JP2019063778A - Catalytic oxidation system, and purification method of carbon dioxide - Google Patents

Abstract

To provide a catalytic oxidation system suitable for suppressing thermal deterioration of a catalyst, and for utilizing the catalyst efficiently.SOLUTION: A catalytic oxidation system X1 for oxidizing, by a catalyst, a hydrocarbon-based compound from raw material gas containing noncombustible gas as a principal component, and containing the hydrocarbon-based compound as impurities, includes a plurality of catalyst tanks 1 filled with the catalyst, in which the plurality of catalyst tanks 1 include low-temperature catalyst tanks 11, 12, 13 in which an upper limit temperature in the tanks is a relatively low temperature, and a high-temperature catalyst tank 14 in which the upper limit temperature in the tank is a relatively high temperature.SELECTED DRAWING: Figure 1

Description

  The present invention provides a system for catalytically oxidizing a hydrocarbon compound contained in a nonflammable gas, and carbon dioxide by catalytically oxidizing a hydrocarbon compound (impurity) contained in carbon dioxide which is a nonflammable gas. The present invention relates to a method for purifying concentrated carbon dioxide.

  Carbon dioxide emitted from a chemical plant and noncombustible exhaust gas such as helium and argon emitted from a semiconductor plant are often purified and reused after being recovered. These noncombustible exhaust gases include paraffins such as methane and ethane, olefins such as ethylene and propylene, aromatics such as benzene and toluene, and carboxylic acids such as formic acid and acetic acid other than hydrocarbons, formaldehyde, In many cases, hydrocarbon compounds represented by aldehydes such as acetaldehyde are contained. As a method of removing these hydrocarbon compounds, there is known a method of removing and converting to carbon dioxide and water by adsorption removal using activated carbon or the like or catalytic oxidation (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 05-306396 JP 2000-281327 A

  However, in the method disclosed in Patent Document 1, it is necessary to raise the temperature of the catalyst tank to 400 ° C. or higher in order to oxidize methane contained as an impurity. Also in the method disclosed in Patent Document 2, the temperature of the catalyst tank needs to be as high as 350 to 800 ° C. As a result, there is a problem that the catalyst exposed to high temperature is thermally deteriorated.

  The present invention has been conceived under such circumstances, and has as its main object to provide a catalytic oxidation system suitable for suppressing thermal deterioration of the catalyst and efficiently using the catalyst. .

  The inventors of the present invention have intensively studied the above problems, and as a result, a plurality of catalyst vessels filled with catalyst are provided, and these catalyst layers are compared with the low temperature catalyst vessel whose upper limit temperature during operation is relatively low, and the upper limit temperature is relative In the low temperature catalyst tank, the catalytic oxidation of lower paraffins such as methane is mainly progressed while the catalytic oxidation of hydrocarbon compounds other than the lower paraffins such as methane is mainly progressed in the low temperature catalyst tank by distinguishing them from high temperature catalyst tanks that are The inventors have found that it is possible to suppress the thermal deterioration of the catalyst by advancing the reaction in a high temperature catalyst tank, and have completed the present invention.

  According to a first aspect of the present invention, there is provided a catalytic oxidation system in which a hydrocarbon compound is oxidized by a catalyst from a raw material gas containing a noncombustible gas as a main component and a hydrocarbon compound as an impurity, A plurality of catalyst vessels filled with a catalyst, wherein the plurality of catalyst vessels are a low temperature catalyst vessel whose upper limit temperature in the vessel is relatively low, and a high temperature catalyst whose upper limit temperature in the vessel is relatively high A catalytic oxidation system is provided, comprising: a vessel.

  Preferably, the upper temperature limit in the low temperature catalyst tank is less than 400 ° C.

  Preferably, a plurality of the low temperature catalyst vessels are provided, and an oxygen supply unit for supplying oxygen is provided in a flow path on the upstream side of each of the plurality of low temperature catalyst vessels.

  Preferably, the flow path between the adjacent ones of the plurality of low temperature catalyst vessels is provided with a cooler for cooling the gas flowing through the flow path.

  Preferably, the noncombustible gas is carbon dioxide.

  According to the second aspect of the present invention, carbon dioxide is used to oxidize the hydrocarbon compound from the raw material gas containing carbon dioxide as the main component and hydrocarbon compound as the impurity by means of a catalyst to concentrate carbon dioxide. Using the low-temperature catalyst tank whose upper limit temperature in the tank is relatively low, and the high-temperature catalyst tank whose upper limit temperature in the tank is relatively high; A method of purifying carbon dioxide is provided which catalyzes the oxidation of hydrocarbonaceous compounds.

  Preferably, the upper temperature limit in the low temperature catalyst tank is less than 400 ° C.

  Preferably, a plurality of the low temperature catalyst vessels are provided, and catalytic oxidation of the hydrocarbon compound is performed while supplying oxygen to each of the plurality of low temperature catalyst vessels.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a schematic block diagram which shows one Embodiment of the catalyst oxidation system which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 illustrates one embodiment of a catalytic oxidation system according to the present invention. The catalyst oxidation system X1 of the present embodiment includes a plurality of catalyst vessels 1, a heater 2, a cooler 3, an oxygen supply unit 4, and flow paths 51 to 55 connecting these elements, and carbonized as an impurity. A hydrocarbon-based compound is oxidized by a catalyst from a raw material gas containing a hydrogen-based compound.

  Here, the hydrocarbon-based compound includes a “hydrocarbon” composed of carbon and hydrogen, and further includes a compound composed of carbon and hydrogen and oxygen. Examples of hydrocarbons include paraffins such as methane and ethane, olefins such as ethylene and propylene, and aromatics such as benzene and toluene. Examples of hydrocarbon compounds other than hydrocarbons include carboxylic acids such as formic acid and acetic acid, and aldehydes such as formaldehyde and acetaldehyde.

  The source gas contains a noncombustible gas as a main component. Examples of the nonflammable gas include oxygen, nitrogen, carbon dioxide, helium, argon and the like. Carbon dioxide, helium and argon are preferred in view of their recovery and recycling value. Carbon dioxide is more preferable as the noncombustible gas because carbon dioxide is generated when the hydrocarbon-based compound is oxidized. When the noncombustible gas is other than carbon dioxide, carbon dioxide generated by oxidation of a hydrocarbon compound may be removed by an appropriate means such as alkali absorption, adsorption, distillation, membrane separation and the like.

  Each of the plurality of catalyst vessels 1 has gas passage ports 1a and 1b at both ends, and a catalyst is filled between the gas passage ports 1a and 1b. The catalyst filled in each catalyst tank 1 is not particularly limited, but, for example, a Pd-based or Pt-based catalyst is used, and a Pd-Pt alloy or the like may be used. The support for supporting the catalyst is not particularly limited, and spherical alumina, honeycomb ceramic, or the like may be used.

  In the present embodiment, the plurality of catalyst vessels 1 include three low temperature catalyst vessels 11, 12, 13 and a high temperature catalyst vessel 14. In the low temperature catalyst tank 11 to 13, the upper limit temperature in the tank is relatively low. The upper limit temperature of the low temperature catalyst tank 11 to 13 is, for example, less than 400 ° C., preferably less than 350 ° C., from the viewpoint of preventing deterioration of the catalyst. In the low temperature catalyst tanks 11 to 13, mainly hydrocarbon compounds other than lower paraffins such as methane are catalytically oxidized. The temperature in the low-temperature catalyst tank 11 to 13 is, for example, 200 ° C. or higher from the viewpoint of appropriately advancing the catalytic oxidation. In the present embodiment, three low temperature catalyst vessels 11 to 13 are provided in series via the flow paths 52 and 53.

  The high temperature catalyst tank 14 has a relatively high upper limit temperature in the tank. The upper limit temperature of the high temperature catalyst tank 14 is, for example, 400 ° C. or more. In the high temperature catalyst tank 14, mainly, low-grade paraffin such as methane is catalytically oxidized. From the viewpoint of suppressing thermal deterioration of the catalyst, the upper limit temperature of the high temperature catalyst tank 14 is preferably in the range of 400 to 600 ° C. In the present embodiment, one high temperature catalyst tank 14 is provided in series downstream of the low temperature catalyst tank 13 via the flow path 54.

  The shape of each catalyst tank 1 may be a rectangular cylinder type, a cylindrical type, a multi-tubular type (shell & tube type), etc., but from the viewpoint of uniform diffusibility of gas and the load of filling operation The mold is preferred. In addition, either horizontal or vertical type may be used for each catalyst tank 1.

  In the present embodiment, the amount of catalyst charged in the catalyst tank 1 (low temperature catalyst tanks 11 to 13 and high temperature catalyst tank 14) also depends on the flow rate of the gas flowing through the catalyst tank 1, but the space velocity ( For example, it is 100 to 300,000 / h, and preferably from 5000 to 100,000 / h from the viewpoint of reaction efficiency and cost. In addition, the quantity (space velocity) of the catalyst charged about several catalyst tanks 1 may each differ.

  The heater 2 heats the gas introduced into the catalyst tank 1 to a desired temperature. In the present embodiment, the heater 2 is provided at two places, the flow path 51 connected to the upstream side of the first low temperature catalyst tank 11 and the flow path 54 connected to the upstream side of the high temperature catalyst tank 14.

  The cooler 3 is provided in the flow paths 52 and 53 between adjacent low temperature catalyst tanks 11 to 13. The cooler 3 cools the gas which is discharged from the low temperature catalyst tanks 11 and 12 and flows through the flow paths 52 and 53. For example, the temperature of the gas flowing through the flow paths 52 and 53 is lowered by heat exchange with liquid refrigerant. Let

  In the present embodiment, the flow paths 52 and 53 are provided with bypass flow paths 521 and 531 for bypassing the cooler 3. Near the upstream of the cooler 3 in the flow paths 52 and 53, automatic valves 52a and 53a are provided. Further, automatic valves 521 a and 531 a are provided in the bypass flow channels 521 and 531. These automatic valves 52a, 53a, 521a, 531a are valves which can switch between an open state and a closed state, respectively.

  The oxygen supply unit 4 supplies oxygen to the flow path on the upstream side of the catalyst tank 1 and adds oxygen to the catalyst tank 1. In the present embodiment, the oxygen supply unit 4 is branched in the flow paths 51 to 54 on the upstream side of each catalyst tank 1 (each of the plurality of low temperature catalyst tanks 11 to 13 and the high temperature catalyst tank 14). . The oxygen supply unit 4 supplies oxygen to the gas flowing in the flow paths 51 to 54.

  In the catalyst oxidation system X1 configured as described above, when the raw material gas is supplied from the upstream end of the flow path 51, the supplied gas sequentially passes through the plurality of catalyst tanks 1 (low temperature catalyst tanks 11 to 13 and high temperature catalyst tank 14). . In each catalyst tank 1, the hydrocarbon compound as an impurity is catalytically oxidized to generate carbon dioxide. In the low temperature catalyst tanks 11 to 13, hydrocarbon compounds other than lower paraffins such as methane are catalytically oxidized. In the high temperature catalyst tank 14, mainly low-grade paraffin such as methane is catalytically oxidized. The gas (carbon dioxide-enriched gas) which has passed through the high temperature catalyst tank 14 is taken out through the flow path 55. Here, "enrichment" means that in each catalyst tank 1, hydrocarbon-based compounds among the supplied gases are catalytically oxidized to generate carbon dioxide and the carbon dioxide concentration is increased.

  In the present embodiment, the plurality of catalyst vessels 1 include low temperature catalyst vessels 11 to 13 and a high temperature catalyst vessel 14. In the high temperature catalyst tank 14, for example, the upper limit temperature in the tank is set to 400 ° C. or higher, and thermal degradation of the catalyst occurs, but a plurality of catalyst tanks 1 are distinguished between a low temperature tank and a high temperature tank having different upper limit temperatures. Thus, the influence of the thermal deterioration of the catalyst can be limited to the high temperature catalyst tank 14 only. Therefore, the amount of catalyst to be replaced when replacing the catalyst can be reduced, and the time and effort of the catalyst replacement operation can be reduced, and as a result, the operation cost of the catalyst oxidation system X1 can be reduced.

  Regarding the source gas, the content of the hydrocarbon-based compound (impurity) in the noncombustible gas is not particularly limited. When the content of the hydrocarbon-based compound (impurity) is large, the calorific value at the time of the catalytic oxidation reaction increases. In the present embodiment, a plurality of low temperature catalyst vessels 11 to 13 are provided, and the flow path on the upstream side of each of the low temperature catalyst vessels is provided with the oxygen supply unit 4 for supplying oxygen. It is possible to control the reaction (heat of reaction) by the amount supplied. Further, it is possible to cool the gas by the cooler 3 in the flow paths 52, 53 between the adjacent low temperature catalyst vessels 11 to 13. Therefore, even when the content of the hydrocarbon-based compound (impurity) is large, it is possible to suppress an excessive temperature rise of the gas sequentially passing through the catalyst tank 1.

  Further, in the present embodiment, in the flow paths 52 and 53 in which the cooler 3 is provided, bypass flow paths 521 and 531 for bypassing the cooler 3 are provided. According to such a configuration, the case where the gas discharged from the low temperature catalyst tank 11, 12 is cooled by the cooler 3 and the cooler according to the content of the hydrocarbon compound (the calorific value at the time of the catalytic oxidation reaction) The case where it bypasses 3 and does not cool can be selected suitably. Thereby, the temperature of the gas introduced into the low temperature catalyst tank 12, 13 in the latter stage can be appropriately managed.

  As mentioned above, although specific embodiment of this invention was described, this invention is not limited to this, A various change is possible within the range which does not deviate from the thought of invention. For example, the number of catalyst vessels constituting the catalyst oxidation system according to the present invention is not limited to the aspect of the above embodiment. The number of low temperature catalyst vessels is not limited to three in the above embodiment, and may be one, two or four or more.

  In addition, a plurality (two or more) of high temperature catalyst tanks may be provided. When a plurality of high temperature catalyst vessels are provided, these high temperature catalyst vessels may be arranged in parallel, and it may be configured to be able to appropriately select which high temperature catalyst vessel the gas flows. When arranging a plurality of high temperature catalyst vessels in parallel, when replacing a deteriorated catalyst, the catalyst oxidation system is not interrupted by interrupting the operation of the catalytic oxidation system by flowing a gas to the high temperature catalyst vessel which is not a target of catalyst exchange. It is possible to carry out the replacement work of When the content of lower paraffins such as methane in the raw material gas is high, a plurality of high temperature catalyst vessels are arranged in series and the gas flowing between adjacent high temperature catalyst vessels is cooled to suppress an excessive temperature rise. You may do so.

  Next, the utility of the present invention will be described by way of examples.

Example 1
Carbon dioxide as the main component (noncombustible gas) and methane 200 vol.% As impurities (hydrocarbon compounds). ppm, ethylene 5000 vol. ppm, propylene 5000 vol. After preheating to 500 ° C. the raw material gas consisting of 500 ppm of raw material gas to 200 ° C., 6.1 mL of Pd-on-Alumina-supported catalyst (manufactured by ENCHEM Cat, granular) is placed in a stainless steel reaction vessel (inner diameter 20.8 mm, length 18.0 mm) The reaction was conducted through the first to third catalyst baths respectively filled. The space velocity (SV) in each catalyst tank was about 5,000 / h. The oxygen supply was added at 9.4 ml / min at the inlet of the first and second catalyst vessels, and 2.1 ml / min at the inlet of the third catalyst tank. The reaction temperature of the first catalyst tank (low temperature catalyst tank) is 230 ° C, the reaction temperature of the second catalyst tank (low temperature catalyst tank) is 230 ° C, and the reaction temperature of the third catalyst tank (high temperature catalyst tank) is 430 ° C Met. The composition of the gas discharged from the third catalyst tank was 0.38 vol% oxygen, 5 vol. Less than ppm (less than detection lower limit), ethylene 1 vol. Less than ppm (less than detection lower limit), propylene 1 vol. It was less than ppm (less than the detection lower limit). The results of this example are shown in Table 1.

Example 2
Carbon dioxide as the main component (noncombustible gas) and methane 200 vol.% As impurities (hydrocarbon compounds). ppm, ethylene 10000 vol. ppm, propylene 4000 vol. After preheating 300 mL / min of raw material gas consisting of ppm to 200 ° C, 3.4 mL of Pd-Pt alloy catalyst (manufactured by JGC Universal Corporation, honeycomb shape) is a stainless steel reaction vessel (outer diameter 20.8 mm, length 10.0 mm) The reaction is passed through first to third catalyst vessels respectively filled in The space velocity (SV) in each catalyst tank was about 5,000 / h. Oxygen was added at 7.2 ml / min each at the inlet of the first and second catalyst vessels and at 0.1 ml / min at the inlet of the third catalyst vessel. The reaction temperature of the first catalyst tank (low temperature catalyst tank) is 210 ° C, the reaction temperature of the second catalyst tank (low temperature catalyst tank) is 210 ° C, and the reaction temperature of the third catalyst tank (high temperature catalyst tank) is 400 ° C Met. The composition of the gas discharged from the third catalyst tank is oxygen 20 vol. ppm, methane 5 vol. Less than ppm (less than detection lower limit), ethylene 1 vol. Less than ppm (less than detection lower limit), propylene 1 vol. It was less than ppm (less than the detection lower limit). The results of this example are shown in Table 2.

Comparative Example 1
Carbon dioxide as the main component (noncombustible gas) and methane 200 vol.% As impurities (hydrocarbon compounds). ppm, ethylene 5000 vol. ppm, propylene 5000 vol. After preheating to 500 ° C. the raw material gas 500 mL / min consisting of ppm, 6.1 mL of Pd supported on alumina catalyst (manufactured by ENCHEM Cat, granular) 6.1 mL is made into a stainless steel reaction vessel (outside diameter 20.8 mm, length 18.0 mm) The reaction was conducted through the first to third catalyst baths respectively filled. The space velocity (SV) in each catalyst tank was about 5,000 / h. The oxygen supply was added at 9.4 ml / min at the inlet of the first and second catalyst vessels, and 2.1 ml / min at the inlet of the third catalyst tank. The reaction temperature of the first catalyst vessel was 230 ° C., the reaction temperature of the second catalyst vessel was 230 ° C., and the reaction temperature of the third catalyst vessel was 340 ° C. The composition of the gas discharged from the third catalyst tank was 0.39 vol% oxygen, 60 vol. ppm, ethylene 1 vol. Less than ppm (less than detection lower limit), propylene 1 vol. It was less than ppm (less than the detection lower limit). The results of this comparative example are shown in Table 1.

Comparative Example 2
Carbon dioxide as the main component (noncombustible gas) and methane 200 vol.% As impurities (hydrocarbon compounds). ppm, ethylene 10000 vol. ppm, propylene 4000 vol. After preheating 300 mL / min of raw material gas consisting of ppm to 200 ° C, 3.4 mL of Pd-Pt alloy catalyst (manufactured by JGC Universal Corporation, honeycomb shape) is a stainless steel reaction vessel (outer diameter 20.8 mm, length 10.0 mm) The reaction is passed through first to third catalyst vessels respectively filled in The space velocity (SV) in each catalyst tank was about 5,000 / h. Oxygen was added at 7.2 ml / min each at the inlet of the first and second catalyst vessels and at 0.1 ml / min at the inlet of the third catalyst vessel. The reaction temperature of the first catalyst vessel was 210 ° C., the reaction temperature of the second catalyst vessel was 210 ° C., and the reaction temperature of the third catalyst vessel was 350 ° C. The composition of the gas discharged from the third catalyst tank is oxygen 250 vol. ppm, methane 110 vol. ppm, ethylene 1 vol. Less than ppm (less than detection lower limit), propylene 1 vol. It was less than ppm (less than the detection lower limit). The results of this comparative example are shown in Table 2.

Comparative Example 3
Carbon dioxide as the main component (noncombustible gas) and methane 200 vol.% As impurities (hydrocarbon compounds). ppm, ethylene 10000 vol. ppm, propylene 4000 vol. After preheating 300 mL / min of raw material gas consisting of ppm to 200 ° C, 3.4 mL of Pd-Pt alloy catalyst (manufactured by JGC Universal Corporation, honeycomb shape) is a stainless steel reaction vessel (outer diameter 20.8 mm, length 10.0 mm) The reaction is passed through first to third catalyst vessels respectively filled in The space velocity (SV) in each catalyst tank was about 5,000 / h. Oxygen was added at 7.2 ml / min each at the inlet of the first and second catalyst vessels and at 0.1 ml / min at the inlet of the third catalyst vessel. The reaction temperature of the first catalyst vessel was 210 ° C., the reaction temperature of the second catalyst vessel was 210 ° C., and the reaction temperature of the third catalyst vessel was 380 ° C. The composition of the gas discharged from the third catalyst tank is oxygen 120 vol. ppm, methane 40 vol. ppm, ethylene 1 vol. Less than ppm (less than detection lower limit), propylene 1 vol. It was less than ppm (less than the detection lower limit). The results of this comparative example are shown in Table 2.

X1 catalyst oxidation system 1 catalyst tank 1a gas passage port 1b gas passage port 11 low temperature catalyst tank 12 low temperature catalyst tank 13 low temperature catalyst tank 14 high temperature catalyst tank 2 heater 3 cooler 4 oxygen supply unit 51 flow path 52 flow path 52a automatic valve 521 Bypass flow channel 521a Automatic valve 53 flow channel 53a Automatic valve 531 Bypass flow channel 531a Automatic valve 54 flow channel 55 flow channel

Claims (8)

A catalytic oxidation system in which a hydrocarbon compound is oxidized by a catalyst from a raw material gas containing a noncombustible gas as a main component and a hydrocarbon compound as an impurity,
A plurality of catalyst vessels filled with the catalyst;
The catalyst oxidation system, wherein the plurality of catalyst vessels include a low temperature catalyst vessel whose upper limit temperature in the vessel is relatively low, and a high temperature catalyst vessel whose upper limit temperature in the vessel is relatively high.   The catalytic oxidation system according to claim 1, wherein the upper limit temperature in the low temperature catalyst tank is less than 400 ° C. A plurality of the low temperature catalyst tanks are provided,
3. The catalytic oxidation system according to claim 1, wherein an upstream side flow path of each of the plurality of low temperature catalyst vessels is provided with an oxygen supply unit for supplying oxygen. 4.   The catalyst oxidation system according to claim 3, wherein a flow passage between adjacent ones of the plurality of low temperature catalyst vessels is provided with a cooler for cooling a gas flowing through the flow passage.   The catalytic oxidation system according to any one of claims 1 to 4, wherein the noncombustible gas is carbon dioxide. A method of purifying carbon dioxide comprising: oxidizing a hydrocarbon compound from a raw material gas containing carbon dioxide as a main component and a hydrocarbon compound as an impurity by means of a catalyst to concentrate carbon dioxide,
The above hydrocarbon-based compounds in the raw material gas are catalytically oxidized using a low temperature catalyst tank whose upper limit temperature in the tank is relatively low and a high temperature catalyst tank whose upper limit temperature in the tank is relatively high Let the carbon dioxide purification method.   The purification method of carbon dioxide according to claim 6, wherein the upper limit temperature in the low temperature catalyst tank is less than 400C. A plurality of the low temperature catalyst tanks are provided,
The method for purifying carbon dioxide according to claim 6 or 7, wherein the hydrocarbon-based compound is catalytically oxidized while supplying oxygen to each of the plurality of low-temperature catalyst vessels.

Images