Background technology
Dimethyl formamide (be called for short: DMF) and toluene be important industrial chemicals and solvent, be widely used in pharmacy and pesticide intermediate building-up process, in pharmacy and pesticide intermediate building-up process, adopt above-mentioned solvent, easily form the mixing solutions of sodium salt, DMF, toluene and water.Mainly contain physico-chemical process, biochemical process and chemical hydrolysis for recovery and the treatment process containing sodium salt, DMF and toluene in waste water both at home and abroad at present.Adopt biochemical process and chemical hydrolysis all can destroy DMF and toluene structure.The biochemical process treatment time is long, degraded is not thorough, and in addition, DMF can make microorganism poisoning, and biological treatment is caused to very big impact; Chemical method does not reach the object that reclaims DMF and toluene, easily causes secondary pollution.
As taked effective separation method, not only can reclaim DMF and toluene to above-mentioned mixed solution, reach the object of processing waste water simultaneously, reduce treating processes cost.Adopt low boiling point solvent as CH
2cl
2, chloroform, dichlorobenzene, benzene, pimelinketone or methyl-phenoxide etc. carry out liquid-liquid extraction as extraction agent, recyclable DMF, but need further to separate containing the mixed solvent of extraction agent after extraction, reaches 1~3% containing organic solvent in water after separating, and easily causes secondary pollution.For high density DMF and toluene (nearly 100 g/L) waste water, distillation method separate DMF, toluene and water, the DMF of recovery and toluene can be back to production, but separate after waste water COD reach 40000PPM, process energy consumption is higher; If DMF and toluene mass concentration are lower than 50 g/L in waste water, this method cost recovery will increase considerably, very uneconomical.Absorption method has the features such as technical process is short, simple to operate, recovering effect is good, but mixing organism after absorption needs further to process, and adsorbent reactivation needs high energy consumption.
Summary of the invention
The object of the present invention is to provide a kind of azeotropic extraction rectifying and the liquid liquid stratified set composition technique from sodium salt, DMF, toluene and water mixed solution, compared with traditional technology, it is fairly simple that the present invention has processing step, through flash liberation, content, the yield of DMF and toluene are higher, and after separating, the COD of water is lower than 800PPM; Extraction agent used is convenient to regeneration and recycle, and sepn process energy consumption is low.
For achieving the above object, the present invention adopts following technical scheme:
Azeotropic extraction rectifying and liquid liquid stratified set composition, from a method for sodium salt-DMF-toluene-water mixed solution, comprise the following steps:
1) after raw material sodium salt, DMF, toluene and water mixed solution preheating, again by the desalination of desalination evaporating pot, mixing solutions after desalination adds azeotropic extraction rectifying tower from the middle and lower part of azeotropic extraction rectifying tower, modification extraction agent is added in azeotropic extraction rectifying tower by the middle and upper part of azeotropic extraction rectifying tower, and described modification extraction solvent is the mixed solvent of tetramethylene sulfone and dioctyl phthalate (DOP); Control tower top, column bottom temperature, mixing solutions is at azeotropic extraction rectifying tower through azeotropic extraction rectifying, and tower top obtains toluene and water mixing gas, obtains the mixture of DMF and modification extraction agent at the bottom of tower;
2) toluene and water mixing gas, after condensation, are divided into toluene layer and water layer, and toluene layer is containing the toluene of more than 99% (mass content, below content be mass content), and water layer toluene level is lower than 0.08%; Toluene is partly refluxed to azeotropic extraction rectifying tower;
3) mixture of DMF and modification extraction agent is through solvent reclamation recycle column rectification process, and solvent reclamation recycle column tower top obtains 99.9% DMF, at the bottom of solvent reclamation recycle column tower, obtains modification extraction agent, is circulated to azeotropic extraction rectifying tower.
The inventive method has been set up a kind of azeotropic extraction rectificating method, and traditional azeotropic distillation and extracting rectifying effective integration, in same device, are realized to separating of DMF, toluene and water on same azeotropic extraction rectifying tower, has simplified the technological process of production.
In described method, the temperature at the bottom of tower top and the tower of azeotropic extraction rectifying tower is respectively 83.8~84.5 ℃ and 95.7~97.5 ℃.
In described method, the mass ratio of raw material and modification extraction agent is 1:0.4~1.0.
In described method, described modification extraction solvent is the sulfolane solution containing 15~20% dioctyl phthalate (DOP)s.
In described method, mixing solutions and azeotropic extractive distillation column overhead vapours carry out heat exchange and carry out preheating.
Azeotropic extraction rectifying of the present invention and liquid liquid stratified set composition are from sodium salt, DMF, the method of toluene and water mixed solution, concrete steps are as follows: sodium salt, DMF, toluene and water mixed solution are 1. through azeotropic extraction rectifying tower tower top steam preheating, again by after the desalination of desalination evaporating pot, added in azeotropic extraction rectifying tower by the middle and lower part of azeotropic extraction rectifying tower, azeotropic extraction rectifying tower tower top, column bottom temperature is respectively 83.8~84.5 ℃ and 95.7~97.5 ℃, 6. modification extraction agent (adds 15-20wt% dioctyl phthalate (DOP)) in the upper position charging of azeotropic extraction rectifying tower in tetramethylene sulfone, after azeotropic distillation and extracting rectifying, 3. azeotropic extraction rectifying tower tower top is the mixing gas of toluene and water, after raw material condensation (with the 1. heat exchange of charging mixing solutions) and cryogenic condensation, ℃ (raw material condensation effectively utilizes the heat of azeotropic extraction rectifying tower tower top gas in fluid temperature≤20, cryogenic condensation guarantees that tower top gas is condensed into liquid), be divided into toluene layer 4. with water layer 5., 4. toluene layer is 99.5% above toluene, 5. water layer is more than 99.9% water (toluene is lower than 0.08%), it at the bottom of azeotropic extraction rectifying tower, is 8. the mixed solution of modification extraction agent and DMF, mixed solution is 8. through solvent reclamation recycle column rectification process, 7. solvent reclamation circulation tower top distillates cut is more than 99.9% DMF solution, and at the bottom of tower, discharging is that modification extraction agent is circulated to azeotropic extraction rectifying tower, recycles.
The preferred processing condition of described sepn process are as follows: in sepn process, each tower reactor, tower top temperature control, reflux ratio, feed entrance point and stage number are shown in Table 1.
Table 1 sepn process processing condition
The present invention adopts azeotropic extraction rectifying and the liquid liquid stratified set composition technique from sodium salt-DMF-toluene-water mixed solution, by traditional azeotropic distillation and extracting rectifying effective integration in same device, on same azeotropic extraction rectifying tower, realize separating of DMF, toluene and water, simplified the technological process of production.Compared with traditional technology, the inventive method, by traditional azeotropic distillation and extracting rectifying effective integration, adopts desalter to carry out preheating and desalination, realizes polycomponent and separate in azeotropic extraction rectifying tower, and technological process is simple; Adopt azeotropic extraction rectifying tower tower top steam to raw material preheating, effectively utilize heat, reduce energy consumption; Adopt modification extraction solvent, significantly reduce the fusing point of extraction agent, while avoiding winter environment temperature low, on the impact of azeotropic extraction rectifying.Described method stock liquid, through azeotropic extraction rectifying and the primary treatment of liquid liquid stratified set apparatus for converting, once can obtain more than 99.5% toluene and 99.9% above DMF, more than one time yield all reaches 98 %, after separating, in water, contains toluene lower than 0.08%.
Embodiment
Azeotropic extraction rectifying of the present invention and liquid liquid stratified set composition are from the method for sodium salt, DMF, toluene and water mixed solution, tripping device and technical process are with reference to Fig. 1, and wherein 1 is azeotropic extraction rectifying tower, and 2 is desalter, 3 is azeotropic extraction rectifying tower well heater, 4 is feed preheater, and 5 is subcooling condenser, and 6 is venting hole, 7 is liquid liquid layering tank, 8 is condenser, and 9 is solvent reclamation recycle column, and 10 is well heater.
Adopting sodium salt, DMF, toluene and the water mixed solution that certain company provides is raw material, operating under normal pressure of azeotropic extraction rectifying tower carried out, tower internal diameter is 50mm, the Stainless Steel Helices of in-built φ 3*3 θ type, through measuring by standards system, this height equivalent to one theoretical plate HETP=27mm, tower reactor heats with electric mantle, raw material, modification extractant feed and discharging are all with glass rotameter metering, and azeotropic extraction rectifying tower and solvent reclamation recycle column all adopt external reflux.
Sodium salt, DMF, toluene and water mixed solution 1. in feed preheater 4 through the 1 overhead vapours preheating of azeotropic extraction rectifying tower, and then by 2 desalinations of desalination evaporating pot, added in azeotropic extraction rectifying tower 1 by the middle and lower part of azeotropic extraction rectifying tower 1, azeotropic extraction rectifying tower 1 tower top, column bottom temperature is respectively 83.8~84.5 ℃ and 95.7~97.5 ℃, 6. modification extraction agent (adds 15-20% dioctyl phthalate (DOP)) in the upper position charging of azeotropic extraction rectifying tower 1 in tetramethylene sulfone, 1. raw material is 1:0.4~1.0 with the ratio of modification extraction agent, 3. azeotropic extraction rectifying tower 1 tower top material is the mixing gas of toluene and water, after feed preheater 4 and subcooling condenser 5 raw material condensations and cryogenic condensation, tower top gas is condensed into liquid, fluid temperature≤20 ℃, in liquid liquid layering tank 7, be divided into toluene layer 4. with water layer 5., 4. toluene layer is 99.5% above toluene, 5. water layer is 99.9% water (toluene is lower than 0.08%), 8. azeotropic extraction rectifying tower 1 materials at bottom of tower is the mixed solution of modification extraction agent and DMF, tower reactor mixed solution is sent into solvent reclamation recycle column 9, process through solvent reclamation recycle column 9,7. solvent reclamation recycle column 9 tower tops distillate cut is more than 99.9% DMF solution, materials at bottom of tower is modification extraction agent, be circulated to azeotropic extraction rectifying tower 1, recycle.
The processing condition of sepn process: in sepn process, the control of each tower reactor temperature, reflux ratio, feed entrance point and stage number are shown in Table 1.
Analyze through HP chromatographic instrument, raw material and each fractions consisting detailed results are shown in Table 2.
The rectifying of table 2 azeotropic extraction and liquid liquid stratified set composition are from the separating resulting of sodium salt, DMF, toluene and water mixed solution