A propane dehydrogenation catalyst and a method for preparing the same

Abstract

The application belongs to the technical field of petroleum chemical 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 consists of the following components in percentage by mass: a main active component Pt 0.1-0.5%, a first auxiliary active component X 0.1-0.5%, and a second auxiliary active component Y 0.04-0.08%;the carrier is a Sn-SiO2 / Al2O3 composite oxide;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 has 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 application belongs to the technical field of petrochemical catalysts, and particularly relates to a propane dehydrogenation catalyst and a preparation method thereof. BACKGROUND

[0002] Propylene is a basic raw material for three synthetic materials, and is mainly used for producing polypropylene, acrylonitrile, isopropyl alcohol, acetone and propylene oxide, etc. Its production processes include propane dehydrogenation, catalytic cracking of naphtha, catalytic cracking of oil refinery, coal-to-olefins, methanol-to-hydrocarbons, DCC heavy oil cracking, etc. Among them, propane dehydrogenation has the characteristics of single raw material, low cost, simple dehydrogenation process, environmental protection, etc., and is widely used in industry.

[0003] In the preparation of propylene by propane dehydrogenation (PDH), the catalyst is the key to affect the propane conversion rate and the selectivity of propylene. The direct dehydrogenation of propane to propylene is carried out in a high-temperature environment, and the catalyst is easy to be deactivated, so the catalyst has a high requirement for structural stability. The reasons for the deactivation of the dehydrogenation catalyst include sintering of the metal in the catalyst or reduction of the metal oxide, which causes the structure of the active site to change and lose activity, and coke deposition to block the voids or cover the active sites.

[0004] On the one hand, the doping of the auxiliary agent to form a bimetallic alloy can effectively improve the anti-coking ability of the catalyst, thereby improving the service life and performance of the catalyst. On the other hand, the poisoning of the easy-coking sites and the elimination of the acid 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 silicon dioxide and active alumina as a carrier, platinum as a main active component, and one or more of potassium, magnesium, tin and cerium as an auxiliary active component. The high-temperature stability of the catalyst is significantly improved. The catalyst is prepared by impregnating a composite oxide carrier composed of gallium-modified silicon dioxide and active alumina with a Pt nanoparticle sol as an impregnation liquid to reduce the accumulation of Pt at high temperatures, and to realize the uniform distribution of Pt on the composite oxide carrier. The preparation process is relatively complex. In addition, the propane conversion rate and the propylene selectivity still need to be improved.

[0006] Therefore, improving the stability of the existing SiO2 / Al2O3-based catalyst carrier and Pt-based catalyst, and developing a new alternative propane dehydrogenation catalyst are the keys to improving the propane dehydrogenation process. SUMMARY

[0007] In view of the problems in the prior art, the present application provides a propane dehydrogenation catalyst and a preparation method thereof, by combining specific active component combinations with the main active component Pt, the dispersion of each active component on the carrier is more uniform after interaction, the coking resistance of the catalyst is significantly improved, the catalytic activity of each component is fully utilized, and the catalyst is endowed with more excellent catalytic activity and cycle performance.

[0008] The technical scheme of the present application is as follows:

[0009] The present application provides a propane dehydrogenation catalyst, comprising an active component and a carrier; the active component consists of the following components in percentage by mass: main active component Pt 0.1-0.5%, first active component X 0.1-0.5%, second active component Y 0.04-0.08%; the carrier is Sn-SiO2 / Al2O3 composite oxide; the first active component X is one or more of K, Na, Mg, Ca, Sr and Ba; the second active component Y is one or more of Fe, Co, Ni, Zn, Ru, Rh, Pd and Ir.

[0010] In the present application, the source of the main active component Pt element can use water-soluble Pt-containing compounds, including but not limited to chloroplatinic acid, platinum nitrate, and platinum nitrate ammonia. The source of the first active component X can use oxides, chlorides, hydroxides, sulfates and nitrates of X. The source of the second active component Y can use chlorides, chlorates, oxo acids or oxo acid ammonium salts of Y.

[0011] In the present application, when the active component simultaneously contains alkali metal / alkaline earth metal and transition metal, the catalyst exhibits more excellent catalytic activity and cycle performance, that is, the alkali metal or alkaline earth metal and the transition metal have a significant synergistic effect on improving the catalytic activity of the Pt-based catalyst.

[0012] Preferably, the first active component is K and Ba.

[0013] More preferably, the mass ratio of K and Ba in the first active component is 1:0.5-3.

[0014] Preferably, the mass ratio of the first active component X to the second active component Y is ≥5:1.

[0015] In some specific embodiments of the present application, the carrier Sn-SiO2 / Al2O3 composite oxide is prepared by the following method: taking a silicon source and adding water to obtain a silica sol; taking an aluminum source and adding a nitric acid solution to obtain an aluminum sol; mixing the silica sol, the aluminum sol, a template agent and a tin chloride solution, and then forming, drying and calcining to obtain the carrier.

[0016] 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 application. The technical effects of the present application can be achieved by using Sn-SiO2 / Al2O3 composite oxides prepared by conventional methods in the art.

[0017] In some more specific embodiments of the present application, the aluminum source used includes but is not limited to one or more of aluminum hydroxide, pseudoboehmite, hydrated aluminum oxide, aluminum sulfate, sodium metaaluminate, aluminum chloride and aluminum nitrate.

[0018] In some more specific embodiments of the present application, the silicon source includes but is not limited to one or more of silicon dioxide and water glass.

[0019] In some more specific embodiments of the present application, the template agent is selected from hexamethylenetetramine.

[0020] In some more specific embodiments of the present application, the mass ratio of the aluminum source, the silicon source, the template agent and the tin chloride is 1-2:0.015-0.2:0.15-0.5:0.005-0.025.

[0021] Preferably, the mass percentage of Sn contained in the Sn-SiO2 / Al2O3 composite oxide is 0.3-0.6%.

[0022] More preferably, the specific surface area of the Sn-SiO2 / Al2O3 composite oxide is 120-150m 2 / g.

[0023] The present application also provides a preparation method of the propane dehydrogenation catalyst as described above, and the specific steps are as follows:

[0024] (1) preparing a Sn-SiO2 / Al2O3 composite oxide;

[0025] (2) dissolving chloroplatinic acid and a compound containing a second promoter component Y in water to obtain solution 1;

[0026] (3) dissolving a compound containing a first promoter component X in water to obtain solution 2;

[0027] (4) sequentially adding the Sn-SiO2 / Al2O3 composite oxide to solution 1 and solution 2 for primary impregnation and secondary impregnation, and then drying and calcining to obtain the propane dehydrogenation catalyst.

[0028] Further, the time for the primary impregnation is 4-8h.

[0029] Further, the time for the secondary impregnation is 2-5h.

[0030] Further, the drying temperature is 80-120℃, and the drying time is 4-6h.

[0031] Further, the calcination temperature is 400-600℃, and the calcination time is 2-5h.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The present application realizes the improvement of catalyst performance (including propane conversion rate and propane selectivity) through the mutual cooperation of the main active component Pt and each auxiliary active component (alkali metal, alkaline earth metal, and transition metal); the cooperation of the alkali metal or alkaline earth metal and the transition metal can improve the catalyst anti-coking ability and improve the catalyst cycle performance (high-temperature stability);

[0034] (2) Through the use of Sn-SiO2 / Al2O3 composite oxide as the carrier, and further through the regulation of the carrier Sn loading amount and specific surface area, the catalyst strength is improved, and at the same time, the appropriate Sn can more effectively neutralize the strong acid sites, avoid the deposition of coke on the carrier surface, and lay a foundation for the improvement of catalyst stability;

[0035] (3) Further through the optimization of the amount, that is, each active component is in a reasonable amount range, a more optimal dispersion effect is realized, the higher the activity species dispersion, the better the catalyst performance, thereby further improving the propane conversion rate and the propylene selectivity;

[0036] (4) The present application also finds that through the optimization of the proportioning of each component in the main active component and the auxiliary active component, the propane conversion rate of the propane dehydrogenation catalyst can also be effectively improved;

[0037] (5) The catalyst preparation process of the present application is simple, the preparation temperature is low, it is safer, and it is more suitable for large-scale production in industry. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. Unless otherwise specified, the raw materials and reagents used in the present application are commercially available.

[0039] Preparation Example 1:

[0040] (1) The silica was added to water to prepare a silica sol with a mass fraction of 20%;

[0041] (2) Aluminum hydroxide and pseudo-boehmite were added into 5% nitric acid solution with a mass ratio of 1:1 to prepare an aluminum sol with a mass fraction of 20%;

[0042] (3) 100 g of the aluminum sol was taken, 3 g of hexamethylenetetramine, 0.1 g of tin chloride and 3 g of silica sol were added, and stirring was performed at 300 rpm for 60 min to obtain a slurry;

[0043] (4) The slurry was dripped into a hot oil column with a needle, and a carrier wet ball was formed after solidification, which 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). The specific surface area of the carrier A was 145 m 2 / g, and the average pore size was 18.794 nm.

[0044] Preparation Example 2:

[0045] The difference from Preparation Example 1 was that, in step (4), the drying temperature was 150°C, and the calcination temperature was 900°C, and carrier B (Sn-SiO2 / Al2O3-2) was prepared. The specific surface area of the carrier B was 122 m 2 / g, and the average pore size was 22.010 nm.

[0046] Preparation Example 3:

[0047] The difference from Preparation Example 1 was that, in step (4), the drying temperature was 100°C, and the calcination temperature was 500°C, and carrier C (Sn-SiO2 / Al2O3-3) was prepared. The specific surface area of the carrier C was 168 m 2 / g, and the average pore size was 13.125 nm.

[0048] Preparation Example 4:

[0049] The difference from Preparation Example 1 was that, in step (3), tin chloride was replaced by an equal amount of gallium chloride, and carrier D (Ga-SiO2 / Al2O3) was prepared. The specific surface area of the carrier D was 138 m 2 / g, and the average pore size was 21.055 nm.

[0050] Preparation Example 5:

[0051] (1) Silica was added into water to prepare a silica sol with a mass fraction of 20%;

[0052] (2) Aluminum hydroxide and pseudo-boehmite were added into 5% nitric acid solution with a mass ratio of 1:1 to prepare an aluminum sol with a mass fraction of 20%;

[0053] (3) 100 g of the aluminum sol and 3 g of silica sol were taken, and stirring was performed at 300 rpm for 60 min to obtain a slurry;

[0054] (4) The slurry is dripped into a hot oil column with a needle, and a carrier wet ball is formed after solidification, dried at 110°C for 4h, and calcined at 700°C for 5h to obtain the carrier E (SiO2 / Al2O3). The specific surface area of the carrier E is 150m2 / g, and the average pore size is 17.523nm. 2

[0055] The specific surface area of the carrier is tested by a JW-TB series specific surface and pore size analyzer produced by Beijing Jeol Highborn Science and Technology Co., Ltd. to analyze the pore structure and specific surface area parameters of the catalyst. The sample is vacuum degassed at 350°C for 4h before determination, the specific surface area of the sample is calculated by the BET method, the pore volume is calculated by the BJH model, and the pore size distribution is analyzed by the DFT method.

[0056] Examples 1-10

[0057] The sources, compositions and amounts of the carrier, the main active ingredient Pt, the first auxiliary active ingredient X and the second auxiliary active ingredient Y used in Examples 1-10 are shown in Table 1.

[0058] Table 1 Catalyst raw material formula of Examples 1-10

[0059]

[0060] The preparation method is as follows:

[0061] (1) H2PtCl6·6H2O and a compound containing the second auxiliary active ingredient Y are dissolved in water to obtain solution 1;

[0062] (2) A compound containing the first auxiliary active ingredient X is dissolved in water to obtain solution 2;

[0063] (3) The carrier is added to solution 1 for primary impregnation, the impregnation time is 5h, then vacuum dried at 120°C for 4h, and calcined at 500°C for 3h; then added to solution 2 for secondary impregnation, the impregnation time is 3h, then vacuum dried at 120°C for 4h, and calcined at 500°C for 3h to obtain the corresponding propane dehydrogenation catalyst.

[0064] Example 11

[0065] The sources, compositions and amounts of the carrier, the main active ingredient Pt, the first auxiliary active ingredient X and the second auxiliary active ingredient Y used in this example are the same as in Example 6, and the preparation method is as follows:

[0066] (1) H2PtCl6·6H2O and a compound containing the first auxiliary active ingredient X are dissolved in water to obtain solution 1;

[0067] ​(2) dissolving the compound containing the second promoter Y in water to obtain solution 2;

[0068] (3) adding the carrier into solution 1 to perform one-time impregnation, the impregnation time is 5 h, then vacuum drying at 120℃ for 4 h, and calcining at 500℃ for 3 h; then adding solution 2 to perform two-time impregnation, the impregnation time is 3 h, then vacuum drying at 120℃ for 4 h, and calcining at 500℃ for 3 h, to obtain the propane dehydrogenation catalyst.

[0069] Example 12

[0070] The source, composition and amount of the carrier, the main active component Pt, the first promoter X and the second promoter Y used in this example are the same as those in Example 6, and the preparation method is as follows:

[0071] (1) dissolving H2PtCl6·6H2O, the compound containing the first promoter X and the compound containing the second promoter Y in water to obtain a solution;

[0072] (2) adding the carrier into the solution to perform one-time impregnation, the impregnation time is 5 h, then vacuum drying at 120℃ for 4 h, and calcining at 500℃ for 3 h, to obtain the propane dehydrogenation catalyst.

[0073] Application Example

[0074] Catalytic performance detection: the propane dehydrogenation reaction to prepare propylene is carried out in a fixed bed reactor, the reaction temperature is 600℃, the reaction pressure is normal pressure, the reaction gas composition is: propane / hydrogen = 1:1 (V / V); the space velocity is 1500h-1, and the loading amount of the propane dehydrogenation catalyst is 5 g. The reaction gas is introduced into the reactor loaded with the above-mentioned catalyst to react for 5 h to prepare a product, and the product is analyzed by using a GC 7900 gas chromatograph. The catalytic performance results of the propane dehydrogenation reaction using the propane dehydrogenation catalyst prepared in Examples 1-12 are shown in Table 2. -1

[0075] Table 2: Catalytic performance characterization results of the catalysts of Examples 1-12

[0076]

[0077] As can be seen from Table 2, the catalysts prepared in Examples 1-12 of the present application all have high propane conversion rate and propylene selectivity, and the propane conversion rate decreases by not more than 2% and the propylene selectivity decreases by not more than 0.7% after 36 h of continuous reaction, and the stability is high.

[0078] ​In addition, from Examples 1, 2 and 5, it can be seen that K and Na in the first co-activating component have a certain synergistic effect on improving stability, and from the comparison of Examples 5 and 6, it can be seen that when at least two components are selected as the second co-activating component, the propane conversion rate, propylene selectivity and stability can be further improved.

[0079] From the comparison of Examples 2-4, it can be seen that the catalytic effect of the catalyst of the present application is affected by the specific surface area of the carrier, the larger the specific surface area of the carrier, the better the catalytic effect, but 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, which may be due to the fact that the internal pore diameter of the carrier is too small, which is not conducive to the adsorption of reaction gas and the desorption of product.

[0080] In Examples 6, 9 and 10, the X / Y ratio is 5:1, 3:1 and 11:1 respectively, and the catalytic effect of Example 9 decreases, which shows that too little amount of the co-activating component X (too much amount of Y) will also lead to the decrease of the catalytic effect of the catalyst, therefore, the X / Y ratio is preferably 5:1 or more.

[0081] Finally, in Example 11, the catalyst is prepared by impregnation method, and the order of adding the impregnation solution is different, and in Example 12, one-time impregnation is adopted, and compared with Example 6, the propane conversion rate and propylene selectivity of the catalyst obtained by the above methods decrease after 6 hours of reaction, and the propane conversion rate further decreases after 36 hours, therefore, it is preferred to adopt two-time impregnation, and it is further preferred to adopt one-time impregnation of Pt and the second co-activating component Y, and two-time impregnation of the first co-activating component X.

[0082] Comparative Examples 1-6

[0083] The source, composition and amount of the carrier, the main active component Pt, the first co-activating component X and the second co-activating component Y used in Comparative Examples 1-6 are shown in Table 3.

[0084] Table 3 Raw material formula of the catalyst of Example 6 and Comparative Examples 1-6

[0085]

[0086] The preparation method is the same as that of Examples 1-10.

[0087] The catalytic performance results of the propane dehydrogenation catalyst prepared by Comparative Examples 1-6 in the propane dehydrogenation reaction are shown in Table 4.

[0088] Table 4 Catalytic performance characterization results of the catalyst of Example 6 and Comparative Examples 1-6

[0089]

[0090] As can be seen from Table 4, compared with Example 6, the catalytic activity of the catalysts in Comparative Examples 1 and 2 is greatly affected when the amounts of the co-activating components X and Y exceed a certain range, i.e. when the X / Y ratio is too low or the amount of transition metal is too high (Comparative Example 2), the initial catalytic effect is poor and the propane conversion rate further decreases after 36 h.

[0091] Compared with Example 6, the catalysts in Comparative Examples 3 and 4 only have a single X or Y co-activating component, and not only is the initial catalytic effect poor, but the decrease in the catalytic effect after 36 h of continuous reaction is also large, which shows that the first co-activating component X and the second co-activating component Y have a significant synergistic effect in improving the catalytic effect and stability of the catalyst.

[0092] In addition, although the initial propane conversion rate and propylene selectivity are high in Comparative Example 5 in which Ga-SiO2 / Al2O3 composite oxides are used as the carrier, the stability of the catalyst is poor and the propane conversion rate and propylene selectivity both decrease to a large extent as the reaction proceeds. Although Sn is also present in the catalyst in Comparative Example 6, the introduction method is different, and not only does the propane conversion rate decrease greatly, but the hardness of the catalyst itself is also poor, which further leads to a decrease in stability and a significant decrease in the propane conversion rate as the reaction proceeds.

[0093] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A propane dehydrogenation catalyst characterized in that, The active ingredient consists of the following components: the main active ingredient Pt 0.1-0.5%, the first auxiliary active ingredient X 0.1-0.5%, and the second auxiliary active ingredient Y 0.04-0.08%, based on 100% by mass of the carrier; the carrier is a Sn-SiO2 / Al2O3 composite oxide; The first auxiliary active ingredient X is K and Ba; the mass ratio of K to Ba in the first auxiliary active ingredient is 1:0.5-3; the second auxiliary active ingredient Y is one or more of Fe, Co, Ni, Ru, Pd, and Ir; and the mass ratio of the first auxiliary active ingredient X to the second auxiliary active ingredient Y is ≥5:

1. The preparation method of the propane dehydrogenation catalyst is as follows: (1) preparing a Sn-SiO2 / Al2O3 composite oxide; (2) dissolving chloroplatinic acid and a compound containing the second auxiliary active ingredient Y in water to obtain solution 1; (3) dissolving a compound containing the first auxiliary active ingredient X in water to obtain solution 2; (4) sequentially adding the Sn-SiO2 / Al2O3 composite oxide to solution 1 and solution 2 for primary impregnation and secondary impregnation, and then drying and calcining to obtain the propane dehydrogenation catalyst.

2. The propane dehydrogenation catalyst of claim 1, wherein, The Sn-SiO2 / Al2O3 composite oxide is prepared by the following method: adding a silicon source to water to obtain a silica sol; adding an aluminum source to a nitric acid solution to obtain an alumina sol; mixing the silica sol, the alumina sol, a template agent, and a tin chloride solution, and then shaping, drying, and calcining to obtain the Sn-SiO2 / Al2O3 composite oxide.

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

4. The propane dehydrogenation catalyst of claim 1, wherein, The Sn-SiO2 / Al2O3 composite oxide has a specific surface area of 120-150 m 2 / g.

5. The process for preparing a propane dehydrogenation catalyst according to any one of claims 1 to 4, characterized in that, The specific steps are as follows: (1) preparing a Sn-SiO2 / Al2O3 composite oxide; (2) dissolving chloroplatinic acid and a compound containing the second auxiliary active ingredient Y in water to obtain solution 1; (3) dissolving a compound containing the first auxiliary active ingredient X in water to obtain solution 2; (4) sequentially adding the Sn-SiO2 / Al2O3 composite oxide to solution 1 and solution 2 for primary impregnation and secondary impregnation, and then drying and calcining to obtain the propane dehydrogenation catalyst.

6. The preparation method according to claim 5, characterized in that, In step (4), the time for the primary impregnation is 4-8 h; and / or the time for the secondary impregnation is 2-5 h.

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

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