Propane dehydrogenation catalyst and preparation method thereof

Abstract

The invention belongs to the technical field of petrochemical catalysts, and provides a propane dehydrogenation catalyst and a preparation method thereof. The propane dehydrogenation catalyst comprises an active component and a carrier, the active component is prepared from the following components in percentage by mass: 0.1 to 0.5 percent of main active component Pt, 0.1 to 0.5 percent of first auxiliary active component X and 0.04 to 0.08 percent of second auxiliary active component Y; the carrier is a Sn-SiO2 / Al2O3 composite oxide, and the catalyst is a catalyst. The first auxiliary active component X is K and / or Ba; and the second auxiliary active component Y is one or more of Fe, Co, Ni, Ru, Pd and Ir. The propane dehydrogenation catalyst provided by the invention has the advantages of high propane conversion rate, good propylene selectivity and better cycle performance, and the preparation process is simple and suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical catalysts, and particularly relates to a propane dehydrogenation catalyst and a preparation method thereof. Background Art

[0002] Propylene is a basic raw material for three major synthetic materials, mainly used in the production of polypropylene, acrylonitrile, isopropanol, acetone, propylene oxide, etc. Its production processes include propane dehydrogenation, catalytic cracking of naphtha, catalytic cracking in refineries, coal-to-olefins, methanol-to-hydrocarbons, DCC heavy oil cracking, etc. Among them, propane dehydrogenation has the characteristics of using a single raw material, being cheap and easily available, having a simple dehydrogenation process flow, and being environmentally friendly, so it is widely used in industry.

[0003] In the preparation of propylene by propane dehydrogenation (PDH), the catalyst is the key to affecting propane conversion and propylene selectivity. The direct dehydrogenation of propane to propylene is carried out in a high-temperature environment, and the catalyst is prone to deactivation, so there are relatively high requirements for the structural stability of the catalyst. The reasons for the deactivation of the dehydrogenation catalyst include the sintering of metals in the catalyst or the reduction of metal oxides, resulting in a change in the structure of the active sites and loss of activity, as well as coke deposition blocking pores or covering the active sites.

[0004] On the one hand, doping with promoters to form a bimetallic alloy can effectively improve the anti-coking ability of the catalyst, thereby improving the catalyst life and performance. On the other hand, poisoning the easily coking sites and eliminating the acidic sites of the carrier can also improve the anti-coking performance of the catalyst.

[0005] For example, Chinese Patent Application No. CN108786801A discloses a Pt-based dehydrogenation catalyst with a composite oxide composed of gallium-modified silica and activated alumina as the carrier, platinum as the main active component, and one or more of potassium, magnesium, tin, and cerium as the co-active components. Its high-temperature stability is significantly improved. This catalyst uses a Pt nanoparticle sol as an impregnating solution to impregnate a composite oxide carrier composed of gallium-modified silica and activated alumina to reduce the accumulation of Pt at high temperatures and achieve the uniform distribution of Pt on the composite oxide carrier. The preparation process is relatively complex; in addition, its propane conversion and propylene selectivity still need to be improved.

[0006] Therefore, improving the stability of existing SiO2 / Al2O3-based catalyst carriers and Pt-based catalysts and developing new alternative propane dehydrogenation catalysts are the key to improving the propane dehydrogenation process. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a propane dehydrogenation catalyst and a preparation method thereof. By combining specific promoter active components with the main active component Pt, the interaction of each active component results in a more uniform dispersion on the carrier, significantly improving the anti-coking ability of the catalyst, fully exerting the catalytic activity of each component, and endowing the catalyst with more excellent catalytic activity and cyclic performance.

[0008] The technical solution of the present invention is as follows: The present invention provides a propane dehydrogenation catalyst, comprising an active component and a carrier; the active component is composed of the following components by mass percentage: 0.1-0.5% of the main active component Pt, 0.1-0.5% of the first promoter active component X, and 0.04-0.08% of the second promoter active component Y; the carrier is a Sn-SiO2 / Al2O3 composite oxide; the first promoter active component X is one or more of K, Na, Mg, Ca, Sr, and Ba; the second promoter active component Y is one or more of Fe, Co, Ni, Zn, Ru, Rh, Pd, and Ir.

[0009] In the present invention, the source of the main active component Pt element can be a water-soluble Pt-containing compound, including but not limited to chloroplatinic acid, platinum nitrate, and ammonium platinum nitrate. The source of the first promoter active component X can be an oxide, chloride, hydroxide, sulfate, or nitrate of X. The source of the second promoter active component Y can be a chloride, chlorate, oxyacid, or ammonium oxyacid salt of Y.

[0010] In the present invention, when the promoter active components simultaneously contain alkali metals / alkaline earth metals and transition metals, the catalyst exhibits better catalytic activity and cyclic performance, that is, alkali metals or alkaline earth metals and transition metals have a significant synergistic effect in improving the catalytic activity of Pt-based catalysts.

[0011] Preferably, the first promoter active component is K and Ba.

[0012] More preferably, the mass ratio of the first promoter active component K and Ba is 1:0.5-3.

[0013] Preferably, the mass ratio of the first promoter active component X to the second promoter active component Y is ≥5:1.

[0014] In some specific embodiments of the present invention, the carrier Sn-SiO2 / Al2O3 composite oxide is prepared by the following method: taking a silicon source and adding water to obtain silica sol; taking an aluminum source and adding nitric acid solution to obtain aluminum sol; mixing the silica sol, aluminum sol, template agent, and tin chloride solution, followed by shaping, drying, and calcination to obtain the product.

[0015] Those skilled in the art should understand that the above is only one of the preparation methods of the carrier Sn-SiO2 / Al2O3 composite oxide of the present invention. The technical effects of the present invention can be achieved by preparing Sn-SiO2 / Al2O3 composite oxide using conventional methods in the art.

[0016] In some more specific embodiments of the present invention, the raw material aluminum source includes but is not limited to: one or more of aluminum hydroxide, pseudo-boehmite, hydrated alumina, aluminum sulfate, sodium meta-aluminate, aluminum chloride, and aluminum nitrate.

[0017] In some more specific embodiments of the present invention, the silicon source includes but is not limited to one or more of silicon dioxide and water glass.

[0018] In some more specific embodiments of the present invention, the template agent is selected from hexamethylenetetramine.

[0019] In some more specific embodiments of the present invention, the mass ratio of the aluminum source, silicon source, template agent, and tin chloride is 1-2:0.015-0.2:0.15-0.5:0.005-0.025.

[0020] Preferably, the mass percentage of Sn in the Sn-SiO2 / Al2O3 composite oxide is 0.3-0.6%.

[0021] More preferably, the specific surface area of the Sn-SiO2 / Al2O3 composite oxide is 120-150m 2 / g.

[0022] The present invention also provides a preparation method of the propane dehydrogenation catalyst described in any one of the above, and the specific steps are as follows: (1) Prepare Sn-SiO2 / Al2O3 composite oxide; (2) Dissolve chloroplatinic acid and a compound containing the second co-active component Y in water to obtain solution 1; (3) Dissolve the compound containing the first co-active component X in water to obtain solution 2; (4) Add the Sn-SiO2 / Al2O3 composite oxide to solution 1 and solution 2 in sequence for the first impregnation and the second impregnation, and then obtain the propane dehydrogenation catalyst through drying and calcination.

[0023] Furthermore, the time of the first impregnation is 4-8h.

[0024] Furthermore, the time of the second impregnation is 2-5h.

[0025] Furthermore, the drying temperature is 80-120°C, and the drying time is 4-6h.

[0026] Further, the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 5 h.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) In the present invention, through the mutual cooperation of the main active ingredient Pt and each co-active ingredient (alkali metal, alkaline earth metal, and transition metal), the improvement of the catalyst performance (including propane conversion rate and propane selectivity) is achieved; among them, the synergistic cooperation of the alkali metal or alkaline earth metal and the transition metal can improve the anti-coking ability of the catalyst and enhance the catalyst cycle performance (high-temperature stability); (2) By using the Sn-SiO2 / Al2O3 composite oxide as the carrier and further regulating the Sn loading amount and specific surface area of the carrier, the catalyst strength is improved. At the same time, an appropriate amount of Sn can more effectively neutralize strong acid sites, avoid coke deposition on the carrier surface, and also lay a foundation for improving the catalyst stability; (3) Further through dosage optimization, that is, within a reasonable dosage range of each active ingredient, a better dispersion effect is achieved. The higher the dispersion of the active species, the better the catalytic performance of the catalyst, thereby further improving the propane conversion rate and propylene selectivity; (4) The present invention also finds that by optimizing the proportion of each component in the main active ingredient and the co-active ingredient, the propane conversion rate of the propane dehydrogenation catalyst can be effectively improved; (5) The catalyst preparation process of the present invention is simple, the preparation temperature is low, it is safer, and it is more suitable for large-scale industrial production. Specific Embodiments

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Unless otherwise specified, the raw materials and reagents used in the present invention are all from common commercial sources.

[0029] Preparation Example 1: [[ID=2II]] (1) Add silicon dioxide to water to make a silica sol with a mass fraction of 20%; (2) According to a mass ratio of 1:1, add aluminum hydroxide and pseudo-boehmite to a 5% nitric acid solution by mass to make an aluminum sol with a mass fraction of 20%; (3) Take 100 g of aluminum sol, add 3 g of hexamethylenetetramine, 0.1 g of tin chloride, and 3 g of silica sol, and stir at 300 rpm for 60 min to obtain a slurry; (4) The slurry was dropped into a hot oil column with a needle, and after curing, a wet carrier ball was formed. It was dried at 110 °C for 4 h and calcined at 700 °C for 5 h to obtain the carrier A (Sn - SiO₂ / Al₂O₃ - 1). Among them, the specific surface area of carrier A was 145 m 2 / g; the average pore diameter was 18.794 nm.

[0030] Preparation Example 2: The difference from Preparation Example 1 was only that in step (4), the drying temperature was 150 °C and the calcination temperature was 900 °C, to obtain carrier B (Sn - SiO₂ / Al₂O₃ - 2). Among them, the specific surface area of carrier B was 122 m 2 / g; the average pore diameter was 22.010 nm.

[0031] Preparation Example 3: The difference from Preparation Example 1 was only that in step (4), the drying temperature was 100 °C and the calcination temperature was 500 °C, to obtain carrier C (Sn - SiO₂ / Al₂O₃ - 3). Among them, the specific surface area of carrier C was 168 m 2 / g; the average pore diameter was 13.125 nm.

[0032] Preparation Example 4: The difference from Preparation Example 1 was only that: tin chloride in step (3) was replaced with an equal mass of gallium chloride to obtain carrier D (Ga - SiO₂ / Al₂O₃). Among them, the specific surface area of carrier D was 138 m 2 / g; the average pore diameter was 21.055 nm.

[0033] Preparation Example 5: (1) Silicon dioxide was added to water to make a silica sol with a mass fraction of 20%; (2) Aluminum hydroxide and pseudo - boehmite were added to a 5% nitric acid solution according to a mass ratio of 1:1 to make an aluminum sol with a mass fraction of 20%; (3) 100 g of aluminum sol and 3 g of silica sol were stirred at 300 rpm for 60 min to obtain a slurry; (4) The slurry was dropped into a hot oil column with a needle, and after curing, a wet carrier ball was formed. It was dried at 110 °C for 4 h and calcined at 700 °C for 5 h to obtain the carrier E (SiO₂ / Al₂O₃). Among them, the specific surface area of carrier E was 150 m[[ID=!]] 2 / g; the average pore diameter was 17.523 nm.

[0034] Among them, for the test of the specific surface area of the carrier, a JW-TB series specific surface area and pore size analyzer produced by Beijing Jingwei Gaobo Science and Technology Co., Ltd. was used to analyze the pore structure and specific surface area parameters of the catalyst. Before the sample determination, vacuum degassing was carried out at 350 °C for 4 h. The BET method was used to calculate the specific surface area of the sample, the BJH model was used to calculate the pore volume, and the DFT method was used to analyze the pore size distribution.

[0035] Examples 1-10 The sources, compositions and dosages of the carrier, the main active ingredient Pt, the first co-active ingredient X, and the second co-active ingredient Y used in Examples 1-10 are shown in Table 1.

[0036] Table 1 Catalyst raw material formula of Examples 1-10

[0037] The preparation method is as follows: (1) Dissolve H2PtCl6·6H2O and the compound containing the second co-active ingredient Y in water to obtain Solution 1; (2) Dissolve the compound containing the first co-active ingredient X in water to obtain Solution 2; (3) Add the carrier to Solution 1 in sequence for the first impregnation, with an impregnation time of 5 h, then vacuum dry at 120 °C for 4 h, and then calcine at 500 °C for 3 h; then add it to Solution 2 for the second impregnation, with an impregnation time of 3 h, then vacuum dry at 120 °C for 4 h, and then calcine at 500 °C for 3 h to obtain the corresponding propane dehydrogenation catalyst.

[0038] Example 11 The sources, compositions and dosages of the carrier, the main active ingredient Pt, the first co-active ingredient X, and the second co-active ingredient Y used in this example are the same as those in Example 6. The preparation method is as follows: (1) Dissolve H2PtCl6·6H2O and the compound containing the first co-active ingredient X in water to obtain Solution 1; (2) Dissolve the compound containing the second co-active ingredient Y in water to obtain Solution 2; (3) Add the carrier to Solution 1 in sequence for the first impregnation, with an impregnation time of 5 h, then vacuum dry at 120 °C for 4 h, and then calcine at 500 °C for 3 h; then add it to Solution 2 for the second impregnation, with an impregnation time of 3 h, then vacuum dry at 120 °C for 4 h, and then calcine at 500 °C for 3 h to obtain the propane dehydrogenation catalyst.

[0039] Example 12 The sources, compositions and dosages of the carrier, the main active ingredient Pt, the first co-active ingredient X, and the second co-active ingredient Y used in this example are the same as those in Example 6. The preparation method is as follows: (1) Dissolve H2PtCl6·6H2O, the compound containing the first co-active ingredient X, and the compound containing the second co-active ingredient Y in water to obtain a solution; (2) Add the carrier to the solution in sequence for a single impregnation for 5 h, then vacuum dry at 120 °C for 4 h, and then calcine at 500 °C for 3 h to obtain a propane dehydrogenation catalyst.

[0040] Application Example Catalytic performance detection: The propane dehydrogenation to propylene reaction is carried out in a fixed-bed reactor. The reaction temperature is 600 °C, the reaction pressure is atmospheric pressure, and the reaction gas composition is: propane / hydrogen = 1:1 (V / V); the space velocity is 1500 h -1 , and the loading amount of the propane dehydrogenation catalyst is 5 g. Pass the reaction gas into the reactor loaded with the above catalyst for reaction for 5 h to obtain the product, and analyze the product with a GC 7900 gas chromatograph. The catalytic performance results of the propane dehydrogenation reaction using the propane dehydrogenation catalysts prepared in Examples 1-12 are shown in Table 2.

[0041] Table 2 Catalytic performance characterization results of the catalysts in Examples 1-12

[0042] As can be seen from Table 2, the catalysts prepared in Examples 1-12 of the present invention all have high propane conversion and propylene selectivity. At the same time, after continuous reaction for 36 h, the propane change rate decreases by no more than 2%, and the propylene selectivity decreases by no more than 0.7%, showing high stability.

[0043] In addition, as can be seen from Examples 1, 2 and 5, there is a certain synergistic effect between K and Na in the first co-active ingredient in improving stability. From the comparison of Examples 5 and 6, it can be seen that when at least two components are selected for the second co-active ingredient, the propane conversion, propylene selectivity and stability can all be further improved.

[0044] From the comparison of Examples 2-4, it can be seen that the catalytic effect of the catalyst of the present invention is affected by the specific surface area of the carrier. The larger the specific surface area of the carrier, the better the catalytic effect. However, when the specific surface area of the carrier exceeds 130 m 2 / g, the corresponding average pore diameter is less than 22 nm, and the catalytic effect decreases. This may be due to the relatively small internal pore diameter of the carrier, which is not conducive to the adsorption of reaction gases and the desorption of products.

[0045] In Examples 6, 9, and 10, the X / Y ratios are 5:1, 3:1, and 11:1 respectively. The catalytic effect of Example 9 decreases. It can be seen that too little amount of the co-active ingredient X (too much amount of Y) will also lead to a decrease in the catalytic effect of the catalyst. Therefore, the X / Y ratio is preferably 5:1 or more.

[0046] Finally, when preparing the catalyst by the impregnation method in Example 11, different addition sequences of the impregnation solution were used, and in Example 12, one-time impregnation was adopted. Compared with Example 6, the propane conversion rate and propylene selectivity of the obtained catalyst decreased when reacting for 6 hours, and the propane conversion rate further decreased after 36 hours. Therefore, it is preferred to use two-time impregnation, and more preferably to impregnate Pt and the second co-active component Y once, and the first co-active component X twice.

[0047] Comparative Examples 1-6 The sources, compositions and dosages of the carriers, main active component Pt, first co-active component X and second co-active component Y used in Comparative Examples 1-6 are shown in Table 3.

[0048] Table 3 Catalyst raw material formulas of Example 6 and Comparative Examples 1-6

[0049] The preparation method is the same as that of Examples 1-10.

[0050] The catalytic performance results of propane dehydrogenation reaction using the propane dehydrogenation catalysts prepared in Comparative Examples 1-6 are shown in Table 4.

[0051] Table 4 Characterization results of catalytic performance of the catalysts of Example 6 and Comparative Examples 1-6

[0052] It can be seen from Table 4 that: compared with Example 6, when the dosages of the co-active components X and Y in Comparative Examples 1 and 2 exceed a certain range, they both have a greater impact on the catalytic activity of the catalyst. That is, when the X / Y ratio is too low, or in other words, when the dosage of the transition metal is too high (Comparative Example 2), the initial catalytic effect is poor, and the propane conversion rate further decreases after 36 hours.

[0053] Compared with Example 6, Comparative Examples 3 and 4 have only a single co-active component X or Y. Not only is the initial catalytic effect poor, but the decline is also large after continuous reaction for 36 hours. It can be seen that the first co-active component X and the second co-active component Y show a significant synergistic effect in improving both the catalytic effect and stability of the catalyst.

[0054] In addition, in Comparative Example 5, Ga-SiO2 / Al2O3 composite oxide was used as the carrier. Although the initial propane conversion rate and propylene selectivity were high, as the reaction proceeded, the catalyst stability became poor, and both the propane conversion rate and propylene selectivity decreased to a large extent. Although Sn also exists in the catalyst of Comparative Example 6, its introduction method is different. Not only is the propane conversion rate greatly reduced, but the hardness of the catalyst itself is also poor, which leads to a decrease in stability, and the propane conversion rate decreases significantly as the reaction proceeds.

[0055] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Any simple modification or equivalent replacement made by those of ordinary skill in the art to the technical solution of the present invention shall not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A propane dehydrogenation catalyst, characterized in that, It includes an active ingredient and a carrier; based on 100% of the carrier mass, the active ingredient consists of the following components: 0.1 - 0.5% of the main active ingredient Pt, 0.1 - 0.5% of the first co-active ingredient X, and 0.04 - 0.08% of the second co-active ingredient Y; the carrier is a Sn-SiO2 / Al2O3 composite oxide; The first co-active ingredient X is K and / or Ba; the second co-active ingredient Y is one or more of Fe, Co, Ni, Ru, Pd, and Ir.

2. The propane dehydrogenation catalyst according to claim 1, wherein, The first co-active ingredient is K and Ba.

3. The propane dehydrogenation catalyst according to claim 2, wherein The mass ratio of K to Ba in the first co-active ingredient is 1:0.5 - 3.

4. The propane dehydrogenation catalyst according to claim 1, wherein The mass ratio of the first co-active ingredient X to the second co-active ingredient Y is ≥5:

1.

5. The propane dehydrogenation catalyst according to claim 1, characterized in that, The Sn-SiO2 / Al2O3 composite oxide is prepared by the following method: Take a silicon source and add water to obtain a silica sol; take an aluminum source and add it to a nitric acid solution to obtain an aluminum sol; mix the silica sol, aluminum sol, template agent, and tin chloride solution, and then carry out shaping, drying, and calcination to obtain it.

6. The propane dehydrogenation catalyst according to claim 1, wherein The mass percentage of Sn in the Sn-SiO2 / Al2O3 composite oxide is 0.3 - 0.6%.

7. The propane dehydrogenation catalyst according to claim 1, wherein The specific surface area of the Sn-SiO2 / Al2O3 composite oxide is 120-150 m 2 / g.

8. The preparation method of the propane dehydrogenation catalyst according to any one of claims 1-7, characterized in that, The specific steps are as follows: (1) Prepare the Sn-SiO2 / Al2O3 composite oxide; (2) Dissolve chloroplatinic acid and a compound containing the second co-active ingredient Y in water to obtain Solution 1; (3) Dissolve a compound containing the first co-active ingredient X in water to obtain Solution 2; (4) Add the Sn-SiO2 / Al2O3 composite oxide to Solution 1 and Solution 2 in sequence for the first impregnation and the second impregnation, and then carry out drying and calcination to obtain the propane dehydrogenation catalyst.

9. The preparation method according to claim 8, wherein, In step (4), the time for the first impregnation is 4 - 8 h; and / or the time for the second impregnation is 2 - 5 h.

10. The preparation method according to claim 8, characterized in that, In step (4), the drying temperature is 80 - 120 °C, and the drying time is 4 - 6 h; and / or the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 5 h.

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