A cobalt-based catalyst for propane dehydrogenation to propylene and its synthesis method

Abstract

This application discloses a highly efficient cobalt-based catalyst for propane dehydrogenation to propylene and its synthesis method. Treatment of Silicate-1 seed crystals with an alkali causes the surface Si-OH groups to lose protons, forming a mesoporous microenvironment structure rich in Si-O-, which adsorbs Co through electrostatic interactions. 2+ Ions were then encapsulated within the Silicate-1 zeolite framework by dry gel conversion and calcination to anchor CoO clusters and Co-Si-O species at individual sites, maintaining high catalytic performance in stability tests. Its advantages include stable propane dehydrogenation at 500℃ for 300 h and a propylene formation rate of 27.5 mmol / (g) at 580℃. cat ·h).

Description

Technical Field

[0001] This application belongs to the field of catalyst preparation, specifically relating to a highly efficient cobalt-based catalyst for the dehydrogenation of propane to propylene and its synthesis method. Background Technology

[0002] Propylene is an important petrochemical product, mainly used in the synthesis of high-value-added chemicals such as polypropylene, acrylonitrile, propylene oxide, and acetone. In recent years, the development of hydraulic fracturing technology has enabled large-scale, low-cost extraction of shale gas, providing inexpensive and abundant feedstock for the propane-to-propylene route. Among these technologies, the direct propane dehydrogenation (PDH) process has attracted considerable attention due to its advantages, including a single product distribution and high propylene selectivity.

[0003] To date, PDH processes have mainly focused on two major catalyst classes: PtSn / Al2O3 (Oleflex process) and Cr / Al2O3 (Catofin process). However, the high cost of Pt and the chemical toxicity of Cr have significantly limited further development. Additionally, VO x GaO x and ZnO x The activation of CH bonds in propane by Lewis (MO) sites in metal oxides has also been widely reported. The interaction between the lattice oxygen of metal oxides and propane molecules transforms direct dehydrogenation into oxidative dehydrogenation. The cyclic reduction-oxidation process of oxide catalysts leads to catalyst sintering and deactivation during regeneration.

[0004] Co-based catalysts have shown great potential in alkane dehydrogenation due to their low cost, environmental friendliness, and excellent CH bond activation ability. However, for Co-based catalysts, differences in preparation conditions such as the support, loading method, and loading amount often lead to variations in catalytic performance. Chinese patent CN111589449A discloses a method for preparing a cobalt-based catalyst for propane dehydrogenation and its applications, employing a one-step hydrothermal method to support Co on an Al2O3 support. This catalyst exhibits advantages such as good dehydrogenation stability, simple preparation process, environmental friendliness, and promising industrial application prospects; however, the conversion rate of propane and the selectivity for propylene still need improvement. Chinese patent CN115155591A discloses Co-based catalysts supported on Al2O3 with different morphologies for propane dehydrogenation, using Al2O3 rich in five-coordinate Al... 3+Using Al2O3 nanorods as a support, Co is introduced through an equal-volume impregnation method, while citric acid and urea are added to regulate the metal dispersion. This method, which precisely stabilizes Co single atoms or sub-nanoclusters within a "confined space" through strong metal-support interactions, can produce highly dispersed active sites. However, when the metal active sites are at the scale of sub-nanoclusters or even single atoms, the surface free energy of the metal increases. Furthermore, the reaction is typically carried out at high temperatures and in a strongly reducing atmosphere, making the sub-nanoclusters and single atoms susceptible to severe sintering or reduction and deactivation. Chinese patent CN114984999A discloses a method for preparing a Silicate-1 zeolite-supported cobalt composite catalyst and its application, using it in the propane dehydrogenation reaction. The active metal Co and an additive are added to a clear, transparent zeolite mother liquor, followed by hydrothermal treatment to obtain the Co / Silicate-1 catalyst. Although this catalyst has a high initial propane conversion rate, its stability is poor, requiring frequent oxidative regeneration. This invention provides a method for synthesizing a stable cobalt-based catalyst for the dehydrogenation of propane to propylene, namely, anchoring Co species on a defect-rich S-1 support, and then encapsulating the Co species within the framework of Silicate-1 zeolite through secondary growth of seed crystals. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a highly active and stable catalyst for propane dehydrogenation reaction.

[0006] The propane dehydrogenation reaction was carried out in a fixed-bed reactor. A certain amount of catalyst (40-60 mesh) was weighed and then loaded into the reactor. The temperature was increased to 500℃ at 5℃ / min under a N2 atmosphere of 30 mL / min, and the reaction was switched to propane for dehydrogenation.

[0007] The technical solution adopted in this application is: a highly efficient catalyst for propane dehydrogenation to propylene and its preparation method. The catalyst uses Silicate-1 zeolite as the main support and Co-groups as the main active center. The following two factors are mainly utilized to jointly promote and improve the catalytic activity and stability of the highly efficient catalyst for propane dehydrogenation to propylene.

[0008] Firstly, Silicate-1 seed crystals are treated with alkali, causing the surface Si-OH groups to lose protons and form a mesoporous microenvironment structure rich in Si-O-. Then, Co is adsorbed through electrostatic interaction. 2+ ion;

[0009] Secondly, Co is confined and encapsulated within the framework of Silicate-1 zeolite through secondary growth of seed crystals, denoted as Co@S-1.

[0010] The method includes the following steps:

[0011] I. Preparation of Silicate-1 seed crystals:

[0012] (1) Mix tetraethyl orthosilicate, tetrapropylammonium hydroxide and deionized water, and stir at room temperature until clear to obtain solution A;

[0013] (2) Transfer the above solution A to a hydrothermal reactor and hydrotherm at 90°C for 2 days to obtain solution B;

[0014] (4) Wash the solid substance in solution B with deionized water until neutral, then dry and calcine to obtain S-1 seed crystals;

[0015] In step (1), the molar composition of solution A is SiO2∶TPAOH∶H2O=1∶0.45∶20

[0016] II. Alkali treatment of Silicate-1 seed crystals:

[0017] (1) A certain amount of Silicate-1 seed crystals were dispersed in a 0.3 mol / L alkaline solution and treated at 70℃ for 4 h to obtain solution C;

[0018] (2) The solid material in solution C is filtered, washed and dried to obtain the S-1 carrier after alkali treatment.

[0019] The base in step (1) is one or more of sodium hydroxide and piperidine tetrapropylammonium hydroxide.

[0020] In step (2), the solid-liquid ratio of S-1 seed crystal to alkaline solution is 1:10-1:50 (g:mL).

[0021] III. Preparation of Co@S-1 catalyst:

[0022] (1) Dissolve the Co precursor in deionized water to obtain solution D;

[0023] (2) Add the Silicate-1 carrier treated with the above alkali to the solution D to obtain solution E;

[0024] (3) Stir solution E magnetically at 40℃ for 12h and dry it in an oven at 80℃ for 12h to obtain powder F;

[0025] (4) Mix powder F, silica and tetrapropylammonium bromide evenly in a mortar, then crystallize at 180°C for 3 days using the dry gel conversion method, and finally wash, dry and calcine to obtain the catalyst;

[0026] In step (1), one or more of the following are added: cobalt nitrate hexahydrate, cobalt acetylacetonate, cobalt chloride, cobalt sulfate, and cobalt oxalate.

[0027] In step (2), the mass fraction of Co is 0.1-2 wt% of the Silicate-1 carrier.

[0028] The above-mentioned technical solution adopted in this application can achieve the following beneficial effects:

[0029] To further improve catalytic performance and stability, this application incorporates the following innovations: First, Silicate-1 zeolite is treated with alkali to cause the Si-OH groups on the zeolite surface to lose protons, forming a mesoporous microenvironment structure rich in Si-O-. Second, Co is adsorbed through electrostatic interactions. 2+ The ions were then anchored and encapsulated within the Silicate-1 zeolite framework via dry gel conversion and calcination. Compared to composite materials synthesized in situ using conventional methods, the catalyst prepared by this method exhibits good metal dispersion, relatively strong interaction with the zeolite, and is less prone to reduction or sintering during dehydrogenation reactions. Furthermore, this catalyst demonstrates high propane conversion and selectivity at low temperatures, and showed stable propane dehydrogenation for 300 h at 500 °C; and at 580 °C for 2.4 h. -1 The propylene formation rate can reach 27.5 mmol / (g). cat ·h). Attached Figure Description

[0030] Figure 1 Propane conversion and propylene selectivity of Co@S-1 catalyst at 500℃

[0031] Figure 2 SEM image of the morphology of the Co@S-1 catalyst prepared in Example 1

[0032] Figure 3 STEM observation of the Co@S-1 catalyst prepared in Example 1 and Co element mapping. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] Example 1.

[0035] (1) Catalyst preparation

[0036] Preparation of Silicate-1 seed crystals:

[0037] 103.64 g TEOS, 183.00 mL TPAOH (25 wt.%), and 42.60 g deionized water were mixed and stirred continuously at room temperature for 4 h. The mixture was then transferred to a reaction vessel and reacted at 90 °C for 48 h. The resulting solid product was then centrifuged, washed, dried at 100 °C for 12 h, and finally calcined in air at 550 °C for 5 h to obtain Silicate-1 seed crystals.

[0038] Alkali treatment of Silicate-1 seed crystals:

[0039] 4g of Silicate-1 seed crystals were dispersed in 160mL of tetrapropyl sodium hydroxide solution (0.3mol / L) and treated at 70℃ for 4h. The solid material was filtered, washed and dried to obtain the alkali-treated Silicate-1 support.

[0040] Preparation of Co@S-1 catalyst:

[0041] 0.05 g of cobalt nitrate hexahydrate was dissolved in 10 mL of deionized water and stirred until clear. Then, 0.5 g of alkali-treated Silicate-1 seed crystals were added, and the mixture was stirred at 40 °C for 12 h and dried in an oven at 80 °C for 12 h. The mixture was then mixed evenly with silica and tetrapropylammonium bromide in a mortar and crystallized at 180 °C for 72 h using a dry gel conversion method. Finally, the mixture was washed, dried, and calcined to obtain the Co@S-1 catalyst.

[0042] (2) Catalyst performance testing

[0043] The propane dehydrogenation reaction was carried out in a fixed-bed reactor. 0.2 g of catalyst (40–60 mesh) was weighed and added to the reactor. The temperature was increased to 500 °C at 5 °C / min under a N₂ atmosphere of 30 mL / min, and then switched to propane for the dehydrogenation reaction. The catalytic activity and stability test results are shown in Table 1.

[0044] Example 2.

[0045] (1) Catalyst preparation

[0046] Preparation of Silicate-1 seed crystals:

[0047] 103.64 g TEOS, 183.00 mL TPAOH (25 wt.%), and 42.60 g deionized water were mixed and stirred continuously at room temperature for 4 h. The mixture was then transferred to a reaction vessel and reacted at 90 °C for 48 h. The resulting solid product was then centrifuged, washed, dried at 100 °C for 12 h, and finally calcined in air at 550 °C for 5 h to obtain S-1 seed crystals.

[0048] Alkali treatment of Silicate-1 seed crystals:

[0049] 4g of S-1 seed crystals were dispersed in 200mL of sodium hydroxide solution (0.3mol / L) and treated at 70℃ for 4h. The solid material was filtered, washed and dried to obtain the alkali-treated Silicate-1 support.

[0050] Preparation of Co@S-1 catalyst:

[0051] 0.05 g of cobalt acetylacetonate was dissolved in 10 mL of deionized water and stirred until clear. Then, 0.5 g of alkali-treated Silicate-1 seed crystals were added, stirred at 40 °C for 12 h, and dried in an oven at 80 °C for 12 h. The mixture was then mixed evenly with silica and tetrapropylammonium bromide in a mortar. The mixture was then crystallized at 180 °C for 72 h using a dry gel conversion method. Finally, the mixture was washed, dried, and calcined to obtain the Co@S-1 catalyst.

[0052] (2) Catalyst performance testing

[0053] The propane dehydrogenation reaction was carried out in a fixed-bed reactor. 0.2 g of catalyst (40–60 mesh) was weighed and added to the reactor. The temperature was increased to 500 °C at 5 °C / min under a N₂ atmosphere of 30 mL / min, and then switched to propane for the dehydrogenation reaction. The catalytic activity and stability test results are shown in Table 1.

[0054] Example 3.

[0055] (1) Catalyst preparation

[0056] Preparation of S-1 seed crystals:

[0057] 103.64 g TEOS, 183.00 mL TPAOH (25 wt.%), and 42.60 g deionized water were mixed and stirred continuously at room temperature for 4 h. The mixture was then transferred to a reaction vessel and reacted at 90 °C for 48 h. The resulting solid product was then centrifuged, washed, dried at 100 °C for 12 h, and finally calcined in air at 550 °C for 5 h to obtain S-1 seed crystals.

[0058] Alkali treatment of Silicate-1 seed crystals:

[0059] 4g of Silicate-1 seed crystals were dispersed in 120mL of piperidine solution (0.3mol / L) and treated at 70℃ for 4h. The solid material was filtered, washed and dried to obtain the alkali-treated S-1 support.

[0060] Preparation of Co@S-1 catalyst:

[0061] 0.05 g of cobalt oxalate was dissolved in 10 mL of deionized water and stirred until clear. Then, 0.5 g of alkali-treated Silicate-1 seed crystals were added and stirred at 40 °C for 12 h. The mixture was then dried in an oven at 80 °C for 12 h. After that, it was mixed evenly with silica and tetrapropylammonium bromide in a mortar. Then, it was crystallized at 180 °C for 72 h using the dry gel conversion method. Finally, it was washed, dried and calcined to obtain the Co@S-1 catalyst.

[0062] (2) Catalyst performance testing

[0063] The propane dehydrogenation reaction was carried out in a fixed-bed reactor. 0.2 g of catalyst (40–60 mesh) was weighed and added to the reactor. The temperature was increased to 500 °C at 5 °C / min under a N₂ atmosphere of 30 mL / min, and then switched to propane for the dehydrogenation reaction. The catalytic activity and stability test results are shown in Table 1.

[0064] Example 4.

[0065] (1) Catalyst preparation

[0066] Preparation of Silicate-1 seed crystals:

[0067] 103.64 g TEOS, 183.00 mL TPAOH (25 wt.%), and 42.60 g deionized water were mixed and stirred continuously at room temperature for 4 h. The mixture was then transferred to a reaction vessel and reacted at 90 °C for 48 h. The resulting solid product was then centrifuged, washed, dried at 100 °C for 12 h, and finally calcined in air at 550 °C for 5 h to obtain S-1 seed crystals.

[0068] Alkali treatment of Silicate-1 seed crystals:

[0069] 4g of Silicate-1 seed crystals were dispersed in 80mL of a mixed solution of sodium hydroxide and piperidine (0.3mol / L) and treated at 70℃ for 4h. The solid material was then filtered, washed, and dried to obtain the alkali-treated Silicate-1 support.

[0070] Preparation of Co@S-1 catalyst:

[0071] 0.05 g of cobalt chloride was dissolved in 10 mL of deionized water and stirred until clear. Then, 0.5 g of alkali-treated Silicate-1 seed crystals were added and stirred at 40 °C for 12 h. The mixture was then dried in an oven at 80 °C for 12 h. After that, it was mixed evenly with silica and tetrapropylammonium bromide in a mortar. Then, it was crystallized at 180 °C for 72 h using the dry gel conversion method. Finally, it was washed, dried and calcined to obtain the Co@S-1 catalyst.

[0072] (2) Catalyst performance testing

[0073] The propane dehydrogenation reaction was carried out in a fixed-bed reactor. 0.2 g of catalyst (40–60 mesh) was weighed and added to the reactor. The temperature was increased to 500 °C at 5 °C / min under a N₂ atmosphere of 30 mL / min, and then switched to propane for the dehydrogenation reaction. The catalytic activity and stability test results are shown in Table 1.

[0074] Example 5.

[0075] (1) Catalyst preparation

[0076] Preparation of Silicate-1 seed crystals:

[0077] 103.64 g TEOS, 183.00 mL TPAOH (25 wt.%), and 42.60 g deionized water were mixed and stirred continuously at room temperature for 4 h. The mixture was then transferred to a reaction vessel and reacted at 90 °C for 48 h. The resulting solid product was then centrifuged, washed, dried at 100 °C for 12 h, and finally calcined in air at 550 °C for 5 h to obtain S-1 seed crystals.

[0078] Alkali treatment of Silicate-1 seed crystals:

[0079] 4g of S-1 seed crystals were dispersed in 40mL of tetrapropylammonium hydroxide solution (0.3mol / L) and treated at 70℃ for 4h. The solid material was filtered, washed and dried to obtain the alkali-treated S-1 support.

[0080] Preparation of Co@S-1 catalyst:

[0081] 0.05 g of anhydrous cobalt sulfate was dissolved in 10 mL of deionized water and stirred until clear. Then, 0.5 g of alkali-treated Silicate-1 seed crystals were added, stirred at 40 °C for 12 h, and dried in an oven at 80 °C for 12 h. The mixture was then mixed evenly with silica and tetrapropylammonium bromide in a mortar. The mixture was then crystallized at 180 °C for 72 h using a dry gel conversion method. Finally, the mixture was washed, dried, and calcined to obtain the Co@S-1 catalyst.

[0082] (2) Catalyst performance testing

[0083] The propane dehydrogenation reaction was carried out in a fixed-bed reactor. 0.2 g of catalyst (40–60 mesh) was weighed and added to the reactor. The temperature was increased to 500 °C at 5 °C / min under a N₂ atmosphere of 30 mL / min, and then switched to propane for the dehydrogenation reaction. The catalytic activity and stability test results are shown in Table 1.

[0084] Table 1. Results of activity and stability tests for propane dehydrogenation to propylene.

[0085]

[0086]

[0087] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included in the rights of this application.

Claims

1. A Co-based catalyst for propane dehydrogenation to propylene, characterized in that, The catalyst is prepared by anchoring Co species on a defect-rich Silicate-1 support, followed by secondary seeding to confine and encapsulate the Co within the framework of the Silicate-1 zeolite, denoted as Co@S-1. The catalyst is prepared using a secondary seeding method, with the following steps: Step 1: Preparation of Silicate-1 seed crystals: (1) Mix tetraethyl orthosilicate, tetrapropylammonium hydroxide and deionized water, and stir at room temperature until clear to obtain solution A; (2) Transfer the above solution A to a hydrothermal reactor and hydrotherm at 90°C for 2 days to obtain solution B; (4) Wash the solid substance in solution B with deionized water until neutral, then dry and calcine to obtain Silicate-1 seed crystals; In the preparation of Silicate-1 seed crystals (1), the molar composition of solution A is SiO2:TPAOH:H2O=1:0.45:20; Step 2: Alkali treatment of Silicate-1 seed crystals: (1) A certain amount of Silicate-1 seed crystals were dispersed in a 0.3 mol / L alkaline solution, the alkaline being one or more of sodium hydroxide, piperidine, and tetrapropylammonium hydroxide, and treated at 70℃ for 4 h to obtain solution C; (2) The solid material in solution C was filtered, washed and dried to obtain the Silicate-1 carrier after alkali treatment; Step 3: Preparation of Co@S-1 catalyst: (1) Dissolve the Co source in deionized water. The Co source is one or more of cobalt nitrate hexahydrate, cobalt acetylacetonate, cobalt chloride, and cobalt sulfate to obtain solution D. (2) Add the Silicate-1 carrier treated with the above alkali to the solution D to obtain solution E; (3) Stir solution E magnetically at 40℃ for 12h and dry it in an oven at 80℃ for 12h to obtain powder F; (4) Mix powder F, silica and tetrapropylammonium bromide evenly in a mortar, then crystallize at 180°C for 3 days using the dry gel conversion method, and finally wash, dry and calcine to obtain the catalyst.

2. A method for preparing a Co-based catalyst for propane dehydrogenation to propylene, characterized in that, The catalyst is prepared by anchoring Co species on a defect-rich Silicate-1 support, followed by secondary seeding to confine and encapsulate the Co within the framework of the Silicate-1 zeolite, denoted as Co@S-1. The catalyst is prepared using a secondary seeding method, with the following steps: Step 1: Preparation of Silicate-1 seed crystals: (1) Mix tetraethyl orthosilicate, tetrapropylammonium hydroxide and deionized water, and stir at room temperature until clear to obtain solution A; (2) Transfer the above solution A to a hydrothermal reactor and hydrotherm at 90°C for 2 days to obtain solution B; (4) Wash the solid substance in solution B with deionized water until neutral, then dry and calcine to obtain Silicate-1 seed crystals; Step 2: Alkali treatment of Silicate-1 seed crystals: (1) A certain amount of Silicate-1 seed crystals were dispersed in a 0.3 mol / L alkaline solution and treated at 70℃ for 4 h to obtain solution C; (2) The solid material in solution C was filtered, washed and dried to obtain the Silicate-1 carrier after alkali treatment; Step 3: Preparation of Co@S-1 catalyst: (1) Dissolve the Co source in deionized water to obtain solution D; (2) Add the Silicate-1 carrier treated with the above alkali to the solution D to obtain solution E; (3) Stir solution E magnetically at 40℃ for 12h and dry it in an oven at 80℃ for 12h to obtain powder F; (4) Mix powder F, silica and tetrapropylammonium bromide evenly in a mortar, then crystallize at 180°C for 3 days using the dry gel conversion method, and finally wash, dry and calcine to obtain the catalyst.

3. The method according to claim 2, characterized in that, Step 1: Preparation of Silicate-1 seed crystals (1) The molar composition of solution A is SiO2:TPAOH:H2O=1:0.45:

20.

4. The method according to claim 2, characterized in that, Step 2: Alkali treatment. The alkali in Silicate-1 seed crystal (1) is one or more of sodium hydroxide, piperidine, and tetrapropylammonium hydroxide.

5. The method according to claim 2, characterized in that, Step 2: Alkali treatment of Silicate-1 seed crystals (2) The solid-liquid ratio of Silicate-1 seed crystals and alkali solution is 1:10-1:50 g:mL.

6. The method according to claim 2, characterized in that, Step 3: Preparation of Co@S-1 catalyst (1) Add one or more of cobalt nitrate hexahydrate, cobalt acetylacetonate, cobalt chloride, and cobalt sulfate.

7. The method according to claim 2, characterized in that, Step 3: Preparation of Co@S-1 catalyst (1) The mass fraction of Co added accounts for 0.1-5 wt% of the Silicate-1 support.

8. The application of the Co-based catalyst as described in claim 1 in the propane dehydrogenation to propylene production, characterized in that, The propane dehydrogenation to propylene reaction is carried out in a fixed-bed reactor at a reaction temperature of 500-600℃. The reaction gas is introduced into the reactor carrying a Co-based catalyst for propane dehydrogenation to propylene.

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