Background technology
There are azeotrope in methyl alcohol and methylcarbonate (DMC), and (azeotropic point is 63 ℃, and azeotrope consists of CH
3OH 70%, and DMC 30% (mass) can't obtain pure product with common rectificating method.Existing isolation technique mainly contains two kinds, and a kind of is extracting rectifying, and a kind of is azeotropic distillation.These two kinds of separation method solvent cycle amounts are all very big, and energy consumption is higher.
United States Patent (USP) 3,963,586 have disclosed the technology of separating dimethyl carbonate from methylcarbonate, first alcohol and water.Water is put into extractive distillation column overhead by weight at least 10: 1, and methyl alcohol, water and a spot of methylcarbonate go out from tower bottom flow.Methylcarbonate, water and a spot of methyl alcohol are housed in the cat head container, are divided into the bottom organic phase after the condensation cooling, contain a large amount of methylcarbonates, a spot of water and methyl alcohol; Upper aqueous phase contains a large amount of water, the methyl alcohol of a certain amount of methylcarbonate and trace.Organic phase needs further to separate the pure methylcarbonate that arrives of ability, and a large amount of aqueous solvent of aqueous phase need reclaim.The defective of this technology maximum need to be the aqueous solvent of big cycle volume, inevitably can consume a large amount of energy consumptions and volume; Secondly, water is narrower as its extraction scope of solvent, has certain restricted.
United States Patent (USP) 5,338,878 use the technology of two kinds of separated from solvent alkyl carbonates and alkanol.First kind of solvent boiling point under a normal atmosphere is 50~450 °F, solvent can be one or more low polarity hydro carbons, comprise the fluidized catalytic cracking petroleum naphtha, coking naphtha, weight direct current petroleum naphtha, catalytic reforming products such as hydrocracking petroleum naphtha, alkylide and isomer thereof, extraction liquid needn't separate.Alkyl in the material carbon acid alkyl ester is the alkyl of 1~9 carbon atom, and more suitable is diethyl carbonate; Second kind of solvent is water, and the add-on of aqueous solvent and the ratio of raw material are 3: 1~5: 1, and alkanol is the alkyl alcohol of 1~9 carbon atom, and more suitable is a kind of mixture, as methyl alcohol, and ether, the mixture of Virahol and acetone.The purpose product is to obtain a kind of oxygenatedchemicals as Fuel Petroleum.The purpose product of this technology only is the oxygenatedchemicals as Fuel Petroleum, and the scope of application is very narrow.
In sum, prior art is in industrial applications or solvent load is too big, and energy consumption and cost of equipment height lack economic worth; Solvent there be to a certain degree restricted; The separating technology purpose product specific aim that is adopted is stronger.In addition, above-mentioned separating technology has a common ground: solvent extraction and distillation are carried out in same extraction distillation column, need take into account favourable extraction temperature and favourable distillation temperature, and both are competing, and operation easier is bigger.
In view of the above shortcoming of prior art, the objective of the invention is to study a kind of economic and practical separation method, so that better realize CH
3The separation of OH-DMC azeotrope.
Embodiment
Below in conjunction with accompanying drawing technology of the present invention is described in further detail.
Extraction system of the present invention adopts two kinds of solvents that incompatibility is immiscible simultaneously, and a kind of is polar solvent, water preferably, a kind of is non-polar solvent, and boiling point is 45~100 ℃ hydro carbons or a hydrocarbon mixture, preferably alkane or naphthenic hydrocarbon or their mixture.A kind of novel process that the present invention created is liquid-liquid extraction, azeotropic distillation and extracting rectifying bonded separating technology, and process frame chart and technical process are respectively as shown in Figure 1 and Figure 4.The major equipment of this technical process is: the reboiler 6,7 of condenser 5, extractor 1, quantizer 2, azeotropy rectification column 3 (finishing column), extractive distillation column 4 (water tower) and two towers.The varsol 10 that contains the stock liquid 9 of DMC, first alcohol and water, the material steam phlegma that returns as the water 11 of extraction solvent, by condenser 5 and small amount of supplemental is all sent into the top of extractor 1.The overhead vapours 14,15 of finishing column 3 and water tower 4 enters the bottom of extractor 1.Extractor 1 top is drawn steam and is sent into condenser 5, and extractor 1 bottom is drawn liquid and sent into quantizer 2.The light phase 12 of quantizer 2 (rich hydrocarbon phase) enters the finishing column top, obtains DMC product 17 at the bottom of the tower.The heavy phase 13 (water-rich phase) of quantizer enters the water top of tower, and the binary solution 16 of drawing the first alcohol and water at the bottom of the tower enters methanol distillation column, methanol distillation column recovered overhead methyl alcohol, and the water part at the bottom of the tower is returned extractor as solvent 11, and a part gives off system.By the heavy phase 13 of quantizer 2 or gently 12 draw a small gangs of logistics and go out system mutually, to avoid of the gathering of light constituents such as methyl-formiate and methyl acetate at extractor 1, quantizer 2.
Separate raw materials involved in the present invention is the mixture of methylcarbonate (DMC), first alcohol and water, also contains a spot of methyl-formiate and methyl acetate and other trace impurities in mixture.DMC content is 10~90% (mass ratioes) in the raw material, is preferably 20~40%; Methanol content is 10~90% in the raw material; Water generally accounts for 1~20% of raw material, is preferably 1~10%.Separate raw materials involved in the present invention is the mixture of methylcarbonate (DMC), first alcohol and water, also contains a spot of methyl-formiate and methyl acetate and other trace impurities in mixture.DMC content is 10~90% in the raw material, is preferably 20~40%; Methanol content is 10~90% in the raw material; Water generally accounts for 1~20% of raw material, is preferably 1~10%.
Most typical in the existing separating technology is water extractive distillation technology.Its work block diagram and technical process are respectively as shown in Figures 2 and 3.The mixture of material carbon dimethyl phthalate, methyl alcohol, water enters from the middle part of water extraction distillation column 19, aqueous solvent 33 sprays into from cat head after being preheating to about 80 ℃, raw material and aqueous solvent adverse current are carried out vapour-liquid, liquid-liquid mass transfer and heat transfer process, add heat by reboiler 22 controls.Extraction phase 28 (about 85% water and 15% methyl alcohol) is drawn by tower bottom, goes methanol distillation column to reclaim methyl alcohol and aqueous solvent, and solvent water circulation is used.Extracting phase 27 (a large amount of methylcarbonates, water and a spot of methyl alcohol) is drawn by cat head with vapor form, enters quantizer 18 after the condensation cooling.Light 29 (methylcarbonate, water and the methyl alcohol) mutually of quantizer are back to the middle part opening for feed of extraction distillation column 19.Quantizer heavy phase 30 (about 90% methylcarbonate, a spot of water and methyl alcohol) enters finished product DMC rectifying tower 20 tops, tower bottom 32 extraction product DMC, and overhead vapours 31 enters quantizer 18 after the condensation cooling.Among the figure, 23 is the reboiler of extractive distillation column, and 24 is the product condenser, and 25 is the aqueous solvent preheater, and 26 is raw material.
Technology of the present invention and existing processes (extractive distillation is compared as water, has tangible advantage:
1. existing separating technology (as water extractive distillation technology) has a common ground: solvent extraction and distillation are carried out in same extraction distillation column 19, need take into account favourable extraction temperature and favourable distillation temperature, and both are competing, and operation easier is bigger.And technical process of the present invention is that liquid-liquid extraction, azeotropic distillation and extracting rectifying are carried out in extractor 1, quantizer 2, extractive distillation column 4 (water tower) and azeotropy rectification column 3 (finishing column) respectively, and with its separating technology that organically combines.Easy and simple to handle, easy to control, separating effect is remarkable.Product (DMC) purity can reach 99.9%.
2. existing separating technology (as water extractive distillation technology) needs a large amount of solvents, is in a ratio of 10: 1 as the add-on and the raw material of aqueous solvent, is preferably 5: 1.So a large amount of aqueous solvent 33 recycles needs to consume a large amount of heats, and a large amount of aqueous solvent needs to reclaim, and can consume lot of energy, needs big volumetrical equipment simultaneously.Inevitably cause the energy consumption height, the unit equipment operation efficiency is low.Secondly, water is narrower as its extraction scope of solvent, has certain restricted.And the solvent requirement is little in the technical process of the present invention, and the adding 10 and the raw material of varsol are in a ratio of 0.25~0.6: 1; The consumption and the raw material of aqueous solvent 11 are in a ratio of 0.25~0.5: 1, and aqueous solvent comes from the Methanol Recovery tower bottom waste water in the flow process, do not need to add.Whole flow process solvent cycle is used, and internal circulating load is little, does not need heating or cooling.Therefore energy consumption is low, unit equipment operation efficiency height.
3. existing separating technology (as water extractive distillation technology), water extraction distillation column 19 and finished product rectifying tower 20 all need overhead condensation water cooler 21, and in the technical process of the present invention, extractive distillation column 4 (water tower) and azeotropy rectification column 3 (finishing column) do not need overhead condenser.Overhead vapours directly enters extractor 1 bottom, and bubbling passes liquid layer and forms the intensive turbulence, carries out vapour-liquid, liquid-liquid mass transfer and heat transfer.The technology of innovation has reduced energy consumption greatly.
4. existing separating technology (as water extractive distillation technology), water is narrower as its extraction scope of solvent, and operation easier is big, less stable.Behind water extraction methyl alcohol, extracting phase 27 (water extractive distillation cat head steam) enters with finished product rectifying tower top steam 31 and carries out layering in the quantizer 18, methanol content in the heavy phase 30 (organic phase) of quantizer 18>10% (mass), finished product rectifying tower 20 inferior separating effect, DMC purity is low, recovery per pass is low.And in the technical process of the present invention, the liquid-liquid extraction operating restraint is wide, and effect of extracting is good, and rich hydrocarbon phase 12 and water-rich phase 13 carry out azeotropic distillation and extracting rectifying respectively, good separating effect, DMC purity height.
In implementing, reality adopt the middle part that the extractor of a carry potential overflow pipe gas distribution grid is arranged.The grid distributor form can be sieve plate, floating valve tray or other rectifiying plate.Enter under the gas slave plate, enter on the liquid slave plate.The gas bubbling passes liquid layer and forms the intensive turbulence, carries out vapour-liquid, liquid-liquid mass transfer and heat transfer process.Drawn by the extractor top through the gas of this process, liquid is drawn at the bottom of by extractor.
The solvent strength that quantizer is drawn in the liquid in the technical process of the present invention need be controlled by entering the extractor quantity of solvent.Gently middle mutually hydrocarbon content is 25~65% (mass ratioes), is preferably 40~55%; Water-content is 25~60% in the heavy phase, is preferably 35~50%.The quantizer working pressure is a normal pressure, 15~70 ℃ preferably 20~45 ℃ of service temperatures.
Finishing column of the present invention can be a packing tower, also can be tray column.Plate is several 10~40, and preferably 18~28.Add the DMC quality product of drawing at the bottom of the heat control tower by reboiler.DMC purity can reach 99.9%.Working pressure is normal pressure or low pressure, service temperature: cat head is 60~80 ℃, and the tower still is 94~116 ℃.
Water tower of the present invention can be a packing tower, also can be tray column.Plate is several 10~40, and preferably 18~28.Add the residual volume of DMC and alkane in the methyl alcohol of drawing at the bottom of the heat control tower, the water mixture, DMC residual volume<1%, alkane residual volume trace by reboiler.Working pressure is normal pressure or low pressure, service temperature: cat head is 70~96 ℃, and the tower still is 86~111 ℃.
This technical process is in long-term the driving, enter micro-methyl-formiate and the methyl acetate that the feed liquid of system brings into and can be gathered in extractor, quantizer and cat head, the influence operation, can draw a small amount of material continuously or off and on by the light phase or the heavy phase (preferably heavy phase) of quantizer, also can remove light constituent in advance, with Control of Impurities on the level that does not influence operation.
Embodiment 1-3:
Test is carried out in two rectifying tower, an extractor and a quantizer.Rectifying tower is that tower diameter is 1200mm, and filler (stainless steel ripple filler) height is the Stainless Steel Helices tower of 18000mm.
The stock liquid 9 (containing a spot of methyl-formiate and methyl acetate) that contains DMC, first alcohol and water with from water rectifying tower 4 cat head materials 15, product rectifying tower 3 cat head materials 14 and methanol distillation column still material 11 (being mainly water) and replenish a spot of second kind of solvent normal hexane 10 (boiling point is 68.7 ℃, water-soluble hardly) enter extractor 1 together, extractor adds second kind of an amount of solvent normal hexane for 1 li in advance, carries out vapour-liquid, liquid-liquid mass transfer and heat transfer.Gas through this process is drawn by extractor 1 top, and liquid is drawn by extractor 1 bottom.Enter quantizer 2 then, the light phase 12 of quantizer 2 (rich alkane phase) enters finishing column 3 tops, finishing column 3 bottom side line extraction product DMC17, purity>99.9%.The heavy phase 13 (water-rich phase) of quantizer 1 enters water tower 4 tops, draws the binary solution 16 of first alcohol and water at the bottom of the tower.The material of drawing at the bottom of the tower enters methanol distillation column, and methanol distillation column reclaims methyl alcohol, and the water part at the bottom of the tower is returned extractor 1 as solvent 11, and a part gives off system.Whole flow process is a normal pressure or low voltage operated.
Test conditions and the results are shown in Figure 5, the subordinate list of Fig. 6, Fig. 7.
Embodiment 4-6:
Whole process flow is with embodiment 1-3, and different is that the non-polar solvent that embodiment 4-6 uses is respectively hexanaphthene, pentamethylene, normal heptane, and its boiling point is respectively 80.7 ℃, 49.2 ℃, 98.4 ℃, and its common ground is water insoluble.
Test conditions and the results are shown in Figure 8, the listed subordinate list of Fig. 9, Figure 10.
Adopt the technology mode of this patent invention, well methyl alcohol is separated with the azeotrope of DMC, the DMC purity of acquisition can reach more than 99.90%, DMC total recovery>99%.This flow operations is good, operating restraint is wide, can both obtain good separating effect in the condition and range of broad.