catalyst particles

Abstract

To improve a manufacturing efficiency of a desired product by reducing attachment of catalyst particles to an interior of a furnace in a reaction performed by flowing the particles into the furnace and to make the reaction efficiently proceed by using the catalyst particles like this.SOLUTION: Catalyst particles of the present invention are catalyst particles which are heated in a furnace while flowing and are used for the conversion of a raw material gas introduced into the furnace, and powder XRD shows at least one or more of an iron oxide phase, an iron hydroxide phase, a spinel type ferrite phase, and an Fe-containing composite hydroxide phase, and a total of a collapsing angle and a spatula angle is 85° or smaller, and the spatula angle is 61.5°or smaller.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to catalyst particles for thermal cracking or conversion of hydrocarbons, and more particularly to Fe-containing catalyst particles suitable for thermal reactions in a fluidized state, and a method for producing hydrogen using the same. [Background technology]

[0002] Conventionally, various furnaces have been used to heat-treat materials such as gases and solids to obtain desired products. For example, Patent Document 1 describes the production of hydrogen, carbon monoxide, methane, and the like by using a continuous fixed-bed catalytic reactor including a reactor vessel as a furnace, the reactor vessel containing a catalyst layer supported by a retainer, and heating a hydrocarbon-containing gas in the reactor vessel.

[0003] Patent Document 2 describes a method for producing carbon nanotubes on catalyst particles by introducing a raw material gas containing hydrocarbons such as ethylene into a rotary furnace together with catalyst particles and heating the catalyst particles while causing them to flow by rotation. Furthermore, Patent Document 3 describes a method for producing nanocarbons and hydrogen by reforming methane using a screw-type catalytic reactor equipped with a screw feeder in a reactor vessel as a furnace.

[0004] In Patent Documents 2 and 3, catalyst particles and raw material gas are continuously introduced into a rotary furnace, while carbon nanotubes or nanocarbon deposited on the catalyst are continuously discharged from the reaction vessel. In particular, in reactions in which such products are deposited on the catalyst, the contact area between the catalyst and the raw material gas gradually decreases, reducing the reaction efficiency. However, in Patent Documents 2 and 3, fresh catalyst is introduced while the catalyst particles on which the products are deposited are discharged, allowing for a continuous, highly efficient reaction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-166106 [Patent Document 2] Special Publication No. 2013-518015 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-116656 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the reactions described in Patent Documents 2 and 3, although the catalyst particles are fluidized by the rotation of the furnace or the screw, the catalyst particles may adhere to the inner wall of the furnace or the blades of the screw. If this happens, the catalyst particles and the products deposited thereon remain undischarged, resulting in a decrease in the overall reaction efficiency and a decrease in the production efficiency of the desired product.

[0007] The present invention has been made in view of the above-mentioned problems, and its object is to reduce adhesion of catalyst particles to the inner walls of a furnace in a reaction carried out by flowing catalyst particles in the furnace, thereby improving the production efficiency of a desired product, and to efficiently proceed with the reaction using such catalyst particles. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides catalyst particles having an appropriate fluidity and being less likely to adhere to the inner wall of the furnace.

[0009] Specifically, the catalyst particles according to the present invention are catalyst particles that are heated while flowing in a furnace and are used to convert raw material gas introduced into the furnace, and are characterized in that, in powder XRD, they exhibit at least one of an iron oxide phase, an iron hydroxide phase, a spinel-type ferrite phase, and an Fe-containing layered double hydroxide phase, and the sum of the collapse angle and spatula angle is 85° or less, and the spatula angle is 61.5° or less.

[0010] The catalyst particles according to the present invention have a sum of the collapse angle and the spatula angle, which are indicators of particle fluidity, of 85° or less, and the spatula angle is 61.5° or less. Therefore, when the particles are used while being fluidized in a furnace, the particles flow appropriately within the furnace and are less likely to adhere to the inner walls of the furnace. Therefore, when the catalyst particles are continuously introduced into and discharged from the furnace, the catalyst particles can be prevented from adhering and remaining inside the furnace. Furthermore, because the catalyst particles have the appropriate fluidity as described above, contact with the raw material gas in the furnace can be improved, and the reaction to obtain the desired product can be efficiently promoted.

[0011] The method for producing hydrogen according to the present invention is characterized by comprising the steps of: introducing catalyst particles having a sum of a collapse angle and a spatula angle of 85° or less and a spatula angle of 61.5° or less and a raw material gas containing hydrocarbons into a furnace; heating the catalyst particles and the raw material gas while flowing the catalyst particles in the furnace; and recovering hydrogen generated by the heating.

[0012] The hydrogen production method according to the present invention uses catalyst particles having a sum of the collapse angle and the spatula angle, which are indicators of particle fluidity, of 85° or less, and the spatula angle being 61.5° or less, thereby preventing the catalyst particles from adhering and remaining in the furnace, as described above. This improves the accessibility of the catalyst particles to the hydrocarbon-containing feed gas, thereby accelerating the catalytic pyrolysis reaction of the hydrocarbons. As a result, the hydrogen yield can be improved.

[0013] In the catalyst particles according to the present invention, the iron oxide phase is preferably hematite.

[0014] In the catalyst particles according to the present invention, the iron hydroxide phase is preferably goethite.

[0015] In the catalyst particles according to the present invention, the layered double hydroxide phase is preferably hydrotalcite.

[0016] The catalyst particles according to the present invention preferably have an iron content of 5% or more and 80% or less.

[0017] In the catalyst particles according to the present invention, the raw material gas is C a H 2a+b (where a is a positive integer of 4 or less, and b is either -2, 0, or 2)

[0018] In the catalyst particles according to the present invention, the furnace may be a rotary kiln.

[0019] As described above, the catalyst particles according to the present invention have suitable fluidity and can effectively prevent particles from adhering to the furnace, and are therefore particularly effective when a rotary kiln is used, which fluidizes particles introduced into the furnace by rotation.

[0020] In the catalyst particles according to the present invention, the conversion of the raw material gas may be a reaction of thermally decomposing saturated hydrocarbons into hydrogen and solid carbon. [Effects of the Invention]

[0021] The catalyst particles according to the present invention have an appropriate fluidity, which reduces adhesion of the catalyst particles to the furnace interior and improves contact with the raw material gas, allowing the catalyst particles to efficiently promote the hydrogen generation reaction, thereby improving the efficiency of hydrogen production. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its application, or its uses.

[0023] A catalyst particle according to one embodiment of the present invention is characterized in that the sum of the collapse angle and spatula angle is 85° or less, and the spatula angle is 61.5° or less. It is used in applications where the particles are heated while flowing in a furnace, for example, as catalyst particles for hydrocarbon thermal cracking. The collapse angle and spatula angle are used as indicators of particle fluidity. The collapse angle is expressed as the angle between the slope (ridge) and the horizontal plane when a mountain-shaped particle layer collapses due to impact. Specifically, the collapse angle is expressed as the angle between the slope (ridge line) and the horizontal plane (surface of the table) of the collapsed particle layer when a predetermined impact is applied after particles are dropped onto a table through a funnel or the like to form a mountain-shaped particle layer. The higher the particle fluidity of the particles, the flatter the impacted mountain-shaped particle layer collapses, resulting in a smaller collapse angle. The preferred lower limit of the collapse angle is approximately 10°, with 15° or more being preferable, and 20° or more being more preferable. If the collapse angle is less than 10°, the movement of the powder during furnace rotation is reduced, resulting in poor contact with the raw material gas. The preferred upper limit of the collapse angle is approximately 30°, with 29° or less being preferred and 28° or less being even more preferred. A collapse angle exceeding 30° increases the contact time between the furnace wall and the powder, making it more likely to adhere. The spatula angle is expressed as (A + B) / 2, where A is the angle between the slope (ridge) of the particle layer deposited on a spatula after the spatula is slowly lifted and the horizontal plane (surface of the spatula), and B is the angle between the slope (ridge) of the particle layer collapsed by a predetermined impact and the horizontal plane (surface of the spatula). The higher the particle fluidity, the flatter the particle collapses when the spatula is lifted, making the spatula angle smaller. When using a flight or other device to scrape powder in a furnace, if the spatula angle exceeds 61.5°, the amount of powder lifted increases, making it more likely for catalyst particles to adhere to the furnace wall. The preferred lower limit of the spatula angle is about 30°, preferably 35° or more, and more preferably 40° or more. When stirring up powder in a furnace with a flight or the like, if the spatula angle is less than 30°, the amount of powder stirred up decreases, resulting in poor contact with the raw material gas.

[0024] The catalyst particles according to one embodiment of the present invention have a moderate fluidity because the sum of the collapse angle and the spatula angle is 85° or less, and the spatula angle is 61.5° or less. Therefore, when used in applications where the catalyst particles are heated while flowing in a furnace, they are less likely to adhere to the inner walls of the furnace. Therefore, when catalyst particles are continuously introduced into and discharged from the furnace, the catalyst particles can be prevented from adhering and remaining in the furnace. Furthermore, because the catalyst particles have a moderate fluidity, they can improve contact with the heated raw material gas in the furnace, efficiently promoting the reaction to obtain the desired product.

[0025] Another embodiment of the present invention is a method for producing hydrogen using catalyst particles having the above characteristics. The hydrogen production method according to this embodiment is characterized in that catalyst particles having the above characteristics and a feed gas containing hydrocarbons are introduced into a furnace, the catalyst particles and the feed gas are heated while the catalyst particles are flowing in the furnace, and the hydrogen generated thereby is recovered. Because the hydrogen production method according to the present invention uses catalyst particles having the above characteristics, the catalyst particles can be efficiently flowed in the furnace, improving their contact with the feed gas. As a result, the catalytic action of the catalyst particles can be efficiently exerted, and the hydrogen yield can be improved.

[0026] The furnace used in the catalyst particles and hydrogen production method according to one embodiment of the present invention produces hydrogen via a catalyst by introducing a feed gas. Any suitable device can be selected without particular limitations on its structure or principle, as long as it can fluidize the catalyst particles. Specifically, suitable devices include fluidized beds, which process materials by flowing them up and down in a vertically installed reaction tube; screw-type tubular furnaces and rotary kilns, which transport and fluidize materials horizontally in a long horizontal reaction tube, and other devices that promote solid-gas contact between catalyst particles and feed gas in the reaction field. In fluidized beds, solid-gas contact is promoted by the catalyst being fluidized by the feed gas blown up from below; in screw-type tubular furnaces, the catalyst and feed gas are mixed by the screw; and in rotary kilns, the catalyst is scraped up by shear or flight due to rotation. Depending on the device selected, any of a batch type, continuous type, and batch-continuous type may be used, but these are not particularly limited. In particular, when a rotary kiln or other rotary kiln is used, which has the problem of catalyst particles adhering to the furnace wall inside the furnace, particularly when a continuous or batch continuous rotary kiln is used, the effects obtained by the moderate fluidity of the catalyst particles of the present invention can be more significantly demonstrated.

[0027] The feedstock gas used in the catalyst particles and hydrogen production method according to this embodiment may be a hydrocarbon gas such as propane gas, liquefied natural gas (LNG), city gas, methane, ethylene, or acetylene. However, the feedstock gas may be any gas that produces hydrogen and solid carbon by thermal decomposition of the hydrocarbon via a catalyst. Furthermore, a reducing gas, an inert gas, or an oxidizing gas may be mixed with the feedstock gas to adjust the feedstock gas concentration or prevent catalyst deactivation. From the perspective of producing high-concentration hydrogen, the feedstock gas concentration contained in the gas introduced into the reaction field is preferably 60 vol% or more, more preferably 90 vol% or more, and even more preferably 95 vol% or more. In the present invention, hydrogen synthesis is preferably performed using the direct methane reforming (DMR) reaction, in which methane gas is directly thermally decomposed into solid carbon and hydrogen. In this reaction, methane gas is heated together with a catalyst, causing methane decomposition to produce hydrogen gas and solid carbon. This reaction is advantageous in that it does not generate carbon oxide gases such as carbon dioxide. Typically, solid carbon is produced in the form of layers on the surface of catalyst particles, and although its shape and crystallinity depend on the catalyst and other reaction conditions, it is preferable that at least a portion of it is fibrous crystalline carbon such as carbon nanotubes.

[0028] The catalyst particles according to this embodiment have the above characteristics and exhibit at least one of an iron oxide phase, an iron hydroxide phase, a spinel-type ferrite phase, and an Fe-containing layered double hydroxide phase in powder XRD. The iron oxide phase is preferably hematite, the iron hydroxide phase is preferably goethite, and the layered double hydroxide phase is preferably hydrotalcite. By containing these compounds, the catalyst particles have excellent catalytic ability and are easy to maintain activity in the conversion reaction of the feedstock gas.

[0029] The range of the particle diameter of the catalyst particles is not particularly limited as long as it is within the range in which they flow in the furnace, but the median diameter (d50) is preferably 1 μm to 10 mm, and particularly preferably 2.5 μm to 7 mm.

[0030] Various processing methods can be used to adjust the powder properties of the catalyst particles according to this embodiment. Examples of crushing processing devices that can be used to adjust the particle size and particle properties include cutter mills that crush by shear stress, pin mill type crushers (glow mills, mass colloiders, etc.) that crush by compressive shear stress, sand mills, mix mills, hammer mills (jaw crushers) that crush by impact, and jet mills, which are airflow crushers.

[0031] One embodiment of the hydrogen production method according to the present invention is described below. A continuous rotary kiln with a diameter of 250 mm is used as the furnace. The catalyst particles are made of iron oxide and have a sum of the collapse angle and spatula angle of 85° or less and a spatula angle of 61.5° or less. Methane gas is used as the hydrocarbon. In this embodiment, the catalyst particles are continuously supplied into the rotary kiln at a rate of 0.01 g / min to 7.5 g / min, and methane gas is continuously supplied at a rate of 0.5 L / min to 50 L / min. The gases may be supplied in multiple stages. The supplied catalyst particles and methane gas are heated to a temperature of 400°C to 800°C in the rotary kiln. This causes the methane to thermally decompose in the furnace via the catalyst, producing hydrogen and solid carbon. The generated hydrogen and the catalyst particles, with solid carbon deposited on their surfaces, are then continuously discharged from a supply port at one end of the rotary kiln and a discharge port at the opposite end. When a batch rotary kiln with a diameter of 150 mm is used, the catalyst is supplied in an amount of 0.01 g to 100 g, and the methane gas is supplied in an amount of 0.1 L / min to 50 L / min. Regardless of whether the rotary kiln is continuous, batch continuous, or batch, the rotation speed in the reaction section is about 0.1 rpm to 60 rpm.

[0032] In this hydrogen production method according to the present embodiment, the catalyst particles used have a sum of the collapse angle and spatula angle of 85° or less, and the spatula angle is 61.5° or less. Because the catalyst particles have adequate fluidity, they are prevented from adhering to the furnace interior and are properly discharged from the outlet of the rotary kiln after the reaction in the furnace. Furthermore, adequate fluidity in the furnace improves contact with methane gas, improving catalytic efficiency in the thermal decomposition reaction of methane. As a result, the yields of hydrogen and solid carbon can be improved. [Example]

[0033] Examples are given below to explain the catalyst particles according to the present invention in detail.

[0034] First, as raw materials for the catalyst particles, iron oxide (hematite) particles, metal oxide particles whose main component is iron oxide with an Al / Mg ratio of 0.4 and a total content of Al and Mg of 13 wt%, goethite particles, spinel ferrite particles, and Fe-containing layered double hydroxide were prepared.

[0035] Next, these raw materials were crushed or compressed under the predetermined processing conditions shown in Table 1 below (a: crushing using a high-speed mill (manufactured by Taninaka O&K Corporation), b: crushing in a mortar, c: compression by tapping 100 times, d: extrusion molding), to produce catalyst particles of the examples and comparative examples shown in Table 1 below. Table 1 shows the physical properties of the produced catalyst particles. Among the physical properties, the collapse angle was measured using a Powder Tester (registered trademark) (manufactured by Hosokawa Micron Corporation). The catalyst particles were dropped from a funnel onto a stand, and the pile of accumulated powder was impacted three times using the attached weight. The angle between the ridgeline and the stand was measured about 10 times, and the average value was taken as the collapse angle. The spatula angle was also measured using a Powder Tester (registered trademark) (manufactured by Hosokawa Micron Corporation). A pile of catalyst particles was placed on a spatula placed on a tray, and the spatula was then gently lifted. The angle (A) between the edge of the powder on the spatula and the spatula and the angle (B) after one impact with the attached weight were measured approximately 10 times, and the average value was taken as the spatula angle. D50 was measured using a laser diffraction / scattering particle size distribution analyzer LMS-2000e (manufactured by Seishin Enterprise Co., Ltd.).

[0036] [Table 1]

[0037] As shown in Table 1, examples were those in which the sum of the collapse angle and spatula angle was 85° or less and the spatula angle was 61.5° or less. Comparative examples were those in which at least one of the following conditions was not met: the sum of the collapse angle and spatula angle was 85° or less, or the spatula angle was 61.5° or less. Examples 1 and 5 or Comparative Example 1 were those in which iron oxide (hematite) was used as raw material particles; Example 2 or Comparative Example 2 was those in which iron oxide containing Al and Mg was used; Example 3 or Comparative Example 3 was those in which goethite particles were used; Example 4 or Comparative Example 4 was those in which an Fe-containing layered double hydroxide was used; and Example 6 was those in which spinel ferrite particles were used. As shown in Table 1, the collapse angle was 30° or less in all of the examples.

[0038] In Examples 1 and 5, the treatment condition b was carried out using hematite particles as the catalyst raw material. The resulting catalyst particles had a total collapse angle and spatula angle of 80.0°, 77.9°, and 80.0°, and the spatula angles were 51.4°, 52.6°, and 51.4°, respectively. The Fe content measured using a scanning X-ray fluorescence (XRF) analyzer (ZXT Primus II, manufactured by Rigaku Co., Ltd.) was 69.0 wt% in all cases.

[0039] In Example 3, goethite particles were used as the catalyst raw material under the treatment condition b. The resulting catalyst particles had a total collapse angle and spatula angle of 81.1°, a spatula angle of 57.2°, and an Fe content of 53.7 wt% as measured using a scanning X-ray fluorescence (XRF) analyzer (ZXT Primus II, manufactured by Rigaku Corporation).

[0040] In Example 4, Fe-containing layered double hydroxide was used as the catalyst raw material, and treatment conditions d (Example 4-1) and a (Example 4-2) were performed. The resulting catalyst particles had a total collapse angle and spatula angle of 72.9° and 82.5°, respectively, and spatula angles of 44.5° and 60.4°, and the Fe content measured using a scanning X-ray fluorescence (XRF) analyzer (ZXT Primus II, manufactured by Rigaku Co., Ltd.) was 18.0 wt% in all cases.

[0041] In Example 6, spinel ferrite particles were used as the catalyst raw material, and the treatment condition b was carried out. The resulting catalyst particles had a total collapse angle and spatula angle of 84.9°, a spatula angle of 58.5°, and an Fe content of 35.9 wt% as measured using a scanning X-ray fluorescence (XRF) analyzer (ZXT Primus II, manufactured by Rigaku Corporation).

[0042] The constituent phases of the catalyst particles of Examples 1 and 5 were confirmed by X-ray diffraction (XRD) (D8 ADVANCE, manufactured by BRUKER) and were confirmed to be a hematite phase. The constituent phases of the catalyst particles of Example 3 were confirmed by XRD and were confirmed to be a goethite phase. The constituent phases of the catalyst particles of Example 4 were confirmed by XRD and were confirmed to be a hydrotalcite phase. The constituent phases of the catalyst particles of Example 6 were confirmed by XRD and were confirmed to be a spinel-type ferrite phase.

[0043] Next, hydrogen and solid carbon were produced in a rotary kiln using the catalyst particles of each of the above examples and comparative examples. Specifically, a predetermined amount of catalyst was pre-loaded into a batch-type rotary kiln using a rotating reaction section (retort) with a circumference of 0.63 m or 0.48 m. The kiln was then heated over approximately one hour while rotating at 5.67 rpm in an inert atmosphere. At the predetermined temperature, the inert gas was switched to 13A city gas, and the reaction was carried out for three hours to produce hydrogen and solid carbon. Then, for each example and comparative example, the retort was tilted at an angle of 45° or more so that its outlet was facing downward. The amount of catalyst particles with solid carbon deposited on the surface discharged solely by the rotation of the rotary kiln and the amount of catalyst particles forcibly discharged by striking the furnace wall against the catalyst particles adhering to the furnace wall were measured, and the proportion of catalyst particles discharged solely by rotation was calculated. The conditions for each example and comparative example, such as the amount of catalyst supplied to the furnace, the set temperature, and the furnace circumference, along with the results of the measurements and calculations, are shown in Table 2 below.

[0044] [Table 2]

[0045] As shown in Table 2, when the catalyst particles of Examples 1 to 5 were used, 87% or more of the catalyst particles after catalyzing the methane pyrolysis reaction could be recovered by rotating the rotary kiln alone. On the other hand, when the catalyst particles of Comparative Examples 1 to 4 were used, 86% or less of the catalyst particles could be recovered by rotating the rotary kiln alone. From these results, it can be seen that by using the catalyst particles of each Example in which the sum of the collapse angle and spatula angle is 85° or less and the spatula angle is 61.5° or less, it is possible to prevent the catalyst particles from adhering to the furnace wall of the rotary kiln.

[0046] From the above, the catalyst particles according to the present invention have an appropriate fluidity, which can reduce adhesion of the catalyst particles to the furnace interior and improve contact with the raw material gas, and therefore the catalyst particles can efficiently promote the hydrogen production reaction, thereby improving the efficiency of hydrogen production and being useful.

Claims

1. Catalyst particles are heated while flowing in a furnace and used to convert a raw material gas introduced into the furnace, exhibits at least one of an iron oxide phase, an iron hydroxide phase, a spinel-type ferrite phase, and an Fe-containing layered double hydroxide phase in powder XRD; The sum of the collapse angle and the spatula angle is 85° or less, the collapse angle is 10° or more and 30° or less, and the spatula angle is 30° or more and 61.5° or less, The catalyst particles are characterized in that the furnace is a rotary kiln.

2. 2. The catalyst particle according to claim 1, wherein the iron oxide phase is hematite.

3. 2. The catalyst particle of claim 1, wherein the iron hydroxide phase is goethite.

4. 2. The catalyst particles according to claim 1, wherein the layered double hydroxide phase is hydrotalcite.

5. 2. The catalyst particles according to claim 1, wherein the particles have an iron content of 5% to 80%.

6. The raw material gas is C ａ H ２ａ＋ｂ 2. The catalyst particle according to claim 1, wherein a is a positive integer of 4 or less, and b is either -2, 0, or 2.

7. 2. The catalyst particles according to claim 1, wherein the conversion of the raw material gas is a reaction of thermally decomposing saturated hydrocarbons into hydrogen and solid carbon.

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