CS212931B1 - A method for producing methacrylic acid esters and a device for making it - Google Patents

Abstract

The invention relates to a method and a device for the production of methacrylic acid esters. According to the invention, methacrylic acid esters are produced from methacrylamide sulfate, alcohol and water in the presence of sulfuric acid and a polymerization inhibitor in a device consisting of 1 to 6 reactors and a diameter to height ratio of 0.12 to 0.32. A hydrophobic extraction solvent is added to the reaction mixture in an amount of 0.5 to 3 times the volume of the reaction mixture itself, while the system is stirred with a stirrer with 5 to 10 blades placed one above the other without the two phases intermixing. The temperature of the organic phase is maintained at 70 to 110 ° C, the temperature of the aqueous phase at 80 to 150 ° C and the individual phases are continuously removed.

Description

The present invention relates to a process and an apparatus for the production of methacrylic acid esters.

The methacrylic acid esters of the present invention are prepared from methacrylamide sulfate, alcohol and water in the presence of sulfuric acid and a polymerization inhibitor in an apparatus of 1 to 6 reactors and a diameter to height ratio of 0.12 to 0.32. The hydrophobic extraction solvent is added to the reaction mixture in 0.5 to 3 times by volume to the reaction mixture itself, while mixing the system with a 5 to 10 paddles placed one above the other without overlapping the two phases. The temperature of the organic phase is maintained at 70 to 110 ° C, the temperature of the aqueous phase is at 80 to 150 ° C, and the phases are continuously removed.

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The invention provides a process for the production of methacrylic acid esters from methacrylamide sulphate by means of a suitable apparatus.

Methacrylic acid esters can be prepared by conventional methods. Industrial production ea is based almost exclusively on a process starting from acetone cyanohydrin (AKH). Acetone cyanohydrin aa in the presence of concentrated sulfuric acid stems at most methacrylamine sulphate, which in a later stage by eaterification in the presence of alcohol and water gives the methacrylic acid alkyl ester Zilbermann E.N., Ifisurin A.A. prihl.chim. 4P, 122 (1967). Industrially, the most important is the production of methacrylic acid methyl ester, which is the starting monomer for the preparation of block and suspension polymers and copolymers. Regarding the yield of the final product of the technology, in the case of methanol eeterification, the second stage of the synthesis, the process of esterification of methacrylamide sulphate, is crucial. This is done in a discontinuous and continuous arrangement. The discontinuous systems operate by adding methacrylamide sulfate dissolved in sulfuric acid, methanol, water, or a suitable polymerization inhibitor into the boiler e. Continuous methods of etherification work in a cascade in the knee, in the mixed rectors or in the reactors. The esterification mixture is passed through individual SiC cascades and, after a suitable conversion e and e, the methacrylic acid ester is displaced by water vapor (U.S. Pat. No. 84,213) may also be distilled directly from the reaction mixture. A mixture of alcohol and water springs (No. 152 224) emerges, and the ester itself undergoes additional finishing operations, and the habit is drained from the boil.

The esterification may also be carried out in a two-phase system in the presence of a hydrocarbon solvent e.g. in hexane (Jap. pat. 71-17205), or in the presence of aromatics such as xylene and cumene (Jap. pat. 74-86318). The flow system ea is also realized by the fact that in the countercurrent reactor from the upper part an eaterification mixture (methacrylamide sulphate, alcohol, water, sulfuric sulfur) enters the countercurrent (Ss. Pat. 123 247).

These methods of performing methacrylate synthesis have some disadvantages. By direct distillation of the ester from the reaction mixture, the cascade member heats the reaction mixture mainly, resulting in polymers that reduce the yield and cause technological difficulties, mainly in the part of the waste sulphate waste treatment. When using water vapor isolation of the methacrylic acid ester, the process is energy intensive and also generates some polymer by-products. In both of these examples, ea produces a crude ester which contains, in the case of methyl methacrylate production, mainly methanol, science, methacrylic acid. The methacrylic acid is first neutralized, the methanol is extracted and the product is distilled only in the next phase. These operations are sensitive to the manner of stabilization. Ineffective stabilization can result in copolymerization of part of the device.

Speoifical problems also arise from column synthesis. Columns are polymerized, the main reaction takes place in the boiler, it is difficult to keep

212 B31 optimal synthesis temperature.

The main disadvantage of the methods used is the relatively low product yield due to the formation of polymers, mainly due to the polymerization of methacrylic acid and alkali metal methacrylene through which it separates from methacrylic acid.

The above-mentioned disadvantages are overcome by the process according to the invention, wherein the process for producing methacrylic acid ethers from methacrylamide sulphate by treating a solution of 1 to 8 carbon atoms and 1 to 8 carbon atoms with a molar ratio of 1: 1 to 2: 1 to 6 is present. by adding to the reaction mixture a hydrophobic extraction solvent in a volume of 0.5 to 3 times by volume to a reaction mixture selected from paraffinic hydrocarbons having from 6 to 12 carbon atoms, preferably a light distillation cut and / or aromatic Hydrocarbons having from 6 to 12 carbon atoms, preferably pyrolysis naphtha and deacidification slices thereof, and esters of dicarboxylic acid having a temperature of at least 10 ° C higher than the resulting methacrylic acid ester, the mixture being mixed without phase and phase temperature aa maintained at 70-110 ° C and the aqueous phase temperature at 8 0 to 150 ° C and the phases are continuously removed.

Apparatus for the production of methacrylic acid ethers consisting of a reactor or a cascade of reactors in series, as well as the associated fittings. and measuring and control instruments, consisting of 1 to 6 reactors with a diameter of 0,12 to 0,32, each reactor being equipped with a β5 to 10 blades placed over one another, with outlets located above the interface at the level of the interface. organickoj: phases and below the level of the phase interface are situated outlets of the aqueous phase.

An advantage of the present invention is that the recovery of the selective solvent simplifies the method of the ester separation. The reaction layer contains at most 1 wt. % higher molecular weight by-products, 1 to 2 wt. % methyl methacrylate, 5 to 6 wt. methanol, water, ammonium hydrogen sulphate, sulfuric acid, methoxyeulfonic acid. The backsheet may and preferably be treated to ammonium sulfate. In the case of the preparation of methacrylic acid ethers and higher alkchols, aa refers to the corresponding alcohol and ester. Used !

the reactors have a diameter to height (d / l) ratio of 0.118 to 0.320. The stirrer is equipped with 5 to 10 blades one above the other and a speed of 400 to 700 rpm · This mode ensures stable stratification on the reaction and extraction layers. The number of cascade members is selected according to the reaction rate and, depending on the alcohol used, the esterification of methacrylamide sulfate. The volume is then determined by a reaction time of aa ranging from 120 to 200 min. As extraction hydrophobic solvent, aliphatic hydrocarbons such as e.g. n-hexane, n-heptene and higher hydrocarbons or a mixture thereof, e.g. pyrolysis gasoline (m.p. 160-220 ° C), paraffinic paraffin oil, alkyl aromatics and higher phthalic acid esters. The process for producing methacrylic acid ethers according to the invention has several advantages. The reaction mixture is less thermal

212 931 stressed and despite the fact that β-monomer is being used, polymer by-products are substantially reduced in the lower range, reducing the costs of cleaning the separators and also the number of production interruptions. The costs of purification of the crude ester are also reduced, and the solution of the ether in an elective solvent can be conveniently separated by rectification. a more violent advantage of the process is that it is also possible to isolate methacrylic acid, which can be used for saler application. This is an advantage with respect to some technologies in which methacrylic acid will melt, due to its susceptibility to polymerization when it is removed from the reaction mixture prior to isolating the ester. The following examples describe the process of the present invention.

Example 1

The reaction mixture prepared from 1 mole of methacrylamide sulphate, 0.5 mole of sulfuric acid (this time obtained from acetone-anhydride and sulfuric acid), to which 1.6 mole of methanol and 4 moles of water (stabilized with 0.1% hydroquinone) was added continuously. the central portion of the first three-member cascade reactor. Light petrol (b. 180 to 220 ° C) stabilized with 0.1 wt. 2,6-Diterebutyl cresol (DTBK) in an amount of 0.35 volume of the reaction mixture. At a stirrer speed of 400 rpm, a stable interface is formed between the reaction and extraction layers, the position of which is controlled by level gauges. The temperature of the heating medium in the jacket is maintained at 120 ° C, the temperature of the reaction layer at 90 to 100 ° C. A solution containing 45% by weight of the last cascade member is removed from the stomach. % methyl methacrylate and 50 wt. methacrylic acid (MAK). These components are separated from the solvent by rectification. Sulphate liquors are separated from the bottom of the last Klen of the cascade and contain about 1% by weight. methyl methacrylate and 5% unreacted methanol. The yield of methyl methacrylate for the methacrylamide used was 85 wt.

Example 2

The starting esterification mixture has the composition as in Example 1. This, together with the selective solvent, which is kerosene, in an amount of 0.42 volumes per starting material (withdrawal of 0.1% PTBK) is injected into a reactor whose diameter to length is 0,320. The stirrer speed is 5Q0. Reactor jacket temperature 120 ° C. The reaction time is 180 min. The top layer (kerosene) contains 50 wt. % methyl methacrylate and 7.7 wt. methacrylic acid. The backsheet contains 1.1% methyl methacrylate, 4.5% methanol and 1% polymers. The reaction yield is 86% by weight.

Example 3

The esterification reaction mixture contains 1 mole of methacrylamide sulfate, 0.8 mole of sulfuric acid, 2 mole of butanol, 4 mole of water. The stabilized mixture of 0.01% hydrochlorinone was added

Z1Z> 31 is continuously fed into the central part of the four-member cascade together with a raactive solvent, such as dioctyl phthalate, stabilized with 0.01% DTBK in an amount of 0.28 volumes per incoming feed. The temperature of the heating grip in the jacket is maintained at 120 ° C. A solution of matyl methacrylate (42% by weight) and kya are removed from the sweetened cascade member. methacrylic (6.8 wt.%) in dioctyl phthalate. This mixture aa ripped onto the rectal glass. The ester yield is 82% on methacrylamide.

Example 4

Reaction mixture consisting of 1 mole of methacrylamide sulphate, 0,3 mole of sulfuric acid,

1.8 moles of octanol and 4 moles of water (stabilized with 0.01% w / w pyrocataehin) are fed into the central part of the 6-member cascade reactor together with a solvent containing paraffin oil (stabilized with 0.01% DTBK) in an amount of 0.45 parts from the feed volume of the reactants. The solvent aa dosed into the top of the reactor * The temperature of the heating grinder aa was maintained at 150 ° C. From the last member of the cascade, octyl methacrylate (40% by weight), methacrylic acid (7.1% by weight) in paraffin oil are taken. Zmaa aa led to rectification spraying. The yield of octyl methacrylate on the starting amide is 80% by weight.

Claims (2)

No. 4,212,231 does not continually enter the central part of the four-member cascade together with the reactive solvent, which is dioctyl phthalate, stabilized with 0.01% DTBK in an amount of 0.28 vial to feed the feedstock. The temperature of the heating medium in the jacket and maintained at 120 ° C. A methyl methacrylate solution (42% by weight) and kye is removed from the last cascade member. non-acrylic (6.8 wt.%) in dioctylphthalate. This mixture and next to the rectifier. The ester yield is 82% to methacrylamide. EXAMPLE 4 A reaction mixture consisting of 1 mole of methacrylamide sulfate, 0.3 mole of sulfuric acid, 1.8 mole of octanol and 4 mols of water (stabilized with 0.01% w / w pyrocateehine) is dosed in one central portion of the 6-membered cascade reactor together with a solvent which is paraffin oil (stabilized with 0.01% DTBK) in an amount of 0.45% by volume of the reaction components. The solvent is metered into the top of the reactor. The temperature of the heated butter is maintained at 150 ° C. octyl methecrylate (40% by weight), methacrylic acid (7.1% by weight) in paraffin oil is taken from the last cascade member. The mixture is next to the rectification process. The yield of octyl methacrylate on the starting amide is 80% by weight. SUBJECT OF THE INVENTION A process for the preparation of methacrylamide sulphate esters of non-acrylic acid by treating a 1: 8 to 2: 1 to 6 solution of an alcohol of 1 to 8 carbon atoms and a sulfuric acid inhibitor and a polymorph inhibitor, indicating and by reacting to the reaction. The hydrophobic dissolving solvent is added in a 3 to 3-fold volume to the actual reaction mixture, selected from paraffinic hydrocarbons having from 6 to 12 carbon atoms, and preferably their de-reductive and / or aromatic hydrocarbons having from 6 to 12 carbon atoms. carbon ethoxy, preferably gasoline from pyrolysis and their distillation, and esters of dicarbonic acid having a boiling point of at least 10 ° C, such as having a methacrylic acid ester, adhere to the system without the intersection of the two phases and the temperature of the organic phase being maintained at 70-110 ° C and the temperature of the aqueous phase at j80 to 150 ° C and the individual phases are continuously removed Jun. 2. Alignment for the process of step 1, consisting of a reactor or cascade reactors connected serially as well as servicing fittings and measurement and control devices, characterized in that it consists of 1 to 6 reactors with a diameter to nutrient ratio of 0.12 to 0.32, each the reactor is provided with a reservoir having 5 to 10 blades positioned one above the other, the organic phase outlets of the individual reactors are situated above the level of the phase interface and outlets are situated below the phase interface; aqueous phase.