KR100785254B1 - Heteropoly acid catalyst supported on metal oxides and production method of dimethylcarbonate using said catalyst - Google Patents

Abstract

The present invention relates to a heteropoly acid-supported catalyst for synthesizing dimethyl carbonate from methanol and carbon dioxide, and to a method for preparing dimethyl carbonate using the catalyst. The present invention relates to a heteropoly acid supported catalyst prepared by supporting a metal oxide and a dimethyl carbonate production method using the catalyst. The heteropoly acid supported catalyst according to the present invention has high reactivity when applied to synthesize dimethyl carbonate from methanol and carbon dioxide. Dimethyl carbonate can be obtained, does not involve side reactions and provides an environmentally friendly synthesis process.

Dimethyl carbonate, heteropoly acid, metal oxide, supported catalyst

Description

Heteropoly acid-supported catalyst and method for producing dimethyl carbonate using the above catalyst {{HETEROPOLY ACID CATALYST SUPPORTED ON METAL OXIDES AND PRODUCTION METHOD OF DIMETHYLCARBONATE USING SAID CATALYST}

The present invention relates to a heteropoly acid-supported catalyst and a method for preparing dimethyl carbonate using the catalyst, and more particularly, to a dimethyl carbonate prepared from methanol and carbon dioxide, and to a heteropoly acid supported by preparing a heteropoly acid having acidic properties on a metal oxide It relates to a catalyst and a method for producing dimethyl carbonate from methanol and carbon dioxide using the catalyst.

Dimethyl carbonate has attracted attention as an environmentally friendly chemical product as a carbonylating or methylating agent of fine chemicals. Furthermore, dimethyl carbonate can replace toxic phosgene, methyl chloride, dimethyl sulfate, etc., as well as additives to increase the octane number of automobile fuels, raw materials for the production of polycarbonate resins, and intermediates for fine chemical products. Very wide Conventional methods for preparing dimethyl carbonate are very diverse. For example, a phosgene method for reacting methanol and toxic phosgene, a methanol oxidation method for reacting carbon monoxide and oxygen with methanol, a methyl nitrate method using methyl nitrate, a transesterification method using ethylene oxide, and the like. There are two types of methanol oxidation methods: liquid phase method and gas phase method. Cu (I) or Cu (II) is mainly used as a catalyst of the liquid methanol oxidation method, and a mixture with another promoter may be used. When the copper chloride catalyst is used, the selectivity of dimethyl carbonate is still not satisfactory at around 25%, and a volatile methyl chloride is formed as a by-product, which is known to cause corrosion problems. 4,900,705]. In the case of a mixed catalyst using a Cu (I) catalyst and potassium chloride as a cocatalyst, it is known that the methanol conversion and the dimethyl carbonate selectivity are improved when the water content in the reactant is controlled to 3% by weight or less [US Patent No. 5,599,965]. And European Patent 636,601. The liquid methanol oxidation method reported above can cause safety problems by using carbon monoxide as a reactant, and a lot of by-products are generated, causing corrosion of the reactor. The gas phase reaction technique has been proposed to improve the disadvantage of the liquid phase reaction, which is limited by the reactor size. However, in the case of the gas phase reaction, the catalyst is deactivated because chlorine is removed from the catalyst during the reaction. Catalysts used in the methanol gas phase oxidation method include metal halides and their complexes [WO 87/7601], copper halides and alkaline earth metal hydroxides supported on porous supports [US Pat. No. 5,347,031], palladium-based catalysts [US Pat. 5,466,856]. Heterogeneous catalysts used as transesterification catalysts that are known to exhibit relatively high conversions include tertiary amines, quaternary ammonium salts, sulfonic acids, ion exchange resins containing carboxylic acids, alkali metals, alkaline earth metals, and silica supported silicates. Or zeolites in which ammonium ions have been exchanged. [US Pat. In addition, a method using a styrene-divinylbenzene copolymer substituted with triphenylphosphine [US Pat. No. 5,214,182] and a method of using an inorganic compound containing lead as a heterogeneous catalyst [JP-A-49356] Recently, rare earth-based oxides such as yttrium (Y), lanthanum (La), cerium (Ce) [US Pat. No. 5,430,170], or A-type zeolites carrying K, Na, Ca and the like [US Pat. No. 5,436,362] A method of using an inorganic compound such as Ho) as a catalyst has been reported. When the catalyst is reacted for at least tens of hours in the range of 50 to 160 ° C., a conversion rate of 50 to 60% of ethylene carbonate and a yield of about 30 to 50% of dimethyl carbonate can be obtained. However, there is a problem that the yield of dimethyl carbonate is considerably lowered by side reactions. The dimethyl carbonate synthesis reaction reported above has the disadvantage of using mostly carbon monoxide, which is a toxic substance, and having high corrosiveness, and has a problem in that a by-product is generated by the progress of a side reaction by a catalyst, thereby making a multi-step reaction.

In order to overcome this problem, a method of directly synthesizing dimethyl carbonate from methanol and carbon dioxide has recently been reported [K. Tomishige, T. Sakaihori, Y. Ikeda, K. Fujimoto, Catal. Lett., Vol. 58, p. 225 (1999) / S. Fang, K. Fujimoto, Appl. Catal. A: Geneneral, Vol. 142, L1 (1996)]. However, no suitable catalyst system and efficient synthesis method have been proposed.

On the other hand, heteropolyacid catalysts based mainly on phosphorus and molybdenum have been used as catalysts because of their unique strong acid properties and oxidizing ability.However, due to their poor thermal stability, they are easily deteriorated and are easily reduced due to their strong oxidation ability. The crystallization property is very strong at low temperature, whereas the crystallization property is higher than 150 ° C, and the cohesion force between particles is extremely weak and easily crushed. Therefore, the catalyst performance is improved by improving the electrical, chemical and physical and chemical properties of the catalyst using various metals or by adding organic and inorganic compounds in the preparation of the catalyst to control the physical properties of the catalyst such as surface area, pore volume, and pore distribution. The results of partial technical development to remedy the above disadvantages can be found in the following patent documents. For example, U.S. Patents 4,042,625, 4,272,408, JP-A-82-32734, 83-74142, 83-166938, 86-5043, 86-76436, 88-167152, Korean Patent 36019, 36020, and the like, The Japanese Patent Application Laid-Open Publication Nos. 82-12830, 84-66349, 89-119942, 92-16242 and others disclose organic and inorganic compounds such as nitrogen heterocyclic compounds, urea, organic reducing substances, ammonium nitrate, ammonium carbonate, and ammonium sulfate. Additives were added, and the catalyst production conditions and methods such as addition time and aging temperature of the catalyst components were controlled to improve catalyst performance. However, none of the above documents used the above heteropolyacid supported catalyst in producing dimethyl carbonate from methanol and carbon dioxide.

Therefore, the present invention is to provide an effective catalyst for the direct synthesis of dimethyl carbonate from methanol and carbon dioxide.

Another technical problem of the present invention is to provide a method of directly synthesizing dimethyl carbonate from methanol and carbon dioxide which are environmentally friendly raw materials using the catalyst.

In order to achieve the above technical problem, the present invention is used to prepare dimethyl carbonate from methanol and carbon dioxide, and provides a heteropoly acid supported catalyst prepared by supporting a heteropoly acid having acidic properties on a metal oxide.

In addition, in the present invention, the heteropolyacid is at least one element selected from the group consisting of tungsten (W), molybdenum (Mo), vanadium (V) and niobium (Nb), and the phosphorus (P), silicon ( Provided is a heteropolyacid-supported catalyst characterized in that the structure of the inorganic condensed acid wherein at least one element selected from the group consisting of Si) and cobalt (Co) is the central element.

In addition, the present invention is the heteropoly acid is 12- tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ), 12- molybdo phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ), 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ) And _12- molybdo tungstophosphoric acid (H ₃ PMo _12-x W _x O ₄₀ , x = 0-12) to provide a heteropolyacid-supported catalyst.

In addition, in the present invention, the metal oxide as the carrier is zirconium oxide (ZrO ₂ ), magnesium oxide (MgO), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂₎ It provides a heteropoly acid supported catalyst, characterized in that at least one member selected from the group consisting of O ₃ ).

In order to achieve another technical problem of the present invention, the present invention provides a method for producing dimethyl carbonate by reaction of 5 to 70 atm of carbon dioxide and methanol at a temperature of 100 to 200 ℃ in the presence of the heteropoly acid supported catalyst. to provide.

Hereinafter, the present invention will be described in detail.

The heteropolyacid supported catalyst of the present invention is used to prepare dimethyl carbonate from methanol and carbon dioxide, and is prepared by supporting heteropolyacid having acidic properties on a metal oxide. As described above, there is no example of using a heteropolyacid supported catalyst to prepare dimethyl carbonate from methanol and carbon dioxide, and the present inventors have found that the heteropoly acid supported catalyst is very effective in preparing the dimethyl carbonate and have completed the present invention.

Typical heteropolyacid catalysts act not only as redox catalysts but also as acid catalysts due to the acid properties of the catalysts. The reason why the heteropolyacid-carrying catalyst of the present invention exhibits superior catalytic activity compared to the metal oxide catalyst is not known yet. However, the results of the present inventors have shown that the Bronsted acid point of the heteropolyacid catalyst enhances the acidity of the metal oxide, thereby enhancing the methyl group of methanol. It is estimated that the effect of increasing the conversion is induced to increase the activity of the reaction of synthesizing dimethyl carbonate directly from methanol and carbon dioxide.

The heteropolyacid used in the heteropolyacid supported catalyst of the present invention may be a commercially available material or a catalyst material prepared by a conventional method, and the catalyst material is preferably recrystallized at 300 ° C. or higher. The heteropolyacid is at least one member selected from the group consisting of tungsten (W), molybdenum (Mo), vanadium (V), and niobium (Nb), and phosphorus (P), silicon (Si), and cobalt (Co). It is preferable that at least one selected from the group consisting of C) is an inorganic condensed acid serving as a central element, more preferably ₁₂ -tungstoic acid (H ₃ PW ₁₂ O ₄₀ ), 12-molybdate phosphoric acid (H ₃ PMo). ₁₂ O ₄₀ ), 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ) and _12- molybdoung tungstophosphoric acid (H ₃ PMo _12-x W _x O ₄₀ , x = 0-12) It is preferable that it is at least one selected.

The heteropolyacid supported catalyst may be prepared by the following method. The present invention is characterized by dissolving a heteropoly acid in a solvent in order to add an acid characteristic to a metal oxide, and then supporting it in a metal oxide, followed by heat treatment to prepare a supported catalyst, and using the catalyst to prepare dimethyl carbonate from methanol and carbon dioxide.

In preparing the heteropolyacid supported catalyst of the present invention, it is easy to use the heteropolyacid to be dissolved in a solvent and used in the form of a solution. There is no particular restriction on the concentration of the solution, and a minimum amount of solvent capable of dissolving the heteropolyacid may be used. Preferably, 1 to 50% by weight of a solid catalyst selected from heteropolyacids is dissolved by stirring at room temperature using 99 to 50% by weight of one or two or more mixed solvents selected from distilled water, ethanol, methanol, and the like as a solvent to prepare a supported catalyst. Can be used for

Metal oxides used as carriers in the heteropolyacid supported catalysts of the present invention include zirconium oxide (ZrO ₂ ), magnesium oxide (MgO), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ) and aluminum At least one selected from the group consisting of oxides (Al ₂ O ₃ ) is preferred. In particular, in the present invention, even when using two or more kinds of complex oxides in the oxide, the composition ratio is not limited.

In addition, the heteropoly acid-carrying catalyst of the present invention may be prepared by a method in which a heteropoly acid and a metal precursor are reacted in a solution state and co-precipitated, followed by heat treatment. That is, precursors of metal oxides such as zirconyl chloride (ZrOCl ₂ ), magnesium nitrate (Mg (NO ₃ ) ₃ ), titanium isopropoxide (Ti (OCH (CH ₃ ) ₂ ) ₄ ) and One or two or more precursors selected from cerium nitrate (Ce (NO ₃ ) ₃ ) are dissolved in one selected from a solvent such as distilled water, ethanol or methanol, and stirred for 10 to 30 minutes to form a hydroxide form. A metal salt is obtained, and a heteropolyacid / metal oxide supported catalyst is prepared by adding a solution in which the heteropolyacid is dispersed and heat treatment at 100 ° C to 400 ° C. At this time, even in the case of a composite oxide composed of two or more kinds of precursors among the selected metal oxide precursors, the composition ratio is not particularly limited.

In the present invention, dimethyl carbonate was synthesized from the environmentally friendly methanol and carbon dioxide using the catalyst prepared as described above, and the supported catalysts were compared with each other under the same reaction conditions as those of the metal oxide catalyst without heteropoly acid. . A batch high pressure reactor was used for the reaction, and the reaction was performed for 5 to 12 hours at a temperature of 100 ° C. to 300 ° C. and a carbon dioxide pressure of 10 to 60 atmospheres.

Hereinafter, the present invention will be described in more detail with reference to examples which are specific embodiments of the present invention.

(Produce) Example  1-1 (using metal precursors On zirconium oxide Supported  12- Tungstoic acid  Supported catalyst production)

A predetermined amount of 12- tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) was heat-treated at 300 ^° C to remove the crystal water, 0.6 grams was taken and dissolved in 3 cc of methanol. The homogeneous solution thus produced was left at room temperature for about 30 minutes. On the other hand, 4.83 g of zirconyl chloride was dissolved in 30 cc of distilled water and hydrated for about 30 minutes. The 12-tungstophosphoric acid solution was added to the zirconyl chloride solution, dispersed together, precipitated with ammonia water, and stirred with a magnetic stirrer for 1 hour. After stirring, the precipitate was filtered and washed with a vacuum filter, dried at room temperature for 20 hours, and further dried at 100 ° C. for 24 hours. A 12-tungstophosphoric acid catalyst supported on zirconium oxide was prepared by pulverizing the completely dried sample and heat treatment at 300 ° C.

12- tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) is selected as the heteropolyacid catalyst, zirconium oxide is selected as the metal oxide carrier, and finally infrared rays are examined to examine the characteristics of the supported catalyst prepared by heat treatment at 300 ° C. Spectroscopic analysis (IR) was performed. The results are summarized in Table 1 below. As can be seen in Table 1, the characteristic four bond frequencies of heteropolyacids are lower for the 12-tungstoic acid supported on zirconium oxide, compared to the unsupported pure 12-tungstoic acid catalyst. Appeared in. This means that 12- tungstophosphoric acid is strongly bonded to zirconium oxide as a metal oxide.

(Produce) Example  1-2 (using metal precursors On zirconium oxide Supported  Preparation of 12-tungstoic acid supported catalyst)

A 12-tungstophosphate catalyst supported on zirconium oxide in the same manner as in Example 1-1, except that the amount of ₁₂ -tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) was half (0.3 g). Was prepared. The amount of the 12- tungstophosphoric acid catalyst supported on zirconium oxide in the prepared catalyst is 10% by weight.

(Produce) Example  2 (Magnesium using metal precursors In oxide Supported  12- Tungstosilic acid  catalyst)

A predetermined amount of 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ) was heat-treated at 300 ^° C. to remove crystal water, and 0.6 grams was taken and dissolved in 3 cc of methanol. The homogeneous solution thus produced was left at room temperature for about 30 minutes. 3.85 g of magnesium nitrate was dissolved in 30 cc of distilled water, and hydrated for 30 minutes. The 12-tungstosilic acid solution was added thereto, dispersed together, precipitated with sodium hydroxide solution, and stirred with a magnetic stirrer for 1 hour. After stirring, the precipitate was filtered and washed with a vacuum filter, dried at room temperature for 24 hours, and further dried at 100 ° C. for 24 hours. The fully dried sample was pulverized and then heat-treated at 300 ° C. to prepare a 12-tungstosilic acid catalyst supported by 20% by weight in magnesium oxide.

(Produce) Example  3 (CE Oxide -titanium Oxide  On composite oxides Supported  12- Tungstosilic acid  catalyst)

A predetermined amount of 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ) was heat-treated at 300 ^° C. to remove crystal water, and then 0.6 grams of the resultant was dissolved in 3 cc of distilled water. The homogeneous solution thus produced was left at room temperature for 30 minutes. 3.47 g of cerium nitrate and 2.27 g of titanium isopropoxide dissolved in 30 cc of ethanol were prepared in a 1: 1 molar ratio. The 12-tungstosilic acid solution was added thereto, dispersed together, and precipitated with ammonia water. Stir with a magnetic stirrer for minutes to 1 hour. After stirring, the precipitate was filtered and washed with a vacuum filter, dried at room temperature for 24 hours, and further dried at 100 ° C. for 24 hours. A 12-tungstosilic acid catalyst supported on a cerium oxide-titanium oxide composite oxide was prepared by pulverizing a completely dried sample and heat-treating at 300 ° C.

(Produce) Example  4 (zirconium In oxide Supported  12- Tungstoic acid  Catalyst production)

A predetermined amount of 12- tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) was heat-treated at 300 ^° C to remove the crystal water, 0.6 grams taken and dissolved in 1.5cc of methanol. The homogeneous solution thus produced was left at room temperature for about 30 minutes. 1.0 g of a commercially available zirconium oxide powder (Aldrich, 99.99%) was added to the 12-tungstophosphoric acid solution and dried at 100 ° C. for 24 hours. A 12-tungstophosphoric acid catalyst supported on zirconium oxide was prepared by pulverizing the completely dried sample and heat treatment at 300 ° C.

(use) Example  One( Dimethyl carbonate  Manufacturing reaction)

Dimethyl carbonate was prepared by using a 12-tungstoic acid / zirconium oxide catalyst carrying 20% by weight and 10% by weight of 12-tungstophosphoric acid, prepared in Examples 1-1 and 1-2, respectively. . Dimethyl carbonate production was carried out in a batch high pressure reactor. For reaction, 0.5 g of a solid supported catalyst was added to 200 m-mole of methanol and purged with carbon dioxide to convert the inside of the high pressure reactor into a carbon dioxide atmosphere, and then pressurized to about 10 atm. After the reaction temperature was raised to 170 ℃ and pressurized carbon dioxide to 50 atm and the reaction was carried out at 400rpm.

 The catalytic activity of the dimethyl carbonate production of these catalysts was measured and summarized in Table 2 below.

Reaction temperature = 170 ^o C, reaction time = 8 hours, carbon dioxide pressure = 50 atmospheres, methanol = 200 m-mole

As can be seen in Table 2, the heteropoly acid-carrying catalyst of the present invention can be seen that the activity of about 3 to 7 times higher than the general metal oxide. As shown in Table 2, the 12-tungstophosphoric acid catalyst supported on zirconium oxide showed higher dimethyl carbonate productivity than pure zirconium oxide. In particular, the catalyst supported by 20% by weight of 12- tungstophosphoric acid showed higher catalytic activity than the catalyst supported by 10% by weight of 12-tungstoic acid. This is because the conversion of methanol to the methyl group was activated by the Bronsted acid point of 12- tungstophosphoric acid, which increased the reactivity.

(use) Example  2 (According to the catalyst production method Dimethyl carbonate  Manufacturing reaction)

12-tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) was selected as a heteropolyacid catalyst, and each 20 wt% supported 12-tung prepared by the preparation methods of (Preparation) Example 1 and (Preparation) Example 4, respectively. Styroic acid / zirconium oxide catalysts were prepared. Dimethyl carbonate production was carried out in a batch high pressure reactor. For the reaction, 0.5 g of a solid supported catalyst was added to 200 m-mole of methanol and purged with carbon dioxide to convert the inside of the high pressure reactor into a carbon dioxide atmosphere, and then pressurized to about 10 atm. After the reaction temperature was raised to 170 ℃ and pressurized carbon dioxide to 50 atm and the reaction was carried out at 400rpm. The catalytic activity of the dimethyl carbonate production of these catalysts is shown in Table 3 below. As shown in Table 3 below, the activity of the supported catalyst prepared by Production Example 1 (preparation using a metal precursor) was greater than that of the supported catalyst prepared according to Preparation Example 4 (preparation using a metal oxide). Appeared. This is because when the supported catalyst is prepared by coprecipitation as in Example 1, 12-tungstoic acid has a stronger interaction with the surface of the zirconium oxide to better provide Bronsted acid point.

Reaction temperature = 170 ^o C, reaction time = 8 hours, carbon dioxide pressure = 50 atmospheres, methanol = 200 m-mole

(use) Example  3 ( Dimethyl carbonate  Manufacturing reaction)

12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ) is selected as a heteropoly acid catalyst, By the preparation method of Preparation Example 2 and the preparation method of Preparation Example 3, 12- tungstosilic acid catalyst supported by 20% by weight in magnesium oxide and 12-tungstosilicon supported by 20% by weight in cerium oxide-titanium oxide composite oxide Acid catalysts were prepared. Dimethyl carbonate production was carried out in a batch high pressure reactor. For the reaction, 0.6 g of a supported catalyst in a solid phase was added to 200 m-mole of methanol and purged with carbon dioxide to convert the inside of the high pressure reactor into a carbon dioxide atmosphere and pressurized to about 10 atm. After the reaction temperature was raised to 110 ℃ and pressurized carbon dioxide to 40 atm and the reaction was carried out at 400rpm. The catalytic activity of the dimethyl carbonate production of these catalysts is shown in Table 4 below. As shown in Table 4, the activity of the 12- tungstosilonic acid catalyst (Preparation Example 3) supported on the cerium oxide-titanium oxide composite oxide rather than the 12- tungstosilic acid catalyst supported on the magnesium oxide (Preparation Example 2) It was found to be superior to this. This is because the acid point of 12- tungstosilonic acid acted more efficiently by the interaction of the composite metal oxide.

Reaction temperature = 110 ^o C, reaction time = 8 hours, carbon dioxide pressure = 40 atmospheres, methanol = 200 m-mole

As described above, the catalyst prepared by supporting heteropolyacid on a metal oxide has an advantage of exhibiting better reactivity with a metal oxide catalyst not supporting heteropolyacid in a reaction for directly synthesizing dimethyl carbonate from methanol and carbon dioxide.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

Claims (6)

delete delete delete delete delete Used to make dimethyl carbonate from methanol and carbon dioxide, 12- tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ), 12-molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ), 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ) and 12-molybdate One or more heteropolyacids selected from the group consisting of stalk acid (H ₃ PMo _12-x W _x O ₄₀ , x = 0-12) may include magnesium oxide (MgO), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), A heteropolyacid supported catalyst supported on at least two metal oxide carriers selected from the group consisting of silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ).