Catalyst for n-butane skeletal isomerization and preparation method and application thereof

Abstract

The present invention discloses a catalyst for the skeletal isomerization of n-butane, and a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: S1, immersing a silica carrier in an iron salt solution, first standing, and first drying to obtain a catalyst precursor; S2, immersing the catalyst precursor in an ammonium sulfate solution, second standing, and second drying and first roasting to obtain an intermediate product; S3, immersing the intermediate product in a solution containing a palladium salt and / or a platinum salt, third standing, and third drying and second roasting. The catalyst preparation flow of the present invention is short, the preparation process is simple, and the prepared catalyst has good catalytic activity and selectivity for the skeletal isomerization of n-butane.

Description

Technical Field

[0001] The invention belongs to the field of heterogeneous catalyst preparation, and specifically relates to a catalyst for n-butane skeletal isomerization reaction, a preparation method and application thereof. Background Art

[0002] In industry, C4 alkanes mainly come from catalytic cracking units. It is very important to develop high-octane clean components for gasoline blending. Alkyl oil has the advantages of high octane number, low volatility, no aromatics and olefins, and almost no sulfur, making it very suitable for oil blending. Isobutane is one of the raw materials for producing hydrocarbon alkyl oil, so the development of catalysts for isomerization of n-butane to produce isobutane is of great significance to the production of clean gasoline.

[0003] Isomerization catalysts usually use platinum halide / alumina catalysts with γ-Al2O3 as carriers. During the operation, an appropriate amount of chloride additives needs to be continuously added to the raw materials. The main problem with this technology is that it has strict requirements on the water and sulfur content in the raw materials, which needs to be less than 0.1ppm. At the same time, the chlorine-containing substances produced during the reaction are corrosive to the equipment, increasing the equipment material cost and maintenance cost, and also polluting the environment.

[0004] Sulfated solid superacid catalysts not only do not contain chlorine, but also have loose requirements on the moisture and sulfur content of the raw materials and can be regenerated, which is the development direction of isomerization catalysts. The following patents disclose the preparation method of isomerization catalysts for alkanes such as n-butane.

[0005] CN1660973A discloses a method for isomerizing C5 and C6 alkanes, wherein the catalyst preparation process comprises: reacting a zirconium salt solution with an alkaline solution to prepare zirconium hydroxide; mixing aluminum hydroxide with silica sol and drying; 2- Solution impregnation and drying; metal salt solution impregnation, drying and roasting.

[0006] CN106732676A discloses a n-butane isomerization catalyst, which comprises co-precipitating, filtering, washing and drying zirconium salt, gallium salt solution and ammonia water or urea aqueous solution to obtain a precursor, and then impregnating other component solutions, drying and calcining to finally prepare a ZrO2 catalyst.

[0007] CN106140197A and CN106101797B disclose a solid superacid catalyst and a preparation method thereof and a method for isomerizing light normal alkanes. Ammonia water and a metal salt solution are co-precipitated, filtered, washed, dried, then impregnated in steps, dried, and finally roasted to obtain the catalyst.

[0008] CN107051420A discloses a method for preparing a catalyst for n-butane isomerization. The catalyst preparation steps of the method include: hydrothermal reaction of ammonia water and zirconium salt to generate hydroxide; precipitation filtering, washing and drying; impregnation and drying of an acidic solution containing SO42-; and impregnation, drying and roasting of a metal salt solution.

[0009] CN10822184A discloses an alkane isomerization catalyst and a preparation method thereof, comprising preparing zirconium hydroxide, SO4 2- The process includes solution impregnation, drying, mixing with silica sol, nickel salt solution impregnation, drying, calcination and other complex processes.

[0010] CN10807998A discloses a catalyst for isomerization of C5 and C6 alkanes and its preparation and application. A metal-doped ZrO2 precursor is prepared by a coprecipitation method, and a catalyst is obtained after being distributedly impregnated with oxytungstic acid and a metal salt, dried and calcined.

[0011] CN109772287A discloses an alkane isomerization catalyst carrier and a preparation method thereof, the catalyst and the preparation method thereof, wherein the preparation process involves multiple steps such as reaction of zirconium salt and ammonia water, filtration, washing, drying, multiple impregnation and drying, and roasting.

[0012] It can be seen from the above patent that the SO4 currently used in butane isomerization 2- / ZrO2 catalyst is generally prepared by reacting zirconium salt with ammonia water to generate zirconium hydroxide precipitate, which is filtered, washed and dried to obtain catalyst precursor, and then impregnated with SO4 2- The method involves many steps and a long process, produces alkaline wastewater containing ammonia, and requires a large amount of water to wash the precipitate to neutrality, and multiple drying consumes a lot of energy. At the same time, the cost of zirconium-based catalysts is relatively high. Summary of the invention

[0013] In view of the above problems existing in the prior art, the present invention provides a new catalyst for the skeletal isomerization of n-butane and a preparation method thereof. The sulfated iron oxide catalyst of the present invention has the advantages of good catalyst performance, short preparation flow, simple preparation process and low iron consumption in the preparation process.

[0014] The first aspect of the present invention provides a method for preparing a catalyst for skeletal isomerization of n-butane, comprising the following steps:

[0015] S1, immersing the silica carrier in an iron salt solution, first allowing it to stand, and first drying it to obtain a catalyst precursor;

[0016] S2, immersing the catalyst precursor in an ammonium sulfate solution, allowing it to stand for a second time, and performing a second drying and a first calcination to obtain an intermediate product;

[0017] S3, immersing the intermediate product in a solution containing palladium salt and / or platinum salt, allowing to stand for a third time, drying for a third time, and calcining for a second time.

[0018] According to some embodiments of the present invention, preferably, the specific surface area of ​​the silica carrier is 200 to 600 m 2 / g.

[0019] According to some embodiments of the present invention, preferably, the pore size of the silica carrier is 10 to 20 nm.

[0020] According to some embodiments of the present invention, preferably, the iron salt is ferric nitrate; preferably, calculated as ferric nitrate, the amount of ferric nitrate used is 20 to 80% by mass of the carrier.

[0021] According to some embodiments of the present invention, preferably, the iron salt solution is a ferric nitrate solution, and the content of ferric nitrate in the ferric nitrate solution is 15 to 75% by mass.

[0022] According to some embodiments of the present invention, preferably, in step S2, the amount of ammonium sulfate used is 5 to 25 mass % of the catalyst precursor.

[0023] According to some embodiments of the present invention, preferably, in the ammonium sulfate solution, the content of ammonium sulfate is 4 to 25% by mass.

[0024] According to some embodiments of the present invention, preferably, the palladium salt in step S3 is palladium nitrate and / or palladium chloride, and the platinum salt is chloroplatinic acid.

[0025] According to some embodiments of the present invention, preferably, the amount of palladium salt and / or platinum salt used is 0.1-0.5 mass % of the intermediate product, calculated as Pd and / or Pt element.

[0026] According to some embodiments of the present invention, preferably, the conditions of the first standing, the second standing, and the third standing each independently include: a temperature of 20 to 40° C., and a time of 20 to 28 hours.

[0027] According to some embodiments of the present invention, preferably, the conditions of the first drying, the second drying and the third drying each independently include: a temperature of 100 to 150° C. and a time of 10 to 20 hours.

[0028] According to some embodiments of the present invention, preferably, the first calcination conditions include: a temperature of 500-800° C., preferably 650-750° C., and a calcination time of 3-8 hours. The calcination can be performed in air using a muffle furnace.

[0029] According to some embodiments of the present invention, preferably, the second calcination conditions include: a temperature of 300-500° C. and a time of 3-8 hours. The calcination can be performed in air using a muffle furnace.

[0030] The second aspect of the present invention provides a catalyst for the skeletal isomerization of n-butane prepared by the above method. The catalyst is M / SO4 2- / Fe2O3@SiO2, wherein M is Pt and / or Pd.

[0031] The third aspect of the present invention provides a catalyst prepared according to the above method or the use of the above catalyst in the skeletal isomerization reaction of n-butane.

[0032] According to some embodiments of the present invention, preferably, the catalyst is subjected to activation treatment before use.

[0033] According to some embodiments of the present invention, preferably, the activation treatment process comprises: heating in a nitrogen flow containing 10 volume % hydrogen.

[0034] According to some embodiments of the present invention, preferably, the activation temperature is 350-450°C.

[0035] According to some embodiments of the present invention, preferably, the activation time is 2 to 6 hours.

[0036] According to some embodiments of the present invention, preferably, the n-butane skeletal isomerization reaction is carried out under hydrogen conditions.

[0037] According to some embodiments of the present invention, preferably, the reaction temperature is 180-220°C.

[0038] According to some embodiments of the present invention, preferably, the reaction pressure is 0.5-2 MPa.

[0039] According to some embodiments of the present invention, preferably, the butane volume space velocity is 0.2 to 2 h -1 .

[0040] According to some embodiments of the present invention, preferably, the hydrogen to hydrocarbon molar ratio is 0.1 to 1.0:1.

[0041] According to some embodiments of the present invention, the catalyst needs to be activated before use. The catalyst is activated by heating in a nitrogen flow containing 10% volume fraction hydrogen. The activation temperature is 350-450° C. and the activation time is 2-6 hours.

[0042] According to some embodiments of the present invention, the n-butane skeletal isomerization reaction is carried out under hydrogen conditions, with a reaction temperature of 180 to 220° C., a pressure of 0.5 to 2.0 MPa, and a butane volume space velocity of 0.2 to 2 h -1 , the molar ratio of hydrogen to hydrocarbon is 0.1 to 1.0:1.

[0043] Beneficial effects of the present invention:

[0044] (1) The present invention uses silica beads as a carrier to simply prepare an iron-based solid superacid catalyst, and the metal modification and introduction of hydrogenation components can enhance the catalyst's ability to resist carbon deposition. The preparation process of the present invention is short, the steps are simple, and the amount of iron used is small.

[0045] (2) The catalyst of the present invention is insensitive to the content of impurities such as oxygen and sulfur in the raw materials. The prepared catalyst has high catalytic activity, selectivity and stability for the skeletal isomerization of n-butane at low temperatures. DETAILED DESCRIPTION

[0046] In order to make the present invention more easily understood, the present invention will be described in detail below in conjunction with embodiments. These embodiments are only for illustration and are not intended to limit the application scope of the present invention.

[0047] In the following examples and comparative examples, silicon oxide beads were purchased from Qingdao Ocean Chemical Co., Ltd.

[0048] [Example 1]

[0049] Take 100g of silica spheres (specific surface area 346m 2 / g, pore size 10.5nm), added into 100mL ferric nitrate solution (mass fraction 20%), left at room temperature for 24h, and then baked at 110°C for 12h to obtain a precursor.

[0050] Take 100g of the precursor, add it into 100mL of ammonium sulfate solution (mass fraction is 20%), place it at room temperature for 24h, then bake it at 110℃ for 12h, and calcine it in a muffle furnace with air at a calcination temperature of 720℃ and a calcination time of 5h.

[0051] Take 100 g of the calcined sample and add it to 100 mL of chloroplatinic acid solution containing 0.3 g of platinum element, place it at room temperature for 24 hours, then bake it at 110°C for 12 hours, grind it and calcine it in a muffle furnace at a calcination temperature of 400°C for 4 hours to obtain a solid superacid catalyst, recorded as PtSFe-1.

[0052] [Example 2]

[0053] Except that the mass fraction of iron nitrate is 40% (i.e., instead of the mass fraction of iron nitrate of 20% in Example 1), other conditions of Example 2 are the same as those of Example 1, and a solid superacid catalyst is obtained, which is recorded as PtSFe-2.

[0054] [Example 3]

[0055] Except that the mass fraction of iron nitrate is 60% (i.e., instead of the mass fraction of iron nitrate of 20% in Example 1), other conditions of Example 3 are the same as those of Example 1, and a solid superacid catalyst is obtained, which is recorded as PtSFe-3.

[0056] [Example 4]

[0057] Except that the mass fraction of iron nitrate is 75% (i.e., instead of the mass fraction of iron nitrate of 20% in Example 1), other conditions of Example 4 are the same as those of Example 1, and a solid superacid catalyst is obtained, which is recorded as PtSFe-4.

[0058] [Example 5]

[0059] Except that the mass fraction of ammonium sulfate is 15% (i.e., the mass fraction of ammonium sulfate in Example 3 is 20%), the other conditions of Example 5 are the same as those of Example 3, and a solid superacid catalyst is obtained, which is recorded as PtSFe-5.

[0060] [Example 6]

[0061] Except that the mass fraction of ammonium sulfate is 10% (i.e., the mass fraction of ammonium sulfate in Example 3 is 20%), the other conditions of Example 6 are the same as those of Example 3, and a solid superacid catalyst is obtained, which is recorded as PtSFe-6.

[0062] [Example 7]

[0063] Except that the mass fraction of ammonium sulfate is 5% (i.e., the mass fraction of ammonium sulfate in Example 3 is 20%), the other conditions of Example 7 are the same as those of Example 3, and a solid superacid catalyst is obtained, which is recorded as PtSFe-7.

[0064] [Example 8]

[0065] Except for adding 100 mL of palladium nitrate solution containing 0.3 g of palladium element (i.e., palladium nitrate solution replaces the chloroplatinic acid solution in Example 3), Example 8 is the same as Example 3 under other conditions to obtain a solid superacid catalyst, which is recorded as PdSFe-8.

[0066] [Example 9]

[0067] Except for adding 100 mL of palladium chloride solution containing 0.3 g of palladium element (i.e., palladium chloride solution replaces the chloroplatinic acid solution in Example 3), Example 9 is the same as Example 3 under other conditions to obtain a solid superacid catalyst, which is recorded as PdSFe-9.

[0068] [Example 10]

[0069] Except for the first calcination temperature of 650°C (i.e., the first calcination temperature of 650°C replaces the first calcination temperature of 720°C in Example 3), Example 10 is the same as Example 3 in other conditions to obtain a solid superacid catalyst, recorded as PdSFe-10.

[0070] [Example 11]

[0071] Except for the first calcination temperature of 500°C (i.e., the first calcination temperature of 500°C replaces the first calcination temperature of 720°C in Example 3), Example 11 is the same as Example 3 in other conditions to obtain a solid superacid catalyst, recorded as PdSFe-11.

[0072] [Example 12]

[0073] Except for the first calcination temperature of 450°C (i.e., the first calcination temperature of 450°C replaces the first calcination temperature of 720°C in Example 3), Example 12 is the same as Example 3 in other conditions to obtain a solid superacid catalyst, recorded as PdSFe-12.

[0074] [Example 13]

[0075] Except for the first calcination temperature of 800°C (i.e., the first calcination temperature of 800°C replaces the first calcination temperature of 720°C in Example 3), Example 13 is the same as Example 3 in other conditions to obtain a solid superacid catalyst, recorded as PdSFe-13.

[0076] [Example 14]

[0077] Except for the first calcination temperature of 900°C (i.e., the first calcination temperature of 900°C replaces the first calcination temperature of 720°C in Example 3), Example 14 is the same as Example 3 in other conditions to obtain a solid superacid catalyst, recorded as PdSFe-14.

[0078] [Example 15]

[0079] In addition to silica beads (specific surface area of ​​600m 2 / g) instead of silica beads (specific surface area 346m 2 / g), the other conditions of Example 15 were the same as those of Example 3 to obtain a solid superacid catalyst, which was recorded as PdSFe-15.

[0080] [Example 16]

[0081] In addition to silica beads (specific surface area of ​​200m 2 / g) instead of silica beads (specific surface area 346m 2 / g), the other conditions of Example 16 were the same as those of Example 3 to obtain a solid superacid catalyst, which was recorded as PdSFe-16.

[0082] [Example 17]

[0083] Except that silica beads (pore size 15 nm) were used instead of silica beads (pore size 10.5 nm), the other conditions of Example 17 were the same as those of Example 3 to obtain a solid superacid catalyst, which was recorded as PdSFe-17.

[0084] [Example 18]

[0085] Except that silica beads (pore size 5.0 nm) were used instead of silica beads (pore size 10.5 nm), the other conditions of Example 18 were the same as those of Example 3 to obtain a solid superacid catalyst, which was recorded as PdSFe-18.

[0086]

Comparative Example 1

[0087] Except that the silicon dioxide was not impregnated with the ferric nitrate solution, the other conditions of Control Example 1 were the same as those of Example 3 to obtain a catalyst, which was recorded as CB-1.

[0088]

Comparative Example 2

[0089] Except that ammonium acetate solution was used instead of ammonium sulfate solution, the other conditions of Control Example 2 were the same as those of Example 3 to obtain a catalyst, which was recorded as CB-2.

[0090]

Comparative Example 3

[0091] Only the second roasting is carried out, specifically:

[0092] Take 100g of silica spheres (specific surface area 300m 2 / g, pore size 10.5nm), added into 100mL ferric nitrate solution (mass fraction 20%), left at room temperature for 24h, and then baked at 110°C for 12h to obtain a precursor.

[0093] Take 100 g of the precursor, add it into 100 mL of ammonium sulfate solution (mass fraction 20%), leave it at room temperature for 24 h, and then bake it at 110° C. for 12 h.

[0094] 100 g of the calcined sample was added into 100 mL of chloroplatinic acid solution containing 0.3 g of platinum element, placed at room temperature for 24 h, then baked at 110°C for 12 h, ground and calcined in a muffle furnace at 400°C for 4 h to obtain a solid superacid catalyst, recorded as CB-3.

[0095]

Test example

[0096] The performance evaluation of the n-butane skeletal isomerization catalysts of Examples 1-18 and Comparative Examples 1-3 was conducted on a fixed bed continuous flow reaction system. The reaction tube had a specification of 5 mm × 40 cm, a catalyst loading of 10 mL, and a particle size of 20-40 meshes, and was placed in the constant temperature zone of the furnace. The reaction temperature was 200°C, the hydrogen pressure was 1 MPa, and the butane volume space velocity was 1 h -1 The molar ratio of hydrogen to hydrocarbon was 1:1, and the reaction products were analyzed online by gas chromatography. The results of the catalyst performance evaluation are shown in Table 1.

[0097] Table 1 Catalytic performance of n-butane skeletal isomerization

[0098]

[0099]

[0100] It can be seen from Table 1 that only the catalyst obtained by simultaneously impregnating ferric nitrate and sulfate is active, and the solid superacid catalyst prepared by the method of the present invention has good activity and selectivity.

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this field, under the technical enlightenment provided by the present invention, as common knowledge in the field, other equivalent variations and improvements can also be made, which should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for n-butane skeletal isomerization, comprising the following steps: S1, immersing the silica carrier in an iron salt solution, first allowing it to stand, and first drying it to obtain a catalyst precursor; S2, immersing the catalyst precursor in an ammonium sulfate solution, allowing it to stand for a second time, and performing a second drying and a first calcination to obtain an intermediate product; S3, immersing the intermediate product in a solution containing a palladium salt and / or a platinum salt, allowing it to stand for a third time, and drying and calcining it for a third time; The iron salt is ferric nitrate; Calculated as ferric nitrate, the amount of ferric nitrate used is 20 to 80% by mass of the carrier; The amount of ammonium sulfate used is 5 to 25% by mass of the catalyst precursor; The amount of palladium salt and / or platinum salt used is 0.1 to 0.5 mass % of the intermediate product, calculated as Pd and / or Pt element.

2. The preparation method according to claim 1, characterized in that: The specific surface area of ​​the silica carrier is 200 to 600 m 2 / g, and / or, the pore size of the silica carrier is 10 to 20 nm.

3. The preparation method according to claim 1 or 2, characterized in that: The content of iron nitrate in the iron nitrate solution is 15 to 75% by mass.

4. The preparation method according to claim 1 or 2, characterized in that: The content of ammonium sulfate in the ammonium sulfate solution is 4 to 25% by mass.

5. The preparation method according to claim 1 or 2, characterized in that: In step S3, the palladium salt is palladium nitrate and / or palladium chloride, and the platinum salt is chloroplatinic acid.

6. The preparation method according to claim 1 or 2, characterized in that: The conditions of the first standing, the second standing and the third standing independently include: a temperature of 20 to 40° C. and a time of 20 to 28 hours.

7. The preparation method according to claim 1 or 2, characterized in that: The conditions of the first drying, the second drying, and the third drying each independently include: The temperature is 100-150°C and the time is 10-20 hours.

8. The preparation method according to claim 1 or 2, characterized in that: The first calcination conditions include: a temperature of 500-800° C. and a calcination time of 3-8 hours; and / or, The second calcination conditions include: a temperature of 300 to 500° C. and a time of 3 to 8 hours.

9. The preparation method according to claim 8, characterized in that: The first calcination conditions include: a temperature of 650-750°C.

10. A catalyst for skeletal isomerization of n-butane prepared by the method according to any one of claims 1 to 9.

11. Use of the catalyst prepared by the method according to any one of claims 1 to 9 or the catalyst according to claim 10 in the skeletal isomerization reaction of n-butane.

12. The use according to claim 11, characterized in that: The catalyst is activated before use; And / or, the n-butane skeletal isomerization reaction is carried out under hydrogen conditions; and / or, the reaction temperature is 180-220°C; and / or, the reaction pressure is 0.5 to 2 MPa; And / or, butane volume space velocity is 0.2~2h -1 ; And / or, the molar ratio of hydrogen to hydrocarbon is 0.1 to 1.0:

1.

13. The use according to claim 12, characterized in that: The activation treatment process includes: heating in a nitrogen flow containing 10 volume % hydrogen; And / or, the activation temperature is 350-450°C; And / or, the activation time is 2 to 6 hours.

Images