HK1179596B

HK1179596B - Apparatus and process for carbon monoxide shift conversion, and hydrogen production equipment

Info

Publication number: HK1179596B
Application number: HK13106721.8A
Authority: HK
Inventors: 冈田治; 中山真衣子; 森本香; 伊藤千寻; 永冈胜俊
Original assignee: 株式会社新生能源研究
Priority date: 2010-07-06
Filing date: 2011-07-06
Publication date: 2018-04-27

Description

Carbon monoxide conversion device and method, and hydrogen production device

Technical Field

The present invention relates to a carbon monoxide shift converter and a method for converting carbon monoxide contained in a reaction gas into carbon dioxide and hydrogen by reacting the carbon monoxide with steam.

Background

In recent years, the development of clean energy (clean energy) such as a fuel cell has been actively carried out, and the demand for producing high-purity hydrogen gas has been increasing as a fuel source for the fuel cell and the like. As the hydrogen fuel, a reformed gas obtained by reforming a hydrocarbon, an alcohol, or the like is used, but the reformed gas contains about 10% of carbon monoxide and carbon dioxide in addition to hydrogen. In the case of a polymer electrolyte fuel cell operating at a low temperature of 100 ℃ or lower, carbon monoxide contained in the reformed gas poisons a platinum catalyst used in an electrode, and therefore the carbon monoxide concentration needs to be reduced to 100ppm or lower, preferably 10ppm or lower.

In order to remove carbon monoxide in the reformed gas to 10ppm or less, the carbon monoxide concentration is reduced to 1% or less by a carbon monoxide shift reaction (water gas shift reaction) in which carbon monoxide is converted into carbon dioxide and hydrogen by reacting carbon monoxide with steam, and then carbon monoxide is selectively oxidized by supplying a small amount of oxygen (air) using a platinum-based catalyst or the like, and the carbon monoxide concentration is further reduced to 10ppm or less. In the downstream process, when the carbon monoxide concentration after the upstream carbon monoxide shift reaction is high, the amount of oxygen supplied increases, and hydrogen in the reformed gas is unnecessarily oxidized, so that the carbon monoxide concentration needs to be sufficiently reduced in the upstream carbon monoxide shift reaction.

The carbon monoxide shift reaction is an equilibrium reaction (exothermic reaction) represented by the following chemical formula 1, and when the temperature is low, a composition biased to the right is obtained. Therefore, the low reaction temperature is advantageous for the conversion of carbon monoxide, but has a problem that the reaction rate is slow. Further, if the conversion of carbon monoxide (reaction to the right side) proceeds, the reaction is inhibited due to the restriction of chemical equilibrium. Therefore, a large amount of shift catalyst is required to sufficiently reduce the carbon monoxide concentration. When such a large amount of shift catalyst is required, the heating of the catalyst takes time, which is a factor of inhibiting the demand for downsizing the shift converter and shortening the start-up time, and particularly, it is a problem in a shift system for a hydrogen station, a fuel cell system for home use, and the like.

(chemical formula 1)

CO+H₂O→H₂+CO₂

The carbon monoxide shift reaction may proceed by the 1-stage reaction, but since the temperature rises as the reaction proceeds due to the exothermic reaction as described above, a configuration is generally adopted in which the catalyst layer is divided and cooled in the middle in order to obtain a favorable gas composition (for example, see non-patent document 1 described below and the descriptions of paragraphs [0002] to [0006] of patent document 1). Among these, as the shift catalyst, a copper zinc-based catalyst, a copper chromium-based catalyst, or the like that can be used at 150 to 300 ℃ is used as the downstream-side intermediate temperature and low temperature catalyst, and as the high temperature catalyst, an iron chromium-based catalyst that functions at 300 ℃ or higher is used. Copper-based shift catalysts, particularly copper-zinc-based catalysts, are more advantageous than high-temperature catalysts in that shift reactions can be performed at low temperatures of 150 to 300 ℃ and in that carbon monoxide conversion is possible, and are more advantageous in terms of cost because expensive materials such as noble metals are not used, and therefore, they are widely used in hydrogen production processes and are not limited to fuel cells. On the other hand, the active species of the copper-based shift catalyst is reduced metallic copper, but since the catalyst contains about 30 to 45% of copper oxide when it is on the market, it is necessary to reduce and activate the catalyst with a reducing gas such as hydrogen before use. On the other hand, it has been proposed to perform the reduction treatment in a short time by using a noble metal catalyst having high heat resistance (see, for example, patent documents 2 and 3 below).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2004-75474

Patent document 2: japanese patent laid-open No. 2000-178007

Patent document 3: japanese patent laid-open publication No. 2003-144925

Non-patent document

Non-patent document 1: a catalyst manual (catalyst manual ズ - ドケミ catalyst Kabushiki Kaisha) is published on pages 22 to 23 on 7 months and 1 days in 13 years

Disclosure of Invention

Problems to be solved by the invention

As described above, although catalysts of various compositions exist as shift catalysts, in order to sufficiently reduce the carbon monoxide concentration to 1% or less, it is necessary to use a large amount of a catalyst having high activity at a low temperature which is advantageous in terms of the conversion rate of carbon monoxide. Conventionally, as a factor for limiting the reaction of the shift catalyst, it is considered that the carbon monoxide shift reaction is mainly suppressed due to the restriction of the chemical equilibrium as the carbon monoxide shift reaction proceeds, and therefore it is considered that a large amount of shift catalyst is required to further reduce the carbon monoxide concentration.

The present invention has been made in view of the above-described problems of the shift catalyst, and an object thereof is to provide a carbon monoxide shift apparatus and a method for improving the conversion rate of carbon monoxide concentration without increasing the amount of the shift catalyst used.

Means for solving the problems

As a result of intensive studies by the inventors of the present invention, it has been found that there are some shift catalysts in which the catalytic activity is lowered by poisoning the active species of the catalyst with carbon dioxide which is a product of the carbon monoxide shift reaction, unlike the restriction on the chemical equilibrium, and on the other hand, there are some shift catalysts in which the lowering of the catalytic activity due to the poisoning with carbon dioxide is not significantly reflected. Further, it has been found that in a catalyst in which the catalytic activity is decreased by carbon dioxide poisoning, the decrease in catalytic activity is suppressed by controlling the reaction temperature.

In order to achieve the above object, the present invention provides a carbon monoxide shift converter and a method therefor, characterized in that the 1 st catalyst is provided in each of the upstream catalyst layers by dividing the carbon monoxide shift reaction into at least two stages, i.e., an upstream side and a downstream side, the downstream catalyst layer is provided with a2 nd catalyst, the 1 st catalyst has a characteristic that the higher the carbon dioxide concentration in the supplied reaction gas is, the lower the carbon monoxide conversion rate is when the carbon monoxide concentration and the reaction temperature in the supplied reaction gas are constant, the degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the above-described 2 nd catalyst is smaller than the degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the above-described 1 st catalyst.

According to the carbon monoxide shift device and method of the above-described feature 1, in the case where the upstream-side 1 st catalyst has a characteristic that the higher the carbon dioxide concentration in the reaction gas is when the carbon monoxide concentration in the supplied reaction gas is constant, the lower the carbon monoxide conversion rate, that is, in the case of a catalyst whose catalytic activity is decreased due to carbon dioxide poisoning, even if the higher the carbon dioxide concentration and the lower the catalytic activity are toward the downstream side of the catalyst layer due to the carbon monoxide shift reaction, the catalyst having a higher tolerance to carbon dioxide poisoning than the 1 st catalyst is used as the downstream-side 2 nd catalyst, so that the influence of the decrease in catalytic activity can be suppressed, and the carbon monoxide concentration conversion rate can be increased.

Further, in the carbon monoxide shift converter and the method according to the above-described 1, it is preferable that the 1 st catalyst is a copper zinc-based catalyst, the 2 nd catalyst is a noble metal-based catalyst, particularly a platinum-based catalyst, and the carrier of the 2 nd catalyst is cerium oxide. Further, it is preferable that the volume of the 2 nd catalyst is equal to or less than the volume of the 1 st catalyst. As described above, although the copper-zinc-based catalyst can perform the shift reaction at a low temperature of 150 to 300 ℃, as described below, it is clarified by the intensive studies of the present inventors that the copper-zinc-based catalyst is deteriorated in catalytic activity due to carbon dioxide poisoning. On the other hand, intensive studies by the inventors of the present application revealed that the platinum-based catalyst exhibits better low-temperature activity than the copper-zinc-based catalyst and has higher resistance to carbon dioxide poisoning than the copper-zinc-based catalyst. Here, when the copper zinc based catalyst is used over the entire area or on the downstream side of the catalyst layer, the carbon monoxide conversion rate is lowered due to the influence of the poisoning, and the amount of the copper zinc based catalyst used needs to be increased in order to improve the carbon monoxide conversion rate. On the other hand, by using the cu-zn based catalyst on the upstream side and the pt-based catalyst on the downstream side, it is possible to improve the carbon monoxide concentration conversion rate while suppressing the influence of carbon dioxide poisoning on the cu-zn based catalyst and suppressing the increase in cost due to the use of the pt-based catalyst, and to enjoy the advantages of both catalysts.

Further, in the carbon monoxide shift converter and the method according to the above-described feature 1, there are cases where the reaction temperatures of the 1 st catalyst and the 2 nd catalyst are controlled in common and cases where the reaction temperatures are controlled independently of each other. In the former, the temperature control of the entire catalyst layer is performed at once, and the temperature control is simplified. On the other hand, in the latter, the carbon monoxide concentration conversion rate can be further increased by controlling the upstream-side catalyst layer and the downstream-side catalyst layer to the respective optimum temperature ranges.

Further, a carbon monoxide shift converter and a method according to the 1 st aspect are the same in composition and structure as the 2 nd catalyst, and the 2 nd aspect is that the reaction temperatures of the 1 st catalyst and the 2 nd catalyst are independently controlled so that a degree of decrease in carbon monoxide conversion rate with respect to an increase in carbon dioxide concentration in the supplied reaction gas in the 2 nd catalyst is smaller than a degree of decrease in carbon monoxide conversion rate with respect to an increase in carbon dioxide concentration in the supplied reaction gas in the 1 st catalyst.

As a result of intensive studies by the inventors of the present invention, it has been found that the influence of carbon dioxide poisoning can be suppressed by controlling the reaction temperature even in the same catalyst, and therefore, even when the 1 st catalyst and the 2 nd catalyst are the same catalyst, the reaction temperature is independently controlled to lower the sensitivity of carbon dioxide poisoning of the 2 nd catalyst, and the operational effect of the above-described feature 1 can be exhibited.

Further, in the carbon monoxide shift converter and the method according to the above 2, it is preferable that the 1 st catalyst and the 2 nd catalyst are copper zinc based catalysts. As described above, although the copper-zinc-based catalyst can perform the shift reaction at a low temperature of 150 to 300 ℃, as described below, it has been clarified through intensive studies by the present inventors that the copper-zinc-based catalyst is deteriorated in catalytic activity due to carbon dioxide poisoning, and the deterioration of the catalytic activity changes depending on the temperature. Here, when the cu-zn based catalyst is used under the same temperature control over the entire area or the downstream side of the catalyst layer, the carbon monoxide conversion rate is lowered due to the influence of the poisoning, and the amount of the cu-zn based catalyst used needs to be increased in order to improve the carbon monoxide conversion rate, which is disadvantageous in terms of cost. On the other hand, the upstream side and the downstream side are independently temperature-controlled, and the influence of carbon dioxide poisoning on the downstream side copper-zinc-based catalyst is suppressed more than the upstream side, whereby the carbon monoxide concentration conversion rate can be improved.

Further, a hydrogen production apparatus according to the present invention includes: the carbon monoxide shift converter having the above features and the carbon monoxide selective oxidizer for reducing the concentration of carbon monoxide in a gas treated by the carbon monoxide shift converter by selective oxidation.

According to the hydrogen production apparatus having the above features, since combustion of carbon monoxide in the carbon monoxide selective oxidizer is reduced and combustion of hydrogen is also greatly reduced, when the apparatus is applied to a fuel cell, it is possible to improve the power generation efficiency of the fuel cell, and further, it is possible to reduce the size and the cost of the carbon monoxide selective oxidizer.

Drawings

Fig. 1 is a schematic configuration diagram schematically showing a configuration of an embodiment of a carbon monoxide shift converter according to the present invention.

FIG. 2 is a schematic configuration diagram showing a schematic configuration of an experimental apparatus for a carbon monoxide shift conversion method according to the present invention.

Fig. 3 is a view showing a gas composition of the gas to be treated used in the experimental apparatus shown in fig. 2 in a list.

Fig. 4 is a characteristic diagram showing characteristics of the carbon monoxide conversion rate of each of the 1 st catalyst and the 2 nd catalyst.

Fig. 5 is a characteristic diagram showing CO concentration dependence of the individual carbon monoxide conversion rates of the 1 st catalyst and the 2 nd catalyst.

FIG. 6 is a CO showing the individual carbon monoxide conversions of catalyst 1 and catalyst 2₂Characteristic diagram of concentration dependence.

FIG. 7 shows CO for catalyst 1 and catalyst 2₂Characteristic diagram of the measurement result of the poisoning characteristic.

FIG. 8 shows CO for catalyst 1 and catalyst 2₂Characteristic diagram of the measurement result of the poisoning characteristic.

Fig. 9 is a characteristic diagram showing characteristics of the carbon monoxide conversion ratio of the carbon monoxide conversion apparatus according to the present invention and a comparative example in which the catalyst layer structures are different from each other.

Fig. 10 is a characteristic diagram showing characteristics of the carbon monoxide conversion ratio in another example of the carbon monoxide shift conversion device according to the present invention and a comparative example in which the catalyst layer structure is different.

Fig. 11 is a characteristic diagram showing a relationship between the amount of catalyst and the carbon monoxide conversion rate in a comparative example including only the 1 st catalyst used in the carbon monoxide converter according to the present invention.

Fig. 12 is a table showing the influence of the platinum loading amount of the 2 nd catalyst used in the carbon monoxide shift converter according to the present invention.

Fig. 13 is a characteristic diagram showing an influence of the platinum loading amount of the 2 nd catalyst used in the carbon monoxide shift converter according to the present invention.

Fig. 14 is a schematic configuration diagram showing a schematic configuration of an experimental apparatus for producing hydrogen gas using the carbon monoxide shift converter according to the present invention.

Fig. 15 is a schematic configuration diagram showing another embodiment of the carbon monoxide shift converter according to the present invention.

Description of the symbols

1: carbon monoxide conversion device

2: reaction tube

3: 1 st catalyst layer

4: 2 nd catalyst layer

5: inlet port

6: an outlet

11-13: supply pipe

14: mixed gas supply pipe

15: carburetor

16: water tank

17: water supply pipe

18: electric stove

19: cover type resistance heater

20. 22: exhaust pipe

21: drain box (Drain tank) (cooler)

23: gas chromatography device

24: carbon monoxide selective oxidizer

25: air pump

26: cooling water pump

G0: gas to be treated (reaction gas)

G1, G1': treated gas

G2: treated gas (after selective oxidation)

Detailed Description

Embodiments of the carbon monoxide shift conversion apparatus and method according to the present invention (hereinafter, appropriately referred to as "apparatus of the present invention" and "method of the present invention") will be described below with reference to the drawings.

As schematically shown in fig. 1, the apparatus 1 of the present invention is configured to include, in a tubular reaction tube 2, a1 st catalyst layer 3 packed with a copper-zinc-based carbon monoxide shift catalyst (1 st catalyst) on the upstream side and a2 nd catalyst layer 4 packed with a platinum-based carbon monoxide shift catalyst (2 nd catalyst) on the downstream side. The gas G0 to be treated (reaction gas) is supplied into the reaction tube 2 from the inlet 5 of the reaction tube 2, and when passing through the 1 st catalyst layer 3 and the 2 nd catalyst layer 4, a shift reaction occurs, and the treated gas G1 after the reaction flows out from the outlet 6 of the reaction tube 2. The reaction temperature is controlled by installing the reaction tube 2 in an electric furnace or a thermostatic bath, not shown, by a known method. In the present embodiment, in order to control the temperature in the reaction tube 2 to a constant temperature, the reaction temperature in the 1 st catalyst layer 3 and the reaction temperature in the 2 nd catalyst layer 4 are controlled to the same temperature in common.

In the present embodiment, as an example, the 1 st catalyst is a commercially available copper-zinc-based catalyst (Cu/Zn catalyst) having a composition including copper oxide, zinc oxide, and alumina (carrier) prepared by a general preparation method (coprecipitation method) as a carbon monoxide shift catalyst, and the 2 nd catalyst is Pt/CeO prepared as follows₂Catalyst, i.e. preparation of dinitrodiammineplatinum crystals (Pt (NO)₂)₂(NH₃)₂) A nitric acid solution of the predetermined concentration of (4) is supported on cerium oxide (CeO)₂) Drying the mixture, and reducing the dried mixture at 300 ℃ in a hydrogen flow.

The apparatus and method of the present invention are an apparatus and method for converting carbon monoxide contained in a gas to be treated such as a reformed gas G0 into carbon dioxide and hydrogen by reacting the carbon monoxide with steam. Hereinafter, the case where the carbon monoxide conversion rate is significantly improved by using the apparatus 1 of the present invention having the above-described configuration will be described with reference to experimental data performed by the method of the present invention.

First, an experimental apparatus used in the following experiment will be described. FIG. 2 schematically shows a schematic configuration of the experimental apparatus. As shown in FIG. 2, H₂、CO、CO₂The respective elemental gases are supplied from supply pipes 11 to 13 having stop valves (stop valve), pressure reducing valves, electromagnetic valves, mass flow controllers, check valves (clack valve), pressure gauges, etc. (not shown) connected to respective supply sources, and are joined to generate H₂、CO、CO₂Is injected into the inlet of the vaporizer 15 through the mixed gas supply pipe 14. On the other hand, purified water is injected from the water tank 16 into the inlet of the vaporizer 15 through a water supply pipe 17 to which a pump, a check valve, a resistor, and the like (not shown) are attached. The purified water injected into the vaporizer 15 is vaporized at a temperature of about 200 c to produce H₂、CO、CO₂、H₂The mixed gas of O (the processing target gas G0) is injected into the reaction tube 2. In addition, in this experiment, first, onlyMixing water vapor (H)₂O) is introduced into the reaction tube 2 from the vaporizer 15, and after sufficient water vapor reaches the catalyst layer, H starts₂、CO、CO₂The supply of the mixed gas of (2). The treated gas G1 flowing out of the outlet of the reaction tube 2 through the exhaust pipe 20 is cooled by passing through a drain tank (cooler) 21 in which purified water is sealed, and the treated gas G1' from which water has been removed is supplied to the gas chromatograph apparatus 23 through an exhaust pipe 22 to which a pressure gauge, a back pressure valve, a three-way solenoid valve, and the like (not shown) are attached.

The reaction tube 2 is housed in an annular electric furnace 18, and the inlet and the outlet are covered with sheath type electric resistance heaters 19, respectively. The 1 st catalyst and the 2 nd catalyst are inserted into two stages in front and rear of the central portion of the reaction tube 2 to form the 1 st catalyst layer 3 and the 2 nd catalyst layer 4, and glass wool is filled in front and rear of the catalyst layers to fix the catalyst layers 3 and 4 so as not to move. A sheath (not shown) is inserted into the reaction tube 2 from the outlet side to the position close to the 2 nd catalyst layer 4, and a thermocouple is inserted into the sheath. With this configuration, the reaction temperature in the reaction tube 2 is measured by a thermocouple, and the heating of the electric furnace 18 and the sheathed resistance heater 19 is adjusted to control the reaction temperature in the reaction tube 2 to be constant.

In this experimental apparatus, the main body of the reaction tube 2, and the plugs (plugs) and pressure reducing valves (reducers) at the inlet and outlet are made of a metal material such as stainless steel, and the structure, size, material, and the like of the reaction tube 2 may be appropriately and appropriately selected according to the throughput of the carbon monoxide shift reaction.

In the present experiment, the above-described No. 1 catalyst (Cu/Zn catalyst) and No. 2 catalyst (Pt/CeO catalyst) were used₂Catalyst) in the form of particles having a particle diameter of 0.85 to 1mm, and performing the reaction at 200 ℃ for 1 hour₂Reducing the obtained catalyst. According to the experimental contents, the platinum loading of the 2 nd catalyst was used in three kinds of 10 wt%, 3 wt% and 1 wt%, respectively.

Next, the gas to be treated used in the experiment was treatedGas composition (H) of body G0₂、CO、CO₂、H₂Mixing ratio of O) will be described. In this experiment, 9 kinds of the gas G0 to be processed shown in the gas composition table of fig. 3 were prepared and used according to the experiment contents. Further, the 9 kinds of the gases to be processed G0 each contain a component gas (H)₂、CO、CO₂、H₂O) is controlled by controlling the mixing ratio of each component gas (H) from each supply pipe 11 to 13₂、CO、CO₂) And purified water (H) supplied to the vaporizer 15₂O) is adjusted. Gas #1 and gas #2 are 2 kinds of process gases G0 having different volume% of the total component gases. CO and CO in gas #1₂Is 4% and 14% by volume, CO in gas #2₂Is 10% and 5% by volume of (C), CO₂The size of the volume% of (c) is reversed. This is because the CO concentration of the gas to be treated G0 decreases and CO concentration decreases as the carbon monoxide reforming reaction shown in chemical formula 1 proceeds₂The concentration is rather increased, so gas #2 and gas #1 simulatively represent the gas to be treated on the upstream side and the gas to be treated on the downstream side in the catalyst layer. Gases #2 to #4 are CO₂Is fixed to a constant value (5%), and the CO volume% is different from each other, and the purpose of the present invention is to measure the CO concentration dependency of the 3 types of gas to be treated G0. Gases #5 to #7 were gases in which the volume% of CO was fixed at a constant value (1%), and CO₂3 processed gases G0 whose volume% are different from each other, for the purpose of CO determination₂Concentration dependence. Gas #8 and gas #9 are CO in gas #1 and gas #2₂Substitution to N₂For the purpose of comparing CO described later₂The effect of poisoning.

Next, fig. 4 to 6 show results of examining the characteristics of the carbon monoxide conversion rate of each of the 1 st catalyst and the 2 nd catalyst. Fig. 4 to 6(a) show the measurement results of the 1 st catalyst, and (b) show the measurement results of the 2 nd catalyst. FIG. 4 shows the results of measurements using gas #1 and gas #2 at the respective reaction temperatures, FIG. 5 shows the results of measurements (CO concentration dependence) using gases #2 to #4 at the respective reaction temperatures,FIG. 6 shows the results of measurements using gases #5 to #7 at the respective reaction temperatures (CO)₂Concentration-dependent). The 2 nd catalyst used a platinum loading of 10 wt% catalyst. In the measurement shown in fig. 4 to 6, the amount of catalyst used and the contact time of the catalyst to be measured with the gas to be treated G0 are constant except for the measurement conditions (reaction temperature, gas composition of the gas to be treated G0) shown in the figure. Specifically, the amounts of the catalysts used were 0.5cc, respectively. In addition, in the measurement of the CO concentration dependence shown in FIG. 5, CO of the gases #2 to #4 used was₂Constant concentration of CO₂The influence of the concentration is excluded, CO shown in FIG. 6₂In the measurement of the concentration dependence, the CO concentrations of the gases #5 to #7 used were constant, and the influence of the CO concentrations was excluded.

As shown in fig. 4, the higher the temperature of each of the 1 st catalyst and the 2 nd catalyst, the higher the catalytic activity and the higher the carbon monoxide conversion rate. However, it can be seen that the CO concentration sensitivity of the catalytic activity of the 1 st and 2 nd catalysts is related to CO₂The concentration sensitivity was different.

First, if CO or CO is to be used₂Gas #1 and CO, CO at 4% and 14% by volume₂When fig. 4(a) and fig. 4(b) of the gas #2 having 10% and 5% by volume are compared, the carbon monoxide conversion rate of the gas #2 is higher in the 1 st catalyst than in the gas #1, whereas the carbon monoxide conversion rate of the gas #1 is higher in the 2 nd catalyst than in the gas #2, and the two catalysts show opposite tendencies. This means that the 1 st catalyst is more suitable for the gas composition on the upstream side of the catalyst layer than the 2 nd catalyst, the 2 nd catalyst is more suitable for the gas composition on the downstream side of the catalyst layer than the 1 st catalyst, and further, means the CO concentration sensitivity and CO concentration sensitivity between the 1 st catalyst and the 2 nd catalyst₂There is a large difference in at least any one of the concentration sensitivities.

Next, when comparing FIG. 5(a) and FIG. 5(b) using gases #2 to #4 containing 10%, 4% and 2% by volume of CO, the 1 st catalyst and the 2 nd catalyst both have high CO concentrations at reaction temperatures in the range of 140 ℃ to 200 ℃There is a tendency that the conversion of carbon monoxide decreases. When the volume% of CO in fig. 4(a) and fig. 5(a) is compared between 10% and 4%, the carbon monoxide conversion rate is high when the CO concentration in fig. 4(a) is 10 vol%, whereas the carbon monoxide conversion rate is high when the CO concentration in fig. 5(a) is 4 vol%. It can be seen that the CO concentration sensitivity is opposite in FIG. 4(a) and FIG. 5(a), and the reason for this is that CO₂While the concentration changes in FIG. 4(a), CO changes in FIG. 5(a)₂The concentration was constant at 5 vol%, and therefore, in the 1 st catalyst, CO was caused to flow out₂The concentration changes, and the CO concentration sensitivity changes greatly. On the other hand, when the volume% of CO in fig. 4(b) and fig. 5(b) is compared between 10% and 4%, the CO concentration is 4 vol% and the CO conversion is high₂Change in concentration and CO₂When the concentration is constant, the CO concentration sensitivity shows the same tendency. That is, it can be seen that the 1 st catalyst is CO more than the 2 nd catalyst₂The change in concentration is sensitive.

Then, if CO is to be used₂When comparing FIGS. 6(a) and 6(b) in which the volume% of the gases #5 to #7 is 14%, 5%, and 1%, the No. 1 catalyst and the No. 2 catalyst are both in CO₂At high concentrations, the conversion of carbon monoxide tends to decrease. However, the reaction temperature is measured in the range of 140 ℃ to 200 ℃ relative to CO₂The difference in carbon monoxide conversion (degree of decrease) of the difference in concentration (from 1 vol% to 14 vol%) results in about 31% to 42% in the 1 st catalyst, while being suppressed to about 8% to 28% in the 2 nd catalyst as compared with the 1 st catalyst. Further, the reaction temperature is in the range of 140 ℃ to 200 ℃ relative to CO₂The difference in carbon monoxide conversion (decrease) of the difference in concentration (from 1 vol% to 5 vol%) was as high as about 9% to 26% in the 1 st catalyst, while being greatly suppressed to about 0% to 8% in the 2 nd catalyst as compared with the 1 st catalyst. In summary, for catalyst 1, with CO₂The carbon monoxide conversion rate greatly decreased with an increase in the concentration from a low level of 1 vol%, whereas with the 2 nd catalyst, the CO content increased with the CO content₂The concentration is from 5 vol% to aboutThe carbon monoxide conversion rate tended to be slightly lowered by the increase in the right, and it was found that CO was present between the 1 st catalyst and the 2 nd catalyst₂The concentration sensitivity is greatly different. That is, it can be judged that: about 1 vol% or more of CO₂CO at a concentration that is a product of a carbon monoxide shift reaction₂The 1 st catalyst is poisoned and the catalytic activity tends to be significantly reduced.

In the above experimental results shown in FIG. 6, the gases #5 to #7 used were CO-excluded₂H other than concentration₂And H₂The concentration of O also follows that of CO₂Since the concentration changes, CO and H are added₂、H₂CO determination with constant respective O concentrations₂Degree of poisoning, gas #1 will be used and CO in gas #1 will be₂Substitution to N₂FIG. 7 shows the results of the experiment of gas #8, using gas #2 and CO in gas #2₂Substitution to N₂The experimental results of gas #9 in (2) are shown in fig. 8. In the experiments of fig. 7 and 8, the individual carbon monoxide conversions of the 1 st catalyst and the 2 nd catalyst were measured at different reaction temperatures, respectively. In the measurement shown in fig. 7 and 8, the amount of catalyst used and the contact time between the catalyst to be measured and the process gas G0 were constant, except for the measurement conditions (reaction temperature, gas composition of the process gas G0) shown in the figure. The 2 nd catalyst used a platinum loading of 10 wt% catalyst. Further, the amounts of catalysts used were 0.5cc, respectively.

As is clear from FIGS. 7 and 8, the CO in the gas G0 to be treated is introduced₂Substitution to N₂In contrast, the carbon monoxide conversion rate of the 1 st catalyst is greatly improved, and in the 2 nd catalyst, the carbon monoxide conversion rate is hardly improved or is minimally improved as compared with the 1 st catalyst. In addition, when the measurement results of fig. 7 and 8 are compared, CO is caused by comparison of the gas #1 used in fig. 7 with the gas #2 used in fig. 8₂The concentration is high, so the carbon monoxide conversion rate is greatly increased in the 1 st catalyst by the above-mentioned substitution. The following is evident from the summary: in the 1 st catalyst, the CO concentration in the supplied reaction gas and the reactionThe CO in the supplied reaction gas should be constant in temperature₂The higher the concentration, the lower the CO conversion, i.e., CO₂On the other hand, in the 2 nd catalyst, poisoning is remarkably exhibited with respect to CO in the supplied reaction gas₂The decrease in CO conversion with increasing concentration is less than for catalyst No. 1, CO₂The degree of poisoning is minimal. In other words, the CO of the 1 st catalyst and the CO of the 2 nd catalyst can be compared by the substitution experiments shown in FIGS. 7 and 8₂And (4) poisoning characteristics.

As described above, since the content of CO is about 1% or more₂CO at concentration₂Since the 1 st catalyst tends to be poisoned and the catalytic activity tends to be remarkably lowered, when the catalyst layer of the carbon monoxide shift device is constituted by only the 1 st catalyst, CO is present on the downstream side of the catalyst layer₂The concentration becomes high and the catalytic activity is remarkably lowered. In contrast, attention is paid to CO between the 1 st catalyst and the 2 nd catalyst as described above₂The concentration sensitivity is greatly different, by using CO at the downstream side of the catalyst layer₂Relatively low concentration sensitivity, i.e. CO₂The 2 nd catalyst having a small degree of poisoning can significantly improve the carbon monoxide conversion rate and can also reduce the amount of catalyst used in the entire catalyst layer, as compared with the case where the catalyst layer is composed of only the 1 st catalyst. The results of the experiment will be described below at this point.

Fig. 9 shows the results of measuring the relationship between the carbon monoxide conversion rate and the contact time for 4 catalyst layer configurations in which the catalyst layer in the reaction tube 2 was configured in the same manner as in the apparatus 1 of the present invention, i.e., the configuration a of the present invention in which the 1 st catalyst was used on the upstream side and the 2 nd catalyst was used on the downstream side, the comparative configuration B in which the 1 st catalyst was used in the entirety as the comparative example, the comparative configuration C in which the 2 nd catalyst was used in the entirety as the comparative example, and the comparative configuration D in which the 2 nd catalyst was used on the upstream side and the 1 st catalyst was used on the downstream side as the comparative example. The catalyst amount of the catalyst layer was 3cc, and in the present invention configuration a and the comparative configuration D, the amounts of the 1 st catalyst and the 2 nd catalyst were set to be equal (1.5 cc). The reaction temperature was measured at two temperatures of 160 ℃ and 180 ℃ using gas #2 as the gas to be treated G0. In addition, the 2 nd catalyst used a platinum loading of 10 wt% of the catalyst. In addition, for comparative constitution D, the reaction temperature was a temperature of 160 ℃. The contact time (unit: second) indicated by the horizontal axis of each graph is the residence time (reciprocal of the space velocity) of the gas to be treated G0 in the catalyst layer, and is controlled by the flow rate of the gas to be treated G0 in the reaction tube 2.

As is clear from fig. 9, as the contact time becomes longer, the carbon monoxide conversion rate approaches the equilibrium conversion rate and reaches saturation as the carbon monoxide shift reaction proceeds. The carbon monoxide conversion at a contact time of about 8.7 seconds at a reaction temperature of 160 ℃ was about 93.9% in comparative configuration B in which all the catalyst layers were the 1 st catalyst, about 79.6% in comparative configuration C in which all the catalyst layers were the 2 nd catalyst, and about 99.3% in inventive configuration a in which the 1 st catalyst was used on the upstream side and the 2 nd catalyst was used on the downstream side. The difference in the carbon monoxide conversion between the comparative configuration B and the comparative configuration C in fig. 9 is consistent with the comparison result between the 1 st catalyst and the 2 nd catalyst shown in fig. 4 when the gas to be treated G0 is gas #2, and only by looking at this result, since the carbon monoxide conversion is higher when the 1 st catalyst is used as compared with when the 2 nd catalyst is used, it is preliminarily concluded that the carbon monoxide conversion is lower in the configuration a of the present invention in which the 1 st catalyst and the 2 nd catalyst are combined in half (as described below, in the comparative configuration D), as compared with the comparative configuration B, but actually, as shown in fig. 9, the carbon monoxide conversion is higher in the configuration a of the present invention in which the 2 nd catalyst is disposed on the downstream side of the 1 st catalyst. This is because, as described above, about 1% or more of CO is contained₂CO at concentration₂Since the degree of poisoning toward the downstream side of the catalyst layer tends to be significantly lower as the 1 st catalyst is poisoned, the carbon monoxide conversion rate is significantly improved by changing the downstream side from the 1 st catalyst to the 2 nd catalyst. In comparative configuration D, which also combines half of the 1 st catalyst and half of the 2 nd catalyst, the carbon monoxide conversion was 87 at a contact time of about 8.7 seconds.8%, improved over comparative configuration C, but worse than comparative configuration B.

At a reaction temperature of 180 ℃, the carbon monoxide conversion rate is saturated in a shorter contact time, so that at a contact time of about 2.9 seconds, the carbon monoxide conversion rate of any one of the present invention composition a, the comparative composition B, and C is in a substantially saturated state, 98.2% in the present invention composition a, 92.7% in the comparative composition B, and 95.9% in the comparative composition C. When the reaction temperature is 180 ℃, the conversion of carbon monoxide is improved in the present invention composition a compared with either of the comparative compositions B and C, as well as in the same manner when the reaction temperature is 160 ℃. Further, since the improvement in the carbon monoxide conversion rate of the present invention configuration a as compared with either of the comparative configurations B and C occurs after a certain contact time has elapsed, it is estimated that the carbon monoxide shift reaction proceeds and, at the same time, the CO proceeds with the CO on the downstream side of the catalyst layer₂The concentration is increased, and the effect of the invention is gradually and obviously embodied. The effect is also exhibited similarly at reaction temperatures of 160 ℃ and 180 ℃ although the effect varies depending on the contact time. From the above, it was shown that the carbon monoxide conversion rate was greatly improved by using the 1 st catalyst on the upstream side and the 2 nd catalyst on the downstream side.

Next, a relationship between the component ratio of the 1 st catalyst and the 2 nd catalyst in the configuration a of the present invention and the improvement effect of the carbon monoxide conversion rate will be described. In the configuration a of the present invention shown in fig. 9, the ratio of the 1 st catalyst to the 2 nd catalyst was 1 to 1, and the effect of improving the carbon monoxide conversion rate was confirmed when the ratio of the 1 st catalyst to the 2 nd catalyst was reduced by setting the ratio of the 1 st catalyst to the 2 nd catalyst to 10 to 1. Fig. 10 shows the results of measuring the relationship between the carbon monoxide conversion rate and the contact time (seconds) for 2 catalyst layer compositions, i.e., composition a of the present invention in which the component ratio of the 1 st catalyst to the 2 nd catalyst is 10 to 1, and comparative composition B in which the 1 st catalyst is used in its entirety. The total catalyst amount of the catalyst layer was 3.3cc, and the 2 nd catalyst constituting A of the present invention was 0.3 cc. The reaction temperature was measured at 1 temperature of 160 ℃ using gas #2 as the gas to be treated G0. In addition, the 2 nd catalyst used a platinum loading of 10 wt%.

As can be seen from fig. 10, the carbon monoxide conversion at a contact time of about 8.7 seconds (flow rate: about 20.8cc/min) was about 96.7% in comparative composition B, while the composition a of the present invention was improved to about 98.5%. When this is converted into the carbon monoxide concentration after the shift reaction, the carbon monoxide concentration is 0.15% in the case of the present invention configuration a and 0.33% in the case of the comparative configuration B, so that the carbon monoxide concentration is reduced to about 45% in the case where the component ratio of the 1 st catalyst to the 2 nd catalyst is 10 to 1 in the present invention configuration a as compared with the comparative configuration B. Fig. 11 shows the relationship between the carbon monoxide conversion and the contact time (seconds) at 3.3cc and 5cc for the 1 st catalyst in comparative configuration B as a reference example. As is clear from fig. 11, when the amount of the 1 st catalyst was 3.3cc and 5cc, substantially the same carbon monoxide conversion was achieved, and even if the amount of the 1 st catalyst was increased by about 1.5 times, the carbon monoxide concentration did not decrease unless the contact time was extended. That is, in comparative configuration B, in order to further halve the carbon monoxide concentration, more catalyst and contact time are required, but in configuration a of the present invention, the same or more effects can be obtained by using a small amount of the 2 nd catalyst.

Next, the relationship between the platinum loading amount of the 2 nd catalyst in the configuration a of the present invention and the improvement effect of the carbon monoxide conversion rate will be described. Fig. 12 shows the results of measuring the carbon monoxide conversion at a contact time of 9.5 seconds for 3 catalyst layer compositions of 2 invention composition a (the former is a1, the latter is a 2.) in which the platinum loading amount of the 2 nd catalyst is set to 3 wt% and the component ratio of the 1 st catalyst to the 2 nd catalyst is 23 to 10 and 28 to 5, and 3 catalyst layer compositions of comparative composition B (comparative composition B1) in which the 1 st catalyst is used in its entirety. Fig. 13 shows the results of measuring the relationship between the carbon monoxide conversion rate and the contact time for 4 catalyst layer configurations, i.e., a1 st catalyst which is a commercially available copper-zinc-based catalyst having a higher alumina content and a higher strength than the 1 st catalyst used in the configurations a1 and a2 of the present invention, and 3 configurations a (A3, a4, and a5 in order from the point of low platinum loading) in which the platinum loading amount of the 2 nd catalyst is set to 3 types, i.e., 1 wt%, 3 wt%, and 10 wt%, and a comparative configuration B (comparative configuration B2) in which the 1 st catalyst having a higher strength is used in total. In each of the configurations a1 to a5, the comparative configurations B1, and B2, the total catalyst amount of the catalyst layer was 3.3cc, and the 2 nd catalyst amount was set to 1.0cc in the configuration a1, 0.5cc in the configuration a2, and 0.3cc in the configurations A3 to a 5. In the measurement of the carbon monoxide conversion in fig. 12 and 13, the reaction temperature was measured at 1 temperature of 160 ℃, using the gas #2 as the gas to be treated G0.

As is clear from fig. 12, the carbon monoxide conversion rate was about 96.6% in the comparative composition B1, whereas about 98.7% and about 97.3% in the compositions a1 and a2 of the present invention, respectively, were improved over the comparative composition B1. When this is converted into the carbon monoxide concentration after the shift reaction, the carbon monoxide concentration is 0.13% in the case of the configuration a1 of the present invention, 0.27% in the case of the configuration a2 of the present invention, and 0.34% in the case of the comparative configuration B1, so that the carbon monoxide concentration is reduced to about 38% in the case where the component ratio of the 1 st catalyst to the 2 nd catalyst is 23 to 10 in the configuration a1 of the present invention, and to about 79% in the case where the component ratio of the 1 st catalyst to the 2 nd catalyst is 28 to 5 in the configuration a2 of the present invention, as compared to the comparative configuration B1. If the platinum loading amount is small, the catalytic activity of the 2 nd catalyst is decreased, but if the platinum loading amount of the 2 nd catalyst is set to 3 wt%, the carbon monoxide conversion rate is also improved.

Further, as is clear from fig. 13, when the contact time was 9.5 seconds, the carbon monoxide conversion rate was about 92.9% in the comparative composition B2, whereas about 93.5%, about 93.9%, and about 97.9% in the compositions A3, a4, and a5 of the present invention were improved over the comparative composition B1. When the platinum supporting amount of the 2 nd catalyst is small or the ratio of the 2 nd catalyst to the total catalyst amount is small, the catalytic activity in the whole of the constitution A of the present invention is lowered and the effect of the present invention is lowered, but the effect of the present invention depends on the relative relationship between the 1 st catalyst and the 2 nd catalyst, and therefore, when the 1 st catalyst itself is used as the catalystCO conversion by No. 1 catalyst having low activation₂When the degree of poisoning is large, even in the case where the platinum loading amount of the 2 nd catalyst is 1 wt% and the component ratio of the 2 nd catalyst with respect to the total catalyst amount is as small as 10%, the effect of improving the carbon monoxide conversion rate is exerted.

Next, assuming that the apparatus 1 of the present invention is used in an actual polymer electrolyte fuel cell system, the effect of applying the apparatus 1 of the present invention when a hydrogen production apparatus is configured to reduce the carbon monoxide concentration in the reformed gas to 10ppm or less (for example, 5ppm) by providing a carbon monoxide selective oxidizer downstream of the apparatus 1 of the present invention is verified. Fig. 14 schematically shows a schematic configuration of an experimental apparatus for verifying this effect. The experimental apparatus shown in fig. 14 is configured by providing a carbon monoxide selective oxidizer 24, an air pump 25, and a cooling water pump 26 on the downstream side of the exhaust pipe 20 of the experimental apparatus shown in fig. 2, instead of the drain tank (cooler) 21, the exhaust pipe 22, and the gas chromatography device 23. The treated gas G1 discharged from the reaction tube 2 of the carbon monoxide shift converter is introduced into the carbon monoxide selective oxidizer 24 through the exhaust pipe 20. The carbon monoxide selective oxidizer 24 is packed with a catalyst in which ruthenium (Ru) is supported on alumina. The exhaust pipe 20 is provided with an air pump 25 for adding oxygen for selective oxidation to the treated gas G1, and the carbon monoxide selective oxidizer 24 is further provided with a cooling water pump 26 for cooling the outer peripheral surface thereof. Although not shown, the treated gas G1 introduced from the exhaust pipe 20 into the carbon monoxide selective oxidizer 24 is cooled to 100 ℃ by air cooling. The configuration of the carbon monoxide shift converter and its peripheral equipment on the upstream side of the exhaust pipe 20 is the same as that of the experimental apparatus shown in fig. 2, and therefore, redundant description is omitted.

The present verification experiment was carried out on the catalyst layer structures in the reaction tube 2, namely, 2 catalyst layer structures, i.e., the structure a of the present invention using the 1 st catalyst on the upstream side and the structure a of the present invention using the 2 nd catalyst on the downstream side, and the comparative structure B of the comparative example using all the 1 st catalysts. The catalyst amounts of the catalyst layers were all 3cc, and in the configuration a of the present invention, the amounts of the 1 st catalyst and the 2 nd catalyst were set to be equal (1.5 cc). The reaction temperature was set to 160 ℃. The treated gas G1 was supplied to the carbon monoxide selective oxidizer 24, and the output of the air pump 25 was controlled so that the carbon monoxide concentration in the treated gas G2 discharged from the carbon monoxide selective oxidizer 24 reached 5 ppm. Further, the cooling water pump 26 is controlled so that the temperature inside the carbon monoxide selective oxidizer 24 becomes 110 ℃. In the carbon monoxide selective oxidizer 24, a selective oxidation reaction (exothermic reaction) shown in the following chemical formula 2 occurs, and a reaction consuming hydrogen gas shown in the chemical formula 3 occurs, so that there is a problem that the effective hydrogen gas used by the fuel cell decreases.

(chemical formula 2)

2CO+O₂→2CO₂

(chemical formula 3)

2H₂+O₂→2H₂O

In both the configuration a of the present invention and the configuration B of the comparison, since the output of the air pump 25 is controlled so that the carbon monoxide concentration in the treated gas G2 reaches 5ppm, a difference occurs in the amount of oxygen supplied to the treated gas G1 in accordance with the carbon monoxide concentration of the treated gas G1, specifically, a difference occurs in the power consumption of the air pump 25. Table 1 below shows the results of measuring the power consumption of the air pump 25 for 2 types of contact time.

(Table 1)

Contact time	Constitution A of the present invention	Comparative constitution B
			8.7 seconds	0.1W	0.4W
4.4 seconds	0.7W	1.6W

As the contact time is longer, the gas amount is small and the load is low, and the power consumption is reduced. In particular, when the contact time is 8.7 seconds, the conversion rate is very high in the case of the configuration a of the present invention, and therefore, the value is an immeasurable value. From this, it is understood that the use of the apparatus 1 of the present invention significantly contributes to the improvement of the power generation efficiency of the fuel cell, because the combustion of carbon monoxide in the carbon monoxide selective oxidizer 24 is reduced and the combustion of hydrogen is significantly reduced. It is also found that even in a situation where the load on the fuel cell is large (a situation where the contact time is short), it is effective to reduce the power consumption. Further, in the facility constituting the solid polymer fuel cell power generation system, since the oxidation reaction (heat generation reaction) directly occurs in the carbon monoxide selective oxidizer in addition to the catalyst, the catalyst life is limited, and in order to achieve a life of 4 ten thousand hours or 9 ten thousand hours, it is necessary to increase the size of the carbon monoxide selective oxidizer to a size more than necessary, and if the facility is used in combination with the apparatus 1 of the present invention, the reaction amount is extremely reduced, so that the size and cost of the carbon monoxide selective oxidizer can be reduced.

Other embodiments of the apparatus and method of the present invention are described below.

<1>In the above embodiment, a copper-zinc-based catalyst (Cu/Zn catalyst) is assumed as the No. 1 catalyst, and Pt/CeO is assumed₂The catalyst was the 2 nd catalyst, but any combination of the 1 st catalyst and the 2 nd catalyst described below, i.e., the 1 st catalyst and the 2 nd catalyst were carbon monoxideThe shift catalyst, the 1 st catalyst has a characteristic that the higher the carbon dioxide concentration in the supplied reaction gas is, the lower the carbon monoxide conversion rate is when the carbon monoxide concentration and the reaction temperature in the supplied reaction gas are constant (that is, the property that carbon dioxide poisons the 1 st catalyst and lowers the catalytic activity), and the degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the 2 nd catalyst is smaller than the degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the 1 st catalyst, and the effects of the present invention can be exhibited even in addition to the catalysts exemplified in the above embodiment. As the 2 nd catalyst, even Pt/CeO₂Catalysts other than catalysts, e.g. the same platinum group catalyst, with cerium oxide (CeO) as the carrier₂) Other catalyst, or noble metal catalyst other than platinum, in which the No. 2 catalyst is CO-selective than the No. 1 catalyst₂The effects of the present invention can be exhibited even when the resistance to poisoning is high. Further, instead of constituting the 2 nd catalyst layer 4 by one kind of the 2 nd catalyst, the 2 nd catalyst layer 4 may be constituted, for example, by providing two or more kinds of the 2 nd catalysts.

<2>In the above experimental apparatus for verifying the effect of the present invention, since the total amount of the catalysts of the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 is 5cc or less, a case will be described in which the reaction tube 2 housing the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 is installed in an electric furnace or a constant temperature bath, and the temperature in the reaction tube 2 is controlled to a constant temperature. However, the reaction tube 2 may not be provided in the electric furnace or the thermostatic bath, and the adiabatic control may be performed by adjusting the temperature of the reaction gas before the treatment fed into the reaction tube 2 to control the reaction temperatures of the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 together. This adiabatic control is a temperature control method applied when the number of catalysts of the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 is large in order to increase the processing capacity and the apparatus of the present invention is large in size. In this adiabatic control, since the carbon monoxide shift reaction is an exothermic reaction, the reaction temperature in the reaction tube 2 becomes higher toward the downstream side, and then becomes higher toward the downstream sideNear equilibrium, the temperature rise gradually saturates. Therefore, the reaction temperature in the reaction tube 2 is not maintained at a constant temperature unlike the case of the experimental apparatus, and the reaction gas passing through the 1 st catalyst layer 3 flows into the 2 nd catalyst layer 4 at a temperature in this state, so that the conditions are the same as those of the experimental apparatus with respect to the 1 st catalyst on the downstream side of the 1 st catalyst layer 3 and the 2 nd catalyst on the upstream side of the 2 nd catalyst layer 4. Therefore, even when a large amount of each catalyst is contained in the 1 st catalyst layer 3 and the 2 nd catalyst layer 4, CO on the downstream side of the 1 st catalyst layer 3₂The effect of the present invention obtained by replacing the portion of the 1 st catalyst poisoned by carbon dioxide with the 2 nd catalyst in the region of high concentration was the same as in the case of the above experimental apparatus.

<3> in the above embodiment, it is assumed that the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 are formed in the same reaction tube 2 as shown in fig. 1, but as shown in fig. 15, it is also a preferable embodiment to form the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 in different reaction tubes 2a, 2b, respectively, and connect the 2 reaction tubes 2a, 2b in series. In this case, it is easy to control the reaction temperatures in the 1 st catalyst layer 3 and the 2 nd catalyst layer 4, respectively. Therefore, the optimal reaction temperatures for the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 can be adjusted according to the carbon monoxide concentration and the carbon dioxide concentration of the respective injected gases to be treated.

<4>In the above embodiment, a copper-zinc-based catalyst (Cu/Zn catalyst) is assumed as the No. 1 catalyst, and Pt/CeO is assumed₂As the 2 nd catalyst, even if the 1 st catalyst and the 2 nd catalyst are the same catalyst (for example, copper zinc based catalyst) as long as the catalyst is configured such that the reaction temperature can be independently controlled for each of the 1 st catalyst layer 3 and the 2 nd catalyst layer 4 (for example, configuration as shown in fig. 15), the lowering of the carbon monoxide conversion rate with respect to the increase of the carbon dioxide concentration in the supplied reaction gas in the 2 nd catalyst can be made by performing control such that the reaction temperature of the 2 nd catalyst on the downstream side is set higher than the reaction temperature of the 1 st catalystThe degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the 1 st catalyst is smaller, and the effect of the present invention can be exhibited. For example, the above effects can be achieved by controlling the reaction temperature of the 1 st catalyst (copper zinc based catalyst) on the upstream side to 160 ℃ and the reaction temperature of the 2 nd catalyst (copper zinc based catalyst) on the downstream side to 200 ℃ or higher. This can be confirmed from the experimental results of fig. 6(a), 7 and 8. When the 1 st catalyst and the 2 nd catalyst use the copper zinc-based catalyst, referring to the experimental results of fig. 7 and 8, it is understood that: the higher the carbon dioxide concentration in the process gas passing through the upstream-side 1 st catalyst, the higher the reaction temperature of the 2 nd catalyst is set, whereby CO in the 2 nd catalyst can be suppressed₂Poisoning. Further, as is clear from the experimental results of fig. 7, by setting the reaction temperature of the 2 nd catalyst to a temperature higher than 200 ℃, CO can be further suppressed₂Poisoning. In the case where the 1 st catalyst and the 2 nd catalyst are constituted by the same catalyst, as described above, according to the idea of the conventional equilibrium theory, since the reaction temperature is low as described above, it is advantageous for the conversion of carbon monoxide, and therefore, the reaction temperature on the downstream side is generally set lower than that on the upstream side₂Poisoning can instead seek to improve the carbon monoxide conversion.

In order to confirm the effects of the above-described other embodiments in which the reaction temperature of the downstream-side 2 nd catalyst is set to be higher than the reaction temperature of the 1 st catalyst, experiments were carried out in the following manner. With regard to the configuration of the catalyst layer in the reaction tube 2, the carbon monoxide concentration in the treated gas G1 was measured with 3 catalyst layer configurations, i.e., the configuration of the present invention E and F in which the 1 st catalyst was used on the upstream side and the 2 nd catalyst was used on the downstream side in the same manner as in the apparatus 1 of the present invention and the reaction temperatures of the 1 st catalyst and the 2 nd catalyst were independently controlled with the configuration shown in fig. 14, and the comparative configuration B in which the 1 st catalyst was used in its entirety. In the constitution of 3 catalyst layers1 the catalyst used was a copper-zinc catalyst. Catalyst No. 2 in inventive configuration E, the same copper-zinc-based catalyst as that of catalyst No. 1 was used, and in inventive configuration F, Pt/CeO with a platinum loading of 10 wt% was used₂A catalyst. In addition, for each of the above configurations, gas #2 was supplied at a flow rate of 83.4 cc/min. The carbon monoxide concentration in the treated gas G1 at a reaction temperature of 160 ℃ constituting B was compared to 1.88 vol%. In contrast, in configuration E of the present invention, the carbon monoxide concentration in the treated gas G1 at 160 ℃ was set to be the same as that in configuration B, and was reduced compared to configuration B, with the reaction temperature of the 1 st catalyst being 1.45 vol% at 220 ℃ and 1.33 vol% at 250 ℃ respectively for the 2 nd catalyst. From this, it was found that even if the 1 st catalyst and the 2 nd catalyst are the same copper-zinc-based catalyst, the carbon monoxide conversion rate can be improved by performing control to set the reaction temperature of the 2 nd catalyst on the downstream side higher than the reaction temperature of the 1 st catalyst. Furthermore, the 2 nd catalyst was changed from the copper-zinc based catalyst to Pt/CeO₂In the present invention configuration F of the catalyst, the carbon monoxide concentration in the treated gas G1 was 1.01 vol% at the reaction temperature of the 1 st catalyst of 160 ℃ and the reaction temperature of the 2 nd catalyst of 220 ℃, which was further reduced as compared with the configuration E of the present invention in which the 2 nd catalyst was a copper-zinc-based catalyst. This means that even in the case where the reaction temperature of the 2 nd catalyst is set to be higher than that of the 1 st catalyst, by using Pt/CeO₂The catalyst 2 is a catalyst which can further improve the conversion rate of carbon monoxide.

Industrial applicability

The present invention is applicable to a carbon monoxide shift converter and a method for converting carbon monoxide contained in a reaction gas into carbon dioxide and hydrogen by reacting the carbon monoxide with steam, and is particularly useful for reducing the concentration of carbon monoxide in a reformed gas used as a fuel source for a fuel cell or the like.

Claims

1. A carbon monoxide shift device characterized by reacting carbon monoxide contained in a reaction gas with steam to convert the carbon monoxide into carbon dioxide and hydrogen,

the shift catalyst layer is divided into at least two stages, i.e., an upstream side and a downstream side, and the 1 st catalyst is provided on the upstream side and the 2 nd catalyst is provided on the downstream side, respectively,

the 1 st catalyst is a copper-zinc catalyst, the 2 nd catalyst is a noble metal catalyst,

the 1 st catalyst has a characteristic that the higher the carbon dioxide concentration in the supplied reaction gas is, the lower the carbon monoxide conversion rate is when the carbon monoxide concentration in the supplied reaction gas and the reaction temperature are constant,

the degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the 2 nd catalyst is smaller than the degree of decrease in the carbon monoxide conversion rate with respect to the increase in the carbon dioxide concentration in the supplied reaction gas in the 1 st catalyst.

2. The carbon monoxide shift device according to claim 1, wherein the 2 nd catalyst is a platinum-based catalyst, and the carrier of the 2 nd catalyst is cerium oxide.

3. The carbon monoxide shift device according to claim 1, wherein the volume of the 2 nd catalyst is equal to or less than the volume of the 1 st catalyst.

4. The carbon monoxide shift device according to any one of claims 1 to 3, wherein the reaction temperatures of the 1 st catalyst and the 2 nd catalyst are controlled together.

5. The carbon monoxide shift device according to any one of claims 1 to 3, wherein the reaction temperatures of the 1 st catalyst and the 2 nd catalyst are independently controlled.

6. A carbon monoxide shift device characterized by reacting carbon monoxide contained in a reaction gas with steam to convert the carbon monoxide into carbon dioxide and hydrogen,

the 1 st catalyst and the 2 nd catalyst have the same composition and structure,

the respective reaction temperatures of the 1 st catalyst and the 2 nd catalyst are independently controlled so that a degree of decrease in the carbon monoxide conversion rate with respect to an increase in the carbon dioxide concentration in the supplied reaction gas in the 2 nd catalyst becomes smaller than a degree of decrease in the carbon monoxide conversion rate with respect to an increase in the carbon dioxide concentration in the supplied reaction gas in the 1 st catalyst.

7. The carbon monoxide shift converter according to claim 6, wherein the 1 st catalyst and the 2 nd catalyst are copper-zinc-based catalysts.

8. A carbon monoxide shift conversion method characterized by reacting carbon monoxide contained in a reaction gas with steam to convert the carbon monoxide into carbon dioxide and hydrogen,

the shift reaction step is divided into at least 2 consecutive shift reaction steps, the 1 st shift reaction step on the upstream side uses the 1 st catalyst, and the 2 nd shift reaction step on the downstream side uses the 2 nd catalyst, wherein,

9. The carbon monoxide shift method as recited in claim 8, wherein the 2 nd catalyst is a platinum-based catalyst, and the carrier of the 2 nd catalyst is cerium oxide.

10. The carbon monoxide shift process according to claim 8, wherein the volume of the 2 nd catalyst is equal to or less than the volume of the 1 st catalyst.

11. The carbon monoxide shift process according to any one of claims 8 to 10, wherein the reaction gas passed through the 1 st catalyst is directly fed to the 2 nd catalyst without adjusting the temperature thereof.

12. The carbon monoxide shift process according to any one of claims 8 to 10, wherein the reaction temperatures of the 1 st catalyst and the 2 nd catalyst are independently controlled.

13. A carbon monoxide shift conversion method characterized by reacting carbon monoxide contained in a reaction gas with steam to convert the carbon monoxide into carbon dioxide and hydrogen,

14. The carbon monoxide shift conversion process according to claim 13, wherein the 1 st catalyst and the 2 nd catalyst are copper-zinc-based catalysts.

15. A hydrogen production apparatus is characterized by comprising: a carbon monoxide shift converter as set forth in any one of claims 1 to 3 and 6, and a carbon monoxide selective oxidizer for reducing the concentration of carbon monoxide in a gas treated by the carbon monoxide shift converter by selective oxidation.

16. A hydrogen production apparatus is characterized by comprising: the carbon monoxide shift converter according to claim 4, and a carbon monoxide selective oxidizer for reducing the concentration of carbon monoxide in a gas treated by the carbon monoxide shift converter by selective oxidation.

17. A hydrogen production apparatus is characterized by comprising: the carbon monoxide shift converter according to claim 5, and a carbon monoxide selective oxidizer for reducing the concentration of carbon monoxide in a gas treated by the carbon monoxide shift converter by selective oxidation.