JP6631245B2 - Method for producing catalyst for reforming hydrocarbon and method for reforming light hydrocarbon - Google Patents

Description

  The present invention provides a method for producing a hydrocarbon reforming catalyst (hereinafter, may be simply referred to as “catalyst”) that reforms a light hydrocarbon feedstock with steam and converts it into a gas such as hydrogen or carbon monoxide, and And a light hydrocarbon reforming method using a hydrocarbon reforming catalyst.

  Hydrogen is expected as a raw material for new energy, and is used in hydrogen production equipment for hydrogen stations and in fixed fuel cell systems that are expected to spread to homes and small and medium-sized business establishments. Production at the site is being considered. At present, hydrogen stations and household fuel cells produce hydrogen using natural gas, city gas, LPG, kerosene, etc. as raw materials, and in such cells, a catalyst supporting a noble metal element is generally used. Therefore, it is a very expensive system. In order to spread these hydrogen production systems, it is important to reduce the price of the systems. Among them, the price of a reforming catalyst for producing hydrogen from fuel accounts for a large proportion. That is, it is considered that realizing a higher performance of the reforming catalyst, reducing the amount of noble metal used, and realizing a lower price will lead to promotion of the system.

  Therefore, it is desired to use a catalyst in which the amount of the noble metal used is greatly reduced or a less expensive element from a catalyst using a noble metal. For example, as an inexpensive metal element, nickel is one of the potential elements.

  Conventionally, in a nickel / alumina-based catalyst (for example, Patent Document 1) most frequently used as a hydrocarbon reforming catalyst, an alumina phase changes to an α-alumina phase in a high temperature region, and crystal growth proceeds. Therefore, there is a problem that the specific surface area sharply decreases, and accordingly, the reaction activity decreases. In addition, these catalysts contain a large amount of nickel, and carbon precipitation easily occurs on the surface of the catalyst. Therefore, potassium or calcium is often added as an alkali component to prevent the precipitation (Patent Document 2). .

  In the case of such a catalyst containing a large amount of nickel, during use of the catalyst, a potassium compound may be scattered to a reaction apparatus, a pipe, or the like, which may cause a problem such as occurrence of corrosion. In addition, the catalyst has a large amount of supported nickel, but has a low dispersity, and has a problem that it is difficult to advance the reforming reaction at a high reaction rate because the active metal is coarsely precipitated. Furthermore, when these catalysts are used to reform hydrocarbons containing sulfur compounds that have a poisoning effect, a stable compound is generated between the active metal and sulfur, thereby reducing the effects of sulfur poisoning. Since it is greatly affected, there is a problem that the catalytic activity is greatly reduced.

  On the other hand, a method has been reported in which a heat-resistant carrier is used as a composite oxide by adding another component to alumina. For example, those prepared by impregnating alumina with lanthanum, lithium or strontium (for example, Patent Documents 3 to 5), and those prepared by coprecipitating alumina with a hydroxide thereof from a rare earth salt (Patent Document 3) Reference 6), and a spinel-type one obtained by adding magnesia to alumina and firing the same (Patent Document 7) and the like are reported. These are all based on the premise that a porous carrier is first prepared and the nickel active component is supported in the pores of the porous body by the impregnation method, and the fine dispersion of the active component is limited. Therefore, it is inferior in catalytic activity.

  As a conventional noble metal-based catalyst, a catalyst in which ruthenium, platinum, rhodium, or the like is supported on alumina or the like is known. Since these catalysts have an action of suppressing carbon deposition by utilizing the physical properties of the noble metal component, they have a feature that carbon deposition is small and the activity is easily maintained as compared with the nickel-based catalyst. . However, since these catalysts also have a disadvantage that they are easily poisoned by sulfur compounds, hydrocarbons whose sulfur compounds have been reduced to the ppb level through a desulfurization step are usually reformed with these catalysts (Patent Reference 8).

  In addition, as a method for producing an oxide containing nickel, magnesium and aluminum, a precipitant is added to an aqueous solution in which each metal component is dissolved to form a precipitate (mainly a hydrotalcite structure), In some cases, the reforming reaction of hydrocarbons is performed using a dried and calcined catalyst. (Patent Document 9).

  On the other hand, a precipitate was formed from an aqueous solution containing nickel and magnesium, the precipitate was mixed with alumina powder and water, or alumina sol was added to form a mixture, and the mixture was obtained by drying and calcining the mixture. A catalyst has been proposed that reforms a gas containing tar mainly composed of heavy-chain hydrocarbons or condensed polycyclic aromatic hydrocarbons generated when pyrolyzing coal, biomass, or the like. (Patent Documents 10 and 11). This reaction exhibits catalytic activity to generate hydrogen, carbon monoxide, etc. even when a large amount of sulfur compounds are present, but the reactant is tar, and even when light hydrocarbons such as methane are decomposed, tar is generated. The catalyst converted into light hydrocarbons by hydrocracking. In Patent Document 11, cerium or the like is added in order to highly activate the tar reforming reaction.

JP-B-49-9312 JP 2010-155234 A U.S. Pat. No. 3,966,391 U.S. Pat. No. 4,021,185 U.S. Pat. No. 4,061,594 JP-A-63-175624 JP 2007-203159 A JP 2006-045049 A JP-A-2004-255245 WO 2010/035430 International Publication No. 2010/134326

  The present invention is capable of reforming light hydrocarbons such as methane with steam to convert them into gas such as hydrogen and carbon monoxide with high performance and stability even if the raw materials still contain sulfur compounds. An object of the present invention is to provide a method for producing a hydrocarbon reforming catalyst that can be used, and a hydrocarbon reforming method using the hydrocarbon reforming catalyst.

  The present inventors focused on the composition of the elements constituting the catalyst, designed the catalyst, and studied the production method diligently.Then, a light hydrocarbon such as methane containing a sulfur compound was reacted with steam to produce hydrogen. Higher activity and less decrease in activity with reaction time as compared to nickel / alumina-based catalysts, noble metal-based catalysts, and nickel / magnesia-based catalysts by conventional loading methods as catalysts for converting to carbon monoxide or the like The composition of the catalyst was found. The present invention has been completed based on this finding.

  The gist of the present invention is as follows.

[1] The ratio between the nickel compound and the magnesium compound is 0.05 / 0.95 to 0.3 / 0. 7 , a precipitant is added to the mixed solution to form a precipitate of hydrate by coprecipitating nickel and magnesium, and alumina sol or alumina powder and water are added to the precipitate. The obtained light hydrocarbon reforming catalyst is added so that the content of alumina in the catalyst is 5 to 30% by mass, mixed to form a mixture, and the mixture is dried and calcined to produce a light hydrocarbon. A method for reforming light hydrocarbons, comprising reforming light hydrocarbons using a reforming catalyst to obtain hydrogen and carbon monoxide.

[ 2 ] The ratio between the nickel compound and the magnesium compound is 0.2 / 0.8 to 0.3 / 0.7 (that is, Ni / Mg = 0.25 to 0.43) in a molar ratio of nickel to magnesium. The light hydrocarbon reforming method according to the above [1], wherein the light hydrocarbon reforming catalyst produced to satisfy the condition (1) is used.

[ 3 ] The light hydrocarbon according to [1] or [2], wherein a catalyst for reforming the light hydrocarbon manufactured so as to have an alumina content of 5 to 20% by mass is used. Reforming method.

[ 4 ] The method for reforming a light hydrocarbon according to any one of [1] to [3], wherein the light hydrocarbon contains a sulfur compound.

[ 5 ] The method for reforming a light hydrocarbon according to the above [4] , wherein the light hydrocarbon is a methane-containing gas.

  ADVANTAGE OF THE INVENTION According to this invention, the gas of light hydrocarbons, such as methane, can be converted to chemical substances, such as hydrogen and carbon monoxide, stably. In particular, even if a sulfur compound contained as an odorant in city gas or LPG is included, it is brought into contact with a catalyst without desulfurization treatment to reform hydrocarbons in the gas to produce hydrogen, monoxide. It can be converted stably to chemical substances such as carbon.

4 is a graph showing the relationship between the methane conversion (%) and the reforming reaction time (h) obtained by the examples of the present invention. 9 is a graph showing the relationship between the conversion (%) of hydrocarbons such as methane and the reforming reaction time (h) obtained in Example 9 of the present invention. 10 is a graph showing the relationship between the conversion (%) of hydrocarbons such as methane and the reforming reaction time (h) obtained in Example 10 of the present invention. 15 is a graph showing the relationship between the conversion (%) of hydrocarbons such as methane and the reforming reaction time (h) obtained in Example 15 of the present invention.

  The present inventors contact a light hydrocarbon containing a sulfur compound, such as natural gas, LNG, shale gas, city gas, LPG, etc., with a catalyst while containing the sulfur compound, and convert the light hydrocarbon into hydrogen, carbon monoxide, etc. We studied diligently about the method of stably converting to. The light hydrocarbons described here are C1 to C4 hydrocarbons such as methane, ethane, ethylene, propane, propylene, normal butane, and isobutane contained in city gas and LPG. The higher the number of carbon atoms, the easier it is to decompose, so high activity can be obtained. Is preferred.

As a result, the present inventors have found that as a catalyst for reforming of light hydrocarbons, a NiMgO catalyst, the constituent elements nickel, magnesium, aluminum, NiMgO, _{and, Ni X Mg 1-X Al} 2 O 4 It has been found that by using a metal oxide containing a crystal phase of as a catalyst, even if a light hydrocarbon containing a sulfur compound is reformed, the catalytic activity can be stably maintained for a long period of time. Here, the crystalline phase of _{Ni X Mg 1-X Al 2} O 4 , for example, by coprecipitation from a mixed solution containing a nickel compound and a magnesium compound to produce a precipitate of hydrates, after the generation of the precipitate Is a crystal phase that can be obtained by adding, mixing, drying, and calcining an aluminum component, and cannot be distinguished by X-ray diffraction measurement or the like. However, even when only NiAl ₂ O ₄ or MgAl ₂ O ₄ is used, possible.

  The reason that such a phenomenon was observed is that, according to the estimation of the present inventors, by performing reduction treatment with hydrogen before the reforming reaction, the active metal was removed from the matrix (mother phase) of the metal oxide. It is considered that a certain amount of nickel is finely precipitated in the form of clusters on the catalyst surface, so that activity reduction and carbon deposition due to sulfur poisoning hardly occur. Thus, it is considered that the catalyst obtained according to the present invention has little deterioration over time and can stably reform light hydrocarbons and convert them into hydrogen, carbon monoxide, and the like.

  In the present invention, unlike the conventional method for producing a catalyst by the impregnation-supporting method, a precipitate of a hydrate is formed by coprecipitation from a mixed solution containing a nickel compound and a magnesium compound. A catalyst for reforming hydrocarbons is produced by a solid phase crystallization method in which components are added, mixed, dried and calcined. (1) Fine deposition of active species metal is possible and high-speed reaction is possible. (2) The deposited active metal is firmly bonded to the matrix, so that sintering (aggregation) is difficult, and a decrease in activity can be suppressed. In particular, the present inventors have found that the composition of nickel, magnesium, and aluminum greatly affects the stabilization of the catalytic activity. That is, a hydrate precipitate is formed by coprecipitation from a mixed solution containing a nickel compound and a magnesium compound at a predetermined ratio. After the precipitate is formed, 5 to 30% by mass of an aluminum component is added as alumina and mixed. It has been found that a catalyst for reforming light hydrocarbons obtained by drying and calcining can particularly stably reform light hydrocarbons.

<Production method of hydrocarbon reforming catalyst>
Hereinafter, the method for producing the light hydrocarbon reforming catalyst of the present invention will be described in detail with reference to a preferred specific example of the present invention.

  First, a precipitant is added to a mixed aqueous solution of a nickel compound and a magnesium compound, and nickel and magnesium are coprecipitated to form a precipitate. When preparing a mixed aqueous solution of a nickel compound and a magnesium compound, it is appropriate to use each metal compound having high solubility in water. For example, not only inorganic salts such as nitrates, sulfates, carbonates and chlorides, but also organic salts such as acetates can be suitably used. Particularly preferred are nitrates, carbonates, and acetates, which are considered to be less likely to leave impurities that can poison the catalyst after calcination. The precipitant used when forming a precipitate from the aqueous solution is not particularly limited as long as the pH of the aqueous solution is changed from neutral to basic in which nickel and magnesium precipitate as hydroxides. For example, an aqueous solution of potassium carbonate or sodium carbonate, an aqueous solution of potassium hydroxide, an aqueous solution of sodium hydroxide, an aqueous solution of ammonia, or the like can be suitably used.

  After filtering the precipitate obtained as described above, washing with pure water 4 to 5 times and filtration are repeated, and excess cations (potassium and sodium in the precipitant) and anions (nitric acid, sulfuric acid, carbonic acid, chloride) By washing away substances, acetate ions, etc.), a mixture of nickel / magnesia hydroxide with reduced impurities is obtained. To this precipitate, alumina sol or alumina powder and water are added in an amount of 5 to 30% by mass, based on the mass at the time of completion of the catalyst production, and the mixture is mixed to form a mixture. By calcination, a catalyst can be produced.

  As another method, a precipitant is added to a mixed aqueous solution of a nickel compound, a magnesium compound, and aluminum, and nickel, magnesium, and aluminum are co-precipitated to generate a precipitate. When preparing the mixed aqueous solution, it is appropriate to use each metal compound having high solubility in water. For example, not only inorganic salts such as nitrates, sulfates, carbonates and chlorides, but also organic salts such as acetates can be suitably used. Particularly preferred are nitrates, carbonates, and acetates, which are considered to be less likely to leave impurities that can poison the catalyst after calcination. The precipitant used when forming a precipitate from the aqueous solution is not particularly limited as long as the pH of the aqueous solution is changed from neutral to basic in which nickel and magnesium precipitate as hydroxides. For example, an aqueous solution of potassium carbonate or sodium carbonate, an aqueous solution of potassium hydroxide, an aqueous solution of sodium hydroxide, an aqueous solution of ammonia, or the like can be suitably used.

After filtering the precipitate obtained as described above, washing with pure water 4 to 5 times and filtration are repeated, and excess cations (potassium and sodium in the precipitant) and anions (nitric acid, sulfuric acid, carbonic acid, chloride) , And a mixture of nickel / magnesia / aluminum hydroxide with reduced impurities can be obtained. The precipitate can be dried and further calcined to produce a catalyst.
Although any of the above manufacturing methods can solve the problem without any problem, the latter is preferable from the viewpoint of simplicity of manufacturing.

  Here, for drying the mixture, a drying method using a general dryer can be used regardless of the temperature or the drying method. In addition, since the mixture after mixing the alumina contains a large amount of water, it is heated to 40 to 50 ° C. under reduced pressure using an evaporator or the like before drying at a time in a dryer or the like. Most of the water may be dried. The dried mixture may be subjected to coarse pulverization, if necessary, and then fired.

  The firing of the mixture can be performed in air, and the temperature may be in the range of 800 to 1300 ° C. More preferably, it is 900 to 1150 ° C. If the sintering temperature is high, the sintering of the mixture proceeds and the strength increases, but the specific surface area decreases and the catalytic activity decreases. Therefore, it is desirable to determine the balance in consideration of the balance. After firing, it can be used as a catalyst as it is, but if necessary, it can be molded by press molding or the like and used as a molded product. It should be noted that a molding step may be added between the drying and the firing, if necessary, and firing may be performed after the molding.

  In the production of the reforming catalyst of the present invention, when the weight of the produced oxide is 100%, the weight of the mixed alumina is subtracted, and the remaining weight of the catalyst is present as a NiMgO solid solution. It is preferable that the metal in the nickel compound and the magnesium compound is adjusted to a predetermined molar ratio so that nickel and magnesium in the solid solution have a predetermined molar ratio, and the production is preferable. That is, when preparing 10 g of a catalyst having a molar ratio of nickel / magnesium of 0.1 / 0.9 and a mixed amount of alumina of 10% by mass, 1 g becomes alumina weight, 9 g becomes NiMgO, and 9 g of NiMgO is prepared. It is preferable that a nickel compound and a magnesium compound are mixed so as to have a molar ratio of 0.1 / 0.9, and a precipitant is added to obtain a precipitate.

Further, under the condition that the amount of alumina was adjusted so that the content of alumina in the reforming catalyst was 5 to 30% by mass, the molar ratio of nickel to magnesium was 0.05 / 0.95 to 0.3. It is necessary to adjust so as to be in the range of /0.7. That is, if the nickel content is too small, sufficient performance cannot be obtained, so the molar ratio of nickel needs to be 0.05 or more. Since the higher the nickel content, the higher the activity, the molar ratio of nickel is more preferably 0.1 or more, and further preferably 0.2 or more. However, if the molar ratio of nickel is 0.3 or more, the performance tends to be saturated, and carbon deposition tends to increase. Therefore, the molar ratio of nickel to magnesium is 0.2 / 0.8 to 0.8 / 0.8. It is more preferable to adjust so as to be 0.3 / 0.7. When the molar ratio is in the range of 0.05 / 0.95 to 0.3 / 0.7, light hydrocarbons containing sulfur compounds can be reformed with high performance and stability, and the conventional problems can be solved without any problem. Solvable.
In the present invention, when calculating the mass ratio in the reforming catalyst, the mass of the reforming catalyst as a parameter is the mass of the fired catalyst.

  Here, the reforming catalyst of the present invention preferably has a nickel content of 4.9 to 23.6% by mass as an active component. If the amount is less than 4.9% by mass, the reforming performance of nickel is not sufficiently exhibited, which is not preferable. If the content exceeds 23.6% by mass, the content of magnesium and aluminum forming the matrix is reduced, so that the fine particles of nickel metal deposited on the catalyst tend to be coarsened, and the performance deteriorates with time under the reaction conditions. There is a fear.

  Further, the content of magnesium is preferably 28.9 to 52.2% by mass. If the amount is less than 28.9% by mass, it tends to be difficult to maintain the catalyst performance stably for a long time by making use of the properties of the basic oxide of magnesium. On the other hand, if it exceeds 52.2%, the content of other nickel and aluminum is reduced, so that the catalyst may not be able to exhibit its reforming activity sufficiently.

Further, the content of alumina is preferably 5 to 30% by mass. If the content is less than 5% by mass, nickel-magnesia-based ceramics will be formed, and the NiAl ₂ O ₄ and MgAl ₂ O ₄ crystal phases will be reduced in the matrix. If the content exceeds 30% by mass, the content of nickel, which is the main active component, is reduced, so that the reforming activity of the catalyst cannot be sufficiently exhibited.

  The reforming catalyst of the present invention has a nickel content of 5.6 to 33.0% by mass, a magnesium content of 23.5 to 52.2% by mass, and an alumina content of 5 to 20% by mass. It is more preferable to manufacture it. The alumina referred to here is added in the form of alumina sol or alumina powder to the precipitate of hydroxide of nickel and magnesium, or coprecipitated with nickel and magnesium. In the case of adding with alumina sol, it is preferable to use alumina particles having an average particle size of 100 nm or less. The particle size distribution of alumina having such a particle size can be determined by using a laser diffraction type particle size distribution measuring device (for example, Mastersizer 3000 manufactured by Malvern). When the powder is added, the particle size is preferably as small as possible. For example, the average particle size is preferably 100 μm or less. At the time of mixing, water and the like can be added to use the slurry. Also in this case, the particle size distribution of the alumina particle size can be confirmed using a Coulter type particle size distribution measuring device (for example, Multisizer 4 manufactured by Beckman Coulter) in addition to using the laser diffraction type particle size distribution measuring device described above. In addition, in order to adjust the content of each metal species so as to be within the above range, it is preferable to prepare in advance by calculating each starting material. It should be noted that once the catalyst has the desired component composition, the catalyst may be prepared by the subsequent blending.

  Table 1 shows mass% of nickel, magnesium, and alumina in a typical composition. Assuming that the total amount of the catalyst is 100 mass%, mass% of nickel and magnesium as metals and mass% of alumina as oxides are shown. I have.

  In addition to the above-mentioned elements, unavoidable impurities to be mixed in the catalyst manufacturing process and the like, and other components may be contained at, for example, 5% by mass or less as long as the effect of solving the problem is not impaired. It is desirable.

  Here, the reforming catalyst produced in the present invention may be in the form of a powder, or a molded article, and in the case of a molded article, may be spherical, pellet, cylinder, ring, wheel, or the like. . When used on a fixed bed, granulation, extrusion molding, press molding, tablet molding and the like can be suitably used as the molding method, but are not particularly limited thereto.

<Method of Reforming Hydrocarbon Using Catalyst for Reforming Hydrocarbon>
Next, a method for reforming light hydrocarbons using the reforming catalyst of the present invention will be described. In this reforming method, a light hydrocarbon containing a sulfur compound is brought into contact with steam in the presence of a catalyst obtained by reducing the above-described catalyst, and the light hydrocarbon is reformed to produce hydrogen, carbon monoxide, and the like. . When the light hydrocarbon is methane, steam reforming proceeds with steam as represented by the equation (1).

CH ₄ + H ₂ O → 3H ₂ + CO (1)

Further, a water gas shift reaction such as the formula (2) also proceeds as a side reaction.
CO + H ₂ O → H ₂ + CO ₂ (2)

  Not only methane but also other light hydrocarbons such as ethane, ethylene, propane, propylene, normal butane, and isobutane other than methane contained in city gas and LPG, the same reaction proceeds. Can be modified.

  Here, the conditions for reducing the catalyst are as follows: the nickel particles, which are active metals, are precipitated from the catalyst of the present invention in a fine cluster form from the matrix. Although not limited, it is common to use hydrogen, or even under a gas atmosphere in which water vapor is mixed with hydrogen, or under an atmosphere in which an inert gas such as nitrogen is mixed with those gases. Good. The reduction temperature is preferably from 700 to 1000C, and more preferably from 750 to 900C. The reduction time depends on the amount of the catalyst to be charged and the flow rate of the reducing gas to be brought into contact with the catalyst. For example, it is practically preferable to perform the reduction for about 30 minutes to 1 hour.

  As the catalyst reactor, a fixed bed type, a fluidized bed type, a moving bed type or the like can be suitably used, and the inlet temperature of the catalyst layer is preferably 500 to 900 ° C. If the inlet temperature of the catalyst layer is lower than 500 ° C., the activity of reforming light hydrocarbons into hydrogen or carbon monoxide is hardly exhibited, which is not preferable. On the other hand, when the temperature exceeds 900 ° C., the reformer becomes expensive, for example, a heat-resistant structure is required, which is economically disadvantageous.

  The reaction pressure is not particularly limited, but it is preferable to carry out the reaction under the conditions of 0.1 to 0.3 MPa (absolute pressure). It is preferable that the hydrocarbon reforming reaction proceeds under pressurization that can be reformed with high productivity and a compact device. However, in a compact system such as a fuel cell, the motor of the compressor must be operated under the condition of increasing the pressure. Since power consumption also increases, leading to an increase in running cost, it is preferable to set the pressure to 0.3 MPa or less. Further, under a pressure of less than 0.1 MPa, there is a problem that productivity is low, although the direction is advantageous in terms of equilibrium.

  When the reforming catalyst of the present invention is used, the reforming reaction of the light hydrocarbon containing the sulfur compound proceeds stably. For example, a sulfur compound is used as an odorant in city gas or LPG, and mercaptans such as tertiary butyl mercaptan (TBM) and sulfides such as dimethyl sulfide (DMS) are used. It is contained in. Usually, in order to suppress poisoning of the catalytically active component by sulfur, hydrocarbons are reformed by reducing the above substances by a desulfurization step. However, the reforming catalyst of the present invention does not require a deflow step. It is also believed that any sulfur compounds will decompose on the active sites of the catalyst and that sulfur can be a poison.

  On the other hand, the reforming catalyst for hydrocarbons filled in the catalytic reactor has the effect that carbon or sulfur components that precipitate on the catalyst surface during the conversion of hydrocarbons to hydrogen, carbon monoxide, etc. are adsorbed by the catalytically active components. As a result, the performance of the catalyst deteriorates. Therefore, as a method for regenerating the deteriorated catalyst, air or steam is introduced into the catalytic reactor, and carbon on the catalyst is removed by the reaction of oxygen or steam in the air with carbon, or the reaction of oxygen or steam with sulfur. By removing sulfur adsorbed on the catalyst, the catalyst can be regenerated. Further, the regenerated catalyst is reduced again with hydrogen to cause fine precipitation of nickel metal clusters. By reacting the hydrogen with sulfur on the catalyst, it is possible to remove sulfur on the catalyst. .

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples. Note that Examples 7, 8, 8, 14, 15, and 19 are reference examples.

(Example 1)
6.32 g of nickel nitrate hexahydrate and 50.12 g of magnesium nitrate hexahydrate were precisely weighed so that the molar ratio of each metal element between nickel nitrate and magnesium nitrate was 0.1: 0.9. Then, dissolved in 500 mL of 60 ° C. pure water, and prepared a mixed aqueous solution heated to 60 ° C., precisely weighed 30.0 g of potassium carbonate, dissolved in 250 mL of 60 ° C. pure water, An aqueous solution of potassium carbonate heated to 60 ° C. was slowly added to about 250 mL / min, and nickel and magnesium were coprecipitated as hydroxides, and sufficiently stirred at about 400 rpm with a stirring blade. Thereafter, the mixture was aged by continuing stirring for about one hour while maintaining the temperature at 60 ° C., followed by suction filtration, and washing and suction filtration with pure water at 80 ° C. several times. The washing can be confirmed by using a portable pH meter or pH test paper to confirm that the pH of the filtrate is neutral. After that, the obtained precipitate was dispersed in pure water of about 400 mL of pure water, and alumina sol was added so as to have a concentration of 5% by mass as alumina, and the mixture was sufficiently mixed at about 350 rpm with a stirring blade, transferred to an eggplant flask, and rotated. Water was evaporated by attaching to an evaporator and heating to about 50 ° C. under reduced pressure. The mixture of nickel, magnesium, and alumina solidified in the eggplant flask was transferred to an evaporating dish, dried at 120 ° C. for about 24 hours, pulverized in a mortar, transferred to a crucible, and then placed in air at 950 ° C. for about 20 hours Calcination was performed to obtain a catalyst in which 5% by mass of alumina was mixed with Ni _0.1 Mg _0.9 O. The obtained catalyst powder was press-molded into tablets having a diameter of 20 mm using a pressure molding machine, and the press-molded body was roughly pulverized to adjust the particle size to 0.5 to 1.0 mm using a sieve. The components of the obtained catalyst are shown in Table 2 together with the respective examples and comparative examples, where the total amount of the catalyst is 100% by mass, and the mass% of nickel and magnesium as metals and the mass% of alumina as oxides are shown. ing.

  Using 0.08 mL of the catalyst obtained above, fix it so as to be sandwiched by quartz wool so as to be located at the center of a quartz reaction tube having an inner diameter of 6 mm and a length of 500 mm. A thermocouple was inserted, and the fixed bed reaction tubes were set at the center of the electric furnace.

Before starting the reforming reaction, the reactor was first heated to 800 ° C. under a nitrogen atmosphere, and then subjected to a reduction treatment for 30 minutes while flowing hydrogen at 100 mL / min. Then, while maintaining the temperature at 800 ° C., 14 mL of methane and 3 ppm of H ₂ S at normal pressure were used, and pure water was precision pumped so that (molar number of steam) / (molar number of carbon of methane) = 3. The experiment was conducted at a reaction pressure of 0.1 MPa for 24 hours while introducing steam at 42 mL / min. Here, H ₂ S was used as a catalyst poisoning substance due to ease of handling in experiments and the like. The space velocity (SV: Space Velocity) representing the gas introduction rate per catalyst volume under these conditions is 40,000 h ^−1, which is an acceleration test condition at a flow rate that is about 10 times that of ordinary hydrogen production conditions. The product gas discharged from the catalytic reactor was passed through an ice temperature trap to remove water, and then subjected to TCD gas chromatography (Yanaco G2800, column: inner diameter 2 mmφ, length 4 m, SHIN CARBON ST, column temperature 120 ° C., TCD detector Gas analysis was performed using an Ar carrier at 140 ° C.). The activity of the reforming reaction was evaluated based on the methane conversion rate, and was calculated from the concentration of each gas component in the outlet gas by the following equation.

  The methane conversion in Example 1 is shown in Table 2 As in 2, the methane conversion could be maintained at 70% even after 24 hours. Note that the content (% by mass) of each element shown in Table 2 is a calculated value, but a method called an inductively coupled plasma method (ICP) can be used as a method for measuring an actually measured value. Specifically, after the sample is pulverized, an alkali melting agent (for example, sodium carbonate, sodium borate, etc.) is added and heated and melted in a platinum crucible. After cooling, the whole is dissolved in a hydrochloric acid solution while heating. When the solution is inserted into the ICP analyzer, the sample solution is atomized and thermally excited in the high-temperature plasma state inside the apparatus, and when this returns to the ground state, an emission spectrum with a wavelength specific to the element is generated. The element type and amount contained can be qualitatively and quantitatively determined from the strength and strength.

(Example 2)
The evaluation was performed in the same manner as in Example 1 except that the catalyst was a mixture of Ni _0.1 Mg _0.9 O and 10% by mass of alumina. As a result, in Table 2 No. As shown in FIG. 3, it was found that the methane conversion could be maintained at 80% even after 24 hours, and the highest activity could be maintained.

(Example 3)
The evaluation was performed under the same conditions as in Example 1 except that the catalyst was prepared by mixing 20 mass% of alumina with Ni _0.1 Mg _0.9 O in Example 1. As a result, in Table 2 No. As shown in FIG. 4, the methane conversion could be maintained at 71% even after 24 hours.

(Example 4)
The evaluation was performed under the same conditions as in Example 1 except that the catalyst was a mixture of Ni _0.1 Mg _0.9 O and 30% by mass of alumina. As a result, in Table 2 No. As shown in Fig. 5, the methane conversion could be maintained at 58% even after 24 hours.

(Comparative Example 1)
In Example 1, the evaluation was performed under the same conditions as in Example 1 except that the catalyst was not mixed with Ni _0.1 Mg _0.9 O without alumina. As a result, in Table 2 No. As in 1, methane conversion depression was reduced to 40% at 7 hours and was very low in activity.

(Comparative Example 2)
All the evaluations were performed under the same conditions as in Example 1 except that the catalyst was a mixture of Ni _0.1 Mg _0.9 O and 40% by mass of alumina. As a result, in Table 2 No. As in 6, the methane conversion could be maintained for 24 hours, but dropped to 18%.

(Comparative Example 3)
All the evaluations were performed under the same conditions as in Example 1 except that the catalyst was a mixture of Ni _0.1 Mg _0.9 O and 50% by mass of alumina. As a result, in Table 2 No. As in 7, the methane conversion was 0% at 21 hours.

(Example 5)
In Example 1, except that nickel and magnesium were used as catalysts in which alumina was mixed with 10% by mass of Ni _0.06 Mg _0.94 O in which the molar ratio of each metal was 0.06: 0.94, All were evaluated under the same conditions as in Example 1. As a result, in Table 3, No. As shown in Fig. 8, it was found that the methane conversion could be maintained at 72% even after 24 hours, and high activity could be maintained.

(Example 6)
Except that in Example 1, nickel and magnesium were used as catalysts in which alumina was mixed with 10 mass% of Ni _0.2 Mg _0.8 O in which the molar ratio of each metal was 0.2: 0.8. All were evaluated under the same conditions as in Example 1. As a result, in Table 3, No. As shown in FIG. 9, it was found that the methane conversion could be maintained at 96% even after 24 hours, and high activity could be maintained.

(Example 7)
In the preparation of the catalyst, nickel salt, magnesium nitrate, and aluminum nitrate were mixed with 5.983 g of nickel nitrate hexahydrate and magnesium nitrate so that the molar ratio of each metal element was 0.091: 0.822: 0.087. 67.479 g of hexahydrate and 7.358 g of aluminum nitrate 9-hydrate were precisely weighed and dissolved in 500 mL of 60 ° C pure water to prepare a mixed aqueous solution heated to 60 ° C. To this mixed aqueous solution, 29.4 g of potassium carbonate was precisely weighed, dissolved in 250 mL of pure water at 60 ° C., and an aqueous potassium carbonate solution heated to 60 ° C. was slowly added at about 250 mL / min to obtain nickel, magnesium, and aluminum. Was coprecipitated as a hydroxide and sufficiently stirred at about 400 rpm with a stirring blade. Thereafter, the mixture was aged by continuing stirring for about one hour while maintaining the temperature at 60 ° C., followed by suction filtration, and washing and suction filtration with pure water at 80 ° C. several times. The temperature of each aqueous solution was measured by inserting an alcohol thermometer into the aqueous solution. The washing can be confirmed by using a portable pH meter or pH test paper to confirm that the pH of the filtrate is neutral.

Thereafter, the obtained precipitate was transferred to an eggplant flask, attached to a rotary evaporator, and heated to about 50 ° C. under reduced pressure to evaporate water. The mixture of nickel, magnesium and alumina solidified in the eggplant flask was transferred to an evaporating dish and dried at an ambient temperature of 120 ° C. for about 24 hours. Then, after pulverizing in a mortar, the powder is transferred to a crucible, and calcined at an atmospheric temperature of 950 ° C. for about 20 hours, and about 10 g of a catalyst corresponding to 10% by mass of alumina mixed with Ni _0.1 Mg _0.9 O is added. Obtained. The obtained catalyst powder was press-molded into tablets having a diameter of 20 mm using a pressure molding machine, and the press-molded body was roughly pulverized to adjust the particle size to 0.5 to 1.0 mm using a sieve. Table 4 shows the components of the obtained catalyst.

  The catalyst thus obtained was subjected to a reforming reaction in the same manner as in Example 1. As a result, as shown in Example 7 in Table 4, the conversion was 78.4% at the time of the reaction for 24 hours, and even if the preparation method was different, high activity could be maintained as in Example 2 having the same catalyst composition. I understood.

(Example 8)
In the preparation of the catalyst, a reforming reaction was carried out in the same manner as in Example 7, except that a catalyst corresponding to 10% by mass of alumina mixed with Ni _0.2 Mg _0.8 O was used. As a result, as shown in Example 8 of Table 4, the conversion was 97.8% at the time of the reaction for 24 hours, and even if the preparation method was different, high activity could be maintained as in Example 6 having the same catalyst composition. I understood.

(Comparative Example 4)
An oxide obtained by impregnating an aqueous solution of nickel nitrate with alumina powder to a concentration of 20% by mass was transferred to an evaporating dish and dried at 120 ° C. for about 24 hours. Then, the powder was transferred to a crucible at 500 ° C. Evaluation was performed under the same conditions as in Example 1 except that the nickel / alumina catalyst was obtained by firing for a time. As a result, in Table 5, No. As in 12, the methane conversion was 0% at 10 hours. It can be seen that the activity of the catalyst by the conventional loading method is extremely low.

(Comparative Example 5)
The oxide impregnated with an aqueous solution of acetylacetonate toruthenium in alumina powder to a concentration of 5% by mass was transferred to an evaporating dish and dried at 120 ° C. for about 24 hours. The powder was transferred to a crucible at 500 ° C. in air. The evaluation was performed under the same conditions as in Example 1 except that calcination was performed for about 20 hours to obtain a ruthenium / alumina catalyst. As a result, in Table 6, No. As in 13, the methane conversion was 75.7%. Although the performance is equivalent to the performance of the catalyst of the present invention, since it is a noble metal, the cost of the catalyst is high, and the present invention can be manufactured at lower cost.

(Comparative Example 6)
An aqueous solution of platinum acetylacetonate in alumina powder impregnated with 5% by mass of an oxide was transferred to an evaporating dish, dried at 120 ° C. for about 24 hours, and then transferred to a crucible at 500 ° C. in air. The evaluation was performed under the same conditions as in Example 1 except that firing was performed for about 20 hours to obtain a platinum / alumina catalyst. As a result, as shown in Table 7, As in 14, the methane conversion was 82.5%. Although the performance is equivalent to the performance of the catalyst of the present invention, since the catalyst is more expensive than the ruthenium of Comparative Example 5, the catalyst cost is higher, and the present invention can be manufactured at lower cost.

(Comparative Example 7) NiCeMgO-based catalyst Nickel nitrate, cerium nitrate, and magnesium nitrate were precisely weighed so that the molar ratio of each metal element was 0.1: 0.1: 0.8, and heated at 60 ° C. An aqueous solution of potassium carbonate heated to 60 ° C. was slowly added to the mixture prepared at room temperature, and nickel, cerium, and magnesium were coprecipitated as hydroxides and sufficiently stirred with a stirring blade. Thereafter, the mixture was aged by continuing stirring for a certain period of time while maintaining the temperature at 60 ° C., followed by suction filtration, and washing with pure water at 80 ° C. sufficiently. Then, alumina sol was added to the obtained precipitate in an amount of 50% by mass as alumina, and the mixture was sufficiently mixed with a stirring blade, transferred to an eggplant flask, attached to a rotary evaporator, and heated to about 50 ° C. under reduced pressure. As a result, water was evaporated. The mixture of nickel, cerium, magnesium, and alumina solidified in the eggplant flask was transferred to an evaporating dish, dried at 120 ° C. for about 24 hours, crushed in a mortar, and then transferred to a crucible at 950 ° C. in air. The firing was performed for 20 hours to obtain a catalyst in which alumina was mixed with Ni _0.1 Ce _0.1 Mg _0.8 O at 50% by mass. The obtained catalyst powder was press-molded into a tablet having a diameter of 20 mm using a pressure molding machine, and the pressed compact was roughly crushed to adjust the particle size to 0.5 to 1.0 mm. Evaluation was performed under the same conditions.

  No. of Table 8 From the result of No. 15, it was found that the sample deteriorated in a shorter time than Comparative Example 3 in which cerium was not added (Table 1, No. 7).

(Comparative Example 8)
In Comparative Example 7, an alumina sol was added so that 30 mass% of _alumina, except that alumina Ni _0.1 Ce _0.1 Mg0.8O obtain 30 wt% mixed catalyst, the same as in Example 1 The condition was evaluated.

  As a result, as shown in Table 8, As shown in FIG. 15, the methane conversion rate became 0 in 17 hours, and the deterioration was achieved in a very short time as compared with Example 4 (Table 1, No. 5) in which cerium was not added and the same amount of alumina was mixed. It turned out to be.

  From the above results, it was found that the activity of the catalyst to which cerium was added, which had conventionally been highly active as a tar reforming catalyst, deteriorated very quickly.

(Example 9)
Using the catalyst prepared by mixing Ni _0.1 Mg _0.9 O with 10% by mass of alumina prepared in Example 2, in the reforming reaction of Example 1, the simulated city gas (methane was 89.6% , Ethane 5.6%, propane 3.4%, and normal butane 1.4%) in a concentration of 12 ml and H2S at 3 ppm. (Moles of water vapor) / (moles of carbon in the simulated city gas) The experiment was performed at a reaction pressure of 0.1 MPa for 24 hours while introducing pure water as steam at 42 ml / min with a precision pump so that (number) = 3. The space velocity (SV) representing the gas introduction velocity per catalyst volume under these conditions is 40,000 h ^-1, which is an acceleration test condition at a flow rate that is about 10 times that of ordinary hydrogen production conditions. As a result, in Table 9 No. As shown in FIG. 17, even after 24 hours, the methane conversion was kept at 91%, and the conversion of ethane, propane and butane was 99% or more. Even when the source gas was a city gas component, it showed high activity as well as methane alone. Ethane, propane, and butane are easily decomposed and have a problem of increasing the amount of carbon deposition. However, the catalyst according to the present invention had a carbon deposition rate of 1% by mass or less even after an acceleration test for 24 hours.

(Example 10)
A reforming reaction was carried out in the same manner as in Example 9 using a catalyst prepared by mixing Ni _0.2 Mg _0.8 O with 10% by mass of alumina prepared in Example 6. As a result, in Table 9 No. As shown in FIG. 18, the conversion of methane remained 97% even after 24 hours, and the conversions of ethane, propane and butane were almost 100%. It exhibited higher activity and longer life than Example 7. Ethane, propane, and butane are easily decomposed and have a problem of increasing the amount of carbon deposition. However, the catalyst of the present invention had a carbon deposition rate of about 2% by mass even after an acceleration test for 24 hours.

(Example 11)
In Example 1, except that a catalyst in which 5% by mass of alumina was mixed with Ni _0.2 Mg _0.8 O in which the molar ratio of each metal was 0.2: 0.8 with nickel and magnesium was used. A reforming reaction was performed in the same manner as in Example 9. As a result, in Table 9 No. As shown in FIG. 19, the methane conversion was maintained at 93% even after 24 hours, and the conversion of ethane, propane and butane was 98% or more. Ethane, propane, and butane are easily decomposed and have a problem of increasing the amount of carbon deposition. However, the catalyst of the present invention had a carbon deposition rate of about 2.5% by mass even after a 24-hour acceleration test.

(Example 12)
In Example 1, except that a catalyst in which 30% by mass of alumina was mixed with Ni _0.2 Mg _0.8 O, in which the molar ratio of nickel and magnesium was 0.2: 0.8, was used. A reforming reaction was performed in the same manner as in Example 9. As a result, in Table 9 No. As shown in FIG. 20, the methane conversion was maintained at 89% even after 24 hours, and the conversions of ethane, propane and butane were 95% or more. Ethane, propane, and butane are easily decomposed and have a problem of increasing the amount of carbon deposition. However, the catalyst of the present invention had a carbon deposition rate of about 1.8% by mass even after a 24-hour acceleration test.

(Example 13)
In Example 1, nickel and magnesium were mixed using a catalyst in which alumina was mixed with 10 mass% of Ni _0.3 Mg _0.7 O in which the molar ratio of each metal was 0.3: 0.7. A reforming reaction was performed as in Example 7. As a result, in Table 9 No. As shown in FIG. 21, the methane conversion was maintained at 99.2% even after 24 hours, and the conversion of ethane, propane and butane was 100%. It exhibited higher activity and longer life than Example 8. Ethane, propane, and butane are easily decomposed and have a problem of increasing the amount of carbon deposition. However, the catalyst of the present invention had a carbon deposition rate of about 3% by mass even after an acceleration test for 24 hours.

(Example 14)
With alumina were mixed 10 mass% catalyst _Ni 0.1 _{Mg 0.9} O prepared in Example 7, in the same manner as in Example 9 was subjected to reforming reaction. As a result, in Table 10 No. As in No. 22, the methane conversion was maintained at 90% even after 24 hours, and the conversions of ethane, propane, and butane were 95% or more. Ethane, propane, and butane are easily decomposed and have a problem of increasing the amount of carbon deposition. However, the catalyst of the present invention had a carbon deposition rate of about 1.8% by mass even after a 24-hour acceleration test. Other catalyst preparation methods also exhibited high activity.

(Example 15)
A reforming reaction was carried out in the same manner as in Example 9 using a catalyst prepared by mixing Ni _0.2 Mg _0.8 O with 10% by mass of alumina prepared in Example 8. In this example, the reaction was performed for up to 48 hours. As a result, in Table 10 No. As in the case of No. 23, the conversion rate of methane, ethane, propane, and butane over 24 hours was 99% or more. Furthermore, even after 48 hours, the methane conversion was 98%, the ethane conversion was 99%, and the conversions of propane and butane were 100%. The catalyst of the present invention had a carbon deposition rate of about 0.6% by mass even after the accelerated test for 48 hours. Other catalyst preparation methods also exhibited high activity.

(Comparative Example 9)
Using the nickel / alumina catalyst prepared in Comparative Example 4, a reforming reaction was carried out in the same manner as in Example 7. As a result, in Table 11 No. As in the case of Comparative Example 4, the conversion of methane became 0% in about 12 hours, and the conversion of ethane, propane and butane also decreased to several%, as in Comparative Example 4. Further, the carbon deposition rate was as large as 12% by mass.

(Example 16)
In a reforming reaction of Example 1, propane gas (98% propane, ethane was 98%) was used in the reforming reaction of Example 1 using a catalyst in which alumina was mixed with 10% by mass of Ni _0.2 Mg _0.8 O prepared in Example 6. 5.7 ml of 0.4%, 1.6% of isobutane, and 8 ppm of sulfur), and purified water was precisely purified so that (molar number of steam) / (molar number of carbon in the simulated city gas) = 3. The experiment was conducted at a reaction pressure of 0.1 MPa for 24 hours while introducing 51.5 ml / min as steam with a pump. Here, 8 ppm of sulfur is added to propane gas as an odorant. The space velocity (SV) representing the gas introduction velocity per catalyst volume under these conditions is 40,000 h ^-1, which is an acceleration test condition at a flow rate that is about 10 times that of ordinary hydrogen production conditions. As a result, in Table 12 No. As shown in FIG. 25, even after 24 hours, the conversion of propane was 98%, and the conversion of ethane and butane was 100%. Even when the raw material gas was propane gas, only methane or high activity was exhibited as in the case of city gas components.

(Example 17)
A reforming reaction similar to that in Example 16 was performed using a catalyst in which 5% by mass of alumina was mixed with Ni _0.2 Mg _0.8 O prepared in Example 11. As a result, even after 24 hours, the conversion of propane was maintained at 95%, and the conversion of ethane and butane was 100%. Even when the raw material gas was propane gas, only methane or high activity was exhibited as in the case of city gas components.

(Example 18)
The same reforming reaction as in Example 16 was performed using a catalyst in which 30% by mass of alumina was mixed with Ni _0.2 Mg _0.8 O prepared in Example 12. As a result, even after 24 hours, the conversion of propane was maintained at 95%, and the conversion of ethane and butane was 100%. Even when the raw material gas was propane gas, only methane or high activity was exhibited as in the case of city gas components.

(Example 19)
The same reforming reaction as in Example 16 was performed using a catalyst corresponding to 10% by mass of alumina mixed with Ni _0.2 Mg _0.8 O prepared in Example 8. As a result, even after 24 hours, the conversion of propane was maintained at 98%, and the conversion of ethane and butane was almost 100%. Even with the catalyst prepared by another catalyst preparation, even when the raw material gas was propane gas, only methane or a high activity was exhibited similarly to the city gas component.

  FIG. 1 is a graph showing the relationship between the methane conversion (%) and the reforming reaction time (h) obtained in the comparative example and the examples (test Nos. 1 to 7). The relationship between the conversion (%) of hydrocarbons such as methane obtained in Examples 9 and 10 and the reforming reaction time (h) is shown in the graphs of FIGS. FIG. 4 shows the relationship between the conversion (%) of hydrocarbons such as methane obtained in Example 15 and the reforming reaction time (h).

Claims (5)

A precipitant is added to a mixed solution in which the molar ratio of the nickel compound and the magnesium compound is 0.05 / 0.95 to 0.3 / 0.7 in a molar ratio of nickel and magnesium, and nickel and magnesium are added. Coprecipitation of magnesium to form a hydrate precipitate,
Alumina sol or alumina powder and water are added to the precipitate so as to have an alumina content of 5 to 30% by mass in the obtained light hydrocarbon reforming catalyst, and mixed to form a mixture. And
Using a catalyst for reforming light hydrocarbons produced by drying and calcining the mixture,
A method for reforming light hydrocarbons, comprising reforming light hydrocarbons to obtain hydrogen and carbon monoxide. The ratio between the nickel compound and the magnesium compound is 0.2 / 0.8 to 0.3 / 0.7 (that is, Ni / Mg = 0.25 to 0.43) in a molar ratio of nickel and magnesium. The light hydrocarbon reforming method according to claim 1, wherein the light hydrocarbon reforming catalyst produced as described above is used. The method for reforming a light hydrocarbon according to claim 1 or 2, wherein a catalyst for reforming the light hydrocarbon produced so as to have an alumina content of 5 to 20% by mass is used. The method for reforming a light hydrocarbon according to any one of claims 1 to 3, wherein the light hydrocarbon contains a sulfur compound. The light hydrocarbon reforming method according to claim 4, wherein the light hydrocarbon is a methane-containing gas.

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