CN100374406C - Methylacrylic acid extracting and refining process - Google Patents

Abstract

The present invention relates to a method that tertiary butyl alcohol or isobutylene is used as raw materials, and methacrylic acid water solution containing impurities, such as acetic acid, etc. obtained through catalysis oxidation and absorption is rectified after the methacrylic acid water solution and mixed solvent carry out countercurrent extraction. The present invention carries out countercurrent extraction to methacrylic acid water solution by the mixture solvent of ester and hydrocarbon, the quality ratio of ester and hydrocarbon is from 1: 9 to 9: 1, the quality ratio of mixed solvent and methacrylic acid water solution is from 0.3 to 1.5, and the extraction rate of methacrylic acid reaches more than 98.7 %. High-purify methacrylic acid products are obtained from extract phases by pressure reducing desolventizing agents, light desolventizing constituents and heavy desolventizing constituents under an optimum technology condition.

Description

A kind of extraction of methacrylic acid and process for purification

Technical field

The present invention relates to the trimethyl carbinol or iso-butylene through catalyzed oxidation and the extraction and the rectification and purification method that absorb the methacrylic aqueous acid that obtains.

Background technology

Methacrylic acid (MAA) aqueous solution is to obtain through the methacrylic acid gaseous mixture of two sections catalyzed oxidation trimethyl carbinols or iso-butylene generation through condensation and water absorption.Except methacrylic acid, also contain other impurity and a large amount of water such as acetic acid, propionic acid, vinylformic acid in the methacrylic aqueous acid.In sepn process, except considering that these impurity exert an influence to the separating technology in downstream and quality product, separate that a large amount of water is the emphasis of selecting isolation technique in the MAA aqueous solution.

Because methacrylic acid and water easily form azeotrope (760mmHg, azeotropic point is 99.3 ℃), can not they be separated with simple method.Adopting azeotropic distillation is one of method of separating methacrylic acid, but adopts this method to have a large amount of water and entrainer to distill, and consume lot of energy, obviously not too economical.People for the methacrylic acid separation of water solution, adopt the method for extracting and separating can avoid some unfavorable factors carrying out the relatively back discovery of multiple technologies economical plan.

In the abstraction technique, choice of Solvent is most important.To the extraction agent of methacrylic aqueous acid, people have proposed multiple solvent at present, for example, and esters solvent, aromatic hydrocarbon solvent, alkane solvent and ketones solvent.It is more that ester class and aromatic hydrocarbon solvent are used, and its reason is mainly concerned with the choice of Solvent problem.The selectivity here not only refers to solvent to solute and former choice of Solvent height, and to impurity the performance of selective extraction should be arranged also, and promptly solvent has bigger difference to their partition ratio.

Esters solvent is higher to the percentage extraction of methacrylic acid, and under certain solvent ratio condition, disposable percentage extraction can reach more than 90%.Although esters solvent has higher partition ratio to methacrylic acid, esters solvent and water have very high mutual solubility.In addition, with regard to extracting power, esters solvent and varsol compare other impurity also higher percentage extraction.If these impurity are a large amount of be extracted to ester mutually in, except in rectifying, increasing the energy consumption, will have a negative impact to rectifying separation.If use single varsol, can avoid the problem big, but its percentage extraction is not as good as the esters solvent height with the water mutual solubility.In order to seek better extraction solvent, English Patent GB2015509A adopts dimethylbenzene and ethylbenzene (80%) to form mixed solvent with MMA (20%), and is bigger than the extraction agent that uses dimethylbenzene and ethylbenzene to form separately to the extraction partition ratio of methacrylic acid; The Chinese patent CN1249739A oxygenatedchemicals and the hydro carbons that can change into methacrylic acid, as Methylacrylaldehyde, iso-butylene, isobutyric aldehyde and methyl tertiary butyl ether (MTBE) equal solvent extraction methacrylic acid, its advantage is that the extraction agent boiling point is lower, easily separated, solvent can change into the purpose product, but the easy polymerization of solvent, loss is bigger.Thereby limited use.Therefore, the extraction agent that chooses only considers that partition ratio is not enough, and influence also seems very important to the boiling point of solvent to the rectifying polymeric.Solvent boiling point is too high, causes the rectifying column bottom temperature too high, easily polymerization; Solvent boiling point is too low, from considering it is favourable with the isolating angle of methacrylic acid, needs a large amount of refrigerating dutys but reclaim low boiling point solvent, and energy consumption is bigger.

Summary of the invention

In view of the above problems, the present invention adopts ester class (non-acetic ester) and varsol to make the mixed extractant of methacrylic acid, has moderate boiling point, percentage extraction height (more than 99.5%), other impurity is had selectivity preferably, can produce highly purified methacrylic acid.

The present invention is a raw material with the methacrylic aqueous acid of 1～50 quality % of the catalyzed oxidation trimethyl carbinol or iso-butylene production, the aqueous solution of preferred 10～30 quality %, adopt the mixed solvent of ester class and hydro carbons to carry out counter-current extraction, the desolventizing that reduces pressure, take off light constituent and take off the method for heavy constituent, isolate highly purified methacrylic acid.Whole extraction and rectifying comprise following four steps:

1) mixed solvent and methacrylic aqueous acid carry out counter current contact in turntable extracting tower;

2) extraction phase enters the desolventizing tower and carries out desolventizing, and the cat head material returns extraction tower;

3) desolventizing Tata substrate material enters cut light tower, and the light constituent that removes returns extraction tower;

4) taking off light component Tata substrate material enters and takes off heavies column and isolate the high purity methacrylic acid product.

Wherein, mixed solvent is made of ester class and hydrocarbons, esters solvent is ethyl propionate, propyl propionate, allyl propionate, butyl propionate, ethyl propenoate, butyl acrylate, methyl methacrylate, Jia Jibingxisuanyizhi, methyl isobutyrate or 2-butylene acid methyl esters, and varsol is hexane, heptane, hexanaphthene, methylcyclohexane, benzene, toluene or dimethylbenzene.The ester class is 1: 9～9: 1 with the mixing quality ratio of hydro carbons in the mixed solvent, and entering the mixed solvent of extraction tower and the mass ratio of methacrylic aqueous acid is 0.3～1.5: 1, carries out the counter current contact extraction under 25～50 ℃.A certain amount of acetic acid is contained in the extraction tower bottom, acrylic acid waste water removes the acetic acid retrieving arrangement, contains the raw material of the extraction phase of methacrylic acid as the desolventizing tower.

Add Resorcinol, p methoxy phenol or 2,2,6 in the desolventizing bottoms material, 6-tetramethyl piperidine and phosphorous acid esters stopper thereof, add-on is 30～3000ppm.

The extraction phase that contains methacrylic acid removes solvent in the desolventizing tower, the solvent that removes returns extraction tower and reuses.Operational condition is: column bottom temperature 85-100 ℃, reflux ratio are 0.5～2, the stopper add-on is that 30～3000ppm, vacuum tightness are 10～15kPa, and the content of methacrylic acid is not less than in 85 quality % and the solvent overhead and does not contain methacrylic acid in the control tower substrate material.

Desolventizing Tata substrate material enters and removes light component such as acetic acid, vinylformic acid, propionic acid and a small amount of solvent in the cut light tower, and the light component and the solvent that remove return extraction tower.Operational condition is: column bottom temperature 85-95 ℃, reflux ratio is 1～5, vacuum tightness is 3～6kPa, and in the control tower substrate material content of methacrylic acid be not less than 99.5 quality %, light component content less than methacrylic acid content in 0.2 quality % and the cat head material less than 80 quality %.

Take off light component Tata substrate material and enter to take off and remove heavy component in the heavies column, cat head is the high purity methacrylic acid product, reaches more than the 99.7 quality %.Tower bottom regrouping share demethyl vinylformic acid pyrolysis recovery device.This tower operational condition is: column bottom temperature 84-94 ℃, reflux ratio is 0.5～3, and vacuum tightness is 3～5kPa.

First advantage of the present invention is to adopt mixed solvent to make extraction agent, has avoided independent use ester class to make the problem that methacrylic acid extraction agent and water have bigger mutual solubility.If contain a large amount of water in the extraction phase then not only cause desolventizing overload in the desolventizing tower, and can consume a large amount of energy.Another advantage of the present invention is that the extracting power of impurity such as mixed solvent Dichlorodiphenyl Acetate, vinylformic acid weakens, and the selectivity of methacrylic acid is seemed higher owing to add hydrocarbons as the second extraction agent component.Like this, impurity such as acetic acid is mainly stayed water in the process of extracting and separating methacrylic acid, for condition has been created in the recovery of acetic acid in downstream unit.

Description of drawings

Fig. 1 is methacrylic acid extraction and process for purification schema.

Number in the figure is: the 1-extraction tower, and 2-desolventizing tower, 3-take off light component tower, and 4-takes off the heavy component tower.

Embodiment

With embodiment content of the present invention is described further below.

Unless otherwise indicated, per-cent % all is weight percentage below.

Embodiment 1

The methacrylic acid that obtains with the catalyzed oxidation trimethyl carbinol or iso-butylene (being called for short MAA)) aqueous solution is raw material, with methyl methacrylate (being called for short MMA) and toluene is mixed extractant, the ratio of mixture of MMA and toluene is 3: 7 (quality), the mass ratio of the mixed solvent and the MAA aqueous solution is 0.8: 1, extraction temperature is 35 ℃, is to carry out the counter current contact extraction in the φ 85 small-sized turntable extracting towers [1] having 40 tower trays, tower diameter.When rotary speed be 700r/min, when the raw material treatment capacity is 25kg/h, percentage extraction is 99.8%.The raw material composition sees Table 1.The extraction phase composition sees Table 2.

Table 1 MAA aqueous feed solution is formed

Form	Acetone	Methylacrylaldehyde	Water	Acetic acid	Vinylformic acid	MAA
							Content, %	0.15	0.31	72.87	9.81	2.04	14.77

Table 2 extraction phase is formed

Form	Water	MMA	Toluene	Acetic acid	Vinylformic acid	MAA	Acetone	Methylacrylaldehyde
									Content, %	1.48	23.24	55.44	2.86	1.49	14.97	0.1	0.60

The extraction phase that will contain MAA is squeezed into the desolventizing sieve-tray tower [2] that tower diameter is Ф 40 with feedstock pump, the quinhydrones add-on to be 500ppm, column bottom temperature less than 94 ℃, reflux ratio be 0.6 and vacuum tightness be to remove lighter components such as MMA and toluene mixed solvent and a spot of Methylacrylaldehyde, acetone under the condition of 10～15kPa, a small amount of light component and mixed solvent return extraction tower, and the bottoms material enters and takes off light component tower [3].In the cut light tower [3], column bottom temperature less than 92 ℃, reflux ratio be 4, vacuum tightness is under 3～6kPa condition, removes light component such as acetic acid, vinylformic acid and propionic acid and a small amount of solvent, the cat head material returns extraction tower.The bottoms material enters and takes off heavy component tower [4], column bottom temperature less than 90 ℃, reflux ratio be 1, vacuum tightness is to isolate the MAA product under 3～5kPa condition, the rectifying tower separating resulting sees Table 3.As shown in Table 3, contain the separation of the extraction phase of MAA through 3 rectifying tower, the purity of the MAA product that obtains at last is 99.85%, and product colourity (AHPA) is less than 10, and moisture content is less than 0.001%.

Table 3 rectifying tower separating resulting

Composition/%	The desolventizing tower		Take off light component tower		Take off the heavy component tower
							At the bottom of the tower	Cat head	At the bottom of the tower	Cat head	At the bottom of the tower	Cat head
	Methylacrylaldehyde	-	0.01	-	0.001	-							-
Water							-	0.35	-	0.26	-	0.0007
	MMA	2.00	28.37	0.006	1.65	-							0.005
Toluene							5.96	68.10	0.019	6.22	-	0.017
	Acetic acid	3.14	2.45	0.006	7.76	-							0.012
Vinylformic acid							3.50	0.05	0.002	13.62	0.31	0.01
	MAA	85.13	0.004	99.50	70.18	84.65							99.85
Isopropylformic acid							0.01	0.004	-	0.03	-	0.03
	Phenylformic acid	0.01	-	0.21	-	7.01							0.007
P-methylbenzoic acid							0.05	-	0.17	-	3.40	-

Embodiment 2

The MAA aqueous feed solution is with embodiment 1, with ethyl propenoate and heptane is mixed extractant, the ratio of mixture of ethyl propenoate and heptane is 4: 6 (quality), the mass ratio of the mixed solvent and the MAA aqueous solution is 0.8, extraction temperature is 35 ℃, is that [1] carries out the counter current contact extraction in the Ф 85 small-sized turntable extracting towers having 40 tower trays, tower diameter.When rotary speed be 700r/min, when the raw material treatment capacity is 25kg/h, percentage extraction is 99.7%.The extraction phase composition sees Table 4.

Table 4 extraction phase is formed

Form	Water	Ethyl propenoate	Heptane	Acetic acid	Vinylformic acid	MAA	Acetone	Methylacrylaldehyde
									Content/%	1.76	32.65	46.34	2.73	1.50	14.37	0.11	0.10

The extraction phase that will contain MAA is squeezed into the desolventizing sieve-tray tower [2] that tower diameter is Ф 40 with feedstock pump, at phosphorous acid-3-(2,2,6,6-tetramethyl piperidine free radical) the ester add-on be raw materials used 50ppm, column bottom temperature less than 90 ℃, reflux ratio be 0.6 and vacuum tightness be to remove lighter components such as ethyl propenoate and heptane mixed solvent and the rare aldehyde of a spot of methyl-prop, acetone under the condition of 10～15kPa, a small amount of light component and mixed solvent return extraction tower, and the bottoms material enters and takes off light component tower [3].In the cut light tower [3], column bottom temperature less than 91 ℃, reflux ratio be 4, vacuum tightness is under 3～6kPa condition, removes light component such as acetic acid, vinylformic acid and propionic acid and a small amount of solvent, the cat head material returns extraction tower.The bottoms material enters and takes off heavies column [4], column bottom temperature less than 89 ℃, reflux ratio be 1, vacuum tightness is to isolate the MAA product under 3～5kPa condition, the rectifying tower separating resulting sees Table 5.As shown in Table 5, contain the separation of the extraction phase of methacrylic acid through 3 rectifying tower, the purity of the MAA product that obtains at last is 99.70%, and product colourity (AHPA) is less than 10, and moisture content is less than 0.001%.

Table 5 rectifying tower separating resulting

Composition/%	The desolventizing tower		Lightness-removing column		Weight-removing column
							At the bottom of the tower	Cat head	At the bottom of the tower	Cat head	At the bottom of the tower	Cat head
	Methylacrylaldehyde	-	0.01	-	0.001	-							-
Water							-	0.56	-	0.25	-	-
	Ethyl propenoate	3.30	41.63	0.006	3.68	-							0.001
Heptane							4.24	55.40	0.003	4.81	-	0.015
	Acetic acid	2.71	2.23	0.006	8.25	-							0.011
Vinylformic acid							3.50	0.05	0.002	12.98	0.53	0.013
	MAA	86.13	0.003	99.60	69.69	87.25							99.70
Isopropylformic acid							0.02	0.004	-	0.01	-	0.025
	Phenylformic acid	0.01	-	0.15	-	8.54							0.005
P-methylbenzoic acid							0.07	-	0.13	-	3.66	-

Embodiment 3～12

Raw material and extraction and rectifying condition are with embodiment 1, and institute's difference is that the service temperature of extraction agent kind and corresponding each rectifying tower is different, the results are shown in Table 6 and table 7.

Table 6 adopts different composite extractants and the separating resulting under the distillation operation condition

Embodiment	3	4	5	6	7
						Extraction agent	Ethyl propionate+hexane	Butyl propionate+heptane	Propyl propionate+hexanaphthene	Allyl propionate+methylcyclohexane	Ethyl propenoate+benzene
Desolventizing tower stopper	Resorcinol	Resorcinol	Resorcinol	Resorcinol	Resorcinol
						The stopper consumption, ppm	500	300	800	200	2000
Desolventizing tower temperature, ℃	93	93	94	94	93
						Take off light component tower temperature, ℃	90	91	91	91	91
Take off heavy component tower temperature, ℃	88	89	89	89	89
						The MAA percentage extraction, %	97.83	98.75	98.73	99.27	99.30
Product purity, %	99.80	99.75	99.86	99.70	99.85
						Product colourity, AHPA	10	10	10	10	10
The product water-content, %	0.001	0.001	0.001	0.001	0.001

Table 7 adopts different composite extractants and the separating resulting under the distillation operation condition

Embodiment	8	9	10	11	12
						Extraction agent	Butyl acrylate+toluene	MMA+ dimethylbenzene	Jia Jibingxisuanyizhi+toluene	Methyl isobutyrate+dimethylbenzene	2-butylene acid methyl esters+benzene
Desolventizing tower stopper	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester
						The stopper consumption, ppm	500	500	500	500	500
Desolventizing tower temperature, ℃	94	94	94	94	94
						Take off light component tower temperature, ℃	92	92	92	92	92
Take off heavy component tower temperature, ℃	90	90	90	90	90
						The MAA percentage extraction, %	99.73	99.75	99.78	98.81	99.52
Product purity, %	99.85	99.70	99.78	99.76	99.72
						Product colourity, AHPA	10	10	10	10	10
The product water-content, %	0.001	0.001	0.001	0.001	0.001

Comparative example 1～16

Raw material and extraction and rectifying condition are with embodiment 1, and institute's difference is that the service temperature of extraction agent kind and corresponding each rectifying tower is different, the results are shown in Table 8 and table 9.

Separating resulting under single extraction agent of table 8 and the corresponding distillation operation condition

Comparative example	1	2	3	4	5	6
							Extraction agent	Ethyl propionate	Butyl propionate	Ethyl propenoate	Butyl acrylate	MMA	Jia Jibingxisuanyizhi
Desolventizing tower stopper	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester
							The stopper consumption, ppm	500	500	500	500	500	500
Desolventizing tower temperature, ℃	94	94	94	94	94	94
							Take off light component tower temperature, ℃	90	90	90	90	90	90
Take off heavy component tower temperature, ℃	89	89	89	89	89	89
							The MAA percentage extraction, %	87.50	87.70	89.87	89.53	90.51	88.30
Product purity, %	99.15	99.40	99.20	99.40	99.76	99.45
							Product colourity, AHPA	10	10	15	10	10	20

The product water-content, %

0.01

0.005

0.003

0.001

0.001

0.008

Separating resulting under single extraction agent of table 9 and the distillation operation condition

Comparative example	7	8	9	10	11	12
							Extraction agent	Methyl isobutyrate	2-butylene acid methyl esters	Heptane	Hexanaphthene	Benzene	Toluene
Desolventizing tower stopper	Resorcinol	Resorcinol	Resorcinol	Resorcinol	Resorcinol	Resorcinol
							The stopper consumption, ppm	500	500	500	500	500	500
Desolventizing tower temperature, ℃	94	94	92	92	94	94
							Take off light component tower temperature, ℃	91	91	88	88	91	92
Take off heavy component tower temperature, ℃	89	89	87	87	89	89
							The MAA percentage extraction, %	87.20	88.50	83.86	82.10	85.40	86.66
Product purity, %	99.70	99.65	99.63	99.30	99.64	99.78
							Product colourity, AHPA	10	10	15	15	10	10
The product water-content, %	0.002	0.005	0.001	0.001	0.001	0.001

Separating resulting under different extraction agents of table 10 and the corresponding distillation operation condition

Comparative example	13	14	15	16
					Extraction agent	Hexane	Dimethylbenzene	Ethyl acetate+toluene	Butylacetate+hexanaphthene
Desolventizing tower stopper	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester	Phosphorous acid ester
					The stopper consumption, ppm	500	500	500	500
Desolventizing tower temperature, ℃	91	94	94	93
					Take off light component tower temperature, ℃	87	91	91	89
Take off heavy component tower temperature, ℃	87	90	90	89
					The MAA percentage extraction, %	84.19	83.75	91.51	92.10
Product purity, %	99.46	99.34	99.54	99.56
					Product colourity, AHPA	10	10	15	10
The product water-content, %	0.001	0.001	0.001	0.001

Table 11 different solvents is to the influence of methacrylic acid raw material abstraction phase composite

Main ingredient	Extraction phase is formed, wt%
							Toluene	Toluene and methyl methacrylate	Ethyl propenoate	Ethyl propenoate and heptane	Heptane	Methyl methacrylate
	Methacrylic acid	22.76	22.33	21.65	22.36	21.56							20.77
Vinylformic acid							0.43	0.51	0.34	0.35	0.46	0.55
	Acetic acid	1.67	2.30	2.56	2.06	1.56							2.91
Water							1.29	1.48	5.63	1.76	1.23	8.41
	Solvent	73.80	72.34	68.95	72.96	74.35							66.48

By table 8～11 as can be known, single solvent is made the methacrylic acid extraction agent, and the percentage extraction of esters solvent is higher, but also higher with the mixing degree of water.The percentage extraction of mixed solvent is a little less than ester solvent, but is much smaller than single esters solvent with the mutual solubility of water, shows extraction ability preferably.

Claims (5)

1. the extraction of a methacrylic acid and process for purification, it is characterized in that absorbing the methacrylic aqueous acid that obtains 1～50 quality % with the trimethyl carbinol or iso-butylene catalytic oxidation product through water is raw material, mixture with ester class and hydro carbons is a solvent, esters solvent is a propyl propionate, allyl propionate, butyl propionate, ethyl propenoate, butyl acrylate, methyl methacrylate, Jia Jibingxisuanyizhi, isopropylformic acid first vinegar or 2-butylene acid methyl esters, varsol is a hexane, heptane, hexanaphthene, methylcyclohexane, benzene, toluene or dimethylbenzene, through counter-current extraction, methacrylic acid be extracted to mixed solvent mutually in, obtain highly purified methacrylic acid by rectifying then;

Extraction and rectifying comprise following four steps:

1) mixed solvent and methacrylic aqueous acid carry out counter current contact in turntable extracting tower [1];

2) extraction phase enters desolventizing tower [2] and carries out desolventizing, and the cat head material returns extraction tower [1];

3) desolventizing tower [2] bottoms material enters cut light tower [3], and the light constituent that removes returns extraction tower [1];

4) taking off light component tower [3] bottoms material enters and takes off heavies column [4] and isolate the high purity methacrylic acid product.

2. according to the described method of claim 1, it is characterized in that the mixing quality ratio of esters solvent and varsol is 1: 9～9: 1 in the mixed solvent, entering the mixed solvent of extraction tower and the mass ratio of methacrylic aqueous acid is 0.3～1.5: 1, carries out counter-current extraction under 25～50 ℃.

3. according to the described method of claim 1, it is characterized in that the operational condition of each rectifying tower is: 86～100 ℃ of desolventizing tower [2] column bottom temperatures, reflux ratio is 0.5～2, vacuum tightness is 10～15kPa; 80～95 ℃ of cut light tower [3] column bottom temperatures, reflux ratio is 1～5, vacuum tightness is 3～6kPa; Take off 84～94 ℃ of heavies column [4] column bottom temperatures, reflux ratio is 0.5～3, and vacuum tightness is 3～5kPa.

4. according to the described method of claim 1, it is characterized in that adding in the desolventizing bottoms material Resorcinol, p methoxy phenol or 2,2,6,6-tetramethyl piperidine or phosphorous acid ester stopper, add-on is 30～3000ppm.

5. according to the described method of claim 1, the mass percentage concentration that it is characterized in that raw material methacrylic aqueous acid is 10～30%.

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