated off.
• the head effluent from column B containing DMAC (e.g., ⁇ 98 wt% DMAC, especially 98.5 to 99.5 wt% DMAC) is preferably recycled to column A.
• DMAC e.g., ⁇ 98 wt% DMAC, especially 98.5 to 99.5 wt% DMAC
• the bottom product of column B is separated again in a column C under normal pressure, the head discharge containing DMAC and methanol (eg about 94% by weight of DMAC and about 6% by weight of methanol) preferably also being recycled to column A. is and the bottom product of the column C (high boilers, DMAC and methanol added) for disposal, eg Combustion, passes.
• the third column C the amount of residue is significantly reduced.
• the distillative purification of DMAC can also be carried out according to one of the processes of the two German patent applications No. 102004030616.8 of 24.06.04 and DE-A-10 315 214 (both BASF AG).
• the process can advantageously also be carried out in a plant which was originally designed for the production of N, N-dimethylformamide (DMF) from carbon monoxide (CO) and DMA.
• DMF N, N-dimethylformamide
• the DMAC space-time yields are in the range of 0.1 to 0.85 kg DMAC / (liter reactor volume • hr), e.g. 0.2 to 0.5 kg DMAC / (liter reactor volume • h).
• the process according to the invention gives DMAC having a purity of ⁇ 99.5% by weight, in particular ⁇ 99.7% by weight, very particularly ⁇ 99.8% by weight, for example in the range of ⁇ 99.9 to 99, 99% by weight, (method and conditions for determination of purity see below), a water content ⁇ 200 ppm, for example in the range from 50 to 150 ppm, (according to DIN 51777), and a Pt / Co color number ⁇ 10, especially ⁇ 8, for example in the range from 1 to 6, (according to DIN ISO 6271).
• the acid content (calculated as acetic acid) of the DMAC is in particular ⁇ 80 ppm, very particularly ⁇ 70 ppm, for example in the range from 5 to 60 ppm, (according to DIN 53402).
• the reaction took place in a loop reactor with an average residence time (VWZ) of 1 h and sodium methoxide (0.48 g / h) in methanolic solution (30% strength by weight) as homogeneous catalyst.
• VWZ average residence time
• sodium methoxide (0.48 g / h) in methanolic solution (30% strength by weight) as homogeneous catalyst.
• the heat was removed via an external heat exchanger.
• the energy dissipated in the external heat exchanger can generate 1, 5-bar steam.
• the liquid effluent from the synthesis step consisted of 57.7% by weight of DMAC, 34.2% by weight of methanol, 5.0% by weight of methyl acetate and a total of 3.1% by weight of DMA, tetrahydrofuran, sodium methoxide and by-products ,
• Example 3 All settings from example 1 have been adopted. However, the water content of the feed stream was 550 ppm. After a short time it came in the reactor by precipitating sodium acetate to blockages and the experiment had to be stopped. Example 3
• the reaction took place in a loop reactor with an average VWZ of 1 h and sodium methoxide (0.56 g / h) in methanolic solution (30% by weight) as a homogeneous catalyst.
• the heat was removed via an external heat exchanger.
• the energy dissipated in the external heat exchanger can generate 1, 5-bar steam.
• the liquid discharge from the synthesis stage consisted of 53.9 wt .-% DMAC, 36.3 wt .-% methanol, 3.9 wt .-% of methyl acetate and a total of 5.9 wt .-% DMA, tetrahydrofuran, sodium methoxide and by-products ,
• This discharge was conveyed in a straight pass through a tubular reactor at 120 0 C, 20 bar and a mean VWZ of 1 h.
• the effluent consisted of 58.3% by weight of DMAC, 37.3% by weight of methanol, 1.1% by weight of methyl acetate and a total of 3.3% by weight of DMA, tetrahydrofuran, sodium methoxide and by-products.
• Example 3 To a reaction effluent according to Example 3 was continuously 10 wt .-% of excess stoichiometric added to the catalyst H 2 O to decompose the sodium methoxide. In a continuous exhaust steam at 135 ° C, all volatile ingredients (1, 8 kg / h) were distilled off. The accumulated within 20 hours and evaporated to dryness salt-like residue (245 g) in the bottom of the bladder was dissolved in 1, 5 kg of H 2 O and removed without residue from the bladder to be treated wastewater (bbA).
• a reaction effluent according to Example 3 was continuously mixed with 85% phosphoric acid for the stoichiometric formation of Na 2 HPO 4.
• 400 g / h of the condensed mixture were fed continuously to a distillation column and at a bottom temperature of 175 ° C, a high-boiling current (218 g / h) with 99.2 wt .-% DMAC and 0 , 8 wt .-% by-products deducted.
• this stream was further worked up to obtain 198 g / h DMAC with a purity of 99.9% from a side draw.

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• 2004
  • 2004-12-06 DE DE102004058886A patent/DE102004058886A1/de not_active Withdrawn
• 2005
  • 2005-12-03 WO PCT/EP2005/012982 patent/WO2006061159A1/de not_active Ceased
  • 2005-12-03 ES ES05815808.0T patent/ES2472271T3/es not_active Expired - Lifetime
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  • 2005-12-03 US US11/720,774 patent/US20080207949A1/en not_active Abandoned
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