A supported catalyst with low precious metal content, its preparation method and application

Abstract

This invention relates to the field of catalyst technology, providing a low-precious-metal-content supported catalyst, its preparation method, and its application. The low-precious-metal-content supported catalyst comprises: a) Pt or its oxide, b) W or its oxide, c) a Group IIA element or its oxide, d) an iron-based element or its oxide, and e) a support; the mass ratio of each component is a:b:c:d:e = (0.01–0.3):(0.01–3):(0.01–1):(0.01–3):(95–99). The low-precious-metal-content supported catalyst provided by this invention reduces the loading of the precious metal Pt, thereby lowering the catalyst cost; simultaneously, it maintains good performance in alkane dehydrogenation reactions, showing promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a low-noble-metal-content supported catalyst, its preparation method, and its application. Background Technology

[0002] Propylene, as an important petrochemical feedstock, has become the second most demanded chemical monomer after ethylene. Its main uses are in the production of polypropylene, acrylonitrile, isopropanol, and other chemical products. In recent years, the global demand for propylene has grown at a rate far exceeding that of ethylene. Therefore, the world may face a shortage of propylene resources in the future. Traditional methods for producing propylene involve co-production with ethylene and cracking processes involving naphtha and light diesel oil. Expanding production processes to increase propylene sources has become a key research focus in the petrochemical field. my country possesses abundant oil and natural gas resources, which contain large amounts of propane. However, these are generally used as fuel or vented, resulting in significant resource waste. How to convert large quantities of inexpensive propane into high-value-added propylene, which is in high demand in the market, through catalytic dehydrogenation has significant economic and social benefits. Therefore, methods for producing propylene from propane derived from petrochemical byproducts or natural gas through direct dehydrogenation processes have received considerable attention in recent years.

[0003] Propane dehydrogenation to propylene technologies that have been industrialized or successfully developed include UOP's Oleflex process, CB&I Lummus's Catofin process, Snamprogetti-Yarsintez's fluidized bed FBD process, Krupp-Uhde's steam-activated reforming STAR process, and Linde-BASF's PDH process. Currently, the most widely industrialized processes are UOP's Oleflex process (using a Pt / Al₂O₃ catalyst) and CB&I Lummus's Catofin process (using a Cr / Al₂O₃ catalyst). Both of these catalysts suffer severe deactivation due to carbon buildup, requiring catalyst regeneration. Furthermore, chromium is toxic and environmentally harmful, and platinum is expensive, severely limiting the development of propane dehydrogenation processes. Therefore, finding a cheap, low-toxicity propane dehydrogenation catalyst with high activity and stability is of great practical significance.

[0004] Reducing the Pt or Cr content in catalysts is an important direction for improving alkane dehydrogenation catalysts. However, current research mainly focuses on the optimization of Pt-based catalysts, with limited research on reducing the Pt content. The Pt content in catalysts is generally above 0.3 wt%. For example, US patents US3843560, US3903191, US3531544, US3647719, US4000210, US4046715, and US4133842 describe alkane dehydrogenation catalysts as Pt-Sn bimetallic systems, using alkali metals as acidity modifiers, with a Pt loading of approximately 0.5%.

[0005] Therefore, how to reduce the Pt content in alkane dehydrogenation catalysts while maintaining their catalytic performance is a technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a low-precious-metal-content supported catalyst, its preparation method, and its application, so as to solve the technical problem of high Pt content in existing alkane dehydrogenation catalysts.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a low-noble-metal-content supported catalyst, comprising: a) Pt or its oxide, b) W or its oxide, c) a Group IIA element or its oxide, d) an iron-based element or its oxide, and e) a support; the mass ratio of the components is a:b:c:d:e = (0.01~0.3):(0.01~3):(0.01~1):(0.01~3):(95~99).

[0009] The low-precious-metal-content supported catalyst provided by this invention uses Pt as the dehydrogenation active component, and strengthens the role of Pt with W, Group IIA elements and iron-based elements. This can reduce the Pt content in the catalyst and it has excellent catalytic activity in the dehydrogenation of alkane to olefins.

[0010] In this invention, the mass ratio of each component is calculated, with the mass of Pt or its oxide being calculated as the mass of Pt; the mass of Cr or its oxide being calculated as the mass of Cr; the mass of Ge or its oxide being calculated as the mass of Ge; and the mass of iron group elements or their oxides being calculated as the mass of iron group elements.

[0011] According to some embodiments of the present invention, the mass ratio of the components is a:b:c:d:e = (0.01~0.2):(0.1~2):(0.1~0.8):(0.1~2):(95~99).

[0012] According to some embodiments of the present invention, the mass ratio of the components is a:b:c:d:e = (0.05~0.2):(0.5~2):(0.1~0.8):(0.5~2):(95~99).

[0013] According to some embodiments of the present invention, the mass ratio of the components is a:b:c:d:e = (0.05~0.15):(1~2):(0.4~0.8):(0.5~2):(95~99).

[0014] According to some embodiments of the present invention, the surface area of ​​Pt accounts for 0.5% to 1.0% of the total surface area of ​​the catalyst.

[0015] In this invention, the surface area of ​​Pt refers to the area occupied by Pt on the surface of the catalyst.

[0016] According to some embodiments of the present invention, the support comprises a ZnAl2O4 composite oxide.

[0017] According to some embodiments of the present invention, the preparation method of the ZnAl2O4 composite oxide includes: preparing a solution containing a soluble salt of Zn and a soluble salt of Al, adding ammonia water dropwise under stirring until the pH value is 7-9, aging, filtration, drying, calcining, and obtaining the ZnAl2O4 composite oxide.

[0018] For catalysts used in the dehydrogenation of alkanes to olefins, many side reactions can occur at the acid sites on the catalyst support surface, such as alkane cracking and isomerization, and olefin cracking, isomerization, and polymerization. Compared to common single supports such as Al2O3, the catalyst provided in this invention uses the composite oxide ZnAl2O4 as the support, which is beneficial to improving the stability of the catalytic reaction.

[0019] According to some embodiments of the present invention, the group IIA element includes at least one of Mg, Ca, or Sr.

[0020] According to some embodiments of the present invention, the iron-group element includes at least one of Fe, Co, or Ni.

[0021] In a second aspect, the present invention provides a method for preparing the catalyst described in the first aspect, comprising: mixing a solution comprising a soluble salt of Pt, a soluble salt of W, a soluble salt of a Group IIA element and a soluble salt of an iron group element with a support, drying, and calcining to obtain the catalyst.

[0022] According to some embodiments of the present invention, the preparation method includes: first mixing a first solution comprising a soluble salt of a group IIA element with a support, followed by a first drying and a first calcination to obtain a catalyst precursor; then mixing a second solution comprising a soluble salt of Pt, a soluble salt of W, and a soluble salt of an iron group element with the catalyst precursor, followed by a second drying and a second calcination to obtain the catalyst.

[0023] According to some embodiments of the present invention, mixing the second solution with the catalyst precursor includes: spraying the second solution onto the surface of the catalyst precursor using a coating method.

[0024] Coating is generally used to coat pharmaceutical tablets and pills with sugar, organic films, and water-soluble films, and can be achieved using a coating machine. In this invention, a coating method is used during the loading of the active components onto the carrier. The active component solution is atomized by an atomizer in the coating machine and uniformly coated onto the carrier surface. Rapid drying at high temperature ensures the uniformity of the dispersion of each active component on the carrier surface, strengthens the interaction between the active components, and thus improves the performance of the catalyst.

[0025] According to some embodiments of the present invention, the coating method employs a coating machine with the following parameters: main unit speed 10–30 rpm, fan speed 1000–2000 rpm, heating chamber temperature 100–200°C, and solution feed rate 3–5 mL / min. Setting the coating machine parameters within the above range allows the impregnation solution to dry rapidly and deposit on the carrier after contact, ensuring the amount and uniformity of impregnation and minimizing the loss of catalyst components.

[0026] According to some embodiments of the present invention, the temperature of the first drying is 80-150°C and the time is 6-24 hours.

[0027] According to some embodiments of the present invention, the temperature of the first calcination is 450–750°C, and the time is 6–24 hours.

[0028] According to some embodiments of the present invention, the temperature of the second drying is 80-150°C, and the time is 6-24 hours.

[0029] According to some embodiments of the present invention, the temperature of the second calcination is 450–750°C, and the time is 6–24 hours.

[0030] Thirdly, the present invention provides the application of the catalyst described in the first aspect in the dehydrogenation of alkanes to olefins.

[0031] According to some embodiments of the present invention, the alkane is propane.

[0032] According to some embodiments of the present invention, the reaction conditions for the dehydrogenation of alkane to olefins are as follows: a steam to propane volume ratio of (10–1):1, a reaction temperature of 400–600°C, a reaction pressure of 0–1 MPa, and an alkane mass hourly space velocity of 3.0–8.0 h⁻¹. -1 .

[0033] The beneficial effects of this invention are at least as follows:

[0034] The low-precious-metal-content supported catalyst provided by this invention reduces the loading of the precious metal Pt, thereby reducing the catalyst cost; at the same time, it maintains good performance in alkane dehydrogenation reaction and has promising prospects for industrial application. Detailed Implementation

[0035] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0036] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0037] Preparation Example

[0038] Weigh 297.49g of zinc nitrate hexahydrate and 750.26g of aluminum nitrate nonahydrate and dissolve them in 1L of deionized water. Mix well and slowly add ammonia water dropwise while stirring continuously to adjust the pH to 7.7. Age the product for 2 hours, wash the filter cake with 4L of water, dry the filter cake at 110℃ for 16 hours, and then calcine it in a muffle furnace at 680℃ for 15 hours to obtain the ZnAl2O4 support.

[0039] Example 1

[0040] 8.44 g of magnesium nitrate hexahydrate was dissolved in 100 mL of water, and 96.58 g of the ZnAl2O4 support from the preparation example was added with stirring. The mixture was dried at 110 °C for 16 hours and calcined in a muffle furnace at 680 °C for 15 hours to obtain the catalyst precursor. 0.32 g of chloroplatinic acid hexahydrate, 7.23 g of ferric nitrate nonahydrate, and 2.01 g of ammonium metatungstate were dissolved in 100 mL of water. This solution was sprayed onto the catalyst precursor using a Labcouting IV high-efficiency coating machine. The spraying steps were as follows: the catalyst precursor was poured into a rotating drum; the main unit speed was set to 20 rpm, the fan speed to 1500 rpm, and the heating chamber temperature to 180 °C; when the material temperature reached 50 °C, the solution feed rate was set to 5 mL / min; after spraying, the coating machine continued to run for 30 minutes, the catalyst precursor sprayed into the solution was removed, dried at 110 °C for 16 hours, and calcined in a muffle furnace at 680 °C for 15 hours to obtain the catalyst.

[0041] Example 2

[0042] 8.44 g of magnesium nitrate hexahydrate was dissolved in 100 mL of water, and 95.12 g of the ZnAl2O4 support from the preparation example was added with stirring. The mixture was dried at 110 °C for 16 hours and calcined in a muffle furnace at 680 °C for 15 hours to obtain the catalyst precursor. 0.213 g of chloroplatinic acid hexahydrate, 14.46 g of ferric nitrate nonahydrate, and 2.68 g of ammonium metatungstate were dissolved in 100 mL of water. This solution was sprayed onto the catalyst precursor using a Labcouting IV high-efficiency coating machine. The spraying steps were as follows: the catalyst precursor was poured into a rotating drum; the main unit speed was set to 15 rpm, the fan speed to 2000 rpm, and the heating chamber temperature to 180 °C; when the material temperature reached 50 °C, the solution feed rate was set to 4 mL / min; after spraying, the coating machine continued to run for 30 minutes, the catalyst precursor sprayed into the solution was removed, dried at 110 °C for 16 hours, and calcined in a muffle furnace at 680 °C for 15 hours to obtain the catalyst.

[0043] Example 3

[0044] The catalyst was prepared in accordance with Example 1, except that 8.44 g of magnesium nitrate hexahydrate was replaced with 4.71 g of calcium nitrate tetrahydrate.

[0045] Example 4

[0046] The catalyst was prepared in accordance with Example 1, except that 8.44 g of magnesium nitrate hexahydrate was replaced with 1.93 g of strontium nitrate.

[0047] Example 5

[0048] The catalyst was prepared in accordance with Example 1, except that 7.23g of ferric nitrate nonahydrate was replaced with 4.94g of cobalt nitrate hexahydrate.

[0049] Example 6

[0050] The catalyst was prepared according to Example 1, except that 7.23g of ferric nitrate nonahydrate was replaced with 4.96g of nickel nitrate hexahydrate.

[0051] Example 7

[0052] Weigh 8.44g magnesium nitrate hexahydrate, 0.32g chloroplatinic acid hexahydrate, 7.23g ferric nitrate nonahydrate, and 2.01g ammonium metatungstate and dissolve them in 100mL of water. Spray this solution onto 96.58g of the prepared ZnAl2O4 support using a Labcouting IV high-efficiency coating machine. The spraying steps are as follows: pour the ZnAl2O4 support into a rotating drum; set the main unit speed to 20 rpm, the fan speed to 1500 rpm, and the heating chamber temperature to 180℃; when the material temperature reaches 50℃, set the solution feed rate to 5mL / min; after spraying, the coating machine continues to run for 30min, remove the ZnAl2O4 support with the sprayed solution, dry it at 110℃ for 16 hours, and calcine it in a muffle furnace at 680℃ for 15 hours to obtain the catalyst.

[0053] Example 8

[0054] 8.44 g of magnesium nitrate hexahydrate was dissolved in 100 mL of water, and 96.58 g of the ZnAl2O4 support from the preparation example was added with stirring. The mixture was dried at 110 °C for 16 hours and calcined in a muffle furnace at 680 °C for 15 hours to obtain the catalyst precursor. 0.32 g of chloroplatinic acid hexahydrate, 7.23 g of ferric nitrate nonahydrate, and 2.01 g of ammonium metatungstate were dissolved in 100 mL of water, and the catalyst precursor was added with stirring. The mixture was dried at 110 °C for 16 hours and calcined in a muffle furnace at 680 °C for 15 hours to obtain the catalyst.

[0055] Comparative Example 1

[0056] Weigh 0.32 g of chloroplatinic acid hexahydrate and dissolve it in 100 mL of water. Add the solution to 99.88 g of the ZnAl2O4 support prepared in the example while stirring. Mix well, let stand for 2 hours, dry at 110 °C for 16 hours, and calcine in a muffle furnace at 680 °C for 15 hours to obtain the catalyst.

[0057] Comparative Example 2

[0058] The catalyst was prepared according to Example 1, except that 2.01g of ammonium metatungstate was not added, and the amount of ZnAl2O4 support added was 98.08g.

[0059] Comparative Example 3

[0060] Weigh 0.32 g of chloroplatinic acid hexahydrate, 7.23 g of ferric nitrate nonahydrate, and 2.01 g of ammonium metatungstate and dissolve them in 100 mL of water. Spray this solution onto 97.38 g of the ZnAl2O4 support from the preparation example using a Labcouting IV high-efficiency coating machine. The spraying steps are as follows: pour the ZnAl2O4 support into a rotating drum; set the main unit speed to 20 rpm, the fan speed to 1500 rpm, and the heating chamber temperature to 180℃; when the material temperature reaches 50℃, set the solution feed rate to 5 mL / min; after spraying, the coating machine continues to run for 30 min, remove the ZnAl2O4 support with the sprayed solution, dry it at 110℃ for 16 hours, and calcine it in a muffle furnace at 680℃ for 15 hours to obtain the catalyst.

[0061] Comparative Example 4

[0062] The catalyst was prepared according to Example 1, except that 7.23g of ferric nitrate nonahydrate was not added, and the amount of ZnAl2O4 support added was 97.58g.

[0063] Catalyst performance evaluation

[0064] (1) Catalyst activity evaluation

[0065] The catalysts prepared in each embodiment and comparative example were evaluated for their activity in an isothermal fixed-bed reactor. The evaluation methods are as follows:

[0066] Propane gas is fed into a preheating zone for mixing by adjusting the flow rate using a mass flow meter, and then enters the reaction zone. Both the preheating and reaction zones of the reactor are heated by heating wires to reach a predetermined temperature. The reactor is constructed with a stainless steel sleeve with an inner diameter of Ф9mm-Ф6mm and a length of approximately 400mm. After the reaction, the gas passes through a condenser and is then analyzed by gas chromatography to determine its composition.

[0067] Evaluation criteria include:

[0068] 0.5 g of catalyst was loaded into the above-mentioned isothermal fixed-bed reactor (catalyst bed height 17 mm), and the reactor was kept at atmospheric pressure and a temperature of 560 °C; the volume ratio of water vapor to propane was 8:1; and the propane mass hourly space velocity was 3.0 h⁻¹. -1 .

[0069] The calculation methods for propane conversion and propylene selectivity are as follows:

[0070]

[0071]

[0072] The content of substances in the above calculation formulas are all molar amounts.

[0073] The evaluation results are shown in Table 1.

[0074] (2) Surface area of ​​Pt on the catalyst:

[0075] Using AutoChem II 2920 from Micromeritics Inc. (USA), the temperature was increased to 550℃ at a rate of 10℃ / min, and reduction was performed using H2 / Ar for 2 hours. The atmosphere was then switched to Ar, and the temperature was increased to 580℃, purged for 1 hour, and then cooled to 45℃. Pure H2 was used, and adsorption was achieved through pulsed heating every 3 minutes until equilibrium was reached. The system was calculated based on the pulse adsorption capacity V of H2. H (mL, STP), assuming the adsorption atomic ratio of metal Pt to H2 is 1:1, the surface area S of metal Pt on the catalyst is... Pt (m 2 The formula for calculating / g) is as follows:

[0076]

[0077] In the formula, V H (mL, STP) represents the total volume of H2 consumed by the sample; N0 is Avogadro's constant, 6.019 × 10⁻⁶. 23 σ is the cross-sectional area of ​​a Pt atom (0.089 nm), W is the mass (g) of the catalyst sample, and P is the mass fraction (%) of Pt in the catalyst.

[0078] (3) Catalyst surface area:

[0079] The N2 physical adsorption method was used to determine the specific surface area and pore size distribution using a Micromeritics Inc. ASAP2010 rapid surface area and pore size distribution analyzer. Before sample measurement, 0.1 g of the sample was degassed under vacuum at 300 °C for more than 5 h, and then N2 adsorption-desorption experiments were performed at liquid nitrogen temperature to obtain adsorption-desorption curves. The catalyst surface area was calculated using the Brunauer-Emmet-Teller (BET) method.

[0080] Table 1

[0081]

[0082]

[0083] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A supported catalyst with low precious metal content, characterized in that, include: a) Pt or its oxide, b) W or its oxide, c) Group IIA elements or their oxides, d) iron-group elements or their oxides, and e) support; the mass ratio of the components is a:b:c:d:e = (0.01~0.3):(1~3):(0.01~1):(0.5~3):(95~99); The surface area of ​​Pt accounts for 0.5% to 1.0% of the total surface area of ​​the catalyst; The carrier comprises ZnAl2O4 composite oxide.

2. The catalyst according to claim 1, characterized in that, The mass ratio of each component is a:b:c:d:e = (0.01~0.2):(1~2):(0.1~0.8):(0.5~2):(95~99).

3. The catalyst according to claim 1 or 2, characterized in that, The group IIA elements include at least one of Mg, Ca, or Sr; And / or, the iron group elements include at least one of Fe, Co or Ni.

4. A method for preparing the catalyst according to any one of claims 1-3, characterized in that, include: The catalyst is prepared by mixing a solution containing soluble salts of Pt, W, Group IIA elements, and iron group elements with a support, drying, and calcining.

5. The preparation method according to claim 4, characterized in that, The preparation method includes: first, mixing a first solution containing soluble salts of Group IIA elements with a support, followed by a first drying and a first calcination to obtain a catalyst precursor; then, mixing a second solution containing soluble salts of Pt, W, and iron-based elements with the catalyst precursor, followed by a second drying and a second calcination to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that, The mixing of the second solution with the catalyst precursor includes: spraying the second solution onto the surface of the catalyst precursor using a coating method.

7. The preparation method according to claim 6, characterized in that, The coating method uses a coating machine with the following parameters: main unit speed 10~30 rpm, fan speed 1000~2000 rpm, heating chamber temperature 100~200℃, and solution feed rate 3~5 mL / min.

8. The preparation method according to any one of claims 5-7, characterized in that, The temperature for the first drying step is 80–150°C; And / or, the temperature of the first calcination is 450–750°C, and the time is 6–24 hours; And / or, the temperature of the second drying is 80–150°C; And / or, the second calcination temperature is 450–750°C, and the time is 6–24 hours.

9. The use of the catalyst according to any one of claims 1-3 in the dehydrogenation of alkane to olefins.

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