GB2096601A - Process for producing methacrylic acid - Google Patents
Process for producing methacrylic acid Download PDFInfo
- Publication number
- GB2096601A GB2096601A GB8206428A GB8206428A GB2096601A GB 2096601 A GB2096601 A GB 2096601A GB 8206428 A GB8206428 A GB 8206428A GB 8206428 A GB8206428 A GB 8206428A GB 2096601 A GB2096601 A GB 2096601A
- Authority
- GB
- United Kingdom
- Prior art keywords
- acetic acid
- methacrolein
- methacrylic acid
- oxidation
- process according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/25—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring
- C07C51/252—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring of propene, butenes, acrolein or methacrolein
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
- C07C45/33—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties
- C07C45/34—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties in unsaturated compounds
- C07C45/35—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties in unsaturated compounds in propene or isobutene
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
- C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/23—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of oxygen-containing groups to carboxyl groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/23—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of oxygen-containing groups to carboxyl groups
- C07C51/235—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of oxygen-containing groups to carboxyl groups of —CHO groups or primary alcohol groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
- C07C51/377—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Methacrylic acid is prepared by the catalytic gas phase oxidation of one or more of the gases isobutylene, t-butanol, methacrolein, isobutyraldehyde and isobutyric acid with molecular oxygen, quenching the reaction product from the oxidation and than recovering methacrylic acid from the quenched product. It is possible to achieve a high concentration of aqueous acetic acid in the solution formed as by-product by recycling the by-product aqueous acetic acid solution to one or both of the oxidation or quenching steps.
Description
SPECIFICATION
Process for producing methacrylic acid
The present invention relates to a process for producing methacrylic acid in which the aqueous acetic acid solution formed as by-product in the production of methacrylic acid by the gas phase catalytic oxidation of isobutylene, t-butanol, methacrolein, isobutyraldehyde, isobutyric acid or a mixture thereof is made use of.
It is well known that methacrylic acid can be produced by the gas phase catalytic oxidation of one or more of isobutylene, t-butanol, methacrolein, - isobutyraldehyde and, isobutyric acid (hereinafter simply referred to as "starting gas"), and it is also well known that, in the production of methacrylic acid by gas phase catalytic oxidation, the water supplied to the reaction system is effective for improving the selectivity of reaction and the life of the catalyst.
Recently, research on the process for producing methacrylic acid from the starting gas has shown remarkable progress, and catalysts and methods for producing methacrylic acid in very high yields have been proposed. However, the selectivity for methacrylic acid is far from 100%, even when using these improved catalysts, and a large amount of by-products are produced.
Among the by-products, there is acetic acid which is produced in a relatively large amount. The amount of acetic acid formed reaches even about 5 to 30% by weight of methacrylic acid, though it depends on the performance of the catalysts used. The acetic acid formed as byproduct in the reaction, however, is markedly diluted by (a) water fed to the reaction system together with the starting material gas, (b) water formed in the reaction, further (c) water added to quench directly the rection product gas containing a highly polymizable methacrylic acid and methacrolein and to recover the methacrylic acid, and (d) water added in the step of purifying the absorption solution used in the recovery step of methacrolein.Consequently, the concentration of acetic acid in the stream after the recovery of methacrylic acid is very low and is generally 5% by weight or less depending on the performance of the oxidation catalyst.
The treatment of such a diluted aqueous acetic acid is roughly classified into two methods.
One of the methods is disposal as waste water and the other method is the recovery of acetic acid as a useful material.
Disposal as waste water naturally requires a treatment for avoiding the waste water pollution, and a burning method is thought of as the treatment, but self-burning is impossible because of low concentration of acetic acid. Consequently, a large volume of supplementary fuel is required, resulting in a requirement of very great treatment cost. As another treatment method, bacteriological treatment method is also known. Even in this case, in addition to the cost for the bacteriological treatment, a large amount of energy is required in order to isolate, dry and cool the activated dirt formed.
The recovery of acetic acid is also preferred from the viewpoint of efficient utilization of resources, but the low concentration of acetic acid in the aqueous solution to be recovered increases the recovery cost, which results in a big obstacle. The following methods are known as the representative methods for recovering acetic acid from an aqueous acetic acid solution:
(1) distillation method,
(2) azeotropic distillation method, and
(3) solvent extraction method.
In the distillation method, water which is present in a large amount is the low boiling point component and, moreover, a large number of plates and a large reflux ratio in a distillation tower are required because the specific volatility of water against acetic acid is small. Thus, this method is not said to be a good method for recovering acetic acid from a diluted aqueous acetic acid solution.
The azeotropic distillation method is a method of facilitating the elevation of water to the tower top by adding a component capable of forming an azeotropic mixture with water as an entrainer. According to this method, the number of plates in the acetic acid-separating tower and the reflux ratio can be reduced, but equipment for recovering the entrainer becomes necessary. Thus, this azeotropic distillation method is also not recommendable as a method of the recovery of acetic acid from a diluted aqueous acetic acid solution.
The solvent extraction method is a process for selectively extracting acetic acid by using esters, ethers, ketones and the like as an extracting solvent. For example, Chem. Eng. Progress,
Vol. 59 (10), page 65 states that among the above three methods, the solvent extraction method is excellent in both investment and operation cost, particularly in low concentration region.
The above mentioned literature indicates, however, that even in this solvent extraction method, both investment and operation cost increase sharply with a decrease in concentraction of acetic acid in the starting material (e.g., if the acetic acid concentration in the starting material is reduced from 10% by weight to 5% by weight, both investment and operation cost increase to 1.8 times). The same comments are made in the above literature, Vol. 73 (5), p. 55, and it is said that if the acetic concentration is 1% by weight, the energy cost alone required for separation reaches the estimated value of acetic acid. This tendency seems to be further strengthened with an elevation of energy cost.
Thus, the acetic acid formed as by-product in the gas-phase catalytic oxidation reaction step for producing methacrylic acid requires a great recovery cost because of its low concentration, and as a result, increases the cost for producing methacrylic acid. Therefore, some resolution measure has been desired.
As a result of intensive research to solve these problems, the present inventors have studied the utilization of a diluted aqueous acetic acid solution formed as by-product in the oxidation reaction in the process for the production of methacrylic acid in any form, and have found that (1) the starting material gas is not adversely affected by the oxidation reaction by recycling the aqueous acetic acid solution formed as by-product in the process for the production of methacrylic acid to the oxidation reaction step, and moreover, most of the acetic acid supplied flows out as such without reaction on the catalyst, and hence, the acetic acid concentration in the reaction product is greatly increased; and
(2) high-boiling compounds such as methacrylic acid, acrylic acid, acetic acid, water and the like can be condensed from the product gas without lowering the acetic acid concentration by feeding the aqueous acetic acid solution formed as by-product to a quenching step for quenching the gas obtained in the oxidation reaction step.
Since it is possible to obtain an aqueous acetic acid sqlution of much higher concentration than the conventional methods by using the above-mentioned two findings separately or in combination, the cost for recovering acetic acid is greatly reduced, and as a result, it has become possible to contribute greatly to the reduction of the cost of production of methacrylic acid.
In this invention, the following step may be combined with the above-mentioned process.
That is to say, the acetic acid solution formed as by-product may be fed to the methacroleinrecovery step as the absorbing agent in the absorption-recovery of methacrolein from the remaining gas obtained by condensing and removing high-boiling compounds such as methacrylic acid, acrylic acid, acetic acid, water and the like from the product gas as mentioned in above step (2). By this combination, methacrolein can be recovered with a much higher efficiency than when water is used as the absorbing agent, while making the best use of the convenience and advantage in process resulting from the use of water which is a very inexpensive absorbing agent as compared with a commercially available organic solvent.
According to the present invention, there is provided a process for producing methacrylic acid comprising the oxidation reaction step for catalytically oxidizing in the gas-phase at least one starting gas selected from the group consisting of isobutylene, t-butanol, methacrolein, isobutyraldehyde and isobutyric acid with a molecular oxygen-containing gas, the quenching step for quenching the gas produced by the oxidation reaction and the recovery step for recovering methacrylic acid formed, characterized by recycling the aqueous acetic solution formed as byproduct to the above oxidation reaction step or to the above quenching step or both the above steps.
The process for producing methacrylic acid from isobutylene and/or t-butanol by the gas phase catalytic oxidation is generally the following two-step oxidation reaction:
Isobutylene and/or t-butanol
methacrolein
Methacrolein
methacrylic acid
It is also possible, however, to carry out the oxidation reaction in one step from the starting material to the final product, methacrylic acid, without taking out the intermediate product methacrolein of the system.
As the catalyst for oxidizing isobutylene and/or t-butanol into methacrolein and methacrylic acid, there may be effectively used a catalyst containing Mo, Bi and Fe in this invention.
As the catalyst for oxidizing methacrolein and/or isobutyraldehyde and/or isobutyric acid, there may be effectively used a catalyst containing at least Mo and P in this invention, and preferred is a catalyst containing at least Mo, P, V and an alkali metal.
It is also possible to convert directly isobutylene to methacrylic acid using a catalyst containing Mo and P, and said catalyst may be applied to this invention.
The catalyst can be prepared in the conventional manner, and, for example, the processes disclosed in Japanese Patent Application Kokai (Laid-Open) No. 4010/75 and Japanese Patent
Application Kokai (Laid-Open) No. 46,016/77 are preferably used.
The proportion of molecular oxygen used to the starting gas may be varied depending on the kind of the starting gas, though generally the molar ratio of molecular oxygen to the starting gas is preferably in the range of from 0.5 to 20, more preferably 0.6 to 10. The starting gas fed may contain other inert gases such as nitrogen, carbon dioxide gas, saturated hydrocarbon and the like.
The oxidation reaction temperature may be varied depending on the kind of catalyst, though there is usually used a temperature in the range of from 200 to 500"C, preferably 250 to 450"C.
The starting gas is fed at a space velocity (SV) of 100 to 8,000 hr-', preferably 300 to 5,000 hr-1 (NTP standard). The reaction may be carried out under pressure, under normal pressure or under reduced pressure, but an excessively high or low pressure has an adverse effect on the production cost due to increase in power cost. Consequently, said reaction is generally carried out at a pressure of O to 5 kg/cm2G. The reaction can be carried out by means of any of the fixed bed, fluidized bed, or moving bed.
The aqueous acetic acid solution formed as by-product in the above oxidation reaction step is fed to the oxidation reaction step or to the quenching step for quenching the gas formed in the oxidation reaction step or to both steps. The concentration of acetic acid in the aqueous acetic acid solution is not critical, and the aqueous acetic acid solution formed as by-product in the oxidation reaction step can be used as such. Furthermore, the acetic acid solution may, if necessary, be diluted with water unless it impairs economy.
When the aqueous acetic acid solution is fed to the oxidation reaction step, said solution may be fed to either step of the above-mentioned two-step oxidation reaction. It is also possible to feed the solution only to the former oxidation step and to feed the reaction product gas to the latter oxidation step as such without isolating or purifying the product in the former reaction step and to carry out the latter oxidation reaction. Bt is also possible to feed the acetic acid solution to the oxidation reaction of isobutyraldehyde into methacrolein and methacrylic acid and to the oxidation reaction of isobutyric acid into methacrylic acid, thereby increasing the acetic acid concentration in the product.The molar ratio of the aqueous acetic acid solution fed to the starting gas is preferably in the range of from 1 to 30, more preferably in the range of from 1 to 20.
When the aqueous acetic acid solution is fed to the quenching step, the weight ratio of said solution fed to oxidation reaction product is preferably in the range of from 0.001 to 1.0, more preferably 0.01 to 0.30, though it may be varied depending on the composition of the oxidation reaction product gas. Excessive feeding of the aqueous acetic acid solution is not desired because the concentration of methacrylic acid obtained from the quenching tower is lowered.
According to the present invention, a part of the aqueous acetic acid solution formed as byproduct may be recycled to the step of recovering methacrolein from the remaining gas obtained by removing by condensation high-boiling compounds from the oxidation product gas in the quenching step. In this case, the amount of aqueous acetic acid solution fed may be varied depending on the operating pressure and the temperature in the absorption tower, though the weight ratio of the acetic acid solution to the methacrolein-containing gas falls usually in the range of from 0.1 to 1 0. The pressure, the temperature and the absorbing liquid volume are determined in consideration of economy.
This invention is further explained referring to the accompanying drawings, in which
Figure 1 is a flow sheet showing the outline of this invention,
Figure 2 is a flow sheet showing a combination of a methacrolein recovery step with the process of Fig. 1, and
Figure 3 is a flow sheet showing in detail an example of the process of this invention.
In Figs. 1, 2 and 3, 2 refers to oxidation reaction step, 4 to quenching step, 8 to methacrylic acid-recovery step, 1 3 to acetic acid-recovery step, 1 6 to methacrolein-recovery step, 1, 3, 5, 7, 9, 10, 11, 12, 14, 15, 17, 18, 20 and 21 to 51 to conduits, 101 to isobutylene oxidation reactor, 102 to methacrolein oxidation reactor, 1 03 to quenching tower, 104 to methacrolein recovery tower, 106 to extractant-separating tower, 107 to acetic acid extraction tower, 108 to extractant-separating tower, 1 O9 to methacrolein-absorbing tower and 1 10 to methacrolein stripper.
In Fig. 1, the starting gas which is the raw material for methacrylic acid, and the molecular oxygen containing gas are fed to the oxidation reaction step 2 from the conduit 1 and the gas formed in the oxidation reaction step is fed via conduit 3 to the quenching step 4 for the purpose of minimizing the formation of polymers by quenching polymerizable methacrylic acid and the like and simultaneously recovering methacrylic acid in the liquid form. In the quenching step 4, methacrylic acid is recovered in the form of an aqueous solution, and generally, the aqueous methacrylic acid solution obtained is cooled and recycled to bring it into direct contact with the reaction product gas.In this case, it is necessary in the quenching step to recover substantially all the methacrylic acid present in the reaction product gas, but, in this case, it is impossible to exclude substantially all of the methacrylic acid from the discharged gas by only circulating the aqueous methacrylic acid solution, and it is necessary to use water free from methacrylic acid together therewith. Therefore, according to the conventional method, as a result thereof, the acetic acid formed as by-product has been diluted. Moreover, steam is usually fed together with the raw materials to the reaction system for smooth progress of the oxidation reaction, and this has resulted in decrease of the concentration of the acetic acid formed.
In this invention, on the other hand, what is recycled is not the aqueous methacrylic acid solution, but the aqueous acetic acid solution obtained by recoverying methacrylic acid from the product which has been sent from the quenching step 4 to the methacrylic acid recovery step 8 via the conduit 7. Consequently, it has been made possible to feed an aqueous acetic acid solution of a high concentration to the acetic acid recovery step 1 3 by recycling the aqueous acetic acid solution to the oxidation step via the conduit 11 in place of the steam, and it has also been made possible to feed an aqueous acetic acid solution of a high concentration to the acetic acid recovery step 1 3 by recycling the aqueous acetic acid solution to the quenching step via the conduit 5 in place of the aqueous methacrylic acid solution.
An amount of acetic acid is present in the off-gas withdrawn via the conduit 6, though the amount is slight, and the off-gas is discharged into the air after treatment in the off-gas-treating step (not shown in the drawings), while a part thereof may be recycled to the oxidation step without the treatment.
The aqueous methacrylic acid solution obtained via the conduit 7 is fed to the methacrylic acid recovery step 8. Methacrylic acid is obtained via the conduit 9, and an aqueous solution containing organic materials consisting mainly of the by-product acetic acid is obtained via the conduit 1 0. As mentioned above, a part thereof is recycled to the oxidation reaction step via the conduit 11 and/cr to the quenching step via the conduit 5, and the remainder thereof is fed to the acetic acid recovery step 1 3 via the conduit 1 2. Acetic acid is obtained from the conduit 14 and then sent to a purification step, if necessary, to give glacial acetic acid.On the other hand, waste water is obtained from conduit 1 5. Since this waste water contains a trace of organic materials, it is usually discharged from the system via the microbial treatment step (not shown in the drawings).
In Fig. 2, the methacrylic acid is produced in the same manner as in Fig. 1, except that the methacrolein-containing gas stream effluent from the quenching step is fed to the methacroleinrecovery step 1 6 through the conduit 1 B, the methacrolein-recovery step consisting mainly of an absorbing zone for absorbing methacrolein with an absorbing solvent and a stripping zone for separating the methacrolein from the absorbing solvent.
As the methacrolein-absorbing solvent, hydrocarbons have hithereto been used, such as light oil, kerosene, heavy oil, creosote oil, toluene, xylene, alkylnaphthalene and the like. In order to prevent the loss of the solvent due to incorporation of the solvent into the off-gas, it is necessary to use a high-boiling solvent, and in this case, the temperature in the stripping zone to separate the methacrolein from the solvent becomes too high, whereby polymerization of methacrolein is caused, resulting in difficulty in operation in the stripping zone. On the other hand, when the aqueous acetic acid solution is fed to the quenching step, acetic acid and the like become contained in the gas passing through the conduit 18, and hence, the acetic acid and the like are accumulated in the solvent and a difficulty is caused in removing them.
As the methacrolein-absorbing solvent, water has been known in addition to the abovementioned solvents. Water is a preferable solvent in respect of simplification of the process, but is disadvantageous in that the absorption efficiency is low. Therefore, it becomes necessary to use a large amount of water or increase the operation pressure, and hence, water cannot always be said to be economical.
In this invention, the aqueous acetic acid solution obtained from the methacrylic acid-recovery step may be fed as the absorbing solvent to the mlethacroiein-recovert step through conduit 17, whereby the absorption efficiency can be increased without imparing the convenience in process which water has. In this case, the off-gas effluent from the methacrolein-recovery step 1 6 contains only a slight amount of acetic acid as in Fig. 1, and hence, the loss of acetic acid is small. The off-gas freed from the methacrolein is treated in an off-gas-treating step (not shown in the drawings) to remove completely the organic matters contained in the off-gas, and then released into the air.On the other hand, the methacrolein recovered is recycled through the conduit 1 9 to the oxidation reaction step 2. In said recovered methacrolein are contained acetic acid and/or water, but this is not objectionable in operating the oxidation reaction step. A part of the absorbing solvent may be withdrawn from the conduit 20 and sent to the acetic acidrecovery step 1 3.
Fig. 3 is a flow sheet showing in detail an embodiment of the production of methacrylic acid from isobutylene by two-step oxidation reaction. For simplicity, only major means are shown and heat-exchanger, pumps, vessels and the like are omitted.
The isobutylene oxidation reactor 101 is filled with a catalyst suitable for converting isobutylene to methacrolein, and the methacrolein oxidation reactor 102 is filled with a catalyst suitable for converting methacrolein to methacrylic acid. To the isobutylene oxidation reactor
101 are fed isobutylene via the conduit 21, an oxygen-containing gas via the conduit 22, and an aqueous acetic acid solution, which is the reffinate in the methacrylic acid-extraction tower, after vaporization via the conduit 23. The reaction product gas effluent from the reactor 101, the temperature of which has been controlled so as to fit the subsequent reaction, is fed to the
methacrolein oxidation reactor 102 together with an additional oxygen-containing gas via the conduit 26, and the unreacted methacrolein recovered from the conduit 27.
The reaction product gas effluent from the reactor 102 is fed to the quenching tower 103 via the conduit 29. To the top of the quenching tower 103 is fed to the bottom stream of the quenching tower after cooling via the conduit 30 to quench the reaction product gas, thereby condensing the high-boiling materials such as most of methacrylic acid, acetic acid, water and the like. Further, an aqueous acetic acid solution, which is the reffinate in the methacrylic acid extraction tower 105, is fed to the top of quenching tower 103 via the conduit 31 to absorb methacrylic acid, so that the gas stream discharged from the tower top is substantially freed from methacrylic acid. In the quenching tower 103, there are obtained high-boiling compounds such as methacrylic acid, acrylic acid, acetic acid, water and the like as well as a small amount of methacrolein as the bottom stream.As mentioned above, a part of the bottom stream is recycled to the top of the quenching tower after cooling and the remainder is fed to the methacrolein recovery tower 104 via the conduit 32. Methacrolein is obtained from the top of the methacrolein recovery tower 104 via the conduit 33. Generally, said methacrolein is circulated to the methacrolein oxidation reactor via the conduit 27, but it may also be circulated to a suitable place of the quenching tower depending on the purity of methacrolein. An aqueous solution of methacrylic acid and the like substantially free from methacrolein is obtained from the bottom of the methacrolein recovery tower 104, and said aqueous solution is fed to the methacrylic acid extraction tower 105 via the conduit 34.Although a variety of solvents may be used as extractants for use in the methacrylic acid extraction tower 105, there are preferred those solvents with which acetic acid is not extracted but only methacrylic acid can be extracted.
For example, paraffins, olefins, and cycloaliphatic compounds having 4 or more carbon atoms or aromatic hydrocarbons having 6 or more carbon atoms and halogen derivatives thereof may be used, among which, for example, pentane, hexane, heptane, octane, cyclohexane and the like are preferably used.
In Fig. 3, a case in which pentane is used as the solvent is shown. The operating conditions in the extraction tower may be varied slightly depending on the properties (for example, specific gravity, boiling point, solidifying point and the like) of an extractive solvent, but it is self-evident for those having a general chemical engineering knowledge.
When pentane is used as the extractant, the bottom stream of the methacrolein recovery tower, which is a substance to be extracted, is fed to the top of the extraction tower 105 via the conduit 34, and pentane, which is an extractant, is fed to the bottom of the extraction tower via the conduit 35. It is also possible to feed a small amount of water to the top of the extraction tower via the conduit 38 in order to inhibit to extraction of acetic acid in the methacrylic acid extraction tower 105. As the extraction tower used, there may be used a generally employed extraction tower such as, a packed tower, perforated tray tower, rotary disk tower, and the like, and, in addition, a mixer-settler type extracting means may also be used.
In Fig. 3, a solution of methacrylic acid in pentane is obtained from the top of the extraction tower 1 05, which solution is fed to the subsequent extractant-separating tower 106 via the conduit 36, where the extractant is separated from the methacrylic acid and again recycled to the methacrylic acid extraction tower 105, while the methacrylic acid is fed either to the subsequent purifying step via the conduit 39 or to the subsequent esterifying step without purification, if the final object is to obtain methacrylates.From the bottom of the extraction tower, there is obtained an aqueous acetic acid solution as the reffinate via the conduit 37, a part of which is recycled to the isobutylene oxidation reactor 101 via the conduit 23, another part of which is recycled to the quenching tower 103 via the conduit 31, a further part of which is used as a supplement of the absorbing liquid in the methacrolein-absorbing tower 109 via the conduit 51. The remaining portion of the aqueous acetic acid solution is fed to the acetic acidextraction tower 107 via the conduit 40, where the acetic acid is extracted and recovered. As the extractant used in the acetic acid extraction tower, preferred are extractants having a high extraction efficiency of acetic acid such as esters, ethers, aromatic hydrocarbons, phosphoric esters, or mixtures thereof.As the extraction tower, a generally employed extraction tower such as a packed tower, a perforated tray tower, a rotary disk tower, and the like may be used, and a mixer-settler type extracting means may also be used. In Fig. 3, ethyl acetate is used as the extractant in the acetic acid extraction tower. In this case, the operating conditions of the acetic acid extraction tower may also be varied depending upon the properties of the extractant (e.g.
specific gravity, boiling point, solidifying temperature and the like), though this is self-evident for those having a general chemical engineering knowledge.
When ethyl acetate is used as the extractant, the extractant is fed to the acetic acid extraction tower 107 via conduit 42, and a solution of acetic acid in ethyl acetate is obtained from the top of the extraction tower 107, which solution is fed to the extractant-separating tower 108 via the conduit 41, where the extractant and acetic acid are separated. The extractant is recycled to the extraction tower 107 via the conduit 42 and acetic acid is fed to an acetic acid-purifying step (not shown in the drawings), via the conduit 44.Since the extracted solution discharged from the acetic acid extraction tower via the conduit 43 contains a small amount of ethyl acetate dissolved therein, the extracted solution is subjected to a suitable waste water treatment such as microbial treatment and the like after passing through an ethyl acetate recovery step (not shown in the drawings) and disposed as waste water.
The gas which is not condensed and not absorbed in the quenching tower 103 is discharged from the top via the conduit 45 and fed to the bottom of the methacrolein-absorbing tower 109, where methacrolein is absorbed by the absorbing liquid and recovered. That is to say, if the methacrylic acid reffinate is fed to the methacrolein-absorbing tower 109 via the conduit 46, and the methacrolein-containing gas is fed via the conduit 45 to the methacrolein-absorbing tower 109, to obtain an aqueous acetic acid solution containing methacrolein from the bottom, which solution is fed to the methacrolein stripper 1 10 via the conduit 48 and methacrolein is recovered from the top. The methacrolein recovered from the top via the conduit 49 is further recycled to the oxidation reactor 102 via the conduit 27.In this case, it is objectionable if an aqueous acetic acid solution which is the absorbing solvent is contained in methacrolein, and this means that the operating conditions of a stripper 1 10 for separating easily polymerizable methacrolein can be moderated, and hence its presence is advantageous. The aqueous acetic acid solution from which methacrolein has been separated is recycled to the methacroleinabsorbing tower via the conduit 46. In order to avoid the accumulation of high-boiling impurities, a part of said aqueous acetic acid solution may be fed to the acetic acid extraction tower via the conduit 50, and the reffinate from the methacrylic acid extraction tower in the corresponding amount may be fed to the acetic acid extraction tower via the conduit 51.
A waste gas comprising mainly nitrogen (N2), oxygen (02), carbon monoxide (CO), and carbon dioxide (CO2) is obtained from the top of the methacrolein-absorbing tower 109 and said waste gas is generally discharged to the air after waste-gas treatment. If necessary, it is also possible to supply said waste gas as a diluent gas to an isobutylene oxidation reaction 101, and a methacrolein oxidation reactor 1 02.
The present invention will be illustrated in detail below referring to Examples. However, said
Examples are by way of illustration and not by way of limitation.
Example 1
The apparatus shown in Fig. 3 was used. (However, the acetic acid extraction tower 107 and the extractant-separating tower 108 were not operated.)
The reactor 101 consisted of a pipe made of SUS 304 having an inner diameter of 18 mm and filled with 450 ml of an isobutylene oxidation reaction catalyst (composition: Mo,OBi1Co- 7Fe2sSbaOx), and heated to 350"C in a molten salt bath.
The reactor 102 consisted of a pipe made of SUS 304 having an inner diameter of 23 mm and was filled with 1 550 ml of a methacrolein oxidation reaction catalyst (composition: Mo12P1.5Zr1V0.25Cs2Mn0.125O), and heated to 320"C in a molten salt bath.
To the reactor 101 were fed as reaction raw materials isobutylene at a rate of 0.1 35 kg/hr from the conduit 21, air at a rate of 0.834 kg/hr from the conduit 22, and the bottom stream of methacrylic acid extraction tower obtained from the conduit 37 after vaporization at a rate of 0.334 kg/hr from the conduit 23. The composition of the reaction raw materials was as follows in terms of molar ratio: isobutylene : air : acetic acid : water = 5.0: 60.0: 1.5 : 33.5, and the feed rate of the reaction raw materials was 2400 hr-' (NTP) based upon the isobutylene oxidation catalyst.To the gas leaving the reactor 101 were added air at a rate of 0.185 kg/hr from the conduit 26 and methacrolein recovered from the reaction product at a rate of 0.037 kg/hr from the conduit 27, and the mixed gas obtained was supplied to the reactor 102 via the conduit 28. The reaction product gas from the reactor 102 was fed to the bottom of the quenching tower 103 having an inner diameter of 5 cm and a height of 120 cm filled with
Raschig rings. To the top of the quenching tower was fed the bottom stream of the methacrylic acid extraction tower at a rate of 0.075 kg/hr via the conduit 31 after cooling to 5"C, while the bottom stream of the quenching tower cooled to 5 C was recycled via the conduit 30.The bottom stream of the quenching tower was treated in the methacrolein recovery tower 104 having an inner diameter of 4 cm and a height of 100 cm filled with heripacks to remove methacrolein and then fed to the top of the methacrylic acid extraction tower 105 (a rotary multiplate tower having a diameter of 4 cm and a height of 1 50 cm; number of plates: 40) via the conduit 34. To the extraction tower were fed n-peutane at a rate of 0.721 kg/hr via the conduit 35 and water at a rate of 0.013 kg/hr via the conduit 38, to extract methacrylic acid.
(the extraction tower was operated at 37"C at a top pressure of 1 kg/cm2G). An aqueous acetic acid solution was obtained as the bottom stream of the methacrylic acid extraction tower from the conduit 37 at the lower part of the extraction tower, and a part of the solution was recycled to the reactor 101 and the quenching tower 103.
The gas effluent from the top of the quenching tower 103 was fed to the methacroleinabsorbing tower 109 having an inner diameter of 5 cm and a height of 1 20 cm filled with
Raschig rings via the conduit 45. To the top of the absorbing tower was fed an aqueous acetic acid solution cooled to 3"C at a rate of 2.89 kg/hr via the conduit 46, and the absorption of methacrolein was carried out therein. Waste gas was withdrawn from the conduit 47. The bottom stream of the absorbing tower 109 was fed to the methacrolein stripper 110 having an inner diameter of 5 cm and a height of 1 20 cm filled with heripacks, where methacrolein was recovered.Methacrolein from the conduit 33 was added to the thus recovered methacrolein, and the resulting mixture was recycled to the methacrolein oxidation reactor 102 and the bottom stream of the methacrolein stripper was recycled to the methacrolein-absorbing tower 109.
The composition and flow rate of each part at the time when the entire system became in the steady state were as shown in Table 1.
Table 1 Composition of each stream in Example 1
Stream 24 25 28 29 45 36 37 46 47 49 40 Inorganic gas 63.9 58.6 62.1 60.5 95.8 0 0 0 99.09 0 Water 22.4 26.9 23.1 24.0 0.8 86.8 0.1 87.0 0.79 2.1 86.8 Acetic acid 3.3 3.1 2.6 3.6 0.1 0 12.7 13.0 0.05 0 12.7 Composi- Isobutylene 10.4 0.4 0.4 0 0 0 0 0 0 0 0 tion (% by weight) Methacrolein 0 10.2 10.9 2.3 3.0 0 0 0 0.06 89.2 0 Methacrylic acid 0 0.3 0.3 9.0 0 15.7 0 0 0 0 0 n-Pentane 0 0 0 0 0 83.6 0.1 0 0 0 0.1 Others 0 0.5 0.6 0.6 0.3 0.6 0.4 0 0.01 8.7 0.4 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Flow rate (kg/hr) 1.30 1.30 1.53 1.53 0.958 0.863 0.500 2.89 0.929 0.032 0.091 Comparative Example 1
The same catalyst and experimental equipment as in Example 1 were used.The same experiment as in Example 1 was repeated, except that the bottom stream of the methacrylic acid extraction tower was recycled to neither of the reactor nor the quenching tower, instead of which water was fed, after vaporization, at a rate of 0.304 kg/hr via the conduit 23 and further water was fed at a rate of 0.072 kg/hr to the quenching tower via the conduit 31, and that xylene was fed to the methacrolein-absorbing tower 109 at a rate of 2.89 kg/hr in place of the aqueous acetic acid solution.
As the xylene fed to the methacrolein-absorbing tower 109, there was used the xylene obtained by re-distilling (not shown in the drawings) the bottom stream of the methacrolein stripper 1 10 to remove acetic acid, methacrylic acid and the like.
The material balance at the time when the operation became the steady state is shown in
Table 2.
It can be seen that the acetic acid concentration in the gas at the outlet (conduit 29) of the
reactor 102, the acetic acid concentration in the bottom stream (conduit 37) of the methacrylic acid extraction tower and the acetic acid concentration in the feed (conduit 40) to the acetic acid
extraction tower (107) were lower than those in Example 1. It can also be found that the waste
gas withdrawn from the top conduit 47 of the methacrolein-absorbing tower 109 contained a
large amount of xylene, which became the loss from the methacrolein system.
Table 2 Concentration of each stream in Comparative Example 1
Stream 24 25 28 29 45 36 37 46 47 49 40 Inorganic gas 65.5 60.0 63.0 61.3 95.60 98.2 Water 23.9 28.4 24.6 25.5 0.82 95.1 0.9 95.4 Acetic acid 0.4 0.3 1.4 0.01 4.4 0.01 4.1 Composition Isobutylene 10.6 0.4 0.3 0 0 (% by weight) Methacrolein 10.4 11.2 2.3 3.22 0.05 0.03 91.07 Methacrylic acid 0.3 0.3 9.2 15.73 0.01 n-Pentane 0 0 0 0 84.21 0.1 0.1 Xylene 0 0 0 0 99.95 0.9 0.05 Others 0.1 0.3 0.3 0.31 0.01 0.4 8.88 0.4 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Flow rate (kg/hr) 1.27 1.27 1.47 1.47 0.940 0.855 0.471 2.89 0.914 0.032 0.471 Example 2
The same catalyst and experimental equipment as in Example 1 was used.The same experiment was repeated, except that water was fed to the quenching tower 103 at a rate of 0.072 kg/hr via the conduit 31 and that the bottom stream of the methacrylic acid extraction tower 105 was not recycled to the quenching tower and that xylene was fed to the methacrolein-absorbing tower 109 at a rate of 2.89 kg/hr in place of the aqueous acetic acid solution.
The xylene fed to the methacrolein-absorbing tower 109 was obtained by subjecting the bottom stream of the methacrolein stripper 1 10 to re-distillation (not shown in the drawings), thereby removing most of acetic acid, methacrylic acid and the like.
The material balance at the time when the operation became the steady state is shown in
Table 3.
It can be seen from Table 3 that the gas concentration at the outlet (conduit 29) of the reactor (102), the acetic acid concentration in the bottom stream (conduit 37) of the methacrylic acid extraction tower 105 and the acetic acid concentration in the feed (conduit 40) to the acetic acid extraction tower are higher than those in Comparative Example 1.
Table 3 Composition of each stream in Example 2
Stream 24 25 28 29 45 36 37 46 47 49 40 Inorganic gas 64.6 59.2 62.7 60.8 95.6 98.2 Water 22.9 27.6 23.5 24.6 0.8 91.6 0.9 91.6 Acetic acid 2.0 1.8 1.6 2.6 8.0 0.01 8.0 Isobutylene 10.5 0.4 0.4 0 Composi- Methacrolein 10.3 10.8 2.3 3.1 0.03 85.1 tion (% by Methacrylic acid 0.3 0.3 9.0 15.7 0.01 weight) n-Pentane 83.8 0.1 0.1 Xylene 99.95 0.9 0.9 Others 0.4 0.7 0.7 0.5 0.5 0.3 14.0 0.3 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Flow rate (kg/hr) 1.29 1.29 1.51 1.51 0.959 0.862 0.488 2.89 0.932 0.034 0.154 Example 3
The same catalyst and experimental equipment as in Example 1 were used.
The same procedure as in Example 1 was repeated, except that xylene was fed to the methacrolein-absorbing tower 109 at a rate of 2.89 kg/hr in place of the aqueous acetic acid solution.
The xylene fed to the methacrolein-absorbing tower 109 was obtained by subjecting the bottom stream of the methacrolein stripper 1 10 to re-distillation (not shown in the drawings), thereby removing most of acetic acid, methacrylic acid and the like.
The material balance at the time when the operation became the steady state is shown in
Table 4.
Table 4 Composition of each stream in Exanmple 3
Stream 24 25 28 29 45 36 37 46 47 49 40 Inorganic gas 63.8 58.7 62.3 60.6 95.8 0 0 98.6 Water 22.4 26.8 22.9 23.9 0.8 0.1 86.8 0.8 86.8 Acetic acid 3.3 3.1 2.6 3.6 0.1 0 12.7 0.1 12.7 Composi- Isobutylene 10.4 0.4 0.4 0 0 0 0 0 tion (% by Methacrolein 10.2 10.9 2.3 3.0 0 0 90.7 0 weight) Methacrylic acid 0.3 0.3 9.0 0 15.7 0 0 n-Pentane 83.6 0.1 0.1 Others 0.1 0.5 0.6 0.6 0.3 0.6 0.4 8.4 0.4 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Flow rate (kg/hr) 1.30 1.30 1.53 1.53 0.958 .864 0.500 2.89 0.934 0.031 0.091 Example 4
The same catalyst and experimental equipment as in Example 1 were used. The same procedure as in Example 1 was repeated, except that vaporized water was fed to the reactor at a rate of 0.30 kg/hr via the conduit 23 and that xylene was fed to the methacrolein-absorbing tower 109 at a rate of 2.89 kg/hr in place of the aqueous acetic acid solution.
The xylene fed to the methacrolein-absorbing tower 109 was obtained by subjecting the bottom stream of the methacrolein stripper 1 10 to re-distillation (not shown in the drawings), thereby removing most of acetic acid, methacrylic acid and the like.
The composition and flow rate in each part at the time when the operation became substantially steady are shown in Table 5.
Table 5 Composition of each stream in Example 4
Stream 24 25 28 29 45 36 37 46 47 49 40 Inorganic gas 65.5 59.9 62.9 61.1 95.8 0 0 98.5 Water 23.9 28.5 24.7 0.8 0 94.2 0.8 94.2 Acetic acid 0.4 0.3 1.4 0.1 0 5.2 5.2 Composi- Isobutylene 10.6 0.4 0.3 0 0 0 tion (% by Methacrylein 10.4 11.2 2.3 3.1 0 weight) Methacrylic acid 0.3 0.3 15.7 n-Pentane 0 0 0 84.2 0.1 0.1 Xylene 0 0 0 99.9 0.6 0.9 Others 0.1 0.3 0.4 0.2 0.4 8.3 0.4 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Flow rate (kg/hr) 1.27 1.27 1.47 1.47 0.938 0.858 0.463 2.89 0.912 0.388
Claims (17)
1. A process for producing methacrylic acid by the gas phase catalytic oxidation of one or more or the gases isobutylene, t-butanol, methacrolein, isobutyraldehyde and isobutyric acid with molecular oxygen, quenching the gaseous product from the oxidation, and recovering the methacrylic acid produced, in which at least part of the aqueous acetic acid solution formed as a by-product of said oxidation is recycled to one or both of the oxidation and the quenching.
2. A process according to claim 1, in which part of said by-product aqueous acetic acid solution is recycled only to the oxidation.
3. A process according to claim 1, in which part of said by-product aqueous acetic acid solution is recycled only to the quenching.
4. A process according to claim 1, in which part of said by-product aqueous acetic acid solution is recycled to both the oxidation and the quenching.
5. A process according to any one of the preceding claims, in which the oxidation reaction is a 2-step oxidation reaction.
6. A process according to any one of claims 1, 2, 4 and 5, in which the proportion of byproduct aqueous acetic acid solution recycled to the oxidation is such that the molar ratio of acetic acid to the starting gas is from 1 to 30.
7. A process according to claim 6, in which said molar ratio is from 1 to 20.
8. A process according to any one of claims 1, 3 and 4, in which the proportion of said aqueous acetic acid solution recycled to the quenching is such that the weight ratio of the solution tithe oxidation reaction product gas is from 0.001 to 1.0.
9. A process according to claim 8, in which said molar ratio is from 0.01 to 0.30.
10. A process according to any one of the preceding claims, in which the molar ratio of the starting gas to oxygen is from 0.5 to 20.
11. A process according to any one of the preceding claims, in which the oxidation is effected at a temperature of from 200"C to 500"C.
1 2. A process according to any one of the preceding claims, in which the starting gas is fed at a space velocity of from 100 to 8,000 reciprocal hours (NTP standard).
1 3. A process according to any one of the preceding claims, in which the process is operated as a continuous process.
1 4. A process according to claim 13, in which part of the aqueous acetic acid solution is recovered from the process cycle.
1 5. A process according to claim 1, substantially as hereinbefore described with reference to any one of the foregoing Examples.
1 6. Methacrylic acid when produced by a process according to any one the preceding claims.
17. An aqueous acid solution when obtained by a process as claimed in claim 14.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2994081A JPS57144237A (en) | 1981-03-04 | 1981-03-04 | Preparation of methacrylic acid |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2096601A true GB2096601A (en) | 1982-10-20 |
| GB2096601B GB2096601B (en) | 1985-03-20 |
Family
ID=12289981
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8206428A Expired GB2096601B (en) | 1981-03-04 | 1982-03-04 | Process for producing methacrylic acid |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS57144237A (en) |
| GB (1) | GB2096601B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0289178A1 (en) * | 1987-04-16 | 1988-11-02 | Nippon Shokubai Kagaku Kogyo Co., Ltd | Process for producing methacrylic ester |
| WO1999050222A1 (en) * | 1998-03-31 | 1999-10-07 | Basf Aktiengesellschaft | Method for producing acrylic acid and acrylic acid esters |
| CN110903184A (en) * | 2018-11-14 | 2020-03-24 | 住友化学株式会社 | Apparatus for producing methacrylic acid |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01142357U (en) * | 1988-03-25 | 1989-09-29 | ||
| JP5691252B2 (en) * | 2010-06-10 | 2015-04-01 | 三菱レイヨン株式会社 | Method for producing heteropolyacid catalyst for production of methacrylic acid, and method for producing methacrylic acid |
| KR20140064861A (en) * | 2011-09-16 | 2014-05-28 | 에보니크 룀 게엠베하 | Process for preparation of methacrylic acid and methacrylic acid esters |
| CN103796982B (en) * | 2011-09-16 | 2015-10-14 | 赢创罗姆有限公司 | The preparation method of methacrylic acid and methacrylic ester |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5821896B2 (en) * | 1975-03-10 | 1983-05-04 | 株式会社日本触媒 | High Suino Riyouhouhou |
| JPS5353613A (en) * | 1976-10-26 | 1978-05-16 | Nippon Zeon Co Ltd | Preparation of methacrylic acid |
| US4092132A (en) * | 1977-09-06 | 1978-05-30 | Halcon Research And Development Corp. | Recovery of methacrolein |
| JPS5821896A (en) * | 1981-07-31 | 1983-02-08 | ソニー株式会社 | Method of mounting electronic part |
-
1981
- 1981-03-04 JP JP2994081A patent/JPS57144237A/en active Granted
-
1982
- 1982-03-04 GB GB8206428A patent/GB2096601B/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0289178A1 (en) * | 1987-04-16 | 1988-11-02 | Nippon Shokubai Kagaku Kogyo Co., Ltd | Process for producing methacrylic ester |
| US4956493A (en) * | 1987-04-16 | 1990-09-11 | Nippon Shokubai Kagaku Kogyo Co., Ltd. | Process for producing methacrylic ester |
| WO1999050222A1 (en) * | 1998-03-31 | 1999-10-07 | Basf Aktiengesellschaft | Method for producing acrylic acid and acrylic acid esters |
| CN110903184A (en) * | 2018-11-14 | 2020-03-24 | 住友化学株式会社 | Apparatus for producing methacrylic acid |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6312458B2 (en) | 1988-03-18 |
| JPS57144237A (en) | 1982-09-06 |
| GB2096601B (en) | 1985-03-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4504692A (en) | Process for producing 1,3-butadiene | |
| EP1773748B1 (en) | Method for producing (meth)acrylic acid | |
| US6639106B1 (en) | Process for preparing and purifying acrylic acid from propylene having improved capacity | |
| US4066706A (en) | Preparation of ethylbenzene hydroperoxide | |
| JP2007518736A (en) | Method for purifying olefinically unsaturated nitriles | |
| EP0523728A2 (en) | Continuous process for preparing dimethyl carbonate | |
| EP1716095B1 (en) | Method for producing (meth)acrylic acid | |
| JP4222815B2 (en) | Extraction method for recovering acrylic acid | |
| US5248819A (en) | Process for recovering methacrolein | |
| KR20020084899A (en) | Process for producing methyl methacrylate | |
| KR101052710B1 (en) | (Meth) acrylic acid purification method obtained by oxidation of base material | |
| GB2096601A (en) | Process for producing methacrylic acid | |
| CN1390190A (en) | Method for purifying acrylic acid obtained by oxidation of propylene and/or acrolein | |
| US5534648A (en) | Process for continuously producing dimethyl carbonate | |
| US3741993A (en) | Maleic anhydride process | |
| US4623432A (en) | Removal of brominated organics from acetic acid obtained by oxidation of liquid butane in presence of Co-Br or Co-Mn-Br system catalysis | |
| JPS6310691B2 (en) | ||
| JPS6056127B2 (en) | Acetic acid recovery method | |
| JPS6348857B2 (en) | ||
| JPH0834757A (en) | Purification of acrylic acid | |
| JP2003192627A (en) | Method for producing methacrolein | |
| JPH0372209B2 (en) | ||
| JPS60174733A (en) | Preparation of 1,3-butadiene | |
| JPH03176439A (en) | Recovering of isobutane and methacrolein | |
| WO1989005788A1 (en) | Process of recovering and esterifying maleic anhydride |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |