CN100427451C - Preparation method of (meth)acrylic acid or (meth)acrylate - Google Patents

Abstract

The method of the present invention can prevent solids from adhering, accumulating and accumulating when (meth)acrylic acid and (meth)acrylate are purified by distillation, and can stably maintain (meth)acrylic acid and (meth)acrylate The high recovery rate can make the distillation column operate stably and continuously for a long time. According to the present invention, when a composition containing (meth)acrylic acid or (meth)acrylate is distilled in a distillation column having a plurality of trays inside, a type having a cross-sectional shape of wave type, having a plurality of trays is used. A distillation column with a corrugated plate-type non-weir perforated plate with a plurality of through-holes and a flat plate-type non-weir perforated plate with multiple through-holes on the plate as the tray.

Description

Preparation method of (meth)acrylic acid or (meth)acrylate

technical field

The present invention relates to a distillation refining method for preparing (meth)acrylic acid or (meth)acrylate.

In addition, in this specification, (meth)acrylic acid is a generic term for acrylic acid and methacrylic acid, and means either one or both of them. And (meth)acrylic acid refers to the general term of (meth)acrylic acid and (meth)acrylic acid ester prepared from these acids and alcohols, and also refers to at least one of them.

Background technique

As a known method for producing acrylic acid, there is a method using a catalytic gas-phase oxidation reaction of propylene. In this method of obtaining acrylic acid by oxidation of propylene, there are two processes, one is to separate the oxidation of propylene to acrolein and the second-stage oxidation of acrolein to acrylic acid in different reactors and in different The two-stage oxidation process carried out under certain conditions, and the other process is a process of direct oxidation to acrylic acid by one-stage oxidation method.

FIG. 1 is an example of a process diagram showing the production of acrylic acid by a two-stage oxidation process and the reaction of the produced acrylic acid with alcohol to produce acrylate. Propylene, water vapor, and air were supplied as raw material gases to the first reactor, and then to the second reactor. In the first reactor and the second reactor, a catalyst such as a molybdenum-based catalyst is filled. The raw material gas passes through the first reactor and the second reactor, and the propylene in the raw material gas is oxidized in two stages to become a gas containing acrylic acid. The acrylic acid-containing gas is contacted with water in a trapping tower to form an aqueous acrylic acid solution, to which an appropriate extraction solvent is added, extracted in an extraction tower, and the above-mentioned extraction solvent is separated in a solvent separation tower.

Next, acetic acid is separated in an acetic acid separation tower to produce crude acrylic acid, and by-products are separated from the crude acrylic acid in a rectification tower to obtain a refined product of acrylic acid. In addition, after the acrylic acid (refined product) undergoes esterification reaction in the esterification reaction tower, it passes through the extraction tower and the low boiling point component separation tower to become crude acrylate, and the by-product (high boiling point component separation tower) is separated from the crude acrylate in the rectification tower. Component), thus, the above-mentioned crude acrylate becomes a refined acrylate. In the above solvent separation column, acetic acid separation column, low boiling point component separation column, and rectification column, the composition containing acrylic acid or acrylate is distilled.

Moreover, depending on the type of acrylate, such a process as shown in FIG. 2 may also be performed. At this time, the by-product is obtained as the bottom raffinate of the acrylic acid separation tower.

In the acrylate production process shown in FIG. 2 , acrylic acid, alcohol, recovered acrylic acid, and recovered alcohol are supplied to the esterification reactor, respectively. Catalysts such as strong acid ion exchange resins are filled in the esterification reactor. The esterification reaction mixture consisting of produced ester, unreacted acrylic acid, unreacted alcohol, produced water and the like taken out from the reactor is supplied to an acrylic acid separation column.

A bottom liquid containing unreacted acrylic acid is withdrawn from the bottom of the acrylic acid separation tower. A part of the bottom liquid is circulated to the esterification reactor. A part of the above-mentioned bottom liquid is supplied to a high boiling point component separation column, and a high boiling point component is separated from the bottom of the column. The high-boiling-point components are supplied to a high-boiling-point component decomposition reactor (not shown in the figure) to be decomposed. Contains valuable decomposition products produced by decomposition and recycled to the process. The position within the process to be circulated differs depending on process conditions. High-boiling-point impurities such as polymers are removed from the high-boiling-point component decomposition reactor and discharged outside the system.

Acrylic acid ester, unreacted alcohol and produced water are distilled off from the top of the acrylic acid separation tower. Part of the distillate is recycled to the acrylic acid separation column as reflux, and the rest is supplied to the extraction column. Water for alcohol extraction is supplied to this extraction column. The alcohol-containing water flowing out from the bottom of the tower is supplied to the alcohol recovery tower. The distilled alcohol is recycled to the esterification reactor.

The crude acrylate flowing out from the top of the extraction column is supplied to a low boiling point component separation column. In the low boiling point component separation column, the low boiling point component is extracted from the top of the column and circulated to the process. The position within the cyclic process varies according to the process conditions. Crude acrylate from which low boiling point components have been removed is supplied to a refining column. In the refining column, high-purity acrylate is obtained from the top of the column. The bottom liquid is recycled to the process because it contains a large amount of acrylic acid. The position within the cyclic process varies according to the process conditions. The composition containing acrylic acid and acrylate is distilled in the above-mentioned acrylic acid separation column, low boiling point component separation column, and purification column.

In addition, in recent years, in order to recover acrylic acid from the above-mentioned aqueous acrylic acid solution, an azeotropic separation method has also been used instead of the solvent extraction method using an extraction solvent. In this azeotropic separation method, distillation is performed using water and an azeotropic solvent, an azeotropic mixture of water and the azeotropic solvent is distilled from the top of the azeotropic separation tower, and acrylic acid is recovered from the bottom of the tower.

In addition, there is also a method of obtaining acrylic acid by performing a catalytic gas phase oxidation reaction in the presence of a catalyst using propane instead of propylene. As the catalyst, for example, a Mo-V-Te composite oxide catalyst or a Mo-V-Sb composite oxide catalyst is used.

In the case of methacrylic acid and methacrylate, use isobutylene or tert-butanol instead of propylene, and undergo the same oxidation process as described above and the subsequent esterification process to obtain refined methacrylic acid and refined methacrylate thing.

In addition, as a method of preparing (meth)acrylate (acrylate, methacrylate), it is also possible to use an acid or the like as a catalyst to perform a transesterification reaction between a (meth)acrylate of a lower alcohol and a higher alcohol to prepare a higher Alcohol (meth)acrylate method. The crude (meth)acrylate obtained by this transesterification reaction is converted into a refined (meth)acrylate through processes such as catalyst separation, concentration, and rectification.

In the above-mentioned distillation and refining process of crude acrylic acid, crude methacrylic acid, crude acrylate, and crude methacrylate, in order to obtain the rectification effect, a tray tower with various trays inside or a tray column filled with various fillers are generally used. packed tower.

As the tray, there are bubble cap tray (bubble cap), single-flow bubble cap tray, T-type disc valve tray, ballast fractionation tray, perforated plate tray (sieve tray), chimney Type tray, corrugated plate type non-weir perforated plate, flat plate type non-weir perforated plate, baffle type tray, etc.

As the packing, there are Raschig rings, spiral rings, Pall rings, etc. as annular packings, and Bell saddle packings, interlocking saddle packings (Interlocking Saddle) as saddle packings, etc., and other packings include Goode Luo packing, Dixon ring, McMahon packing, vertical plate type structured packing, etc.

The distillation step of (meth)acrylic acid or its ester is characterized in that solids such as polymers are often contained in the process liquid in the distillation step. (Meth)acrylic acid and (meth)acrylate are very easily polymerizable substances. Therefore, in the above-mentioned distillation step, although adding a polymerization inhibitor to the above-mentioned process liquid can inhibit polymerization, even so, the process liquid often contains acrylic acid dimer and other polymer substances. Since this solid is also generated during the distillation operation, the general packed column is not suitable for the above distillation process. In addition, solids are easily generated in the downcomer. Therefore, in the production of (meth)acrylic acid or (meth)acrylate, it is preferable to use a flat-plate non-weir perforated plate for constituting a multilayer distillation column without a downcomer (see, for example, JP-A-49-15153). .

The flat plate non-weir perforated plate has the openings of the above-mentioned through-holes on the same plane, so the liquid falling from the upper stage to the lower stage and the vapor rising from the lower stage to the upper stage pass through the openings under the same conditions. Therefore, the entire opening area cannot be used to allow liquid to pass through, and pressure is generated in the upward direction due to the action of steam, so there is a disadvantage that the opening is easily blocked by solid matter. There is also known a technique that attempts to realize practical use of a commercial device by setting fine details such as the opening ratio of a flat-plate non-weir perforated plate (see, for example, JP-A-2000-300903). But basically still can't overcome the above-mentioned shortcoming that flat plate non-weir perforated plate has.

The above-mentioned solid matter is also newly precipitated or generated by heating (meth)acrylic acid or its ester during the distillation and refining operation. In this way, these solids are caused to adhere, accumulate or accumulate in the tray plate inside the distillation column and the gaps in the packing, which will lead to an increase in the pressure difference between the top and the bottom of the column, and the deterioration of the gas-liquid contact state. clogging etc. As a result, not only the recovery rate of the target product is lowered, but also there is a problem that a stable continuous operation of the distillation column is prevented.

Therefore, in the preparation process of both (meth)acrylic acid and (meth)acrylate, it is desired to develop a distillation and refining process that not only solves the above-mentioned problems, but also can stably obtain the above-mentioned products with a high recovery rate.

Contents of the invention

The object of the present invention is to provide a method for producing (meth)acrylic acid, which can prevent the adhesion and accumulation of such solids during distillation and purification of (meth)acrylic acid and (meth)acrylate , Accumulation, and stably maintain the high recovery rate of (meth)acrylic acid and (meth)acrylate, so that the distillation tower can operate stably and continuously for a long time.

As a result of earnest studies, the present inventors have found that these disadvantages can be overcome by making the internal structure of the distillation column satisfy predetermined conditions, and thus completed the present invention.

That is, the present invention is a method comprising subjecting a composition containing (meth)acrylic acid or (meth)acrylic acid ester (hereinafter collectively referred to as "(meth)acrylic acid") to a distillation column having a multi-stage tray inside. The step of distillation is to extract (meth)acrylic acid or (meth)acrylate from the above composition to prepare (meth)acrylic acid or (meth)acrylate. In this method, as a distillation tower, use A distillation column provided with a corrugated plate type non-weir perforated plate with a plurality of through holes and a flat plate type non-weir perforated plate with a plurality of through holes as trays.

A brief description of the drawings

Fig. 1 is a diagram showing an example of the production process of acrylic acid and acrylate esters.

Fig. 2 is a diagram showing another example of the acrylate production process.

Fig. 3 is a schematic sectional view showing a distillation column having a corrugated plate type non-weir perforated plate.

Fig. 4 is a schematic cross-sectional view showing a distillation column having a flat plate-type non-weir perforated plate.

FIG. 5 is an enlarged cross-sectional view showing X in FIG. 3 .

FIG. 6 is an enlarged cross-sectional view showing Y in FIG. 4 .

Best way to practice the invention

In the present invention, a step of distilling a composition containing (meth)acrylic acid in a distillation column having a multi-stage tray inside, extracting (meth)acrylic acid from the above composition to prepare (meth)acrylic acid kind.

(meth)acrylic acid and (meth)acrylic acid esters are mentioned as a typical compound of the said (meth)acrylic-type. Examples of acrylates include methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2- -Hydroxypropyl ester, methoxyethyl acrylate, etc. Examples of methacrylates include compounds obtained by substituting "methacrylic acid" for "acrylic acid" of the above-mentioned acrylates.

In the present invention, other steps related to the production of (meth)acrylic acid may be included in addition to the above-mentioned distillation step within the range that does not impair the effects of the present invention. As such another process, the process normally performed for manufacturing (meth)acrylic acid is mentioned.

As the (meth)acrylic-containing composition, a composition obtained in a conventional method for producing (meth)acrylic can be used. Examples of such a composition include (meth)acrylic acid itself, an aqueous solution of (meth)acrylic acid, a solution of (meth)acrylic acid using an organic solvent as a solvent, and the like. As the organic solvent, known extraction solvents for extracting (meth)acrylic acid from an aqueous solution of (meth)acrylic acid, known azeotropic solvents that azeotrope with water, and the like can be used.

As a conventional method for producing (meth)acrylic acid, when acrylic acid is taken as an example, the following (1)-(3) etc. are mentioned, for example.

(1) A method comprising the steps of: subjecting propane, propylene, and/or acrolein to catalytic gas-phase oxidation to generate an acrylic acid-containing gas; contacting the acrylic acid-containing gas generated in the oxidation step with water to convert acrylic acid into acrylic acid A trapping process for capturing an aqueous solution; an extraction process for extracting acrylic acid from the aqueous acrylic acid solution using an appropriate extraction solvent; a process for distilling and separating acrylic acid and a solvent from the obtained extract; a process for distilling and refining the separated acrylic acid; The process of supplying the Micheal adduct of acrylic acid obtained after the refining process and the high boiling point component containing the polymerization inhibitor used in each process as raw materials to the decomposition reaction tower and recovering valuable products; A process in which valuable products are supplied to any process following the capture process.

(2) A method comprising the steps of: subjecting propane, propylene, and/or acrolein to catalytic gas-phase oxidation to generate an acrylic acid-containing gas; contacting the acrylic acid-containing gas generated in the oxidation step with water to convert acrylic acid into acrylic acid A trapping process in which the aqueous solution is collected; the azeotropic separation process in which the aqueous acrylic acid solution is distilled in the azeotropic separation tower in the presence of an azeotropic solvent, and the crude acrylic acid is taken out from the bottom of the tower; Acetic acid separation process for acetic acid; purification process for further removing high-boiling point components by distillation from the acrylic acid composition after separating acetic acid; The process of supplying the high boiling point component of the polymerization agent as a raw material to the decomposition reaction tower and recovering valuable products; and the process of supplying the obtained valuable products to any process after the trapping process.

(3) A method comprising the steps of: subjecting propane, propylene, and/or acrolein to catalytic gas-phase oxidation to generate an acrylic acid-containing gas; contacting the acrylic acid-containing gas generated in the oxidation step with an organic solvent to produce acrylic acid Acrylic acid organic solvent solution is collected, while removing water, acetic acid, etc. capture/separation process; from this acrylic acid organic solvent solution by distillation to remove acrylic acid separation process; used in each process containing a polymerization inhibitor, organic solvent, And the process of supplying the high-boiling point component of the Mikel adduct of acrylic acid as a raw material to the decomposition reaction tower and recovering valuable products; the process of supplying the obtained valuable products to any process after the capture/separation process; and , A process of purifying a part of the organic solvent.

(4) (meth)acrylic acid produced by catalytic gas-phase oxidation of propylene or isobutylene; and (meth)acrylic acid produced by catalytic gas-phase oxidation of propane.

As a conventional method for producing (meth)acrylate, when acrylate is taken as an example, for example, an esterification reaction step of reacting acrylic acid with an alcohol using an organic acid or a cationic ion exchange resin as a catalyst, and carrying out As a unit operation for concentrating the crude acrylate liquid obtained in the reaction, there is a method of performing a purification step of extraction, evaporation, and distillation. As a raw material acrylic acid, the acrylic acid produced by the method shown to said (1)-(3), for example can be used. In particular, (meth)acrylic acid ester is obtained by esterifying (meth)acrylic acid prepared by the methods shown in (1) to (4) above.

In each unit operation, it is appropriately selected according to the raw material ratio of acrylic acid and alcohol in the esterification reaction, the type of catalyst used in the esterification reaction, or the respective physical properties of raw materials, reaction by-products, and acrylates. After each unit operation, acrylate products are obtained in the refining tower.

The bottom liquid of the refining tower contains Mikel adducts with acrylates, β-acryloyloxypropionates, β-alkoxypropionates, and β-hydroxypropionates as the main components. . By supplying the above-mentioned tower bottom liquid and/or high-boiling components containing polymerization inhibitors used in each process to the decomposition reaction tower, or returning them to the process, valuable products are recovered.

According to the type of alcohol, acrylic acid, acrylic acid dimer (hereinafter referred to as dimer), acrylic acid trimer (hereinafter referred to as trimer), β-alkoxy propionic acid, β-alkoxy propionic acid Esters are the main components, and the high-boiling components containing polymerization inhibitors used in the preparation process are often obtained from the esterification reaction process or any one of the unit operations in the above-mentioned purification process. This high-boiling point component is also supplied to a decomposition reaction tower as a high-boiling point component containing a Mikel adduct to recover a valuable product, and the valuable product may also be supplied to a reaction step or a purification step.

The aforementioned Mikel adduct refers to a compound formed by the reaction between a compound having an active methylene group and an unsaturated carboxyl compound during the preparation of (meth)acrylic acid. The above-mentioned Mikel adducts of acrylic acid or acrylates refer to, for example, Mikel adducts during the preparation of acrylic acid, dimers, trimers, and acrylic acid tetramers (hereinafter referred to as tetramers). ) etc.; as the Mikel adducts during the preparation of acrylates, the Mikel adducts of acrylic acid formed by adding alkyl esters or cycloalkyl esters with 2 to 8 carbon atoms to the above-mentioned acrylates can be mentioned. Adducts, specifically β-acryloyloxypropionate, Mikel adducts of alcohols, specifically β-alkoxypropionate, dimers, trimers, Tetramer, ester body of trimer, ester body of tetramer, β-hydroxypropionic acid, β-hydroxypropionate, etc.

In addition, in the production process of (meth)acrylic acid, as described above, in order to suppress the generation of polymers in the production process, a polymerization inhibitor is generally used.

Specific examples of the polymerization inhibitor include copper acrylate, copper dithiocarbamate, phenolic compounds, phenothiazine compounds, and the like.

Copper dithiocarbamate includes copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper dipropyldithiocarbamate, copper dibutyldithiocarbamate Copper dialkyl dithiocarbamate; copper ethylene dithiocarbamate, copper tetramethylene dithiocarbamate, copper pentamethylene dithiocarbamate, copper hexamethylene dithiocarbamate Copper cyclic alkylene dithiocarbamate such as copper carbamate; Copper cyclic oxydialkylene dithiocarbamate such as copper oxydiethylene dithiocarbamate, etc.

Examples of the phenolic compound include hydroquinone, metokinol, pyrogallol, catechol, resorcinol, phenol, or cresol.

Examples of phenothiazine compounds include phenothiazine, bis-(α-methylbenzyl)phenothiazine, 3,7-dioctylphenothiazine, bis-(α-dimethylbenzyl)phenothiazine Thiazide etc.

Although substances other than the above-mentioned compounds may be contained in the process, there are no particular limitations on the type as long as they do not adversely affect the production and purification of (meth)acrylic acid.

In the above-mentioned distillation step, a distillation column having a corrugated plate type non-weir perforated plate and a flat plate type non-weir perforated plate as trays is used. The distillation step is not particularly limited as long as it can distill a (meth)acrylic acid-containing composition. As such a process, for example, the extraction process as described above; the process of separating the solvent such as the extraction solvent from the acrylic acid; the process of refining the separated acrylic acid; the azeotropic separation process; the acetic acid separation process; Part of the purification process of the solvent; and unit operations such as extraction and distillation. According to the present invention, better effects can be obtained in a system that is relatively easy to produce the above-mentioned solids, for example, in a system with a higher concentration of (meth)acrylic acid in the above-mentioned composition, and more specifically, when the above-mentioned When the distillation step is a step of purifying (meth)acrylic acid, a better effect can be obtained.

The above-mentioned distillation column is not particularly limited as long as it is a distillation column that can be provided with a corrugated plate type non-weir perforated plate and a flat plate type non-weir perforated plate as trays. As such a distillation column, a distillation column generally used in a chemical factory, such as a tray column, can be used, for example. The number of trays (stages) provided in the above-mentioned distillation column can be appropriately set according to various conditions such as the target substance and the type of trays, and is usually preferably 10 to 50 when distilling (meth)acrylic acid.

The above-mentioned corrugated plate-type non-weir porous plate, as shown in Fig. 3 and Fig. 5, is a kind of perforated plate processed into a corrugated plate shape, for example, which has a corrugated cross-sectional shape and has a plurality of through holes. The above-mentioned corrugated plate-type non-weir porous plate, as long as it is a porous plate that can achieve an appropriate balance between ventilation and liquid flow during the distillation process of (meth)acrylic acid, but preferably has an opening rate of 5 to 30%. perforated plate.

In the corrugated plate type non-weir perforated plate, the through-holes may be provided in any of the mountain portion, the valley portion, and the side portion of the mountain or the valley. Moreover, regarding the cross-sectional shape of the corrugated plate type non-weir perforated plate, the upper side of the midline connecting the height of the midpoint between the upper end of the convex part and the lower end of the concave part is called "mountain", and the lower side of the midline is called "valley". In addition, "side" refers to a surface between the top of a mountain and the bottom of a valley.

In addition, the above-mentioned "wave type" refers to a shape in which mountains and valleys continuously repeat in the cross-sectional shape, and a shape in which the surface of the plate formed from the top of the mountain to the bottom of the valley becomes inclined. The above-mentioned "wave pattern" may be, for example, a shape in which mountains and valleys are formed by continuous curves like a sine wave, or may be formed by a combination of intermittent lines, such as a shape formed by connecting pulse waves with hypotenuses. shape. In addition, the above-mentioned "wave pattern" is composed of repeated unit shapes consisting of mountains and valleys, and the unit shapes may be the same or different.

As shown in Fig. 4 and Fig. 6, the flat plate type non-weir perforated plate is a flat plate having a plurality of through holes. The above-mentioned flat plate non-weir porous plate may be a porous plate that can achieve an appropriate balance between gas flow and liquid flow during the distillation process of (meth)acrylic acid, and is preferably a porous plate with an opening ratio of 5 to 30%, for example. In addition, in FIGS. 3 to 6 , the solid line arrows in the figures indicate the flow direction of the vapor in the distillation column, and the broken line arrows indicate the flow direction of the liquid.

In the distillation operation of (meth)acrylic acid, flat-plate non-weir perforated plates are generally used. Generally speaking, since there is no downcomer (downcomer) in the distillation column using a weir-free perforated plate, the entire section area of the distillation column can be used for gas-liquid contact, so that the dispersion of the liquid is uniform. In addition, it also has the feature that the throughput is higher than that of bubble-cap trays.

However, as described above, the flat-plate non-weir perforated plate has the openings of the above-mentioned through-holes on the same plane. Therefore, as shown in FIG. 6 , the liquid falling from the upper stage to the lower stage and the vapor rising from the lower stage to the upper stage pass through the through holes in opposite directions. Therefore, since not all of the opening area is used for the passage of the liquid, and the upward pressure caused by the vapor is received, there is a disadvantage that the through hole is easily blocked by solid matter. This shortcoming can be solved by adjusting the pore size or opening ratio to a certain extent.

The corrugated plate non-weir porous plate is different from the flat plate non-weir porous plate. Because the openings of the through holes are not in the same plane, the liquid mainly flows downward from the valley part, and the steam passes through the mountain part. The solids in the liquid are concentrated in the lower part of the valley and discharged to the lower section, so the solids are difficult to settle and accumulate. In addition, as shown in FIG. 5 , in the through holes of the corrugated plate type non-weir porous plate, the liquid passes through the through holes along the vertical direction, while the vapor passes through the through holes along the axis direction of the through holes. Therefore, it is structurally easy to suppress clogging of the through-holes due to solid matter.

In addition, by processing corrugated plates, when installed in the same distillation tower, the surface area can be larger than that of a flat plate without weirs, and more through holes can be provided.

Furthermore, even if the solid matter clogs the through-holes of the valley part, the liquid can also fall through the through-holes of the mountain part and the side part of the mountain or valley. Stable operation for a long time. Moreover, if the hole diameter of the through-hole in the valley part through which the solid matter is relatively easy to pass is slightly larger, then a better effect can be obtained.

In addition, even if the through-holes in the valley portion are clogged, the through-holes in the side portion can be used for gas-liquid contact, and therefore, the dispersion of the liquid remains uniform. Utilizing this feature, problems such as adhesion, accumulation, and accumulation of solids can be solved.

Furthermore, in the distillation of a liquid containing (meth)acrylic acid, a phenomenon in which a polymer is formed or accumulated on the back of the tray has been observed. One of the main reasons for this is an increase in the residence time of liquids that reflux or adhere to the back of the tray. Since the back (lower surface) of the flat-plate non-weir perforated plate is flat, the liquid adhering to the lower surface is difficult to fall down, so the residence time tends to be longer.

Due to the shape of the structure of the corrugated plate without weir, the back of the plate is inclined, so that the liquid existing on the back of the plate is easy to drip downward, which is the main reason why the above-mentioned disadvantages can be avoided.

In addition, the corrugated plate type non-weir perforated plate has an extremely simple structure similar to the flat plate type non-weir perforated plate, and therefore has the advantage of extremely low construction costs such as the production cost and installation cost of the distillation tower.

In this way, in the flat plate type non-weir perforated plate, in order to make the generated solid matter fall and suppress the occurrence of solid matter in the distillation tower, the pore diameter must be relatively large, and in the corrugated plate type non-weir perforated plate, it is different from the flat type non-weir perforated plate. In order to suppress the generation of solids in the distillation column, it is not necessary to increase the pore diameter compared to the perforated plate.

In addition, in the non-weir perforated plate, although the reduction of the pore size can improve the distillation effect (tray efficiency) of each non-weir perforated plate, the pressure difference of each non-weir perforated plate becomes larger. As a result, the overall pressure difference of the distillation column (the pressure difference between the top and the bottom of the column) increases, and the pressure at the bottom of the column increases, thereby raising the temperature (increasing the boiling point) at the bottom of the column, which tends to increase the generation of solids.

The present invention is characterized in that, in the method of introducing (meth)acrylic acid and/or (meth)acrylic acid ester into a distillation tower for purification, as the above-mentioned distillation tower, a corrugated plate type non-weir porous plate and a flat plate type non-weir porous plate are used inside. Board both.

In the present invention, by arranging both the corrugated plate type non-weir perforated plate that can reduce the aperture of the through hole and the flat plate type non-weir porous plate that must make the aperture of the through hole relatively large from the viewpoint of preventing clogging, at least effective distillation can be achieved (A Base) acrylic acid, prevent the pressure difference between the top and the bottom of the distillation tower from rising, and prevent the internal clogging of the distillation tower caused by solids.

The number and setting ratio of the corrugated plate type non-weir perforated plate and the flat type non-weir perforated plate can be determined according to the diameter of the through hole in each non-weir perforated plate, the pressure difference generated by each piece, and the effect of each piece relative to distillation. Appropriate setting. In the present invention, the ratio of the number of installed corrugated plate-type non-weir perforated plates to flat plate-type non-weir perforated plates is preferably 1:1 to 4:1. If the ratio of the number of corrugated plate-type non-weir perforated plates is less than 1, when the through-hole diameter is selected from the viewpoint of high-efficiency distillation, the solids produced on the flat-type non-weir perforated plates often shorten the continuous operation time of the distillation tower. . If the ratio of the number of corrugated plate-type non-weir perforated plates is greater than 4, the overall pressure difference of the distillation tower will increase and the temperature at the bottom of the tower will often increase, so solids are likely to be generated, thereby shortening the continuous operation time of the distillation tower.

Inside the distillation tower, the corrugated plate type non-weir perforated plate and the flat type non-weir perforated plate can be alternately arranged one by one, or can be arranged alternately according to the specified number of pieces, can also be arranged according to types, and can also be arranged irregularly. . In the present invention, the perforated plate arranged at the lowermost section inside the distillation column is preferably a corrugated plate type non-weir perforated plate.

At the bottom of the tower, the boiled gas in the reboiler causes splashes, which makes the bottom liquid containing both gas and solids fly up, so that the solids are easy to adhere to the back of the bottom tray. The solid matter tends to remain in the flat plate non-weir perforated plate, but since the corrugated plate type non-weir perforated plate (as described above) is composed of inclined plates, liquid flow occurs on the back of the plate to wash off the solid matter.

When a plurality of corrugated plate-type non-weir perforated plates are continuously arranged, the direction in which the waves continue or the direction in which the mountains and valleys of the waves extend are arranged in a crossed manner. It is preferable in consideration of the viewpoint, and it is particularly preferable to arrange it vertically.

In addition, when a plurality of flat non-weir perforated plates are continuously installed, from the viewpoint of improving the dispersion of the liquid in the distillation column to the horizontal direction, the cross-sectional shape of the through holes and the through holes can be respectively arranged in the upper and lower sections although the opening ratio is the same. The configuration of the flat plate without weir perforated plate is different.

In the present invention, it is preferable that the ratio of the wave height to the wavelength (wave height/wavelength) is 1/2 to 1/20 regarding the cross-sectional shape of the corrugated plate-type non-weir porous plate. The "wavelength" refers to the horizontal distance from the top of a mountain to the top of an adjacent mountain, which varies depending on the substance to be distilled, the diameter of the distillation tower, distillation conditions, etc., and is preferably 20 to 6,000 mm. The "wave height" refers to the vertical distance from the peak of the mountain to the lowest point of the valley, which varies depending on the substance to be distilled, the diameter of the distillation tower, distillation conditions, etc., and is preferably 10 to 300 mm.

Weirless perforated plates for distillation must be constantly wetted by the liquid. Once dry (that is, the state without a polymerization inhibitor), it is easy to produce solids. If the above ratio is greater than 1/2, the depth of the liquid remaining on the corrugated plate-type non-weir perforated plate will increase, causing the pressure difference of each corrugated plate-type non-weir perforated plate to become too large, resulting in an increase in the overall pressure difference of the distillation tower. Large, so the temperature at the bottom of the tower rises, and solids are prone to occur, which often shortens the continuous operation time of the distillation tower. If the above-mentioned ratio is less than 1/20, it becomes the same as the flat plate non-weir perforated plate, the liquid flow in the corrugated part becomes very small, and it is difficult to remove the generated solids, so the continuous operation time of the distillation column is often shortened .

In the present invention, the through-hole diameter of the corrugated plate-type non-weir perforated plate is preferably smaller than the through-hole diameter of the flat plate-type non-weir perforated plate. Specifically, the ratio b/a of the through-hole diameter a of the corrugated non-weir perforated plate to the through-hole diameter b of the flat plate-type non-weir perforated plate is preferably 1.1 to 3.0. If the above ratio is less than 1.1, although the corrugated plate-type non-weir perforated plate has a high effect of alleviating the pressure difference of the distillation tower, clogging is likely to occur in the flat-type non-weir perforated plate, which often shortens the continuous operation time of the distillation tower. If the above-mentioned ratio is greater than 3, the relative difference in velocity of the gas blown from the through holes of the two kinds of non-weir perforated plates will increase, which will easily cause the airflow in the distillation tower to be disturbed, thereby easily producing solids, which tends to make the distillation tower The continuous running time is shortened.

Regarding the through-holes in the above-mentioned corrugated plate-type non-weir perforated plate and the above-mentioned flat-type non-weir perforated plate, the cross-sectional shape (shape of the opening) of the through-hole is usually circular, but it may also be rectangular, elliptical, polygonal, etc. non-circular. In addition, the cross-sectional shape of one through hole may be a single shape, or may continuously change from a certain shape to another shape. Furthermore, the above-mentioned through-holes generally have a vertical cross-sectional shape of a rectangle, but other shapes such as trapezoidal or bell-shaped in which the lower side is longer than the upper side may also be used.

In addition, in one non-weir perforated plate, only the through holes with the same cross-sectional shape may be provided, or a plurality of through holes with different cross-sectional shapes may be provided. Moreover, in a non-weir perforated plate, the through holes can be arranged on the whole perforated plate according to the uniform distribution, and the through holes can also be arranged according to the uneven distribution (for example, some through holes are arranged in the center of the perforated plate, and some through holes are arranged in the porous plate. The peripheral portion of the plate is less provided with some through holes).

The through hole diameter of the corrugated plate type non-weir perforated plate is generally 10 to 40 mm, and this range is also preferred in the present invention. In addition, it is preferable that the diameter of the through-holes of the above-mentioned flat plate-type porous plate without weirs is 10 to 50 mm. In the present invention, in these perforated plates without weirs, only through-holes with the same diameter may be provided, or multiple through-holes with different diameters may be provided.

The above-mentioned distillation column may have a structure other than the above-mentioned non-weir perforated plate within the range that does not impair the effect of the present invention. As such other structures, for example, baffles provided at the raw material liquid supply port of the distillation column for deflecting the supplied raw material liquid, and top plates for preventing the raw material liquid of the baffles from splashing upward , a reboiler for heating the raw material liquid supplied to the distillation column, various nozzles appropriately arranged in the liquid flow path, trays other than the above-mentioned non-weir perforated plate, and the above-mentioned packing.

Among the above-mentioned reboilers, known reboilers used for heating the bottom liquid of a distillation column can be used. The above-mentioned reboiler is generally divided into the case where it is installed in the column and the case where it is installed outside the column. In the present invention, it is preferably installed outside the column. The type of reboiler is not particularly limited. Specifically, column bottoms such as vertical fixed tube sheet type, horizontal fixed tube sheet type, U-shaped tube type, double tube type, spiral type, block (corner block) type, plate type, thin film evaporator type, etc. Various heat exchangers for liquid heating.

Various structural materials in the above-mentioned distillation tower can be selected according to the easily polymerizable compound to be treated and its temperature conditions, and there is no special limitation in the present invention. For example, stainless steels such as SUS304, SUS304L, SUS316, SUS316L, SUS317, SUS317L, SUS327; or Hastelloy corrosion-resistant nickel-based alloys are also suitable for use in the present invention. From the viewpoint of corrosion resistance, the above-mentioned materials may be selected according to the physical properties of the corresponding liquids.

【Example】

The present invention will be described more specifically with reference to Examples and Comparative Examples below.

<Example 1>

Acrylic acid was distilled using a vacuum distillation column with a diameter of 1,000 mm. The vacuum distillation column has a column tank for supplying a raw material liquid for distillation, a column body for passing the vapor of the heated liquid in the column tank, and a condenser for condensing the vapor discharged from the top of the column.

A reboiler for heating the supplied raw material liquid is installed in the column pot. The above-mentioned tower body is a plate tower. The tower body has a structure in which 30 arbitrary perforated plates can be arranged as trays.

In this example, a total of 30 corrugated plate-type perforated plates without weirs and flat plate-type perforated plates without weirs were installed as the above-mentioned trays. In this embodiment, the perforated plate group arranged from bottom to top according to the order of four corrugated plate-type non-weir perforated plates and one flat-type non-weir perforated plate is regarded as a group, and the six groups of perforated plates are arranged in a bottom-to-bottom order. Arranged in the order above, configure the non-weir perforated plate as the tray. That is, a total of 30 stages of non-weir perforated plates were installed in the vacuum distillation column.

In addition, the number of stages of the non-weir perforated plate (tray) is counted from 1 to 30 stages in the order from bottom to top. As the above-mentioned corrugated plate type non-weir perforated plate, a corrugated plate type non-weir perforated plate having holes with a diameter of 20 mm is used. Weirless perforated plate. As the above-mentioned flat-type non-weir perforated plate, a flat-type non-weir perforated plate having holes with a pore diameter of 25 mm was used. The opening rate of the corrugated plate type non-weir perforated plate (the ratio of the opening area to the surface area of the non-weir perforated plate assuming that no through holes are formed) is 23%, and the opening rate of the flat plate type non-weir perforated plate is 23%. %.

In this example, a corrugated plate-type non-weir perforated plate is used as the bottommost perforated plate of the distillation column. The 30-stage perforated plate (tray) corresponds to 9 stages in the number of theoretical plates. Furthermore, in the above-mentioned corrugated plate-type non-weir perforated plate, it is designed so that the extension directions of the peaks and valleys of the corrugated plate are perpendicular to each other on the perforated plate having a vertical positional relationship.

An acrylic acid aqueous solution (hereinafter abbreviated as (A) liquid) containing 55% of acrylic acid, 1.5% of acetic acid, 0.3% of formaldehyde and a small amount of formic acid by mass concentration was used as the raw material liquid for distillation. In addition, toluene was used as an azeotropic solvent, and the vacuum distillation column described above was used as a dehydration distillation column to operate.

Initially, after stabilizing the distillation column with toluene, liquid (A) was supplied at 1,100 kg per hour on the tray of the 16th stage, and toluene was supplied at 3,100 kg per hour on the tray of the 30th stage. The pressure at the top of the tower was controlled at 14.0 kPa, and hydroquinone and phenothiazine were supplied as polymerization inhibitors from the top of the tower. The supply amounts of these polymerization inhibitors were adjusted so that the concentrations of the polymerization inhibitors in the bottom liquid were 800 ppm for hydroquinone and 500 ppm for phenothiazine. Air was supplied to the bottom of the tower at 500 liters per hour.

After the distillate condensed by the condenser at the top of the tower is left standing and separated in the decanter, all the azeotropic solvent phase is refluxed to the distillation tower, and the water phase is drawn out. The reboiler is heated with steam at a gauge pressure of 196 kPa. In this way, the pressure at the top of the column was set to 15.5 kPa, and the temperature of the bottom liquid was set to 82° C., and the vacuum distillation column was continuously operated. During operation, in the bottom raffinate extracted from the bottom of the tower, except for acrylic acid, it contains 2.3% of acetic acid, 0.6% of water, 15% of toluene by mass composition, and also contains a small amount of polymerization inhibitor in addition. The experimental conditions and results in this example are shown in Table 1.

The experimental conditions and their results are shown in Table 1.

The pressure difference between the tower top and the tower bottom of the distillation tower in operation is 6.5 kPa or less, does not rise, and can continue to operate stably. After 3 months, when the operation was stopped and the distillation column was inspected from the open point, a small amount of acrylic acid polymer was found on the tray of the second stage.

<Comparative example 1>

As shown in Table 1, in Example 1, the dehydration distillation experiment was performed in the same manner as in Example 1 except that all the trays were changed to flat plate-type non-weir perforated plates. In operation, the composition of the raffinate extracted from the bottom of the tower is the same as in Example 1.

Similar to Example 1, the process operation can be continued stably, but the pressure difference between the top and the bottom of the distillation tower rose from 8.5kPa to 16kPa. After 3 months, the operation was stopped, and when the distillation column was inspected from the open point, a large amount of acrylic acid polymer was found on the trays of the first to fifth stages.

<Comparative example 2>

As shown in Table 1, make the 1st and 5th sections flat-type non-weir perforated plates, and make the 2nd to 4th sections be corrugated plate-type non-weir perforated plates. Four perforated plates without weirs and one plate-type perforated plate without weirs are arranged from bottom to top as a group. The experiment of dehydration distillation was performed similarly to Example 1 except the perforated plate which is a tray. In operation, the composition of the raffinate extracted from the bottom of the tower is the same as in Example 1.

Same as Example 1, the process operation can be carried out stably and continuously, but the pressure difference between the top and the bottom of the distillation tower rises from 8.5kPa to 15kPa. After 3 months, the operation was stopped, and when the distillation tower was inspected from an open point, a large amount of acrylic acid polymer was found under the flat-type non-weir perforated plate in the 0th stage.

<Example 2>

In this embodiment, as shown in Table 1, the perforated plate group arranged from bottom to top according to the order of 3 corrugated plate-type non-weir perforated plates and 2 flat-type non-weir perforated plates is taken as a group. Six groups of plate groups are arranged in order from bottom to top, and are configured as perforated plates as trays. In addition, as a flat plate type non-weir perforated plate, a flat type non-weir perforated plate having a hole diameter of 30 mm and an opening ratio of 27% was used. Except for this, in this example, the experiment of dehydration distillation was performed similarly to Example 1. In operation, the composition of the raffinate extracted from the bottom of the tower is the same as in Example 1.

Similar to Example 1, the pressure difference between the top and the bottom of the distillation column was 5.5 kPa, and there was no rise, and the operation could be continued stably. After 3 months, the operation was stopped, and when the distillation column was inspected from the open point, a small amount of acrylic acid polymer was found on the trays of the 3rd and 4th stages.

<Comparative example 3>

As shown in Table 1, make the 1st to 5th sections flat-type porous plates without weirs, and in the 6th section or above, use 3 corrugated plate-type non-weir perforated plates and 2 flat-type non-weir perforated plates. The perforated plate group configured from bottom to top in the sequence is taken as a group, and the perforated plate used as the tray is configured by arranging the five perforated plate groups in a bottom-up order. In addition, the same as in Example 2 The experiment of dehydration distillation was performed similarly. In operation, the composition of the raffinate extracted from the bottom of the tower is the same as in Example 2.

Similar to Example 2, the process operation can be continued stably, but the pressure difference between the top and the bottom of the distillation tower rose from 5.5 kPa to 15 kPa. After 3 months, the operation was stopped, and when the distillation column was inspected from the open point, a large amount of acrylic acid polymer was found on all the upper and lower trays of the first to fourth stages.

<Example 3>

As shown in Table 1, as the above-mentioned corrugated plate type non-weir porous plate, a corrugated plate type non-weir porous plate having a through hole with a diameter of 25 mm and an opening ratio of 24% is used. The height of the corrugated plate type non-weir perforated plate is 30 mm. As the above-mentioned flat type non-weir perforated plate, a flat type non-weir perforated plate with a hole diameter of 30 mm and a porosity of 24% is used. In addition, The experiment of dehydration distillation was performed similarly to Example 1. In operation, the composition of the raffinate extracted from the bottom of the tower is the same as in Example 1.

Similar to Example 1, the pressure difference between the top and the bottom of the distillation column was 5.5 kPa, and there was no rise, and the operation could be continued stably. After 3 months, the operation was stopped, and when the distillation column was checked from an open point, no polymer of acrylic acid was found.

<Comparative example 4>

As shown in Table 1, in Example 3, the dehydration distillation experiment was performed in the same manner as in Example 3 except that all the trays were changed to flat plate-type non-weir perforated plates. In operation, the composition of the raffinate extracted from the bottom of the tower was the same as in Example 3.

As in Example 3, the operation could be continued stably, but the pressure difference between the top and the bottom of the distillation column rose from 8.2 kPa to 16 kPa. After 3 months, the operation was stopped, and when the distillation column was inspected from the open point, a large amount of acrylic acid polymer was found on all the upper and lower trays of the first to fourth stages.

<Example 4>

As shown in Table 1, the 1st to 20th sections are made of corrugated plate-type non-weir perforated plates, and the 21st section or above is made of flat-plate type non-weir perforated plates. Experiment with dehydration distillation. In operation, the composition of the raffinate extracted from the bottom of the tower is the same as in Example 3.

As in Example 3, the pressure difference between the top and the bottom of the distillation column was 5.5 kPa, which did not rise, and the operation could be continued stably. After 3 months, the operation was stopped, and when the distillation column was checked from an open point, no polymer of acrylic acid was found.

【Industrial Utilization Possibility】

According to the present invention, since (meth)acrylic acid is distilled using a distillation tower having a corrugated plate-type non-weir perforated plate and a flat-type non-weir perforated plate, the overall pressure difference of the distillation tower can be reduced, and polymerization of (meth)acrylic acid can be prevented. It can stably maintain a high recovery rate of (meth)acrylic acid, and can stably carry out continuous operation of the distillation tower for a long time.

In addition, in the present invention, if the corrugated plate type non-weir perforated plate is used as the bottom non-weir perforated plate in the distillation tower, it can prevent the clogging caused by solids in the distillation tower, and prevent the overall pressure difference of the distillation tower from rising. Consider, has a better effect.

In addition, in the present invention, if the ratio of the number of corrugated plate-type non-weir perforated plates and flat plate-type non-weir perforated plates installed in the distillation tower is 1:1 to 4:1, from the viewpoint of preventing the overall pressure difference of the distillation tower from increasing Consider, has a better effect.

In addition, in the present invention, if the ratio of the wave height to the wavelength (wave height/wavelength) is 1/2 to 1/20 in the cross-sectional shape of the corrugated plate type non-weir perforated plate, the long-term continuous From the standpoint of operation and the reduction of the number of tray plates due to the improvement of separation efficiency, it has a better effect.

In addition, in the present invention, if the through-hole aperture a of the corrugated plate type non-weir perforated plate is set to be smaller than the through-hole aperture b of the flat plate type non-weir perforated plate, then from the long-term continuous operation of the distillation tower and the improvement of the separation efficiency. From the viewpoint of achieving the purpose of reducing the number of tray plates, there is a better effect, and if b/a is set to 1.1 to 3, there is a further effect.

Claims (9)

1, the preparation method of a kind of (methyl) vinylformic acid or (methyl) acrylate, this method comprises that the composition that will contain (methyl) vinylformic acid or (methyl) acrylate carries out the distillatory operation with inner distillation tower with multistage column plate, and from above-mentioned composition, take out (methyl) vinylformic acid or (methyl) acrylate, it is characterized in that

As above-mentioned distillation tower, use to be equipped with to have a plurality of cross-sectional shapes and do not have the weir porous plate and on flat board, have the distillation tower of the flat no weir porous plate of a plurality of communicating poress, and the above-mentioned corrugated plate dst that has as the above-mentioned column plate of hypomere does not have the weir porous plate as above-mentioned column plate as the corrugated plate dst of wave mode communicating pores.

2, the method described in the claim 1 is characterized in that, in the above-mentioned distillation process, distills (methyl) vinylformic acid or (methyl) acrylate refining.

3, the method described in the claim 1 is characterized in that, the number ratio that the corrugated plate dst that is provided with in the above-mentioned distillation tower does not have weir porous plate and flat no weir porous plate is 1: 1～4: 1.

4, the method described in the claim 1 is characterized in that, does not have in the cross-sectional shape of weir porous plate at above-mentioned corrugated plate dst, and the height of ripple is with respect to the ratio of wavelength, and promptly height/the wavelength of ripple is 1/2～1/20.

5, the method described in the claim 1 is characterized in that, above-mentioned corrugated plate dst does not have the communicating pores aperture of the communicating pores aperture of weir porous plate less than above-mentioned flat no weir porous plate.

6, the method described in the claim 5 is characterized in that, the communicating pores aperture b of above-mentioned flat no weir porous plate is 1.1～3 with respect to the ratio b/a that above-mentioned corrugated plate dst does not have the communicating pores aperture a of weir porous plate.

7, the method described in the claim 1 is characterized in that, (methyl) vinylformic acid in the above-mentioned composition is that the catalytic vapor phase oxidation reaction by propylene or iso-butylene makes.

8, the method described in the claim 1 is characterized in that, (methyl) vinylformic acid in the above-mentioned composition is the vinylformic acid that the catalytic vapor phase oxidation reaction by propane makes.

9, the described method of each in the claim 1～8 is characterized in that, (methyl) acrylate in the above-mentioned composition is to carry out esterification by (methyl) vinylformic acid by each the described method preparation in the claim 1～8 to obtain.

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