The apparatus and method of intermittent azeotropic rectifying method purifying formic acid solution
Technical field
The present invention relates to a kind of apparatus and method of intermittent azeotropic rectifying method purifying formic acid solution, be specially and adopt the heterogeneous azeotropic rectification method that 10% formic acid weak solution is purified to be the higher concentration formic acid of 80-85%.
Technical background
Formic acid, the popular name formic acid is the simplest aliphatic acid, is important Organic Chemicals, be widely used in agricultural chemicals, leather, weaving, printing and dyeing, medicine and rubber industry etc., can also produce all kinds of solvents, plasticizer, rubber coagulating agent, animal feed additive and new technology insulin synthesis etc.In the acid treatment process of the production of medicine and spices and textile and leather, have a large amount of low concentration formic acid solutions and produce no actual application value.Low concentration formic acid reclaimed and enrichment (w%>85%) in addition, both can reduce environmental pollution, can create considerable economic value again.Formic acid can be pressed the miscible and formation constant boiling mixture (w of arbitrary proportion with water
Water%=22%), can't obtain the formic acid solution of high concentration with the method for conventional distillation.
In the past, the existing bibliographical information of the method for purifying formic acid.Be reported in the new entrainer of adding in the water-containing formic acid as BP in 1948, the weak point of these class methods is: entrainer propyl formate, iso-butyl formate etc. generally need prepare from anhydrous formic acid, these entrainers are easy to hydrolysis simultaneously, in still-process, be subjected to pyrohydrolysis to generate formic acid and propyl alcohol or butanols, thereby separation can not be proceeded.As Chinese patent CN1063483 report in 1992, adopt the additive thionyl chloride, make itself and aqueous formic acid react dehydration, vacuum distillation then, but, can cause certain pollution and in industrializing implementation, can bring higher cost, so seldom adopt environment because technology is complicated.Chinese bibliographical information boric anhydride method of purification in 2006 and for example, utilize the water reaction in boric anhydride (diboron trioxide) and the dilute formic acid to form boric acid, can obtain concentration formic acid and high through distillation, remaining boric acid can reuse through drying and dehydrating, but the boric acid drying and dehydrating becomes boric anhydride, and temperature needs just can carry out more than 300 ℃, and the industrializing implementation difficulty is bigger, and boric anhydride costs an arm and a leg, and production cost is too high.To have introduced with ethyl benzoate, diethylene glycol (DEG) methyl esters or benzoic acid acetic anhydride etc. be the method that the extractant extracting rectifying obtains concentration formic acid and high solution for U.S. Pat-A4877490 and US-A4909907 etc. for another example, but because extractant costs an arm and a leg, and these extractants are high boiling substance, make its recovery and reuse very difficult, effect of extracting is also not ideal enough, so these methods are in industrial difficult realization.
Summary of the invention
The object of the present invention is to provide a kind of apparatus and method of intermittent azeotropic rectifying method purifying formic acid solution, adopt the heterogeneous azeotropic rectification method that 10% formic acid weak solution is purified and be the higher concentration formic acid of 80-85%.The present invention has that technological process is reasonable, apparatus structure is simple, efficient is high, cost is low and the characteristics of suitable industrialization continued operation.
The device of a kind of intermittent azeotropic rectifying method purifying formic acid solution provided by the invention comprises: rectifying column body of the tower, heat-insulation layer, tower still, heating jacket, condenser, phase-splitter and product storage tank; Body of the tower is installed heat-insulation layer outward, and the body of the tower lower end connects the tower still, and the upper end connects condenser and phase-splitter respectively, and phase-splitter connects condenser and product storage tank respectively.
Described condenser comprises product vapor uptake and parallel condensation chamber body, condenser pipe, thermometer, condensation-water drain, condensed water import, reflux ratio adjuster, condensation chamber phase-splitter and thief hatch.
Below the product vapor uptake installation thermometer suitable for reading, the condensation-water drain of condensation chamber interior condenser tube and condensed water import reflux ratio adjuster and condensation chamber phase-splitter are arranged, thief hatch is established in the condensation chamber lower end.
The step that the method for a kind of intermittent azeotropic rectifying method purifying formic acid solution provided by the invention comprises:
1) elementary purification
The operating pressure of rectifying column is a normal pressure, and number of theoretical plate is 15-30, and entrainer cyclohexane and 10% formic acid weak solution together add in the tower still, and its mass ratio is 4-9, and reflux ratio is 0.8-2, and tower top temperature is controlled at 68-69 ℃, and tower still temperature is controlled at 71-72 ℃.According to the triangular phase diagram of formic acid-water-cyclohexane, what steam at first is that the azeotropic of cyclohexane and water is formed, when the quality of the water of extraction is 70% left and right sides of raw material, and shut-down operation, it is 30% formic acid solution that the tower still can obtain mass concentration.
2) secondary purification
With chlorobenzene and mass concentration is that 30% formic acid solution joins rectifier bottoms together, and the rectifying column operating pressure is a normal pressure, and number of theoretical plate is 15-30, the mass ratio of chlorobenzene and formic acid solution is 3-5, reflux ratio is 1.5-3, and tower top temperature is controlled at 94-99 ℃, and tower still temperature is controlled at 96-101 ℃.According to the triangular phase diagram of formic acid-water-chlorobenzene, cat head extraction at first be that the azeotropic of chlorobenzene and water is formed, along with the continuous extraction of water and chlorobenzene, tower top temperature rises gradually, the concentration of formic acid in cat head also raises gradually.Extraction tower top temperature scope after the phase-splitting, can obtain the formic acid solution that mass concentration is 60-70% at 94-98 ℃ cut in phase-splitter.
3) compression rectification
With mass concentration is the formic acid solution adding rectifier bottoms of 60-70%, operating pressure is 4atm (the azeotropic composition under this pressure sees Table 3), reflux ratio is 5-10, originally controlling tower top temperature is 143-144 ℃, tower still temperature is 152-153 ℃, and along with moisture steams from cat head, temperature also rises thereupon, shut-down operation when tower top temperature arrives 152-154 ℃, the tower still can get the formic acid solution that mass concentration is 80-85%.
Beneficial effect of the present invention is mainly reflected in:
1) 10% formic acid weak solution purification can be the higher concentration formic acid of 80-85%.
2) the present invention adopts cyclohexane and chlorobenzene as entrainer respectively according to the method for operating that entrainer need be arranged in formic acid-steam liquid equilibrium relation proposition tower still, and the entrainer price is low, aboundresources, and it is convenient to reclaim.
3) azeotropic distillation technology of the present invention is utilized entrainer and formic acid and water to form ternary azeotrope in secondary purification process and is produced the method for concentration formic acid and high from cat head, is different from general azeotropic distillation and effective.
4) technological process of the present invention's employing is reasonable, and apparatus structure is simple, is fit to very much the industrialization operation.
Description of drawings
Fig. 1 is apparatus of the present invention schematic diagram.
The structure of condenser schematic diagram that Fig. 2 adopts for experiment.
The specific embodiment
The present invention adopts intermittent azeotropic rectifying equipment, and as shown in the figure, Fig. 1 is apparatus of the present invention schematic diagram.Wherein, 1 is the rectifying column body of the tower, and 2 is heat-insulation layer, and 3 is the tower still, and 4 is heating jacket, and 5 is condenser, and 6 is phase-splitter, and 7 is the product storage tank.The structure of condenser schematic diagram that Fig. 2 adopts for experiment.Wherein, 8 is thermometer, and 9 is condensation-water drain, and 10 is the condensed water import, and 11 is the reflux ratio adjuster, and 12 is the condensation chamber phase-splitter, and 13 is thief hatch.
The body of the tower 1 outer heat-insulation layer 2 of installing, rectifying column body of the tower 1 lower end connects tower still 3, and the upper end connects condenser 5 and phase-splitter 6 respectively, and phase-splitter 6 connects condenser 5 and product storage tank 7 respectively.
Condenser comprises: product vapor uptake and parallel condensation chamber body, condenser pipe, thermometer 8, condensation-water drain 9, condensed water import 10, reflux ratio adjuster 11, condensation chamber phase-splitter 12 and thief hatch 13.
Below condensation-water drain 9 in the product vapor uptake installation thermometer 8 suitable for reading, condensation chamber and the condensed water import 10 reflux ratio adjuster 11 and condensation chamber phase-splitter 12 are arranged, thief hatch 13 is established in the condensation chamber lower end.
Experiment adopts the parameter of batch fractionating tower to be: effective packing section height 0.8m, king-post diameter 30mm, the efficient stainless steel θ ring filler of interior dress 3mm * 3mm; The tower still is the there-necked flask of 250ml, peg graft respectively tower body, thermometer and glass stopper; Reflux ratio is sampled at cat head with relay and magnet control; The heating of tower still electricity consumption heating jacket, heating power 200W, body of the tower is incubated with the heat tracing band, and tower top is condensed to room temperature with running water; The theoretical cam curve of this tower is 20.
Condenser is the phase-splitting condenser, and the steam that cat head rises relies on the density contrast layering in phase-splitter after condenser condenses, and organic facies is back in the tower up, and water is by extraction.Because cyclohexane and water, chlorobenzene and water and formic acid can form heterogeneous azeotrope, its azeotropic composition sees Table 1 and table 2 respectively.
The azeotropic of table 1 formic acid-water-cyclohexane system is formed
The azeotropic of table 2 formic acid-water-chlorobenzene system is formed
The azeotropic of formic acid-water is formed under table 3 4atm
The step that the method for intermittent azeotropic rectifying method purifying formic acid solution comprises: at first adopting cyclohexane to make entrainer, is that 10% the dilute formic acid aqueous solution tentatively is concentrated to 30% with mass concentration; Re-use chlorobenzene and make entrainer, the azeotropic mixture of earlier continuous extraction chlorobenzene of cat head and water treats that the mixing of tower top temperature extraction chlorobenzene-formic acid-water in the time of 95 ℃-102 ℃ is formed, and the mass fraction of formic acid can reach 60%-70% after the phase-splitting; Use compression rectification at last, controlled pressure is at 4atm, and the tower still can reach the concentration formic acid and high solution about 80-85%.Concrete steps:
1) elementary purification
Open charging aperture, add the 20ml mass concentration and be 10% formic acid solution and the cyclohexane of 160ml, check everywhere whether good seal of interface, after overhead condenser feeds cooling water, connecting heating power supply heats reboiler, when treating that liquid comes to life in the reboiler, the tower body thermal circuit begins to connect.Keep infinite reflux, make tower top temperature be stabilized in 69 ℃, regulating reflux ratio is 1, and the product of extraction is collected in layering in the phase-splitter, and organic facies is back to rectifying column, the water extraction, and when the water volume of extraction reaches 15ml, shut-down operation.Take out phase-splitting behind the product from the tower still, formic acid concn is 38.4%
2) secondary purification
Open charging aperture, adding 21ml mass concentration is 30% formic acid solution and 79ml chlorobenzene, and keeping tower top temperature after the infinite reflux is 92 ℃, and regulating reflux ratio is 1.5, and the azeotropic of extraction chlorobenzene and water is formed.When tower top temperature rises to 94.5 ℃, collect cut once more, rise to 98.5 ℃ up to temperature, the mass concentration that gets formic acid after the ternary mixture phase-splitting of extraction is 60.1%, yield is 68%.
3) compression rectification
Adding 100ml mass concentration is 60% formic acid solution in rectifying column, and pressure is 4atm, and keeping tower top temperature after the infinite reflux is 144.2 ℃, and regulating reflux ratio is 6.Shut-down operation when treating that tower top temperature rises to 150 ℃, the formic acid mass concentration is 82% in the tower still product, the formic acid yield is 96.7%.