KR102417077B1 - Process for producing methyl methacrylate - Google Patents

Abstract

The present invention relates to a process for the preparation of methyl methacrylate. According to the present invention, there is provided a method for producing methyl methacrylate, which enables the improvement of catalyst life and an increase in production of methyl methacrylate while ensuring the safety of the process.

Description

Method for producing methyl methacrylate {PROCESS FOR PRODUCING METHYL METHACRYLATE}

The present invention relates to a process for the preparation of methyl methacrylate.

Methyl methacrylate (MMA), a colorless and transparent liquid, has excellent reactivity and easily causes various chemical reactions such as polymerization and esterification by light, heat, and radiation. Polymethyl methacrylate (PMMA), a polymer of methyl methacrylate, is used in various industries such as construction, electronics, automobiles, aviation, medicine, extraction, and paints, and its uses are increasing.

As a general method for producing methyl methacrylate, a method using the process shown in FIG. 1 is exemplified.

The above method is a first oxidation of obtaining a first product (P1) containing methacrolein by subjecting a raw material compound (1), which is a C4 compound such as isobutylene and tertiary-butyl alcohol, to a gas phase catalytic oxidation reaction in the presence of a catalyst. process; a second oxidation step of subjecting the first product (P1) to a gas phase catalytic oxidation reaction in the presence of a catalyst to obtain a second product (P2) containing methacrylic acid and unreacted methacrolein; and an esterification process of obtaining a third product (P3) containing methyl methacrylate by esterifying the methacrylic acid separated from the second product (P2) with methanol. Here, unreacted methacrolein included in the second product P2 is recovered through the purification system 300 and supplied as a raw material compound for the second oxidation process together with the first product P1.

However, when the unreacted methacrolein included in the second product P2 is recycled as a raw material compound for the second oxidation process, there is a problem in that the life of the catalyst used in the second oxidation process is rapidly reduced. In addition, the flow rate in the second oxidation reactor 200 increases due to the recirculation of the unreacted methacrolein, thereby increasing the risk of explosion during operation of the process.

In order to solve these problems, it is necessary to reduce the amount of unreacted methacrolein contained in the second product P2, that is, it is necessary to maintain and manage a conversion rate of a certain level or more in the second oxidation reactor 200. In order to maintain the conversion rate above a certain level in the second oxidation reactor 200, compensation of the process temperature and maintenance of catalyst activity are required. Therefore, the selectivity of methacrylic acid in the second oxidation reactor 200 is reduced, and there is a limit in that it is difficult to improve the yield in the entire process.

Meanwhile, as another method for preparing methyl methacrylate, a method for preparing methyl methacrylate by oxidative esterification of methacrolein with methanol and a gas containing molecular oxygen has been proposed.

However, in the above method, a large amount of energy is consumed in the recycling of excess methanol. To solve the above problem, if the amount of recycled excess methanol is reduced, the yield of methyl methacrylate is lowered and a large amount of by-products (such as carbon dioxide, methyl formate, undesired carboxylate esters, etc.) are formed. . Therefore, a complicated purification process for separating methyl methacrylate from the final product is required. And, since methyl methacrylate is very unstable, it causes a decrease in the activity of the catalyst due to a polymerization reaction product of methyl methacrylate, and continuous operation for a long period of time may be difficult.

An object of the present invention is to provide a method for producing methyl methacrylate, which enables an improvement in catalyst life and an increase in methyl methacrylate production while ensuring process safety.

According to the present invention,

(a) a first oxidation process for obtaining a first product containing methacrolein (MACR) by subjecting isobutylene, tert-butyl alcohol or a mixture thereof to a gas phase catalytic oxidation reaction with a gas containing molecular oxygen in the presence of a catalyst ,

(b) a second product containing methacrylic acid (MAA) and unreacted methacrolein (MACR) by subjecting the first product obtained in step (a) to a gas phase catalytic oxidation reaction with a gas containing molecular oxygen in the presence of a catalyst a second oxidation process to obtain

(c) a purification process of separating methacrylic acid (MAA) and unreacted methacrolein (MACR) from the second product obtained in step (b);

(d) an esterification step of esterifying the methacrylic acid (MAA) obtained in the step (c) with methanol to obtain a third product containing methyl methacrylate (MMA), and

(e) a fourth product containing methyl methacrylate (MMA) by oxidative esterification reaction of unreacted methacrolein (MACR) obtained in step (c) with methanol and a gas containing molecular oxygen Oxidative esterification process to obtain

A method for producing methyl methacrylate is provided, comprising a.

Hereinafter, a method for producing methyl methacrylate according to an embodiment of the present invention will be described in more detail.

*Terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. And, as used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite.

As used herein, the meaning of 'comprising' or 'containing' specifies a particular characteristic, region, integer, step, operation, element, or component, and of another particular characteristic, region, integer, step, operation, element, or component. It does not exclude additions.

In this specification, terms including ordinal numbers such as 'first' and 'second' are used for the purpose of distinguishing one component from other components, and do not intend to limit the components by the ordinal number.

The present invention relates to a method for preparing methyl methacrylate from a raw material compound including isobutylene, tert-butyl alcohol, or a mixture thereof.

As shown in FIG. 1, in a general process for producing methyl methacrylate, unreacted methacrolein contained in the second product (P2) is recovered through the purification system 300, and this is combined with the first product (P1) and Together, it is supplied as a raw material compound for the second oxidation process.

However, due to the recirculation of unreacted methacrolein, the lifespan of the catalyst used in the second oxidation process is rapidly reduced, and the flow rate in the second oxidation reactor 200 is increased, thereby increasing the risk of explosion during operation of the process. do.

In order to solve this problem, it is necessary to reduce the amount of unreacted methacrolein included in the second product P2 by maintaining a conversion rate above a certain level in the second oxidation reactor 200 . However, measures for maintaining and managing the conversion rate (for example, compensation of process temperature and maintenance of catalytic activity) cause a decrease in methacrylic acid selectivity in the second oxidation reactor 200 and a decrease in yield in the entire process do.

As a result of the inventors' research, as shown in FIG. 2, unreacted methacrolein recovered through the purification system 300 after the first and second oxidation processes was subjected to an oxidative esterification reaction in a separate reactor, as shown in FIG. It was confirmed that the problems of the same process can be solved.

Referring to FIG. 2 , unreacted methacrolein recovered through the purification system 300 in the method for producing methyl methacrylate according to the present invention is not recycled as a raw material compound in the second oxidation process. Accordingly, the risk of explosion due to an increase in the flow rate in the second oxidation reactor 200 can be reduced, and the lifespan of the catalyst used in the second oxidation process can be dramatically improved. Furthermore, since there is no need to maintain and manage a high conversion rate at the level required in the process shown in FIG. 1 in the second oxidation reactor 200, the amount of the raw material compound 1 supplied to the first oxidation reactor 100 is reduced. It can be increased enough to increase production. In addition, the unreacted methacrolein is subjected to an oxidative esterification reaction in the presence of a palladium-bismuth-containing catalyst in a separate reactor to obtain additional methyl methacrylate, thereby increasing the overall production of methyl methacrylate.

According to one embodiment of the invention,

(a) a first oxidation process for obtaining a first product containing methacrolein (MACR) by subjecting isobutylene, tert-butyl alcohol or a mixture thereof to a gas phase catalytic oxidation reaction with a gas containing molecular oxygen in the presence of a catalyst ,

(b) a second product containing methacrylic acid (MAA) and unreacted methacrolein (MACR) by subjecting the first product obtained in step (a) to a gas phase catalytic oxidation reaction with a gas containing molecular oxygen in the presence of a catalyst a second oxidation process to obtain

(c) a purification process of separating methacrylic acid (MAA) and unreacted methacrolein (MACR) from the second product obtained in step (b);

(d) an esterification step of esterifying the methacrylic acid (MAA) obtained in the step (c) with methanol to obtain a third product containing methyl methacrylate (MMA), and

(e) a fourth product containing methyl methacrylate (MMA) by oxidative esterification reaction of unreacted methacrolein (MACR) obtained in step (c) with methanol and a gas containing molecular oxygen Oxidative esterification process to obtain

A method for producing methyl methacrylate is provided, comprising a.

The method for preparing methyl methacrylate may be performed according to the process of FIG. 2 .

(a) first oxidation process

The first oxidation step is a step for obtaining a first product (P1) containing methacrolein (MACR) by subjecting the raw material compound (1) to a gas phase catalytic oxidation reaction with a molecular oxygen-containing gas in the presence of a catalyst.

As the raw material compound (1), a C4 compound including isobutylene, tert-butyl alcohol, or a mixture thereof may be used.

The first oxidation process may be performed in the first oxidation reactor 100 filled with a catalyst.

As the first oxidation reactor 100 , a reactor having a conventional configuration known to be usable for performing a gas phase catalytic oxidation reaction may be used.

As the catalyst in the first oxidation process, a composite metal oxide represented by the following Chemical Formula 1 may be used:

[Formula 1]

Mo _a Bi _b Fe _c Co _d X _e Y _f O _h

In Formula 1,

Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, O is oxygen,

X is at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), and titanium (Ti),

Y is nickel (Ni), tin (Sn), zinc (Zn), tungsten (W), chromium (Cr), manganese (Mn), magnesium (Mg), antimony (Sb), cerium (Ce), and titanium ( Ti) is at least one element selected from the group consisting of,

a, b, c, d, e, f, and h are the atomic ratios of each element,

When a=12, b is 0.1 to 10, c is 0.1 to 10, d is 1 to 10, e is 0.01 to 2, f is 0 to 3, and h is a number determined by the oxidation state of each element.

There is no particular limitation on the raw material compound used in the formation of the catalyst for the first oxidation process, and an ammonium salt, nitrate, carbonate, chloride, lactate, hydroxide, organic acid salt, oxide, or mixture thereof of the metal element may be applied in combination. can

The catalyst for the first oxidation process may include: preparing a suspension in which the raw material compound is dissolved or dispersed in water; drying the suspension to obtain a solid; shaping the solid into an appropriate shape; And it may be prepared by a method comprising the step of calcining the molded solid.

In addition, the catalyst for the first oxidation process may be used by being supported on an inert carrier. When the inert carrier is used, the step of bringing the suspension into contact with the inert carrier before carrying out the drying step may be additionally performed.

There is no particular limitation on the shape of the catalyst for the first oxidation process, and a spherical shape, a cylindrical shape, a hollow shape, a ring shape, an irregular shape, etc. may be applied.

The size of the catalyst for the first oxidation process is, in the case of a cylindrical shape, the ratio (L/D) of the length (L) to the outer diameter (D) of the catalyst is preferably 0.5 to 1.3; In the case of cylindrical and spherical shapes, the outer diameter (D) of the catalyst is preferably 3 to 10 mm.

In the first oxidation process, the gas phase catalytic oxidation reaction may be performed under conventional conditions.

As an example, the raw material compound (1), molecular oxygen, and a mixed gas containing an inert gas (eg, nitrogen, carbon dioxide, water vapor, etc.) is supplied to the first oxidation reactor 100 and passed through a fixed catalyst bed. can

A first product (P1) containing methacrolein (MACR) is obtained through the first oxidation process.

(b) second oxidation process

In the second oxidation step, (a) the first product (P1) obtained in the first oxidation step is subjected to a gas phase catalytic oxidation reaction with a molecular oxygen-containing gas in the presence of a catalyst to obtain methacrylic acid (MAA) and unreacted methacrole It is a process of obtaining the second product (P2) containing the lane (MACR).

The second oxidation process may be performed in the second oxidation reactor 200 filled with the catalyst.

As the second oxidation reactor 200 , a reactor having a conventional configuration known to be usable for performing a gas phase catalytic oxidation reaction may be used.

Preferably, the (b) second oxidation process may be performed by changing the zone of the fixed catalyst bed in the reactor in which the (a) first oxidation process is performed.

As the catalyst of the second oxidation process, a composite metal oxide represented by the following Chemical Formula 2 may be used:

[Formula 2]

Mo _a P _b Cu _c V _d X _e Y _f O _h

In Formula 2,

Mo is molybdenum, P is phosphorus, Cu is copper, V is vanadium, O is oxygen,

X is iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), chromium (Cr) ), tungsten (W), manganese (Mn), silver (Ag), boron (B), silicon (Si), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi) ), niobium (Nb), tantalum (Ta), zirconium (Zr), indium (In), sulfur (S), selenium (Se), tellurium (Te), lanthanum (La), and cerium (Ce) At least one element selected from the group consisting of

Y is at least one element selected from the group consisting of potassium (K), rubidium (Rb), cesium (Cs), and thallium (Tl);

a, b, c, d, e, f, and h are the atomic ratios of each element,

When a=12, b is 0.1 to 3, c is 0.01 to 3, d is 0.01 to 3, e is 0 to 10, f is 0.01 to 3, and h is a number determined by the oxidation state of each element.

There is no particular limitation on the raw material compound used to form the catalyst for the second oxidation process, and the ammonium salt, nitrate, carbonate, chloride, lactate, hydroxide, organic acid salt, oxide, or mixture thereof of the metal element may be applied in combination. can

The catalyst for the second oxidation process may include: preparing a suspension in which the raw material compound is dissolved or dispersed in water; drying the suspension to obtain a solid; shaping the solid into an appropriate shape; And it may be prepared by a method comprising the step of calcining the molded solid.

In addition, the catalyst for the second oxidation process may be used by being supported on an inert carrier. When the inert carrier is used, the step of bringing the suspension into contact with the inert carrier before carrying out the drying step may be additionally performed.

There is no particular limitation on the shape of the catalyst for the second oxidation process, and a spherical shape, a cylindrical shape, a hollow shape, a ring shape, an irregular shape, etc. may be applied.

The size of the catalyst for the second oxidation process is, in the case of a cylindrical shape, the ratio (L/D) of the length (L) to the outer diameter (D) of the catalyst is preferably 0.5 to 1.3; In the case of cylindrical and spherical shapes, the outer diameter (D) of the catalyst is preferably 3 to 10 mm.

In the second oxidation process, the gas phase catalytic oxidation reaction may be performed under conventional conditions.

For example, the first product P1 obtained in the first oxidation process may be supplied to the second oxidation reactor 200 and passed through a fixed catalyst bed.

Preferably, the mixed gas containing the raw material compound (1), molecular oxygen, and an inert gas (eg, nitrogen, carbon dioxide, water vapor, etc.) is added to the fixed catalyst layer for the first oxidation process and the fixed catalyst layer for the second oxidation process sequentially It can be carried out by feeding the packed reactor through each fixed catalyst bed.

A second product (P2) containing methacrylic acid (MAA) and unreacted methacrolein (MACR) is obtained through the second oxidation process.

The second oxidation process may be performed so that the conversion rate of methacrolein according to Equation 1 is 40% or more and 60% or less.

[Equation 1]

Conversion rate (%) of methacrolein = [(number of moles of methacrolein reacted in the second oxidation process)/(number of moles of methacrolein supplied to the second oxidation process)] × 100

According to an embodiment of the invention, in the second oxidation process, the high level of conversion (eg, 75% or more or 80% or more) required in the process as shown in FIG. 1 is not required to be maintained, so the burden of process operation can be reduced. can

However, when the conversion rate of methacrolein according to Equation 1 in the second oxidation process is too low, the amount of inflow into the (e) oxidative esterification process increases, thereby increasing the oxidative esterification process and overall process efficiency. may cause degradation. Therefore, it is preferable that the second oxidation process is performed so that the conversion rate of methacrolein according to Equation 1 is maintained at 40% or more.

(c) purification process

The purification process is a process of separating methacrylic acid (MAA) and unreacted methacrolein (MACR) from the second product (P2) obtained in the (b) second oxidation process.

The purification process may be performed under the purification system 300 including a conventional purification means such as a distillation column.

For example, in the purification process, a distillation column such as a multi-stage column, a pack column containing a filler, a sieve tray column, a dual flow tray column, a scrubbing column, etc. may be used. have.

Methacrylic acid (MAA) separated from the second product (P2) through the purification process is supplied as a reactant of the subsequent (d) esterification process.

And, unreacted methacrolein (MACR) separated from the second product (P2) through the purification process is not recycled as a reactant of the second oxidation process (b).

That is, all unreacted methacrolein (MACR) separated from the second product (P2) through the purification process is supplied as a reactant to the subsequent process (e).

(d) esterification process

The esterification step is a step of obtaining a third product (P3) containing methyl methacrylate (MMA) by esterifying the methacrylic acid (MAA) obtained in the purification step (c) with methanol.

The esterification process may be performed in a conventional esterification reactor 400 .

The configuration of the esterification reactor 400 is not particularly limited.

The esterification process can be carried out in any manner known to the person skilled in the art and considered suitable. In this case, a polymerization inhibitor to prevent polymerization of methacrylic acid (MAA) may be used.

When the esterification occurs by a direct reaction between methacrylic acid and methanol, an esterification catalyst suitable for the reaction may be used. For example, an acidic ion exchange resin, sulfuric acid, etc. may be used as the esterification catalyst.

(e) oxidative esterification process

In the oxidative esterification process, unreacted methacrolein (MACR) obtained in the (c) purification process is reacted with methanol and molecular oxygen-containing gas by oxidative esterification to produce methyl methacrylate (MMA). This is a process of obtaining the contained fourth product (P4).

The oxidative esterification process may be performed in a conventional oxidative esterification reactor 500 .

The configuration of the oxidative esterification reactor 500 is not particularly limited.

The oxidative esterification process may be performed in a continuous reactor or a batch reactor.

The oxidative esterification process can be carried out in any manner known to the person skilled in the art and considered suitable. In this case, a polymerization inhibitor to prevent polymerization of methacrylic acid (MAA) may be used.

According to an embodiment of the invention, the oxidative esterification reaction in step (e) may be performed in the presence of a solid catalyst containing palladium and bismuth.

Since the oxidative esterification reaction is performed in the presence of a palladium-bismuth-containing catalyst, methacrylic acid can be obtained with a high selectivity of 90% or more, or 95% or more, or 98% or more, or 99% or more.

Preferably, as the catalyst in the oxidative esterification process, a solid catalyst including palladium (Pd) and bismuth (Bi) as active metals may be used. The solid catalyst may further include at least one element selected from the group consisting of iron (Fe), zinc (Zn), germanium (Ge), and lead (Pb).

The solid catalyst may further include an inert carrier selected from the group consisting of silica, alumina, silica-alumina, silicon carbide, and calcium carbonate as a carrier.

According to the present invention, there is provided a method for producing methyl methacrylate, which enables the improvement of catalyst life and an increase in production of methyl methacrylate while ensuring the safety of the process.

1 is a process diagram schematically showing a general process for producing methyl methacrylate.
2 is a process diagram schematically illustrating a process for producing methyl methacrylate according to an embodiment of the present invention.

Hereinafter, preferred embodiments are presented to help the understanding of the invention. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto.

In the following Examples and Comparative Examples, the conversion rate, selectivity, and yield in each reaction process were calculated according to the following formulas, respectively.

*Conversion rate (%) of isobutylene in the first oxidation step = [(number of moles of isobutylene reacted in the first oxidation step)/(number of moles of isobutylene supplied to the first oxidation step)] × 100

*Selectivity (%) of methacrolein in the first oxidation step = [(number of moles of methacrolein produced in the first oxidation step)/(number of moles of isobutylene reacted in the first oxidation step)] × 100

*Selectivity (%) of methacrylic acid in the first oxidation step = [(number of moles of methacrylic acid produced in the first oxidation step)/(number of moles of methacrolein reacted in the first oxidation step)] × 100

*Conversion rate (%) of methacrolein in the second oxidation step = [(number of moles of methacrolein reacted in the second oxidation step)/(number of moles of methacrolein supplied to the second oxidation step)] × 100

* Selectivity (%) of methacrylic acid in the second oxidation step = [(number of moles of methacrylic acid produced in the second oxidation step)/(number of moles of methacrolein reacted in the second oxidation step)] × 100

*Yield (%) of methacrylic acid in the second oxidation step = [(conversion rate of methacrolein in the second oxidation step) × (selectivity of methacrylic acid in the second oxidation step)]/100

*Conversion rate (%) of methacrolein in the esterification process = [(number of moles of methacrolein reacted in the esterification process)/(number of moles of methacrolein supplied to the esterification process)] × 100

*Selectivity of methacrylic acid in the esterification process (%) = [(number of moles of methacrylic acid produced in the esterification process)/(number of moles of methacrolein reacted in the esterification process)] × 100

*Yield (%) of methacrylic acid in the esterification process = [(conversion of methacrolein in the esterification process) × (selectivity of methacrylic acid in the esterification process)]/100

*Conversion rate (%) of methacrolein in oxidative esterification process = [(number of moles of methacrolein reacted in oxidative esterification process)/(number of moles of methacrolein supplied to oxidative esterification process) ] × 100

*Selectivity of methacrylic acid in the oxidative esterification process (%) = [(number of moles of methacrylic acid produced in the oxidative esterification process)/(number of moles of methacrolein reacted in the oxidative esterification process) ] × 100

*Yield (%) of methacrylic acid in oxidative esterification process = [(conversion of methacrolein in oxidative esterification process) × (selectivity of methacrylic acid in oxidative esterification process)]/100

production example One

Solution (1) was prepared by dissolving 1,000 g of ammonium molybdate while heating and stirring 3,000 ml of distilled water at 80°C. A transparent solution (2) was prepared by adding 70 g of nitric acid and 183 g of bismuth nitrate to 400 ml of distilled water and stirring. A solution (3) was prepared by mixing and stirring 380 g of iron nitrate, 111 g of cesium nitrate, and 1098 g of cobalt nitrate in 400 ml of distilled water.

The solution (2) and the solution (3) were sequentially added dropwise to the solution (1) to prepare a light brown suspension.

The suspension was dried at 250° C. using a spray dryer in an air stream to prepare a catalyst powder. A spherical catalyst having a diameter of 6 mm was prepared by mixing 200 g of glass fiber with the prepared catalyst powder and coating and molding a ball having a diameter of 3 mm.

The spherical catalyst was calcined at 480° C. for 5 hours in an air atmosphere, based on the raw material of the catalyst Mo ₁₂ Bi _{0 . 8} Fe _{2 . 0} Co _{8 . 0} Cs _{1 .} A composite metal oxide catalyst (catalyst for the first oxidation process) represented by ₀ O _x was obtained.

production example 2

MoO ₃ 1650 g, V ₂ O ₅ 43.5 g, 85% H ₃ PO ₄ 146.8 g, and distilled water 12 L were put into the reactor, and then stirred at 90 ° C. at 500 rpm to prepare a transparent aqueous solution.

The aqueous solution was evaporated under atmospheric pressure at 90° C. for 7 hours, and the volume of the aqueous solution was concentrated to 3000 ml, and a concentrated solution having a content of 1.77 ml of distilled water with respect to 1 g of a metal precursor including MoO ₃ and V ₂ O ₅ was obtained. .

The concentrate was further stirred for 18 hours to prepare a heteropoly acid. 265 g of the heteropoly acid epiridine, Cu(NO ₃ ) ₂ ·3H ₂ O 69.4 g, TaO ₂ 105.8 g, CsNO ₃ 187 g, and 5000 ml of distilled water were added, and stirred at room temperature to obtain a uniform blue slurry prepared.

The prepared slurry was separated from the reaction solvent and dried in an oven at 120° C. for 12 hours. A spherical catalyst having a diameter of 6 mm was prepared by mixing the dry slurry with 5 wt % of glass fiber based on the total content of the slurry, and coating and molding this on a 3 mm diameter ball.

The spherical catalyst was calcined at 400 ° C. for 5 hours in an air atmosphere, based on the raw material of the catalyst Mo ₁₂ P _{1 . 3} Cu _{0.3 V 0.5 Ta 0 . 25} Cs _{1 .} A composite metal oxide catalyst (catalyst for a second oxidation process) represented by ₀ O ₄₀ was obtained.

production example 3

5 g of palladium chloride and 0.5 g of bismuth nitrate are dissolved in aqua regia (a mixed acid solution made by mixing hydrochloric acid and nitric acid at a ratio of 3:1), the acid is evaporated to dryness, and the residue is dissolved in water to a capacity of 500 ml of palladium-bismuth mixture was prepared.

After using in a stirred reactor, 10 ml of palladium chloride and 100 ml of ethylene glycol were stirred at room temperature for 30 minutes, the palladium-bismuth mixture was added thereto, and mixed at 105 to 110 ° C. for 3 to 7 minutes to obtain a black colloidal solution. got

A colloidal solution having an alumina:palladium ratio of 100:1 was added to the colloidal solution, stirred for 1 hour, and then left for 24 hours. This was centrifuged and calcined at 500° C. for 1 hour to obtain a catalyst (catalyst for oxidative esterification process) in which palladium and bismuth were supported on alumina.

comparative example One

An oxidation reactor (100, 200), a purification system (300), and an esterification reactor (400) equipped with a reaction apparatus as shown in FIG. 1 was prepared.

The first oxidation reactor 100 is configured to circulate a heating medium in a stainless steel reactor having an inner diameter of 1 inch and a length of 300 cm. In the first reactor 100, the oxidation reaction is carried out while controlling the reaction temperature in order to maintain the conversion rate of isobutylene of 99.5% or more at the reaction temperature of 340 °C or higher.

The fluid flowing out of the first oxidation reactor 100 flows into the second oxidation reactor 200 connected in parallel made of stainless steel with a length of 300 cm. In the second oxidation reactor 200, a continuous reaction is carried out while maintaining a MACR reaction rate of 75% or more at a reaction temperature of 290 °C or higher.

At the raw material inlet of the first oxidation reactor 100, a mixed gas containing 6% by volume isobutylene, 12% by volume oxygen, 10% by volume water vapor, and 72% by volume nitrogen is provided at a space velocity of 1000 hr ^-1 were introduced successively. The first and second oxidation processes were continuously performed while the introduced mixed gas sequentially passed through the first fixed catalyst bed of the first oxidation reactor 100 and the second fixed catalyst bed of the second oxidation reactor 200 .

As a result of analyzing the mixed gas passing through the first fixed catalyst layer, it was confirmed that the conversion rate of isobutylene was 99.5%, the selectivity of methacrolein (MACR) was 83%, and the selectivity of methacrylic acid (MAA) was 4.2%. .

In order to prevent the flow rate in the second fixed catalyst layer from being increased, the second oxidation process was performed so that the conversion rate of methacrolein according to Equation 1 below was at least 75%. As a result of analyzing the mixed gas passing through the second fixed catalyst layer, it was confirmed that the selectivity of methacrylic acid (MAA) was 79%, and the recycling yield of methacrylic acid (MAA) was 67.5%.

[Equation 1]

Conversion rate (%) of methacrolein = [(number of moles of methacrolein reacted in the second oxidation process)/(number of moles of methacrolein supplied to the second oxidation process)] × 100

The product obtained in the second oxidation reactor 200 is introduced into a scrubbing column that is a purification system 300 and quenched. In the purification system 300 , most of the high boiling point substances and methacrylic acid (MAA) are condensed into the lower liquid phase. After filtering the lower liquid phase to remove suspended solids, it was supplied to a flash evaporator for extracting methacrylic acid (MAA).

Methacrylic acid (MAA) obtained through the purification was supplied to the esterification reactor 400 of the packed bed type.

The unreacted methacrolein (MACR) obtained from the scrubbing column is absorbed into the circulating fluid of the degassing tower after passing through the methacrolein absorption tower and the refrigerator. The unreacted methacrolein (MACR) obtained through the above process is recycled to the front end of the second fixed catalyst bed of the second oxidation reactor 200 and supplied as a raw material for the second oxidation process.

The esterification reactor 400 is supplied as a flow having a molar ratio of methacrylic acid (MAA): methanol of 1: 1.5, and the esterification reaction is continuously performed at 90° C. in the presence of a cation exchange resin catalyst.

The unreacted methacrylic acid (MAA) in the esterification reactor 400 was introduced into the reaction part of the esterification reactor through recycling. In the steady state, the recycling conversion rate of 50% and the selectivity of methyl methacrylate (MMA) close to about 100% were exhibited. Finally, the yield of methyl methacrylate (MMA) was confirmed to be 67.5% based on the introduced isobutylene.

Example One

An oxidation reactor 100 and 200, a purification system 300, an esterification reactor 400, and an oxidative esterification reactor 500 equipped with a reaction apparatus as shown in FIG. 2 were prepared.

The first oxidation reactor 100 is configured to circulate a heating medium in a stainless steel reactor having an inner diameter of 1 inch and a length of 300 cm. In the first reactor 100, the oxidation reaction is carried out while controlling the reaction temperature in order to maintain the conversion rate of isobutylene of 99.5% or more at the reaction temperature of 340 °C or higher.

The fluid flowing out of the first oxidation reactor 100 flows into the second oxidation reactor 200 connected in parallel made of stainless steel with a length of 300 cm. In the second oxidation reactor 200, a continuous reaction is carried out while maintaining a MACR reaction rate of 75% or more at a reaction temperature of 290 °C or higher.

At the raw material inlet of the first oxidation reactor 100, a mixed gas containing 6% by volume isobutylene, 12% by volume oxygen, 10% by volume water vapor, and 72% by volume nitrogen is provided at a space velocity of 1000 hr ^-1 were introduced successively. The first and second oxidation processes were continuously performed while the introduced mixed gas sequentially passed through the first fixed catalyst bed of the first oxidation reactor 100 and the second fixed catalyst bed of the second oxidation reactor 200 .

As a result of analyzing the mixed gas passing through the first fixed catalyst layer, it was confirmed that the conversion rate of isobutylene was 99.5%, the selectivity of methacrolein (MACR) was 83%, and the selectivity of methacrylic acid (MAA) was 4.2%. .

The second oxidation process was performed so that the conversion rate of methacrolein according to Equation 1 was 50% to 55%. As a result of analyzing the mixed gas passing through the second fixed catalyst layer, it was confirmed that the selectivity of methacrylic acid (MAA) was 87.5% and the yield of methacrylic acid based on isobutylene inflow was 44.1%.

[Equation 1]

Conversion rate (%) of methacrolein = [(number of moles of methacrolein reacted in the second oxidation process)/(number of moles of methacrolein supplied to the second oxidation process)] × 100

The product obtained in the second oxidation reactor 200 is introduced into a scrubbing column that is a purification system 300 and quenched. In the purification system 300 , most of the high boiling point substances and methacrylic acid (MAA) are condensed into the lower liquid phase. After filtering the lower liquid phase to remove suspended matter, it was supplied to a flash evaporator for extracting methacrylic acid (MAA).

Methacrylic acid (MAA) obtained through the purification was supplied to the esterification reactor 400 of the packed bed type. The esterification reactor 400 is supplied as a flow having a molar ratio of methacrylic acid (MAA): methanol of 1: 1.5, and the esterification reaction is continuously performed at 90° C. in the presence of a cation exchange resin catalyst.

The unreacted methacrylic acid (MAA) in the esterification reactor 400 was introduced into the reaction part of the esterification reactor through recycling. In the steady state, the recycling conversion rate of 50% and the selectivity of methyl methacrylate (MMA) close to about 100% were exhibited. Finally, the yield of methyl methacrylate (MMA) was confirmed to be 44.1% based on the introduced isobutylene.

All of the unreacted methacrolein (MACR) obtained through the purification was supplied to the oxidative esterification reactor (500). In the oxidative esterification reactor 500 which is a continuous reactor, the oxidative esterification reaction of methacrolein (MACR), methanol, and molecular oxygen-containing gas is performed in the presence of the palladium-bismuth-containing solid catalyst according to Preparation Example 3 above. became

Specifically, 500 g of the solid catalyst of Preparation Example 3 was added to a 1.2 L capacity external circulation stainless steel reactor equipped with a catalyst separator. The unreacted methacrolein (MACR) 5.4 L/hr and methanol 2L/hr were supplied to the reactor, and the oxidative esterification reaction was performed while maintaining the reaction temperature at 85° C. and the reaction pressure at 7 kg/cm ² . All unreacted solutions were recycled. When the reaction time of 5 hours elapsed after the steady state, the selectivity of methyl methacrylate (MMA) was 91.2%, and the yield of methyl methacrylate (MMA) based on the number of moles of isobutylene introduced was 34.1 % was confirmed.

Example 2

The first and second oxidation processes were performed under the same method as in Example 1, except that the conversion rate of methacrolein according to Equation 1 was 60% in the second oxidation process.

As a result of analyzing the mixed gas passing through the second fixed catalyst layer, it was confirmed that the selectivity of methacrylic acid (MAA) was 86.9% and the yield of methacrylic acid based on isobutylene inflow was 47.5%.

Purification was performed on the product obtained in the second oxidation reactor 200 in the same manner as in Example 1 above.

Methacrylic acid (MAA) obtained through the purification was supplied to the packed bed type esterification reactor 400, and the esterification reaction was performed in the same manner as in Example 1.

The unreacted methacrylic acid (MAA) in the esterification reactor 400 was introduced into the reaction part of the esterification reactor through recycling. In the steady state, the recycling conversion rate of 50% and the selectivity of methyl methacrylate (MMA) close to about 100% were exhibited. Finally, the yield of methyl methacrylate (MMA) was confirmed to be 47.5% based on the introduced isobutylene.

All of the unreacted methacrolein (MACR) obtained through the purification was supplied to the oxidative esterification reactor 500, and the oxidative esterification reaction was performed in the same manner as in Example 1. When the reaction time of 5 hours has elapsed after the steady state, the selectivity of methyl methacrylate (MMA) is 91.2%, and the yield of methyl methacrylate (MMA) based on the number of moles of isobutylene introduced is 30.3 % was confirmed.

Review

In the process according to Comparative Example 1, as unreacted methacrolein obtained in the purification process after the first and second oxidation processes is recycled to the previous stage of the second oxidation process, the conversion rate of methacrolein in the second oxidation process is increased It had to be kept above 75%. And, the yield of methyl methacrylate obtained through the esterification reactor 400 in the process according to Comparative Example 1 was confirmed to be 67.5%.

In the process according to Examples 1 and 2, as unreacted methacrolein obtained in the purification process after the first and second oxidation processes is supplied to the oxidative esterification reactor, methacrolein in the second oxidation process Stable process operation was possible even when the conversion rate was maintained at 55 to 60%. And, the yield of methyl methacrylate obtained in the esterification reactor 400 and the oxidative esterification reactor 500 in the process according to Examples 1 and 2 is 78.2% (Example 1) and 77.8% (Example 1) (Example 1) Example 2) was confirmed.

The yields for each process converted based on the number of moles of the input isobutylene 100 are shown in Table 1 below.

process product transference number (%) Comparative Example 1 Example 1 Example 2 first oxidation MAA 4.2 4.2 4.2 MACR 83.0 83.0 83.0 secondary oxidation MAA 67.5 44.1 47.5 MACR 28.5 37.6 33.2 esterification MMA 67.5 44.1 47.5 oxidative esterification MMA - 34.1 30.3

1: raw material compound
100: first oxidation reactor
200: second oxidation reactor
300: purification system
400: esterification reactor
500: oxidative esterification reactor
P1: first product containing methacrolein
P2: second product containing methacrylic acid and unreacted methacrolein
MAA: methacrylic acid
MACR: methacrolein
P3: methyl methacrylate-containing third product
P4: methyl methacrylate-containing fourth product
MMA: methyl methacrylate

Claims (8)

(a) a first oxidation process for obtaining a first product containing methacrolein (MACR) by subjecting isobutylene, tert-butyl alcohol or a mixture thereof to a gas phase catalytic oxidation reaction with a gas containing molecular oxygen in the presence of a catalyst ,
(b) a second product containing methacrylic acid (MAA) and unreacted methacrolein (MACR) by subjecting the first product obtained in step (a) to a gas phase catalytic oxidation reaction with a gas containing molecular oxygen in the presence of a catalyst a second oxidation process to obtain
(c) a purification process of separating methacrylic acid (MAA) and unreacted methacrolein (MACR) from the second product obtained in step (b);
(d) an esterification step of esterifying the methacrylic acid (MAA) obtained in the step (c) with methanol to obtain a third product containing methyl methacrylate (MMA), and
(e) a fourth product containing methyl methacrylate (MMA) by oxidative esterification reaction of unreacted methacrolein (MACR) obtained in step (c) with methanol and a gas containing molecular oxygen Including an oxidative esterification process to obtain
The (b) second oxidation process is performed so that the conversion rate of methacrolein according to the following formula 1 is 40% or more and 60% or less, a method for producing methyl methacrylate:
[Equation 1]
Conversion rate (%) of methacrolein = [(number of moles of methacrolein reacted in the second oxidation process)/(number of moles of methacrolein supplied to the second oxidation process)] × 100
delete The method of claim 1,
All of unreacted methacrolein (MACR) separated in the (c) purification process is supplied as a reactant to the process (e), a method for producing methyl methacrylate.
The method of claim 1,
In the step (e), the oxidative esterification reaction is performed in the presence of a solid catalyst containing palladium and bismuth.
5. The method of claim 4,
The solid catalyst further comprises, as a carrier, an inert carrier selected from the group consisting of silica, alumina, silica-alumina, silicon carbide, and calcium carbonate.
The method of claim 1,
The (e) oxidative esterification process is carried out in a continuous reactor or a batch reactor, a method for producing methyl methacrylate.
The method of claim 1,
The method for producing methyl methacrylate, wherein the catalyst in the (a) first oxidation process is a composite metal oxide represented by the following formula (1):
[Formula 1]
Mo _a Bi _b Fe _c Co _d X _e Y _f O _h
In Formula 1,
Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, O is oxygen,
X is at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), and titanium (Ti),
Y is nickel (Ni), tin (Sn), zinc (Zn), tungsten (W), chromium (Cr), manganese (Mn), magnesium (Mg), antimony (Sb), cerium (Ce), and titanium ( Ti) is at least one element selected from the group consisting of,
a, b, c, d, e, f, and h are the atomic ratios of each element,
When a=12, b is 0.1 to 10, c is 0.1 to 10, d is 1 to 10, e is 0.01 to 2, f is 0 to 3, and h is a number determined by the oxidation state of each element.
The method of claim 1,
The method for producing methyl methacrylate, wherein the catalyst in the (b) second oxidation process is a composite metal oxide represented by the following Chemical Formula 2:
[Formula 2]
Mo _a P _b Cu _c V _d X _e Y _f O _h
In Formula 2,
Mo is molybdenum, P is phosphorus, Cu is copper, V is vanadium, O is oxygen,
X is iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), chromium (Cr) ), tungsten (W), manganese (Mn), silver (Ag), boron (B), silicon (Si), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi) ), niobium (Nb), tantalum (Ta), zirconium (Zr), indium (In), sulfur (S), selenium (Se), tellurium (Te), lanthanum (La), and cerium (Ce) At least one element selected from the group consisting of
Y is at least one element selected from the group consisting of potassium (K), rubidium (Rb), cesium (Cs), and thallium (Tl);
a, b, c, d, e, f, and h are the atomic ratios of each element,
When a=12, b is 0.1 to 3, c is 0.01 to 3, d is 0.01 to 3, e is 0 to 10, f is 0.01 to 3, and h is a number determined by the oxidation state of each element.

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