JPH0733421A - Production of high purity carbon monoxide - Google Patents

Abstract

PURPOSE:To industrially favorably obtain high purity carbon monoxide low in hydrogen content by decomposing formic acid by heating in the presence of a mineral acid using a zeolite based catalyst. CONSTITUTION:In the production method for carbon monoxide by decomposition by heating of the formic acid, the reaction is executed in the presence of a mineral acid using the zeolite-based catalyst. As the zeolite based catalyst, among catalysts, H-mordenite and H-ZMS-5 are suitable because they are excellent in acid resistance. When the formic acid of 40-100% purity is used, the reaction is executed efficiently. When the purity is less than 40%, the reaction unfavorably requires heating energy because the remainder except the formic acid is water. When the method is used, the high purity carbon monoxide which is usable in the semiconductor production area such as an integrated circuit and has >=99.9% purity is produced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing high-purity carbon monoxide. More specifically, the present invention relates to a method for producing high-purity carbon monoxide having a purity of 99.99% or higher, which is used in the field of semiconductor manufacturing such as integrated circuits.

[0002]

2. Description of the Related Art Conventionally, as a method for producing high-purity carbon monoxide, natural gas is steam-reformed to generate high-concentration carbon monoxide, which is further separated and purified, or formic acid is added to sulfuric acid or a solid catalyst. There is known a method of separating, dehydrating and purifying using the above. Considering the purification process, the formic acid decomposition method is advantageous because carbon monoxide can be obtained with a high selectivity, but when the dehydration reaction is performed using sulfuric acid, the water generated in the reaction lowers the sulfuric acid concentration. However, a large amount of sulfuric acid is required to maintain the reaction rate, and it is not an industrially preferable method from the viewpoint of treating wastewater containing sulfuric acid. On the other hand, the method of decomposing formic acid using a solid catalyst does not cause the above-mentioned problems, but causes a side reaction of producing hydrogen and carbon dioxide in addition to the carbon monoxide producing reaction.

[0003]

The catalyst which can be used in the method using a solid catalyst is generally an ion exchange resin, alumina, alumina / phosphorus pentoxide, calcium phosphate, calcium borate, kryptinolite, H-. Z
SM-5 / alumina and the like are known.

However, the usable temperature of the ion exchange resin is limited to about 100 to 130 ° C., and the conversion rate of formic acid at this temperature is not high. Alumina gives a high conversion rate at 300 ° C. or higher, but the carbon monoxide selectivity is 99.
It is less than 7%, and a considerable amount of hydrogen is included as an impurity. Alumina / phosphorus pentoxide, calcium phosphate, calcium borophosphate, and kryptinolite also show the same tendency as in the case of alumina. On the other hand, H-ZSM-5 / alumina has a conversion of 99.5% and a selectivity of 100 in the reaction at a reaction temperature of 250 ° C.
It is said that carbon monoxide is given in% and hydrogen is not generated at all (Bull.Soc.Belg., 92,225 (1983)). However, according to an additional test by the present inventors, in the long-run test of the H-ZSM-5 / alumina catalyst, 0.5 vol% of hydrogen is generated at the reaction temperature of 250 ° C. from the initial stage of the reaction. Therefore, H-Z
SM-5 / alumina cannot be said to be an excellent catalyst for producing high-purity carbon monoxide.

[0005]

As described above, it is difficult to achieve high conversion and high selectivity at the same time with any of the catalysts, and further, the production capacity of carbon monoxide per unit volume of the catalyst is high. Low is a problem. Also, H-
The ZSM-5 / alumina catalyst is almost satisfactory in terms of conversion, but its selectivity decreases with time, so it is difficult to say that it is an industrially preferable catalyst. Therefore, the present inventors searched for a method of decomposing formic acid into carbon monoxide and water with high conversion and high selectivity in order to develop a method for efficiently obtaining industrially advantageous high-purity carbon monoxide. . As a result, they have found that when a reaction is carried out by adding a mineral acid together with formic acid using a zeolite-based catalyst, the reaction rate is increased and the selectivity of the reaction is remarkably improved.

[0006] That is, the gist of the present invention is a method of producing carbon monoxide by thermally decomposing formic acid, wherein the above reaction is carried out in the presence of a mineral acid using a zeolite-based catalyst. The present invention relates to a method for producing carbon oxide.

In the reaction of the present invention, formic acid is passed through a vaporizer to be vaporized and introduced into the reactor to carry out the reaction. At this time, mineral acid may be mixed with formic acid and passed through the vaporizer at the same time. Alternatively, the mineral acid may be separately and continuously added to the reactor. Examples of the mineral acid that can be used in the present invention include hydrochloric acid, sulfuric acid, phosphoric acid, boric acid and the like. Among them, hydrochloric acid and sulfuric acid can be preferably used in view of cost and ease of wastewater treatment. In the case of hydrochloric acid, it may be added to the reactor in the form of hydrogen chloride in a gaseous form, or may be added to the reactor as an aqueous solution. In the case of sulfuric acid, it may be mixed with formic acid and introduced into the vaporizer, or may be added directly to the reactor. The concentration of the mineral acid is not particularly limited, but it is usually 0.05 to 5 wt%, preferably 0.3 to 3 wt% with respect to formic acid. If the acid concentration is lower than 0.05 wt%, the effect of suppressing side reactions becomes small and the amount of hydrogen generated increases. On the other hand, even if the acid concentration is higher than 5 wt%, there is no merit.

The method of the present invention can be applied to the above-mentioned known catalysts, but can be particularly preferably used for zeolite catalysts. An example of a zeolite-based catalyst is H-
Examples thereof include mordenite, H-ZSM-5, clinoptilolite, etc. Among them, H-mordenite and H-ZSM-5 are catalysts suitable for the purpose of the present invention because they have excellent acid resistance. The H-mordenite catalyst used in the present invention is not particularly limited as long as the Si / Al atomic ratio is 5 to 30, and both natural mordenite and synthetic mordenite can be used. For example, the Si / Al atomic ratio is 5 for natural products and about 5 to about 30 for synthetic products, and any ratio can be used as a catalyst. If the Si / Al atomic ratio is less than 5, it is not preferable because the catalytic activity will decrease.
If it is greater than 0, the catalyst preparation becomes complicated and uneconomical. Further, it is often effective to impregnate the zeolite catalyst with a mineral acid prior to its use.

The concentration of formic acid used in the present invention is not particularly limited, but the reaction can be efficiently carried out by using 40-100% pure formic acid. If the purity is less than 40%, the remaining portion other than formic acid is water, which requires energy for heating, which is not a good idea.

The reaction in the present invention is carried out by bringing vaporized formic acid into contact with the above catalyst. As the reactor, a reaction vessel or a tower filled with a catalyst is used. Carbon monoxide may be generated by charging a catalyst, formic acid and mineral acid into a reaction kettle and heating them, but considering the reaction efficiency, it is preferable to ventilate the vapor of mineral acid and formic acid into the column packed with the catalyst. . In this case, formic acid may be passed through the one-column type reactor, or a multitubular type reactor may be used. In particular, a multi-tubular reactor is preferable because it can prevent one-way flow of gas and can secure a heat transfer area for heating.

The reaction using this catalyst proceeds at a relatively low temperature,
The reaction temperature is usually 150 to 350 ° C. Reaction temperature is 1
If the temperature is lower than 50 ° C., the reaction becomes difficult to proceed and the conversion rate becomes low, which is not preferable, and if it exceeds 350 ° C., a side reaction becomes remarkable, and the hydrogen concentration in carbon monoxide becomes high, which is not preferable. In addition, H-mordenite and H-ZSM-
When 5 is used as a catalyst, the reaction can be continued while maintaining high conversion and high selectivity over a period of 3 months or more.

The carbon monoxide obtained by this reaction contains water and a trace amount of hydrogen, carbon dioxide and a mineral acid as impurities. As a method of further purifying the gas to obtain high-purity carbon monoxide, known combinations can be used. As an example, high purity carbon monoxide can be obtained by washing with dilute caustic soda to remove a small amount of unreacted formic acid and carbon dioxide, and then drying to remove water. The carbon monoxide thus obtained has a purity of 99.99% or more, and can be used not only in the semiconductor manufacturing field but also in various applications.
As the material of the reactor used in the present invention, those that are not corroded by formic acid and carbon monoxide, and those that do not affect the reaction are required, but aluminum, titanium, zirconium, carbon, etc. that satisfy the requirements Can be preferably used.

[0013]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the examples shown here.

Example 1 A column having an inner diameter of 2.5 cm and a length of 60 cm was packed with H-mordenite (Si / Al atomic ratio 7.6) to a length of 11 cm. The catalyst used is 50 ml. A vaporizer of formic acid was provided in the preceding stage of this column. 35% hydrochloric acid water added to a commercially available 88% pure formic acid in an amount of 2 wt% was used as a raw material, and was sent to the upper portion of the reactor as vapor at 130 ° C. at a rate of 45 g / h through a vaporizer. The reaction was performed at 250 ° C. by heating the outside. The reaction gas was taken out from the lower part of the reactor and analyzed to determine the conversion and selectivity of the reaction. The conversion rate of formic acid is obtained by quantifying unreacted formic acid,
The selectivity to carbon monoxide was determined by quantifying the amount of hydrogen produced with a gas chromatograph mass spectrometer (GC-MS). As a result, the reaction proceeded at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more.
The obtained reaction gas was washed with a 10% aqueous sodium hydroxide solution to remove a small amount of carbon dioxide, and further washed with water. The gas was passed through zeolite to dry. As a result, high-purity carbon monoxide of 99.99% or more was obtained. This gas contained 3.4 ppm of hydrogen as an impurity.

Example 2 In place of 35% hydrochloric acid water, 96% sulfuric acid was added to formic acid in an amount of 0.5 w.
The reaction was performed in the same manner as in Example 1 except that t% was added. As a result, the reaction proceeded at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was obtained, in which hydrogen contained 1.6 pp.
m was included.

Example 3 In place of 35% hydrochloric acid water, 96% sulfuric acid was added to formic acid at 1.0 w.
The reaction was performed in the same manner as in Example 1 except that t% was added. As a result, the reaction proceeded at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was obtained, in which hydrogen contained 0.9 pp.
m was included.

Example 4 Example 4 was repeated except that the reaction temperature was 225 ° C. As a result, the reaction proceeded at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was obtained, and 0.4 ppm of hydrogen was contained therein.

Example 5 Example 5 was repeated except that the reaction temperature was 300 ° C. and the filling length was 5 cm. As a result, the reaction proceeded at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was obtained, in which 14.7 ppm of hydrogen was contained.

Example 6 Example 6 was repeated except that H-ZSM-5 was used as the catalyst. As a result, the reaction proceeded at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing the purification treatment in the same manner as in Example 1, 99.
High-purity carbon monoxide of 99% or more was obtained, and 4.1 ppm of hydrogen was contained therein.

Example 7 Following Example 1, the reaction was continued under the same conditions for 70 days (1680 hours). After 70 days, the conversion of formic acid is 99.9%,
The selectivity to carbon monoxide was 99.99%, and deterioration of the catalyst over time was not particularly recognized. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was continuously obtained, in which hydrogen was 3.7.
It was contained in ppm.

Comparative Example 1 A column having an inner diameter of 2.5 cm and a length of 60 cm was filled with H-mordenite (Si / Al atomic ratio 7.6) to a length of 11 cm. The catalyst used is 50 ml. A vaporizer of formic acid was provided in the preceding stage of this column. Commercially available 88% pure formic acid was used as a raw material and passed through a vaporizer to produce steam at 130 ° C.
It was fed into the upper part of the reactor at a rate of g / h. The reaction was performed at 250 ° C. by heating the outside. The reaction gas was taken out from the lower part of the reactor and analyzed to determine the conversion and selectivity of the reaction. The conversion rate of formic acid was determined by quantifying unreacted formic acid, and the selectivity to carbon monoxide was determined by quantifying the amount of hydrogen produced by a gas chromatograph mass spectrometer (GC-MS). As a result, the conversion rate of formic acid was 99.9.
%, The reaction proceeded at a selectivity to carbon monoxide of 99.99% or more. The obtained reaction gas was washed with a 10% aqueous sodium hydroxide solution to remove a small amount of carbon dioxide, and further washed with water. The gas was passed through zeolite to dry. As a result, high-purity carbon monoxide of 99.99% or more was obtained. Hydrogen is 50 pp as an impurity in this gas.
m was included.

Comparative Example 2 The procedure of Comparative Example 1 was repeated except that the reaction temperature was 225 ° C. As a result, the reaction proceeded with a conversion of formic acid of 63.2% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was obtained, in which hydrogen was 1%.
It was contained at 7 ppm.

[0023]

EFFECT OF THE INVENTION When catalytically decomposing formic acid with a zeolite-based catalyst to obtain carbon monoxide, by adding a mineral acid to formic acid to carry out the reaction, the reaction rate is improved and the reaction can be performed with a high selectivity. Therefore, high-purity carbon monoxide having a low hydrogen content can be industrially advantageously obtained.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroyuki Hata 1 346, Miyanishi, Harima-cho, Kako-gun, Hyogo Sumitomo Seika Co., Ltd. Beppu factory

Claims (5)

[Claims] 1. A process for producing carbon monoxide by thermally decomposing formic acid to produce carbon monoxide, which comprises performing the above reaction in the presence of a mineral acid using a zeolite catalyst. 2. The method according to claim 1, wherein the zeolite-based catalyst is H-ZSM-5 or H-mordenite. 3. The production method according to claim 1, wherein the mineral acid is hydrochloric acid or sulfuric acid. 4. The concentration of mineral acid is 0.05 to 5 relative to formic acid.
The manufacturing method according to claim 1, which is wt%. 5. The production method according to claim 1, wherein the thermal decomposition temperature is 150 to 350 ° C.