KR100966141B1 - Catalyst and process for preparing carboxylic acid esters - Google Patents

Abstract

The present invention discloses a process for preparing carboxylic esters from aldehydes and alcohols in the presence of molecular oxygen and catalysts for the same. This catalyst comprises a metal supported on a silica-containing support, which metal is basically composed of at least one of palladium, lead, an alkali metal or an alkaline earth metal and niobium and zirconium. The process for preparing carboxylic esters comprises reacting an aldehyde with an alcohol in the presence of molecular oxygen and the catalyst described above.

Description

Catalyst for preparing carboxylic acid ester and preparation method {CATALYST AND PROCESS FOR PREPARING CARBOXYLIC ACID ESTERS}

The present invention relates to a catalyst for the production of carboxylic acid esters, and more particularly, to a catalyst for producing a carboxylic acid ester from a one-step reaction of an aldehyde and an alcohol and a production method using the catalyst.

One known method of preparing carboxylic acid esters from aldehydes comprises first oxidizing an aldehyde to produce a carboxylic acid, and then reacting the carboxylic acid with an alcohol. However, this method involves a two-step reaction (oxidation reaction and esterification reaction), so that the equivalent amount of starting material must be large. This method also has a problem in that the yield of the carboxylic acid ester obtained due to poor performance of the catalyst used in the reaction is insufficient.

A number of methods have been disclosed for preparing high yields of carboxylic acids via single-phase liquid phase reaction of aldehydes with alcohols in the presence of certain catalysts. For example, JP-B-57-35856 proposes a Pd and Pb based catalyst using calcium carbonate as a carrier, JP-B-4-72578 proposes a Pb based catalyst using zinc oxide as a carrier, JP-A-57-50545 and JP-A-61-243044 propose various types of Pd / Pb catalysts, JP-B-61-60820 proposes Pd / Bi catalysts, and JP-B-62 -7902 and JP-A-5-148184 propose a catalyst composed of one or more elements selected from Pd, Pb and Bi, and JP-B-57-35860 proposes a Pd / Tl / Hg based catalyst.

However, the process for preparing carboxylic acid esters using the catalysts described above is accompanied by low reaction rates and undesirable byproducts.

Therefore, further process improvements are required in the preparation of carboxylic acid esters from aldehydes and alcohols.

The present invention provides a catalyst that catalyzes the reaction in forming carboxylic acid esters from aldehydes and alcohols in the presence of molecular oxygen. This catalyst comprises a metal supported on a silica-containing support, which metal includes palladium, lead, an alkali metal or an alkaline earth metal and at least one of niobium and zirconium.

The present invention also provides a process for preparing carboxylic acid esters. This method involves reacting aldehydes and alcohols in the presence of molecular oxygen and the catalysts described above.

More specifically, the process uses a catalyst comprising a metal supported on a silica-containing support to produce carboxylic acid esters from aldehydes and alcohols in the presence of molecular oxygen, the metal being essentially Palladium, lead, alkali metal or alkaline earth metal, and one or more of niobium and zirconium.

Hereinafter, the specific example of the catalyst for manufacturing carboxylic acid ester of this invention is described.

The support used for the catalyst is an oxide. Preferably, the support is basically a silica-containing support containing silica, for example, a silica support, an alumina-silica support (including a high content silica-alumina support and a low content silica-alumina support). , Silica-alumina-magnesia carrier, crystalline aluminosilicate carrier, zeolite, or mixtures thereof, and silica silica such as silica gel caract (CARIACT) commercially available from Fuji Silysia Chemical Ltd. -The carrier can be obtained commercially. Silica is regarded not only as a support but also as a catalyst component.

The metal supported on the support may include palladium, lead, alkali metal or alkaline earth metal, and one or more of niobium and zirconium, and are formed by depositing their metal and / or metal compound on the support.

The palladium compound on the support can be converted to palladium metal by a reduction reaction using an organic reducing agent such as formaldehyde, formic acid, hydrazine, methanol or a mixture thereof. The palladium compound on the support can also be converted to palladium metal by a reduction reaction with a reducing gas such as dilute or undiluted hydrogen.

In addition, the catalyst can be prepared by the following method.

First, at least one of the niobium compound and the zirconium compound is dissolved in water, and the silica-containing carrier is added and immersed in the resulting solution. The mixture is then dried under reduced pressure and calcined at 300 ° C. or higher, preferably 300-800 ° C. to obtain Nb- and / or Zr-modified silica-containing supports. Examples of niobium compounds usable in the present invention include niobium acetate, niobium carbonate, niobium chloride, niobium citrate, niobium nitrate, niobium oxalate, niobium sulfate, niobium tartarate and the like. Examples of zirconium compounds usable in the present invention include zirconium acetate, zirconium carbonate, zirconium chloride, zirconium citrate, zirconium oxynitrate, zirconium oxalate, zirconium sulfate, zirconium tartarate and the like.

The lead compound and alkali metal or alkaline earth metal compound are then dissolved in water and the resulting solution is added and immersed with Nb and / or Zr-modified silica-containing supports. The mixture is then dried under reduced pressure and calcined at 300 ° C. or higher, preferably 300-800 ° C. to form Nb and / or Zr / Pb / alkali metal or alkaline earth metal modified silica-containing supports. Examples of the lead compound usable in the present invention include lead acetate, lead carbonate, lead chloride, lead citrate, lead nitrate, lead oxalate, lead sulfate, lead tartarate or a mixture thereof. Among them, lead acetate and lead nitrate are preferred because of their high solubility. Alkali metal or alkaline earth metal compounds usable in the present invention include organic or inorganic salts, oxides or hydroxides of alkali metals or alkaline earth metals such as sodium, potassium, magnesium or calcium. Soluble compounds of alkali metals or alkaline earth metals, for example, acetates, carbonates, chlorides, citrates, hydroxides, nitrates, oxalates, sulfates, tartarates, or mixtures thereof of sodium, potassium, magnesium or calcium are alkali It can be used more preferably as a component of a metal or alkaline earth metal compound.

Finally, the palladium compound is dissolved in water to form a solution, to which Nb and / or Zr / Pb / alkali metal or alkaline earth metal modified silica-containing supports are added and immersed to form a suspension. This suspension is concentrated to form a mixture. The mixture is then depressurized and filtered and the cake obtained is washed with water and dried to give Nb and / or Zr / Pd / Pb / alkali metal or alkaline earth metal / SiO ₂ catalyst.

The palladium component in the catalyst is present in an amount of 1-15 parts by weight, preferably 3-12 parts by weight, based on 100 parts by weight of the silica-containing support. The lead component in the catalyst is also present in an amount of 1-15 parts by weight, preferably 3-12 parts by weight, relative to 100 parts by weight of the silica-containing support. The alkali metal or alkaline earth metal in the catalyst is present in an amount of 0.1-10 parts by weight, preferably 0.3-6 parts by weight, relative to 100 parts by weight of the silica-containing support. At least one of niobium and zirconium is present in an amount of 0.1-15 parts by weight, preferably 0.5-12 parts by weight, relative to 100 parts by weight of the silica-containing support.

Also described are methods for producing carboxylic acid esters using the catalysts described above.

The method includes reacting an aldehyde with an alcohol in the presence of molecular oxygen and a catalyst.

Aldehydes that serve as starting materials include saturated aldehydes, unsaturated aldehydes, aromatic aldehydes or mixtures thereof, acetaldehyde, propionaldehyde, isobutyl aldehyde, acrolein, methacrolein, crotonaldehyde, p-tolualdehyde, Benzaldehyde or mixtures thereof and the like. Of the aldehydes mentioned above, methacrolein, acrolein and mixtures thereof are more important because they can serve as raw materials in the production of methacrylic esters and acrylic esters of high industrial value.

Alcohols that serve as another starting material include methanol, ethanol, isopropanol, allyl alcohol, metalyl alcohol or mixtures thereof. Of the alcohols listed, methanol is more important because it can serve as a raw material in the production of industrially valuable methyl acrylate and methyl methacrylate (MMA).

The molar ratio between aldehyde and alcohol is 1: 100 to 1: 1, preferably 1:10 to 2: 3.

Oxygen, air or oxygen-enriched air can serve as a source of molecular oxygen, usually supplied by blow blowing to the reaction solution. Hydrogen peroxide can also be present as an oxidizing agent in the reaction solution.

The process can be carried out at a temperature range of 20-110 ° C., preferably 50-100 ° C. The method can be carried out under high pressure, atmospheric pressure or reduced pressure. Polymerization inhibitors such as hydroquinone, methyl ethyl hydroquinone, or p-methoxyphenol can optionally be added to the reaction solution. It should also be noted that the reaction of aldehydes with alcohol can be carried out continuously, semi-continuously or batch wise. In addition, the above-described reaction can be carried out with or without continuous wastewater treatment.

In general, the catalyst used in the process gradually decreases in activity with time. The yield of the carboxylic acid ester produced is greatly reduced when the catalyst is used repeatedly in a batch reaction or for a long time in a continuous reaction. In consideration of the result that the catalyst activity decreases due to the loss of lead in the reaction, an appropriate amount of lead may be further added to the reaction solution.

The following examples are intended to illustrate in more detail without limiting the scope of the present invention, it will be understood by those skilled in the art that various modifications and changes can be made.

Unless indicated otherwise, all ratios and percentages for liquids and solids are by weight and in molar percentages for gas compositions, flow rates are typically cubic meters per hour (m ³ ), for example, at 0 ° C. and 760 mmHg. Represented by In addition, in the art, the ratio of reaction methacrolein to MMA is generally expressed as a selectivity percentage.

For the sake of understanding, the nature and source of the reagents used in the examples and comparative examples of the present invention are described as follows.

Niobium oxalate: Nb ₂ (OOC-COO) ₅ , manufactured by NOAH.

Zirconium oxynitrate: ZrO (NO ₃ ) ₂ ㆍ 2H ₂ O, manufactured by SHOWA, 99% purity.

Lead acetate: Pb (CH ₃ COO) ₂ 3H ₂ O, manufactured by Showa Corporation, 99.5% purity.

Magnesium Acetate: Mg (CH ₃ COO) ₂ 4H ₂ O, from Showa, 98% purity.

PdCl ₂ : manufactured by ISHIFUKU, 99% purity.

Deionized water.

Silica Carrier: Fuji Silysia Cariact Q-10, particle size 62-105 #.

Catalyst manufacturing method

Example 1

Nb-Modified Oxyesterification Catalyst

11.08 g niobium oxalate was added to 170 g deionized water. After dissolution, 50 g of the silica carrier was added to the above solution to form a mixture 1A. This mixture (1A) was dried under reduced pressure and calcined to obtain an Nb-modified silica carrier.

4.33 g of lead acetate and 8.28 g of magnesium acetate were added to 141 g of deionized water. After dissolution, 47.43 g of the Nb-modified silica carrier was added to the solution to form a mixture 1B. This mixture (1B) was dried under reduced pressure and calcined to obtain an Nb / Pb / Mg-modified silica carrier.

4.16 g PdCl ₂ was added to 199.4 g deionized water. After dissolution, 49.85 g of the Nb / Pb / Mg-modified silica carrier was added to the above solution to obtain a suspension, and the suspension was concentrated to form a dark brown mixture (1C). The mixture (1C) was again depressurized and filtered to wash the cake obtained with deionized water and then dried to obtain a black catalyst (A) containing Pd / Pb / Nb / Mg supported on a silica carrier.

The catalyst (A) contained 5 wt% Pd, 5 wt% Pb, 6.58 wt% Nb, and 2 wt% Mg based on the 100 wt% silica carrier.

Example 2

Zr-Modified Oxyesterification Catalyst

18.99 g zirconium oxynitrate was added to 350 g deionized water. After dissolution, 100 g of the silica carrier was added to the above solution to form a mixture 2A. This mixture (2A) was dried under reduced pressure and calcined to obtain a Zr-modified silica carrier.

8.07 g of lead acetate and 15.52 g of magnesium acetate were added to 363.4 g of deionized water. After dissolution, 87.71 g of the Zr-modified silica carrier described above was added to the solution to form a mixture 2B. This mixture (2B) was dried under reduced pressure and calcined to obtain a Zr / Pb / Mg-modified silica carrier.

7.93 g of PdCl ₂ was added to 382.3 g of deionized water. After dissolution, 105.96 g of the Zr / Pb / Mg-modified silica carrier was added to the above solution to obtain a suspension, and the suspension was concentrated to form a dark brown mixture (2C). The mixture (2C) was again depressurized and filtered to wash the cake obtained with deionized water and then dried to obtain a black catalyst (B) containing Pd / Pb / Zr / Mg supported on a silica carrier.

The catalyst (B) contained 5 wt% Pd, 5 wt% Pb, 6.45 wt% Zr, and 2 wt% Mg based on the 100 wt% silica carrier.

Comparative Example 1

4.80 g of lead acetate and 9.17 g of magnesium acetate were added to 156.4 g of deionized water. After dissolution, 55.15 g of the silica carrier was added to the above solution to form a mixture 3A. This mixture (3A) was dried under reduced pressure and calcined to obtain a Pb / Mg-modified silica carrier.

4.57 g PdCl ₂ was added to 220.4 g deionized water. After dissolution, 55.1 g of the above-described Pb / Mg-modified silica carrier was added to the above solution to obtain a suspension, and the suspension was concentrated to form a dark brown mixture (3B). The mixture (3B) was again depressurized and filtered to wash the cake obtained with deionized water and then dried to obtain a catalyst (C) containing Pd / Pb / Mg supported on a silica carrier.

The catalyst (C) contained 5 wt% Pd, 5 wt% Pb, and 2 wt% Mg based on the 100 wt% silica carrier.

Method for preparing carboxylic ester

Example 3

The catalyst (A) of Example 1 was tested under autoclave equipped with a stirrer at 80 ° C. and a pressure of 5 Kg / cm ² .

Methacrolein (TCI reagent grade, manufactured by Tokyo Kasei Co., Ltd.), methanol (manufactured by Merck, 99.5% purity) and air were mixed to serve as a reaction solution containing 30% methacrolein dissolved in methanol. In addition, lead acetate (Showa Co., Ltd., 99.5% purity) was added to the reaction solution as catalyst stabilizer. The exhaust oxygen content was adjusted to 2-4%. The molar ratio of aldehyde and alcohol in the reaction solution was 7: 3 and the Pb concentration of the reaction solution was 60 ppm.

When the reaction solution reacted with 20.5 g of catalyst (A) under the flow of introduced air, the reaction pressure rose to ⁵ Kg / cm ² and the temperature rose to 80 ° C.

After the reaction solution was further fed, the feed flow was increased to 40 ml / h. Liquid products were collected hourly and analyzed by GC and gaseous products were analyzed by online GC.

The above reaction was carried out in a continuous stirred tank type reactor system, and the methacrolein conversion, methyl methacrylate selectivity, and yield after 10 hours of operation are shown in Table 1.

Example 4

Example 4 was carried out in the same manner as in Example 3, except that Catalyst (A) was replaced with Catalyst (B). Table 1 shows methacrolein conversion, methyl methacrylate selectivity and yield after 10 hours of operation.

Comparative Example 2

Comparative Example 2 was carried out in the same manner as in Example 3, except that Catalyst (A) was replaced with Catalyst (C). Table 1 shows methacrolein conversion, methyl methacrylate selectivity and yield after 10 hours of operation.

Example 5

Example 5 was carried out in the same manner as in Example 4 except for continuous drainage treatment during the reaction. Table 1 shows methacrolein conversion, methyl methacrylate selectivity and yield after 50 hours of operation.

Oxyesterification of Methacrolein with Methanol Example catalyst % Of catalyst Methacrolein Conversion Rate (%) Selectivity (%) Yield (%) Nb Zr Pd Pb Mg SiO ₂ Example 3 Catalyst A 6.58 5 5 2 100 67.0 68.4 45.8 Example 4 Catalyst B 6.45 5 5 2 100 67.5 67.2 45.4 Comparative Example 2 Catalyst C 5 5 2 100 58.3 58.7 34.2 Example 5 Catalyst B 6.45 5 5 2 100 72.5 92.8 67.3

Example 6

Example 6 used ethanol (99.5% purity, manufactured by Nihon Shigaku Industries, Inc.) instead of methanol, except that the feed solution contained 15% methacrolein dissolved in ethanol instead of 30% methacrolein dissolved in methanol. And the same method as in Example 4. Methacrolein conversion, ethyl methacrylate selectivity and yield after 10 hours of operation are shown in Table 2.

Comparative Example 3

Comparative Example 3 was carried out in the same manner as in Example 6 except that Catalyst (B) was replaced with Catalyst (C). Methacrolein conversion, ethyl methacrylate selectivity and yield after 10 hours of operation are shown in Table 2.

Oxyesterification of Methacrolein Using Ethanol Example catalyst Component of catalyst (wt%) Methacrolein Conversion Rate (%) Selectivity (%) Yield (%) Nb Zr Pd Pb Mg SiO ₂ Example 6 Catalyst B 6.45 5 5 2 100 42.9 68.6 29.4 Comparative Example 3 Catalyst C 5 5 2 100 35.3 69.8 24.6

Although the present invention has been described with reference to preferred specific examples and examples, the present invention is not limited thereto. Accordingly, the appended claims should be construed as including all possible modifications and changes within the spirit and scope of the present invention.

As described above, the present invention provides a catalyst for promoting the reaction in forming a carboxylic acid ester from an aldehyde and an alcohol in the presence of molecular oxygen. Also provided is a method of preparing a carboxylic acid ester comprising reacting an aldehyde and an alcohol in the presence of molecular oxygen and the catalyst described above.

Claims (25)

A catalyst for promoting a reaction in forming a carboxylic ester from an aldehyde and an alcohol in the presence of molecular oxygen, comprising a metal supported on a silica-containing support, the metal being palladium, lead, an alkali metal or an alkali A catalyst comprising earth metal and niobium, wherein the niobium is present in an amount of 6.58 to 15 parts by weight relative to 100 parts by weight of the silica-containing support. The method of claim 1, Wherein each of the palladium and lead elements is present in an amount of 1 to 15 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 1, And the alkali metal or alkaline earth metal is present in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the silica-containing support. delete The method of claim 1, And each of the palladium and lead elements is present in an amount of 3 to 12 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 1, The alkali metal or alkaline earth metal is present in an amount of 0.3 to 6 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 1, The niobium is present in an amount of 6.58 to 12 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 1, The catalyst is characterized in that the alkali metal or alkaline earth metal is magnesium. delete delete In the method for producing a carboxylic acid ester comprising reacting an alcohol with an aldehyde in the presence of a molecular oxygen and a catalyst comprising a metal supported on a silica-containing support, the metal is palladium, lead, an alkali metal or Alkaline earth metal and niobium, wherein the niobium is present in an amount of 6.58 to 15 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 11, The aldehyde comprises a saturated aldehyde, unsaturated aldehyde, aromatic aldehyde or a mixture thereof. The method of claim 11, The aldehyde is a method comprising the acetaldehyde, propionaldehyde, isobutyl aldehyde, methacrolein, crotonaldehyde (crotonaldehyde), p-tolualdehyde, benzaldehyde or mixtures thereof. The method of claim 11, The alcohol is a production method characterized in that it comprises methanol, ethanol, isopropanol, allyl alcohol, metallyl alcohol or mixtures thereof. The method of claim 11, The molar ratio of the aldehyde and alcohol is 1: 100 to 1: 1 characterized in that the manufacturing method. The method of claim 11, The molar ratio of the aldehyde and alcohol is characterized in that 1:10 to 2: 3. The method of claim 11, Wherein each of the palladium and lead elements is present in an amount of 1 to 15 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 11, Wherein the alkali metal or alkaline earth metal is present in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the silica-containing support. delete The method of claim 11, Wherein each of the palladium and lead elements is present in an amount of 3 to 12 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 11, The alkali metal or alkaline earth metal is present in an amount of 0.3 to 6 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 11, And niobium is present in an amount of 6.58 to 12 parts by weight based on 100 parts by weight of the silica-containing support. The method of claim 11, The alkali metal or alkaline earth metal is a manufacturing method characterized in that the magnesium. delete delete