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. , Organikum ', 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 reacting carboxylic acid diesters with dialkylamines.
• Example 1 a "20% methanol-methyl acetate azeotropic" for the reaction at 155 - 16O 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 160 0 C, and in the pressure range of normal pressure to 9.81 bar (10 kg »cm 2 -G).
• NaOMe sodium methoxide
• German patent applications Nos. 102004030616.8 of 24.06.04 and DE-A-10 315 214 of BASF AG relate to processes for the purification of DMAC.
• 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).
• DMAC N, N-dimethylacetamide
• MeOAc methyl acetate
• DMA dimethylamine
• MeOAc as a methanolic solution and per mole of MeOAc in the range from 0.0002 to 0.09 mol of catalyst is used and the reaction is carried out at a temperature in the range of 90 to 14O 0 C and at an absolute pressure in the range of 10 to 30 bar.
• 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 .-%, particularly preferably 70 to 85 wt .-%, in particular 75 to 82 wt .-%, MeOAc on.
• an appropriate by-product stream which is used in the production of polyTHF polytetrahydrofuran
• 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% by weight, preferably 14.8 to 25% by weight, in particular 17.6 to 22% by weight,
• Dimethyl ether 0 to 2 wt .-%, preferably 0.1 to 1, 5 wt .-%, in particular 0.2 to
• THF 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 carried out at an absolute pressure in the range of 10 to 30 bar, especially 12 to 25 bar, e.g. 15 to 20 bar, carried out.
• the reaction temperature is in the range of 90 to 14O 0 C, preferably 95-130 0 C 1, in particular from 97 to 12O 0 C, especially 98-110 0 C, for example 100 to 105 0 C.
• 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 is preferably an alkali metal hydroxide, alkaline earth metal hydroxide, alkali metal alcoholate, alkaline earth metal alcoholate,
• the alkali metal is Li, Na, K, Rb or Cs, especially Na or
• the alkaline earth metal is Be, Mg, Ca, Sr or Ba, in particular Mg or Ca.
• the alkoxide is preferably a d- 4 alcoholate, in particular thanolat metal.
• the particular aliphatic amine is preferably a C 3-12
• Alkylamine e.g. Triethylamine, tri-n-propylamine, tri-n-butylamine, dimethylethylamine,
• 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.
• 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 (eg 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, catalyst solvent / -suspensionsstoff and by-products.
• 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, catalyst solvent / -suspensionsstoff 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 turnover of the basic catalyst used for the corresponding acid and the corresponding Alkali metal, alkaline earth metal or ammonium salt of the protonic acid ensures 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
• 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 precipitated salt significantly reduces the heat exchanger performance and leads to encrustations.
• 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 preferably 0.8 to 1.2 bar, of methanol and optionally other low boilers (DMA, water, THF, methyl acetate, and the like) are removed overhead.
• DMA low boilers
• a possibly aqueous methanol stream which may contain DMA, enriched, which is for example advantageously recycled for use in a methylamine synthesis plant (in particular for DMA production).
• the bottom product of column A is fed to a column B.
• Pure DMAC ⁇ 99.5% by weight, in particular> 99.7% by weight, very particularly preferably> 99.8% by weight, eg in the range of ⁇ 99.9 to 99.99% by weight
• % preferably via a liquid side draw, which is preferably in the reinforcing part, separated.
• the head effluent of column B containing DMAC (e.g.> 98 wt% DMAC, especially 98.5 to 99.5 wt% DMAC) is preferably recycled to column A.
• 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 significantly reduces the amount of residue.
• 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 • h), eg 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, eg in the range from 50 to 150 ppm, (according to DIN 51777), and a Pt / Co color number ⁇ 10, especially ⁇ 8, eg 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, more particularly ⁇ 70 ppm, e.g. in the range of 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, blockages occurred in the reactor due to precipitated sodium acetate 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 12O 0 C, 20 bar and a mean VWZ of 1 h.
• the effluent consisted of 58.3 wt% DMAC, 37.3 wt% methanol, 1.1 wt% methyl acetate and a total of 3.3 wt% DMA, tetrahydrofuran, sodium methoxide and by-products.
• a reaction effluent according to Example 3 was continuously mixed with 85% strength 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 (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 99.9% purity from a side draw.

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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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• 2004
  • 2004-12-06 DE DE102004058887A patent/DE102004058887A1/de not_active Withdrawn
• 2005
  • 2005-12-03 EP EP05814359A patent/EP1828101A1/de not_active Withdrawn
  • 2005-12-03 CN CNA2005800417004A patent/CN101072747A/zh active Pending
  • 2005-12-03 JP JP2007544785A patent/JP2008522996A/ja not_active Withdrawn
  • 2005-12-03 WO PCT/EP2005/012960 patent/WO2006061153A1/de active Application Filing
  • 2005-12-03 US US11/720,791 patent/US20080103336A1/en not_active Abandoned

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