JP2912443B2 - Glioxizal manufacturing method - Google Patents

Description

The present invention relates to a gas phase oxidation reaction of ethylene glycol,
More specifically, it is a vapor phase oxidation method in which ethylene glycol is brought into contact with granular silver having a specific particle size in the presence of a predetermined amount of phosphorus or a phosphorus compound to obtain glyoxal in high yield.

(Prior art)

There are various proposals for a method for producing glyoxal by oxidizing ethylene glycol. For example, copper and / or
Or a method of oxidizing with oxygen using an oxidation catalyst comprising silver and phosphorus (Japanese Patent Publication No. 48-1364), the conversion of ethylene glycol in the presence of a catalyst containing phosphorus and copper, phosphorus and silver or phosphorus, copper and silver (Japanese Patent Application Laid-Open No. 52-17408) is a method in which a bromine compound is mixed with a raw material gas in such an amount that the amount of bromine compound is not reduced to about 90% or less. Further, a method using a catalyst containing copper (U.S. Pat. No. 2,339,282), a method using a Cu-Si-Mn alloy to oxidize a copper-containing catalyst in the presence of a halogen-based compound, and the like have been proposed.

However, the method using these alloy-based catalysts is difficult to adjust the catalyst and has a short life span that can maintain high reaction results,
In addition, since the regeneration treatment of the catalyst is complicated, it is not an industrially advantageous method. Further, as a method of oxidizing ethylene glycol, a method of oxidizing in the presence of silver crystals having a fixed particle size (0.1 to 2.5 mm) (Japanese Patent Laid-Open No. 54809/1979).
), And a method of oxidizing in the presence of a phosphorus compound which vaporizes under reaction conditions using a copper-containing catalyst (JP-A-55-55129).

[Problems to be solved by the invention]

However, the yields of glyoxal themselves by these methods are not very high, and the reaction intermediate glycolaldehyde and other impurities are considerably produced.

Glyoxal is a very useful compound as a main raw material for fiber processing agents, paper processing agents, soil hardening agents, and other intermediates for organic synthesis. However, especially when used in a fiber processing agent or a paper processing agent, if the glycolaldehyde is contained in a large amount, the coloring of the final product is remarkable and the value as a commercial product is lost. Further, removing glycolaldehyde by-produced during the production of glyoxal by post-treatment is too costly and not an economical method.

Therefore, these methods were not methods that could compete with the industrially practiced nitric acid oxidation method of acetaldehyde. However, the method of producing glyoxal by vapor phase oxidation of ethylene glycol itself is simpler than the nitric acid oxidation method of acetaldehyde, and its process is simpler and cheaper. Therefore, in this respect, it is economically advantageous and advantageous.

[Means for solving the problem]

Thus, the present inventors have conducted intensive studies to overcome the disadvantages of the conventional method in a method for producing glyoxal by vapor-phase oxidation of ethylene glycol. As a result, in the presence of a trace amount of phosphorus or a phosphorus compound, the carbonized The present inventors have found that by contacting with silver particles, the by-product amount of glycolaldehyde can be remarkably reduced, and that glyoxal excellent in quality with high yield can be produced, and the present invention has been completed.

That is, in the method for producing glyoxal of the present invention, in a method for producing glyoxal by vapor-phase oxidation of ethylene glycol, a gas containing ethylene glycol and molecular oxygen is brought into contact with a silver catalyst in the presence of phosphorus or a phosphorus compound. In carrying out the oxidation, diatomaceous carbide particles are used as a support layer of the catalyst.

The particle size of the silver particles to be used may usually be about 3 mm or 2 mm or less. Although it is possible to use particles larger than that, it is meaningless in fully exerting the purpose of the present invention.

It should be emphasized in the present invention that the particle size of silver particles acting as a catalyst is 0.1 mm or less, and very fine particles that could not be used in the prior art can be used. The working height per volume can be very high.

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 of JP-B-61-54011, a silver crystal having a particle size of 0.1 to 2.5 mm is spread over a height of 30 mm and used for the reaction.

The present inventors have conducted various studies in the process leading to the present invention. As a result, among the catalyst particles shown in the above example, silver particles having a relatively large particle size have almost no action as a catalyst, and act as an active catalyst. It is only effective as a support layer for particles having a small particle size. Therefore, although the size of the silver particles to be used is not particularly limited, it is preferable to use particles having the smallest possible particle size. By using particles having a small particle size, the catalytic activity is improved, and as a result, the selectivity of glyoxal can be improved.

In this case, the thickness of the catalyst layer is sufficiently 10 mm or less, preferably 5 to 10 mm. Although a sufficient catalytic activity can be obtained with a diameter of 5 mm or less, it is very difficult to uniformly fill the catalyst with a thickness of 5 mm or less in a catalyst packed bed of a large-diameter reactor.

In view of this point, the present inventors have focused on the use of diatomaceous carbide (hereinafter abbreviated as SiC) particles as a support layer for a catalyst of fine silver particles, thereby suppressing the production of glycolaldehyde and the desired reaction. I was able to get a grade. By using the SiC support layer in this manner, even if there is some variation in the catalyst filling height of the silver particles, there is an effect that the variation in the air flow resistance of each portion on the catalyst packed layer surface is averaged. This is more effective as the reactor becomes larger. Further, the use of SiC as a material for the support layer has a very important significance. First, SiC is completely inert to this reaction,
Second, SiC has a high thermal conductivity as a ceramic. Due to such properties, SiC can be used as an excellent catalyst support layer in the present invention. As described above, the effect of using SiC is not only a mere support of silver particles, but also an effect of shortening 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 described above, is also generated in the reaction part of the catalyst, but is also generated by a post-reaction between glyoxal molecules while the reaction gas exits the reaction zone and is kept at a high temperature. Therefore, filling with SiC is very effective in reducing the residence time under the catalyst layer. The SiC and the support layer play such a role.

Alumina, which is generally considered to be inert, is not inert at high temperatures as in the present reaction. When α-alumina is used as the support layer, the amount of formalin, CO, and CO ₂ increases, and not only the yield of glyoxal decreases, but also the amount of glycolaldehyde extremely increases. Although the mechanism is not clear, the reaction solution is slightly colored yellow. Further, other ceramics having high thermal conductivity, such as nitrides, cannot chemically withstand the reaction environment of oxidizing atmosphere at high temperature.

The SiC used in the present invention is not particularly limited as long as it is generally used for a catalyst carrier or the like. Table 1 shows examples of commercially available products used in the present invention.
In addition, a sintered body of high-purity SiC powder for a fine ceramics sintered body may be used by appropriately grinding it.

Next, the particle size of the SiC used as the support layer can support silver particles having a small particle size used for the catalyst, and in addition, the particles having a particle size slightly larger than the particle size of the silver particles to those having a particle size of several mm in order, What is necessary is just to pile up what supports fine particles. Specifically, it is preferable to use one having a thickness of about 0.1 mm to 3 mm. Suitably, the total thickness of the support layer is between 10 and 30 mm. However, it is not necessary to unnecessarily increase the thickness of the support layer. These support layers are usually laminated on a special steel or a support surface having gas flow holes of a vertically arranged reactor, and the top of the support layer is filled with a silver catalyst having a fine particle size, and the raw material gas is directed from top to bottom. The method of letting it flow is taken.

Next, as the powdered silver used for the catalyst, not only powdered silver obtained by an electrolysis method, but also finely powdered silver produced chemically, for example, obtained by an alkali precipitation method, or generally gaseous silver It can be used regardless of its preparation method, such as fine powder obtained by various heating methods in an inert gas.

In the present invention, phosphorus or a phosphorus compound may be mixed with ethylene glycol in a predetermined amount in advance and subjected to the reaction, or may be added to the reaction system separately or as a solution separately from ethylene glycol. Examples of the phosphorus compound include inorganic phosphorus compounds such as ammonium orthophosphate, diammonium hydrogenphosphate, ammonium dihydrogenphosphate, ammonium dihydrogen phosphite, and primary to tertiary phosphines such as mono-, di- or trimethylphosphine; Various organic phosphorus compounds such as phosphites such as methyl acid and ethyl phosphite, dimethyl ester of methyl phosphonate and diethyl ester of ethyl phosphonate can be effectively used.

However, phosphorus compounds having a high boiling point require the evaporator temperature to be particularly high, or these phosphorus compounds stay in the evaporator to decompose and accumulate, thereby causing corrosion of equipment materials and causing iron rust generated. Etc. fly to the reaction layer,
It is not preferable because it may adversely affect the reaction.
Therefore, more preferably, an organic phosphorus compound having a relatively low boiling point, for example, methyl phosphite, ethyl phosphite, methyl phosphate, ethyl phosphate and the like are used.

The addition amount of this phosphorus or phosphorus compound is suitably in the range of 0.1 to 50 ppm in terms of phosphorus based on ethylene glycol. By the addition of the phosphorus or the phosphorus compound, the production of oxidation products such as carbon monoxide and carbon dioxide and decomposition products such as formaldehyde is significantly suppressed as compared with the case where they are not added, and the glyoxal which is the target product is produced. The yield rate of 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 ratio of carbon monoxide, carbon dioxide or formaldehyde immediately increases. This suggests that the added phosphorus or phosphorus compound is acting effectively in the gas phase, rather than accumulating and acting on the catalyst.

When the amount of phosphorus or phosphorus compound added is less than 0.1 ppm in terms of phosphorus based on ethylene glycol, the effect obtained is small and not practical. Further, if phosphorus or a phosphorus compound exceeding 50 ppm in terms of phosphorus is added, various reaction suppressing effects such that the reaction cannot be maintained even in the presence of a powdery silver catalyst appear, so that it is not practical.

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

Further, in order to obtain glyoxal in high yield, ethylene glycol and molecular oxygen are diluted with an inert gas to cause a reaction. Inert gases such as nitrogen, helium,
A rare gas such as argon, carbon dioxide gas or water vapor is used.

The reaction temperature of 450 to 650 ° C. is suitable for the gas phase oxidation of the method of the present invention.

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 only causes decomposition of unstable aldehydes.

The cooled gas is divided as necessary to recover unreacted ethylene glycol. If unreacted ethylene glycol is not contained, or a trace amount of ethylene glycol remains to the extent that it does not pose a problem as a product, and if it is not necessary to remove it, cool and condense it in a heat exchanger and then use a normal absorption operation. Separate from gas phase components.

The aqueous solution of glyoxal thus obtained contains an organic acid and a trace amount of formaldehyde as impurities. This formaldehyde is easily removed by a usual stripping operation by blowing steam, and at this time, a part of low-boiling organic acids such as formic acid and acetic acid are also removed.
The aqueous glyoxal solution obtained by the oxidation of ethylene glycol using a powdery silver catalyst contains almost no glycolaldehyde, which is a reaction intermediate, as compared with those synthesized without using a powdery silver catalyst. The amount of organic acid contained in the aqueous glyoxal solution further subjected to the formaldehyde stripping treatment is an appropriate amount of acid necessary for maintaining the stability of the product, so that no further separation treatment is required. Therefore, it is only necessary to perform a decoloring treatment and a treatment with a cation exchange resin as required.

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

EXAMPLES Next, the present invention will be described more specifically with reference to examples.

Example 1 SiC (Futami Abrasives Co., Ltd., TL-851) was crushed,
The particles were classified and used as a catalyst support layer, and silver particles having a particle size of 0.075 to 0.1 mm obtained by electrolysis of an aqueous silver nitrate solution were used as a catalyst.

As shown in Table 2, each layer of SiC was stacked in the reactor, and the silver particles were stacked on the uppermost layer. However, the SiC layer was received with a copper mesh of 100 mesh.

This reactor is an evaporator, passed through a preheater, ethylene glycol 140 g / Hr, steam 140 g / Hr, air 262 Nl / Hr, nitrogen 540 Nl / Hr, and triethyl phosphite 5 ppm as phosphorus relative to ethylene glycol. The added mixed gas was supplied in a downward flow to cause a reaction at a reaction temperature of 585 ° C. After cooling the reaction gas, the product was separated and collected in a water absorption tower.

As a result, ethylene glycol conversion was 99.9%, glyoxal selectivity was 84.3%, formalin selectivity was 2.4%, and glycolaldehyde selectivity was 0.05%. The space-time yield with respect to the silver catalyst was 113 g glyoxal / cm ³ · catalyst volume · hour.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that the same reactor as in Example 1 was used and the SiC portion was replaced with silver particles having the same particle size. Table 3 shows the loading of silver particles.

As a result of the reaction, the ethylene glycol conversion was 99.9%, the glyoxal selectivity was 64.8%, the formalin selectivity was 6.2%, and the glycolaldehyde selectivity was 0.43%. The space-time yield for the silver catalyst was 20.2 g-glyoxal / cm ³ · catalyst volume · time.

Comparative Example 2 A reaction was performed under the same conditions as in Example 1 except that triethyl phosphite was not added to the reactor. As a result, 100% ethylene glycol conversion, 38.6% glyoxal selectivity, 11.2% formalin selectivity, 0.05% glycolaldehyde selectivity
Met.

Comparative Example 3 In place of SiC, α-alumina (AL-873, manufactured by Fujimi Abrasives Co., Ltd.) was crushed as a support layer and charged into a reactor to have the same particle size distribution as in Example 1. The reaction was carried out under the conditions. As a result, ethylene glycol conversion was 99.1%, glyoxal selectivity was 58.7%, formalin selectivity was 9.3%, and glycolaldehyde selectivity was 7.8%. Also, 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 stacked on a 100-mesh copper net in the same manner as in Example 1 and reacted under the same conditions as in Example 1. However, the thickness of the catalyst layer of silver particles is
The reaction was carried out for two types, 5.0 mm and 15.0 mm, respectively.

The results are shown in Table 4. After the completion of the reaction, the inside of the reactor was inspected and found to have leaked a considerable amount from the mesh of the copper net used for the catalyst. Therefore, it is industrially impossible to use only such fine silver powder directly on a copper net. At a catalyst layer thickness of 15.0 mm, the pressure loss was as large as 0.6 kg / cm ² , twice as large as that in Example 1.

Example 2 An experiment was performed under the same reaction conditions except that the thickness of the silver particle layer of the catalyst shown in Example 1 was 3 mm. As a result, the ethylene glycol conversion rate was 98.2% and the glyoxal selectivity was 81.2%.
%, Formalin selectivity 2.6%, and glycolaldehyde selectivity 0.03%. The space / time yield with respect to the silver catalyst was 181 g-glyoxal / cm ³ · catalyst volume / time.

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 added amount of phosphorus was 3 ppm and the reaction temperature was 570 ° C.

As a result, the ethylene glycol conversion was 99.8%, the glyoxal selectivity was 80.2%, the formalin selectivity was 8.2%, and the glycolaldehyde selectivity was 0.04%. The space / time yield with respect to the silver catalyst was 108 g-glyoxal / cm ³ · catalyst volume · time.

Example 4 Silver particles were stacked on the catalyst layer up to the uppermost layer in Table 2 of Example 1 and the second layer below SiC, and the reaction was carried out in the same manner as in Example 1 except for the above.

As a result, the ethylene glycol conversion was 99.9%, the glyoxal selectivity was 84.2%, the formalin selectivity was 2.1%, and the glycolaldehyde was 0.04%.

〔The invention's effect〕

According to the method of the present invention, glyoxal can be produced with good selectivity from inexpensive raw materials and high productivity per expensive silver catalyst, which greatly contributes to industry.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C07C 47/127 C07C 45/38 B01J 32/00 B01J 31/26 B01J 27/224 WPI / L (QUESTEL) CA (STN)

Claims (1)

(57) [Claims] 1. A method for producing glyoxal by vapor-phase oxidation of ethylene glycol, comprising contacting a gas containing ethylene glycol and molecular oxygen with a granular silver catalyst at a high temperature in the presence of phosphorus or a phosphorus compound. A process for producing glyoxal, comprising using a silver particle catalyst layer supported by a silicon carbide particle layer in performing oxidation.