JPH03232835A - Production of glyoxal - Google Patents

Abstract

PURPOSE:To obtain the subject compound having high quality in high yield at a low cost by contacting a gas containing ethylene glycol and molecular oxygen with a granular silver catalyst supported on silicon carbide in the presence of phosphorus or a phosphorus compound at a high temperature, thereby effecting vapor-phase oxidation reaction. CONSTITUTION:In the production of glyoxal useful as a main raw material for textile processing agent, paper processing agent or soil hardener and an intermediate for organic synthesis by the vapor-phase oxidation of ethylene glycol, the oxidation is carried out by contacting a gas containing ethylene glycol and molecular oxygen with granular silver catalyst supported on silicon carbide particles in the presence of phosphorus or a phosphorus compound preferably at 450-650 deg.C. The objective compound having excellent quality can be produced from inexpensive raw material in high selectivity and high productivity per unit of expensive silver catalyst on an industrial scale at a low cost while suppressing the by-production of glycol aldehyde.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a gas phase oxidation reaction of ethylene glycol, and more specifically, the present invention relates to a gas phase oxidation reaction of ethylene glycol, and more specifically, ethylene glycol is mixed with granular silver of a specific particle size in the presence of a predetermined amount of phosphorus or a phosphorus compound. This is a gas phase oxidation method to obtain glyoxal in high yield through contact.

[Prior art]

There are various proposals regarding methods for producing glyoxal by oxidizing ethylene glycol. For example, a method of oxidizing with oxygen using an oxidation catalyst consisting of copper and/or silver and phosphorus (Japanese Patent Publication No. 48-1364), ethylene in the presence of a catalyst containing phosphorus and copper, phosphorus and silver, or phosphorus, copper and silver. There is an oxidation method (JP-A-52-17408) in which a bromine compound is mixed into the raw material gas mixture in an amount that does not reduce the conversion rate of glycol to about 90% or less. Also, a method using a catalyst containing copper (U.S. Pat. No. 2,339,282)
, a method of oxidizing a copper-containing catalyst using a CuCu-3i alloy in the coexistence of a halogen compound has been proposed.

However, methods using these alloy catalysts have not been very advantageous industrially because it is difficult to prepare the catalysts, the lifetime of maintaining high reaction performance is short, and the regeneration treatment of the catalysts is complicated.

Furthermore, as a method by oxidation of ethylene glycol,
A method in which oxidation is carried out in the presence of silver crystals of a certain particle size (0.1 to 2.5 mm) (Japanese Patent Application Laid-open No. 103809/1983), in the presence of a phosphorus compound that vaporizes under the reaction conditions using a copper-containing catalyst. A method in which oxidation is carried out (Japanese Unexamined Patent Publication No. 55-55129) has also been proposed.

[Problem to be solved by the invention]

However, the yield of glyoxal by these methods is not very high, and a considerable amount of reaction intermediate glycolaldehyde and other impurities are produced.

Glyoxal is a very useful compound as a main raw material for fiber processing agents, paper processing agents, soil hardening agents, and as an intermediate for other organic synthesis. However, especially when used as a textile processing agent or paper processing agent, if a large amount of glycolaldehyde is contained, the final product will be significantly colored and will have no commercial value.

Furthermore, removing glycolaldehyde produced as a by-product during glyoxal production by post-treatment is too costly and is not an economical method.

Therefore, these methods cannot compete with the industrially practiced method of oxidizing acetaldehyde with nitric acid. However, compared to the nitric acid oxidation method of acetaldehyde, the method for producing glyoxal using the gas-phase oxidation method of ethylene glycol is simpler and uses ethylene glycol, a derivative of ethylene oxide, as the raw material, which is made from natural gas, which is cheaper. Therefore, it is economically advantageous in this respect.

[Means to solve the problem]

Therefore, the present inventors conducted intensive studies to overcome the drawbacks of the conventional method for producing glyoxal by gas-phase oxidation of ethylene glycol. As a result, carbonized cane particles were added to the support layer in the presence of a trace amount of phosphorus or phosphorus compounds. It was discovered that the amount of glycolaldehyde by-product can be significantly reduced by bringing it into contact with silver particles, and glyoxal can be produced with high yield and excellent quality.
The present invention has now been completed.

That is, the method for producing glyoxal of the present invention involves contacting a gas containing ethylene glycol and molecular oxygen with a silver catalyst in the presence of phosphorus or a phosphorus compound in a method for producing glyoxal by gas-phase oxidation of ethylene glycol. The method is characterized in that cane carbide particles are used as a support layer for the catalyst in carrying out the oxidation.

The particle size of the silver particles used is usually 3III11 or 2mn+
The following degree is sufficient. Although it is possible to use particles larger than this, it is meaningless in fully demonstrating the spirit of the present invention.

What should be emphasized in the present invention is that the particle size of the silver particles that act as a catalyst is 0.1 mm or less, which makes it possible to use very fine particles that could not be used with conventional technology, so the specific surface area is extremely large. It is possible to achieve a very high working height per unit volume of catalyst.

Therefore, the height of the catalyst layer can be small. In the prior art, the thickness of this catalyst layer was several centimeters. For example, in the example in Japanese Patent Publication No. 6154011, silver crystals having a grain size of 0.1 to 2.5 mm are spread at a height of 30 ma+ and subjected to the reaction.

As a result of various studies in the process of arriving at the present invention, the inventors found that
Among the catalyst particles shown in the above example, silver particles having a relatively large particle size have almost no catalytic function, and are only effective as a support layer for the fine particle size particles that act as an active catalyst. Therefore, the size of the silver particles used is not particularly limited, but
It is preferable to use particles with as small a particle size as possible. By using particles with a small particle size, the catalyst activity can be improved, and as a result, the selectivity of glyoxal can be improved.

In this case, the thickness of the catalyst layer is sufficient to be 10 mm or less,
Preferably it is 5 to 10 mm. Although the catalytic activity is sufficiently improved even when the thickness is less than 5IIIn, it is very difficult to uniformly fill the catalyst packed bed of a large-diameter reactor with a thickness of less than 5IIIn.

In this regard, the present inventors focused on using particles of cane carbide (hereinafter abbreviated as SiC) as a support layer for a catalyst made of fine silver particles, thereby suppressing the production of glycolaldehyde and promoting the desired reaction. I was able to get the results. By using the SiC support layer in this way, even if there is some variation in the catalyst filling height of silver particles, the variation in ventilation resistance of each part on the surface of the catalyst packed layer is averaged out.

This becomes more effective as the reactor becomes larger. Furthermore, it is extremely important to use SiC as the material for this support layer. First, SiC is completely inert to this reaction, and second, SiC has high thermal conductivity as a ceramic. Due to these properties, SiC
can be used as an extremely excellent catalyst support layer in the present invention. As described above, the effect of using SiC is not only to simply support the silver particles, but also to reduce the residence time of gas from the outlet of the reaction layer to the quench zone. It has been found that glycolaldehyde, which is the main impurity mentioned above, is produced in the reaction part of the catalyst, but it is also produced by post-reactions between glyoxal molecules while the reaction gas leaves the reaction zone and is maintained at a high temperature. Therefore, filling SiC is very effective in reducing the residence time in the lower part of the catalyst layer. This SiC and supporting layer play such a role.

Alumina and the like, which are generally thought to be inert, are not inert at high temperatures such as in this reaction.

When α-alumina is used as the support layer, formalin,
The amount of produced co and co□ increases, and not only the yield of glyoxal decreases, but also the amount of glycolaldehyde produced increases extremely. Although the mechanism is not clear, the reaction solution is colored slightly yellow. Also, other ceramics with high thermal conductivity, such as nitrides, cannot chemically withstand the reaction environment of high temperature and oxidizing atmosphere.

The SiC used in the present invention may be any SiC that is generally used for catalyst carriers, etc., and is not particularly specified. Table 1 shows examples of commercially available products used in the present invention.

In addition, a sintered body of high-purity SiC powder generally used for fine ceramic sintered bodies may be appropriately crushed and used.

Next, the particle size of the SiC to be used as the support layer is determined in order from one that can support the fine-sized silver particles used for the catalyst and that has a particle size slightly larger than the silver particle to one with a particle size of several micrometers. All you have to do is stack the particles in a way that supports them. Specifically, it is preferable to use a material with a thickness of about 0.1 mm to 3ffII11. The total thickness of the support layer is suitably between 10 and 30 mm. However, it is not necessary to unnecessarily increase the thickness of the support layer. These support layers are usually stacked on a special mesh of a vertically arranged reactor or a support surface with gas flow holes, and the top of the support layer is filled with fine-grained silver catalyst, directing the raw material gas from the top to the bottom. A method is taken to allow it to flow down.

Next, as the powdered silver used for the catalyst, not only powdered silver obtained by electrolysis, but also chemically produced fine powdered silver, such as
It can be used regardless of its preparation method, such as those obtained by an alkaline precipitation method, or fine powders obtained by various heating methods in an inert gas, which is called gas evaporation in boat fishing.

In the present invention, phosphorus or a phosphorus compound may be mixed in advance with ethylene glycol in a predetermined amount before being subjected to the reaction, or may be added to the reaction system separately from ethylene glycol, either alone or as a solution. Examples of phosphorus compounds include inorganic phosphorus compounds such as ammonium orthophosphate, diammonium hydrogen phosphate, ammonium dihydrogen orthophosphate, and ammonium dihydrogen phosphite; primary to tertiary phosphines such as mono-, di-, or trimethylphosphine;
Examples of organic phosphorus compounds that can be effectively used include phosphorous acid esters such as methyl phosphite and ethyl phosphite, dimethyl methylphosphonate, and diethyl ethylphosphonate.

However, phosphorus compounds with high boiling points require the evaporator temperature to be particularly high, or these phosphorus compounds stay in the evaporator and decompose and accumulate, causing corrosion of equipment materials and iron rust that occurs. etc. may fly into the reaction layer and adversely affect the reaction, which is not preferable. Therefore, it is more preferable to use an organic phosphorus compound with a relatively low boiling point,
For example, methyl phosphite, ethyl phosphite, methyl phosphate, ethyl phosphate, etc. are used.

The amount of phosphorus or phosphorus compound added is suitably in the range of 0.1 to soppm in terms of phosphorus relative to ethylene glycol. By adding this phosphorus or phosphorus compound,
Compared to the case where these are not added, the production of oxidation products such as carbon oxide and carbon dioxide and decomposition products such as formaldehyde is significantly suppressed, and the yield of glyoxal, which is the target product, is significantly improved. In addition, when the addition of phosphorus or a phosphorus compound is temporarily interrupted in the method of the present invention, the production rate of carbon oxide, carbon dioxide, or formaldehyde immediately increases. This suggests that the added phosphorus or phosphorus compound acts effectively in the gas phase rather than accumulating and acting on the catalyst.

If the amount of phosphorus or phosphorus compound added is less than 0.1 ppm in terms of phosphorus relative to ethylene glycol, the effect obtained will be small and it is not practical. Further, if more than 50 ppm of phosphorus or a phosphorus compound is added in terms of phosphorus, various reaction-inhibiting effects will appear to the extent that the reaction cannot be maintained even in the presence of a powdered silver catalyst, which is not practical.

In the present invention, pure oxygen or air may be used as molecular oxygen, but the latter is economically advantageous.

1 Furthermore, in order to obtain glyoxal in high yield, ethylene glycol and molecular oxygen are diluted with an inert gas to carry out the reaction. As the inert gas, rare gases such as nitrogen, helium, and argon, carbon dioxide gas, or water vapor are used.

In the gas phase oxidation of the method of the present invention, the reaction temperature is 450 to 650°C.
is appropriate.

The reaction gas reacted as described above must be cooled as quickly as possible after leaving the catalyst layer. Excessive retention in the high temperature region will only lead to decomposition of unstable aldehydes.

The cooled gas undergoes partial condensation as necessary to recover unreacted ethylene glycol. If it does not contain unreacted ethylene glycol, or if there is a trace amount of ethylene glycol remaining that does not pose a problem for the product and there is no need to remove it, it is cooled and condensed in a heat exchanger and then subjected to normal absorption operations. Separates from gas phase components.

The glyoxal aqueous solution thus obtained contains organic acids and trace amounts of formaldehyde as impurities. This formaldehyde is easily removed by a conventional stripping operation using steam injection, during which time some of the low-boiling organic acids such as formic acid and acetic acid are also removed. Furthermore, an aqueous glyoxal solution obtained by oxidizing ethylene glycol using a powdered silver catalyst contains almost no glycolaldehyde, which is a reaction intermediate, compared to a solution synthesized without using a powdered silver catalyst. Furthermore, the amount of organic acid contained in the glyoxal aqueous solution subjected to the formaldehyde stripping treatment is an appropriate amount of acid necessary to maintain the stability of the product, so no further separation treatment is required. Therefore, it is sufficient to perform decolorization treatment and treatment with a cation exchange resin as necessary.

Thus, according to the method of the present invention, glyoxal can be produced from ethylene glycol in a high yield while suppressing the formation of by-products, and the stability of the gas phase oxidation reaction is also excellent. Therefore, the present invention is suitable as an industrial method for producing glyoxal.

Table 1 Note) Physical properties are determined by a method according to JIS, R-2205.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 5iC (manufactured by Fujimi Abrasives Industry Co., Ltd., TL-851) was crushed and classified and used as a catalyst support layer, and as a catalyst, 5iC (manufactured by Fujimi Abrasives Industry Co., Ltd., TL-851) with a particle size of 0.075 to 0.1 P obtained by electrolysis of an aqueous silver nitrate solution was used as a catalyst. Silver particles were used.

Each layer of SiC was stacked in the reactor as shown in Table 2, and the above-mentioned silver particles were stacked on the top layer. However, the SiC layer was covered with a 100 mesh copper net.

To this reactor, ethylene glycol was passed through an evaporator and a preheater at a rate of 140 g/Hr, water vapor at 140 g/■r, air at 262 Nl/Hr, and nitrogen at 54 ON1. /Hr
, and triethyl phosphite added in an amount of 5 ppm as phosphorus relative to ethylene glycol was supplied in a downward flow to cause a reaction at a reaction temperature of 585°C. After the reaction gas was cooled, the product was separated and collected in a water absorption tower.

As a result, the ethylene glycol conversion rate was 99.9χ, the glyoxal selectivity was 84.3χ, and the formalin selectivity was 2.4.
χ, glycolaldehyde selectivity was 0.05χ.

Moreover, the space-time yield for the silver catalyst was 113 g glyoxal/cl·catalyst volume·time.

Table 2 Comparative Example 1 Using the same reactor as in Example 1, a reaction was carried out in the same manner as in Example 1 except that the SiC portion was replaced with silver particles having the same particle size. The loading amount of silver particles is shown in Table 3.

The reaction results were as follows: ethylene glycol conversion rate: 99.9χ, glyoxal selectivity: 64.8χ, formalin selectivity: 6.
The 2χ glycoraldehyde selectivity was 0.43χ.

The space-time yield for the silver catalyst was 20.2 g-glyoxal/c1a·catalyst volume·time.

Table 3 Comparative Example 2 A reaction was carried out under the same conditions as in Example 1 without adding triethyl phosphite to the reactor. As a result, the ethylene glycol conversion rate was 100χ, the glyoxal selectivity was 38.6χ, the formalin selectivity was 11.2χ, and the glycolaldehyde selectivity was 0.05χ.

Comparative Example 3 6 Instead of SiC as a support layer, α-alumina (AL-873 manufactured by Fumi Abrasive Materials Co., Ltd.) was crushed and filled into a reactor with the same particle size distribution as in Example 1. The reaction was carried out under the following conditions. The results were ethylene glycol conversion rate of 99.1χ, glyoxal selectivity of 58.7χ, and formalin selectivity of 9.
3χ, and glycolaldehyde selectivity was 7.8χ.

However, a brown coloration was observed in the reaction solution.

Comparative Example 4 Only silver particles having a particle size of 0.075 to 0.1 mm were placed in a reactor on a 100-mesh copper mesh in the same manner as in Example 1, and a reaction was carried out under the same conditions as in Example 1. However, the reactions were carried out with two types of silver particle catalyst layer thicknesses of 5.0 mm and 15.0 mm.

The results are shown in Table 4. After the reaction was completed, the inside of the reactor was inspected and it was found that the copper mesh used as a catalyst had been poured into the mesh. Therefore, industrially it is impossible to use only such fine silver powder directly on the copper mesh. The catalyst layer thickness is 15.0m.
m, the pressure loss is 0.6 k, which is twice that of Example 1.
g/aft.

Example 2 An experiment was conducted under the same reaction conditions as in Example 1, except that the layer of silver particles of the catalyst had a thickness of 3n+m. As a result, the ethylene glycol conversion rate was 98.2χ, the glyoxal selectivity was 81.2χ, the formalin selectivity was 2.6χ, and the glycolaldehyde selectivity was 0.03χ. The space/time yield relative to the silver catalyst was 181 g-glyoxal/d/catalyst volume/time.

Table 4 GA: Glycolaldehyde Example 3 In the same catalyst layer as in Example 1, the reaction was carried out under the same conditions as in Example 1 except that the amount of phosphorus added was 3 ppm and the reaction temperature was 570°C.

The results were: ethylene glycol conversion rate 99.8'A, glyoxal selectivity 80.2χ, formalin selectivity 2.8χ
, the glycolaldehyde selectivity was 0.04χ.

The space/time yield for the silver catalyst was 108 g-glyoxal/cTIl/catalyst volume/time.

Example 4 The reaction was carried out in the same manner as in Example 1 except that silver particles were stacked on the catalyst layer up to the uppermost layer and the second SiC layer below it in Table 2 of Example 1.

As a result, the ethylene glycol conversion rate was 99.9%, the glyoxal selectivity was 8462%, and the formalin selectivity was 2.1.
%, glycolaldehyde 0.04%.

〔Effect of the invention〕

By the method of the present invention, glyoxal can be produced from inexpensive raw materials with good selectivity and at high productivity per expensive silver catalyst, making an extremely large contribution to industry.

Claims (1)

[Claims] In a method for producing glyoxal by gas-phase oxidation of ethylene glycol, oxidation is carried out by bringing a gas containing ethylene glycol and molecular oxygen into contact with a granular silver catalyst at high temperature in the coexistence of phosphorus or a phosphorus compound. A method for producing glyoxal, characterized in that silica carbide particles are used as a support layer for the catalyst.