A continuous and efficient method and apparatus for the preparation of hanging tetrahydrodicyclopentadiene.

Abstract

This invention discloses a method for the continuous and efficient preparation of hanging tetrahydrodicyclopentadiene from dicyclopentadiene. The method innovatively combines catalytic hydrogenation and catalytic isomerization processes in series, dividing a single catalytic hydrogenation process into two stages. The two-stage hydrogenation, hydrogenation purification, and isomerization reaction are effectively coupled, achieving the continuous and efficient synthesis of hanging tetrahydrodicyclopentadiene. After stable operation, the yield of hanging tetrahydrodicyclopentadiene reaches over 90%, and the device can operate stably for over 2000 hours. This method eliminates the need for catalyst separation, simplifies the operation, produces few byproducts, exhibits good catalyst activity and stability, and allows for long-term stable operation of the device.

Description

Technical Field

[0001] This invention belongs to the field of novel aerospace fuel preparation technology, specifically relating to a continuous and efficient preparation method and apparatus for hanging tetrahydrodicyclopentadiene. Background Technology

[0002] Exo-THDCPD (also known as JP-10) is a high-energy-density liquid hydrocarbon fuel with advantages such as a low freezing point (<-80℃) and high volumetric calorific value (39.6MJ / L). It can be used as a propellant for aircraft, missiles, torpedoes and rockets, and is currently one of the most widely used high-energy hydrocarbon fuels.

[0003] Hanging tetrahydrodicyclopentadiene is typically obtained from dicyclopentadiene (DCPD) through a series of hydrogenation and isomerization reactions. Specifically, dicyclopentadiene is first hydrogenated to endo-THDCPD, which is then isomerized to hanging tetrahydrodicyclopentadiene. Currently, the industrial synthesis of hanging tetrahydrodicyclopentadiene uses a two-step hydrogenation-isomerization process, employing batch reactors. The hydrogenation catalyst is Raney nickel, and the isomerization catalyst is anhydrous AlCl3. Both catalysts exhibit good catalytic activity and selectivity and are suitable for batch reactors. However, anhydrous AlCl3, due to its strong acidity, causes corrosion to the reaction equipment, and the post-processing of the target product is complex and environmentally unfriendly. Furthermore, due to limitations imposed by certain properties of Raney nickel and anhydrous AlCl3, this process cannot achieve continuous and efficient synthesis of hanging tetrahydrodicyclopentadiene. To address this issue and replace existing processes, researchers both domestically and internationally have conducted in-depth studies on numerous heterogeneous catalysts and supporting processes that have the potential to replace Raney nickel and anhydrous AlCl3. However, these hydrogenation catalysts and isomeric catalysts have poor activity and stability, and have not yet been industrialized.

[0004] In existing technologies, to address the shortcomings of Raney nickel catalysts and hydrogenation techniques, researchers have used amorphous alloy SRNA-4, supported nickel framework materials, supported nickel-based catalysts, supported noble metal-based catalysts, and nickel-based MOF composites to replace Raney nickel. Most of these alternative catalysts still employ batch reactors and related processes, while a few use fixed-bed reactors and one-step hydrogenation processes, resulting in poorer techno-economic performance compared to existing technologies. To address the numerous shortcomings of anhydrous AlCl3 catalysts and isomerization techniques, researchers have used heterogeneous catalysts such as molecular sieves and solid acids to replace AlCl3 catalysts, typically employing batch reactors or fixed-bed reactors. However, these heterogeneous catalysts all suffer from poor activity stability, and industrial application still requires time. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a method and apparatus for the continuous and efficient preparation of hanging tetrahydrodicyclopentadiene from dicyclopentadiene. The method innovatively combines catalytic hydrogenation and catalytic isomerization processes in series, dividing a single hydrogenation process into two stages. It effectively couples the two-stage hydrogenation, hydrogenation purification, and isomerization reaction, achieving continuous and efficient synthesis of hanging tetrahydrodicyclopentadiene. After stable operation, the yield of hanging tetrahydrodicyclopentadiene reaches over 90%, and the apparatus can operate stably for over 2000 hours. This method eliminates the need for catalyst separation, simplifies the operation, produces few byproducts, exhibits good catalyst activity and stability, and allows for long-term stable operation of the apparatus.

[0006] First aspect

[0007] This invention provides a method for the continuous liquid-phase preparation of hanging tetrahydrodicyclopentadiene from dicyclopentadiene. The method uses dicyclopentadiene as a raw material and obtains hanging tetrahydrodicyclopentadiene through a first-stage hydrogenation reaction, a second-stage hydrogenation reaction, a hydrogenation purification reaction, and an isomerization reaction.

[0008] The temperature of the first hydrogenation reaction is 10–80℃, and the pressure of the first hydrogenation reaction is 0.1–4 MPa.

[0009] The temperature of the second-stage hydrogenation reaction is 50–180℃, and the pressure of the second-stage hydrogenation reaction is 0.5–5 MPa;

[0010] The volumetric hourly space velocity was 0.2–5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 50–500.

[0011] The hydrogen-to-oil volume ratio refers to the volume ratio of hydrogen to dicyclopentadiene.

[0012] According to an embodiment of the present invention, the temperature of the first stage of hydrogenation reaction is 30-80°C;

[0013] Preferably, the temperature of the hydrogenation reaction is 60°C.

[0014] According to an embodiment of the present invention, the pressure of a hydrogenation reaction stage is 2 MPa.

[0015] According to an embodiment of the present invention, the temperature of the two-stage hydrogenation reaction is 100-180°C;

[0016] Preferably, the temperature of the two-stage hydrogenation reaction is 150-180°C, more preferably 160-170°C.

[0017] According to an embodiment of the present invention, the pressure of the two-stage hydrogenation reaction is 0.5-4 MPa, for example 2 MPa.

[0018] According to an embodiment of the present invention, the temperature of the hydrorefining reaction is 100–400°C, the pressure of the hydrorefining reaction is 0.5–5 MPa, and the volume hourly space velocity is 0.2–5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 50–500.

[0019] According to an embodiment of the present invention, the temperature of the hydrorefining reaction is 200-380°C;

[0020] Preferably, the temperature of the hydrogenation refining reaction is 300-380℃, more preferably 320-350℃.

[0021] According to an embodiment of the present invention, the pressure of the hydrorefining reaction is 2 MPa.

[0022] According to an embodiment of the present invention, the isomerization reaction temperature is 100–200°C, the isomerization reaction pressure is 0.5–5 MPa, and the volume hourly space velocity is 0.2–5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 50–500.

[0023] According to an embodiment of the present invention, the temperature of the isomerization reaction is 100-180°C;

[0024] Preferably, the isomerization reaction temperature is 120-150℃.

[0025] According to an embodiment of the present invention, the dicyclopentadiene is a dicyclopentadiene solution with a mass percentage of 30% to 90%; the solvent of the solution is selected from C5-C15 aliphatic hydrocarbons, such as petroleum ether, n-hexane, and cyclohexane.

[0026] According to an embodiment of the present invention, the catalyst for the first-stage hydrogenation reaction is one or a mixture of two or more noble metal catalysts such as ruthenium, rhodium, palladium, and platinum; preferably, the catalyst for the first-stage hydrogenation reaction is selected from Pd / Al2O3, Pt / Al2O3, and Ru / Al2O3.

[0027] According to an embodiment of the present invention, a hydrogenation reaction is carried out in a fixed-bed reactor.

[0028] According to an embodiment of the present invention, the two-stage hydrogenation catalyst is one or more of non-precious metal catalysts with hydrogenation activity, such as nickel and cobalt; preferably, the catalyst for the two-stage hydrogenation reaction is selected from nickel-supported catalysts, such as Ni / Al2O3 and Ni / SiO2.

[0029] According to an embodiment of the present invention, the two-stage hydrogenation reaction is carried out in a fixed-bed reactor.

[0030] According to an embodiment of the present invention, the hydrorefining catalyst is one or a mixture of two or more heterogeneous catalysts containing metals such as nickel, molybdenum, tungsten, and molybdenum; preferably, the hydrorefining catalyst is selected from Ni-Mo / Al2O3, Pd / Al2O3, Ni / HY, and Ni / Beta.

[0031] According to an embodiment of the present invention, the hydrorefining reaction is carried out in a fixed-bed reactor.

[0032] According to an embodiment of the present invention, the metal catalyst containing hydrogenation activity needs to be reduced and activated at 200–500°C (e.g., 500°C) and in a hydrogen atmosphere.

[0033] According to an embodiment of the present invention, the heterogeneous catalyst is one or a mixture of two or more of supported Lewis acid or molecular sieve catalysts.

[0034] According to an embodiment of the present invention, the isomerization reaction is carried out in a fixed-bed reactor.

[0035] Second aspect

[0036] This invention provides an apparatus for the continuous and efficient liquid-phase preparation of hanging tetrahydrodicyclopentadiene from dicyclopentadiene. The apparatus includes a first-stage hydrogenation unit, a second-stage hydrogenation unit, a hydrogenation purification unit, and an isomerization unit.

[0037] According to an embodiment of the present invention, the first-stage hydrogenation unit, the second-stage hydrogenation unit, the hydrogenation refining unit, and the isomerization unit are connected in series. Each of the first-stage hydrogenation unit, the second-stage hydrogenation unit, and the hydrogenation refining unit includes a corresponding hydrogenation catalyst and / or a fixed-bed reactor. The isomerization unit includes an isomerization catalyst and / or a fixed-bed reactor.

[0038] The beneficial effects of the present invention are as follows: The preparation method of the present invention effectively couples two stages of hydrogenation, hydrogenation purification and isomerization to achieve continuous and efficient synthesis of hanging tetrahydrodicyclopentadiene. This process does not require catalyst separation, the operation is simple, there are few by-products, the catalyst has good activity and stability, the yield of hanging tetrahydrodicyclopentadiene reaches more than 90%, and it can operate stably for more than 2000 hours. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the method of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0041] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0042] Example 1 (The Influence of the Type of Hydrogenation Catalyst)

[0043] Using a 30 wt% dicyclopentadiene solution in n-hexane as the reactant, this example investigates the effect of the type of hydrogenation catalyst on the conversion of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene. Certain amounts of the primary hydrogenation catalyst, nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride-supported catalyst were added to a primary hydrogenation fixed-bed reactor, a secondary hydrogenation fixed-bed reactor, a hydrogenation refining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The conditions were: primary hydrogenation pressure 2 MPa, primary hydrogenation temperature 60 °C, secondary hydrogenation pressure 2 MPa, secondary hydrogenation temperature 170 °C, hydrogenation refining pressure 2 MPa, hydrogenation refining temperature 350 °C, isomerization pressure 0.5 MPa, isomerization temperature 150 °C, and volume hourly space velocity (VHSV) 1.5 h⁻¹. -1 The reaction was carried out under a hydrogen-to-oil volume ratio of 500. Before the reaction, a metal catalyst with hydrogenation activity was reduced and activated at 500°C under a hydrogen atmosphere for 5 hours. The reaction results are as follows:

[0044]

[0045] Example 2 (Influence of Hydrorefining Catalyst Type)

[0046] Using a 30 wt% dicyclopentadiene solution in n-hexane as the reaction feedstock, this example investigates the effect of the type of hydrorefining catalyst on the conversion rate of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene. Certain amounts of palladium-supported catalyst, nickel-supported catalyst, hydrorefining catalyst, and anhydrous aluminum chloride-supported catalyst were added to a single-stage hydrogenation fixed-bed reactor, a two-stage hydrogenation fixed-bed reactor, a hydrorefining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The conditions were: a single-stage hydrogenation pressure of 2 MPa, a single-stage hydrogenation temperature of 60 °C, a second-stage hydrogenation pressure of 2 MPa, a second-stage hydrogenation temperature of 170 °C, a hydrorefining pressure of 2 MPa, a hydrorefining temperature of 350 °C, an isomerization pressure of 0.5 MPa, an isomerization temperature of 150 °C, and a volume hourly space velocity of 1.5 h⁻¹. -1 The reaction was carried out under a hydrogen-to-oil volume ratio of 500. Before the reaction, a metal catalyst with hydrogenation activity was reduced and activated at 500°C under a hydrogen atmosphere for 5 hours. The reaction results are as follows:

[0047]

[0048] Example 3 (The Influence of Hydrogenation Temperature in One Stage)

[0049] Using a 30 wt% dicyclopentadiene solution in n-hexane as the reactant, this example investigates the effect of the first-stage hydrogenation temperature on the conversion of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene. Certain amounts of palladium-supported catalyst, nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride-supported catalyst were added to a first-stage hydrogenation fixed-bed reactor, a second-stage hydrogenation fixed-bed reactor, a hydrogenation refining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The conditions were: first-stage hydrogenation pressure 2 MPa, second-stage hydrogenation pressure 2 MPa, second-stage hydrogenation temperature 170 °C, hydrogenation refining pressure 2 MPa, hydrogenation refining temperature 350 °C, isomerization pressure 0.5 MPa, isomerization temperature 150 °C, and volume hourly space velocity (VHSV) 1.5 h⁻¹. -1 The reaction was carried out under a hydrogen-to-oil volume ratio of 500. Before the reaction, a metal catalyst with hydrogenation activity was reduced and activated at 500°C under a hydrogen atmosphere for 5 hours. The reaction results are as follows:

[0050]

[0051] Example 4 (Influence of Two-Stage Hydrogenation Pressure)

[0052] Using a 30 wt% dicyclopentadiene solution in n-hexane as the reactant, this example investigates the effect of the two-stage hydrogenation pressure on the conversion rate of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene. Certain amounts of palladium-supported catalyst, nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride-supported catalyst were added to a single-stage hydrogenation fixed-bed reactor, a two-stage hydrogenation fixed-bed reactor, a hydrogenation refining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The conditions were: a single-stage hydrogenation pressure of 2 MPa, a single-stage hydrogenation temperature of 60 °C, a two-stage hydrogenation temperature of 170 °C, a hydrogenation refining pressure of 2 MPa, a hydrogenation refining temperature of 350 °C, an isomerization pressure of 0.5 MPa, an isomerization temperature of 150 °C, and a volume hourly space velocity of 1.5 h⁻¹. -1 The reaction was carried out under a hydrogen-to-oil volume ratio of 500. Before the reaction, a metal catalyst with hydrogenation activity was reduced and activated at 500°C under a hydrogen atmosphere for 5 hours. The reaction results are as follows:

[0053]

[0054] Example 5 (Effect of Hydrorefining Temperature)

[0055] Using a 30 wt% dicyclopentadiene solution in n-hexane as the reactant, this example investigates the effect of hydrorefining temperature on the conversion rate of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene. Certain amounts of palladium-supported catalyst, nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride-supported catalyst were added to a single-stage hydrogenation fixed-bed reactor, a two-stage hydrogenation fixed-bed reactor, a hydrorefining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The conditions were: a single-stage hydrogenation pressure of 2 MPa, a single-stage hydrogenation temperature of 60 °C, a second-stage hydrogenation pressure of 2 MPa, a second-stage hydrogenation temperature of 170 °C, a hydrorefining pressure of 2 MPa, an isomerization pressure of 0.5 MPa, an isomerization temperature of 150 °C, and a volume hourly space velocity of 1.5 h⁻¹. -1 The reaction was carried out under a hydrogen-to-oil volume ratio of 500. Before the reaction, a metal catalyst with hydrogenation activity was reduced and activated at 500°C under a hydrogen atmosphere for 5 hours. The reaction results are as follows:

[0056]

[0057] Example 6 (Effect of Isomerization Temperature)

[0058] Using a 30 wt% dicyclopentadiene solution in n-hexane as the reaction feedstock, this example investigates the effect of isomerization temperature on the conversion rate of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene. Certain amounts of palladium-supported catalyst, nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride-supported catalyst were added to a single-stage hydrogenation fixed-bed reactor, a two-stage hydrogenation fixed-bed reactor, a hydrogenation purification fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The conditions were: a single-stage hydrogenation pressure of 2 MPa, a single-stage hydrogenation temperature of 60 °C, a second-stage hydrogenation pressure of 2 MPa, a second-stage hydrogenation temperature of 170 °C, a hydrogenation purification pressure of 2 MPa, a hydrogenation purification temperature of 350 °C, an isomerization pressure of 0.5 MPa, and a volume hourly space velocity of 1.5 h⁻¹. -1 The reaction was carried out under a hydrogen-to-oil volume ratio of 500. Before the reaction, a metal catalyst with hydrogenation activity was reduced and activated at 500°C under a hydrogen atmosphere for 5 hours. The reaction results are as follows:

[0059]

[0060]

[0061] Comparative Example 1: (Influence of Hydrogenation Method)

[0062] Using a 30 wt% hexane solution of dicyclopentadiene as the reaction raw material, this example investigates the effect of hydrogenation method on the conversion rate of dicyclopentadiene and the selectivity of tetrahydrodicyclopentadiene.

[0063] (1) A certain amount of palladium-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride catalyst were added to a single-stage hydrogenation fixed-bed reactor, a hydrogenation refining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The hydrogenation pressure in the first stage was 2 MPa, the hydrogenation temperature in the first stage was 60 °C, the hydrogenation refining pressure was 2 MPa, the hydrogenation refining temperature was 350 °C, the isomerization pressure was 0.5 MPa, the isomerization temperature was 150 °C, and the volume hourly space velocity was 1.5 h⁻¹. -1 The reaction was carried out under the condition that the hydrogen-to-oil volume ratio was 500.

[0064] (2) Certain amounts of nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride catalyst were added to a two-stage hydrogenation fixed-bed reactor, a hydrogenation refining fixed-bed reactor, and an isomerization fixed-bed reactor, respectively. The hydrogenation pressure in the two-stage reactor was 2 MPa, the hydrogenation temperature was 170 °C, the hydrogenation refining pressure was 2 MPa, the hydrogenation refining temperature was 350 °C, the isomerization pressure was 0.5 MPa, the isomerization temperature was 150 °C, and the volume hourly space velocity was 1.5 h⁻¹. -1 The reaction was carried out under the condition that the hydrogen-to-oil volume ratio was 500.

[0065] (3) Certain amounts of palladium-supported catalyst, nickel-supported catalyst, nickel-molybdenum catalyst, and anhydrous aluminum chloride catalyst were respectively added to a first-stage hydrogenation fixed-bed reactor, a second-stage hydrogenation fixed-bed reactor, a hydrogenation refining fixed-bed reactor, and an isomerization fixed-bed reactor. The hydrogenation pressure in the first stage was 2 MPa, the hydrogenation temperature in the first stage was 60 °C, the hydrogenation pressure in the second stage was 2 MPa, the hydrogenation temperature in the second stage was 170 °C, the hydrogenation refining pressure was 2 MPa, the hydrogenation refining temperature was 350 °C, the isomerization pressure was 0.5 MPa, the isomerization temperature was 150 °C, and the volume hourly space velocity was 1.5 h⁻¹. -1 The reaction was carried out under the condition that the hydrogen-to-oil volume ratio was 500.

[0066] (4) Certain amounts of palladium-supported catalyst, nickel-supported catalyst, and anhydrous aluminum chloride-supported catalyst were respectively added to a first-stage hydrogenation fixed-bed reactor, a second-stage hydrogenation fixed-bed reactor, and an isomerization fixed-bed reactor. The hydrogenation pressure in the first stage was 2 MPa, the hydrogenation temperature in the first stage was 60 °C, the hydrogenation pressure in the second stage was 2 MPa, the hydrogenation temperature in the second stage was 170 °C, the isomerization pressure was 0.5 MPa, the isomerization temperature was 150 °C, and the volume hourly space velocity was 1.5 h⁻¹. -1 The reaction was carried out under the condition that the hydrogen-to-oil volume ratio was 500.

[0067] The metal catalyst with hydrogenation activity was reduced and activated at 500℃ under a hydrogen atmosphere for 5 hours before the reaction. The reaction results are as follows:

[0068]

[0069] The research revealed that, compared to directly employing a single two-stage hydrogenation process, two-stage coupling (dividing the hydrogenation reaction into a single-stage and a two-stage process) effectively addresses the severe exothermic issue during hydrogenation. Furthermore, this two-stage coupling combined with hydrorefining improves feed conversion rate, product selectivity, and effectively extends the lifespan of the hydrogenation catalyst, thereby increasing the stable operating time. The two-stage coupling combined with hydrorefining resulted in a stable operating time exceeding 2000 hours for this system.

[0070] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the continuous liquid-phase preparation of hanging tetrahydrodicyclopentadiene from dicyclopentadiene, wherein the method uses dicyclopentadiene as raw material and obtains hanging tetrahydrodicyclopentadiene through a first-stage hydrogenation reaction, a second-stage hydrogenation reaction, a hydrogenation purification reaction and an isomerization reaction. in, The temperature of the first-stage hydrogenation reaction is 60℃, and the pressure of the first-stage hydrogenation reaction is 2MPa. The temperature of the second-stage hydrogenation reaction is 150–180°C, and the pressure of the second-stage hydrogenation reaction is 2 MPa. The volume hourly space velocity was 1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500; The hydrogen-to-oil volume ratio refers to the volume ratio of hydrogen to dicyclopentadiene. The catalyst for the hydrogenation reaction was selected from Pd / Al2O3; The catalyst for the second-stage hydrogenation reaction is a nickel-supported catalyst; The catalyst for the hydrorefining reaction is selected from Ni-Mo / Al2O3 and Pd / Al2O3; the temperature of the hydrorefining reaction is 320-350℃; and the pressure of the hydrorefining reaction is 2 MPa. The catalyst for the isomerization reaction was an anhydrous aluminum chloride catalyst; the temperature of the isomerization reaction was 150℃; and the pressure of the isomerization reaction was 0.5 MPa. The first-stage hydrogenation reaction, the second-stage hydrogenation reaction, the hydrogenation refining reaction, and the isomerization reaction are carried out in a fixed-bed reactor.

2. The method according to claim 1, characterized in that, The temperature for the second-stage hydrogenation reaction is 160-170℃.

3. The method according to claim 1 or 2, characterized in that, The dicyclopentadiene is a dicyclopentadiene solution with a mass percentage of 30% to 90%. The solvent for the solution is selected from C5-C15 aliphatic hydrocarbons.

4. The method according to claim 3, characterized in that, The solvent for the solution is selected from petroleum ether, n-hexane, and cyclohexane.

5. The method according to claim 1 or 2, characterized in that, Metal catalysts with hydrogenation activity need to be reduced and activated at 200–500°C in a hydrogen atmosphere.

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