KR20080042382A - Method for preparing aromatic carbonate and reaction equipment for the same - Google Patents

Abstract

A method for preparing an aromatic carbonate is provided to avoid a need for a step for separating a heterogeneous catalyst, to increase the concentration of low-boiling point reactants, and to enable continuous removal of byproducts, thereby realizing excellent productivity and cost-efficiency. A method for preparing an aromatic carbonate by using a dialkyl carbonate or alkylaryl carbonate and aromatic hydroxyl compound as reactants comprises the steps of: (i) injecting the reactants to the top of a heterogeneous catalyst layer(1b) fixed to a reactor(1); (ii) passing a mixture containing the resultant product obtained after a part of the reactants undergoes a reaction in the catalyst and the remaining reactants through the catalyst layer; (iii) carrying out heat exchange between a part of the liquid reactants in the mixture and vaporous reactants in a column(1c) installed at the bottom of the catalyst layer and transferring the heat exchanged mixture back to the catalyst layer, and sending the remaining mixture to a heat exchanger(3) linked to the bottom of the reactor; (iv) heating the mixture transferred to the heat exchanger, introducing the vaporous reactants into the bottom of the column, discharging a part of the liquid mixture to the exterior of the reactor by controlling the level, and introducing the remaining liquid mixture to the top of the catalyst layer; (v) discharging the vaporous byproducts generated from the top of the catalyst layer and vaporous reactants forming an azeotropic mixture with the byproducts to the exterior of the reactor through a distillation tower(5) linked to the top of the reactor, followed by cooling; and (vi) partially refluxing the cooled liquid byproducts and the reactants to the top of the catalyst layer.

Description

A method for producing an aromatic carbonate and a manufacturing apparatus therefor {METHOD FOR PREPARING AROMATIC CARBONATE AND REACTION EQUIPMENT FOR THE SAME}

1 is a view showing an apparatus for producing an aromatic carbonate according to a preferred embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1 reactor 1a support

1b: catalyst layer 1c: column layer

3: heat exchanger 4,7,9: circulation pump

5: distillation column 6: cooling tower

11: Pipe connected to the lower side of the column bed 12: Pipe connected to the lower side of the catalyst bed

13 pipe connected to the upper side of the catalyst bed

The present invention relates to a method for producing an aromatic carbonate and an apparatus for manufacturing the same, and more particularly, by using a fixed heterogeneous catalyst, a catalyst separation process is not required, and a reactant is introduced into a reactor through a heat exchanger and a circulation pump. By increasing the concentration of the reactants in the reactor and by continuously removing the reaction by-products relates to a method for producing a high conversion rate, selectivity aromatic carbonate and its manufacturing apparatus.

Aromatic carbonates are used as raw materials for the production of aromatic polycarbonates and various types of isocyanates that do not use toxic phosgene gases. Are synthesized. At this time, examples of the reaction raw material mainly used include dimethyl carbonate and phenol.

However, the transester reaction is a reversible reaction, so the equilibrium constant of the reaction is very small, the conversion after the reaction is very low, and the reaction rate is also very slow, there are many difficulties in commercial production.

In order to solve this problem, various efforts have been made, among which attempts have been made to increase the reaction rate by improving the performance of the reaction catalyst. U.S. Patent No. 4,182,726 discloses a process using a _{AlX 3, UX 3, TiX 3} , VOX 3, VX 3, ZnX 2, a reaction catalyst of the FeX ₃ and SnX ₃ series, such as AlCl ₃ are disclosed. (Wherein X is Halogen group)

In addition, US Patent No. 4,045,464 discloses Ti-based compounds such as Lewis acid or titanium tetraphenate as reaction catalysts. In addition, US Patent No. 4,552,704 discloses a Ti and Sn-based reaction catalyst such as butyltin oxide hydroxide, US Patent No. 4,554,110 is a reaction catalyst, a polymeric tin compound US Patent No. 4,609,501 discloses a reaction catalyst in which at least one Lewis acid and one protic acid are mixed.

The prior art can be seen that the efforts to improve the reaction rate by the reaction catalyst rather than improving the reactivity by the reaction process in order to increase the efficiency of producing diphenyl carbonate (DPC) from dimethyl carbonate (DMC). However, all of the catalysts proposed in the above-described invention should be used as a homogeneous catalyst by mixing the reactants in a certain ratio, although the reaction rate is continuously removed from the reaction system, although reaction by-products such as methanol generated during the reaction are applied. Not high.

On the other hand, there have been attempts to use heterogeneous catalysts as reaction catalysts. U.S. Patent No. 5,354,923 uses a stirred reactor using a powdered catalyst having a surface area of 20 m ² / g or more, and U.S. Patent No. 5,565,605 used a heterogeneous catalyst such as titanoalumino phosphate in the reaction.

However, until now, heterogeneous catalysts have been reacted and separated together with reactants in powder form, causing them to stick to the inner wall of equipment and pipes, causing problems. The problem still exists.

Along with the development of reaction catalysts, efforts have been made to increase the efficiency of DPC manufacturing by designing unique reaction processes. U.S. Patent No. 5,210,268 uses a multi-stage distillation column as a reactor to inject a high-boiling reactant with a homogeneous catalyst in the upper layer of the tower, and the low-boiling reactant is heated and vaporized at the bottom of the column to make two reactants with different boiling points countercurrently. Aromatic carbonates were synthesized. In addition, U. S. Patent No. 5,426, 207 discloses a reaction process using three reactors connected in series, and U. S. Patent No. 5,523, 451 discloses a process in which a plurality of bubble columns connected in series are applied to the reactor. In addition, US Pat. No. 6,507,470 discloses a reaction process using reactive distillation techniques.

However, these processes still have many difficulties in separating catalysts using homogeneous catalysts or catalysts in powder, and there are economic problems in that a constant amount of catalyst must be continuously supplied to the reaction system during continuous operation.

It is an object of the present invention to prepare an aromatic carbonate by reacting a dialkyl carbonate with an aromatic hydroxy compound under a heterogeneous catalyst, which does not require separation of the catalyst, increases the concentration of the low boiling point reactant in the reactor and removes reaction byproducts. Is made continuously to provide a method of producing an aromatic carbonate excellent in productivity and economics.

Still another object of the present invention is to provide an apparatus for producing an aromatic carbonate which can be used in the method for producing the aromatic carbonate.

The present invention provides a method for producing an aromatic carbonate comprising a dialkyl carbonate or an alkyl aryl carbonate and an aromatic hydroxy compound as a reactant.

(1) injecting the reactant on top of the heterogeneous catalyst layer fixed in the reactor;

(2) a portion of the reactant is passed through the catalyst layer after the reaction proceeds in the catalyst layer and the mixed solution including the product and the reactant;

(3) a part of the reactant in the liquid phase of the mixed liquid is heat-exchanged with the gaseous reactant in the column layer installed under the catalyst layer to be moved back to the catalyst layer, and the remaining mixed liquid is moved to a heat exchanger connected to the bottom of the reactor;

(4) After heating the mixed liquid moved to the heat exchanger, the gaseous reactant is introduced into the lower side of the column layer, a portion of the liquid mixture is taken out of the reactor by adjusting the water level, and the remaining liquid mixture is added to the upper side of the catalyst layer. Doing;

(5) the gaseous by-products on the catalyst bed and the gaseous reactants azeotropic with the by-products are cooled after being discharged to the outside of the reactor through a distillation column connected to the top of the reactor; And

(6) refluxing the by-product and reactant portions of the cooled liquid phase above the catalyst bed;

It provides a method for producing an aromatic carbonate comprising a.

In addition, the present invention includes a reactor including a heterogeneous catalyst layer fixed to the support and a column layer installed below the support; A heat exchanger connected to a lower end of the reactor to heat the mixed solution passing through the column layer, and then introducing a gaseous reactant into the upper catalyst layer, the lower catalyst layer, or the lower column column; A first circulation pump for moving the liquid mixture introduced from the heat exchanger to the upper side of the catalyst bed; A distillation tower connected to an upper end of the reactor to allow a gaseous by-product on the upper side of the catalyst layer and a gaseous reactant to form an azeotropic product with the by-product out of the reactor; A cooling tower connected to an upper portion of the distillation tower to cool the gaseous by-products and reactants in a liquid phase; A second circulation pump configured to receive liquid by-products and reactants from the lower part of the cooling tower and circulate the upper part of the cooling tower; A cooler installed between the second circulation pump and an upper portion of the cooling tower; And a third circulation pump for refluxing a part of the liquid by-products and the reactants in the lower part of the cooling tower to the distillation column.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method and apparatus for producing an aromatic carbonate using a heterogeneous catalyst using a dialkyl carbonate or an alkyl aryl carbonate and an aromatic hydroxyl compound as a reactant. It is characterized by increasing the concentration of the low boiling point reactant in the reaction and using a heterogeneous catalyst as a reaction catalyst.

The dialkyl carbonate may be represented by the following formula (1).

(In formula (1), R is an alkyl group. The alkyl group is a general alkyl group such as methyl, ethyl, propyl, butyl, cyclohexyl, etc.)

The aromatic hydroxy compound represented by the dialkyl carbonate and ArOH (where Ar is an aromatic group) is synthesized by alkyl aryl carbonate represented by the following Chemical Formula 2 by transesterification and reacted as a reaction byproduct. Alkyl alcohol is produced. In addition, the alkyl aryl carbonate is synthesized into an aromatic carbonate represented by the following formula (3) by disproportionation or transesterification with an aromatic hydroxy compound.

(In the formulas (2) and (3), each Ar is an aromatic group having 5 to 30 carbon atoms.

Typical schemes relating to the reaction process of the present invention can be represented by the following schemes 1-3.

Scheme 1

Scheme 2

Scheme 3

(In the formulas 1, 2, and 3, R is an alkyl group, and Ar is an aromatic group.)

The reactions shown above are reversible reactions in which equilibrium exists, and high reaction conversion can be obtained by taking out reaction by-products generated during the reaction out of the reaction system. Can be increased.

The reaction catalyst used in the present invention may be a transition metal oxide as a heterogeneous catalyst, preferably MoO ₃ , Ga ₂ O ₃ , V ₂ O ₅ , PbO, ZrO ₂ , TiO ₂ , CdO, Fe ₂ O ₃ , CuO, MgO, Y ₂ O ₃ , Mn ₃ NiO, ZnO, Nd ₂ O ₃ , Co ₂ O ₃ , Ru ₂ O ₃ , Nb ₂ O ₅ , Cr ₂ O ₃ It can be selected and used above.

The heterogeneous catalyst uses a carrier such as silica, and the carrier is formed in a spherical, cylindrical, ring, or the like shape having a size of 1 to 200 mm. In this case, the specific surface area of the silica may be 20 to 500 m ² / g, and the porosity may be 0.25 to 0.8 cm ³ / g, more preferably 0.4 to 0.75 cm ³ / g.

The heterogeneous catalyst is introduced by adjusting the amount of aromatic carbonate to be produced. That is, the amount of heterogeneous catalyst required for production is determined after experimentally determining the amount of aromatic carbonate prepared for a predetermined residence time by a certain amount of catalyst.

Reactants comprising dialkyl carbonates or alkyl aryl carbonates and aromatic hydroxy compounds are injected above the fixed heterogeneous catalyst layer. At this time, the molar ratio of the dialkyl carbonate or alkyl aryl carbonate or a mixture thereof and the aromatic hydroxy compound may be 5: 1 to 1: 5. The injected reactant passes through the catalyst bed and undergoes heat exchange by contacting with the low boiling point reactant vaporized by a heat exchanger in a column installed under the catalyst bed. Some of the reactants move to the catalyst bed like the low boiling point reactant and partially unreacted with the product produced through the reaction. The mixed solution containing the reactants is transferred to a heat exchanger connected to the bottom of the reactor.

The heat exchanger is applied to the mixed liquid lowered to the bottom of the reactor to separate the low-boiling reactant and the remaining high-boiling liquid mixture, the low-boiling reactant is recovered by moving to the bottom of the column of the reactor in the vaporized state, wherein the low-boiling reactant is In addition to the bottom of the column layer, the catalyst layer may be moved above or below the catalyst layer.

The remaining mixture which is not vaporized is recovered by the first circulation pump above the catalyst bed. At this time, a part of the mixed liquid including the product is taken out of the reactor by adjusting the level of the mixed liquid in the heat exchanger.

The extracted product is an aromatic boiling point of a high boiling point component, and may be subjected to a conventional purification process such as distillation or crystallization after extraction.

The temperature of the mixed liquid by the heating may vary depending on the pressure of the reactor, but preferably 100 ° C to 300 ° C, more preferably 150 ° C to 250 ° C. At such a temperature, the reaction pressure is suitably 1 to 20 atmospheres, more preferably 5 to 10 atmospheres.

 On the upper side of the catalyst layer, alkyl alcohol, which is a by-product of reaction, and relatively low boiling point alkyl carbonates are discharged out of the reactor through a distillation column in a gaseous state. Cooling condensation occurs in contact with the liquid alkyl alcohol and the relatively low boiling alkyl carbonate in the column bed of the cooling tower. The condensate generated at this time is refluxed or taken out to the distillation step in whole or in part.

Next, the manufacturing apparatus according to the present invention will be described.

A reactor equipped with a support for supporting a catalyst and a column layer positioned at the bottom of the catalyst bed fixed by the support, and a heat exchanger for vaporizing the low boiling point reactant from the mixed solution containing the reactants and the product by vaporizing it to the lower side of the column layer 1c, The remaining mixture liquid not vaporized in the heat exchanger is transferred to the lower side of the column (1c) and the upper side of the catalyst layer (1b) or the lower side of the catalyst layer (1b) by the second circulation pump, and the reaction by-products are connected to the upper portion of the reactor. It is a device designed to be removed through a distillation column.

Referring to the drawings in more detail the present invention,

The reactor 1 includes a heterogeneous catalyst layer 1b fixed to the support 1a and a column layer 1c provided below the support 1a.

The heat exchanger (3) passes through the column layer (1c) and heats the mixed liquid introduced from the bottom of the reactor (1), and then pipes (13) and catalyst layer (s) connecting the gaseous low boiling point reactant to the upper side of the catalyst layer (1b). 1b) Through the pipe 12 connected to the lower side or the pipe 11 connected to the lower side of the column layer 1c is introduced into the reactor 1 and circulated.

The first circulation pump 4 moves the high boiling point liquid mixture which is not vaporized from the heat exchanger 3 to the upper portion of the catalyst layer 1b through the pipe 14.

At this time, by adjusting the level of the mixed liquid in the heat exchanger 3, a part of the mixed liquid including the product is taken out through the pipe 15 to the outside of the reactor.

The distillation column 5 connected to the upper end of the reactor 1 discharges the gaseous by-products on the upper side of the catalyst layer 1b and the gaseous reactants forming the azeotrope with the by-products to the outside of the reactor 1. The cooling tower 6 connected to the upper part of the distillation tower 5 cools the by-products and reactants of the gaseous phase introduced from the distillation tower 5 in the liquid phase, and the second circulation pump 7 below the cooling tower 6 is The liquid by-products and reactants are supplied and circulated to the upper portion of the cooling tower 6. At this time, a cooler 8 is installed between the second circulation pump 7 and the upper portion of the cooling tower 6.

Part of the liquid by-products and reactants in the lower portion of the cooling tower 6 may be refluxed to the distillation column through the third circulation pump 9 or may be partially taken out of the cooling tower through the pipe 17.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are intended to illustrate the present invention, but are not limited to these.

EXAMPLE

Dimethyl carbonate (DMC) was used as a dialkyl carbonate as a raw material, and phenol was used as an aromatic hydroxy compound. Example 1 was mixed so that the phenol molar ratio of dimethyl carbonate (DMC) and the raw material is 3: 1, Example 2 was mixed so that the phenol molar ratio of dimethyl carbonate (DMC) and the raw material is 2: 1 and then the metering high pressure pump Was injected continuously into the reactor at a flow rate of 25 g / min. Regarding the recirculation of the gas phase component through the heat exchanger, in Example 1 75% by weight of the gas phase component was introduced into the bottom of the column under the catalyst bed, and 25% by weight was introduced into the bottom of the catalyst bed. In Example 2, 65% by weight was added to the bottom of the column under the catalyst bed, 30% by weight was added to the bottom of the catalyst bed and 5% by weight to the top of the catalyst bed.

The reaction temperature was 180 ° C. and the reaction pressure was maintained at 7 atmospheres. At this time, the flow rate of the reaction solution circulated by the circulation pump was maintained at 500g / min. The reaction proceeded continuously under the same conditions for 24 hours or more, and the catalyst used was a heterogeneous catalyst loaded with titania (TiO 2) on silica having a diameter of 3 mm, and the amount of catalyst charged in the reactor was 1500 g.

As a result of the reaction, the phenol conversion rate of Example 1 was 30.4%, and the phenol conversion rate of Example 2 was 23.6%.

Comparative Example 1

In order to prepare for the present invention, using the reaction apparatus disclosed in Korean Patent No. 0536185, the weight of the total amount of the reactants is 2 kg (DMC: PhOH molar ratio = 3: 1), and other reaction conditions are the same experimental conditions as those of Example 1 above. It was done in. For reference, unlike the reactor of the present invention, the reactor is a device in which a reactant passed through a heat exchanger is moved to a distillation column without being recycled to the reactor.

The reaction result showed that the phenol conversion was 22.5%.

Examples 1 to 2, the conversion rate and the yield of Comparative Example 1 are summarized in Table 1 below.

Total amount of reactants (kg) DMC: PhOH molar ratio PhOH conversion rate (%) MPC yield (PhOH,%) ^a MPC yield (feed,%) ^b Example 1 9 3: 1 30.4 41.4 10.4 Example 2 9 2: 1 23.6 33.2 11.1 Comparative example 2 3: 1 22.5 32.0 8.0

(a: MPC weight / (PhOH weight + MPC weight) b: MPC weight / reactant weight)

Table 2 below is the content of the final composition of the circulating fluid through the heat exchanger in Example 1 and Comparative Example 1.

In the present invention, a heterogeneous catalyst is used as a reaction catalyst. When the homogeneous catalyst is used, the catalyst and the reactants do not stick to the device and the inner wall of the pipe, and the high boiling point reaction product and the catalyst do not exist. It has the effect of making continuous aromatic carbonates possible.

In addition, by introducing a reactant into the reactor through a heat exchanger and a circulation pump, the reaction by-products are continuously removed, thereby increasing the conversion rate and product efficiency.

Claims (7)

In the method for producing an aromatic carbonate comprising a dialkyl carbonate or an alkyl aryl carbonate and an aromatic hydroxy compound as a reactant, (1) injecting the reactant on top of the heterogeneous catalyst layer fixed in the reactor; (2) a portion of the reactant is passed through the catalyst layer after the reaction proceeds in the catalyst layer and the mixed solution including the product and the reactant; (3) a part of the reactant in the liquid phase of the mixed liquid is heat-exchanged with the gaseous reactant in the column layer installed under the catalyst layer to be moved back to the catalyst layer, and the remaining mixed liquid is moved to a heat exchanger connected to the bottom of the reactor; (4) After heating the mixed liquid moved to the heat exchanger, the gaseous reactant is introduced into the lower side of the column layer, a part of the liquid mixture is taken out of the reactor by adjusting the water level, and the remaining liquid mixture is added into the upper portion of the catalyst layer. Making; (5) the gaseous by-products on the catalyst bed and the gaseous reactants azeotropic with the by-products are cooled after being discharged to the outside of the reactor through a distillation column connected to the top of the reactor; And (6) refluxing the by-product and reactant portions of the cooled liquid phase above the catalyst bed; Method for producing an aromatic carbonate comprising a. The method of claim 1, wherein the heterogeneous catalyst layer comprises a transition metal oxide heterogeneous catalyst supported on a carrier. The method of claim 2, wherein the transition metal oxide is MoO ₃ , Ga ₂ O ₃ , V ₂ O ₅ , PbO, ZrO ₂ , TiO ₂ , CdO, Fe ₂ O ₃ , CuO, MgO, Y ₂ O ₃ , Mn ₃ NiO, ZnO, Nd ₂ O ₃ , Co ₂ O ₃ , Ru ₂ O ₃ , Nb ₂ O ₅ or Cr ₂ O _{3 The} method for producing an aromatic carbonate, characterized in that. The method of claim 2, wherein the carrier has a specific surface area of 20 to 500 m ² / g and a porosity of 0.25 to 0.8 cm ³ / g. The method of claim 1, wherein the gaseous reactant of step (4) is introduced into the upper or lower side of the catalyst layer in addition to the lower side of the column layer. The method according to any one of claims 1 to 5, The reactor internal temperature is a method for producing an aromatic carbonate, characterized in that 100 ℃ to 300 ℃. A reactor including a heterogeneous catalyst layer fixed to a support and a column layer disposed below the support; A heat exchanger connected to a lower end of the reactor to heat the mixed solution passing through the column layer, and then introducing a gaseous reactant into the upper catalyst layer, the lower catalyst layer, or the lower column column; A first circulation pump for moving the liquid mixture introduced from the heat exchanger to the upper side of the catalyst bed; A distillation tower connected to an upper end of the reactor to allow a gaseous by-product on the upper side of the catalyst layer and a gaseous reactant which forms an azeotropic product with the by-product to the outside of the reactor; A cooling tower connected to an upper portion of the distillation tower to cool the gaseous by-products and reactants in a liquid phase; A second circulation pump configured to receive liquid by-products and reactants from the lower part of the cooling tower and circulate the upper part of the cooling tower; A cooler installed between the second circulation pump and an upper portion of the cooling tower; And a third circulation pump for refluxing a part of the liquid by-products and the reactants in the lower part of the cooling tower to the distillation column.

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