JP2018135262A - Method of producing hydrogen, and cerium oxide catalyst for producing hydrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing hydrogen using a hydrogen production catalyst, excellent in steam modification and dry modification even in the presence of hydrogen sulfide.SOLUTION: The method of producing hydrogen comprises subjecting hydrocarbon in a gas to be treated to at least one reaction of steam modification reaction and dry modification reaction by contacting the gas to be treated containing hydrocarbon, 500 ppm or more of hydrogen sulfide, and at least any one of steam and carbon dioxide with a cerium oxide catalyst having a ratio occupied by total rare earth oxide (TREO) in a total composition of the catalyst converted in terms of oxide of 95.0% or more by mass ratio in terms of oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing hydrogen by steam reforming or dry reforming of hydrocarbon gas, and a cerium oxide catalyst for producing hydrogen.

  2015 is positioned as the first year of hydrogen, and expectations for the use of hydrogen energy are growing in Japan. With the commercialization of fuel cell vehicles, the demand for hydrogen is expected to increase continuously in the future, and the development of a method for producing hydrogen by a low cost and low environmental load method is required.

  In the method of producing hydrogen from hydrocarbons typified by methane, there are two major issues that should be emphasized from the viewpoint of cost and environmental burden. The first problem is that the reaction gas needs to be heated to about 800 ° C. The reaction for reforming hydrocarbons to hydrogen and carbon monoxide with water vapor or carbon dioxide is an endothermic reaction, and it is difficult to advance the reaction unless the temperature is high. The second problem is that the amount of carbon dioxide generation increases when the entire process is considered. When hydrogen is produced by reforming fossil fuel methane, the amount of carbon dioxide emissions increases by the amount of energy consumed during hydrogen production, compared to the case where methane is used as fuel as it is. .

Technological development is underway to solve the above two problems.
For example, in the method of reforming the coke oven gas generated from the coke oven in the iron making process and producing hydrogen, the high temperature coke oven gas released from the coke oven is brought into contact with the catalyst as it is to increase the temperature of the gas. Necessary energy can be saved (see, for example, Patent Documents 1 to 4 below). In addition, when methane in biogas is used as a raw material, it is not necessary to use hydrocarbons derived from fossil fuels, so that it is possible to produce hydrogen without increasing carbon dioxide emissions throughout the process. It becomes possible. However, since both coke oven gas and biogas contain hydrogen sulfide, and the concentration of such hydrogen sulfide often exceeds 1000 ppm, attempts have been made to suppress a decrease in catalytic activity in the presence of hydrogen sulfide. Yes. For such attempts, many report examples relating to a catalyst containing nickel, for example, are known (see, for example, Patent Documents 1 to 4 below).

  Against this background of technology trends, some research groups are studying how to generate hydrogen by steam reforming the gas to be treated containing methane using a catalyst mainly composed of cerium oxide. Although it has been reported that cerium oxide exhibits high catalytic activity when the hydrogen sulfide concentration is less than 500 ppm, it has been reported that the catalytic activity gradually decreases in the region where the hydrogen sulfide concentration is 500 ppm or more (the following non-reactive properties). (See Patent Literatures 1 and 2.) Further, it has been confirmed that cerium oxide and hydrogen sulfide react with each other to produce cerium sulfate in a region where the hydrogen sulfide concentration is 50 ppm or more, and the generation of such cerium sulfate is a decrease in activity in the presence of high concentration hydrogen sulfide. This is presumed to be the cause (see Non-Patent Document 1 below).

JP 2004-000900 A JP 2004-209408 A JP 2007-237066 A JP2013-237049A

N. Laosiripojana, S.M. Charojrochkul, P.A. Kim-Lohsonton, and S.K. Assabumrungrat, “Role and advantages of H2S in catalytic steam reforming over nanoscale CeO2-based catalysis,” 2010, 276 (January of Catalysis, 2010). 6-15. A. Kaddouri, and B.B. Beguin, “Methane steam reforming in the absence and presence of H2S over Ce0.8Pr0.2O2-δ, Ce0.85Sm0.15O2-δ and Ce0.9Gd0.1O2-δ201, FCS . 22-27. (Metal Society of Japan), “Metal Physical Chemistry”, 1992, p. 73. Y. Lai. George, “High-temperature corrosion and materials applications”, ASM International, 2007. R. M.M. Ferrizz, R.A. J. et al. Gorte, and J.M. M.M. Vohs, “Determining the Ce2O2S-CeOx phase boundary for conditions and related to adoption and catalysis”, Applied Catalysis B: Environmental 3, 200. 273-280. Edited by Japan Aromatic Industry Association, “Aromatic and Tar Industrial Handbook”, Japan Aromatic Industry Association, 2000.

  Thus, it is considered that the technology for producing hydrogen by steam reforming or dry reforming a gas to be treated containing hydrogen sulfide will become more important in the future. However, a catalyst that achieves both high stability and activity under conditions of hydrogen sulfide concentration of 500 ppm or more and a method for using such a catalyst have not been reported so far.

  Further, according to the study by the present inventors, not only the nickel-containing catalyst developed for coke oven gas but also the catalyst mainly composed of cerium oxide can be industrially used in the reported performance. Have difficulty. Therefore, a catalyst that exhibits high steam reforming activity or dry reforming activity even in the presence of a high concentration of hydrogen sulfide and further exhibits high stability has been eagerly desired.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide hydrogen using a reforming catalyst that is excellent in steam reforming and dry reforming even in the presence of hydrogen sulfide. And a cerium oxide catalyst for hydrogen production.

  The present inventor further investigated the prior art related to the catalytic reaction in the presence of hydrogen sulfide, and predicted that cerium oxide could exhibit high catalytic activity and stability even under conditions where the hydrogen sulfide concentration was 1000 ppm or more. Although the previous study reported that the catalyst activity gradually decreases in the hydrogen sulfide concentration range of 500 ppm or more (see Non-Patent Document 1 above), the reason for the above prediction is as follows. It is as follows.

  According to a report on the steam reforming reaction using cerium oxide in the presence of hydrogen sulfide (see Non-Patent Document 1 above), even after a relatively low concentration of 50 ppm hydrogen sulfide, the reaction time is relatively short. It has been confirmed that a large amount of cerium sulfate is produced over time. Further, it has been confirmed that the catalytic activity is lowered by gradually changing the produced cerium sulfate to cerium sulfide. However, the present inventor investigated the hydrogen-water vapor, hydrogen sulfide-hydrogen Ellingham diagram, and the potential diagram of cerium oxide (see Non-Patent Documents 3 to 5 above), and compared them with the conditions reported above. As a result, it was concluded from the thermodynamic point of view that it is unlikely that a large amount of cerium sulfate is produced under the reaction conditions reported above. Therefore, the present inventor re-examined the contents of the previous research. As a result, in the X-ray diffraction spectrum in Non-Patent Document 1, a peak not attributed to cerium oxide was observed even in the unreacted cerium oxide catalyst. Furthermore, it was confirmed that a part of the peak not attributed to cerium oxide was detected at a position corresponding to calcium oxide or iron oxide. Calcium oxide and iron oxide are known to produce more stable sulfides than cerium oxide. From the above, the present inventor has predicted that the resistance of cerium oxide to hydrogen sulfide will decrease under the condition that a small amount of impurities is contained in cerium oxide.

  Based on this expectation, the present inventor conducted a test using a high-purity cerium oxide catalyst having a low content of calcium oxide, iron oxide and the like, and as a result, even in a reaction gas containing 2000 ppm of hydrogen sulfide, cerium sulfate. Was found to produce almost no.

  Conventionally, the steam reforming reaction using a cerium oxide catalyst has only been known as a methane steam reforming reaction, which is a reaction that hardly causes carbon deposition. However, the present inventor uses the present invention described in detail below to include calcium oxide, iron oxide, and the like in the reforming reaction of 1-methylnaphthalene (carbon number 11), which is one of the representative components of tar. If a small amount of high purity and appropriate cerium oxide catalyst is used, although depending on conditions such as the steam carbon ratio (S / C), carbon deposition can be suppressed, and further, the crystal structure of the catalyst can be avoided. I also found that I can do it.

Furthermore, in the reforming reaction of hydrocarbon gas, the ratio of carbon dioxide to carbon in hydrocarbon (CO ₂ / C) can be appropriately selected also by the dry reforming reaction that uses carbon dioxide instead of steam. For example, it has been found that hydrogen production is possible while suppressing carbon deposition.

Such contents are as shown in the examples described later. The inventor of the present invention has made the present invention based on the above knowledge.
The gist of the present invention completed based on such findings is as follows.

(1) When the total composition of the catalyst is converted to oxide, the proportion of total rare earth oxide (TREO) is 95.0% or more in terms of oxide-converted mass ratio. Then, a gas to be treated containing hydrocarbon, 500 ppm or more of hydrogen sulfide, and at least one of water vapor and carbon dioxide is brought into contact, and the hydrocarbon in the gas to be treated is subjected to a steam reforming reaction or a dry process. A method for producing hydrogen, wherein hydrogen is produced by reacting in at least one of the reforming reactions.
(2) The hydrogen according to (1), wherein the ratio of the total rare earth oxide in the cerium oxide catalyst when the total composition of the catalyst is converted to oxide is 99% or more by mass ratio in terms of oxide. Manufacturing method.
(3) In the cerium oxide catalyst, the proportion of cerium oxide when the total composition of the catalyst is converted to oxide is 90.0% or more by mass ratio in terms of oxide, (1) or (2) A method for producing hydrogen as described in 1. above.
(4) The cerium oxide catalyst contains at least one of iron oxide, aluminum oxide, calcium oxide, barium oxide, nickel oxide, zirconium oxide, and niobium oxide, and the content of the iron oxide is iron oxide ( III) The mass ratio in terms of mass is 3% or less, and the contents of the aluminum oxide, the calcium oxide, the barium oxide, the nickel oxide, the zirconium oxide, and the niobium oxide are mass ratios in terms of oxide. The method for producing hydrogen according to any one of (1) to (3), wherein each is 5% or less.
(5) The method for producing hydrogen according to any one of (1) to (4), wherein the concentration of hydrogen sulfide contained in the gas to be treated is 500 ppm or more and 3000 ppm or less.
(6) The method for producing hydrogen according to any one of (1) to (5), wherein the gas to be treated contains tar.
(7) The method for producing hydrogen according to any one of (1) to (6), wherein the specific surface area of the cerium oxide catalyst is 10 m ² / g or more and 100 m ² / g or less.
(8) The hydrogen according to any one of (1) to (7), wherein when the steam reforming reaction proceeds, a steam carbon ratio of the gas to be treated is 0.8 or more and 3.0 or less. Manufacturing method.
(9) When the dry reforming reaction proceeds, the molar ratio of carbon dioxide in the gas to be treated and carbon atoms contained as hydrocarbons is 1.0 or more and 3.0 or less, (1) The manufacturing method of hydrogen as described in any one of-(8).
(10) The method for producing hydrogen according to (8) or (9), wherein the gas to be treated is coke oven gas.
(11) When the total composition of the catalyst is converted to oxide, the proportion of CeO ₂ is 90.0% or more in terms of mass ratio in terms of oxide, and the total rare earth oxide (TREO) A cerium oxide catalyst for hydrogen production, the proportion of which is 95.0% or more in terms of mass ratio in terms of oxide, and the specific surface area is 10 m ² / g or more and 100 m ² / g or less.
(12) It contains at least one of iron oxide, aluminum oxide, calcium oxide, barium oxide, nickel oxide, zirconium oxide, and niobium oxide, and the content of the iron oxide is a mass ratio in terms of iron (III) oxide. The content of the aluminum oxide, the calcium oxide, the barium oxide, the nickel oxide, the zirconium oxide, and the niobium oxide is a mass ratio in terms of oxide, each being 5% or less. The cerium oxide catalyst for hydrogen production as described in (11).
(13) The cerium oxide catalyst for hydrogen production according to (11) or (12), wherein a ratio of the CeO ₂ is 99.0% or more in terms of mass ratio in terms of oxide.

  As described above, according to the present invention, even when high concentration hydrogen sulfide of 500 ppm or more is contained in the gas to be treated, reforming of at least one of the steam reforming reaction and the dry reforming reaction is performed. Hydrogen can be produced by the reaction.

It is a XRD measurement result of the steam reforming catalyst shown in the Example.

Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Hereinafter, with respect to the method for producing hydrogen according to the present invention, details of the catalyst mainly composed of cerium oxide, details of applicable gas to be treated, and specific embodiments of application, etc. will be described. .

(Catalyst based on cerium oxide)
First, a catalyst mainly composed of cerium oxide according to the present embodiment (hereinafter simply abbreviated as “cerium oxide catalyst”) will be described in detail.
Cerium oxide has been manufactured in various ways by many companies, and can be purchased by arbitrarily selecting the manufacturing method, purity, specific surface area, particle size, and the like. Therefore, in the cerium oxide catalyst according to the present embodiment, the content of cerium oxide is not particularly limited. However, as a result of verification of various products sold by the present inventor as cerium oxide, it was confirmed that even a low-purity product contains 50% or more of cerium oxide by mass ratio. Therefore, in the cerium oxide catalyst according to the present embodiment, it is preferable to use an oxide catalyst containing 50% or more of cerium oxide by mass ratio because of easy availability.

  In addition to purchasing such cerium oxide as an industrial product, this embodiment can be applied to the present embodiment by a known manufacturing method such as a coprecipitation method, a citric acid method, or a thermal decomposition method using a reagent such as cerium nitrate or cerium carbonate. It is possible to produce a cerium oxide catalyst that can be used in such a method for producing hydrogen. Regardless of which production method is used, it is preferable to perform heat treatment at a temperature equal to or higher than the reaction temperature in advance before starting the reaction to suppress thermal denaturation during the reaction.

  In general, cerium oxide has only one kind of stable crystal structure, and it is difficult to control the plane orientation of fine particles by a technique that can be easily mass-produced. Therefore, it is sufficient to pay attention to the purity, specific surface area, and particle size among the physical property values of cerium oxide to be used. Of the three physical property values of purity, specific surface area, and particle size, the ratio of purity and specific surface area is large in the degree of influence when hydrogen is produced by steam reforming reaction or dry reforming reaction.

<Purity of cerium oxide>
As for the purity of cerium oxide, it is preferable to use a high-purity one. However, a lower-purity one tends to be less expensive, so if the following criteria are met, a lower-purity one can be used if necessary. It doesn't matter. As will be described below, since the allowable concentration varies depending on the element contained as an impurity, analyzing the composition of the candidate catalyst in advance is helpful when selecting the catalyst to be actually used.

  For example, lanthanoid series elements such as lanthanum oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, and gadolinium oxide can be mixed in large amounts without any problem. For example, the molar ratio of metal elements to cerium oxide Even when 10% of the lanthanoid oxide is mixed, the same level of catalytic activity and stability can be obtained (a specific example will be shown in the examples described later for the case where 10% of lanthanum oxide is mixed). .)

  On the other hand, in the study conducted by the present inventors, when any one of iron oxide, aluminum oxide, calcium oxide, barium oxide, nickel oxide, zirconium oxide and niobium oxide is mixed with cerium oxide, the catalytic activity is low. Declined.

  From the above results, it is important to limit the content in cerium oxide for elements other than the lanthanoid series. The allowable content in cerium oxide varies depending on the type of oxide. Specifically, the content of iron oxide is preferably 3% or less, and more preferably 1% or less, in terms of mass ratio in terms of iron (III) oxide. As for aluminum oxide, calcium oxide, barium oxide, nickel oxide, zirconium oxide, and niobium oxide, all are preferably 5% or less, more preferably 3% or less in terms of mass ratio in terms of oxide, and 1%. More preferably, it is as follows. In addition, when calculating the mass ratio in terms of oxide of each component in the catalyst in the present embodiment, the denominator corresponds to the total mass when all component compositions (total composition) in the catalyst are oxidized. is there. However, when gold, platinum and rhodium are contained in the catalyst, these are not converted into oxides but added to the denominator as masses in terms of metals.

  In the case of a commercial product, the purity of cerium oxide is often expressed in terms of total rare earth oxide (TREO). This value often means the total amount of lanthanoid series oxides. Specifically, it is calculated as the sum of cerium (IV) oxide and another lanthanoid oxide converted to trivalent. As described above, even if a lanthanoid series element is included, the catalyst performance does not deteriorate. Therefore, a catalyst having a purity sufficient to exhibit catalytic activity can be selected using the purity in terms of TREO as an index. . Specifically, for the cerium oxide catalyst, the purity in terms of TREO calculated from the mass ratio of the total composition of the catalyst expressed in terms of oxide, determined by the procedure shown later, is 95.0% or more by mass ratio. is necessary. Moreover, the purity in terms of TREO in the cerium oxide catalyst is more preferably 99% or more.

Further, when the total composition of the catalyst is converted to oxide, the proportion of CeO ₂ is preferably 90.0% or more in terms of mass ratio in terms of oxide. By setting the ratio of CeO ₂ to 90.0% or more, it becomes possible to efficiently perform steam reforming or dry reforming of hydrocarbons in the gas to be treated. The proportion of CeO ₂ is more preferably 99.0% or more. By setting the ratio of CeO ₂ to 99.0% or more, it becomes possible to further reduce the amount of impurities other than the lanthanoid series.

  When examining the composition of these compounds, in order to avoid changes in the composition of the catalyst during the process of raising the temperature to the reaction temperature, perform an analysis after performing a heat treatment at a temperature higher than the reaction temperature in advance. Is preferred. Although any method can be used for the composition analysis of the sample, the X-ray fluorescence analysis is simple for performing the component analysis with the accuracy required for carrying out the present invention. However, when the compound contains light elements (excluding hydrogen, helium, nitrogen, and oxygen) up to the second period of the periodic table, accurate component analysis becomes difficult by X-ray fluorescence analysis. Therefore, when a more accurate composition analysis is desired, an ICP emission analysis may be performed. However, if the measured value differs due to the difference in analysis method, the result of ICP emission analysis is positive.

  However, in any of the above measurements, the water content cannot be measured, so the hydrogen and oxygen contents cannot be measured. Further, measurement of nitrogen (that is, determination of nitride) is difficult, and further, helium cannot be measured.

  When light elements up to the second period of the periodic table (excluding hydrogen, helium, and oxygen) are not included, the same result is obtained within the measurement error range regardless of which measurement method is used. In any measurement method, since the valence and existence state of each element cannot be determined, the mass ratio obtained by converting each element into an oxide is handled as the composition of each catalyst.

  Further, since it is difficult to determine the amount of nitrogen, all nitrides are calculated in terms of oxides. At this time, the oxide is converted into a stable oxide in a standard state, and when there are a plurality of stable oxides, the oxide is converted into an oxide having the largest oxidation number among them. In particular, for lanthanoid series elements, cerium is converted to cerium (IV) oxide, and other elements are converted to trivalent oxides, and the total nitride content is calculated based on these converted values. Calculate as the sum.

  In addition, gold, platinum, and rhodium are not converted to oxides but are converted to metals because it is difficult to select a stable oxide.

  In this way, each element is converted into an oxide (however, as described above, some elements are converted into metal), and further converted into a mass ratio using the atomic weight described in the periodic table prepared by the Chemical Society of Japan. Can be determined. By determining the total composition of the catalyst in the above procedure, there can be a certain dissociation between the actual composition and the calculated composition.

  However, it is generally difficult to determine an accurate composition including the oxidation number of each element, and it is not practical to apply it to all the catalysts used in this embodiment. Furthermore, in the vicinity of the reaction temperature used in the steam reforming reaction or dry reforming reaction according to the present embodiment, moisture is released, and it is difficult to think of remaining helium, and nitride reacts with steam to change into an oxide. I think that. Therefore, the dissociation between the composition estimated by the above procedure and the composition under actual reaction conditions is small.

  From the above, it is assumed that the total composition of the catalyst in the present embodiment is the total composition in terms of oxide determined in the above-described procedure (however, as described above, some elements are converted to metal). In addition, about the above-mentioned procedure, the function which calculates automatically is attached to many commercial analyzers, and can be performed simply.

  When calculating the TREO-converted purity, first, the total composition of the catalyst is analyzed according to the above procedure, and further the mass in terms of oxide (however, as described above, some elements are converted to metal). By converting to a ratio, the purity in terms of TREO can be calculated as a mass ratio.

<Specific surface area of cerium oxide>
The specific surface area of cerium oxide is preferably as large as possible from the viewpoint of promoting the catalytic reaction, but the density of cerium oxide is as large as 7.3 g / cm ^3. The diameter needs to be very small. For example, in order to set the specific surface area to 100 m ² / g, it is necessary to reduce the primary particle diameter to about 8 nm. However, the reaction temperature is as high as about 800 ° C., which is much higher than that of cerium oxide, so it is very difficult to maintain the fine primary particle diameter as described above. Therefore, even when cerium oxide having a large specific surface area is used, the specific surface area is considered to be 100 m ² / g or less in a short time during the reaction.

On the other hand, when the specific surface area is too small, it has been confirmed that the catalytic activity is greatly reduced. The study of the present inventors, the specific surface area has it been confirmed that can decrease greatly the activity falls below the 3m 2 ^/ g is increased, when the 10 m 2 / ^g or more, regardless of the magnitude of the specific surface area The same catalytic activity was obtained. Therefore, the specific surface area of cerium oxide is preferably 3 m ² / g or more and 100 m ² / g or less, after being subjected to heat treatment at a temperature equal to or higher than the reaction temperature, and preferably 10 m ² / g or more and 100 m ² / g. The following is more preferable.

  Although any method can be used for measuring the specific surface area, it is convenient to use the BET measurement method using a nitrogen adsorption isotherm at the liquid nitrogen temperature. As described above, the cerium oxide catalyst that has been heat-treated at a temperature close to the reaction temperature is expected to have a small specific surface area, and it can be considered that the amount of fine pores decreases as the specific surface area decreases. In such a case, it is easy to obtain an appropriate measurement result by the BET method.

<Cerium oxide particle size>
Any particle size of cerium oxide can be used, and can be appropriately selected according to the utilization form of the catalyst. In the method for producing hydrogen according to this embodiment, if conditions such as the steam carbon ratio (S / C) are optimized, carbon deposition hardly occurs. Therefore, in addition to the fluidized bed reactor, the fixed bed reactor Is available. The catalyst is molded according to the dimensions of the reaction apparatus used at this time, the flow rate in the apparatus, etc., and a particle size that is easy to use at that time may be appropriately selected. For example, the shape of the molded particle is applicable to any shape such as a spherical shape, a cylindrical shape, a porous shape, and a clover shape. As a method for the molding process, any of an extrusion molding method, a rolling granulation method, or a compression molding method that is expensive but easily obtains high strength can be used.

(About treated gas)
Subsequently, the gas to be processed in the method for producing hydrogen according to the present embodiment will be described in detail.
In the method for producing hydrogen according to the present embodiment, a method of reacting hydrocarbons and steam in a gas to be treated containing hydrogen sulfide (steam reforming) or a hydrocarbon and carbon dioxide in the gas to be treated containing hydrogen sulfide. Is used (dry reforming). Therefore, each embodiment of the hydrogen sulfide concentration in the gas to be treated, the type of hydrocarbon, the amount of water vapor, and the amount of carbon dioxide is shown below.

<About hydrogen sulfide concentration>
The method for producing hydrogen according to the present embodiment can be applied as it is to a gas to be treated that does not contain hydrogen sulfide, but a concentration range of hydrogen sulfide concentration of 500 ppm or more, which has been conventionally considered to cause a decrease in activity. Shows particularly high catalytic activity. Therefore, in the method for producing hydrogen according to the present embodiment, the concentration of hydrogen sulfide contained in the gas to be treated is set to 500 ppm or more.

  In addition, the higher the hydrogen sulfide concentration, the more the catalyst activity tends to improve (see the examples below). Further, according to the study of the present inventors, the steam reforming reaction or the dry reforming reaction proceeds even when the method for producing hydrogen according to the present embodiment is applied to the gas to be treated having a hydrogen sulfide concentration of 3000 ppm. It is confirmed that the catalytic activity is exhibited even at a hydrogen sulfide concentration higher than this concentration. On the other hand, if the hydrogen sulfide concentration is too high, it causes corrosion of the device and increases the risk of gas leakage. From this viewpoint, in the method for producing hydrogen according to the present embodiment, the concentration of hydrogen sulfide is preferably 10,000 ppm or less, more preferably 3000 ppm or less, and further preferably 2000 ppm or less.

  Of the gas species to which the hydrogen production method according to this embodiment is applied, it is known that the biomass gasification gas of raw garbage has the highest hydrogen sulfide concentration. However, the normal hydrogen sulfide concentration is less than 3000 ppm. Therefore, in reality, it is considered that the hydrogen sulfide concentration of the gas to be treated hardly exceeds 3000 ppm.

  As a method for measuring the hydrogen sulfide concentration, it is easy to apply a method using a commercially available analyzer. When it is difficult to use a large analyzer and high-precision measurement is not required, the hydrogen sulfide concentration can be measured using a portable constant potential electrolytic diffusion hydrogen sulfide measuring instrument. In this type of analyzer, a commercial product that can measure with a measurement error of 25 ppm and a measurement concentration range of 0 to 3000 ppm is commercially available. If a more accurate measurement of the hydrogen sulfide concentration is required, gas chromatographic measurement can be used. In this type of analyzer, by using an appropriate calibration gas and dilution gas, it is possible to perform measurement with a measurement error of less than 3 ppm and a measurement concentration range of 0 to 3000 ppm. However, if the measured value of gas chromatography is different from that of the constant potential electrolytic diffusion hydrogen sulfide measuring instrument, the measurement result by gas chromatography is positive.

In addition, sulfur dioxide is known as a gas component containing sulfur other than hydrogen sulfide. A small amount of sulfur dioxide may be mixed in the gas to be treated containing a large amount of hydrogen sulfide. However, if the concentration of sulfur dioxide is lower than that of hydrogen sulfide, the Claus reaction (SO ₂ + 2H ₂ S → 3S + 2H ₂ O) proceeds near the reaction temperature, and further, the hydrogenation of sulfur following the Claus reaction (S + H ₂ → It is considered that sulfur dioxide is removed by the progress of H ₂ S). Even when sulfur dioxide is mixed with a gas not containing hydrogen sulfide, the effect on cerium oxide is slight if the concentration of sulfur dioxide is low. According to a test conducted by the present inventor, when a gas to be treated that does not contain hydrogen sulfide and contains 200 ppm of sulfur dioxide (hydrogen sulfide gas is 0 ppm) and cerium oxide are contacted at a reaction temperature of 800 to 900 ° C. It was also confirmed that no change was observed in the crystal structure of cerium oxide. As described above, the present invention can be applied even if sulfur dioxide is mixed in the gas to be treated. Here, in the method for producing hydrogen according to this embodiment, the sulfur dioxide is preferably mixed at a concentration of 200 ppm or less or a concentration of hydrogen sulfide or less.

<About the types of hydrocarbons>
Of the hydrocarbons that can be contained in the gas to be treated, the hydrocarbons that are the subject of the present invention are not limited to methane and 1-methylnaphthalene, but non-aromatic hydrocarbons having 11 or less carbon atoms, Aromatic hydrocarbons having 11 or less carbon atoms and tar components having 11 or more carbon atoms are included. The reason is as follows.

  First, methane is the smallest molecule among hydrocarbons, and it is known that the hydrogen generation reaction by the steam reforming reaction is difficult to proceed. The same applies to the dry reforming reaction. In general, methane is a molecule that hardly undergoes the reforming reaction. Therefore, by the method for producing hydrogen according to the present embodiment capable of proceeding with the steam reforming reaction or dry reforming reaction of methane, ethane, ethene, propane, propene, butane, butene, pentane, pentene, hexane, hexene , Non-aromatic hydrocarbons such as heptane, heptene, octane, octene, nonane, nonene, decane, decene, undecane, undecane, etc. can also be produced by steam reforming or dry reforming to produce hydrogen .

  When non-aromatic hydrocarbons are used, 1-methylnaphthalene is generally used because carbon precipitation is less likely to occur during both steam reforming and dry reforming compared to aromatic hydrocarbons. In addition, in the method for producing hydrogen according to this embodiment capable of preventing carbon deposition, carbon deposition can be prevented even when a non-aromatic hydrocarbon having 11 or less carbon atoms is used, and hydrogen production can be performed stably. It becomes possible.

  Note that non-aromatic hydrocarbons having 12 or more carbon atoms are easily pyrolyzed or oxidatively decomposed to produce compounds having 11 or less carbon atoms. Therefore, the method for producing hydrogen according to this embodiment is applied to non-aromatic hydrocarbons having 12 or more carbon atoms by selecting appropriate reaction conditions and pretreatment conditions for the gas to be treated. Is possible.

  Further, 1-methylnaphthalene is one of substances classified as tar. Tar is a generic name including a great number of substances, and examples of specific substances are described in the literature (for example, see Non-Patent Document 6 above). Many of the substances that fall under tar are those in which multiple aromatic rings are linked, or those aromatic rings with substituents, and those containing up to four aromatic rings are listed as tar components. ing. Among them, the substance having the highest content ratio is a substance having two aromatic rings, and 1-methylnaphthalene is a substance suitable for representing a tar component. Moreover, 1-methylnaphthalene has a structure in which a substituent is attached to an aromatic ring, and has characteristics of many other tar components. Therefore, the method for producing hydrogen according to this embodiment in which efficient hydrogen production has been confirmed by the steam reforming test and the dry reforming test using 1-methylnaphthalene can be applied to other tar components. . Also, since hydrocarbons containing only one aromatic ring are known to be generally more reactive than substances containing two aromatic rings, steam reforming tests and dry reforming using 1-methylnaphthalene are known. It is considered that the hydrogen production method according to the present embodiment, which has confirmed efficient hydrogen production by the quality test, can be similarly applied to aromatic hydrocarbons containing only one aromatic ring.

<About the amount of water vapor>
One feature of the method for producing hydrogen according to this embodiment is that carbon deposition on the catalyst is small. Therefore, in the method for producing hydrogen according to the present embodiment, the steam reforming reaction can be allowed to proceed even under conditions where the amount of steam is small compared to generally used reaction conditions. The present inventor, when represented by a steam carbon ratio (hereinafter sometimes abbreviated as “S / C”), which is a molar ratio between water vapor and carbon atoms contained as hydrocarbons, In the case of reaction, no carbon deposition occurs when S / C is 1.0 or more, and even when 1-methylnaphthalene is used, no carbon deposition occurs when S / C is 1.2 or more. It was confirmed that the obtained catalytic activity was obtained. On the other hand, when S / C was less than 0.8, it was confirmed that, in a reaction test using 1-methylnaphthalene, partial carbon deposition occurred and the activity gradually decreased. Therefore, in the method for producing hydrogen according to the present embodiment, the S / C of the gas to be processed is preferably set to 0.8 or more. On the other hand, the upper limit of S / C is limited by the cost of generating water vapor. In general, the higher the water vapor concentration is, the more difficult the carbon deposition is to occur and the reaction becomes more stable, but there is a problem that the cost for generating water vapor and raising the temperature to the reaction temperature is increased. From the above, in the method for producing hydrogen according to the present embodiment, the S / C of the gas to be processed is preferably set to 3.0 or less.

  In addition, compared with the carbon dioxide of the same density | concentration, water vapor | steam has the much higher effect which suppresses carbon precipitation. Therefore, when reforming hydrocarbons that are prone to carbon deposition in a mixed system in which steam and carbon dioxide are present in the gas to be treated, the steam reforming is achieved by increasing the water vapor concentration in the mixed system above the carbon dioxide concentration. It is recommended that the quality reaction progresses with priority. The total amount of water vapor is calculated as the sum of water vapor originally contained in the raw material gas (for example, coke oven gas or biogas) and water vapor supplied from the outside during the reforming reaction. Therefore, the supply source of water vapor is not important, and the amount of water vapor contained in the gas to be treated at the time of being subjected to the reaction in the catalyst layer is important.

<About the amount of carbon dioxide>
One feature of the method for producing hydrogen according to this embodiment is that carbon deposition on the catalyst is small. Therefore, even in a dry reforming reaction that generally tends to increase the amount of carbon deposition, the dry reforming reaction can be allowed to proceed while suppressing the amount of carbon deposition or hardly causing carbon deposition.

The inventor expresses the carbon dioxide carbon ratio (hereinafter sometimes abbreviated as “CO ₂ / C”), which is a molar ratio between carbon dioxide and carbon atoms contained as hydrocarbons. In the case of a methane reforming reaction, carbon deposition does not occur when CO ₂ / C is 1.0 or more, and carbon deposition occurs when CO ₂ / C is 2.0 or more even when 1-methylnaphthalene is used. It has been confirmed that the amount is reduced and stable catalytic activity is obtained. On the other hand, when CO ₂ / C is 1.0 or less, in the reaction test using 1-methylnaphthalene, it was confirmed that the carbon deposition amount increased and the activity decreased with the lapse of the reaction time. It was.

Therefore, in the hydrogen production method according to the present embodiment, particularly when hydrogen production is performed by a dry reforming reaction, the CO ₂ / C of the gas to be treated is 1.0 or more if the methane reforming reaction. When reforming hydrocarbons (particularly tars) having more carbon atoms than methane, CO ₂ / C is preferably greater than 1.0, It is more preferable.

On the other hand, the upper limit of CO ₂ / C is limited from the viewpoint of the temperature rise cost of the reaction gas and the composition of the product gas. In general, as the carbon dioxide concentration is higher, carbon deposition is less likely to occur, and the reaction becomes more stable. However, the introduction of carbon dioxide increases the total amount of the gas to be treated, causing a problem that the cost for raising the temperature to the reaction temperature increases. Further, as the concentration of carbon dioxide increases, unreacted carbon dioxide increases. This unreacted carbon dioxide remains in the product gas obtained by the reforming reaction as carbon dioxide gas after the dry reforming reaction. Since carbon dioxide is more difficult to remove from the product gas than water vapor, it is not preferable to perform the dry reforming reaction under the condition that excessive unreacted carbon dioxide remains from the viewpoint of the purity of the product gas.

From the above, in the method for producing hydrogen according to the present embodiment, the CO ₂ / C of the gas to be processed is preferably set to 3.0 or less. Further, it has been confirmed that the dry reforming reaction exhibits a higher reaction rate than the steam reforming reaction under conditions where no carbon deposition occurs. Thus, light hydrocarbons that are less susceptible to carbon precipitation, such as methane, ethane, propane, butane, pentane, hexane, ethene, propene, butene, pentene, hexene, methanol, ethanol, propanol, butanol, pentanol, hexanol, and When reforming these structural isomers, etc., by setting the carbon dioxide concentration higher than the water vapor concentration and allowing the dry reforming reaction to preferentially proceed, more efficient hydrogen production can be achieved. It becomes possible. The total amount of carbon dioxide is calculated as the sum of carbon dioxide originally contained in the raw material gas (for example, coke oven gas or biogas) and carbon dioxide supplied from the outside during the reaction. Therefore, the supply source of carbon dioxide is not important, and the amount of carbon dioxide contained in the gas to be treated at the time of being subjected to the reaction in the catalyst layer is important.

<Specific examples of gas to be treated>
Examples of the target gas to which the method for producing hydrogen according to the present embodiment can be applied include natural gas, coke oven gas, biogas, and biomass gasification gas. The coke oven gas before purification contains a high concentration of hydrogen sulfide and contains a large amount of tar, which is suitable as an application example of the method for producing hydrogen according to this embodiment. Biogas generated by anaerobic methane fermentation also contains carbon dioxide as an oxygen source, and hydrogen production efficiency is further increased by utilizing carbon dioxide in the gas. Moreover, since the biomass gasification gas generated by gasification of biomass contains both water vapor and carbon dioxide and is discharged at a high temperature, it is suitable as an application example of the method for producing hydrogen according to the present embodiment. These gases to be treated contain at least a small amount of water vapor and carbon dioxide. Further, even when a gas to be treated containing only one of water vapor and carbon dioxide is applied to the hydrogen production method of the present invention, due to the progress of the water vapor reforming reaction, the dry reforming reaction, and the water gas shift reaction. Then, a gas containing both water vapor and carbon dioxide is generated from the catalyst layer outlet. Therefore, even when a gas to be treated containing only one of water vapor and carbon dioxide is used, or when a gas containing both water vapor and carbon dioxide from the beginning is used as the gas to be treated, water vapor reforming is performed inside the catalyst layer. Both the quality reaction and the dry reforming reaction will proceed.

(About hydrogen production method using cerium oxide catalyst)
Subsequently, a method for producing hydrogen using the cerium oxide catalyst as described above will be described.
In the method for producing hydrogen according to the present embodiment, the gas to be treated is brought into contact with the cerium oxide catalyst as described above, and the hydrocarbon in the gas to be treated is subjected to steam reforming or dry reforming. The method of producing hydrogen by reforming at least one of the above.

  Here, the reaction temperature in the method for producing hydrogen according to the present embodiment is restricted by the reaction efficiency and the temperature raising cost. Both the steam reforming reaction and the dry reforming reaction of hydrocarbons are endothermic reactions, and a sufficient reaction rate cannot be obtained unless the reaction temperature is high. On the other hand, if the reaction temperature is too high, the energy cost required to raise the temperature of the reaction gas will increase. From the above, in the method for producing hydrogen according to this embodiment, the reaction temperature is preferably 650 ° C. or higher and 1000 ° C. or lower, more preferably 700 ° C. or higher and 950 ° C. or lower, and 700 ° C. or higher and 900 ° C. or lower. More preferably it is.

  The heating means for raising the reaction temperature between the cerium oxide catalyst and the gas to be treated to the above temperature range is not particularly limited, and a known heating means can be used. is there.

  As described above, the method for producing hydrogen according to the present embodiment has been made with a focus on the catalytic activity in the presence of hydrogen sulfide, and is a steam reformer that uses a gas to be treated containing a high concentration of hydrogen sulfide. It can be applied to quality reaction or dry reforming reaction. The hydrogen production method according to this embodiment is characterized by (1) using a catalyst mainly composed of cerium oxide as the steam reforming catalyst or dry reforming catalyst; and (2) A gas containing high-concentration hydrogen sulfide, hydrocarbons, and water vapor is used as a processing gas, and a gas containing high-concentration hydrogen sulfide, hydrocarbons, and carbon dioxide is used in the dry reforming reaction. To use. The method for producing hydrogen according to the present embodiment can realize a high catalytic activity and high stability, which have not been predicted in the past, with a catalyst mainly composed of cerium oxide, particularly in a region where the hydrogen sulfide concentration is 500 ppm or more. It is shown that. Specifically, conventionally, in the methane reforming reaction, the catalytic activity has been gradually decreased in the region where the hydrogen sulfide concentration is 500 ppm or more (see, for example, Non-Patent Document 1 above). In the method for producing hydrogen according to the present invention, by selecting an appropriate cerium oxide catalyst, it is possible to avoid a decrease in catalyst activity even in a region where the hydrogen sulfide concentration is 500 ppm or more, and to avoid a change in the crystal structure of the catalyst. Is.

  Hereinafter, the method for producing hydrogen according to the present invention will be specifically described with reference to experimental examples. However, the method for producing hydrogen according to the present invention is not limited in any way by the following experimental examples.

(Generation of various catalysts)
Various catalysts used in the experimental examples were produced by the following procedure.

<Catalyst A: Nickel-based catalyst>
A nickel-supported catalyst was prepared by a coprecipitation method.
More specifically, 1000 ml of pure water was put into a 2000 ml beaker and 500 ml of pure water was put into a 1000 ml beaker, and the temperature was raised to 60 ° C. while stirring with a magnetic stirrer. Weigh 13.30 g of nickel nitrate hexahydrate (Kanto Chemical, purity> 98.0%) and 105.51 g of magnesium nitrate hexahydrate (Wako Pure Chemical, purity> 99.0%). And dissolved in 1000 ml of pure water maintained at 60 ° C. In addition, 63.19 g of potassium carbonate (Kanto Chemical, purity> 99.5%) was weighed and dissolved in 500 ml of pure water maintained at 60 ° C. A 1000 ml solution in which nitrate was dissolved was stirred with a mechanical stirrer while measuring the temperature of the solution with a thermometer. While stirring with a mechanical stirrer, 500 ml of potassium carbonate aqueous solution was put into 1000 ml of nitrate aqueous solution, and stirred for 1 hour while maintaining the temperature at 60 ° C. After stirring, the resulting sol was filtered with suction to collect a precipitate. The obtained precipitate was washed with 500 ml of pure water heated to 80 ° C. and suction filtered again four times to remove potassium. The washed precipitate is put into 500 ml of pure water, kneaded until it becomes a paste, and 95.24 g of alumina sol (Nissan Chemical Industries, Alumina Sol 520) is added while stirring with a mechanical stirrer, and further stirred for 30 minutes. Went. After visually confirming that the whole was uniform, it was allowed to stand overnight and aged. After stirring again, it moved to the rotary evaporator, the water | moisture content was removed, and the obtained solid substance was further dried at 120 degreeC in the dryer for 20 hours. The solid matter was taken out from the dryer and pulverized in an agate mortar. The obtained powder was transferred to an alumina crucible and fired at 950 ° C. for 20 hours in an electric furnace. After cooling, the resulting catalyst was designated as Catalyst A.

  The catalyst A contains 50% alumina by mass, and the remaining 50% by mass contains magnesium oxide and nickel oxide in a molar ratio of metal elements of 9: 1.

<Catalyst B: Nickel-based catalyst>
Similarly to the catalyst A, a nickel-supported catalyst was prepared by a coprecipitation method.
However, as precursor reagents, nickel nitrate hexahydrate (Kanto Chemical, purity> 98.0%) 13.30 g and cerium nitrate (III) hexahydrate (Kanto Chemical, purity> 99.5%) ) 19.85 g and 93.79 g of magnesium nitrate hexahydrate (Wako Pure Chemical, purity> 99.0%). In addition, 69.51 g of potassium carbonate to be weighed (Kanto Chemical, purity> 99.5%) was used. Then 101.26 g of alumina sol (manufactured by Nissan Chemical Industries, alumina sol 520) was added to the precipitate. It cooled after baking and the obtained catalyst was set to the catalyst B.

  Catalyst B contains 50% by mass of alumina, and the remaining 50% by mass contains magnesium oxide, nickel oxide, and cerium oxide in a molar ratio of metal elements of 8: 1: 1.

<Catalyst C: Cerium oxide + Aluminum oxide>
A cerium oxide support (Catalyst Society Reference Catalyst: CEO-2) 3.4010 g and alumina (Catalyst Society Reference Catalyst: ALO-8) 1.0056 g were weighed and dispersed in pure water. The obtained suspension was dispersed in 20 cm ³ of pure water, and mixed for 30 minutes using an ultrasonic cleaner. The water in the suspension was evaporated to dryness, and the resulting solid was pulverized with agate and fired at 800 ° C. for 5 hours in a muffle furnace. After cooling, the obtained sample was designated as Catalyst C.

  The catalyst C contains aluminum and cerium at a metal ion molar ratio of 1: 1. Moreover, the catalyst C contains 22.9% of aluminum oxide and 77.1% of cerium oxide in terms of mass ratio in terms of aluminum oxide and cerium oxide. This corresponds to containing 77.1% TREO.

<Catalyst D: Cerium oxide + Calcium oxide>
A catalyst was prepared by the citric acid method.
More specifically, cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) 3.8055 g, calcium nitrate tetrahydrate (Kanto Chemical, purity> 98.5%) 2 0.0722 g was weighed and dissolved in 50 ml of pure water. In the resulting solution, 6.7320 g of citric acid monohydrate (Wako Pure Chemical Industries, Ltd., purity> 99.5%) was further dissolved and stirred for 15 minutes with a magnetic stirrer. After confirming that the solution became transparent and had no undissolved residue, aqueous ammonia (Wako Pure Chemical Industries, Ltd., concentration 28% by mass) was added dropwise to adjust the pH to 7.0. The solution was stirred for an additional hour and the resulting solution was run on a rotary evaporator to reduce the volume of the solution and then transferred to an alumina crucible. It was heated to 100 ° C. on a hot plate, and the water was evaporated and dried to solidify over another 2 hours. The obtained solid was crushed on an agate mortar and powdered, and then returned to the alumina crucible. The sample was placed in an electric furnace together with an alumina crucible and fired in an air atmosphere. The temperature was raised from room temperature to 110 ° C. over 30 minutes, dried for 5 hours, heated to 800 ° C. over 3 hours, and calcined at 800 ° C. for 5 hours. Then, it cooled to room temperature and obtained the catalyst D.

  The catalyst D contains calcium oxide and cerium oxide at a metal ion molar ratio of 1: 1. Catalyst D contains 24.6% calcium oxide and 75.4% cerium oxide in terms of mass ratio in terms of calcium oxide and cerium oxide. This corresponds to containing 75.4% TREO.

<Catalyst E: Cerium oxide + Iron oxide>
In the same manner as Catalyst D, a catalyst was prepared by the citric acid method.
However, as a reagent, cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) 2.3332 g and iron (III) nitrate nonahydrate (Kanto Chemical, purity> 99.0) %) 0.3829 g and citric acid monohydrate 2.5805 g were weighed and dissolved purely. After the calcination treatment, the obtained catalyst was named Catalyst E.

  The catalyst E contains iron oxide and cerium oxide at a metal ion molar ratio of approximately 1.5: 8.5. Catalyst E contains 7.6% iron oxide and 92.4% cerium oxide in terms of mass ratio in terms of iron (III) oxide and cerium oxide. This corresponds to containing 92.4% TREO. When XRD measurement of catalyst E was performed, a weak iron (III) oxide peak was observed.

<Catalyst F: Cerium oxide + Barium oxide>
In the same manner as Catalyst D, a catalyst was prepared by the citric acid method.
However, as a reagent, cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) 2.6657 g and barium nitrate (II) (Kanto Chemical, purity> 99.0%) 1.6060 g And 4.7231 g of citric acid monohydrate were weighed and dissolved purely. The catalyst obtained after the calcination treatment was designated as catalyst F.

  The catalyst F contains barium oxide and cerium oxide at a metal ion molar ratio of 1: 1. Further, the catalyst F contains 47.1% barium oxide and 52.9% cerium oxide in a mass ratio in terms of barium oxide and cerium oxide. This corresponds to containing 52.9% of TREO.

<Catalysts 1-3: Cerium oxide catalyst>
10 g of each of three types of cerium oxide supports (Catalyst Society Reference Catalyst: CEO-2, CEO-3, CEO-4) were weighed and calcined in an electric furnace at 900 ° C. for 5 hours. It cooled to room temperature and obtained catalysts 1-3. As shown in Table 1 below, all contain cerium oxide in excess of 99% by mass ratio in terms of oxide. This corresponds to containing more than 99% of TREO.

<Catalyst 4: Cerium oxide catalyst>
10 g of a cerium oxide support (Catalyst Society Reference Catalyst: CEO-2) was weighed and calcined in an electric furnace at 800 ° C. for 5 hours in an air atmosphere. Cooling to room temperature gave catalyst 4. As shown in Table 1, the catalyst 4 contains more than 99% of cerium oxide by mass ratio in terms of oxide. This corresponds to containing more than 99% of TREO.

<Catalyst 5: Cerium oxide catalyst (citric acid method)>
In the same manner as Catalyst D, a catalyst was prepared by the citric acid method.
However, 5.0452 g of cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) was weighed and dissolved in 50 ml of pure water, and citric acid monohydrate was added to the resulting solution. 4.4655 g (Wako Pure Chemical, purity> 99.5%) was further dissolved. After the calcination treatment, catalyst 5 was obtained. As shown in Table 1, the catalyst 5 contains cerium oxide in excess of 99% (described as 100% in Table 1) in terms of mass ratio in terms of oxide. This corresponds to containing more than 99% of TREO.

<Catalyst 6: Cerium oxide catalyst (coprecipitation method)>
A catalyst was prepared by a coprecipitation method.
More specifically, 7.5665 g of cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) was weighed and dissolved in 17.4 ml of pure water. To the resulting solution, 1.0 ml of hydrogen peroxide solution (Wako Pure Chemicals, special grade reagent, concentration 30 to 35.5% by mass) was dropped. After stirring until the whole became uniform, aqueous ammonia (Wako Pure Chemicals, concentration 28 mass%) was added dropwise to adjust the pH to 8.0. Stir for 1 hour and let stand for 30 minutes. The resulting precipitate was suction filtered using a membrane filter and washed with pure water. The obtained precipitate was dried on a hot plate at 100 ° C., and then subjected to calcination treatment in an electric furnace in the same procedure as for catalyst 5, whereby catalyst 6 was obtained. As shown in Table 1, the catalyst 6 contains cerium oxide in excess of 99% (described as 100% in Table 1) in terms of mass ratio in terms of oxide. This corresponds to containing more than 99% of TREO.

<Catalyst 7: Lanthanum-cerium catalyst (citric acid method)>
In the same manner as Catalyst D, a catalyst was prepared by the citric acid method.
However, as precursors, cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) 6.8484 g and lanthanum nitrate (III) hexahydrate (Kanto Chemical, purity> 99. 0%) and 0.7584 g were dissolved in 50 ml of pure water, and 6.7314 g of citric acid monohydrate (Wako Pure Chemical Industries, Ltd., purity> 99.5%) was further dissolved in the resulting solution. I let you. After the calcination treatment, catalyst 7 was obtained. The catalyst 7 contains lanthanum and cerium in a molar ratio of metal ions at a ratio of 1: 9. Further, the catalyst 7 contains 9.4% lanthanum oxide and 90.6% cerium oxide in a mass ratio in terms of lanthanum oxide (III) and cerium (IV) oxide. This corresponds to containing more than 99% of TREO.

<Catalyst 8: Lanthanum-cerium catalyst (citric acid method)>
In the same manner as Catalyst D, a catalyst was prepared by the citric acid method.
However, as precursors, cerium (III) nitrate hexahydrate (Kanto Chemical, purity> 99.5%) 1.2966 g and lanthanum nitrate (III) hexahydrate (Kanto Chemical, purity> 99. 09.3) 1.2933 g, dissolved in 50 ml of pure water, and further dissolved 2.5088 g of citric acid monohydrate (Wako Pure Chemicals, purity> 99.5%) in the resulting solution. I let you. After the calcination treatment, catalyst 8 was obtained. The catalyst 8 contains lanthanum and cerium in a molar ratio of metal ions at a ratio of 5: 5. Further, the catalyst 8 contains 51.4% lanthanum oxide and 48.6% cerium oxide in a mass ratio in terms of lanthanum (III) oxide and cerium (IV) oxide. This corresponds to containing more than 99% of TREO.

<Catalyst 9: Cerium oxide + Aluminum oxide>
Except that 2.8503 g of cerium oxide support (Catalyst Society reference catalyst: CEO-2) and 0.1506 g of alumina (Catalyst Society reference catalyst: ALO-8) were weighed and dispersed in pure water. A catalyst was prepared in the same manner as Catalyst C. The obtained sample was designated as catalyst 9. The catalyst 9 contains 5.0% aluminum oxide and 95.0% cerium oxide in a mass ratio in terms of aluminum oxide and cerium oxide. This corresponds to containing 95.0% TREO.

<Catalyst 10: Cerium oxide catalyst>
10 g of cerium oxide support (Showa Denko: Showrox FL-2) was weighed and baked in an electric furnace at 950 ° C. for 5 hours in an air atmosphere. The catalyst 10 was obtained by cooling to room temperature. As shown in Table 1, the catalyst 10 contains 98.2% cerium oxide and 0.972% lanthanum oxide in mass ratio in terms of oxide. This corresponds to containing more than 99% of TREO.

  About each of the catalysts 1-10 produced | generated as mentioned above, the specific surface area and the composition were measured as follows.

[Specific surface area measurement]
Specific surface areas of the catalysts 1 to 10 were measured by a BET method using a nitrogen adsorption isotherm at a liquid nitrogen temperature. The measurement was carried out using an adsorption measuring device (Nippon Bell, BEL-max). The measurement results are summarized in Table 1 below.

[Composition analysis]
The composition ratio of each catalyst is shown in Table 1 below. For the catalysts 1 to 4, the values described in the Catalytic Society Reference Catalyst Usage Guide (5th edition) are used, and for the catalysts 7, 8, and 9, the composition ratio calculated using the ratio of the reagents used is shown. It was. Moreover, about the catalysts 5, 6, and 10, the result of having performed a composition analysis measurement using the energy dispersive X-ray fluorescence analyzer (the product made by Rigaku, NEXCG (EDXL 300)) was shown.

  In the above table, since the sources are different for each sample, the effective orders are different.

(Evaluation)
((1. Steam reforming))
((1-1. Evaluation of methane reforming reaction test))
Using each of the catalysts produced as described above, a steam reforming reaction test of methane was performed. Each catalyst was compression-molded before the reaction, and the particle size was made uniform using a plurality of sieves having different openings, and the particle size was adjusted to 1.0 mm to 2.0 mm. Detailed experimental conditions are as follows.

<Comparative Examples 1 and 2: Nickel-based catalyst>
0.10 g of each of the molded catalyst A and catalyst B was weighed and filled in a reaction tube made of quartz glass. As pretreatment, the temperature was raised to 800 ° C. in 30 minutes while flowing hydrogen gas at 50 cm ³ / min, and reduction treatment was performed for 30 minutes. Thereafter, the gas to be treated shown in Table 2 below was circulated to start the reaction. However, the concentration of hydrogen sulfide in the gas to be treated is 0 ppm until 1 hour after the start of the reaction, 1 ppm after the start of the reaction, 500 ppm until 2 hours after the start of the reaction, and over 2 hours after the start of the reaction. It was set to 1000 ppm until 3 hours later, and 2000 ppm after 3 hours after the start of the reaction and up to 4 hours after the start of the reaction. Activity was evaluated using the methane conversion in the second half of the reaction at each hydrogen sulfide concentration.

  The gas to be treated was analyzed using a gas chromatograph (Shimadzu Corporation, GC-2014) every 15 minutes. Moreover, the following formula 1 was used for the calculation of the methane conversion rate, and the calculation was performed with the concentration of each component of the gas after reaction. The methane conversion at each hydrogen sulfide concentration is summarized in Table 4 below.

  Hereinafter, in all the samples in Table 4, the amount of organic substances having 2 or more carbon atoms and 3 or more carbon atoms was very small. Further, thermogravimetric analysis was performed on the samples after the reaction, but no weight reduction due to oxidative combustion of precipitated carbon was observed in any of the samples. From these results, it is considered that the amount of carbon deposition is very small, and it is considered appropriate to evaluate the methane conversion rate using the following formula 1.

  In this test, both the catalysts A and B showed low activity even at a hydrogen sulfide concentration of 0 ppm. This is considered to be caused by the low concentration of hydrogen sulfide mixed in the pretreatment for reduction because of the high concentration of hydrogen sulfide in the reaction line. As described above, even with a low concentration of hydrogen sulfide that is not intentionally added, the nickel-based catalyst shows a large decrease in activity.

  As for the catalyst A, the catalyst activity tended to decrease as the hydrogen sulfide concentration increased. On the other hand, it was confirmed that the catalyst B containing cerium oxide tends to improve the catalytic activity as the hydrogen sulfide concentration increases.

<Comparative Examples 3 to 6: Cerium oxide catalyst>
Comparative example, except that catalysts C to F after molding were used as the catalyst and the reaction was started by raising the temperature while circulating nitrogen at 50 cm ³ / min without performing pre-reaction treatment. The reaction was carried out in the same manner as in 1. The results of the reaction test are shown in Table 4 below.

  All of the catalysts obtained only a low activity as compared with the catalyst of cerium oxide alone. Moreover, although any catalyst contained 50% or more of cerium oxide by mass ratio, only a half or less methane conversion rate was obtained as compared with cerium oxide alone. Furthermore, the catalyst E containing iron oxide has a tendency to decrease in catalytic activity as the hydrogen sulfide concentration increases. In the catalyst F containing barium oxide, the formation of cerium sulfate was confirmed by XRD measurement of the sample after the reaction. It was. From these results, mixing other elements with cerium oxide reduces the catalytic activity of cerium oxide, reduces the resistance to hydrogen sulfide, and further facilitates the formation of cerium sulfate during the reaction. confirmed.

Methane conversion rate = (CO concentration + CO ₂ concentration) / (CO concentration + CO ₂ concentration + CH ₄ concentration)
... (Formula 1)

<Examples 1 to 9: Cerium oxide catalyst>
A reaction test was performed in the same manner as Comparative Examples 3 to 6 except that the molded catalysts 1 to 9 were used as the catalyst. The methane conversion at each hydrogen sulfide concentration is summarized in Table 4 below. The reaction test using the catalysts 1-9 was made into Examples 1-9, respectively.

  As a result of performing XRD measurement of the catalyst 1 after the reaction in Example 1, the crystal structure of the catalyst 1 was not changed before and after the reaction, and no other impurity peak was detected. Moreover, although the catalyst 9 contained 5.0% of aluminum oxide as an impurity by mass ratio, the methane conversion rate exceeding the catalyst 6 comprised only by cerium oxide was obtained. From these results, it is considered that if the amount of impurities is 5.0% or less by mass ratio (that is, the purity of cerium oxide is 95.0% or more), the influence of impurities can be reduced.

<Example 10: Cerium oxide catalyst>
A reaction test was performed in the same manner as Comparative Examples 3 to 6 except that the molded catalyst 1 was used as the catalyst and the reaction temperature was 900 ° C. The methane conversion at each hydrogen sulfide concentration is summarized in Table 4 below. Moreover, the XRD measurement result of the catalyst 1 before and after the reaction is shown in FIG.

  As is clear from FIG. 1, no change was observed in the crystal structure before and after the reaction, and the formation of impurities such as cerium sulfate was not confirmed. During the reaction, the amount of water vapor introduced inevitably fluctuated, and it is considered that the hydrogen sulfide concentration exceeded 2000 ppm for at least a short time during the reaction test. However, it was confirmed that no impurity was generated even under such conditions.

<Examples 11 and 12: Cerium oxide catalyst>
Reaction tests were conducted in the same manner as in Comparative Examples 3 to 6 except that the molded catalyst 1 and catalyst 10 were used as the catalysts, respectively, and the reaction temperature was 950 ° C. The methane conversion at each hydrogen sulfide concentration is summarized in Table 4 below. In any result, it was confirmed that a high methane conversion rate was obtained as compared with Examples 1-9. The test using the catalyst 1 was taken as Example 11, and the test using the catalyst 10 was taken as Example 12.

  For Example 11, the reaction time was further extended and the reaction was carried out at a hydrogen sulfide concentration of 2000 ppm for 4 hours, but the decrease in catalyst activity during the reaction was slight, and the methane conversion rate at the end of the reaction was 24.7%. there were.

((1-2. Tar reforming reaction test evaluation))
A tar reforming reaction test was carried out using the catalyst produced as described above. Each catalyst was compression-molded before the reaction, and the particle size was made uniform using a plurality of sieves having different openings, and the particle size was adjusted to 1.0 mm to 2.0 mm. Detailed experimental conditions are as follows.

<Comparative Examples 7 and 8: Nickel-based catalyst>
Each of catalyst A and catalyst B after molding was weighed 9.5 cm ³ using a graduated cylinder and filled in a reaction tube. As pretreatment, the temperature was raised to 800 ° C. in 30 minutes while flowing hydrogen gas at 50 cm ³ / min, and reduction treatment was performed for 30 minutes. Thereafter, the gas to be treated shown in Table 3 below and steam having an amount of steam carbon ratio (S / C) = 0.8 were introduced to start the reaction. The reaction gas flow rate was 80 cm ³ / min as a whole, and the reaction time was 6 hours. In addition, space velocity (Space Velocity: SV) is 500 hours ^-1 .

  The reaction gas was analyzed using a gas chromatograph (Shimadzu Corporation, GC-2014) every 15 minutes. The analyzed gas components are hydrogen, nitrogen, methane, carbon monoxide, carbon dioxide, ethylene, ethane, propylene, and propane.

  Assuming that the nitrogen flow rate does not change before and after the reaction, the flow rate of each component of the post-reaction gas was calculated using the relative concentration with the nitrogen concentration. In addition, the reaction activity was evaluated using the hydrogen amplification factor represented by the following formula 2 and the gasification yield represented by the following formula 3. The hydrogen amplification factor is a value indicating how many times the molar amount of hydrogen has increased before and after the reaction, and is a value indicating the efficiency of hydrogen production. On the other hand, the gasification yield is a value indicating the ratio of carbon contained in 1-methylnaphthalene converted to gas, and the larger the value, the better the reforming catalyst. For each value, an average value for 2 to 3 hours and an average value for 5 to 6 hours from the start of the reaction were calculated, and the stability of the reaction was evaluated.

  In addition, after the reaction test, thermogravimetric analysis of each catalyst was performed under a dry air flow, and the amount of weight reduction was defined as the carbon deposition amount. Table 5 below shows the test using the catalyst A as Comparative Example 7 and the test using the catalyst B as Comparative Example 8.

  As is apparent from Table 5 below, catalyst B containing cerium oxide has a greater reduction in gasification yield. Under the present test conditions, cerium oxide and a nickel-based catalyst coexist to stabilize the catalyst. It is thought that the nature is lowered.

  Hydrogen amplification factor = hydrogen flow rate (after reaction) / hydrogen flow rate (before reaction) (Equation 2)

  Gasification yield = 100 × (methane flow rate (after reaction) + carbon monoxide flow rate (after reaction) + carbon dioxide flow rate (after reaction) + ethylene flow rate (after reaction) × 2 + ethane flow rate (after reaction) × 2 + propylene flow rate (After reaction) × 3 + Propane flow rate (after reaction) × 3) / (1-Methylnaphthalene flow rate (before reaction) × 11) (Formula 3)

<Comparative Examples 9 and 10: Nickel-based catalyst>
A tar reforming reaction test was conducted in the same manner as in Comparative Examples 3 and 4 except that the amount of catalyst A and catalyst B after molding was 3.2 cm ³ . S / C is 0.8 and SV is 1500 hours ^-1 . Table 5 below shows the results of analysis and evaluation performed in the same manner as in Comparative Examples 7 and 8 with the test using Catalyst A as Comparative Example 9 and the test using Catalyst B as Comparative Example 10. It was.

<Comparative Examples 11 and 12: Nickel-based catalyst>
The tar reforming reaction test was conducted in the same manner as in Comparative Examples 7 and 8, except that the amount of the catalyst A and catalyst B after molding was 3.2 cm ³ and S / C = 1.2. . S / C is 1.2 and SV is 1500 hours ^-1 . Table 5 below shows the results of analysis and evaluation performed in the same manner as in Comparative Examples 7 and 8 with the test using Catalyst A as Comparative Example 11 and the test using Catalyst B as Comparative Example 12. It was.

<Example 13: Cerium oxide catalyst>
A tar reforming reaction test was conducted in the same manner as in Comparative Examples 7 and 8, except that the molded catalyst 1 was used as the catalyst, and the gas at the time of temperature rise and pretreatment was changed to nitrogen. S / C is 0.8 and SV is 500 hours ^-1 . The test result is referred to as Example 13. The obtained results are shown in Table 5 below.

  As is clear from Table 5 below, the test result of Example 13 is higher in both hydrogen amplification rate and gasification yield than Comparative Examples 7 and 8 in which the reaction was performed under the same reaction conditions. showed that.

<Example 14: Cerium oxide catalyst>
Tar reforming was carried out in the same manner as in Comparative Examples 7 and 8, except that the molded catalyst 1 was used as the catalyst, the temperature at the time of temperature rise and pretreatment was nitrogen, and the amount of the catalyst was 3.2 cm ^3. A reaction test was conducted. S / C is 0.8 and SV is 1500 hours ^-1 . The test result is referred to as Example 14. The obtained results are shown in Table 5 below.

  As apparent from Table 5 below, the test result of Example 14 shows that both the hydrogen amplification rate and the gasification yield are high compared to Comparative Examples 9 and 10 in which the reaction was performed under the same reaction conditions. It can be seen that the amount of carbon deposition is also small. Moreover, in order to investigate the crystal structure change before and behind reaction of the catalyst 1 (CEO-2, 900 degreeC baking) used in Example 14, the result of having performed the XRD measurement was shown in the following FIG. As is clear from FIG. 1, the crystal structure did not change before and after the reaction, and the formation of cerium sulfate or the like was not confirmed.

<Example 15: Cerium oxide catalyst>
Comparative Example 7, except that the molded catalyst 1 was used as the catalyst, the temperature at the time of temperature rise and pretreatment was nitrogen, the catalyst amount was 3.2 cm ^3, and S / C was 1.2. In the same manner as in No. 8, a tar reforming reaction test was conducted. S / C is 1.2 and SV is 1500 hours ^-1 . The result of this test is referred to as Example 15. The obtained results are shown in Table 5 below.

  As is clear from Table 5 below, the test result of Example 15 is higher in both hydrogen amplification rate and gasification yield than Comparative Examples 11 and 12 in which the reaction was performed under the same reaction conditions. Further, almost no carbon deposition was observed.

((2. Dry reforming))
((2-1. Evaluation of methane reforming reaction test))
Using each catalyst, a dry reforming reaction test of methane was performed. Each catalyst was compression-molded before the reaction, and the particle size was made uniform using a plurality of sieves having different openings, and the particle size was adjusted to 1.0 mm to 2.0 mm. Detailed experimental conditions are as follows.

<Comparative Example 13: Nickel-based catalyst>
A reaction test was performed in the same manner as in Comparative Examples 1 and 2 except that the catalyst A was used as the catalyst and the gas shown in Table 6 was circulated as the gas to be treated. The analysis of the gas to be treated was performed in the same manner as in Comparative Examples 1 and 2. Moreover, the following formula 3 was used for the calculation of the methane conversion rate, and the calculation was performed with the concentration of each component of the post-reaction gas. Equation 3 calculates the rate at which methane has changed to carbon dioxide and carbon monoxide by comparing the methane concentration with the sum of the carbon dioxide concentration and the carbon monoxide concentration. The methane conversion at each hydrogen sulfide concentration is summarized in Table 7 below.

  Hereinafter, in all the samples in Table 7, the amount of organic substances having 2 or more carbon atoms and 3 or more carbon atoms was very small. Further, the thermogravimetric analysis of the sample after the reaction was conducted. As for the catalyst A, although a small amount of carbon deposition was observed, no weight reduction due to oxidative combustion of the deposited carbon was observed in any of the other samples. From these results, it is considered reasonable to evaluate the methane conversion rate using the following Equation 3.

  In this test, the activity of Catalyst A was low even at a hydrogen sulfide concentration of 0 ppm. This is considered to be caused by the low concentration of hydrogen sulfide mixed in the pretreatment for reduction because of the high concentration of hydrogen sulfide in the reaction line. As described above, even with a low concentration of hydrogen sulfide that is not intentionally added, the nickel-based catalyst shows a large decrease in activity. Moreover, the catalyst A had a tendency for the catalyst activity to decrease as the hydrogen sulfide concentration increased.

Methane conversion rate = ((CO concentration + CO ₂ concentration + CH ₄ concentration) / 2−CH ₄ concentration) / ((CO concentration + CO ₂ concentration + CH ₄ concentration) / 2)
... (Formula 3)

<Examples 16 to 18: cerium oxide catalyst>
A reaction test was conducted in the same manner as in Comparative Example 13 except that the molded catalysts 4, 5, and 7 were used as the catalysts and the temperature was raised to the reaction temperature under a nitrogen flow without performing pretreatment. . The methane conversion at each hydrogen sulfide concentration is summarized in Table 7 below. The reaction tests using the catalysts 4, 5, and 7 were respectively Examples 16 to 18. Catalyst 4 and catalyst 5 were composed of the same material, and the methane conversion was the same at all hydrogen sulfide concentrations. A high methane conversion was also obtained for catalyst 7, but the activity was slightly lower than that of catalysts 4 and 5.

  As a result of performing XRD measurement of the catalyst 4 after the reaction in Example 16, there was no change in the crystal structure of the catalyst 4 before and after the reaction, and no other impurity peak was detected.

((2-2. Evaluation of tar reforming reaction test))
Using each catalyst shown in Table 10, a tar reforming reaction test was performed. Each catalyst was compression-molded before the reaction, and the particle size was made uniform using a plurality of sieves having different openings, and the particle size was adjusted to 1.0 mm to 2.0 mm. Detailed experimental conditions are as follows.

<Comparative Examples 14 and 15: Nickel-based catalyst>
Each of the molded catalyst A and catalyst B was weighed 3.2 cm ³ using a graduated cylinder and filled in a reaction tube. As pretreatment, the temperature was raised to 800 ° C. in 30 minutes while flowing hydrogen gas at 50 cm ³ / min, and reduction treatment was performed for 30 minutes. Then, the to-be-processed gas shown in the following Table 8 was introduce | transduced, and reaction was started. The CO ₂ / C ratio is 1.0. The reaction gas flow rate was 80 cm ³ / min as a whole, and the reaction time was 6 hours. In addition, space velocity (Space Velocity: SV) is 1500 hours ^-1 . Analysis of the reaction gas was the same as in Examples 13-15.

  Assuming that the nitrogen flow rate does not change before and after the reaction, the flow rate of each component of the post-reaction gas was calculated using the relative concentration with the nitrogen concentration. Further, hydrogen and carbon monoxide amplification factors represented by the following formula 4 were used as evaluation criteria for reaction activity. Unlike the steam reforming reaction, the dry reforming reaction contains a large amount of carbon dioxide in the reaction gas. Accordingly, carbon monoxide and hydrogen react to generate carbon monoxide and water vapor (reverse shift reaction), and the amount of hydrogen decreases. Therefore, the activity of the catalyst is evaluated based on the sum of hydrogen and carbon monoxide, which can be changed with each other by the aqueous shift reaction. That is, if carbon dioxide and 1-methylnaphthalene react with each other, carbon monoxide and hydrogen should be generated, so if you look at how much the sum of the flow rates of carbon monoxide and hydrogen increased before and after the reaction, The activity of the catalyst can be compared. About each catalyst, the average value for 2-3 hours from the reaction start and the average value for 5-6 hours were calculated, respectively, and the stability of reaction was evaluated.

  In addition, after the reaction test, thermogravimetric analysis of each catalyst was performed under a dry air flow, and the amount of weight reduction was defined as the carbon deposition amount. The test using the catalyst A is shown as Comparative Example 14 and the test using the catalyst B is shown as Comparative Example 15 in Table 10 below. In both cases, it was confirmed that the amount of carbon deposited was very large.

<Example 19: Cerium oxide catalyst>
The reaction test was carried out in the same manner as in Comparative Examples 14 and 15 except that the catalyst 4 was used as the catalyst, and the temperature was raised to 800 ° C. in 30 minutes while flowing nitrogen without performing pretreatment. The CO ₂ / C ratio is 1.0. The catalytic activity was evaluated in the same manner as in Comparative Examples 14 and 15, and the carbon deposition amount was also evaluated. The results are shown in Table 10 together. The catalyst 4 was found to have a smaller amount of carbon deposition than Comparative Examples 14 and 15, and the hydrogen and carbon monoxide amplification rates at the time of 2 to 3 hours from the start of the reaction were also high.

<Comparative Example 16: Nickel-based catalyst>
The experiment was performed in the same manner as Comparative Examples 14 and 15 except that the molded gas A was introduced and the gas to be treated shown in Table 9 below was introduced. The CO ₂ / C ratio is 2.0. In the same manner as in Comparative Examples 14 and 15, the measurement data was analyzed to evaluate the activity of the catalyst, and the carbon deposition amount was also evaluated. The results are shown in Table 10 together. Although the decrease in the amount of carbon deposition was confirmed due to the increase in the flow rate of carbon dioxide, a large amount of carbon deposition was confirmed.

<Example 20: Cerium oxide catalyst>
The reaction test was carried out in the same manner as in Comparative Example 16 except that the catalyst 4 was used as the catalyst, and the temperature was raised to 800 ° C. in 30 minutes while flowing nitrogen without performing pretreatment. The CO ₂ / C ratio is 2.0. The catalytic activity was evaluated in the same manner as in Comparative Example 16, and the carbon deposition amount was also evaluated. The results are shown in Table 10 together. The catalyst 4 was found to have a smaller amount of carbon deposition than the comparative example 16, and the hydrogen and carbon monoxide amplification factors at any time were also high. Furthermore, the values of hydrogen and carbon monoxide gain were almost constant over the reaction time, and high stability of the catalyst was also confirmed.

  Hydrogen and carbon monoxide amplification factor = ((hydrogen flow rate + carbon monoxide flow rate) (after reaction)) / ((hydrogen flow rate + carbon monoxide flow rate) (before reaction)) (Formula 4)

(3. Steam reforming and dry reforming)
((Tal reforming reaction test evaluation))
Using the catalyst 4, a tar reforming reaction test was carried out. In addition, the catalyst 4 was compression-molded before the reaction, and the particle size was made uniform using a plurality of sieves having different openings, and the particle size was adjusted to 1.0 mm to 2.0 mm, and used for the reaction test. Detailed experimental conditions are as follows.

<Example 21: Cerium oxide catalyst>
A reaction test was carried out using the catalyst 4 after molding. Using a graduated cylinder, 3.2 cm ^{3 was} weighed and filled into a reaction tube. The test was performed in the same manner as in Example 19 except that the gas to be treated shown in Table 11 below was introduced. The CO ₂ / C ratio is 1.0 and the steam carbon ratio is 0.5. The steam was carried out by introducing pure water into the reaction tube with a water pump and evaporating the whole amount. The reaction gas flow rate was 80 cm ³ / min as a whole, and the reaction time was 6 hours. In addition, space velocity (Space Velocity: SV) is 1500 hours ^-1 . The analysis of the reaction gas was the same as in Example 19, and the catalytic activity was evaluated in the same manner. The results obtained are shown in Table 12.

  Example 21 is carried out under substantially the same conditions as in Example 19, with the conditions that a part of nitrogen is replaced with water vapor. Comparing the results shown in Table 12 and Table 10, it can be seen that by introducing a small amount of water vapor having a steam carbon ratio of 0.5, the catalytic activity is increased, and the amount of carbon deposition is greatly reduced. Steam with a steam carbon ratio of 0.5 is an amount that can be contained in ordinary coke oven gas, and can be introduced at a very low cost. It was confirmed that by introducing such a small amount of water vapor into the reaction gas together with carbon dioxide, it is possible to increase the rate of the tar reforming reaction and suppress carbon deposition. A similar effect is presumed to be obtained in the reaction of hydrocarbons other than tar.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

Claims (13)

  When the total composition of the catalyst is converted to oxide, the ratio of the total rare earth oxide (TREO) is 95.0% or more in terms of mass ratio in terms of oxide. A treated gas containing hydrogen, 500 ppm or more of hydrogen sulfide, and at least one of water vapor or carbon dioxide is brought into contact, and the hydrocarbon in the treated gas is subjected to a steam reforming reaction or a dry reforming reaction. A method for producing hydrogen, wherein hydrogen is produced by reacting at least one of the above reactions.   2. The method for producing hydrogen according to claim 1, wherein the cerium oxide catalyst is 99% or more in terms of a mass ratio in terms of oxide when the total composition of the catalyst is converted into oxides. .   The ratio of the cerium oxide in the cerium oxide catalyst when the total composition of the catalyst is converted to oxide is 90.0% or more in terms of mass ratio in terms of oxide, 3. Production method. The cerium oxide catalyst contains at least one of iron oxide, aluminum oxide, calcium oxide, barium oxide, nickel oxide, zirconium oxide, and niobium oxide,
The iron oxide content is 3% or less in terms of mass ratio in terms of iron (III) oxide,
Content of the said aluminum oxide, the said calcium oxide, the said barium oxide, the said nickel oxide, the said zirconium oxide, and the said niobium oxide is a mass ratio of oxide conversion, and is 5% or less, respectively. The method for producing hydrogen according to any one of the above.   The method for producing hydrogen according to any one of claims 1 to 4, wherein a concentration of hydrogen sulfide contained in the gas to be treated is 500 ppm or more and 3000 ppm or less.   The method for producing hydrogen according to any one of claims 1 to 5, wherein the gas to be treated contains tar. The method for producing hydrogen according to claim 1, wherein the cerium oxide catalyst has a specific surface area of 10 m ² / g or more and 100 m ² / g or less.   8. The method for producing hydrogen according to claim 1, wherein when the steam reforming reaction proceeds, a steam carbon ratio of the gas to be treated is 0.8 or more and 3.0 or less.   When the dry reforming reaction proceeds, the molar ratio of carbon dioxide in the gas to be treated and carbon atoms contained as hydrocarbons is 1.0 or more and 3.0 or less. The method for producing hydrogen according to any one of the above.   The method for producing hydrogen according to claim 8 or 9, wherein the gas to be treated is coke oven gas. When the total composition of the catalyst is converted to oxide, the proportion of CeO ₂ is 90.0% or more in terms of oxide-converted mass ratio,
The proportion of total rare earth oxide (TREO) is 95.0% or more in terms of oxide-converted mass ratio, and
Specific surface area, ^{10 m} 2 / g or more and 100 m ² / g or less, cerium oxide catalyst for hydrogen production. Containing at least one of iron oxide, aluminum oxide, calcium oxide, barium oxide, nickel oxide, zirconium oxide, and niobium oxide,
The iron oxide content is 3% or less in terms of mass ratio in terms of iron (III) oxide,
12. The content of the aluminum oxide, the calcium oxide, the barium oxide, the nickel oxide, the zirconium oxide, and the niobium oxide is 5% or less in terms of oxide mass ratio, respectively. Cerium oxide catalyst for the production of hydrogen. The cerium oxide catalyst for hydrogen production according to claim 11 or 12, wherein the proportion of CeO ₂ is 99.0% or more in terms of mass ratio in terms of oxide.

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