WO2025063273A1 - Dehydrogenation catalyst, method for producing dehydrogenation catalyst, and method for producing propylene - Google Patents

Abstract

The present invention pertains to a dehydrogenation catalyst for producing propylene by a dehydrogenation reaction of propane, said catalyst comprising MFI type zeolite, elemental platinum, and elemental M, wherein: the molar ratio (Si/Al) of silicon to elemental aluminum of the MFI type zeolite is 50 or more; the elemental M is at least one element selected from the group consisting of elemental germanium, elemental copper, elemental indium, elemental iron, elemental ruthenium, and elemental rhenium; and the elemental platinum and the elemental M are located in a channel of the MFI type zeolite.

Description

DEHYDROGENATION CATALYST, METHOD FOR PRODUCING DEHYDROGENATION CATALYST, AND METHOD FOR PRODUCING PROPYLENE

The present invention relates to a dehydrogenation catalyst, a method for producing a dehydrogenation catalyst, and a method for producing propylene.
This application claims priority based on Japanese Patent Application No. 2023-151834, filed on September 20, 2023, the contents of which are incorporated herein by reference.

Propylene is a key chemical used to manufacture a variety of chemicals, including resins, surfactants, dyes, and pharmaceuticals. In recent years, propylene supplies have been declining as steam cracker feedstock has shifted from naphtha derived from crude oil to ethane derived from shale gas.

Given this background, the production of propylene through the dehydrogenation of propane has attracted attention. Because the dehydrogenation of propane is an endothermic reaction, high temperatures of 600°C or higher are required for the reaction to proceed. Extensive research has been conducted on catalysts for the dehydrogenation of propane, and catalysts containing platinum metal are known. However, when the dehydrogenation of propane is carried out at temperatures above 600°C using conventional catalysts containing platinum metal, the activity decreases due to coke deposition and/or sintering.

Non-Patent Document 1 discloses a catalyst containing a platinum-based alloy. It is disclosed that the use of a catalyst containing a platinum-based alloy suppresses the decrease in activity in the dehydrogenation reaction of propane at temperatures above 600°C compared to conventional catalysts containing platinum metal.

J. Feng et al., Chin. J. Chem. Eng., 2014, 22, 1232.

However, the catalyst life of the propane dehydrogenation catalyst described in Non-Patent Document 1 is insufficient. The present invention has been made in consideration of the above circumstances, and aims to provide a dehydrogenation catalyst for producing propylene by the dehydrogenation reaction of propane that has a longer life than conventional catalysts, a method for producing the dehydrogenation catalyst, and a method for producing propylene using the dehydrogenation catalyst.

In order to solve the above problems, the present invention has the following aspects.
[1] A dehydrogenation catalyst for producing propylene by a dehydrogenation reaction of propane, comprising an MFI zeolite, a platinum element, and an M element, wherein the MFI zeolite has a molar ratio of silicon to aluminum element (Si/Al) of 50 or more, the M element is one or more elements selected from the group consisting of a germanium element, a copper element, an indium element, an iron element, a ruthenium element, and a rhenium element, and the platinum element and the M element are located within a channel of the MFI zeolite.
[2] The dehydrogenation catalyst according to [1], wherein the platinum element and the M element form an alloy cluster.
[3] The dehydrogenation catalyst according to [1] or [2], further comprising manganese oxide or tin oxide, the manganese oxide or the tin oxide being located within the channels of the MFI zeolite.
[4] The dehydrogenation catalyst according to any one of [1] to [3], wherein the MFI zeolite does not contain aluminum element.
[5] The dehydrogenation catalyst according to any one of [1] to [4], wherein the M element is a germanium element.
[6] A method for producing a dehydrogenation catalyst according to any one of [1] to [5], comprising: a hydrothermal synthesis step of hydrothermally synthesizing a mixed liquid containing a structure-directing agent, a compound containing a platinum element, the compound containing an M element, and a compound containing a silicon element; an oxidation-calcination step of oxidizing and calcining the solid obtained in the hydrothermal synthesis step in an oxidizing gas atmosphere to remove the structure-directing agent; and a reduction-calcination step of reducing and calcining the calcined body obtained in the oxidation-calcination step in a reducing gas atmosphere.
[7] A method for producing propylene, comprising contacting a feed gas containing propane with the dehydrogenation catalyst according to any one of [1] to [5].
[8] The method for producing propylene according to [7], wherein the reaction temperature is 550 to 650° C.

The present invention provides a dehydrogenation catalyst for producing propylene by the dehydrogenation reaction of propane, which has a longer life than conventional catalysts, a method for producing the dehydrogenation catalyst, and a method for producing propylene using the dehydrogenation catalyst.

FIG. 2 is a graph showing the results of a propane dehydrogenation reaction using the catalysts of Examples 1 and 2 and Comparative Examples 1 and 2. FIG. 1 is a graph showing the results of a propane dehydrogenation reaction using the catalysts of Example 4 and Comparative Examples 2 to 4. FIG. 1 is a graph showing the results of a propane dehydrogenation reaction using the catalysts of Example 5 and Comparative Examples 2 and 5. FIG. 1 is a graph showing the results of a propane dehydrogenation reaction using the catalysts of Examples 6 to 8 and Comparative Example 2. FIG. 1 is a graph showing the results of a propane dehydrogenation reaction using the catalysts of Comparative Examples 2 and 6 to 8. FIG. 1 is a graph showing the results of a propane dehydrogenation reaction using the catalysts of Comparative Examples 2, and 9 to 11. FIG. 1 is a graph showing the results of propane dehydrogenation reaction using the catalysts of Examples 1, 2, 9, and 10. FIG. 1 is a graph showing the results of propane dehydrogenation reaction using the catalysts of Examples 2, 3, 11, and 12.

The following describes in detail the embodiments of the present invention. However, the following description is merely an example of the embodiments of the present invention, and the present invention is not limited to these contents, and can be modified and implemented within the scope of the gist of the invention.

Dehydrogenation catalyst
The dehydrogenation catalyst of this embodiment is a dehydrogenation catalyst for producing propylene by the dehydrogenation reaction of propane. The dehydrogenation catalyst includes MFI zeolite, platinum element, and M element. The molar ratio of silicon to aluminum element (Si/Al) of the MFI zeolite is 50 or more. The M element is one or more elements selected from the group consisting of germanium element, copper element, indium element, iron element, ruthenium element, and rhenium element. The platinum element and the M element are located in the channel of the MFI zeolite. The platinum element and the M element are active components of the dehydrogenation reaction of propane.

<MFI type zeolite>
MFI zeolite is a zeolite having three-dimensional pores formed by the intersection of linear channels of 10-membered rings and sinusoidal channels of 10-membered rings. Examples of MFI zeolite include ZSM-5 containing aluminum element and silicalite not containing aluminum element.

The molar ratio of silicon to aluminum element (Si/Al) of MFI zeolite is 50 or more, preferably 100 or more, more preferably 300 or more, and silicalite that does not contain aluminum element is particularly preferred. When Si/Al is equal to or more than the lower limit, the number of acid sites in MFI zeolite is reduced, coke formation is suppressed, and as a result, catalytic activity is less likely to decrease.

MFI zeolite has 10-membered ring linear channels and 10-membered ring sinusoidal channels in the crystallite, which are micropores with a pore diameter of less than 2 nm. MFI zeolite preferably has substantially no mesopores with a pore diameter of 2 to 50 nm. MFI zeolite having substantially no mesopores means that the ratio of the pore volume of mesopores to the total pore volume is 10 volume% or less. The ratio of the pore volume of mesopores to the total pore volume is preferably 5 volume% or less, more preferably 0 volume%.
In this specification, the "total pore volume" and the "mesopore volume" can be determined from the pore distribution obtained by mercury intrusion porosimetry. Mercury intrusion porosimetry is a measurement method based on the law of capillary action. This law is expressed, for example, by the following formula. In the formula, D is the pore diameter, P is the pressure, γ is the surface tension, and θ is the contact angle. In other words, the pore diameter D is determined from the applied pressure P.
Formula: D=-(1/P)4γcosθ
The total pore volume is determined by integrating the obtained pore distribution, and the pore volume of mesopores is determined by integrating the pores in the 2 to 50 nm range in the obtained pore distribution.

The BET specific surface area of the MFI zeolite is preferably from 250 to 700 ^{m 2} /g, more preferably from 300 to 600 ^{m 2} /g, and even more preferably from 350 to 550 m ² /g.
In this specification, the "BET specific surface area" can be measured by a nitrogen adsorption method.

<Active ingredients>
The dehydrogenation catalyst contains a platinum element and an M element as active components.
The M element is one or more elements selected from the group consisting of germanium, copper, indium, iron, ruthenium, and rhenium, preferably one or more elements selected from the group consisting of germanium, indium, and ruthenium, and more preferably germanium.
The M element may be of one type or of two or more types.

The molar ratio of M element to platinum element (M/Pt) is preferably 0.3 to 7.0, more preferably 0.5 to 5.0, and even more preferably 1.0 to 4.5. When M/Pt is equal to or greater than the lower limit of the range, the catalytic activity, propylene selectivity, and catalyst durability are improved. When M/Pt is equal to or less than the upper limit of the range, the propylene selectivity and catalyst durability are improved.

The platinum element and the M element are located in the channels of the MFI zeolite. The platinum element and the M element are preferably located in the sinusoidal channel of the 10-membered ring. The location of the platinum element and the M element in the sinusoidal channel of the 10-membered ring can be confirmed by combining high-angle annular dark-field scanning transmission microscopy (HAADF-STEM) observation combined with energy dispersive X-ray (EDX) and integrated differential phase contrast (iDPC) STEM observation. Since iDPC has high sensitivity to light elements (silicon, oxygen, etc.), it is possible to observe the zeolite framework. On the other hand, since HAADF-STEM has high sensitivity to heavy elements (platinum, etc.), it is possible to observe the platinum element and the M element. In other words, by comparing the iDPC-STEM image with the HAADF-STEM image, the positions of the platinum element and the M element in the MFI zeolite can be confirmed. At least a portion of the platinum element (M element) may be located within the channel of the MFI zeolite. The amount of platinum element (M element) located within the channel of the MFI zeolite is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 100 mol% relative to the total amount of platinum element (M element).

The platinum and M elements are located within the channels of the MFI zeolite, which suppresses sintering of platinum and M.

The platinum element and the M element may each be in the form of a single metal, an oxide, or an alloy of platinum and the M element. In particular, the platinum element and the M element preferably form an alloy cluster. In this specification, "cluster" means a particle having a particle diameter of 1.2 nm or less. The average particle diameter of the alloy cluster is preferably 1.0 nm or less, more preferably 0.9 nm or less, and even more preferably 0.8 nm or less. The particle diameter of the alloy cluster can be measured by HAADF-STEM observation combined with an energy dispersive X-ray (EDX) method. The longest diameter of 100 or more randomly selected alloy clusters can be measured, and the average of these can be used as the average particle diameter. The number of alloy clusters in the sample may be 100.

The platinum and M elements form alloy clusters, which increases the amount of platinum present on the surface of the alloy clusters compared to larger particles, and platinum is utilized more effectively. It is also believed that the catalytic activity is improved due to the geometric and electronic effects unique to cluster alloys.

<Manganese oxide, tin oxide>
The dehydrogenation catalyst preferably contains manganese oxide or tin oxide. It may contain both manganese oxide and tin oxide. Among them, it is preferable to contain manganese oxide. The manganese oxide or tin oxide is preferably located in the channel of MFI zeolite. It is more preferable that the manganese oxide or tin oxide is located in the sinusoidal channel of a 10-membered ring. It can be confirmed that the manganese oxide or tin oxide is located in the sinusoidal channel of a 10-membered ring in the same manner as in the case of the platinum element and the M element described above. It is sufficient that at least a part of the manganese oxide (tin oxide) is located in the channel of the MFI zeolite. The amount of manganese oxide (tin oxide) located in the channel of the MFI zeolite is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 100 mol% with respect to the total amount of manganese oxide (tin oxide).

When propylene is produced by the dehydrogenation reaction of propane, hydrogen is a by-product. It is believed that this hydrogen is adsorbed onto the surface of the metal (alloy) of platinum element and/or M element, which is the active component, and the active component is poisoned. The inventors of this application have discovered for the first time that by including manganese oxide or tin oxide in the dehydrogenation catalyst and positioning the manganese oxide or tin oxide in the vicinity of the active component, the manganese oxide or tin oxide adsorbs hydride during the production of propylene and then releases it as hydrogen (i.e., hydrogen is produced not by the active component but by the manganese oxide or tin oxide), thereby suppressing the poisoning of the active component. Furthermore, by including manganese oxide or tin oxide, coking of the dehydrogenation catalyst is also suppressed.

<Composition>
The total content of platinum and M element relative to the total mass of the dehydrogenation catalyst is preferably 0.1 to 1.6 mass%, more preferably 0.3 to 1.4 mass%, and even more preferably 0.4 to 1.2 mass%. When the total content of platinum and M element is equal to or greater than the lower limit of the above range, activity per catalyst mass is improved. When the total content of platinum and M element is equal to or less than the upper limit of the above range, alloy clusters can be appropriately formed.

The content of platinum element relative to the total mass of the dehydrogenation catalyst is preferably 0.05 to 1.0 mass%, more preferably 0.1 to 0.8 mass%, and even more preferably 0.2 to 0.6 mass%. When the content of platinum element is equal to or greater than the lower limit of the above range, the activity per catalyst mass is improved. When the content of platinum element is equal to or less than the upper limit of the above range, alloy clusters can be properly formed.

The content of the M element relative to the total mass of the dehydrogenation catalyst is preferably 0.05 to 0.6 mass%, more preferably 0.1 to 0.5 mass%, and even more preferably 0.2 to 0.4 mass%. When the content of the M element is equal to or greater than the lower limit of the above range, the catalytic activity, propylene selectivity, and catalyst durability are improved. When the content of the M element is equal to or less than the upper limit of the above range, the propylene selectivity and catalyst durability are improved.

The content of MFI zeolite relative to the total mass of the dehydrogenation catalyst is preferably 96 to 99.5 mass%, more preferably 97 to 99 mass%, and even more preferably 97.5 to 98.8 mass%. When the content of MFI zeolite is equal to or greater than the lower limit of the above range, the catalytic activity per Pt mass is improved. When the content of MFI zeolite is equal to or less than the upper limit of the above range, the catalytic activity is improved.

When the dehydrogenation catalyst contains manganese oxide or tin oxide, the total content of elemental manganese and tin is preferably 0.05 to 2.0 mass%, more preferably 0.1 to 1.5 mass%, and even more preferably 0.2 to 1.0 mass%. When the total content of elemental manganese and tin is equal to or greater than the lower limit of the above range, the catalytic activity, propylene selectivity, and catalyst durability are improved. When the total content of elemental manganese and tin is equal to or less than the upper limit of the above range, the catalytic activity, propylene selectivity, and catalyst durability are improved.

When the dehydrogenation catalyst contains manganese oxide or tin oxide, the molar ratio of the sum of elemental manganese and elemental tin to the sum of elemental platinum and element M ((Mn+Sn)/(Pt+M)) is preferably 0.1 to 1.0, more preferably 0.2 to 0.9, and even more preferably 0.3 to 0.7.

When the dehydrogenation catalyst contains manganese oxide or tin oxide, the molar ratio of the sum of elemental manganese and elemental tin to elemental platinum ((Mn+Sn)/Pt) is preferably 0.2 to 3, more preferably 0.4 to 2, and even more preferably 0.6 to 1.5. When (Mn+Sn)/Pt is equal to or greater than the lower limit of the range, the catalytic activity, propylene selectivity, and catalyst durability are improved. When (Mn+Sn)/Pt is equal to or less than the upper limit of the range, the catalytic activity and propylene selectivity are improved.

When the dehydrogenation catalyst contains manganese oxide or tin oxide, the molar ratio of the sum of the manganese element and the tin element to the M element ((Mn+Sn)/M) is preferably 0.1 to 2, more preferably 0.3 to 1.6, and even more preferably 0.5 to 1.5.

The dehydrogenation catalyst may contain other components in addition to MFI zeolite, platinum element, M element, manganese oxide, and tin oxide. Examples of other components include metal elements other than platinum element and M element, and alkali metals derived from the manufacturing process of MFI zeolite. Preferred alkali metals are K and Na. When the dehydrogenation catalyst contains other components, the content of the other components relative to the total mass of the dehydrogenation catalyst is preferably 0.3 to 1.5 mass%, more preferably 0.4 to 1.1 mass%, and even more preferably 0.5 to 0.8 mass%. When the dehydrogenation catalyst contains an alkali metal, alloy clusters of platinum element and M element are more likely to be generated.

In this specification, the content of "platinum element, M element, manganese element, tin element, etc." can be measured by inductively coupled plasma atomic emission spectrometry (ICP). For example, after dissolving the dehydrogenation catalyst in acid, the amount of each element can be measured using an inductively coupled plasma atomic emission spectrometer.

＜Physical properties＞

The BET specific surface area of the dehydrogenation catalyst is preferably from 250 to 700 ^{m 2} /g, more preferably from 300 to 600 ^{m 2} /g, and even more preferably from 350 to 550 m ² /g.

The dehydrogenation catalyst preferably has substantially no mesopores with a pore diameter of 2 to 50 nm. "The dehydrogenation catalyst has substantially no mesopores" means that the ratio of the mesopore volume to the total pore volume is 10% by volume or less. The ratio of the mesopore volume to the total pore volume is more preferably 5% by volume or less, and even more preferably 0% by volume.

<Method for producing dehydrogenation catalyst>
The method for producing a dehydrogenation catalyst of this embodiment includes a hydrothermal synthesis step of hydrothermally synthesizing a mixed solution containing a structure-directing agent, a compound containing a platinum element, a compound containing an M element, a compound containing a silicon element, and, if necessary, a compound containing an aluminum element, an oxidation-calcination step of oxidizing and calcining the solid obtained in the hydrothermal synthesis step in an oxidation gas atmosphere to remove the structure-directing agent, and a reduction-calcination step of reducing and calcining the calcined body obtained in the oxidation-calcination step in a reduction gas atmosphere. When the dehydrogenation catalyst contains manganese oxide or tin oxide, the mixed solution may contain a compound containing manganese element or a compound containing tin element. The mixed solution can be produced by a mixed solution preparation step.

<Mixture preparation step>
As the structure directing agent used in the mixed solution preparation step, tetrapropylammonium hydroxide (hereinafter also referred to as "TPAOH") or tetrapropylammonium bromide, which can generate tetrapropylammonium ions, can be used.

The compounds containing platinum, M, manganese and tin are not particularly limited, but examples include inorganic salts such as chlorides, sulfides, nitrates, carbonates, fluorides, ammonium salts and ammonium fluorides; organic salts such as oxalates, acetylacetonates, dimethylglyoximes and ethylenediamine acetates; chelate compounds; carbonyl compounds; cyclopentadienyl compounds; ammine complexes; alkoxide compounds; alkyl compounds; etc.

Examples of compounds containing silicon element include water glass, colloidal silica, and alkoxide compounds, with alkoxide compounds being preferred, and tetraethoxysilane (hereinafter also referred to as "TEOS") being more preferred.
Examples of compounds containing aluminum include aluminates and alkoxide compounds.

In order to dissolve the silicon-containing compound and the aluminum-containing compound, the mixed liquid preferably contains an acid or a base, and more preferably contains a base. If the mixed liquid contains an acid or a base, and an alkoxide compound is used as the silicon-containing compound or the aluminum-containing compound, the alkoxide compound will hydrolyze and dissolve in the mixed liquid. There are no particular limitations on the base, but examples include hydroxides of alkali metals, and sodium hydroxide and potassium hydroxide are preferred.

Examples of the solvent for the mixture include water, ethanol, and acetone, with water being preferred.
In addition to the above compounds, it is preferable to add a dispersant. As the dispersant, a compound having a nitrogen atom is preferable, and ethylenediamine is more preferable.

The order of addition of the structure directing agent, the compound containing platinum, the compound containing M, the compound containing silicon (and optionally the compound containing aluminum), the compound containing manganese, and the compound containing tin is not particularly limited.

<Hydrothermal synthesis process>
The temperature of the hydrothermal synthesis is preferably 150 to 200° C., more preferably 160 to 190° C., and even more preferably 170 to 180° C. The time of the hydrothermal synthesis is preferably 80 to 120 hours, more preferably 70 to 110 hours, and even more preferably 80 to 105 hours.

It is preferable to separate the solid obtained in the hydrothermal synthesis process and wash it. Examples of washing liquids include water, ethanol, and acetone. After washing, drying may be performed.

<Oxidation firing process>
The oxidation gas in the oxidation firing step includes oxygen, air, etc., and a gas diluted with an inert gas may be used. The temperature of the oxidation firing step is preferably 500 to 700°C, more preferably 520 to 660°C, and more preferably 540 to 620°C.
The time for the oxidation baking may be from 5 to 20 hours, from 7 to 15 hours, or from 8 to 12 hours.
The oxidation baking may be carried out only once, or may be carried out two or more times.

The structure-directing agent can be removed by the oxidation and baking process. Furthermore, if the mixed liquid contains a compound containing manganese or a compound containing tin, manganese oxide or tin oxide will be produced by the oxidation and baking process.

<Reduction firing process>
The reducing gas in the reduction firing step includes hydrogen, carbon monoxide, etc., and a gas diluted with an inert gas may be used. The temperature of the reduction firing is preferably 500 to 720°C, more preferably 550 to 710°C, and more preferably 600 to 700°C.
The time for the reduction firing may be from 0.2 to 10 hours, from 0.5 to 7 hours, or from 1 to 5 hours.
It has been confirmed that when a compound containing manganese or a compound containing tin is used, manganese and tin do not form an alloy with platinum even when reduction firing is performed. Platinum and manganese or tin are located in the channels of MFI zeolite, but platinum-manganese alloys and platinum-tin alloys are considered not to be formed in the pores of MFI zeolite due to their large size. It is considered that the oxidation numbers of manganese oxide and tin oxide are reduced by reduction firing. For example, when MnO ₂ is reduced and fired, a part of MnO ₂ is reduced to Mn ₂ O ₃ , Mn ₃ O ₄ , and MnO. The reduction firing may be performed only once, or may be performed two or more times.

The reduction calcination step is preferably carried out by passing a reducing gas through the calcined body packed during the reaction. The gas hourly space velocity of the reducing gas with respect to the calcined body is more preferably 2500 to 75000 hr ^-1 .

<Propylene production method>
The method for producing propylene according to the present embodiment is a method for producing propylene by a dehydrogenation reaction of propane, which comprises contacting a feed gas containing propane with the dehydrogenation catalyst of the present invention.

The propylene production method can be carried out, for example, by filling a reactor with the above-mentioned dehydrogenation catalyst and passing a raw material gas containing propane through it. The reaction method is not particularly limited as long as the effects of the present invention can be obtained, but examples include a fixed bed type, a fluidized bed type, and a moving bed type, with the fixed bed type being preferred.

The propylene production method may be a single-stage propylene production method in which the above-mentioned dehydrogenation catalyst is packed into a single reactor, or a multi-stage continuous propylene production method in which the dehydrogenation catalyst is packed into multiple reactors.

The propane content relative to 100% by volume of the raw material gas is preferably 20-100% by volume, and more preferably 50-100% by volume. Examples of gases other than propane in the raw material gas include inert gases such as helium and nitrogen.

The raw material gas may contain hydrogen. When the raw material gas contains hydrogen, the generation of coke is suppressed. The hydrogen content relative to 100 volume percent of the raw material gas is preferably 10 to 40 volume percent, and more preferably 10 to 20 volume percent. When the hydrogen content is equal to or greater than the lower limit of the range, the catalyst life is improved. When the hydrogen content is equal to or less than the upper limit of the range, the catalytic activity is improved. The dehydrogenation catalyst of this embodiment is less susceptible to deterioration in catalytic activity, so the catalyst life can be extended even if the raw material gas does not contain hydrogen.

The reaction temperature is preferably 550 to 650°C, more preferably 580 to 640°C, and even more preferably 600 to 630°C. When the reaction temperature is equal to or higher than the lower limit of the range, the equilibrium conversion rate and reaction rate are improved. When the reaction temperature is equal to or lower than the upper limit of the range, sintering of the active components is suppressed, and a decrease in catalytic activity is suppressed.

The reaction pressure is preferably 0.1 to 0.3 MPa, more preferably 0.1 to 0.25 MPa, and even more preferably 0.1 to 0.2 MPa. The reaction pressure may be normal pressure.

The weight hourly space velocity (WHSV) of propane in the feed gas relative to the dehydrogenation catalyst is more preferably 1 to 10 hr ^-1 , and even more preferably 2 to 4 hr ^-1 . When the WHSV is equal to or greater than the lower limit of the above range, productivity is improved.

Examples of propane in the raw gas used in the propylene production method of this embodiment include propane derived from shale gas, propane derived from naphtha, and propane derived from biomass.

By using the dehydrogenation catalyst of the present invention, it becomes possible to produce propylene over a longer period of time.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

<Characterization and analysis of dehydrogenation catalysts>
The dehydrogenation catalyst was characterized and analyzed by high-angle annular dark-field scanning transmission microscope, composition analysis, and measurement of the carbon content of the dehydrogenation catalyst after the reaction.

(High angle scattering annular dark field scanning transmission microscope observation)
The particle size of the active component (alloy cluster) of each dehydrogenation catalyst was measured by a high-angle scattering annular dark-field scanning transmission microscope (FEI Titan G-2) equipped with an energy dispersive X-ray (EDX) analyzer at an acceleration voltage of 300 kV. In addition, integrated differential phase contrast (iDPC) was performed using the high-angle scattering annular dark-field scanning transmission microscope to confirm the zeolite framework. Specifically, the dehydrogenation catalyst of each example was crushed, ultrasonicated in ethanol, and then dispersed on a Mo grid supported by a carbon film for observation. The particle size distribution was measured by observing the longest diameter of 100 or more particles (alloy clusters, which are active components) randomly selected from 10 images, and the average of these was taken as the average particle size.

(Composition Analysis)
The composition of the dehydrogenation catalyst in each example was analyzed by inductively coupled plasma emission spectrometry (ICP). The dehydrogenation catalyst was dissolved in a mixed solution of hydrofluoric acid, nitric acid, and hydrochloric acid, and the amount of each element was measured using an inductively coupled plasma emission spectrometry device.

<Measurement of carbon amount in dehydrogenation catalyst after reaction>
The carbon amount of the dehydrogenation catalyst after the reaction of each example was measured by BELCAT II manufactured by MicrotracBEL. Helium was passed through 50 mg of the dehydrogenation catalyst after the reaction for 19.5 hours at 20 NmL/min, pre-treated at 150°C for 1 hour, and then cooled to 100°C. Next, a mixed gas of 2 vol% oxygen and 98 vol% helium was passed through at 50 NmL/min, and the mixture was heated at a constant heating rate from 100 to 700°C. The amount of carbon dioxide in the outlet gas was quantified by an online mass meter. In Table 1, [g] means the amount of carbon per 1 g of catalyst.

<Dehydrogenation of Propane>
The dehydrogenation catalyst of each example was packed into a cylindrical fixed-bed reactor tube made of quartz having a diameter of 4 mm to form a catalyst layer. Hydrogen was then passed through the catalyst layer to carry out pretreatment. Thereafter, a raw material gas containing propane was passed through the catalyst layer to carry out the dehydrogenation reaction of propane.

The gas discharged from the reactor was analyzed using an online thermal conductivity detection gas chromatograph (Shimadzu Corporation, product name "GC-8A"). Propylene, propane, ethylene, ethane, and methane were detected in the reactor outlet gas.

The propane conversion rate was calculated using the following formula 1.

　前記式１中、［Ｃ_３Ｈ_８］_{ｉｎｌｅｔ}は反応器に供給したプロパンの流量（ｍｏｌ／ｍｉｎ）を示し、［Ｃ_３Ｈ_８］_{ｏｕｔｌｅｔ}は反応器から排出されたプロパンの流量（ｍｏｌ／ｍｉｎ）を示す。

In the above formula 1, [C ₃ H ₈ ] _inlet represents the flow rate (mol/min) of propane supplied to the reactor, and [C ₃ H ₈ ] _outlet represents the flow rate (mol/min) of propane discharged from the reactor.

The propylene selectivity was calculated using the following formula 2.

　前記式２中、［Ｃ_３Ｈ_６］は反応器から排出されたプロピレンの流量（ｍｏｌ／ｍｉｎ）を示し、［Ｃ_２Ｈ_６］は反応器から排出されたエタンの流量（ｍｏｌ／ｍｉｎ）を示し、［Ｃ_２Ｈ_４］は反応器から排出されたエチレンの流量（ｍｏｌ／ｍｉｎ）を示し、［ＣＨ_４］は反応器から排出されたメタンの流量（ｍｏｌ／ｍｉｎ）を示す。

In the above formula 2, [C ₃ H ₆ ] represents the flow rate (mol/min) of propylene discharged from the reactor, [C ₂ H ₆ ] represents the flow rate (mol/min) of ethane discharged from the reactor, [C ₂ H ₄ ] represents the flow rate (mol/min) of ethylene discharged from the reactor, and [CH ₄ ] represents the flow rate (mol/min) of methane discharged from the reactor.

The propylene yield was calculated by: flow rate of propylene discharged from the reactor (mol/min) / flow rate of propane supplied to the reactor (mol/min) x 100.

The average catalyst life of the dehydrogenation catalyst was calculated using a first-order deactivation model. Specifically, the average catalyst life of the dehydrogenation catalyst was calculated using the following formulas 3 and 4.

　前記式３中、Ｋ_ｄは失活速度定数（ｈ^－１）を示し、ｔは反応時間（ｈ）を示し、ｃｏｎｖ_{ｓｔａｒｔ}は反応開始時のプロパンの転化率（％）を示し、ｃｏｎｖ_ｅｎｄは反応時間ｔ（ｈ）におけるプロパンの転化率（％）を示す。なお、反応開始時のプロパンの転化率とは、図１～８における最初のプロットのプロパン転化率である。

In the above formula 3, K _d represents the deactivation rate constant (h ⁻¹ ), t represents the reaction time (h), conv _start represents the propane conversion (%) at the start of the reaction, and conv _end represents the propane conversion (%) at the reaction time t (h). The propane conversion at the start of the reaction is the propane conversion of the first plot in Figures 1 to 8.

　前記式４中、１／ｋ_ｄは平均触媒寿命（ｈ）を示す。

In the above formula 4, 1/ _kd represents the average catalyst life (h).

[Example 1]
8.12 g of TPAOH (20-25% by mass, K-free) was dropped into an aqueous solution containing 35 mg of potassium hydroxide (86% by mass) and 5 g of ion-exchanged water, and after stirring, 4.2474 g of TEOS was further dropped. After stirring the obtained solution at room temperature for 24 hours, an aqueous solution containing 30.5 mg of (NH ₄ ) ₂ GeF ₆ and 0.2 g of ion-exchanged water was dropped, and stirring was continued for another hour. Then, a mixed aqueous solution containing 15.7 mg of H ₂ PtCl _{6.6H 2} O, 26.2 mg of Mn(NO ₃ ) _{2.6H 2} O, and 0.8 g of ion-exchanged water was dropped and stirred for 6 hours, and 150 μL of ethylenediamine was added and stirred for another hour.
The obtained solution was transferred to a PTFE container, sealed in an autoclave, and hydrothermal synthesis was performed at 175 ° C. for 96 hours (heating rate: 1 ° C. / min). After completion of hydrothermal synthesis, the sample was cooled to room temperature, recovered using ion-exchanged water, and centrifuged. The supernatant was removed, and the obtained residue was washed by suction filtration five times each with water and acetone, and then dried overnight at 90 ° C. Then, it was baked at 560 ° C. for 8 hours (heating rate: 2 ° C. / min) in an air atmosphere, and then cooled to room temperature. It was further baked at 600 ° C. for 2 hours (heating rate: 5 ° C. / min) in an air atmosphere to obtain catalyst A1 in which platinum-germanium alloy clusters and manganese oxide were supported in the pores of silicalite. Table 1 shows the Pt content (mass%) relative to the total mass of the catalyst converted into the amount of charge, and the molar ratio of other metals (M element, etc.) per 1 mol of Pt (hereinafter, the same is shown for Examples 2, 3, and Comparative Examples 1 to 3). The Pt content relative to the total mass of the catalyst measured by ICP was 0.43% by mass, and the molar ratios of Ge and Mn per mole of Pt were 1.8 and 3.3, respectively. Table 1 also shows the average particle size of the metal clusters. It was confirmed that the Pt and Ge metal clusters and manganese oxide were located within the sinusoidal channels of the 10-membered ring.

[Example 2]
Catalyst A2 in which platinum-germanium alloy clusters were supported in the pores of silicalite was obtained in the same manner as in Example 1, except that Mn(NO ₃ ) _{2.6H 2} O was not used. The Pt content relative to the total mass of the catalyst measured by ICP was 0.46 mass%, and the molar ratio of Ge per 1 mol of Pt was 1.6. It was confirmed that the Pt and Ge metal clusters were located in the sinusoidal channels of the 10-membered ring.

[Example 3]
Catalyst _A3 , in _which platinum-germanium alloy clusters and tin oxide were supported in the pores of silicalite, was obtained in the same manner as in Example 1, except that 50 mg of SnCl _{5.5H 2} O was used instead of Mn(NO ₃ ) 2.6H 2 O. It was confirmed that the Pt and Ge metal clusters and tin oxide were located in the sinusoidal channels of 10-membered rings.

[Comparative Example 1]
8.12 g of TPAOH was added dropwise to an aqueous solution containing 35 mg of KOH and 5 g of ion-exchanged water, and after stirring, 4.2474 g of TEOS was further added dropwise. The resulting solution was stirred at room temperature for 24 hours, and then a mixed aqueous solution containing 16.0 mg of H ₂ PtCl _{6.6H 2} O, 39.3 mg of Mn(NO ₃ ) _{2.6H 2} O, and 1.0 g of ion-exchanged water was added dropwise and stirred for 6 hours. After that, 150 μL of ethylenediamine was added and stirred for another hour.
The obtained solution was transferred to a PTFE container, sealed in an autoclave, and hydrothermal synthesis was performed at 175 ° C. for 96 hours (heating rate: 1 ° C. / min). After completion of hydrothermal synthesis, the sample was cooled to room temperature, recovered using ion-exchanged water, and centrifuged. The supernatant was removed, and the obtained residue was washed by suction filtration five times with water and acetone, respectively, and then dried overnight at 90 ° C. Thereafter, it was baked at 560 ° C. for 8 hours (heating rate: 2 ° C. / min) in an air atmosphere, and then cooled to room temperature. It was further baked at 600 ° C. for 2 hours (heating rate: 5 ° C. / min) in an air atmosphere to obtain catalyst B1 in which platinum metal and manganese oxide were supported in the pores of silicalite. The content of Pt relative to the total mass of the catalyst measured by ICP was 0.40 mass%. It was confirmed that Pt metal and manganese oxide were located in the sinusoidal channel of the 10-membered ring.

[Comparative Example 2]
Catalyst B2, in which platinum metal was supported in the pores of silicalite, was obtained in the same manner as in Comparative Example 1, except that Mn(NO ₃ ) _{2.6H 2} O was not used. The Pt content relative to the total mass of the catalyst measured by ICP was 0.43 mass%. It was confirmed that the Pt metal was located in the sinusoidal channels of the 10-membered ring.

[Example 4]
Catalyst A4, in which platinum-copper alloy clusters were supported in the pores of silicalite, was obtained by the same method as in Example 2, except that 19.3 mg of CuCl ₂ was used instead of (NH ₄ ) ₂ GeF _6. Table 2 shows the Pt content (mass %) relative to the total mass of the catalyst calculated as the charged amount, and the molar ratio of other metals (M element, etc.) per mol of Pt (hereinafter, the same is shown for Examples 5 to 12 and Comparative Examples 3 to 11). Note that M1 in Table 2 means a metal element other than Pt, M element, Mn, and Sn.

[Comparative Example 3]
A catalyst B3 in which platinum and cobalt were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 32.7 mg of CoCl _{2.6H 2} O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 4]
A catalyst B4 in which platinum and nickel were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 33.2 mg of NiCl ₂ .6H ₂ O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Example 5]
A catalyst A5 in which platinum and indium were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 62.9 mg of In(NO ₃ ) _{3.nH 2} O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 5]
A catalyst B5 in which platinum and lead were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 45.3 mg of Pb(NO ₃ ) ₂ was used instead of ₆ (NH ₄ ) ₂ GeF.

[Example 6]
A catalyst A6 in which platinum and iron were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 37.2 mg of FeCl _{3.6H 2} O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Example 7]
A catalyst A7 in which platinum and ruthenium were supported in the pores of silicalite was obtained in the same manner as in Example ₂ , except that 33.7 mg _{of RuCl3.nH2O} was used instead of ( _NH4 ) _2GeF6 .

[Example 8]
A catalyst A8 in which platinum and rhenium were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 36.9 mg of (NH ₄ )ReO ₄ was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 6]
A catalyst B6 in which platinum and zinc were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 41.1 mg of Zn(NO ₃ ) _{2.6H 2} O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 7]
A catalyst B7 in which platinum and antimony were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 24.8 mg of SbF ₃ was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 8]
A catalyst B8 in which platinum and bismuth were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 44.2 mg of BiCl ₃ was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 9]
A catalyst B9 in which platinum and lanthanum were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 59.0 mg of La(NO ₃ ) _{3.6H 2} O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 10]
A catalyst B10 in which platinum and cerium were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 60.3 mg of Ce(NO ₃ ) _{3.6H 2} O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Comparative Example 11]
A catalyst B11 in which platinum and tellurium were supported in the pores of silicalite was obtained in the same manner as in Example 2, except that 31.7 mg of H ₂ TeO ₄ .2H ₂ O was used instead of (NH ₄ ) ₂ GeF ₆ .

[Example 9]
Catalyst A9 in which platinum, germanium, and iron were supported in the pores of silicalite was obtained by the same method as in Example 2, except that 12.4 mg of FeCl _{2.6H 2} O was further added to the mixed solution containing H ₂ PtCl _{6.6H 2} O. The molar ratio of other metals (M element, etc.) per 1 mol of Pt calculated as the charged amount was 4.5 mol of Ge and 1.5 mol of Fe.

[Example 10]
Catalyst A10 in _which platinum, germanium, and copper were supported in the pores of silicalite was obtained by the same method as in Example 2, except that 6.4 _mg of _CuCl2 was further added to the mixed solution containing _H2PtCl6.6H2O . The molar ratio of other metals (M element, etc.) per 1 mol of Pt calculated as the amount of charge was 4.5 mol of Ge and 1.5 mol of Cu.

[Example 11]
Catalyst _A11 in _which platinum, germanium, and gallium were supported in the pores of silicalite was obtained in the same manner as in _Example 2, except that 18.4 mg of Ga(NO ₃ ) _{3.nH 2} O was further added to the mixed liquid containing H 2 PtCl 6.6H 2 O.

[Example 12]
Catalyst A12 in _which platinum, germanium, and gallium were supported in the pores of silicalite was obtained by the same method as in Example 2, except that 11.2 _{mg of RuCl3.nH2O} was further added to the mixed solution containing _H2PtCl6.6H2O . The molar ratio of other metals (M element, etc.) per 1 mol of Pt calculated as the charged amount was 4.5 mol of Ge and 1.5 mol of Ru.

Using catalysts A1, A2, B1 and B2, a dehydrogenation reaction of propane was carried out under the following reaction conditions.
Catalyst loading amount: 30 mg (150 mg for catalysts B1 and B2)
Pretreatment conditions: Hydrogen was circulated through the catalyst layer at 10 mL/min, and pretreatment was carried out at 700° C. for 5 hours.
Reaction conditions: A mixed gas of propane:helium with a volume ratio of 1:2 was passed through the catalyst layer at 7.5 mL/min, and the reaction was carried out at 600° C. or 630° C. The reaction pressure was 0.1 MPa (normal pressure).

Figure 1 shows the change over time in the propane conversion rate and the propylene selectivity at a reaction temperature of 630°C for catalysts A1, A2, B1, and B2. The catalysts of Examples 1 and 2, which contain platinum element, M element, and MFI-type zeolite, had higher propane conversion rate and propylene selectivity at all reaction times compared to the catalysts of Comparative Examples 1 and 2, which do not contain platinum element, M element, or MFI-type. Furthermore, the catalyst of Example 1, which further contains manganese oxide, showed less decrease over time in the propane conversion rate compared to the catalyst of Example 2.

Table 1 shows the 1/ _kd of catalysts A1, A2, B1, and B2 at reaction temperatures of 600°C and/or 630°C. It was found that the catalysts of Examples 1 and 2, which contain platinum element, M element, and MFI type zeolite, have a longer average catalyst life than the catalysts of Comparative Examples 1 and 2, which do not contain platinum element, M element, or MFI type. Table 1 also shows the carbon amounts of catalysts A1, A2, B1, and B2 after 19.5 hours of reaction at a reaction temperature of 600°C. It was found that coking was suppressed by the inclusion of manganese oxide.

Using catalysts A4 to A8, catalysts B2, and B3 to B11, a dehydrogenation reaction of propane was carried out under the following reaction conditions.
Catalyst loading amount: 50 mg
Pretreatment conditions: Hydrogen was circulated through the catalyst layer at 10 mL/min, and pretreatment was carried out at 700° C. for 5 hours.
Reaction conditions: A mixed gas of propane:helium with a volume ratio of 1:2 was passed through the catalyst layer at 7.5 mL/min, and the reaction was carried out at 600° C. The reaction pressure was 0.1 MPa (normal pressure).

The change over time in the propane conversion rate and the change over time in the propylene selectivity for catalyst A4 and catalysts B2 to B4 are shown in Figure 2. The catalyst of Example 4, which contains platinum element, M element, and MFI-type zeolite, had a higher propylene yield after 5 hours of reaction compared to the catalysts of Comparative Examples 2 to 4, which contain platinum element and MFI-type zeolite but do not contain M element.

The change over time in the propane conversion rate and the change over time in the propylene selectivity for catalysts A5, B2, and B5 are shown in Figure 3. The catalyst of Example 5, which contains platinum element, M element, and MFI-type zeolite, had a higher propylene yield after 15 hours of reaction compared to the catalysts of Comparative Examples 2 and 5, which contain platinum element and MFI-type zeolite but do not contain M element.

The changes over time in the propane conversion rate and the propylene selectivity for catalysts A6 to A8 and catalyst B2 are shown in Figure 4. The catalysts of Examples 6 to 8, which contain platinum element, M element, and MFI-type zeolite, had a higher propylene yield after 5 hours of reaction compared to the catalyst of Comparative Example 2, which contains platinum element and MFI-type zeolite but does not contain M element.

The change over time in the propane conversion rate and the change over time in the propylene selectivity for catalysts B2, B6 to B8 are shown in Figure 5. The catalysts of Comparative Examples 6 to 8, which contain platinum element and MFI zeolite and metal elements other than the M element, had a propylene yield at or below the same level after 5 hours of reaction compared to the catalyst of Comparative Example 2, which contains only platinum element and MFI zeolite.

The change over time in the propane conversion rate and the change over time in the propylene selectivity for catalysts B2, B9 to B11 are shown in Figure 6. The catalysts of Comparative Examples 9 to 11, which contain platinum element and MFI zeolite and metal elements other than the M element, had a lower propylene yield after 5 hours of reaction compared to the catalyst of Comparative Example 2, which contains only platinum element and MFI zeolite.

Using the catalysts A1, A2, A3, and A9 to A12, a dehydrogenation reaction of propane was carried out under the following reaction conditions.
Catalyst loading amount: 30 mg
Pretreatment conditions: Hydrogen was circulated through the catalyst layer at 10 mL/min, and pretreatment was carried out at 700° C. for 5 hours.
Reaction conditions: A mixed gas of propane:helium with a volume ratio of 1:2 was passed through the catalyst layer at 7.5 mL/min, and the reaction was carried out at 630°C.

The changes in propane conversion rate and propylene selectivity over time for catalysts A1, A2, A9, and A10 are shown in Figure 7. The catalysts of Examples 1, 2, 9, and 10, which contain platinum element, M element, and MFI-type zeolite, suppressed the decrease in propane conversion rate over time. In addition, the propylene selectivity was consistently at a high level.

The changes in propane conversion rate and propylene selectivity over time for catalysts A2, A3, A11, and A12 are shown in Figure 8. The catalysts of Examples 2, 3, 11, and 12, which contain platinum element, M element, and MFI-type zeolite, suppressed the decrease in propane conversion rate over time. In addition, the propylene selectivity was consistently at a high level.

Tables 1 and 2 show the 1/ _kd of catalysts A3, A5, A9 to 12, and catalysts B3 to B6, B9, and B10 at a reaction temperature of 600° C. It was found that the catalysts of Examples 3, 5, and 9 to 12, which contained platinum element, M element, and MFI zeolite, had longer average catalyst life than the catalysts of Comparative Examples 3 to 6, 9, and 10, which contained platinum element and MFI zeolite but did not contain M element.

The dehydrogenation catalyst of the present invention is useful because it can produce propylene over a long period of time.

Claims (8)

A dehydrogenation catalyst for producing propylene by a dehydrogenation reaction of propane, comprising:
Contains MFI zeolite, a platinum element, and an M element,
The molar ratio of silicon to aluminum element (Si/Al) of the MFI zeolite is 50 or more,
The M element is one or more elements selected from the group consisting of germanium, copper, indium, iron, ruthenium, and rhenium,
A dehydrogenation catalyst, wherein the platinum element and the M element are located within the channels of the MFI zeolite. The dehydrogenation catalyst according to claim 1, wherein the platinum element and the M element form an alloy cluster. The dehydrogenation catalyst according to claim 1 or 2, further comprising manganese oxide or tin oxide, the manganese oxide or the tin oxide being located within the channels of the MFI zeolite. The dehydrogenation catalyst according to claim 1 or 2, wherein the MFI zeolite does not contain aluminum element. The dehydrogenation catalyst according to claim 1 or 2, wherein the M element is germanium. A method for producing the dehydrogenation catalyst according to claim 1 or 2, comprising the steps of:
a hydrothermal synthesis step of hydrothermally synthesizing a mixed solution containing a structure directing agent, a compound containing a platinum element, the compound containing the M element, and a compound containing a silicon element;
an oxidation and calcination step in which the solid obtained in the hydrothermal synthesis step is oxidized and calcined in an oxidizing gas atmosphere to remove the structure-directing agent;
a reduction-calcination step of reducing and calcining the calcined body obtained in the oxidation-calcination step in a reducing gas atmosphere. A method for producing propylene, comprising contacting a feed gas containing propane with the dehydrogenation catalyst according to claim 1 or 2. The method for producing propylene according to claim 7, wherein the reaction temperature is 550 to 650°C.

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