CN217527505U - Dimethyl maleate production system - Google Patents

Abstract

The utility model discloses a dimethyl maleate production system relates to chemical industry technical field to methanol needs are excessive greatly in solving single esterification reaction and the double esterification reaction, leads to methanol circulation energy consumption height, the big problem of equipment load. The production system for preparing the dimethyl maleate comprises: the device comprises a single esterification reactor and a double esterification reactor which are respectively communicated with a first feeding pipe and a second feeding pipe, wherein the single esterification reactor and/or the double esterification reactor are adiabatic reactors, a discharge port of the single esterification reactor is communicated with a feed port of the fixed bed double esterification reactor, a discharge port of the double esterification pre-reactor is communicated with a tower kettle inlet of a rectifying tower, a tower kettle outlet of the rectifying tower is communicated with a feed port of the rectifying tower, and the feed port of the rectifying tower is also communicated with the second feeding pipe. The utility model provides a pair of dimethyl maleate production system is applied to production organic chemical raw materials dimethyl maleate.

Description

Dimethyl maleate production system

Technical Field

The utility model relates to a chemical industry field especially relates to a dimethyl maleate production system.

Background

Dimethyl maleate is an important organic chemical raw material and can be used for producing 1,4-butanediol, tetrahydrofuran and gamma-butyrolactone by catalytic hydrogenation, and can be prepared by the mono-esterification reaction and the di-esterification reaction of cis-maleic anhydride and methanol.

In the related technology, the single esterification reaction can be realized by adopting a monoester fixed bed, and the double esterification reaction is realized by adopting a reaction rectification mode. In order to improve the conversion rate of the cis-maleic anhydride, the methanol needs to be greatly excessive in the mono-esterification reaction and the di-esterification reaction, so that the methanol has high circulating energy consumption and large equipment load.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a dimethyl maleate production system to when improving cis-maleic anhydride's conversion rate, reduce methyl alcohol circulation energy consumption and equipment load.

In a first aspect, the utility model provides a pair of dimethyl maleate production system, include: the single esterification reactor is used for respectively communicating a first feeding pipe and a second feeding pipe, the first feeding pipe is used for conveying maleic anhydride, and the second feeding pipe is used for conveying methanol;

the double-esterification reactor is characterized in that the single-esterification reactor and/or the double-esterification reactor is/are of an adiabatic reactor, a discharge hole of the single-esterification reactor is communicated with a feed hole of the double-esterification reactor, and the feed hole of the double-esterification reactor is also communicated with the second feed pipe;

and the rectifying tower comprises a tower kettle and a catalytic reaction section positioned above the tower kettle, a discharge port of the double esterification reactor is communicated with an inlet of the tower kettle of the rectifying tower, an outlet of the tower kettle of the rectifying tower is communicated with a feed port of the rectifying tower, and the feed port of the rectifying tower is also communicated with a second feed pipe.

Compared with the prior art, the utility model provides an among the dimethyl maleate production system, first inlet pipe and second inlet pipe communicate with the monoester reactor respectively, consequently, can utilize first inlet pipe can carry along maleic anhydride to the monoester reactor, can utilize the second inlet pipe to carry methyl alcohol to the monoester reactor. At the moment, cis-maleic anhydride and methanol enter a mono-esterification reactor to carry out mono-esterification reaction to obtain monomethyl maleate for discharging. Meanwhile, a discharge hole of the mono-esterification reactor is communicated with a feed hole of the double-esterification reactor, and the discharged monomethyl maleate can enter the double-esterification reactor to carry out double-esterification reaction to obtain discharged dimethyl maleate. And because the type of the mono-esterification reactor and/or the double-esterification reactor is an adiabatic reactor, the reaction speed of the mono-esterification reaction and/or the double-esterification reaction is high, and simultaneously, a large amount of reaction heat generated in the reaction process is generated, so that abundant reaction heat is stored in the discharged monomethyl maleate, and based on the reaction heat, when the discharge port of the double-esterification reactor is communicated with the inlet of the tower kettle of the rectifying tower, the discharged dimethyl maleate can enter the rectifying tower, and the methanol contained in the discharged monomethyl maleate is recovered in the tower kettle of the rectifying tower by utilizing the abundant reaction heat stored in the discharged dimethyl maleate. The catalytic reaction section is positioned above the tower kettle, and the outlet of the tower kettle of the rectifying tower is communicated with the feed inlet of the rectifying tower, so that the methanol can enter the catalytic reaction section in the rectifying tower to continuously react with unreacted methanol in the maleic acid monoester and diester discharge, thereby improving the conversion rate of maleic anhydride. It can be seen that the embodiment of the utility model provides a dimethyl maleate production system can not only improve the conversion rate of cis-maleic anhydride for adiabatic reactor through setting for single esterification reactor and/or two esterification reactors, can also utilize single esterification reaction heat and/or two esterification reaction heat to separate out methyl alcohol from the ejection of compact of maleic acid monoester and diester to reduce methyl alcohol separation energy consumption, reduce equipment load.

Additionally, the utility model provides an among the dimethyl maleate production system, the second inlet pipe communicates with the feed inlet of single esterification reactor, two esterification reactors and the feed inlet of rectifying column respectively, consequently, the utility model provides a dimethyl maleate production system divide into the triplex with methyl alcohol, provides single esterification reactor and carries out single esterification reaction, provides two esterification reactors and carries out one time two esterification reactions, provides the rectifying column and carries out two times two esterification reactions to reduce unnecessary methyl alcohol circulation, reduce equipment load.

Drawings

The accompanying drawings, which are described herein, serve to provide a further understanding of the invention and constitute a part of this specification, and the exemplary embodiments and descriptions thereof are provided for explaining the invention without unduly limiting it. In the drawings:

FIG. 1 shows a schematic structural diagram of a dimethyl maleate production system in an embodiment of the present invention;

FIG. 2 shows a schematic view of a rectifying column in an embodiment of the present invention;

fig. 3 shows a schematic flow chart of a dimethyl maleate production system process in the embodiment of the present invention.

Reference numerals:

100-a mono-esterification reactor; 200-a double esterification reactor; 300-a rectifying tower; 310-rectifying tower kettle; 311-left tower kettle; 312-right tower still; 320-a catalytic reaction section; 330-first stripping section; 340-a second stripping section; 400-a separation device; 500-a preheater; a-a first feed pipe; b-a second feed tube;

the logistics code number is as follows: 1-fresh methanol; 2-cis-maleic anhydride; discharging the 3-monomethyl maleate reactor; 4-fresh methanol; discharging from a 5-dimethyl maleate reactor; 6-discharging from a tower kettle at the left side of the rectifying tower; 7-compensation of methanol; 8-discharging from the top of the rectifying tower; 9-recycle of methanol; 10-discharging from a tower kettle at the right side of the rectifying tower; 11-refluxing methanol; 12-efflux of methanol; 13-waste water.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects to be solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically limited otherwise. The meaning of "a number" is one or more unless specifically limited otherwise.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Dimethyl maleate is an important organic chemical raw material, and can be prepared by mono-esterification reaction and di-esterification reaction of maleic anhydride and methanol. Since the mono-esterification reaction is irreversible, the di-esterification reaction is reversible equilibrium reaction, and the reaction of the di-esterification reaction proceeds slowly, the di-esterification reaction needs to be performed in the presence of a catalyst to accelerate the reaction. In order to increase the yield of dimethyl maleate, the water produced in the reaction is generally removed by catalytic distillation during the reaction, so as to shift the chemical equilibrium of the double esterification reaction.

The traditional production process adopts sulfuric acid as a catalyst, and although the production process has good catalyst activity and low price, a large amount of byproducts exist, the product is easy to isomerize to generate a large amount of dimethyl fumarate, and the product is difficult to purify and separate; and the reaction product of the sulfuric acid process needs to be subjected to alkali washing and water washing steps, so that the process is long and the corrosion problem of equipment is obvious.

Some researchers propose that the monoester is reacted with methanol in a fixed bed, and in order to ensure the conversion rate of the maleic anhydride, the methanol is excessive, and the methanol circulation energy consumption is high. The diester reaction adopts a reaction rectification mode, and the double esterification reaction is carried out in a rectification tower. In order to ensure complete conversion of the monomethyl maleate, excess methanol is required to participate in the double esterification reaction. On the basis, a large amount of methanol at the top of the rectifying tower and in the tower kettle needs to be recycled after separation and refining. In the process, the methanol needs to be continuously heated, vaporized, condensed and liquefied, the load of the rectifying tower is high, and the frequent liquefaction and vaporization of the methanol lead to high energy consumption, so that the utilization rate of the methanol is low.

The esterification reaction is carried out in the rectifying tower by independently depending on the resin catalyst, the catalyst in the rectifying tower needs to be frequently regenerated or loaded and unloaded due to reasons of raw material fluctuation, treatment load fluctuation and the like, the use cost of the catalyst is also increased, the heat of the single esterification reaction and the heat of the double esterification reaction are not fully and thoroughly utilized, the cis-maleic anhydride remained in the rectifying tower reacts with the resin catalyst for a long time, and the service life of the catalyst is shortened.

Based on above-mentioned problem, an urgent need for a reaction high efficiency, green, the little dimethyl maleate production system of methyl alcohol circulation volume, the utility model discloses the utility model provides a dimethyl maleate production system for low material consumption, low energy consumption and large-scale production dimethyl maleate, dimethyl maleate can directly be used for follow-up dimethyl maleate hydrogenation preparation dimethyl succinate or dimethyl maleate hydrogenation preparation 1,4-butanediol hydrogenation unit.

Fig. 1 illustrates a schematic structural diagram of a dimethyl maleate production system provided by the embodiment of the present invention. As shown in fig. 1, a dimethyl maleate production system provided by the embodiment of the present invention includes: a single esterification reactor, a double esterification reactor and a rectifying tower.

As shown in fig. 1, the above-mentioned mono-esterification reactor 100 is communicated with a first feeding pipe a for feeding maleic anhydride and a second feeding pipe b for feeding methanol, respectively. Based on this, the first feeding pipe a can be used for feeding maleic anhydride to the mono-esterification reactor 100, and the second feeding pipe b can be used for feeding methanol to the mono-esterification reactor 100, at this time, maleic anhydride and methanol enter the mono-esterification reactor 100 to perform mono-esterification reaction to obtain a monomethyl maleate discharge.

Illustratively, as shown in fig. 1, the first feed pipe a and the second feed pipe b can feed cis-maleic anhydride and methanol to the mono-esterification reactor 100 according to actual reaction molar ratios, so that cis-maleic anhydride and methanol undergo mono-esterification reaction in the mono-esterification reactor 100 at a certain temperature, and cis-maleic anhydride is almost completely converted into monomethyl maleate. For example: when the molar ratio of the cis-maleic anhydride to the methanol in the mono-esterification reactor 100 is (1-3): 1, the reaction temperature can be 30-150 ℃. In addition, since the methanol is excessive, the discharged monomethyl maleate contains not only monomethyl maleate but also unreacted methanol.

As shown in FIG. 1, the discharge port of the above-mentioned mono-esterification reactor 100 is communicated with the feed port of the double-esterification reactor 200. At this time, the discharged monomethyl maleate may enter the double esterification reactor 200 for double esterification reaction to obtain a discharged dimethyl maleate, and 30-60% of the monomethyl maleate may be converted into dimethyl maleate during the double esterification reaction. Meanwhile, as the feed inlet of the double esterification reactor 200 is also used for being communicated with the second feed pipe b, the second feed pipe b can not only convey methanol to the single esterification reactor 100, but also convey methanol to the double esterification reactor 200, so that the monomethyl maleate is converted into dimethyl maleate as much as possible. Furthermore, since the second feeding pipe b feeds methanol to the double esterification reactor 200, unnecessary methanol circulation can be reduced, thereby reducing circulation energy consumption and equipment energy consumption, for example: the vaporized methanol and the condensed liquefied methanol are not required to be continuously heated.

The reaction conditions of the double esterification reaction are as follows: the molar ratio of the monomethyl maleate to the methanol is (1-4): 1, the reaction temperature is 50-160 ℃, and the pressure is 0.2-1 Mpa. At this time, the dimethyl maleate discharge contains not only unreacted monomethyl maleate but also unreacted excess methanol.

As depicted in FIG. 1, the above-described mono-esterification reactor 100 and/or di-esterification reactor 200 can be of the adiabatic reactor type. When the mono-esterification reactor 100 is an adiabatic reactor, mono-esterification reaction can be performed in the mono-esterification reactor 100, and a large amount of reaction heat is released during the mono-esterification reaction to accelerate the conversion of maleic anhydride into maleic acid monoester. When the double esterification reactor 200 is an adiabatic reactor, a double esterification reaction can be performed in the double esterification reactor 200, and a large amount of reaction heat released during the double esterification reaction can accelerate the conversion of monomethyl maleate to dimethyl maleate. When the mono-esterification reactor 100 and the di-esterification reactor 200 are adiabatic reactors, the reaction heat released during the mono-esterification reaction and the reaction heat released during the di-esterification reaction not only accelerate the conversion rate of maleic anhydride and monomethyl maleate, but also allow abundant reaction heat to enter the left tower kettle of the rectifying tower in the dimethyl maleate discharge to complete the recovery of methanol.

As shown in fig. 1, the rectifying tower 300 includes a tower bottom 310 and a catalytic reaction section 320 located above the tower bottom 310, a discharge port of the double esterification reactor 200 is communicated with an inlet of the tower bottom 310 of the rectifying tower 300, an outlet of the tower bottom 310 of the rectifying tower 300 is communicated with a feed port of the rectifying tower 300, and the feed port of the rectifying tower 300 is further used for being communicated with a second feed pipe b.

For example, as shown in fig. 1, when the discharge port of the double esterification reactor 200 is communicated with the inlet of the bottom 310 of the rectification column 300, the discharged dimethyl maleate in the double esterification reactor 200 enters the bottom 310 of the rectification column 300, the unreacted methanol is vaporized by using the rich reaction heat contained in the discharged dimethyl maleate, and the vaporized methanol directly enters the catalytic reaction section 320 from the inside of the rectification column 300 and directly enters the catalytic reaction section 320 as a raw material to continue the reaction. In the process of methanol vaporization, not only extra heat is not consumed, but also the methanol circulation amount can be reduced, and the energy consumption is reduced. Meanwhile, the feed inlet of the rectifying tower 300 is also used for being communicated with the second feed pipe b, so that the second feed pipe b can convey fresh methanol to the catalytic reaction section 320 of the rectifying tower 300, and the supplemented fresh methanol is injected from the lower part of the rectifying tower, so that the monomethyl maleate and the methanol perform a countercurrent reaction, and dimethyl maleate and a byproduct water are generated in the reaction process. On the basis, the outlet of the tower bottom 310 of the rectifying tower 300 is communicated with the feed inlet of the rectifying tower 300, and the dimethyl maleate discharged after the methanol separation can be sent to the catalytic reaction section 320 in a manner of discharging from the tower bottom 310. At the moment, the unreacted monomethyl maleate contained in the discharged dimethyl maleate can be subjected to secondary double esterification with methanol.

Additionally, the embodiment of the utility model provides a dimethyl maleate production system divide into the triplex with methyl alcohol, provides single esterification reactor and carries out single esterification reaction, provides double esterification reactor and carries out a double esterification reaction, provides rectifying column 300 and carries out the double esterification reaction to reduce unnecessary methyl alcohol circulation, reduce equipment load.

Illustratively, as shown in fig. 1, when the single esterification reactor 100 of the embodiment of the present invention is a tubular fixed bed reactor and the double esterification reactor 200 is a fixed bed double esterification reactor 200, the first feeding pipe a and the second feeding pipe b can convey maleic anhydride and methanol to the single esterification reactor 100 according to an actual reaction molar ratio, so that the maleic anhydride and the methanol perform a single esterification reaction in the single esterification reactor 100 at a certain temperature, and the monomethyl maleate discharge can be obtained without a catalyst. At this time, the monomethyl maleate in the mono-esterification reactor 100 is discharged into the di-esterification reactor 200, about 30-60% of the monomethyl maleate in the di-esterification reactor 200 can be converted into dimethyl maleate, and the remaining unconverted monomethyl maleate is discharged into the bottom 310 of the rectifying tower 300.

As shown in fig. 1, in the embodiment of the present invention, the double esterification reactor 200 can convert about 30% to 60% of monomethyl maleate into dimethyl maleate, the remaining unreacted monomethyl maleate enters the catalytic reaction section 320 of the rectification column 300, and since part of the methanol in the catalytic reaction section 320 is derived from unreacted methanol in the dimethyl maleate discharge, the molar ratio of the methanol reacted in the catalytic reaction section 320 to the monomethyl maleate is actually (3-4): 1, the actual ratio of methanol to maleic anhydride in the mono-esterification reactor 100 is (1-1.2): 1, nearly complete conversion of cis-maleic anhydride to monomethyl maleate, in a double esterification reactor 200 the methanol and monomethyl maleate are substantially in the ratio of 1:1, so that the molar ratio of methanol to cis-maleic anhydride is in the range of (2 to 3): 1, and the molar ratio of the existing methanol to the cis-maleic anhydride is more than 3:1, therefore, the utility model can reduce the circulating dosage of the methanol.

Illustratively, the rectifying tower bottom 310 may be a dividing wall type bottom 310, and the dividing wall in the dividing wall type bottom 310 divides the internal space of the dividing wall type bottom 310 into two subspaces, wherein one subspace is used for recovering methanol in the reaction product in the double esterification reactor 200, and the other subspace is used for recovering the reaction product in the catalytic section in the rectifying tower 300, so as to facilitate the subsequent hydrogenation of dimethyl maleate to prepare dimethyl succinate or hydrogenation of dimethyl maleate to prepare 1,4-butanediol.

For example, one subspace is defined as a left-side tower bottom 311, the other subspace is defined as a right-side tower bottom 312, the dimethyl maleate discharged from the double esterification reactor is directly sent to the left-side tower bottom 311 of the rectification tower, excessive methanol in the dimethyl maleate discharged from the double esterification reactor is recovered in the left-side tower bottom 311 of the rectification tower and then directly enters the catalytic reaction section of the rectification tower 300 in a gas phase form to participate in the next reaction, and then the monomethyl maleate and the diester in the left-side tower bottom 311 of the rectification tower are sent to the upper part of the reaction section of the rectification tower 300 to continue to participate in the reaction.

Illustratively, as shown in fig. 2, the feed ports of the rectifying tower 300 include a first feed port and a second feed port distributed along the direction of increasing the height of the rectifying tower 300, the first feed port is used for communicating with a second feed pipe b, and the second feed port is communicated with the outlet of the rectifying tower 300 at the bottom 310. Along the direction of increasing height of the rectifying tower 300, the first feed inlet is located at one end of the catalytic reaction section 320 close to the tower bottom 310, and the second feed inlet is located at one end of the catalytic reaction section 320 away from the tower bottom 310.

In practical application, as shown in fig. 2, along the increasing direction of the height of the rectifying tower 300, the first feeding port is located at one end of the catalytic reaction section 320 close to the tower bottom 310, and the second feeding port is located at one end of the catalytic reaction section 320 away from the tower bottom 310, so that the methanol supplemented by the second feeding pipe b can be injected into the rectifying tower 300 from the lower part of the catalytic reaction section 320, and the tower bottom discharge from the discharge port of the tower bottom 310 is injected into the rectifying tower 300 from the upper part of the catalytic reaction section, so that the monomethyl maleate contained in the tower bottom 310 discharge performs a counter-current reaction with the methanol to generate the dimethyl maleate and water. The slightly excessive methanol and the water generated by the reaction can be extracted from the top of the rectifying tower 300, the generated dimethyl maleate can be extracted from the other subspace of the tower bottom 310, and the extracted dimethyl maleate discharge can be directly used for preparing dimethyl succinate by subsequent dimethyl maleate hydrogenation or a hydrogenation unit for preparing 1,4-butanediol by dimethyl maleate hydrogenation. Tests prove that the conversion rates of maleic anhydride and monomethyl maleate contained in the discharged material of the tower bottom 310 in the catalytic reaction section 320 are both more than 99.5%, and the acid value of the dimethyl maleate product generated by the reaction is lower and is less than 0.5mgKOH/g.

In one example, as shown in fig. 2, the rectifying tower 300 of the embodiment of the present invention further includes a first stripping section 330, and the first stripping section 330 is located between the catalytic reaction section 320 and the tower bottom 310. At this time, the methanol vaporized from one subspace may be further purified by the first stripping section 330 to reach the bottom of the catalytic reaction section 320. Meanwhile, the dimethyl maleate generated in the catalytic reaction section 320 can also be purified by the first stripping section 330 and then enter another space. It should be understood that a liquid purification column can be further disposed between the subspace of the column bottom 310 for vaporizing methanol and the first stripping section 330, so that the vaporized methanol can be purified in advance by the liquid purification column before entering the first stripping section 330, and therefore, the methanol can be purified twice by the liquid purification column and the first stripping section 330 before reaching the bottom of the catalytic reaction section 320, and the introduction of impurities into the reaction can be reduced.

In one example, as shown in fig. 2, the rectifying column 300 of the embodiment of the present invention further includes a second stripping section 340, and the second stripping section 340 is located at an end of the catalytic reaction section 320 that faces away from the first stripping section 330. When a little excessive methanol and water generated by the reaction are carried, the methanol can enter the top of the rectifying tower after being purified by the second stripping section 340, so that the energy consumption of the subsequent purification is reduced.

In one example, the catalytic reaction section 320 may be in the form of a fixed bed, wherein the catalyst is a solid acid and acidic resin catalyst, and the catalyst is alternately filled in order to increase the discharge rate of dimethyl maleate. Compared with the traditional sulfuric acid catalyst, the resin catalyst filled in the catalytic reaction section 320 has less side reaction in the reaction process of the resin catalyst, the acid proportion in the product is small, the product quality can be improved, the product separation step is reduced, the corrosion to equipment can be reduced, and the dimethyl maleate obtained after esterification can be discharged to a downstream butanediol and dimethyl succinate generation device directly.

Here, it is understood that the above-mentioned height of the packed catalyst is 1/3 of the distance from the bottom of the catalytic reaction section 320 to the bottom of the column bottom 310 of the rectifying column 300, and the distance from the top of the catalytic reaction section 320 to the bottom of the column bottom 310 is 2/3 of the distance from the column bottom 310. The theoretical plate number of the rectifying tower 300 is 20-40, the reaction temperature is 60-150 ℃, and when the molar ratio of methanol contained in the material flow 5, the material flow 9 and the material flow 10 to the monomethyl maleate in the material flow 6 is (1-4): 1, the volume space velocity of the monomethyl maleate to the 300 catalyst of the rectifying tower is 0.1h ^-1 ～4h ^-1 、0.2h ^-1 ～3h ^-1 Or 0.3h ^-1 ～2h ^-1 。

Illustratively, when the esterification reaction is performed in the catalytic reaction section 320, the catalyst needs to be replaced by continuously stopping the operation, and frequent replacement of the catalyst not only causes fluctuation of raw materials and fluctuation of treatment load but also increases the catalyst use cost of the catalyst. For guaranteeing that the catalytic activity of catalyst is stable, on this basis, the utility model discloses in the dimethyl maleate production system of embodiment, two esterification reactors 200 carry out one time two esterification reactors 200 as the prereactor, and rectifying column 300 carries out two times two esterification reactors 200 as formal reactor to reduce the change number of times of catalyst in rectifying column 300, and then reduce catalyst use cost. Meanwhile, the number of the double esterification reactors 200 may be one or at least two. When the number of the double esterification reactors 200 is at least two, at least one of the double esterification reactors 200 is in an operating state, and at least one of the double esterification reactors 200 is in a closed state.

For example, when the catalyst needs to be replaced, the double esterification reactor 200 in which the catalyst is located can be set to a shutdown state, and the double esterification reactor 200 in which the catalyst does not need to be replaced is set to a startup state, so that the dimethyl maleate production system can continuously perform double esterification, and the problem of fluctuation of raw materials and processing load in the rectifying tower 300 caused by frequent replacement of the catalyst is reduced.

Illustratively, the dimethyl maleate production system provided by the embodiment of the present invention further includes a preheater 500, which is disposed on the first feeding pipe b. At this time, the pre-heater 500 can be used to pre-heat the methanol input from the second feeding pipe in advance, and the methanol entering the mono-esterification reactor 100, the bi-esterification reactor 200 and the rectifying tower 300 can participate in the reaction quickly, so that the production efficiency can be improved.

The above dimethyl maleate production system further comprises: the discharge hole of the separation device 400 and the discharge hole of the rectifying tower 300 are communicated with the feed hole of the separation device 400, the discharge hole of the separation device 400 is communicated with the third feed hole of the rectifying tower and/or the fourth feed hole of the rectifying tower respectively, the third feed hole is positioned at one end of the catalytic reaction section close to the tower kettle, the fourth feed hole is positioned above one end of the catalytic reaction section far away from the tower kettle, and the separation device 400 can be a membrane separation component.

Exemplarily, adopt rectification coupling membrane separation technique in the rectifying column, adopt the rectification coupling to accomplish dimethyl maleate rectification in the rectifying column, compare with traditional production process, the utility model discloses a realize esterification reaction and separation in same rectifying column. When the discharge hole of the rectifying tower 300 is communicated with the feed inlet of the separation device 400, the methanol carrying water enters the separation device 400 through separation in a steam mode without condensation, and the separation device 400 directly removes byproduct water through a membrane separation technology, so that the separation of the methanol and the water is realized. Based on this, compare through the mode of multistage rectification with the tradition, the utility model discloses methanol need not through the process of sending out gaseous phase condensation, the separation of liquid phase heating vaporization that relapse, greatly reduced equipment investment and separation energy consumption.

Illustratively, since the third feed port is located at one end of the catalytic reaction section close to the bottom of the column, when the discharge port of the separation device 400 is communicated with the third feed port of the rectifying column, the methanol separated by the separation device enters the catalytic reaction as the circulating methanol to continue to participate in the reaction. Based on the method, the methanol circulation amount can be greatly reduced, and the production cost is reduced. The fourth feed inlet is positioned above one end of the catalytic reaction section, which is far away from the tower kettle, and when the discharge hole of the separation device 400 is communicated with the fourth feed inlet of the rectifying tower, the methanol separated by the separation device enters the rectifying tower through the fourth feed inlet as reflux methanol so as to prevent a small amount of monomethyl maleate or dimethyl maleate from entering the tower top. When the discharge hole of the separation device 400 is simultaneously communicated with the third feed inlet and the fourth feed inlet, the methanol separated by the separation device enters the rectifying tower respectively as circulating methanol and reflux methanol, so that the methanol circulating energy consumption can be reduced in the whole process of producing the dimethyl maleate.

Illustratively, the membrane separation module comprises a plurality of membrane modules, and the membrane modules can be connected in series, parallel or series-parallel. The utility model discloses in because moisture content is more, adopt the tandem system to connect the membrane module, can realize the separation of methyl alcohol and water fast. It should be understood that different membrane separation module connection modes can be adopted according to the water content and the load, and according to actual conditions. The membrane module may be a pervaporation membrane module, such as a molecular sieve type membrane, for rapid separation of methanol and water, although other membrane modules may be selected, and are not illustrated here.

In an embodiment, the utility model discloses a adiabatic fixed bed single esterification reactor and adiabatic fixed bed double esterification reactor, after the esterification reaction is accomplished in double esterification reactor, the dimethyl maleate ejection of compact in the double esterification reactor enters rectifying column left side tower cauldron, utilize single esterification reaction heat and double esterification reaction heat to accomplish the recovery of excessive methyl alcohol, surplus dimethyl maleate ejection of compact after retrieving the methyl alcohol enters into the rectifying column and continues to participate in the reaction, carry out the secondary esterification reaction in the rectifying column, after the reaction finishes with the mode separation dimethyl maleate of rectification coupling, back through the direct ejection of compact of rectifying column right side tower cauldron, excessive methyl alcohol carries moisture with the form of gaseous phase and enters into the rectifying column top after the reaction, realize the separation of methyl alcohol and water through separator when extracting from the rectifying column top of the tower, the methyl alcohol of separation divide into the triplex, one part is as backward flow methyl alcohol, one part is as circulation methyl alcohol, one part is as outer row of methyl alcohol, the water of formation discharges the production technology of outside.

Compare with traditional production dimethyl maleate production process, the utility model discloses in the water that generates in the esterification reaction need not the condensation at the rectifying column top, directly get into membrane separation subassembly with the steam mode, through the direct desorption by-product water of membrane separation, but methyl alcohol circulation continues the reaction to the rectifying section, compares through the mode of multistage rectification with the tradition, and methyl alcohol need not through the gas phase condensation that relapse, the process of liquid phase heating vaporization separation, the cost and the separation energy consumption of reduction equipment. The mol ratio of methanol to maleic anhydride in one-way reaction in the production process of the dimethyl maleate can be reduced to 3, the methanol circulation amount is greatly reduced, and the production cost is greatly reduced. Therefore, the conversion rate of cis-maleic anhydride in the whole esterification reaction process reaches 100%, the selectivity of dimethyl maleate reaches more than 99.5%, and the circulating dosage of methanol is greatly reduced.

Illustratively, during the esterification reaction in the rectifying tower 300, solid acid and strong acidic ions can be used to perform the esterification reaction with the resin catalyst, which can effectively reduce the problem of corrosion of equipment and also reduce the production cost.

In an embodiment, the utility model provides a logistics reaction process, methyl alcohol commodity circulation 1 and cis-maleic anhydride commodity circulation 2 generate maleic acid monomethyl ester commodity circulation 3 in simple esterification reactor 100, methyl alcohol commodity circulation 4 gets into in the double esterification reactor 200 after 3 mixes with maleic acid monomethyl ester commodity circulation, when the double esterification reactor carries out the catalyst change, generate and contain maleic acid monomethyl ester, the material 5 of dimethyl maleate and excessive methyl alcohol, send to rectifying column 300, tower cauldron ejection of compact commodity circulation 6 only contains maleic acid monomethyl ester, the material 6 of dimethyl maleate is sent to the upper portion of rectifying column catalyst section, compensation methyl alcohol 7, backflow methyl alcohol commodity circulation 11 and circulation methyl alcohol commodity circulation 9 contact reaction with maleic acid monomethyl ester in the rectifying column against the current, rectifying column right side tower cauldron ejection of compact commodity circulation 10 takes out the dimethyl maleate product. The steam rich in water and methanol at the top of the rectifying tower directly enters a separation device, the stream 13 at the permeation side discharges waste water, and the stream 9 at the retentate side circulates the methanol, the stream 11 at the reflux methanol and the stream 12 at the discharge methanol.

In one implementation, the reaction conditions in the mono-esterification reactor 100 are: the molar ratio of methanol in the material flow 1 to maleic anhydride in the material flow 2 is 1.3:1, reaction pressure is 1Mpa, feeding temperature is 50 ℃, retention time is 10min, nearly 90 percent of cis-maleic anhydride is converted into monomethyl maleate.

The reaction conditions of the double esterification reactor 200 are as follows: the feeding temperature is 90 ℃, the retention time is 60min, and the molar ratio of the methanol to the total maleic anhydride of the feeding system of the rectifying tower is 3:1, completely converting maleic anhydride into monomethyl maleate, and converting maleic monoester into dimethyl maleate at a conversion rate of 40%;

the reaction conditions of the rectifying tower 300 are as follows: the temperature of the left tower kettle and the right tower kettle of the rectifying tower are both 130-150 ℃, the pressure is 0.3Mpa, the mass of the reflux methanol of the material flow 11 is 0.15 times of the mass of the material flow 6, and the total molar ratio of the methanol to the monomethyl maleate in the catalytic reaction section is 3:1, the retentate side water content is less than 1% after passing through the separation unit and the permeate side stream 13 is free of methanol. After the reaction, the conversion rate of the maleic acid monomethyl ester is 99.5 percent, the selectivity of the maleic acid dimethyl ester is 99.5 percent, the acid value of the material flow 9 is lower than 0.5mgKOH/g, and the material flow can directly enter a downstream hydrogenation reactor.

Above-mentioned dimethyl maleate production system, the conversion of cis-maleic anhydride can be accelerated to the make full use of single esterification reaction heat and the double esterification reaction heat in reaction process for production is more high-efficient, and make full use of reaction heat in whole production process simultaneously leads to retrieving excessive methyl alcohol and reusing, makes whole dimethyl maleate production process more green.

In one embodiment, a process flow of a dimethyl maleate production system is also provided, as shown in fig. 3:

step 1: conveying a fresh methanol material flow 1 and a cis-maleic anhydride material flow 2 to a single esterification tubular fixed bed reactor through a first feeding pipe a and a second feeding pipe b, wherein when the molar ratio of cis-maleic anhydride to methanol is (1-3): 1, the reaction temperature is 30-150 ℃;

step 2: taking the discharged monomethyl maleate in the single esterification reactor as a material flow 3, continuously mixing the discharged monomethyl maleate with a fresh methanol material flow 4, and then entering a double esterification reactor, wherein when the molar ratio of the monomethyl maleate to the methanol is (1-4): 1, the reaction temperature is 50-160 ℃, the pressure is 0.2-1 Mpa, and the obtained maleic acid mono-diester is discharged as a material flow 5;

and step 3: maleic acid dimethyl ester in a double esterification reactorAnd (3) sending a material flow 5 in the ester discharge to a tower kettle on the left side of the rectifying tower, recovering excessive methanol by rich reaction heat contained in the dimethyl maleate discharge in the double esterification reactor, connecting a discharge hole of the tower kettle on the left side of the rectifying tower with a feed inlet of the rectifying tower, and sending a discharge material flow 6 of the tower kettle on the left side of the rectifying tower to the rectifying tower for continuous reaction. Methanol recovered from the left tower bottom of the rectifying tower directly enters a catalytic reaction section to continuously participate in reaction after being purified by a first stripping section, and simultaneously, dimethyl maleate discharge material flow 5, discharge material flow 6 of the left tower bottom of the rectifying tower and reflux methanol material flow 11 are in countercurrent contact to generate esterification reaction in the catalytic reaction section, so that monomethyl maleate is completely converted into dimethyl maleate and is discharged as material flow 10 through a right tower bottom, and the discharge dimethyl maleate from the right tower bottom can be directly used for preparing dimethyl succinate through subsequent dimethyl maleate hydrogenation or a hydrogenation unit for preparing 1,4-butanediol through dimethyl maleate hydrogenation. Wherein, the reaction section of the rectifying tower is filled with solid acid or acid resin catalyst, the catalyst and the filler are alternately filled, the height of the catalyst filling is 1/3 of the distance from the bottom of the catalytic reaction section to the bottom of the tower kettle, the distance from the top of the catalytic reaction section to the bottom of the tower kettle is 2/3 of the distance from the tower kettle, the theoretical plate number of the rectifying tower is 20-40, the reaction temperature is 60-150 ℃, and when the molar ratio of methanol contained in the material flow 5, the material flow 9 and the material flow 10 to the monomethyl maleate of the material flow 6 is (1-4): 1, the volume space velocity of the monomethyl maleate to the 300 catalyst of the rectifying tower is 0.1h ^-1 ～4h ^-1 、0.2h ^-1 ～3h ^-1 Or 0.3h ^-1 ～2h ^-1 ；

And 4, step 4: the water generated in the esterification reaction of the catalytic section of the rectifying tower is carried to the top of the rectifying tower by a little excessive methanol, the top of the rectifying tower contains vaporized methanol and water vapor which directly enter a separating device, the methanol carrying the water enters the separating device as a material flow 8 to be separated, the wastewater separated after being cooled by a condenser of the separating device is discharged out of the system by a material flow 13, the separated circulating methanol is divided into three strands, a reflux methanol material flow 11 is used for returning to the rectifying tower to carry water and preventing dimethyl maleate from entering the top of the rectifying tower, a circulating methanol material flow 9 is directly sent to the catalytic reaction section for circulating reaction, and an externally discharged methanol material flow 12 prevents light component impurities from accumulating. When the pervaporation membrane is used for separation, organic components such as water, methanol and the like in the discharged methanol material flow 12 permeate to the downstream side of the membrane from the upstream side of the membrane through the membrane component in a gas phase mode, the pressure of the rectifying tower is 0.1-0.5 MPa and 0.2-0.4 MPa to ensure the osmotic pressure difference, or the downstream side of the membrane adopts a vacuumizing and condensing mode to form the partial pressure difference of the components on the upstream side and the downstream side of the membrane, and the pressure is 0.1-0.3 MPa in vacuum. Permeate vapor is drawn by a vacuum pump into a permeate condenser where it is condensed and discharged as wastewater as stream 13.

The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (9)

1. A dimethyl maleate production system, comprising:

the single esterification reactor is used for respectively communicating a first feeding pipe and a second feeding pipe, wherein the first feeding pipe is used for conveying maleic anhydride, and the second feeding pipe is used for conveying methanol;

the single esterification reactor and/or the double esterification reactor are/is an adiabatic reactor, a discharge hole of the single esterification reactor is communicated with a feed hole of the double esterification reactor, and the feed hole of the double esterification reactor is also used for being communicated with the second feed pipe;

and the rectifying column comprises a column kettle and a catalytic reaction section positioned above the column kettle, the discharge port of the double-esterification reactor is communicated with the column kettle inlet of the rectifying column, the column kettle outlet of the rectifying column is communicated with the feed inlet of the rectifying column, and the feed inlet of the rectifying column is also communicated with the second feed pipe.

2. The dimethyl maleate production system of claim 1 wherein the mono-esterification reactor and the di-esterification reactor are fixed bed adiabatic reactors.

3. The dimethyl maleate production system of claim 1 wherein the column bottom is a dividing wall column bottom, the dividing wall in the dividing wall column bottom divides the internal space of the dividing wall column bottom into two subspaces, the inlet of the column bottom is communicated with one subspace, and the outlet of the one subspace is communicated with the inlet of the rectification column.

4. The dimethyl maleate production system of claim 1, wherein the feed inlet of the rectification column comprises a first feed inlet and a second feed inlet distributed along the direction of increasing height of the rectification column, the first feed inlet is used for communicating with the second feed pipe, and the second feed inlet is communicated with the kettle outlet of the rectification column.

5. The dimethyl maleate production system of claim 4 wherein, along the direction of increasing height of the rectification column, the first feed inlet is located at the end of the catalytic reaction section near the bottom of the column, and the second feed inlet is located at the end of the catalytic reaction section away from the bottom of the column.

6. The dimethyl maleate production system of claim 4 wherein the rectification column further comprises a first stripping section and a second stripping section, the first stripping section is located between the catalytic reaction section and the bottom of the column, and the second stripping section is located at an end of the catalytic reaction section away from the first stripping section.

7. The dimethyl maleate production system of any of claims 1 to 6 further comprising a preheater for being provided on the second feed pipe.

8. The dimethyl maleate production system of any one of claims 1 to 6 further comprising: the separation device, the discharge gate of rectifying column with separation device's feed inlet intercommunication, separation device's discharge gate respectively with the third feed inlet of rectifying column and/or the fourth feed inlet intercommunication of rectifying column, the third feed inlet is located the catalytic reaction section is close to the one end of tower cauldron, the fourth feed inlet is located the catalytic reaction section deviates from the top of the one end of tower cauldron.

9. The dimethyl maleate production system of claim 8 wherein the separation device is a membrane separation module.

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