A hydrocracking catalyst for producing aviation fuel, its preparation method and application

Abstract

The invention relates to the technical field of catalysts, and discloses a hydrocracking catalyst for preparing aviation fuel, a preparation method thereof, and an application thereof. The hydrocracking catalyst comprises a catalyst I and a catalyst II; the catalyst I is mesoporous sulfided zirconium oxide; the catalyst II comprises a carrier and a Ni element loaded on the carrier; the catalyst I is formed by solid-phase calcination of a mixture of (NH4)2SO4 and ZrOCl2·8H2O. The catalyst of the invention can enable the hydrocracking reaction of polyolefins to be carried out under mild conditions without using precious metal elements, and has a high C8~C 15 Hydrocarbon selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a hydrocracking catalyst for preparing aviation fuel, a preparation method and an application thereof. Background Art

[0002] Polyolefins (such as polyethylene, polypropylene, etc.) are used everywhere in our lives. However, due to their acid and alkali resistance and good stability, polyolefin plastics are difficult to degrade in the natural environment, causing serious pollution to the environment. Traditional methods of treating polyolefin waste plastics, such as incineration, pyrolysis, biodegradation and landfill, all have their own shortcomings. For example, incineration wastes energy, landfill pollutes the soil, pyrolysis consumes a lot of energy, and biodegradation is difficult to achieve large-scale industrial production.

[0003] Hydrocracking usually has mild reaction conditions and a narrow carbon number distribution of the product, and is an efficient means of polyolefin recovery. However, traditional polyolefin hydrocracking relies on precious metal catalysts such as Pt and Ru, which are expensive and easily poisoned, making them difficult to prepare on a large scale, and their industrial applications are limited. In addition, the current aviation fuel (C 8 ~C 15 ) is mainly prepared from petroleum products through complex processes. Not only is the process cumbersome and economically costly, but it also increases the degree of dependence on petroleum raw materials. The carbon number of the product of polyolefin hydrocracking is affected by the catalyst, so the hydrocracking catalysts used for different products cannot be used interchangeably. The products of existing hydrocracking catalysts are difficult to meet the carbon number requirements of aviation fuel. Therefore, it is particularly important to develop a non-precious metal catalyst that can efficiently catalyze the hydrocracking of polyolefins to produce aviation fuel under mild conditions. Summary of the invention

[0004] In order to solve the above technical problem, that is, the products of the existing polyolefin hydrocracking catalysts are difficult to meet the carbon number requirements of aviation fuel, and need to rely on precious metal elements to achieve high catalytic activity, the present invention provides a hydrocracking catalyst for producing aviation fuel and its preparation method and application. The catalyst of the present invention can make the polyolefin hydrocracking reaction proceed under mild conditions without using precious metal elements, and has a high C 8 ~C 15 Hydrocarbon selectivity.

[0005] The specific technical scheme of the present invention is:

[0006] In the first aspect, the present invention provides a hydrocracking catalyst for preparing aviation fuel, comprising a catalyst I and a catalyst II; the catalyst I is mesoporous sulfided zirconium oxide; the catalyst II comprises a carrier and a Ni element supported on the carrier; the catalyst I is composed of (NH 4 )2 SO 4 and ZrOCl 2 ·8H 2 O are formed by mixed solid-phase roasting.

[0007] In the present invention, by compounding the above-mentioned catalyst I and catalyst II, high catalytic activity can be achieved without using noble metal elements, enabling the hydrocracking reaction of polyolefins to proceed under mild conditions. Moreover, by using the catalyst of the present invention, the proportion of C 8 ~C 15 hydrocarbons (hydrocarbons with 8 to 15 carbon atoms) in the product of polyolefin hydrocracking is relatively high, which can meet the carbon atom number requirements of aviation fuel and achieve a high aviation fuel yield.

[0008] The hydrocracking catalyst of the present invention is composed of a compound of catalyst I and catalyst II, which enables a certain spatial distance between the Ni active sites and catalyst I, allowing the hydrocracking process of polyolefins to proceed along a suitable reaction route, avoiding deep cracking of the product, and improving the selectivity of C 8 ~C 15 hydrocarbons. If the active component (Ni element) in catalyst II is loaded into catalyst I, the spatial distance between the active sites in catalyst I and Ni will be too close, resulting in a large content of low-carbon hydrocarbons in the product and a too low content of C 8 ~C 15 hydrocarbons.

[0009] In addition, the formation method of catalyst I will also affect the selectivity of C 8 ~C 15 hydrocarbons. In the present invention, catalyst I is formed by the mixed solid-phase roasting of (NH 4 ) 2 SO 4 and ZrOCl 2 ·8H 2 O, which can endow catalyst I with a suitable pore structure, accommodate and stabilize larger-sized reaction intermediates and products, be beneficial to the formation of high-carbon number products, and enable a relatively high proportion of C 8 ~C 15 hydrocarbons in the product of the polyolefin hydrocracking reaction. When catalyst I is formed by impregnation roasting, the selectivity of C 8 ~C 15 hydrocarbons in the polyolefin hydrocracking reaction is relatively low.

[0010] Preferably, the mass ratio of catalyst I to catalyst II is 0.25~1:1.

[0011] In the hydrocracking catalyst of the present invention, when the proportion of Catalyst I is too large, deep cracking will occur, resulting in a decrease in the selectivity of C 8 ~C 15 hydrocarbons and the generation of excessive small-molecule hydrocarbons; while when the proportion of Catalyst II is too large, there is a lack of acidic sites, which will cause a decrease in the activity of catalytic polyolefin hydrocracking and the generation of more high-carbon wax substances. The present invention sets the mass ratio of Catalyst I to Catalyst II to 0.25~1:1, which can further improve the selectivity of C 8 ~C 15 hydrocarbons.

[0012] Preferably, the molar ratio of ZrOCl 2 ·8H 2 O to (NH 4 ) 2 SO 4 is 1:4~10.

[0013] By increasing the dosage of (NH 4 ) 2 SO 4 relative to ZrOCl 2 ·8H 2 O, the number of strong acid sites in Catalyst I can be increased, thereby improving the catalyst activity.

[0014] Preferably, in Catalyst I, the content of Ni element is 2~30 wt%.

[0015] Preferably, the carrier is an inert carrier.

[0016] Furthermore, the inert carrier is SiO 2 and / or Al 2 O 3 .

[0017] Second, the present invention provides a preparation method of the hydrocracking catalyst, including the following steps:

[0018] S1: Mix and grind (NH 4 ) 2 SO 4 and ZrOCl 2 ·8H 2 O, and then calcine in an aerobic atmosphere to obtain Catalyst I;

[0019] S2: Mix the nickel source solution and the carrier, and then perform reduction calcination to obtain Catalyst II;

[0020] S3: Mix Catalyst I and Catalyst II to obtain the hydrocracking catalyst.

[0021] Preferably, in step S1, the aerobic atmosphere is an air atmosphere; the roasting temperature is 600 - 620 °C, and the time is 4.5 - 5.5 h.

[0022] Preferably, in step S2, the reduction roasting process is carried out in a hydrogen atmosphere, the temperature is 600 - 650 °C, and the time is 3 - 5 h.

[0023] In a third aspect, the present invention provides the application of the hydrocracking catalyst in the catalytic hydrocracking of polyolefins to produce aviation fuel, and the aviation fuel is a hydrocarbon having 8 - 15 carbon atoms.

[0024] Preferably, the application includes the following steps: After mixing and grinding the polyolefin powder with the hydrocracking catalyst, hydrogen is introduced for hydrocracking reaction.

[0025] Preferably, during the process of catalytic hydrocracking of polyolefins to produce aviation fuel, the hydrogen pressure is 0.2 - 1 Mpa, and the reaction temperature is 200 - 350 °C.

[0026] Preferably, the polyolefin is one or more of polyethylene, polypropylene, and polystyrene, and the weight - average molecular weight (M w ) is 150,000 - 260,000 Da.

[0027] Preferably, the process of catalytic hydrocracking of polyolefins to produce aviation fuel is carried out in a fixed - bed, fluidized - bed or autoclave.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) In the hydrocracking catalyst of the present invention, by using a specific combination of catalyst I and catalyst II, and adopting the mixed solid - phase roasting method of (NH 4 ) 2 SO 4 and ZrOCl 2 ·8H 2 O to form catalyst I, it is possible to achieve high catalytic activity without using precious metal elements, enabling the hydrocracking reaction of polyolefins to proceed under mild conditions, and having high selectivity for C 8 ~C 15 hydrocarbons. The product can meet the carbon - atom number requirements of aviation fuel, achieving a high aviation - fuel yield.

[0030] (2) In the hydrocracking catalyst of the present invention, by setting the mass ratio between catalyst I and catalyst II to 0.25 - 1:1, it is possible to further improve the C 8 ~C 15Hydrocarbon selectivity enables a higher content of C in the hydrocracking products of polyolefins 8 ~C 15 hydrocarbons. Description of the Drawings

[0031] Figure 1 It is the liquid product distribution diagram obtained after the hydrocracking of polyolefins in Example 1.

[0032] Figure 2 It is the XRD pattern of Catalyst I prepared in Example 1.

[0033] Figure 3 It is the nitrogen adsorption / desorption diagram of Catalyst I prepared in Example 1.

[0034] Figure 4 It is the scanning electron microscope image of Catalyst I prepared in Example 2.

[0035] Figure 5 It is the XRD pattern of Catalyst II prepared in Example 2.

[0036] Figure 6 It is the nitrogen adsorption diagram of Catalyst I prepared in Comparative Example 1. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with the embodiments.

[0038] First, the present invention relates to a hydrocracking catalyst for preparing aviation fuel, including Catalyst I and Catalyst II; the Catalyst I is mesoporous sulfurized zirconia; the Catalyst II includes a carrier and Ni element loaded on the carrier; the Catalyst I is formed by calcining the mixed solid phase of (NH 4 ) 2 SO 4 and ZrOCl 2 ·8H 2 O.

[0039] In some specific embodiments, the mass ratio of the Catalyst I to the Catalyst II is 0.25~1:1.

[0040] In some specific embodiments, the molar ratio of the ZrOCl 2 ·8H 2 O to (NH 4 ) 2 SO 4 is 1:4~10.

[0041] In some specific embodiments, in the Catalyst I, the content of Ni element is 2~30 wt%.

[0042] In some specific embodiments, the carrier is an inert carrier. The aforementioned inert carrier can be selected from SiO 2 , Al 2 O 3 or other commonly used inert carriers in the industry. The specific types are not limited in the present invention.

[0043] Second, the present invention relates to a method for preparing the hydrocracking catalyst, including the following steps:

[0044] S1: After mixing and grinding (NH 4 ) 2 SO 4 and ZrOCl 2 ·8H 2 O, calcine in an aerobic atmosphere to obtain Catalyst I;

[0045] S2: After mixing the nickel source solution and the carrier, perform reduction calcination to obtain Catalyst II;

[0046] S3: Mix Catalyst I and Catalyst II to obtain the hydrocracking catalyst.

[0047] In some specific embodiments, in step S1, the aerobic atmosphere is an air atmosphere; the temperature of the calcination is 600 - 620 °C, and the time is 4.5 - 5.5 h.

[0048] In some specific embodiments, in step S2, the process of reduction calcination is carried out in a hydrogen atmosphere, the temperature is 600 - 650 °C, and the time is 3 - 5 h.

[0049] Third, the present invention relates to the application of the hydrocracking catalyst in the catalytic hydrocracking of polyolefins to produce aviation fuel, and the aviation fuel is a hydrocarbon with 8 - 15 carbon atoms.

[0050] In some specific embodiments, the application includes the following steps: After mixing and grinding the polyolefin powder with the hydrocracking catalyst, introduce hydrogen to carry out the hydrocracking reaction.

[0051] In some specific embodiments, during the process of catalytic hydrocracking of polyolefins to produce aviation fuel, the hydrogen pressure is 0.2 - 1 Mpa, and the reaction temperature is 200 - 350 °C.

[0052] In some specific embodiments, the polyolefin is one or more of polyethylene, polypropylene, and polystyrene, and the weight - average molecular weight (M w ) is 150000 - 260000 Da.

[0053] In some specific embodiments, the process of catalytic hydrocracking of polyolefins to aviation fuel is carried out in a fixed bed, a fluidized bed or an autoclave.

[0054] The present invention will be described below through specific examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, the changes and advantages that can be conceived by those skilled in the art are included in the present invention, and the scope of protection of the present invention is the appended claims and any equivalents thereof.

[0055] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. The raw materials and equipment used in the present invention are conventional raw materials and equipment in the art and can be obtained from conventional commercial channels without special instructions; the methods used in the present invention are conventional methods in the art without special instructions.

[0056] Example 1

[0057] In this example, a hydrocracking catalyst was prepared according to the following steps and used for catalytic hydrocracking of polyolefins to aviation fuel:

[0058] S1: Preparation of Catalyst I

[0059] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. The mixture was allowed to stand at room temperature for 18 h and then calcined in an air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 6). Its XRD is as shown in Figure 2 and the nitrogen adsorption - desorption data is as shown in Figure 3 .

[0060] S2: Preparation of Catalyst II

[0061] The equal - volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano - silica) was adopted. The nickel nitrate aqueous solution and nano - silica were mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain a powdery Catalyst II, in which the Ni loading was 2 wt% (i.e., the Ni content in Catalyst II was 2 wt%).

[0062] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0063] Weigh 50 mg of the catalyst I prepared in step S1, 100 mg of the catalyst II prepared in step S2, and 1 g of polyethylene powder (M w = 150,000 Da), mix and grind them evenly, then load them into an autoclave reactor, introduce 0.2 MPa of hydrogen, and react at 250 °C until the conversion rate of polyolefin reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) is measured to be 74.8%, and the liquid product distribution diagram is as shown in Figure 1 Figure.

[0064] Example 2

[0065] In this example, the hydrocracking catalyst was prepared according to the following steps and used to catalyze the hydrocracking of polyolefin to aviation fuel:

[0066] S1: Preparation of catalyst I

[0067] Grind ammonium sulfate and zirconium oxychloride octahydrate at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 4:1. Let it stand at room temperature for 18 h and calcine it in an air atmosphere at 600 °C for 5 h to obtain catalyst I (S / Zr = 4). Its scanning electron micrograph is as shown in Figure 4 Figure ( Figure 4 the scale in the lower right corner in the figure means that all the small grids add up to 5.00 μm).

[0068] S2: Preparation of catalyst II

[0069] Adopt the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), mix the nickel nitrate aqueous solution and the nano-silica, and ultrasonicate for 2 h to form a homogeneous mixture. Then calcine it in a hydrogen atmosphere at 600 °C for 3 h to obtain the powdery catalyst II, where the Ni loading is 15 wt% (that is, the Ni content in the catalyst II is 15 wt%). The XRD pattern of catalyst II is as shown in Figure 5 Figure, indicating that the existence form of the Ni element is metallic Ni.

[0070] S3: Catalyze the hydrocracking of polyolefin to aviation fuel

[0071] Weigh 50 mg of the catalyst I prepared in step S1, 100 mg of the catalyst II prepared in step S2, and 1 g of polyethylene powder (M w= 150,000 Da), after mixing and grinding evenly, it was loaded into an autoclave reactor, 1 MPa of hydrogen was introduced, and the reaction was carried out at 200 °C until the conversion rate of polyolefin reached 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) was 60.4%.

[0072] Example 3

[0073] In this example, the hydrocracking catalyst was prepared according to the following steps and used for catalyzing the hydrocracking of polyolefin to produce aviation fuel:

[0074] S1: Preparation of Catalyst I

[0075] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 10:1. It was left standing at room temperature for 18 h and calcined in air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 10).

[0076] S2: Preparation of Catalyst II

[0077] By the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), the nickel nitrate aqueous solution and the nano-silica were mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain a powdery Catalyst II, in which the Ni loading was 30 wt% (i.e., the Ni content in Catalyst II was 30 wt%).

[0078] S3: Catalyzing the hydrocracking of polyolefin to produce aviation fuel

[0079] Weighed 25 mg of Catalyst I prepared in step S1, 100 mg of Catalyst II prepared in step S2 and 1 g of polyethylene powder (M w = 150,000 Da), after mixing and grinding evenly, it was loaded into an autoclave reactor, 0.5 MPa of hydrogen was introduced, and the reaction was carried out at 250 °C until the conversion rate of polyolefin reached 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) was 72.7%.

[0080] Example 4

[0081] In this example, the hydrocracking catalyst was prepared according to the following steps and used for catalyzing the hydrocracking of polyolefin to produce aviation fuel:

[0082] S1: Preparation of Catalyst I

[0083] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. The mixture was allowed to stand at room temperature for 18 h and then calcined in air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 6).

[0084] S2: Preparation of Catalyst II

[0085] By the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), the nickel nitrate aqueous solution and the nano-silica were mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain the powdery Catalyst II, in which the Ni loading is 30 wt% (i.e., the Ni content in Catalyst II is 30 wt%).

[0086] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0087] 50 mg of Catalyst I prepared in step S1, 100 mg of Catalyst II prepared in step S2 and 1 g of polypropylene powder (M w = 200000 Da) were weighed, mixed and ground evenly, then loaded into a fluidized bed reactor, 1 MPa of hydrogen was introduced, and the reaction was carried out at 300 °C until the polyolefin conversion rate reached 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) was measured to be 80.5%.

[0088] Example 5

[0089] In this example, a hydrocracking catalyst was prepared according to the following steps and used for catalytic hydrocracking of polyolefins to aviation fuel:

[0090] S1: Preparation of Catalyst I

[0091] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl2·8H 2 O of 4:1. The mixture was allowed to stand at room temperature for 18 h and then calcined in air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 4).

[0092] S2: Preparation of Catalyst II

[0093] The equal volume impregnation method was adopted (the volume of the nickel nitrate aqueous solution was equal to the pore volume of the nano-silica), and the nickel nitrate aqueous solution was mixed with the nano-silica and ultrasonicated for 2 h to form a homogeneous mixture, which was then calcined at 600 °C for 3 h in a hydrogen atmosphere to obtain the powdery catalyst II, where the Ni loading was 10 wt% (i.e., the Ni content in the catalyst II was 10 wt%).

[0094] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0095] Weigh 100 mg of the catalyst I prepared in step S1, 100 mg of the catalyst II prepared in step S2, and 1 g of the polyolefin mixture powder (composed of 0.5 g of polystyrene with M w = 260000 Da and 0.5 g of polyethylene with M w = 150000 Da), mix and grind them evenly, then load them into a fixed-bed reactor, introduce 1 MPa of hydrogen, and react at 350 °C until the polyolefin conversion rate reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) was measured to be 77.2%.

[0096] Example 6

[0097] In this example, the hydrocracking catalyst was prepared according to the following steps and used for catalytic hydrocracking of polyolefins to aviation fuel:

[0098] S1: Preparation of catalyst I

[0099] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. It was left standing at room temperature for 18 h and calcined at 600 °C for 5 h in an air atmosphere to obtain catalyst I (S / Zr = 6).

[0100] S2: Preparation of catalyst II

[0101] The equal volume impregnation method was adopted (the volume of the nickel nitrate aqueous solution was equal to the pore volume of the nano-silica), and the nickel nitrate aqueous solution was mixed with the nano-silica and ultrasonicated for 2 h to form a homogeneous mixture, which was then calcined at 600 °C for 3 h in a hydrogen atmosphere to obtain the powdery catalyst II, where the Ni loading was 10 wt% (i.e., the Ni content in the catalyst II was 10 wt%).

[0102] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0103] Weigh 50 mg of the catalyst I prepared in step S1, 100 mg of the catalyst II prepared in step S2, and 500 mg of polyethylene powder (M w = 150,000 Da). After mixing and grinding evenly, load them into a fixed-bed reactor, introduce 0.5 MPa of hydrogen, and react at 250 °C until the polyolefin conversion rate reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) is measured to be 60.1%.

[0104] Example 7

[0105] In this example, a hydrocracking catalyst was prepared according to the following steps and used to catalyze the hydrocracking of polyolefins to produce aviation fuel:

[0106] S1: Preparation of catalyst I

[0107] Grind ammonium sulfate and zirconium oxychloride octahydrate at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. Let it stand at room temperature for 18 h and calcine it in an air atmosphere at 600 °C for 5 h to obtain catalyst I (S / Zr = 6).

[0108] S2: Preparation of catalyst II

[0109] Using the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-alumina), mix the nickel nitrate aqueous solution and nano-alumina, sonicate for 2 h to form a homogeneous mixture, and then calcine it in a hydrogen atmosphere at 600 °C for 3 h to obtain the powdery catalyst II, where the Ni loading is 10 wt% (i.e., the Ni content in the catalyst II is 10 wt%).

[0110] S3: Catalytic hydrocracking of polyolefins to produce aviation fuel

[0111] Weigh 50 mg of the catalyst I prepared in step S1, 100 mg of the catalyst II prepared in step S2, and 500 mg of polyethylene powder (M w = 150,000 Da). After mixing and grinding evenly, load them into a fixed-bed reactor, introduce 0.2 MPa of hydrogen, and react at 250 °C until the polyolefin conversion rate reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) is measured to be 75.7%.

[0112] Example 8

[0113] In this example, the hydrocracking catalyst was prepared according to the following steps and used to catalyze the hydrocracking of polyolefins to aviation fuel:

[0114] S1: Preparation of Catalyst I

[0115] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. The mixture was allowed to stand at room temperature for 18 h and then calcined in air at 600 °C for 5 h to obtain Catalyst I (S / Zr = 6).

[0116] S2: Preparation of Catalyst II

[0117] Using the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), the nickel nitrate aqueous solution and nano-silica were mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain a powdery Catalyst II, where the Ni loading is 2 wt% (i.e., the Ni content in Catalyst II is 2 wt%).

[0118] S3: Catalyzing the hydrocracking of polyolefins to aviation fuel

[0119] Weigh 30 mg of Catalyst I prepared in step S1, 120 mg of Catalyst II prepared in step S2, and 1 g of polyethylene powder (M w = 150000 Da). After mixing and grinding evenly, they were loaded into a high-pressure autoclave reactor, 0.2 MPa of hydrogen was introduced, and the reaction was carried out at 250 °C until the polyolefin conversion rate reached 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) was measured to be 68.9%.

[0120] Comparative Example 1

[0121] The difference between this comparative example and Example 1 is only that: in step S1 of this comparative example, Catalyst I was prepared by the impregnation calcination method; the other steps are the same as those in Example 1. Specifically, the hydrocracking catalyst was prepared according to the following steps and used to catalyze the hydrocracking of polyolefins to aviation fuel:

[0122] S1: Preparation of Catalyst I

[0123] Using the equal-volume impregnation method (the volume of the ammonium sulfate aqueous solution is equal to the pore volume of Zr(OH) 4 ), the ammonium sulfate aqueous solution and Zr(OH) 4Mix for 2 h by ultrasound to form a homogeneous mixture, and calcine at 600 °C for 5 h in an air atmosphere to obtain Catalyst I (S / Zr = 6). Its nitrogen adsorption and desorption data are as Figure 6 shown.

[0124] S2: Preparation of Catalyst II

[0125] Adopt the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), mix the nickel nitrate aqueous solution and the nano-silica, and ultrasonicate for 2 h to form a homogeneous mixture. Then, calcine at 600 °C for 3 h in a hydrogen atmosphere to obtain the powdery Catalyst II, where the Ni loading is 2 wt% (i.e., the Ni content in Catalyst II is 2 wt%).

[0126] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0127] Weigh 50 mg of Catalyst I prepared in step S1, 100 mg of Catalyst II prepared in step S2, and 1 g of polyethylene powder (M w = 150000 Da), mix and grind them evenly, then load them into a high-pressure autoclave reactor, introduce 0.2 MPa of hydrogen, and react at 250 °C until the polyolefin conversion rate reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) is measured to be 45.8%.

[0128] Comparing Example 1 and Comparative Example 1, it can be seen that: compared with the impregnation calcination method, using the mixed solid-phase calcination method in the present invention to prepare Catalyst I can improve the selectivity of C 8 ~C 15 hydrocarbons in the polyolefin hydrocracking reaction. The reason for the analysis is that the preparation method will affect the pore structure of Catalyst I (as can be seen from Figure 3 and Figure 6 ). When the mixed solid-phase calcination method is used, the prepared Catalyst I can have a suitable pore structure, which can accommodate and stabilize larger-sized reaction intermediates and products, is beneficial to the formation of high-carbon-number products, and thus makes the C 8 ~C 15 hydrocarbons in the products of the polyolefin hydrocracking reaction have a higher proportion.

[0129] Comparative Example 2

[0130] The difference between this comparative example and Example 1 is only that: in this comparative example, the form of compounding Catalyst I and Catalyst II is not adopted, but the active component (Ni) in Catalyst II is loaded in Catalyst I; the remaining steps are the same as those in Example 1. Specifically, this comparative example prepares a hydrocracking catalyst according to the following steps and uses it to catalyze the hydrocracking of polyolefins to aviation fuel:

[0131] S1: Preparation of Catalyst I

[0132] Ammonium sulfate and zirconium oxychloride octahydrate were ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. The mixture was allowed to stand at room temperature for 18 h and then calcined in an air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 6).

[0133] S2: Loading of Ni

[0134] By the equal - volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of Catalyst I), the nickel nitrate aqueous solution and Catalyst I were mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain a powdered hydrocracking catalyst, where the Ni loading was 2 wt% (i.e., the Ni content in Catalyst II was 2 wt%).

[0135] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0136] 50 mg of the hydrocracking catalyst prepared in step S2 and 1 g of polyethylene powder (M w = 150000 Da) were weighed, mixed and ground evenly, then loaded into a high - pressure autoclave reactor, 0.2 MPa of hydrogen was introduced, and the reaction was carried out at 250 °C until the polyolefin conversion rate reached 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) was measured to be 50.1%.

[0137] Comparing Example 1 and Comparative Example 2, it can be seen that: compared with loading the active component (Ni) in Catalyst II onto Catalyst I, the method of compounding Catalyst I and Catalyst II in the present invention can improve the selectivity of C 8 ~C 15 hydrocarbons in the polyolefin hydrocracking reaction. The reason for the analysis is that the method of compounding Catalyst I and Catalyst II can make the Ni active sites have a large spatial distance from Catalyst I, so that the polyolefin hydrocracking process proceeds along a suitable reaction route, avoiding deep cracking of the products; while if Ni is loaded in Catalyst I, the spatial distance between the active sites in Catalyst I and Ni will be too close, and the content of low - carbon alkanes in the products will be large.

[0138] Comparative Example 3

[0139] The difference between this comparative example and Example 5 is only that: in this comparative example, the mass ratio between Catalyst I and Catalyst II is changed from 1:1 to 1.5:1; the remaining steps are the same as those in Example 5. Specifically, this comparative example prepares a hydrocracking catalyst according to the following steps and uses it to catalyze the hydrocracking of polyolefins to aviation fuel:

[0140] S1: Preparation of Catalyst I

[0141] Ammonium sulfate and zirconium oxychloride octahydrate are ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 4:1. The mixture is allowed to stand at room temperature for 18 h and then calcined in an air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 4).

[0142] S2: Preparation of Catalyst II

[0143] By the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), the nickel nitrate aqueous solution and the nano-silica are mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain a powdery Catalyst II, where the Ni loading is 10 wt% (i.e., the Ni content in Catalyst II is 10 wt%).

[0144] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0145] 120 mg of Catalyst I prepared in step S1, 80 mg of Catalyst II prepared in step S2, and 1 g of a polyolefin mixture powder (composed of 0.5 g of polystyrene with M w = 260000 Da and 0.5 g of polyethylene with M w = 150000 Da) are weighed, mixed and ground evenly, then loaded into a fixed-bed reactor, 1 MPa of hydrogen is introduced, and the reaction is carried out at 350 °C until the polyolefin conversion rate reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) is measured to be 53.8%.

[0146] Comparing Example 5 and Comparative Example 3, it can be seen that: in the hydrocracking catalyst composed of Catalyst I and Catalyst II, when the proportion of Catalyst I is too large, the selectivity of C 8 ~C 15 hydrocarbons in the polyolefin hydrocracking reaction will decrease. The reason may be that the polyolefins undergo deep cracking to produce excessive small-molecule hydrocarbons.

[0147] Comparative Example 4

[0148] The difference between this comparative example and Example 8 is only that: in this comparative example, the mass ratio between Catalyst I and Catalyst II is changed from 0.25:1 to 0.15:1; the remaining steps are the same as those in Example 8. Specifically, this comparative example prepares a hydrocracking catalyst according to the following steps and uses it to catalyze the hydrocracking of polyolefins to aviation fuel:

[0149] S1: Preparation of Catalyst I

[0150] Ammonium sulfate and zirconium oxychloride octahydrate are ground at room temperature to obtain a homogeneous solid mixture with a molar ratio of (NH 4 ) 2 SO 4 to ZrOCl 2 ·8H 2 O of 6:1. It is left standing at room temperature for 18 h and then calcined in an air atmosphere at 600 °C for 5 h to obtain Catalyst I (S / Zr = 6).

[0151] S2: Preparation of Catalyst II

[0152] By the equal-volume impregnation method (the volume of the nickel nitrate aqueous solution is equal to the pore volume of the nano-silica), the nickel nitrate aqueous solution and the nano-silica are mixed and ultrasonicated for 2 h to form a homogeneous mixture, and then calcined in a hydrogen atmosphere at 600 °C for 3 h to obtain a powdery Catalyst II, where the Ni loading is 2 wt% (i.e., the Ni content in Catalyst II is 2 wt%).

[0153] S3: Catalytic hydrocracking of polyolefins to aviation fuel

[0154] Weigh 20 mg of Catalyst I prepared in step S1, 130 mg of Catalyst II prepared in step S2, and 1 g of polyethylene powder (M w = 150000 Da). After mixing and grinding evenly, they are loaded into a high-pressure autoclave reactor, 0.2 MPa of hydrogen is introduced, and the reaction is carried out at 250 °C until the polyolefin conversion rate reaches 100%. The yield of aviation fuel (C 8 ~C 15 hydrocarbons) is measured to be 25.7%.

[0155] Comparing Example 8 and Comparative Example 4, it can be seen that: in the hydrocracking catalyst composed of Catalyst I and Catalyst II, when the proportion of Catalyst II is too large, the selectivity of C 8 ~C 15 hydrocarbons in the polyolefin hydrocracking reaction will decrease. The reason may be the lack of acidic sites, resulting in a decrease in the activity of catalyzing the hydrocracking of polyolefins and the formation of more high-carbon wax-like substances.

[0156] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving the C8~C 15 A hydrocarbon selective method, characterized in that A hydrocracking catalyst is used to catalyze a polyolefin hydrocracking reaction; the hydrocracking catalyst comprises a catalyst I and a catalyst II in a mass ratio of 0.25 to 1:1; the catalyst I is mesoporous sulfided zirconium oxide; the catalyst II comprises a carrier and a Ni element loaded on the carrier; the catalyst I is formed by solid-phase calcination of a mixture of (NH4)2SO4 and ZrOCl2·8H2O.

2. The method according to claim 1, characterized in that The molar ratio of ZrOCl2·8H2O to (NH4)2SO4 is 1:4-10.

3. The method according to claim 1, characterized in that In the catalyst II, the content of Ni single substance is 2-30wt%.

4. The method according to claim 1, characterized in that: The carrier is an inert carrier.

5. The method according to any one of claims 1 to 4, characterized in that: The preparation method of the hydrocracking catalyst comprises the following steps: S1: (NH4)2SO4 and ZrOCl2·8H2O were mixed and ground, and then calcined in an oxygen atmosphere to obtain catalyst I; S2: mixing the nickel source solution and the carrier, and performing reduction calcination to obtain catalyst II; S3: Mixing catalyst I and catalyst II to obtain a hydrocracking catalyst.

6. The method according to claim 5, characterized in that In step S1, the aerobic atmosphere is an air atmosphere.

7. The method according to claim 5, characterized in that In step S1, the calcination temperature is 600-620°C and the calcination time is 4.5-5.5 h.

8. The method according to claim 5, characterized in that In step S2, the reduction calcination process is carried out in a hydrogen atmosphere at a temperature of 600-650° C. for 3-5 h.

9. The method according to claim 1, characterized in that During the catalytic polyolefin hydrocracking reaction, the hydrogen pressure is 0.2-1 Mpa and the reaction temperature is 200-350°C.

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