EP2054370A1

EP2054370A1 - Integrated process and apparatus for preparing esters of methacrylic acid from acetone and hydrocyanic acid

Info

Publication number: EP2054370A1
Application number: EP07803110A
Authority: EP
Inventors: Udo Gropp; Robert Weber; Thomas Schäfer; Andreas Perl; Rudolf Sing; Thomas Mertz
Original assignee: Evonik Roehm GmbH
Current assignee: Evonik Roehm GmbH
Priority date: 2006-12-08
Filing date: 2007-08-31
Publication date: 2009-05-06
Also published as: KR20090096450A; JP2010511651A; TW200835680A; BRPI0719692A2; WO2008068064A1; US20100069662A1; MX2009005895A; AU2007327788A1; DE102006058250A1; RU2009125683A; CN101195574A

Abstract

The subject-matter of the present invention relates in principle to a process for preparing alkyl esters of methacrylic acid, comprising at least the following steps: preparing acetone cyanohydrin from hydrocyanic acid and acetone in a first step, purifying the acetone cyanohydrin in a second step, preparing methacrylamide from acetone cyanohydrin in a third step, esterifying a reaction mixture comprising methacrylamide and at least one alkyl alcohol in the presence of a mixture of water and sulphuric acid to give alkyl methacrylates in a fourth step, and purifying the alkyl methacrylate in at least one further step, and also to an apparatus for performing this process.

Description

INTEGRATED METHOD AND DEVICE FOR PREPARING METHACRYLIC ACID ESTERS FROM ACETONE AND BLUE ACID

The subject matter of the present invention relates generally to a process for the preparation of alkyl esters of methacrylic acid and its secondary products which can be used in a variety of chemical synthesis processes which can lead to a wide variety of further processing products, and to an apparatus for carrying out this process.

From the prior art, a variety of methods for the production of methacrylic acid esters is known. The problem with many of these methods is that a large number of material streams within the scope of the production process leaves the process sequence and thus has to be subjected to a complex and often expensive after-treatment. Often, such streams must be disposed of as waste, which can often lead to additional costs. Apart from the aftertreatment costs or the disposal costs or both, the known processes frequently result in the problem that potential reactants are withdrawn from the process and thus in principle valuable valuable raw materials are wasted or the adjustment of a stoichiometry conducive to the process is made more difficult.

In principle, this results in an object according to the invention of at least partially alleviating or even overcoming the disadvantages resulting from the prior art.

In particular, it was an object of the invention to provide a process which permits the largest possible utilization of the material streams occurring in the context of the process. In addition, an object of the invention was to provide a device for To provide that allows implementation of the method according to the invention.

Summary of the invention

The objects underlying the invention are achieved by a process for the preparation of alkyl esters of methacrylic acid, which comprises at least the following steps:

- producing acetone cyanohydrin from hydrocyanic acid and acetone in a first step,

Cleaning the acetone cyanohydrin in a second step,

- Preparation of methacrylamide from acetone cyanohydrin in a third step, - Esterification of a Methacrylsäureamid and at least one alkyl alcohol-containing reaction mixture in the presence of a mixture of water and sulfuric acid to alkyl methacrylate in a fourth step and

- Purification of the methacrylic acid alkyl ester in at least one further step.

In a further embodiment of the invention, the acetone cyanohydrin can be freed in a rectification column, for example at least from impurities having a boiling point of more than about -5 ⁰ C and less than about 100 ⁰ C, these impurities are attributed to the reaction for the preparation of acetone cyanohydrin can. In the production of methacrylamide resulting gaseous products can be introduced into the reaction mixture of the esterification.

In addition, it may be advantageous in the context of the present invention if the methacrylic acid alkyl ester formed in the esterification of methacrylamide with at least one alkyl alcohol is Washed water and the wash water obtained after washing is returned to the esterification process. The mixture of water and sulfuric acid and optionally further substances from the esterification can be freed, for example, first by means of flotation of solids and optionally additionally subsequently cooled. The cooling can be carried out in heat exchangers and the mixture of water and sulfuric acid and optionally other substances from the esterification in the heat exchanger can be mixed with the washing water obtained in the washing of Methacrylsäurealkylesters with water.

It may also be advantageous if the entry of the wash water in the heat exchanger takes place such that the inner surfaces of the heat exchanger are at least partially wetted with the wash water during operation. The entry of the wash water into the heat exchanger can be carried out according to the invention, for example, such that during operation are not permanently wetted with the mixture of water and sulfuric acid and optionally other substances from the esterification in contact inner surfaces of the heat exchanger with the wash water.

In a further embodiment of the invention, the formed methacrylic acid alkyl ester of a pre-cleaning and a

Main cleaning be subjected. In the pre-cleaning, if a two-stage cleaning is to take place, for example, substances can be separated, which have a lower boiling point than the methacrylic acid alkyl ester. In the main cleaning, for example, substances can be separated, which have a higher boiling point than the methacrylic acid alkyl ester. It may, for example, have advantageous effects if substances are separated in the pre-purification, which have a lower boiling point than the alkyl methacrylate and these substances are then condensed by cooling, leaving non-condensed residues in the gas phase and in the

Hauptreinigung substances are separated, which have a higher boiling point than the alkyl methacrylate and this is condensed by cooling, leaving non-condensed residues in the gas phase and not condensed gaseous residues from the pre-cleaning and non-condensed gaseous residues from the main purification of a common post-condensation are subjected. A condensate obtained during the joint after-condensation can then be subjected to a phase separation within the scope of a further embodiment of the invention, it being possible for an aqueous phase and an organic phase to form. It can then be in

Within the scope of the present process, in a further embodiment of the invention, the process is carried out such that the aqueous phase is at least partially recycled to the esterification or the organic phase is returned to the pre-purification or both.

If a process according to the invention is carried out in the context of an integrated plant with a device for splitting sulfuric acid, it may be advantageous if the mixture of water and sulfuric acid is optionally introduced together with other substances into such a plant for splitting the sulfuric acid (sulfuric acid splitting plant) ,

For example, SO3 obtained from the sulfuric acid splitting plant can be further processed into sulfuric acid, and the sulfuric acid thus obtained can be used in the production of acetone cyanohydrin. The present invention also relates to an apparatus for the production of alkyl methacrylates, comprising fluid-conducting interconnected

a plant element for producing acetone cyanohydrin, followed by;

- a plant element for the production of methacrylamide, followed by;

- An installation element for the preparation of methacrylic acid alkyl ester, optionally followed by; a plant element for cleaning the

Methacrylic acid alkyl ester, optionally followed by;

- An installation element for the polymerization, optionally followed by;

- a plant part for packaging,

wherein the apparatus comprises a rectification column for removing constituents having a boiling point of more than -5 ⁰ C and less than 100 ⁰ C from the produced acetone cyanohydrin and the rectification column is fluidly connected to the plant element for producing acetone cyanohydrin so that the removed components in the reaction for the production of acetone cyanohydrin are recycled.

Within the scope of a further embodiment of the invention, the plant element for producing alkyl methacrylate may be connected in a fluid-conducting manner to the plant element for producing methacrylamide in such a way that gaseous products obtained in the production of methacrylamide are introduced into the reaction mixture of the esterification.

The plant element for the production of methacrylic acid ester by esterification of methacrylamide with at least one alkyl alcohol may, for example, at least one scrubber for washing For example, the scrubber may be in fluid communication with the plant element for producing methacrylic acid ester in such a way that the scrubbing water obtained after the scrubbing is recycled to the esterification process.

It has proved in some cases to be useful when a device according to the invention comprises a plant element in which the mixture of water and sulfuric acid and optionally other substances from the esterification first by means of flotation of

Solids can be released and then cooled.

A device according to the invention may comprise heat exchangers in fluid communication with the plant element for producing methacrylic acid ester such that the mixture of water and sulfuric acid and optionally further substances from the esterification in the heat exchanger with the in the washing of the

Methacrylic acid alkyl ester is mixed with water obtained washing water.

For the entry of the wash water in the heat exchanger functional elements, such as nozzles, may be provided as a supply line, which allow entry of the wash water such that the inner surfaces of the heat exchanger are at least partially wetted with the wash water during operation. The entry of the wash water can for example be such that during operation are not permanently wetted with the mixture of water and sulfuric acid and optionally other substances from the esterification in contact inner surfaces of the heat exchanger with the wash water.

The plant element for purifying the methacrylic acid alkyl ester may further comprise at least one pre-cleaning element and a Main cleaning element, so that the methacrylic acid alkyl ester is subjected to a pre-cleaning and a main cleaning. In a further embodiment of the invention, the precleaning element can, for example, comprise at least one column for condensing methacrylic acid alkyl ester and a device for

Include postcondensation of gaseous condensable materials and are in fluid communication with the main cleaning element so that non-condensed gaseous residues can be fed from an optionally carried out main cleaning in the apparatus for condensing gaseous substances in the pre-cleaning element, so that a common post-condensation is possible.

The at least one apparatus for condensing gaseous substances as part of the pre-cleaning element may moreover be in fluid-conducting connection with a device for phase separation, so that a condensate obtained during the joint after-condensation is subjected to phase separation, whereby an aqueous phase and an organic phase can form.

The device for phase separation can furthermore be in fluid-conducting connection with the system element for preparing alkyl methacrylate, for example, such that an aqueous phase obtained in the device for phase separation can be at least partially supplied to the preparation of alkyl methacrylate. In addition, the device for phase separation may, for example, be in fluid-conducting connection with the prepurification element in such a way that the organic phase can be returned to the column of the prepurification element, in particular into the top of the column.

The present invention furthermore relates to the use of a methacrylic acid alkyl ester obtainable by a process according to any one of claims 1 to 16 for the production of fibers, films, paints, molding compositions, moldings, paper auxiliaries, leather auxiliaries, Flocculants and drilling additives; and fibers, films, lacquers, molding compounds, shaped articles, paper auxiliaries, leather auxiliaries, flocculants or drilling additives based on a methacrylic acid alkyl ester obtainable by a process according to the invention.

Detailed description of the invention

In the following, various method and device elements of the invention will be explained, which can be used individually or as an ensemble of two or more of said elements in the context of the present invention.

Preparation of acetone cyanhydrin

In this process element, acetone cyanohydrin is prepared by generally known methods (see, for example, Ullmanns Enzyklopadie der technischen Chemie, 4th Edition, Volume 7). Frequently acetone and hydrocyanic acid are used as reactants. The reaction is an exothermic reaction. In order to counteract a decomposition of the acetone cyanohydrin formed in the course of this reaction, the heat of reaction is usually removed by a suitable apparatus. The reaction can in principle be carried out as a batch process or as a continuous process, if a continuous procedure is preferred, the reaction is often carried out in a loop reactor, which is set up accordingly.

A key feature of a high yielding product to the desired product is often that the reaction product is cooled with sufficient reaction time and the reaction equilibrium is shifted in the direction of the reaction product. In addition, the reaction product for the benefit of overall yield often with a added stabilizer to prevent decomposition in the subsequent workup in the starting materials.

The mixing of the reactants acetone and hydrocyanic acid can basically be carried out in substantially any desired manner. The type of mixing depends in particular on whether a discrete mode of operation, for example in a batch reactor, or a continuous mode of operation, for example in the loop reactor, is selected.

In principle, it may be advantageous if the acetone is fed into the reaction via a feed tank which has a wash tower. Vent lines that carry acetone and hydrocyanic acid containing exhaust air, can be performed for example through this reservoir. In the scrubbing tower, which is connected to the storage tank, the exhaust air escaping from the storage tank can be washed with acetone, whereby hydrogen cyanide are removed from the exhaust air and recycled into the process. For this purpose, for example, a portion of the introduced from the reservoir into the reaction acetone in the partial flow through a cooler, preferably via a brine cooler, fed into the head of the scrubbing tower and thus achieved the desired result.

Depending on the extent of the amount of end products to be produced, it may be advantageous to supply the acetone from more than just one feed tank to the reaction. Each of the two or more storage containers can carry a corresponding wash tower. However, it is sufficient in many cases, if only one of the storage tanks is equipped with a corresponding wash tower. In this case, however, it is often useful if corresponding exhaust air lines that can transport acetone and hydrogen cyanide are passed through this container or via this wash tower.

The temperature of the acetone in the storage container can basically be within a substantially arbitrary range, insofar as the Acetone is in the liquid state at the corresponding temperature. Advantageously, however, the temperature in the storage tank is about 0 to about 20 ° C.

In the scrubbing tower, the acetone used for washing is cooled to a temperature of about 0 to about 10 ° C via a corresponding cooler, for example via a plate cooler with brine. The temperature of the acetone entering the scrubbing tower is therefore preferably, for example, about 2 to about 6 ^° C.

The hydrocyanic acid required in the reaction can be introduced into the reactor either in liquid or gaseous form. This may be, for example, raw gas from the BMA or from the Andrussow process.

The hydrogen cyanide, for example, be liquefied, for example by the use of a corresponding cooling brine. Instead of liquefied hydrocyanic acid coking gas can be used. Thus, for example, hydrogen cyanide-containing coke oven gas after washing with potash is continuously washed countercurrently with acetone containing 10% water, and the reaction to acetone cyanohydrin can be carried out in the presence of a basic catalyst in two series gas scrubbing columns.

Within the scope of a further embodiment, a gas mixture comprising hydrogen cyanide and inert gases, in particular a crude gas from the BMA process or from the Andrussow process, can be reacted with acetone in the presence of a basic catalyst and acetone cyanohydrin in a gas-liquid reactor.

In the context of the method described here, a raw BMA gas or an Andrussow raw gas is preferably used. That from the above-mentioned usual processes for the production of hydrogen cyanide resulting gas mixture can be used as such or after an acid wash. The raw gas from the BMA process, in which hydrogen cyanide and hydrogen are formed essentially from methane and ammonia, typically contains 22.9% by volume of HCN, 71.8% by volume of H ₂ , 2.5% by volume. NH3, 1, VoI .-% N ₂ , 1, 7 VoI .-% CH ₄ . In the well-known Andrussow process, hydrocyanic acid and water are formed from methane and ammonia and atmospheric oxygen. The raw gas of the Andrussow process typically contains about 8% by volume of HCN, 22% by volume of H ₂ , 46.5% by volume of N ₂ , 15% by volume of H ₂ O, 5 when oxygen is used as the source of oxygen Vol .-% CO, 2.5% by volume of NH3 and 0.5% by volume of CH4 and CO ₂ .

When using a non-acidic raw gas from the BMA or Andrussow process, the ammonia contained in the raw gas often acts as a catalyst for the reaction. Since the ammonia contained in the raw gas often exceeds the amount required as a catalyst and therefore can lead to high losses of sulfuric acid used for stabilization, such a raw gas is often subjected to an acid wash to eliminate ammonia therefrom. When using such an acid-washed crude gas, however, then a suitable basic catalyst must be added to the reactor in a catalytic amount. In principle, known inorganic or organic basic compounds can act as a catalyst.

Hydrogen cyanide in gaseous or in liquid form or a hydrogen cyanide-containing gas mixture and acetone are continuously fed to a loop reactor as part of the continuous procedure. The loop reactor thereby comprises at least one possibility for supplying acetone or two or more such possibilities, at least one possibility for supplying liquid or gaseous hydrocyanic acid, or two or more such possibilities as well as at least one possibility for supplying a catalyst. In principle, any alkaline compounds, such as ammonia, sodium hydroxide or potassium hydroxide, which can catalyze the conversion of acetone and hydrogen cyanide to acetone cyanohydrin, are suitable as catalyst. However, it has proved to be advantageous if as

Catalyst an organic catalyst, in particular an amine is used. Suitable examples are secondary or tertiary amines, such as diethylamine, dipropylamine, thethylamine, tri-n-propylamine and the like.

A loop reactor which can be used within the scope of the described process element furthermore has at least one pump, or two or more pumps, and at least one mixing device, or two or more such mixing devices.

Basically, all pumps which are suitable for ensuring the circulation of the reaction mixture in the loop reactor are suitable as pumps.

As mixing devices both mixing devices with movable elements and so-called static mixers are suitable in which immobile flow resistances are provided. In the case of the use of static mixers, for example, those are suitable which allow a Betriebsübertrug of at least about 10, for example at least about 15 or at least about 20 bar under operating conditions without significant restrictions on the functionality. Corresponding mixers may be made of plastic or metal. As plastic are, for example, PVC, PP; HDPE, PVDF, PFA or PTFE. Metal mixers may for example consist of nickel alloys, zirconium, titanium and the like. Also suitable, for example, rectangular mixer.

The addition of the catalyst is preferably carried out in the loop reactor downstream of the pump and upstream of a loop reactor Mixing element. Catalysts are used in the context of the reaction described, for example, in such an amount that the overall reaction at a pH of at most 8, in particular at most about 7.5 or about 7 is driven. It may be preferred if the pH in the reaction is within a range of about 6.5 to about 7.5, for example about 6.8 to about 7.2.

It is also possible in the context of the described method as an alternative to adding the catalyst in the loop reactor after the pump and before a mixing device, the catalyst together with the

Feed acetone into the loop reactor. In such a case, it may be advantageous to provide for appropriate mixing of acetone and catalyst prior to feeding into the loop reactor. A corresponding mixing can be done for example by using a mixer with moving parts or by using a static mixer.

If, in the context of the described method, a continuous procedure in a loop reactor is selected as the operating mode, it may be expedient to investigate the state of the reaction mixture by means of punctual or continuous analyzes. This offers the advantage that, if necessary, it is also possible to react quickly to changes in the state of the reaction mixture. In addition, for example, the reactants can be dosed as accurately as possible in order to minimize yield losses.

A corresponding analysis can be carried out for example by sampling in the reactor loop. Suitable analysis methods are, for example, pH measurement, measurement of the heat of reaction or measurement of the composition of the reaction mixture by suitable spectroscopic methods. In particular, in the context of turnover control, quality aspects and safety, it has often proven useful to determine the conversion in the reaction mixture on the heat dissipated from the reaction mixture and to compare with the theoretically released heat.

The actual reaction can, with a suitable choice of the loop reactor, basically take place in the pipe systems arranged inside the loop reactor. However, since the reaction is exothermic, care can be taken to avoid loss of yield, sufficient cooling or sufficient removal of the heat of reaction. It has often proved to be advantageous if the reaction takes place within a heat exchanger, preferably within a shell-and-tube heat exchanger. Depending on the amount of product to be produced, the capacity of a corresponding heat exchanger can be chosen differently. Heat exchangers with a volume of about 10 to about 40 m ^{3 have} proven particularly suitable for industrial processes. The tube bundle heat exchangers preferably used are heat exchangers which have a liquid-flowed tube bundle in a jacket through which liquid flows. Depending on the pipe diameter, packing density, etc., the heat transfer between the two liquids can be adjusted accordingly. It is fundamentally possible in the context of the method described to carry out the reaction to the effect that the reaction mixture is driven through the heat exchanger in the tube bundle itself and the reaction takes place within the tube bundle, wherein the heat is removed from the tube bundle into the sheath liquid.

However, it has also proven to be practical and in many cases useful to guide the reaction mixture through the jacket of the heat exchanger, while circulating the liquid used for cooling within the tube bundle. It has proven to be advantageous in many cases when the reaction mixture in Coat to achieve a longer residence time and better mixing through flow resistance, preferably baffles distributed.

Depending on the design of the reactor, the ratio of jacket volume to volume of the tube bundle may be about 10: 1 to about 1: 10, preferably the volume of the jacket is greater than the volume of the tube bundle (based on the contents of the tubes).

The heat removal from the reactor is adjusted with a suitable coolant, for example with water, such that the reaction temperature within a corridor is about 25 to about 45 ^° C., in particular about 30 to about 38, in particular about 33 to about 35 ^° C. ,

From the loop reactor, a product is continuously removed. The product has a temperature within the above reaction temperatures, for example, a temperature of about 35 ⁰ C. The product is cooled via one or more heat exchangers, in particular via one or more plate heat exchangers. For example, a brine cooling system is used. The temperature of the product after cooling should be about 0 to 10, in particular 1 to about 5 ⁰ C. The product is preferably transferred to a storage container having a buffer function. In addition, the product can be further cooled in the storage container, for example, by constantly discharging a partial flow from the storage container to a suitable heat exchanger, for example to a plate heat exchanger, or maintained at a suitable storage temperature. It is quite possible that a post-reaction can take place in the storage container.

The return of the product in the storage container, can basically be done in any way. It has, however, in some cases as advantageously found that the product is recycled through a system of one or more nozzles in the storage container so that takes place within the storage container, a corresponding mixing of the stored product.

From the storage container product is further continuously discharged into a stabilization tank. There, the product is treated with a suitable acid, for example with H ₂ SO ₄ . In this case, the catalyst is deactivated and the reaction mixture is adjusted to a pH of about 1 to about 3, in particular about 2. Sulfuric acid, for example sulfuric acid with a content of about 90 to about 105%, in particular from about 93 to about 98%, of H ₂ SO ₄ is particularly suitable as the acid.

The stabilized product is removed from the stabilization tank and transferred to the purification stage. In this case, a portion of the removed, stabilized product can be returned, for example, in such a way in the stabilization tank, that a sufficient mixing of the container is ensured by a system of one or more nozzles.

ACH workup

In the context of a further process element which can be used in connection with the present invention is

Acetone cyanohydrin, which were obtained in an upstream stage, for example, from the reaction of acetone with hydrogen cyanide, subjected to a distillative workup. In this case, the stabilized crude acetone cyanohydrin is freed via a corresponding column of low-boiling constituents. A suitable distillation process can be carried out, for example, via only one column. However, it is also possible, as part of a corresponding purification of crude acetone cyanohydrin, a combination of two or more Use distillation columns also combined with a falling film evaporator. Furthermore, two or more falling film evaporators or two or more distillation columns can be combined.

The crude acetone cyanohydrin is usually at a temperature of about 0 to about 15 ⁰ C, for example a temperature of about 5 to about 10 ⁰ C from the storage for distillation. In principle, the crude acetone cyanohydrin can be introduced directly into the column. However, it has proven useful in some cases when first the crude, cool acetone cyanohydrin takes over a heat exchanger part of the heat of the already purified by distillation product. Therefore, in the context of a further embodiment of the process described herein, the crude acetone cyanohydrin is heated via a heat exchanger to a temperature of about 60 to 80 ⁰ C.

The distillative purification of acetone cyanohydrin is carried out via a distillation column or a rectification column with more than 10 trays or via a cascade of two or more appropriately suitable distillation columns. The heating of the column bottom is preferably carried out with steam. It has been found to be advantageous if the bottom temperature does not exceed a temperature of 140 ⁰ C, good yields and a good cleaning can be achieved if the bottom temperature is not greater than about 130 ⁰ C or not higher than about 110 ⁰ C. The temperature data refer to the wall temperature of the column bottom.

The crude acetone cyanohydrin is fed to the column body in the upper third of the column. The distillation is preferably carried out at reduced pressure, for example at a pressure of about 50 to about 900 mbar, in particular about 50 to about 250 mbar and with good results between 50 to about 150 mbar. Gaseous impurities, in particular acetone and hydrocyanic acid, are taken off from the top of the column and the separated gaseous substances are cooled by means of a heat exchanger or a cascade of two or more heat exchangers. In this case, preferably a brine cooling with a temperature of about 0 to about 10 ⁰ C is used. The gaseous ingredients of the vapors are given the opportunity to condense. The first condensation stage can take place, for example, at normal pressure. However, it is also possible and has proved to be advantageous in some cases when this first condensation stage under reduced pressure, preferably in the

Pressure, which prevails in the context of the distillation takes place. The condensate is forwarded to a cooled collecting vessel and there collected at a temperature of about 0 to about 15 ⁰ C, in particular at about 5 to about 10 ⁰ C.

The non-condensing in the first condensation step gaseous compounds are removed via a vacuum pump from the vacuum chamber. In principle, any vacuum pump can be used. However, it has proved to be advantageous in many cases when a vacuum pump is used, which does not lead due to their design to the entry of liquid contaminants in the gas stream. Therefore, dry running vacuum pumps are preferably used here, for example.

The escaping on the pressure side of the pump gas stream is passed through a further heat exchanger, which is preferably cooled with brine at a temperature of about 0 to about 15 ⁰ C. This condensing ingredients are also collected in the sump, which already catches the condensates obtained under vacuum conditions. The condensation carried out on the pressure side of the vacuum pump can take place, for example, through a heat exchanger, but also with a cascade of two or more heat exchangers arranged in series in parallel. After this Condensation step remaining gaseous substances are removed and any other recycling, for example, a thermal utilization, fed.

The collected condensates can also be reused as desired. However, it has proved extremely advantageous from an economical point of view to recycle the condensates into the reaction to produce acetone cyanohydrin. This is preferably done at one or more locations allowing access to the loop reactor. The condensates may in principle have any composition, provided that they do not interfere with the production of the acetone cyanohydrin. In many cases, however, the majority of the condensate will consist of acetone and hydrocyanic acid, for example in a molar ratio of from about 2: 1 to about 1: 2, often in a ratio of about 1: 1.

The obtained from the bottom of the distillation column acetone cyanohydrin is first cooled by a first heat exchanger by the supplied, cold crude acetone cyanohydrin to a temperature of about 40 to about 80 ⁰ C. Subsequently, the

Acetone cooled via a least a further heat exchanger to a temperature of about 30 to about 35 ⁰ C and optionally stored.

Overall, it has been found to be advantageous in some cases when the acetone cyanohydrin in a rectification column at least from impurities having a boiling point of more than about -5 ⁰ C and less than about 100 ⁰ C, for example more than about 0 ⁰ C and less than about 90 ⁰ C, is freed, and these impurities are recycled into the reaction to produce acetone cyanohydrin. The corresponding process variant is advantageously carried out with the aid of a device comprising a rectification column for removing constituents having a boiling point of more than -5 ⁰ C and less as 100 ⁰ C from the prepared acetone cyanohydrin and the rectification column is fluidly connected in such a way with the plant element for the production of acetone cyanohydrin, that the removed components can be returned to the reaction for the preparation of acetone cyanohydrin.

amidation

In a further process step, the acetone cyanohydrin produced in the first step is subjected to hydrolysis. At various temperature stages, methacrylamide forms as product after a series of reactions.

The reaction is effected in a manner known to those skilled in the art by a reaction between concentrated sulfuric acid and acetone cyanohydrin. The reaction is exothermic, so that reaction heat can be removed from the system, for example, for the reaction control.

The reaction can also be carried out here again in a batch process or in continuous processes. The latter has proved advantageous in many cases. If the reaction is carried out as part of a continuous process, the use of loop reactors has proven itself. The reaction can be carried out, for example, in only one loop reactor. However, it may be advantageous if the reaction is carried out in a cascade of two or more loop reactors.

A suitable loop reactor in the described process comprises one or more feed sites for acetone cyanohydrin, one or more concentrated sulfuric acid feed stations, one or more gas separators, one or more heat exchangers, and one or more mixers. The hydrolysis of acetone cyanhydrin with sulfuric acid to methacrylamide is, as already described, exothermic. However, the heat of reaction arising in the context of the reaction can advantageously be at least substantially removed from the system such that a

Yield maximization can be achieved because with increasing temperature in the reaction, the yield decreases. It is basically possible to achieve a rapid and comprehensive removal of the heat of reaction with appropriate heat exchangers. However, it may be advantageous not to cool the mixture too much, since a sufficient heat transfer is required for a corresponding exchange at the heat exchangers. Since the viscosity of the mixture increases with decreasing temperature, circulation in the loop reactor can be made more difficult if the temperature is too high. In this case, if appropriate, a sufficient removal of the reaction energy from the system can no longer be guaranteed.

In addition, too low temperatures in the reaction mixture can lead to crystallization of ingredients of the reaction mixture at the heat exchangers. As a result, the heat transfer can be further deteriorated, which possibly leads to a decrease in yield. In addition, over-cooling may result in the loop reactor not being able to be charged with the optimal levels of reactants, so that the efficiency of the process may suffer as a result.

Within the scope of a further embodiment of the invention, a part, for example about two thirds to about three quarters, of the volume flow can be introduced from a stream of acetone cyanohydrin into a first loop reactor. In this case, such a first loop reactor may have one or more heat exchangers, one or more pumps, one or more mixing elements and one or more gas separators. The passing through the first loop reactor Circulating flows are for example in the range of about 100 to 450 m ³ / h, preferably in a range of 200 to 400 m ³ / h and moreover preferably in a range of about 250 to 350 m ³ / h. In an at least one further loop reactor following the first loop reactor, the recirculation streams are preferably in a range of about 40 to 450 m ³ / h, preferably in a range of 50 to 400 m ³ / h and moreover preferably in a range of about 60 up to 350 m ³ / h. Furthermore, about 1 to 10 ⁰ C are preferred as the temperature difference across the heat exchanger, with about 2 to 7 ⁰ C are particularly preferred.

The supply of acetone cyanohydrin can in principle be carried out at any point in the loop reactor. However, it has proven to be advantageous if the supply takes place in a mixing element, for example in a mixer with moving parts or a static mixer. The supply of sulfuric acid is advantageously carried out before

Acetone addition. Otherwise, however, it is also possible to introduce the sulfuric acid at any point in the loop reactor.

For example, the ratio of reactants in the loop reactor is controlled so that there is an excess of sulfuric acid. Of the

Excess sulfuric acid may be about 1, 8: 1 to about 3: 1 in the first loop reactor, and about 1.3: 1 to about 2: 1 in the last loop reactor, in terms of the molar ratio of the ingredients.

In some cases, it has proven advantageous to operate the reaction in the loop reactor with such an excess of sulfuric acid. The sulfuric acid can be used here as a solvent and keep the viscosity of the reaction mixture low, whereby a higher removal of heat of reaction and a lower temperature of the reaction mixture can be ensured. This can bring significant yield advantages. The temperature in the reaction mixture is about 90 to about 120 ⁰ C, for example about 95 to about 115 ⁰ C. The heat removal can be ensured by one or more heat exchangers in the loop reactor. It has often proven to be advantageous if the heat exchangers have a suitable sensor for adjusting the cooling capacity in order to prevent excessive cooling of the reaction mixture for the reasons mentioned above. Thus, it may be advantageous, for example, to measure the heat transfer in the heat exchanger or in the heat exchangers punctiform or continuously and to adjust the cooling capacity of the heat exchangers. This can be done for example via the coolant itself. It is also equally possible to achieve a corresponding heating of the reaction mixture by appropriate variation of the addition of the reactants and by the generation of more heat of reaction. A combination of both possibilities is conceivable. The loop reactor should also have at least one gas separator. On the one hand the loop reactor continuously formed product is removed via the gas separator. On the other hand, gases formed during the reaction can thus be withdrawn from the reaction space. The gas is mainly carbon monoxide. The product taken from the loop reactor is preferably transferred to a second loop reactor. In this second loop reactor, the reaction mixture containing sulfuric acid and methacrylic acid amide, as obtained by the reaction in the first loop reactor, is reacted with the remaining partial stream of acetone cyanohydrin. In this case, the excess of sulfuric acid from the first loop reactor, or at least part of the excess sulfuric acid, reacts with the acetone cyanohydrin with further formation of methacrylamide. The implementation of the reaction in two or more loop reactors has the advantage that due to the sulfuric acid excess in the first loop reactor, the pumpability of the reaction mixture and thus the heat transfer and ultimately the yield can be improved. In the second loop reactor, in turn, at least one mixing element, at least one heat exchanger and at least one gas separator arranged. The reaction temperature in the second loop reactor is also about 90 to about 120 ^° C.

The problem of the pumpability of the reaction mixture, the heat transfer and the lowest possible reaction temperature is the same in every other loop reactor as in the first. Therefore, advantageously, the second loop reactor has a heat exchanger whose cooling capacity can be controlled by appropriate sensors.

The supply of acetone cyanohydrin is again carried out in a suitable mixing element, preferably in a static mixer.

From the gas separator of the second loop reactor, the product is removed and heated to a temperature of about 140 to about 180 ⁰ C to complete the reaction and to form the methacrylamide.

The heating is preferably carried out such that the maximum temperature is achieved only for the shortest possible time period, for example for a time of about one minute to about 30 minutes, in particular for a time of about two to about eight or about three to about five minutes. This can basically be done in any apparatus to achieve such a temperature for such a short period of time. For example, the power can be supplied conventionally by electrical energy or by steam. However, it is also possible to supply the energy by electromagnetic radiation, for example by microwaves.

It has proven to be advantageous in various cases when the heating step in a heat exchanger with two or more stages arrangement of coiled tubing, preferably in an at least double, opposing arrangement can be done. The reaction mixture is heated rapidly to a temperature of about 140 to 180 ⁰ C.

The heat exchanger may, for example, with one or more

Combined gas separators. Thus, it is possible, for example, to lead the reaction mixture after leaving the first coiled tubing in the heat exchanger through a gas separator. In this case, for example, formed during the reaction, gaseous components are separated from the reaction mixture. It is also possible to treat the reaction mixture after leaving the second coil with a gas separator. It may also be advantageous to treat the reaction mixture with a gas separator at both points, both after leaving the first and after leaving the second coiled tubing.

The amide solution thus obtainable generally has a temperature of more than 100 ⁰ C, usually a temperature of about 140 to 180 ⁰ C.

The resulting gaseous compounds in the amidation can basically be disposed of in any way or fed to a further processing. In some cases, however, it may be advantageous if the corresponding gases are combined in a transport line in such a way that they can be subjected either continuously or if necessary, if necessary, to pressure, for example with steam pressure, and thus transported onward.

In a further embodiment of the invention, it has been found in some cases to be advantageous if, in the context of

Production of methacrylamide amide resulting gaseous products are introduced in the context of further transport into the reaction mixture of the below-described esterification. It can be one Initially done at any point in the esterification. Often, however, it is advantageous, especially when an esterification takes place in several Keseln to initiate the resulting gaseous products in the reaction mixture of the esterification, which is a first boiler. The introduction of the resulting gaseous products, for example, be designed so that the steamed gases are introduced into a boiler so that they provide for at least local mixing of the boiler contents or for heating the boiler contents or for a substantially constant temperature of the boiler contents or provide for a combination of two of said elements.

esterification

Another step of the invention is the hydrolysis of methacrylamide to methacrylic acid and their simultaneous esterification to methacrylic acid ester. This reaction can be carried out in one or more heated, for example steam-heated boilers. It has proved advantageous in many cases if the esterification is carried out in at least two successive boilers, but for example also in three or four or more successive boilers. In this case, a solution of methacrylamide is introduced into the boiler or in the first boiler of a two or more boiler cascade of boilers.

It is often preferred to carry out a corresponding esterification reaction with a cascade of two or more vessels. In the following, therefore, reference will be made exclusively to this variant.

In the context of the invention described here, for example, an amide solution, as obtainable from the amidation reaction described here, can be fed into a first vessel. The boiler is heated with steam, for example. The supplied amide solution points in the Typically, an elevated temperature, for example, a temperature of about 100 to about 180 ⁰ C, substantially corresponding to the discharge temperature of the amide solution from the amidation reaction presented above. The boilers continue to be supplied with an alkanol, which can be used for esterification.

In principle, any alkanols having 1 to about 4 carbon atoms, which may be linear or branched, saturated or unsaturated, are suitable here, with methanol being particularly preferred. Likewise, these alkanols can be used together with methacrylic acid esters, which is the case in particular in transesterifications.

The boiler is further charged with water, so that a total water concentration in the boiler of about 13 to about 26 wt .-%, in particular about 18 to about 20 wt .-% prevails.

The amount of amide solution and alkanol is controlled such that a total molar ratio of amide to alkanol of about 1: 1, 4 to about 1: 1, 6 prevails. The alkanol can be distributed to the kettle cascade such that in the first reactor the molar ratio is about 1: 1, 1 to about 1: 1, 4 and in the following reaction stages based on the Gesamtamidstrom molar ratios of about 1: 0.05 to about 1 : 0.3 can be adjusted. The alkanol fed into the esterification can be composed of "fresh alkanol" and alkanol from recycling streams of the work-up stages and, if required, also from recycling streams of the downstream processes of the production network.

The feeding of the first kettle with water can basically be carried out by supplying water from any source to the kettle, provided that this water has no ingredients which could adversely affect the esterification reaction or the subsequent process stages. For example, the boiler VE-water or well water can be supplied. It is, however, too possible to supply the boiler with a mixture of water and organic compounds, as obtained for example in the purification of methacrylic acid or methacrylic acid esters. In a preferred embodiment of the method presented here, the boilers are at least partially charged with a mixture of water and such organic compounds.

If a cascade of two or more boilers is used in the course of the esterification reaction, the resulting gaseous substances, in particular the methacrylic acid esters, can in principle be withdrawn from each vessel individually and fed to a purification. However, it has proven to be advantageous in some cases, when in a cascade of two or more boilers, the gaseous products from the first boiler are first fed into the second reaction vessel, without the gaseous compounds from the first boiler are fed directly to a cleaning. This approach has the advantage that the often strong foaming in the first boiler does not have to be counteracted by expensive, defoaming apparatus. In the case of a cascading of the gaseous substances from the first boiler into the second boiler, the foam formed in the first tank and possibly entrained simply enters the reaction space of the second boiler. Since foaming is generally much lower there, it is not necessary to defoam the equipment.

The arranged after a first boiler second boiler now takes on the one hand the overflow of the first boiler, on the other hand it is fed with the gaseous substances formed in the first boiler or existing in the first boiler. The second boiler and the possibly following are also charged with methanol. It is preferred that the amount of methanol from boiler to boiler by at least 10%, based on the previous boiler, decreases. The water concentration in the second boiler and in the other boilers may differ from that of the first boiler, but often the concentration difference is small.

The vapors produced in the second boiler are removed from the boiler and introduced into the bottom of a distillation column.

If the esterification is carried out with a cascade of three or more boilers, the overflow of the second boiler is transferred to a third boiler and the overflow of the third boiler is transferred to a fourth boiler if necessary. The other boilers are also steam-heated. Preferably, the temperature in the boilers 3 and optionally 4 is set to about 120 ⁰ C to about 140 ⁰ C.

The vapors escaping from the boilers are introduced into a distillation column, these preferably in the

Subregion of the distillation column takes place. The vapors comprise an azeotropic mixture of carrier vapor, methacrylic acid ester and alkanol and depending on the alkanol used have a temperature of about 60 to about 120 ⁰ C, for example about 70 to about 90 ⁰ C when using methanol. In the distillation column, the methacrylic acid ester is separated in gaseous form from the vapor components boiling at higher temperatures. The high-boiling components (mainly methacrylamide, hydroxyisobutyric acid ester and water) are recycled to the first reaction vessel. The methacrylic acid ester formed is withdrawn from the top of the column and cooled by a heat exchanger or a cascade of two or more heat exchangers. It has proven in some cases when the cooling of the methacrylic acid ester takes place via at least two heat exchangers, wherein a first heat exchanger with water performs the condensation and cooling to a temperature of about 60 to about 30 ⁰ C, while a second, brine-cooled heat exchanger Cooling to about 5 to about 15 ⁰ C makes. From the water-cooled condensate can be a partial flow as reflux to the Columns for concentration control of the column given. However, it is also possible to cool the formed methacrylic ester via a cascade of more than two heat exchangers. In this case, it is possible, for example, first to carry out cooling by means of two water-cooled heat exchangers connected in series, and then to achieve further cooling by means of a corresponding brine-cooled heat exchanger.

Thus, for example, in the context of the process presented here, the methacrylic acid ester formed can be cooled in the gaseous state via a first heat exchanger with water cooling. Both condensed and non-condensed materials are then transferred to a second heat exchanger, where further condensation via water cooling takes place. At this point, for example, gaseous substances can now be transferred into a separate, cooled with brine heat exchanger. The condensate in this brine-cooled heat exchanger is then added to the distillate stream, while the remaining gaseous substances can be recycled or sent for disposal. The methacrylate ester condensate from the second water-cooled

Heat exchanger is then cooled in a cooled with water or with sole heat exchanger to a temperature of less than 15 ⁰ C, preferably about 8 to about 12 ⁰ C. This cooling step can lead to the methacrylic acid ester formed having a significantly lower formic acid content than would be the case without the corresponding cooling step. The cooled condensate is then transferred to a phase separator. Here, the organic phase (methacrylic acid ester) is separated from the aqueous phase. The aqueous phase, which in addition to water may still have a content of organic compounds, in particular alkanol, from the distillation step, can in principle be used as desired. However, as already described above, it may be preferable that this mixture of water and organic compounds again in the Esterification process by feeding into the first reaction vessel takes place.

The separated organic phase is fed to a scrubber. There, the methacrylic acid ester is washed with demineralized water. The separated aqueous phase, which contains a mixture of water and organic compounds, in particular alkanol, can in principle be used in any other way. However, it is advantageous from an economic point of view to recycle this aqueous phase back into the esterification step, for example, by feeding it into the first kettle.

Since methacrylic acid esters have a strong tendency to undergo polymerization, it is advantageous in many cases when, in the course of the esterification of methacrylic acid, care is taken to prevent such polymerization.

In plants for the production of methacrylic acid or methacrylic acid esters, polymerization often takes place when methacrylic acid or methacrylic ester on the one hand have a low flow velocity, so that locally quiet zones can form in which a prolonged contact between methacrylic acid or methacrylic acid ester and a polymerization initiator can be established, which can then result in polymerization.

In order to avoid a corresponding polymerization behavior, it may be advantageous to carry out an optimization of the material flow to the effect that, on the one hand, the flow rate of the methacrylic acid ester or of the methacrylic acid at all points in the system is so high that the number of quiet zones is minimized. In addition, it may be advantageous to add the stream of methacrylic acid or methacrylic acid ester with suitable stabilizers such that polymerization is largely suppressed. For this purpose, in the context of the process shown here, in principle, the material streams can be mixed with stabilizers in such a way that the least possible polymerization takes place in the system itself. For this purpose, in particular the part of the plant is supplied with appropriate stabilizers in which the methacrylic acid or the methacrylic acid ester is present during or after the distillation in high concentration.

Thus, for example, it has proven to be useful to the top of the distillation column to the current withdrawn there

Methacrylic acid ester to supply a stabilizer. Furthermore, it has proved to be advantageous to rinse those parts of the plant with a solution of stabilizer in methacrylic acid esters in which methacrylic acid or methacrylic acid ester with a temperature of more than about 20 ⁰ C, preferably at a temperature in the range of about 20 to about 120 ⁰ C. circulated. Thus, for example, part of the condensate accumulating in the heat exchangers, together with a suitable stabilizer, is returned to the top of the distillation column in such a way that the column head is continuously sprayed on its inside with stabilized methacrylic acid ester or stabilized methacrylic acid. This is preferably done in such a way that no rest zones can form in the top of the column, at which a polymerization of methacrylic acid or methacrylic acid ester is to be feared. The heat exchangers themselves can accordingly also with a stabilized solution of methacrylic acid or

Methacrylic acid esters are acted upon in such a way that here no quiet zones can be trained.

It has also proved to be an advantage in the context of the process presented here, for example, if the exhaust gases containing carbon monoxide from preceding processes, in particular from the amidation step, are passed through the esterification plant together with steam. In this way, a reunification of the Gas mixture of compounds which can be separated as a solid or as a liquid. On the other hand, these are collected at a central location and can be sent for further recovery or disposal.

The MMA obtained in the course of the esterification and the subsequent pre-cleaning or the methacrylic acid ester obtained or the resulting methacrylic acid are then fed to a further treatment. From the esterification results as remaining residue dilute sulfuric acid, which can also be fed to a further recovery.

Pre-cleaning of the ester or the acid

In the context of the process presented here, the subject matter of the present invention can also be used in connection with a process for the prepurification of methacrylic acid or methacrylic acid ester, as described in the following process element. Thus, in principle, crude methacrylic acid or a crude methacrylic acid ester is subjected to further purification in order to arrive at a product which is as pure as possible. Such a further process element representing cleaning, for example, be single-stage. However, it has proven to be advantageous in many cases if such a purification comprises at least two stages, wherein in a first pre-cleaning, as described herein, the low-boiling constituents of the product are removed. For this purpose, crude methacrylic acid ester or crude methacrylic acid is first transferred to a distillation column in which the low-boiling constituents and water can be separated off. For this purpose, the crude methacrylic acid ester is fed to a distillation column, the addition being carried out approximately in the upper half of the column. The column bottom is heated with steam, for example, such that a wall temperature of about 50 to about 120 ⁰ C is reached. The cleaning is carried out under vacuum. The pressure within the column is preferably about 100 to about 600 mbar in the case of the ester. The pressure within the column is preferably about 40 to about 300 mbar in the case of the acid.

At the top of the column, the low-boiling components are removed. In particular, these may be, for example, ether, acetone and methyl formate. The vapors are then condensed via one or more heat exchangers. In some cases, it has proven useful, for example, first to carry out a condensation via two series-connected, water-cooled heat exchangers. However, it is also possible to use only one heat exchanger at this point. The heat exchangers are preferably operated in a vertical state to increase the flow rate and to prevent the formation of stationary phases. Downstream of the water-cooled heat exchanger or water-cooled heat exchangers may be a brine-cooled heat exchanger, but it is also possible to connect a cascade of two or more brine-cooled heat exchangers. In the cascade of heat exchangers, the vapors are condensed, provided with stabilizer and fed, for example, a phase separator. Since the vapors can also contain water, any accumulating aqueous phase is disposed of or sent for further use. As further utilization, for example, the return in an esterification reaction, for example, in an esterification reaction as described above, offers. In this case, the aqueous phase is preferably recycled to the first esterification vessel.

The separated organic phase is fed as reflux into the top of the column. Part of the organic phase can in turn be used to spray the heat exchanger heads and the column head. Since the separated organic phase is a phase which is mixed with stabilizer, it is possible to do so effectively prevent the formation of quiet zones on the one hand. On the other hand, the presence of the stabilizer causes a further suppression of the polymerization tendency of the separated vapors.

In addition, the condensate stream obtained from the heat exchangers is preferably mixed with demineralized water in such a way that a sufficient separation effect can be achieved in the phase separator.

The gaseous compounds remaining after the condensation in the heat exchanger cascade can, preferably by means of vapor ejectors as negative pressure generators, again be subjected to condensation via one or more further heat exchangers. It has been found to be advantageous from an economic point of view, if not only the gaseous substances from the pre-cleaning are condensed in the context of such a post-condensation. Thus, it is possible, for example, to supply further gaseous substances to such after-condensation, as they result from the main purification of methacrylic acid esters. The advantage of such a procedure is, for example, that a proportion of methacrylic acid ester, which was not condensed in the context of the main purification stage, can be transferred again via the phase separator into the purification column during the pre-purification. Thus, for example, it is ensured that a maximization of yield can take place, and the lowest possible losses of methacrylic ester occur. In addition, the composition of the exhaust gas leaving this heat exchanger, in particular the content of low boilers, can be adjusted by suitably selecting the design and operation of this further heat exchanger.

Due to the supply of water as part of the pre-purification of the methacrylic acid ester, the water content in the esterification and the concentration of low-boiling constituents in the crude Methyl methacrylate increase continuously. To avoid this, it may be advantageous to discharge a portion of the water supplied to the system, preferably continuously, from the system. In principle, this discharging can take place, for example, in an order of magnitude in which water is supplied to the system in the pre-cleaning. The deposited in the phase separator aqueous phase usually has a content of organic ingredients. It may therefore be advantageous to supply this water to a form of disposal which exploits this content of organic matter.

Thus, it may be advantageous, for example, if such a water contaminated with organic substances in the context of a sulfuric acid slit process is added to the combustion chamber. Due to the oxidizable ingredients so their calorific value, at least partially, can still be used. In addition, a potentially costly disposal of contaminated with organic substances water is often avoided.

Main purification of the methacrylic ester

For the main purification of the methacrylic acid ester, the crude, prepurified methacrylic acid ester is subjected to a redistillation. The crude methacrylic acid ester is freed from its high-boiling constituents with the aid of a distillation column to obtain a pure methacrylic acid ester. This is the raw

Methacrylic acid ester introduced in a manner known to those skilled in the lower half of a distillation column.

In principle, the distillation column can correspond to any embodiment which appears suitable to a person skilled in the art. However, it has proven to be advantageous for the purity of the product obtained in many cases, if the distillation column with one or several packs, which corresponds approximately to the following specifications:

On the one hand, as few "dead spaces" as possible should form in the columns as well as in the other lines through which methacrylates flow, resulting in a comparatively long residence time of the methacrylic acid esters, which in turn promotes their polymerization, which in turn leads to costly production interruptions and purifications of the methacrylic acid The formation of dead spaces can be countered, inter alia, by the fact that both by design and by a suitable operation of the columns, they are always loaded with a sufficient amount of liquid, so that a constant flushing of the columns and in particular Thus, the columns can be spray units designed for spraying the column internals Furthermore, the column internals can interconnect with one another or with the column via interrupted adhesive seams Such adhesive seams have at least about 2, preferably at least about 5 and most preferably at least about 10 interruptions to 1 m adhesive seam length. The length of these breaks may be selected to be at least about 10, preferably at least about 20, and most preferably at least about 50%, but generally not more than 95% of the length of the adhesive seam.

Another constructional measure may be that less than about 50%, preferably less than about 25% and particularly preferably less than about 10% of all surfaces, in particular of column internals, are horizontal in the inner column regions, in particular those which come into contact with the methacrylic acid ester run. Thus, for example, the opening into the interior of the column neck can be configured conically or with inclined surfaces. Furthermore, a Measure consist in keeping the amount of liquid of methacrylic acid ester during operation of the column in the column bottom as low as possible and on the other hand to avoid overheating of this amount despite moderate temperatures and large evaporation surfaces during evaporation. In this case, it may be advantageous for the amount of liquid in the column bottom to be in the range from about 0.1 to 15% and preferably about 1 to 10% of the total amount of methacrylic acid ester in the column. The measures proposed in this section can also be used in the distillation of methacrylic acid.

In the course of the purification of the methacrylic acid ester, its high-boiling components are separated from the product by distillation. For this purpose, the column bottom is heated with steam. The bottom temperature is preferably about 50 to about 80 ⁰ C, in particular about 60 to about 75 ⁰ C at a wall temperature of less than about 120 ⁰ C.

The material obtained in the bottom of the column is preferably removed continuously and via a heat exchanger or a cascade of several heat exchangers to a temperature in a range from about 40 to about 80 ⁰ C, preferably about 40 to about 60 ⁰ C and more preferably in a range of about 50 to 60 ⁰ C cooled.

This material, predominantly methacrylic acid ester,

Contains hydroxyisobutyric acid ester, methacrylic acid and stabilizer components is then placed on a storage container, for example, disposed of or otherwise used. It has proven advantageous in many cases if the material obtained in the column bottom is returned to the esterification reaction. For example, the material is recycled from the bottom of the column in the first esterification boiler. This has the advantage that in terms of the most economical driving and a As high yield contained in the bottom of the column, higher-boiling compounds are attributed to the esterification reaction.

At the top of the column, the purified by distillation methacrylic acid ester is removed and cooled by a heat exchanger or a cascade of two or more heat exchangers. The heat of the vapors can be dissipated by water-cooled heat exchangers or by brine-cooled heat exchangers or by a combination of both. It has proven useful in some cases if the vapors from the distillation column in two or more parallel

Heat exchangers are transferred, which are operated by means of water cooling. The non-condensed fractions from the water-cooled heat exchangers can be introduced, for example, into a brine-cooled heat exchanger or a cascade of two or more brine-cooled heat exchangers, which can be arranged in series or in parallel. The condensates obtainable from the heat exchangers are introduced into a collecting tank and fed by means of a pump via a further heat exchanger or a cascade of two or more further heat exchangers to a buffer tank. The condensate stream is, for example, via a cascade of one or two water-cooled heat exchangers and one or two brine-cooled heat exchangers to a temperature in a range of about 0 to about 20 ⁰ C, preferably about 0 to about 15 ⁰ C and more preferably in a range of cooled down about 2 to 10 ⁰ C.

The condensate stream is taken from a partial stream, which is returned via the top of the column in the distillation column. In principle, the feeding of the condensate stream into the column head can take place in any desired manner, for example via distributors. However, it may be advantageous if a portion of the condensate stream is fed into the vapor line above the top of the column, for example sprayed, will. Furthermore, it is preferred that stabilizer is introduced into the top of the column with this feed.

A further partial stream of the condensate provided for recycling into the column can be branched off, for example, before introduction into the vapor line and introduced directly into the top of the column. Again, it is preferred that is introduced with this feed stabilizer in the top of the column. The introduction into the column head can take place, for example, in such a way that the interior of the column head is sprayed with the condensate in such a way that no quiet zones can form in the column head at which polymerization of the methacrylic acid ester can take place. It may also be advantageous if a stabilizer to prevent polymerization is added to a partial flow of condensate returned to the column. This can be done, for example, by adding a corresponding amount of polymerization inhibitor as a stabilizer to the condensate partial stream intended for spraying the column head. It has proven to be advantageous in some cases when the condensate partial stream after the addition of the stabilizer, but before entering the column head passes through a suitable mixing device, preferably a static mixer to achieve a uniform distribution of the stabilizer in the condensate partial stream.

The resulting in the purification process, non-condensable gaseous substances are supplied for disposal, for example.

The crude product contained in the buffer tank is maintained at a temperature of about 0 to about 20 ⁰ C, preferably about 0 to about 15 ⁰ C and more preferably in a range of about 2 to 10 ⁰ C with the aid of a brine cooler. In order to remove any further impurities from the product and to reach the pure methacrylic acid esters, the product may be subjected to an adsorptive purification step. It has proven, for example, when the pure product is completely purified or at least a portion of the pure product using a molecular sieve on. Particularly acidic impurities, in particular formic acid formed during the production process, can thus be removed from the product stream in a simple manner. Moreover, in some cases, it has proven useful in some cases when the product stream, after passing through the adsorptive purification stage, passes through one or more filters in order to remove any solids present in the product.

The material streams occurring in the course of workup predominantly comprise polymerizable compounds. In order, as already described several times in this text, to prevent the formation of quiet zones, it has been found in the case of the method described herein to be advantageous when the parts of the plant, which come into contact with methacrylic ester, are constantly overflowed with methacrylic acid ester , In the context of a further embodiment of the method presented here is therefore a

Partial stream of methacrylic acid ester after the buffer tank, but taken before the adsorptive purification step to overflow the head areas of those heat exchangers that absorb the originating from the distillation column vapors.

Overall, it has proved to be advantageous in the context of the present invention if the composite of pre-cleaning and main cleaning is designed such that

- In the pre-cleaning substances are separated, which have a lower boiling point than that

Alkyl methacrylates and these substances are then condensed by cooling, leaving non-condensed residues in the gas phase, - In the main cleaning substances are separated, which have a higher boiling point than the alkyl methacrylate and this is condensed by cooling, with non-condensed residues remain in the gas phase and

- Not condensed gaseous residues from the pre-cleaning and uncondensed gaseous residues from the main cleaning of a common post-condensation are subjected.

A condensate obtained in such a joint after-condensation can advantageously be subjected to a phase separation, wherein an aqueous and an organic phase can form. In this case, for example, the aqueous phase can be wholly or partially recycled to the esterification or the organic phase can be wholly or partially recycled to the pre-cleaning or both.

The total product obtained in the purification stage is then removed at a temperature in the range of about -5 to about 20 ⁰ C, preferably about 0 to about 15 ⁰ C and more preferably in a range of about 2 to 10 ⁰ C of the purification stage ,

Stripping the spent acid

In the context of the method presented here, it may be useful, for example in a further process element, to subject the consumed sulfuric acid obtained in the process to purification, in order subsequently to return it to the process. In this case, for example, a stream of spent sulfuric acid, as can be obtained from the esterification, be subjected to steam in a flotation tank. In this case, at least part of the solids contained can deposit on the surface of the liquid, wherein these separated solids can be removed. The vapors are then condensed in a heat exchanger, preferably with water cooling, cooled and returned to the esterification reaction.

It has proved to be advantageous in some cases if, to reduce corrosion in the heat exchangers and to further improve the cooling effect, a mixture of water and organic compounds, as obtained in the esterification in the purification of the produced methacrylic acid ester by washing in which heat exchangers are introduced in such a way that the heads of the heat exchangers are sprayed with this mixture. In addition to the corrosion-reducing effect and the cooling of the acid in the heat exchanger, this approach has a further advantage. Material derived from esterification (a mixture of water and predominantly methanol) is recycled to the esterification process along with the methacrylic acid and methacrylic acid ester derived from that process. In the stripper, mixtures of acid and solids are obtained by the flotation described above. These are after their separation of any other

Use or disposal supplied. It is possible, for example, to burn the mixture obtained in a splitting plant and thus to produce sulfuric acid again to recover some of the energy used in the process.

The stripping occurring, non-condensable gaseous compounds are fed to any further use or disposed of.

The plant described here for the removal of solids from the spent acid and for the return of material from the esterification process in just this process, for reasons of reliability, for example, be carried out twice. So For example, the two or more flotation tanks can be used at different times. Since solids can settle in these containers, it is advantageous to remove them if the respective flotation container is not in use.

The present invention furthermore relates to the use of the methacrylic acid obtainable by the process according to the invention or the methacrylic acid ester obtainable by the process according to the invention in fibers, films, paints, molding compositions,

Moldings, paper auxiliaries, leather auxiliaries, flocculants and drilling additives. In addition, the present invention relates to fibers, films, coatings, molding compositions, moldings, paper auxiliaries, leather auxiliaries, flocculants and drilling additives which are based on a methacrylic acid obtainable by the process according to the invention or a methacrylic acid ester obtainable by the process according to the invention.

The foregoing will now be exemplified by way of non-limiting drawings. Show it:

Fig. 1: an apparatus for manufacturing and processing of

Methacrylic acid or methyl methacrylate,

2 shows schematically a plant for the production of acetone cyanohydrin,

3 shows schematically a reprocessing plant of acetone cyanohydrin,

4: schematically amidation plant,

5 shows schematically an esterification plant,

6 shows schematically a plant for pre-purification of the ester, Fig. 7: The fine cleaning system of the ester.

In Fig. 1, the preferred elements are shown a plant composite 1 for the production of methacrylic acid or methacrylic acid esters and their processing products. The system composite 1 has various interconnected mostly fluid-conducting systems as elements of this composite. This composite includes acetone cyanohydrin production 20, followed by acetone cyanohydrin work-up 30, followed by amidation 40, followed by esterification / hydrolysis 50 / 50a), followed by work-up for ester or methacrylic acid 60, again followed by a finely-cleaned 70, after which Ester, usually methyl methacrylate, or methacrylic acid is present. The pure ester / pure acid thus obtained can be fed to a further processing plant 80. Suitable further processing plants 80 are, in particular, polymerization apparatuses and reactors for further organic reactions. Polymethacrylates can be prepared in the polymerization reactors, and in the reactors for organic reactions, the pure monomers obtained here can be converted into further organic compounds. If the further processing products are polymers of methacrylic acid or methacrylic acid esters, in particular methyl methacrylate, these are transformed into fibers, molding compositions, in particular granules, films, plates, automobile parts and other shaped articles by suitable processes Equipment such as extruders, blow extruders, injection molding equipment, spinnerets and the like, further processed. Furthermore, the system composite 1 in many cases includes a sulfuric acid plant 100. In principle, all sulfuric acid plants suitable for this purpose which are suitable for this purpose are considered. For example, see Chapter 4, page 89 et seq. In "Integrated Pollution Prevention and Control -Draft Reference Document on Best Avalible Techniques for the Manufacture of Large Volume Inorganic Chemicals - Amonia Acids and Fertelizers ", available from the European Commission, in this connection The Sulfuric Acid Plant 100 is connected to a number of other plants, such as the production of acetone cyanohydrin 20 via a

Sulfuric acid 2 supplied with concentrated sulfuric acid. In addition, there is another sulfuric acid line 3 between the sulfuric acid plant 100 and the amidation 40. The dilute sulfuric acid also referred to as "spent acid" from the esterification 50 (hydrolysis 50a) is transferred to the sulfuric acid plant 100 through the spent sulfuric acid lines 4 and 5, respectively. The dilute sulfuric acid can be worked up in the sulfuric acid plant 100. The dilute sulfuric acid can be worked up, for example, as described in WO 02/23088 A1 or WO 02/23089 A1

Expert performed common and suitable for the respective stresses appear materials. Mostly this is stainless steel, which in particular must have a special acid resistance. The areas of the plants, which are operated with sulfuric acid and in particular with concentrated sulfuric acid, are also lined with ceramic materials or plastics and protected. In addition, the methacrylic acid obtained in the methacrylic acid plant 50a can be supplied to the pre-cleaning 60 via a methacrylic acid line 6. Furthermore, it has been proven that in the acetone cyanohydrin production 20, the amidation 40, the esterification 50, the hydrolysis 50a, the pre-cleaning 60 and also the final cleaning 70 add a marked "S" stabilizer.

In the acetone cyanohydrin production 20 shown in Figure 2, the acetone in an acetone container 21 and the hydrogen cyanide in a

Hydrocyanic acid tank 22 is provided. The acetone container 21 has a washing tower 23, which has one or more cooling elements 24 in its upper region. In the wash tower 23 opens a series of Exhaust pipes 25, which come from different systems of the system composite 1. In a loop reactor 26, the acetone is fed via the acetone feed line 27 and the hydrocyanic acid via the hydrocyanic acid feed line 28 downstream of the hydrocyanic acid feed line 28 there is a pump 29, again followed by a catalyst feed 210, followed by a static mixer 211. This is followed by a heat exchanger 212, which has a number of flow resistances 213 and at least one cooling line 214. In the loop reactor 26, the reaction mixture consisting of acetone, hydrocyanic acid and catalyst is driven to a considerable extent in a cycle which is characterized by bold lines. From the heat exchanger 212, the reaction mixture is passed over the flow resistance along the cooling lines 214 and a part of the circulating stream passed into another heat exchanger 215, followed by a collecting tank 216, in which a nozzle 217 as part of a cooling circuit 218 with a heat exchanger 219th is located, whereby the reaction product is held on the one hand in motion and the other cool. A stabilizer tank 221 is connected via a discharge line 220 adjoining the collecting tank 216, to which a sulfuric acid feed line 222 opens and from which the crude acetone cyanohydrin is passed through the discharge line 223 into the acetone cyanohydrin work-up 30.

In FIG. 3, the derivative 223 discharges from cyanohydrin production 20 into a heat exchanger 31, in which the stream coming from cyanogen 20 is heated. The heat exchanger 31 is followed by a vapor feed line 32, which opens into the upper, preferably the top region of a column 33. The column 33 has a plurality of packages 34, which are usually designed as trays. In the lower region of the column 33, there is the column sump 35, from which a sump discharge 36 leads into the heat exchanger 31 and heats the streams conducted via the discharge line 233 into the heat exchange 31. To the heat exchanger 31 is followed by a pure product guide 37, followed by the amidation 40 downstream. In the top region of the column 33 is a head discharge 38, which opens into a heat exchanger 39, which is followed by a vacuum pump 310, which in turn opens into a heat exchanger 311. Both the heat exchanger 39 and the heat exchanger 311 are connected via lines to a cooling tank 312, which is followed by a recycle 313, which is connected to the loop reactor 26 in the acetone cyanohydrin production 20.

The amidation 40 shown in FIG. 4 initially has a

Acetoncyanhydrinzuführung 41 and a sulfuric acid feed 42, which open into a loop reactor 43. The acetone cyanohydrin feed 41, which is connected to the acetone cyanohydrin work-up 30, flows into the loop of the loop reactor 43 after a pump 44 in front of a mixer 45. The sulfuric acid feed 42 ends before this pump 44. Downstream of the mixer 45, a heat exchanger 46 follows, which in turn discharges into a gas separator 47 on the one hand, a gas outlet 48 and a supply line 49 to another loop reactor 410 goes off. The further loop reactor 410 or a third is comparable to the first loop reactor 43 constructed. From the further loop reactor 410, a feed line 411 passes into a heat exchanger 412, followed by a gas separator 413, from which leads to a gas outlet 414 and an amide line 415 leading to the esterification / saponification 50 / MAS unit 50a.

FIG. 5 shows the esterification 50 in which a solvent line 51 leading to water and organic solvents and an amide line 52 connected to the amidation 40 open into a vessel 53 which can be heated by a boiler heater 54. In the boiler 53 further opens a dashed lines drawn alcohol pipe 55. The alcohol pipe 55 opens into both the upper and in the lower part of the boiler 53. About a marked with a dash dot Esterbrüdenleitung 56, the first boiler 53 is connected to a further boiler 53 ', which has a further boiler heater 54'. This further boiler 53 'is connected to the alcohol pipe 55 both from below and from above. At the top of the boiler 53 ', the ester vapor line 56 connects, which opens into a sump 57 of a column 58. Furthermore, in the upper region of the boiler 53 'is a line for dilute sulfuric acid 59. A boiler unit 510 framed in the dotted ellipse is formed from a heatable vessel 53 and 54 with alcohol pipe 55 and ester vapor line 56. One, two or more of such boiler units may follow each other in a cascade, with each of these boiler units 510 being connected via the ester vapor line 56 to the bottom 57 of the column 58. From the bottom 57 of the column 58 further leads a heavy soother line 511 to the boiler 53 to supply water and organic solvents again the esterification. in the

Upper region, preferably the head, the column 58, connects via a suitable line, a first heat exchanger 512 followed by a further phase separator 513. Both at the top of the column 58 and in the first heat exchanger 512, a first stabilizer feed 414 (stabilizer labeled "S") and a further stabilizer feed 515 may be provided to supply an undesired polymerization preventing inhibitor or stabilizer to the further phase separator 513 is followed by a scrubber 516, in the lower region of which passes a solvent line 517 which opens into the solvent line 51 via a heat exchanger 521. From the upper region of the scrubber 516, a crude ester line is discharged, which discharges into the ester processing 60 the upper portion of the boiler 53 'and the boiler of the last boiler unit 510 outgoing donor acid conduit 59 opens into a flotation tank 519 for separating the solids or in the

Donor acid non-soluble constituents. From the flotation tank 519 is a Spentsäureableitung 520 in the sulfuric acid plant 100 and one, the low-boiling constituents leading, Niedersiederbrüdenleitung 522 for further processing and return to the esterification.

The ester workup shown in FIG. 6 is followed by a crude ester line 61 to the esterification 50, the crude ester feed line 61 discharging into the middle region of a vacuum distillation column 62. This column 62 has column internals 63 and a bottom heater 64 arranged in the lower region of the column 62. From the lower region of the column 62, which represents the bottom of this column, is an ester derivative 65, which opens into the fine ester cleaning 70 and thus freed from low boilers crude ester feeds the fine cleaning. In the upper region of the column 62, usually in the head, a first heat exchanger 66 and a further or a plurality of heat exchangers 67 adjoin via a discharge, followed by a phase separator 69. In the phase separator 69, the mixture originating from the heat exchanger 67 is divided into organic and aqueous constituents, with a recycle 611 in the upper region adjoining the phase separator 69, which opens in the upper region of the column 62. In the lower part of the separator there is a water outlet 610, which opens into the esterification 50 in order to recycle the separated water to the esterification. Connected to the heat exchangers 66 and 67 via a vacuum line 612 is a vacuum generator 613.

In FIG. 7, the ester derivative 65 originating from the ester workup 60 discharges into a distillation column 71. This comprises a plurality of column internals 71 and a bottom sump heater 73 at the bottom of the distillation column 71. From the top of the distillation column 71, a clean ester vapor line 74 passes into a first heat exchanger 75 onto which one (or more) further heat exchanger 76 follow, which are connected to a vacuum generator 717. The outlet of the further heat exchanger 76 has a line from which, on the one hand, an ester recycle line 77 opens into the upper region of the top of the distillation column 71. The ester recycle 77 has a stabilizer feed 79, which is arranged in the ester recycle line 77 in front of a mixer 78. On the other hand, from the line of the further heat exchanger 76 from a Reinesterableitung 710. Connected to these in series, an additional heat exchanger 711 and another heat exchanger 712. This is followed by a molecular sieve container 713 having molecular sieve packages 714. Further purified by the molecular sieve, the pure test ester is transferred to the further processing plant 80 by the pure ester ester removal following the molecular sieve container.

LIST OF REFERENCE NUMBERS

1 plant network

2 sulfuric acid line

3 more sulfuric acid line

4 spent sulfuric acid line - ester

5 spent sulfuric acid line - acid 6 methacrylate acid line

20 acetone cyanohydrin production

30 acetone cyanohydrin workup 40 amidation

50 esterification 50a hydrolysis

60 pre-cleaning

70 final cleaning

80 processing plant

90 Packaging 100 sulfuric acid plant

21 acetone containers

22 hydrocyanic acid tank

23 wash tower

24 cooling elements 25 exhaust pipes

26 loop reactor

27 acetone feed line

28 hydrocyanic acid feed

29 pump 210 catalyst feed line

211 mixers

212 heat exchangers

213 flow resistance

214 cooling pipes 215 heat exchangers

216 collection containers

217 nozzle

218 cooling circuit

219 heat exchanger 220 discharge

221 Stabilizing container

222 sulfuric acid feed

223 derivative

31 heat exchanger 32 vapor feed line

33 column

34 packs

35 column bottom with heat exchanger

36 sump discharge 37 pure product guidance

38 head derivation

39 heat exchangers

310 vacuum pump

311 heat exchangers

312 cooling tanks

313 feedback

41 acetone cyanohydrin feed

42 sulfuric acid feed

43 loop reactor

44 pump

45 mixers

46 heat exchangers

47 gas separators

48 gas discharge

49 supply line

410 additional loop reactor

411 supply line

412 heat exchangers

413 gas separator

414 gas discharge

415 amide line

51 solvent line

52 amide line

53 first boiler

54 first boiler heating

53 ^' further boiler

54 ^' further boiler heating

55 Alkali line

56 Esterbrüdenleitung

57 Column swamp

58 column

59 Spentic acid line

510 boiler unit

511 high-boiler line

512 heat exchangers

513 phase separator

514 stabilizer feed

515 additional stabilizer feed

516 extraction column

517 solvent line

518 raw ester line

519 flotation tanks

520 Spent Acid Dissipation

521 heat exchangers

522 Niedersiederbrüdenleitung

61 crude ester feed

62 vacuum distillation column

63 column internals 64 sump heating

65 ester derivation

66 heat exchangers

67 heat exchangers

68 water supply

69 phase separator

610 water drainage

611 feedback

612 vacuum line

613 negative pressure generator

71 distillation column

72 column internals

73 Column sump heating

74 Reinesterbrüdenleitung

75 first heat exchanger

76 more heat exchangers

77 ester recycling

78 mixers

79 stabilizer metering

710 pure ester discharge

711 additional heat exchanger

712 other heat exchangers

713 molecular sieve containers

714 molecular sieve packs

715 pure ester drainage

716 high-boiler line

717 low boiler withdrawal

Claims

claims

A process for the preparation of alkyl esters of methacrylic acid comprising at least the following steps:

Cleaning the acetone cyanohydrin in a second step,

Preparation of methacrylamide from acetone cyanohydrin in a third step,

Esterification of a methacrylamide and at least one alkyl alcohol-containing reaction mixture in

Presence of a mixture of water and sulfuric acid to alkyl methacrylate in a fourth step and

2. The method according to claim 1, characterized in that the acetone cyanohydrin is freed in a rectification column at least of impurities having a boiling point of more than -5 ⁰ C and less than 100 ⁰ C and these impurities are recycled to the reaction for the preparation of acetone cyanohydrin.

3. The method according to any one of the preceding claims, wherein in the production of methacrylic acid resulting gaseous products are introduced into the reaction mixture of the esterification.

4. The method according to any one of the preceding claims, characterized in that the resulting in the esterification of methacrylamide with at least one alkyl alcohol Methacrylsäurealkylester washed with water and the wash water obtained after the washing in the

Esterification process is attributed.

5. The method according to any one of the preceding claims, characterized in that the mixture of water and sulfuric acid and optionally further substances from the

Esterification first freed by means of flotation of solids and then cooled.

6. The method according to claim 5, characterized in that the cooling is carried out in heat exchangers and the

Mixture of water and sulfuric acid and optionally other substances from the esterification in the heat exchanger is mixed with the washing water obtained in the washing of the methacrylic acid alkyl ester with water.

7. The method according to claim 6, characterized in that the entry of the wash water into the heat exchanger takes place such that the inner surfaces of the heat exchanger are at least partially wetted with the wash water during operation.

8. The method of claim 6 or 7, wherein the entry of the wash water in the heat exchanger is such that during operation not permanently with the mixture of water and sulfuric acid and optionally further

Substances from the esterification in contacting inner surfaces of the heat exchanger are wetted with the wash water.

9. The method according to any one of the preceding claims, characterized in that the methacrylic acid alkyl ester is subjected to a pre-cleaning and a main cleaning.

10. The method according to claim 9, characterized in that substances are separated in the pre-cleaning, which have a lower boiling point than the Methacrylsäurealkylester.

11. The method according to claim 9, characterized in that substances are separated in the main cleaning, which have a higher boiling point than the Methacrylsäurealkylester.

12. The method according to any one of claims 9 to 11, characterized in that

- In the pre-purification substances are separated, which have a lower boiling point than the alkyl methacrylate and these substances are then condensed by cooling, with non-condensed residues remain in the gas phase,

- In the main cleaning substances are separated, which have a higher boiling point than the alkyl methacrylate and this is condensed by cooling, with non-condensed residues remain in the gas phase and

- Non-condensed gaseous residues from the pre-cleaning and non-condensed gaseous residues from the main cleaning of a common

Be subjected to post-condensation.

13. The method according to claim 12, characterized in that a resulting in the common post-condensation condensate is subjected to a phase separation, forming an aqueous and an organic phase.

14. The method according to claim 13, characterized in that the aqueous phase is at least partially recycled to the esterification or the organic phase is returned to the pre-cleaning or both.

15. The method according to any one of the preceding claims, characterized in that the mixture of water and sulfuric acid is optionally introduced together with other substances in a plant for the cleavage of the sulfuric acid.

16. The method according to any one of the preceding claims, characterized in that from the sulfuric acid split plant obtained SO3 is further processed to sulfuric acid and the sulfuric acid thus obtained is used in the production of acetone cyanohydrin.

17. An apparatus for the production of methacrylic acid alkyl esters, comprising fluid-conducting interconnected

a plant element for producing acetone cyanohydrin, followed by;

- a plant element for the production of methacrylamide, followed by;

Methacrylic acid alkyl ester, optionally followed by;

- An installation element for the polymerization, optionally followed by; - An installation part for packaging, wherein the device comprises a rectification column for removing constituents having a boiling point of more than -5 ⁰ C and less than 100 ⁰ C from the produced acetone cyanohydrin and the rectification column is connected in such a fluid-conducting manner with the plant element for the production of acetone cyanohydrin in that the removed constituents are recycled to the reaction for producing acetone cyanohydrin.

18. The device according to claim 17, characterized in that the plant element for the production of methacrylic acid is connected in such a fluid-conducting manner with the plant element for the production of methacrylamide that in the production of methacrylic acid resulting gaseous products in the reaction mixture of

Esterification be initiated.

19. Device according to one of claims 17 or 18, characterized in that the plant element for the production of methacrylic acid ester by esterification of

Methacrylamides having at least one alkyl alcohol at least one scrubber for washing preserved methacrylic acid ester with water and the scrubber is so in fluid communication with the plant element for the production of methacrylic acid ester, that the washing water obtained after the wash is recycled to the esterification process.

20. Device according to one of claims 17 to 19, characterized in that it comprises a plant element, in which the mixture of water and sulfuric acid and optionally other substances from the esterification first freed by means of flotation of solids and then cooled.

21. The apparatus according to claim 20, characterized in that it comprises heat exchangers and the heat exchangers are so in fluid communication with the plant element for the production of methacrylic acid ester that the mixture of water and sulfuric acid and optionally other substances from the esterification in the heat exchanger with the at Washing the Methacrylsäurealkylesters obtained with water

Washing water is mixed.

22. The apparatus according to claim 21, characterized in that the entry of the wash water in the heat exchanger functional elements, such as nozzles, are provided as a supply line, which allow entry of the wash water such that the inner surfaces of the heat exchanger during operation at least partially with the wash water be wetted.

23. The apparatus of claim 21 or 22, characterized in that the entry of the wash water in the heat exchanger functional elements, such as nozzles, are provided as a supply line, which allow entry of the wash water such that during the

Operate not permanently with the mixture of water and sulfuric acid and optionally other substances from the esterification in contact inner surfaces of the heat exchanger are wetted with the wash water.

24. Device according to one of the preceding claims, characterized in that the plant element for purifying the Methacrylsäurealkylesters at least one pre-cleaning element and a main cleaning member so that the methacrylic acid alkyl ester is subjected to a pre-cleaning and a main cleaning.

25. The method according to claim 24, characterized in that the pre-cleaning comprises at least one column for condensing alkyl methacrylate and a device for recondensing gaseous condensables and are in fluid communication with the main cleaning element in such a way that non-condensed gaseous residues from the main cleaning in the device for condensing gaseous substances in the pre-cleaning element can be fed, so that a common post-condensation is possible.

26. The device according to claim 25, characterized in that the at least one device for condensing gaseous substances as part of the pre-cleaning element in fluid-conducting connection with a device for

Phase separation is such that a resulting in the common post-condensation condensate is subjected to a phase separation, which can form an aqueous and an organic phase.

27. The device according to claim 26, characterized in that the device for phase separation is in fluid-conducting connection with the plant element for the production of methacrylic acid alkyl ester, that in the apparatus for phase separation resulting aqueous phase can be at least partially supplied to the production of methacrylic acid alkyl ester.

28. The apparatus of claim 25 or 26, characterized in that the device for phase separation is in fluid-conducting connection with the pre-cleaning element, that the organic phase in the column of the pre-cleaning element, in particular in the column head, can be returned.

29. Use of a methacrylic acid alkyl ester obtainable by a process according to any one of claims 1 to 16 for the production of fibers, films, paints, molding compounds,

Moldings, paper auxiliaries, leather auxiliaries, flocculants and drilling additives.

30 fibers, films, paints, molding compounds, moldings, paper auxiliaries, leather auxiliaries, flocculants or

Drilling additives based on a methacrylic acid alkyl ester obtainable by a process according to any one of claims 1 to 16.