JP6396246B2 - Carbon monoxide production method - Google Patents

Description

  The present invention relates to a method for producing carbon monoxide. More particularly, the present invention relates to a method for producing high-purity carbon monoxide having a purity of 99.99% or more used in the field of semiconductor production such as integrated circuits.

  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 decomposed and dehydrated using sulfuric acid or a solid catalyst. Methods for purification and the like are known. Considering the purification process, the formic acid decomposition method is more advantageous because carbon monoxide can be obtained with high selectivity. However, when dehydration is performed using sulfuric acid, the water produced by the reaction lowers the sulfuric acid concentration. In order to maintain the reaction rate, a large amount of sulfuric acid is required, and it is not an industrially preferable method from the viewpoint of treatment of waste water containing sulfuric acid.

  On the other hand, the method for decomposing formic acid using a fixed catalyst does not cause the above-mentioned problem, but a side reaction for generating hydrogen and carbon dioxide occurs in addition to the carbon monoxide production reaction. That is, as the decomposition reaction of formic acid, a reaction that gives carbon monoxide and water as products (main reaction) and a reaction that gives carbon dioxide and hydrogen (side reactions) are known. For the purpose of obtaining high purity carbon monoxide, it is desired that only the main reaction proceeds selectively. For example, Patent Document 1 discloses a means for selectively allowing only the main reaction to proceed. According to this method, when a zeolite modified with a mineral acid is used as a catalyst, the main reaction proceeds with high selectivity at a reaction temperature of 110 to 150 ° C., and high-purity carbon monoxide can be obtained.

  However, the mineral acid-modified zeolite used in this reaction is stable for a long time when the reaction is performed at a constant temperature, but when the catalyst temperature changes, the catalyst is physically destroyed, that is, pulverized, As a result, the catalyst life is shortened. In this pulverization, for example, when the reactor is operated under the condition of daytime operation and nighttime stop, the catalyst is rapidly pulverized due to the temperature difference between daytime and nighttime.

Japanese Patent No. 3856872

  The present invention has been conceived under such circumstances, and performs intermittent operation in a method for producing carbon monoxide by a thermal decomposition reaction of formic acid using a zeolite-based catalyst previously modified with a mineral acid. Even in such a case, an object is to provide a production method suitable for preventing thermal deterioration of the catalyst.

  As a result of the pursuit of the cause of the above-mentioned powdering, the present inventors do not mean that the mineral acid-modified zeolite is thermally weak under heating, and the mineral acid-modified zeolite is thermally changed compared to the unmodified zeolite. It turned out to be fragile. That is, the formic acid decomposition catalyst is pulverized by raising and lowering the catalyst layer temperature, and the catalyst life is shortened.

  Therefore, as a result of intensive studies to solve this problem, the present inventors have found that the catalyst layer is placed when the catalyst layer is placed at a constant temperature, or when the temperature change rate is smaller than a certain range even if there is a temperature change. It has been confirmed that the damage received by can be reduced, and the present invention has been completed.

  That is, the gist of the present invention is that in the method for producing carbon monoxide by thermally decomposing formic acid, the formic acid is decomposed intermittently at a reaction temperature of 110 to 150 ° C. using a zeolite-based catalyst previously modified with mineral acid. And a method for producing carbon monoxide, wherein the temperature change rate of the catalyst is within 60 ° C. per hour throughout the reaction and during the reaction stop.

  Preferably, the catalyst temperature when the reaction is stopped is in a temperature range 0 to 60 ° C. lower than the catalyst temperature when the reaction is performed.

  Preferably, the zeolitic catalyst is H-mordenite or H-ZSM-5 modified with a mineral acid.

  Preferably, the mineral acid is sulfuric acid.

  Hereinafter, the present invention will be specifically described.

  Examples of the zeolitic catalyst used in the present invention include H-mordenite, H-ZSM-5, clinoptilolite, etc. Among them, H-mordenite and H-ZSM-5 are excellent in acid resistance. It is a catalyst suitable for the purposes of the present invention. As these zeolite-based catalysts, commercially available products can be used as they are. The H-mordenite catalyst used in the present invention is not particularly limited as long as the Si / Al atomic ratio is about 5 to about 30, and either natural mordenite or synthetic mordenite can be used. For example, the Si / Al atomic ratio is about 5 for natural products and about 5 to about 30 for synthetic products, and any ratio can be used as a catalyst. When the Si / Al atomic ratio is less than about 5, the catalyst activity tends to decrease, which is not preferable. When the Si / Al atomic ratio is more than about 30, the catalyst preparation becomes complicated and tends to be economically disadvantageous.

  H-mordenite is usually obtained by treating mordenite with about 1 N hydrochloric acid. H-mordenite itself also has a formic acid decomposition activity, but a high temperature of 200 ° C. or higher is necessary for its activity to be fully exerted. In the present invention, by modifying H-mordenite with a high concentration of mineral acid, sufficient results can be obtained in both the reaction rate and the reaction selectivity even at relatively low temperatures, and the production of hydrogen and methane can also be suppressed. The effect of the present invention is achieved.

  Examples of the mineral acid that can be used in the present invention include sulfuric acid, hydrochloric acid, phosphoric acid and the like. Among them, sulfuric acid can be suitably used from the viewpoint of cost and ease of wastewater treatment. The concentration of the mineral acid is not particularly limited, but is usually 30 to 98% by weight, preferably 50 to 80% by weight. When the concentration of the mineral acid is lower than 30% by weight, the carbon monoxide production activity is low, and it is difficult to achieve the object of the present invention.

  In the present invention, as a method of modifying the zeolitic catalyst with a mineral acid in advance, for example, prior to its use, the zeolitic catalyst is added to a 30 to 98 wt% sulfuric acid or sulfuric acid aqueous solution at 20 to 50 ° C. for 0.5 to 0.5%. Examples include a method of immersing for 24 hours, or a method in which a column packed with a zeolite catalyst is filled with 30 to 98% by weight sulfuric acid aqueous solution and left at 20 to 50 ° C. for 0.5 to 24 hours and then the sulfuric acid aqueous solution is allowed to flow out. . When hydrochloric acid or phosphoric acid is used as the mineral acid, 10 to 37% by weight hydrochloric acid or 30 to 98% by weight phosphoric acid can be used in place of the sulfuric acid.

  As the formic acid used in the present invention, a commercially available product (for example, manufactured by Guangei Co., Ltd.) can be used as it is. The concentration of formic acid at the time of use is not particularly limited, but the reaction can be efficiently carried out by using 40 to 100% by weight of formic acid or formic acid aqueous solution. When the concentration is less than 40% by weight, since the remaining part other than formic acid is water, a large amount of energy is required 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 a catalyst previously modified with a mineral acid as described above and thermally decomposing it. As the reactor, a reaction kettle or a column packed with a catalyst is used. Carbon monoxide may be generated by charging the catalyst and formic acid into a reaction kettle and heating, but considering the reaction efficiency, it is preferable to ventilate formic acid through a column packed with catalyst. In this case, formic acid may be passed through a one-column reactor, or a multitubular reactor may be used. In particular, a multi-tubular reactor is preferable because it can prevent a single flow of gas and can secure a heat transfer area for heating.

  The reaction using this catalyst proceeds at a relatively low temperature, and the reaction temperature is usually 110 to 150 ° C, preferably 120 to 150 ° C. If the reaction temperature is less than 110 ° C., the reaction is difficult to proceed and the conversion rate is low, which is not preferable. If the reaction temperature exceeds 150 ° C., side reactions occur and hydrogen and methane concentrations in carbon monoxide tend to increase, which is preferable. Absent.

  As a material for the reactor used in the present invention, a material that is not corroded by formic acid and carbon monoxide and does not affect the reaction is required, but a non-metallic material such as carbon is suitable for satisfying the requirements. Can be used. In addition, since the reaction proceeds at a relatively low temperature of 110 to 150 ° C., it is possible to use the equipment by glass lining.

  As an example of this reaction, when the reaction was carried out at a temperature of 140 ° C. using a modified zeolite catalyst obtained by treating H-mordenite with sulfuric acid, the catalyst was maintained without being pulverized even during continuous operation for one month. On the other hand, it was operated at the same temperature for 8 hours in the daytime, and then the temperature of the catalyst layer was decreased to 70 ° C. in 1 hour (temperature change rate was 70 ° C. per hour), and then the reactor was left as it was until the next morning, The next morning, the temperature of the catalyst tank is increased again from around room temperature to 140 ° C over 1 hour over about 1.5 hours (temperature change rate is 47 ° C per hour), and then the reaction is started. For 2 weeks, the catalyst was pulverized.

  Further, as an application of this knowledge, even when the operation was stopped, the catalyst maintained its activity without being pulverized even if the temperature of the catalyst layer was kept the same as the temperature during the reaction.

  Carbon monoxide obtained by this reaction contains water and trace amounts of hydrogen, carbon dioxide and methane as impurities. By controlling the temperature of the catalyst layer according to the method of the present invention, no change was observed in the amount of trace impurities generated. As a method for obtaining a high purity carbon monoxide by further adding a purification step to this gas, a combination of known methods can be used. As an example, there is a method of washing with thin caustic soda to remove trace amounts of unreacted formic acid and carbon dioxide, and then drying to remove water to obtain high purity carbon monoxide. The purity of the carbon monoxide obtained in this way is 99.99% or more and can be used not only for the semiconductor manufacturing field but also for various applications.

  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 and the like 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 of 7.6) to a length of 11 cm. The catalyst used is 50 ml. The column was prefilled with 70 wt% sulfuric acid solution and contacted with the catalyst at 40 ° C for about 2 hours. After the sulfuric acid was allowed to flow out of the column, an 88% by weight aqueous formic acid solution was then sent to the top of the reactor as a steam at 130 ° C. at a rate of 45 g / h through a vaporizer provided at the front stage of the column. The reaction was performed at 130 ° C. with the outside heated. This reaction was performed for 8 hours, and then the supply of formic acid aqueous solution was stopped to stop the reaction. The reaction stop time was 16 hours, and the temperature of the catalyst layer was kept at 130 ° C. during that time. The next day, the reaction was started under the same conditions as the previous day, and the reaction was carried out for 8 hours as in the previous day. This operation was repeated for 2 weeks.

  After intermittent reaction as described above for 2 weeks, the reaction gas was taken out from the lower part of the reactor and analyzed, and the conversion rate and selectivity of the reaction were determined. 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 with a gas chromatograph mass spectrometer (GC-MS). As a result, the reaction proceeded at a conversion rate 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 carbon dioxide contained in a trace amount, and further washed with water. This gas was passed through the zeolite and dried. As a result, high purity carbon monoxide of 99.99% or more was obtained. This gas contained 0.2 ppm hydrogen and 0.4 ppm methane as impurities. Further, when the catalyst after two weeks passed was taken out and sieved with a 20 mesh sieve, 0.02% by weight of catalyst-derived powder was recognized under the sieve.

[Example 2]
The reaction was carried out for 8 hours under the same conditions as in Example 1, and then the catalyst layer was cooled to 60 ° C. in 90 minutes by water cooling (temperature change rate was 47 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 60 ° C., and the next day, the temperature was raised to a predetermined reaction temperature of 130 ° C. in 90 minutes (the temperature change rate was 47 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. This operation was repeated for 2 weeks, but no change was observed in the conversion and selectivity of the reaction. When the catalyst was taken out and sieved with a 20 mesh sieve, 0.02% by weight of the catalyst-derived powder was recognized under the sieve.

Example 3
The reaction was carried out for 8 hours under the same conditions as in Example 1, and then the catalyst layer was cooled to 70 ° C. in 60 minutes by water cooling (temperature change rate was 60 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 60 ° C., and the temperature was raised to the predetermined reaction temperature of 130 ° C. in 60 minutes on the next day (the temperature change rate was 60 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. This operation was repeated for 2 weeks, but no change was observed in the conversion and selectivity of the reaction. When the catalyst was taken out and sieved with a 20 mesh sieve, 0.04% by weight of the catalyst-derived powder was observed under the sieve.

Example 4
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 of 7.6) to a length of 11 cm. The catalyst used is 50 ml. The column was prefilled with 70 wt% sulfuric acid solution and contacted with the catalyst at 40 ° C for about 2 hours. After the sulfuric acid was allowed to flow out of the column, an 88 wt% formic acid aqueous solution was then sent to the top of the reactor as a steam at 140 ° C. at a rate of 45 g / h through a vaporizer provided at the front stage of the column. The reaction was carried out at 140 ° C. with the outside heated. This reaction was performed for 8 hours, and then the supply of formic acid aqueous solution was stopped to stop the reaction. The reaction stop time was 16 hours, and the temperature of the catalyst layer was kept at 140 ° C. during that time. The next day, the reaction was started under the same conditions as the previous day, and the reaction was carried out for 8 hours as in the previous day. This operation was repeated for 2 weeks.

  After intermittent reaction as described above for 2 weeks, the reaction gas was taken out from the lower part of the reactor and analyzed, and the conversion rate and selectivity of the reaction were determined. 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 with a gas chromatograph mass spectrometer (GC-MS). As a result, the reaction proceeded at a conversion rate 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 carbon dioxide contained in a trace amount, and further washed with water. This gas was passed through the zeolite and dried. As a result, high purity carbon monoxide of 99.99% or more was obtained. This gas contained 0.3 ppm of hydrogen and 0.4 ppm of methane as impurities. Further, when the catalyst after two weeks passed was taken out and sieved with a 20 mesh sieve, 0.03% by weight of catalyst-derived powder was recognized under the sieve.

Example 5
The reaction was carried out for 8 hours under the same conditions as in Example 4. Thereafter, the catalyst layer was cooled to 70 ° C. in 90 minutes by water cooling (temperature change rate was 47 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 70 ° C., and the temperature was raised to the predetermined reaction temperature of 140 ° C. in 90 minutes on the next day (the temperature change rate was 47 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. This operation was repeated for 2 weeks, but no change was observed in the conversion and selectivity of the reaction. When the catalyst was taken out and sieved with a 20-mesh sieve, 0.03% by weight of the catalyst-derived powder was recognized under the sieve.

Example 6
The reaction was carried out for 8 hours under the same conditions as in Example 4, and then the catalyst layer was cooled to 80 ° C. in 60 minutes by water cooling (temperature change rate was 60 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 80 ° C., and the next day, the temperature was raised to a predetermined reaction temperature of 140 ° C. in 60 minutes (temperature change rate was 60 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. This operation was repeated for 2 weeks, but no change was observed in the conversion and selectivity of the reaction. When the catalyst was taken out and sieved with a 20-mesh sieve, 0.05% by weight of catalyst-derived powder was recognized under the sieve. Furthermore, this operation was repeated for 3 months, but no change was observed in the conversion and selectivity of the reaction. When the catalyst was taken out and sieved with a 20 mesh sieve, 0.01% by weight of catalyst-derived powder was newly recognized under the sieve.

Example 7
The same procedure as in Example 1 was performed except that only the catalyst was changed to H-ZSM-5. As a result, no change was observed in the conversion and selectivity of the reaction. When the catalyst was taken out and sieved with a 20 mesh sieve, 0.02% by weight of the catalyst-derived powder was recognized under the sieve.

[Comparative Example 1]
The reaction was carried out for 8 hours under the same conditions as in Example 1, and then the catalyst layer was cooled to 60 ° C. in 30 minutes by water cooling (temperature change rate was 140 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 60 ° C., and the temperature was raised to the predetermined reaction temperature of 130 ° C. in 30 minutes on the next day (the temperature change rate was 140 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. When this operation was repeated for 2 weeks, the conversion rate of formic acid decreased to 99.4%. When the catalyst was taken out and sieved with a 20 mesh sieve, 4% by weight of the catalyst-derived powder was recognized under the sieve.

[Comparative Example 2]
The reaction was carried out for 8 hours under the same conditions as in Example 4, and then the catalyst layer was cooled to 70 ° C. in 60 minutes by water cooling (temperature change rate was 70 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 70 ° C., and the temperature was raised to the predetermined reaction temperature of 140 ° C. in 90 minutes on the next day (the temperature change rate was 47 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. When this operation was repeated for 2 weeks, the conversion rate of formic acid decreased to 99.4%. When the catalyst was taken out and sieved with a 20-mesh sieve, 2% by weight of the catalyst-derived powder was recognized under the sieve.

[Comparative Example 3]
The reaction was carried out for 8 hours under the same conditions as in Example 4, and then the catalyst layer was cooled to 70 ° C. in 60 minutes by water cooling (temperature change rate was 70 ° C. per hour). Thereafter, the temperature of the catalyst layer was kept at 70 ° C., and the temperature was raised to the predetermined reaction temperature of 140 ° C. in 60 minutes on the next day (the temperature change rate was 70 ° C. per hour) to start the reaction. The time from when the reaction was stopped to when the reaction was resumed after cooling the catalyst layer, maintaining a constant temperature, and raising the temperature (reaction stop time) was 16 hours. When this operation was repeated for 2 weeks, the conversion rate of formic acid decreased to 99.3%. When the catalyst was taken out and sieved with a 20-mesh sieve, 3% by weight of catalyst-derived powder was observed under the sieve.

  From the above results, it is not a good idea to give a rapid temperature change to the catalyst. By keeping the rate of change of the catalyst temperature within 60 ° C. per hour, catalyst pulverization can be suppressed within a range that does not cause a problem in practice. It became clear.

  When carbon monoxide is obtained by decomposing formic acid with a zeolite catalyst that has been modified with mineral acid in advance, even if intermittent operation is performed, the temperature change of the catalyst is controlled within 60 ° C. per hour, thereby causing thermal degradation of the catalyst. Succeeded in preventing. When intermittent operation is repeated under the temperature conditions of the present invention, the reaction can be continued while maintaining a high conversion and high selectivity over a period of 2 weeks.

Claims (4)

  In the method for producing carbon monoxide by thermally decomposing formic acid, the formic acid is thermally decomposed intermittently at a reaction temperature of 110 to 150 ° C. using a zeolite catalyst previously modified with mineral acid, and the reaction is carried out. And a method for producing carbon monoxide, wherein the temperature change rate of the catalyst is within 60 ° C. per hour throughout the reaction stop.   The method for producing carbon monoxide according to claim 1, wherein the catalyst temperature when the reaction is stopped is in a temperature range lower by 0 to 60 ° C than the catalyst temperature when the reaction is performed.   The method for producing carbon monoxide according to claim 1 or 2, wherein the zeolitic catalyst is H-mordenite or H-ZSM-5 modified with a mineral acid.   The method for producing carbon monoxide according to any one of claims 1 to 3, wherein the mineral acid is sulfuric acid.