A hydrocracking catalyst, its application and cracking method

Abstract

A hydrocracking catalyst, its application and cracking method. A hydrocracking catalyst comprises a primary cracking catalyst and an intermediate hydrogenation catalyst, wherein the mass ratio of the primary cracking catalyst to the intermediate hydrogenation catalyst is 0.1-5:1, the primary cracking catalyst is a fixed acid, and the intermediate hydrogenation catalyst is an S-1 molecular sieve encapsulated with an active metal. The hydrocracking catalyst of the present invention is used for the hydrocracking of waste plastics. The series catalytic system of cracking and hydrogenation used in the present invention can achieve the separation of active components and minimize the aggregation and carbon deposition of intermediate products. Through the structural design of the catalyst, the active metal is wrapped in the molecular sieve pores, which greatly improves the stability of the catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid catalysts, and in particular relates to a hydrocracking catalyst, an application thereof and a cracking method. Background Art

[0002] Global plastic production exceeds 300 million tons annually. While this provides convenience, the majority of waste plastics, particularly polyethylene and polypropylene (over 45% of the total), are difficult to degrade under natural conditions. Currently, landfill and incineration are the primary treatment methods, causing severe environmental pollution, significant waste of hydrocarbon resources, and CO2 emissions. Extensive and effective measures are urgently needed to address this issue. Physical recycling yields relatively low-value products, while chemical recycling involves breaking down and reorganizing waste plastics at the molecular level, converting them into high-value chemicals and fuels, or generating monomers to regenerate new plastics, thereby achieving a circular energy conversion of waste plastics.

[0003] The thermal cracking of polyolefins is typically carried out in an oxygen-free or low-oxygen environment at temperatures of 400-800°C. This reaction primarily follows a free radical reaction mechanism. Polyolefins with saturated C-C and C-H bonds often follow a linear random chain scission mechanism / chain end scission mechanism. The reaction process involves disordered and chain end scission of the polymer chain. As a result, the hydrocarbon carbon number distribution in the pyrolysis products is broad (C1-C50), product selectivity is poor, and the products contain a large amount of olefins and paraffin, making direct industrial application difficult. CN112251253.A reports a method for chemical recycling of waste plastics, with a reaction temperature of 500-600°C and a naphtha yield of 70%. By adjusting the catalyst and the tandem reaction method, the low-temperature activation ability of waste plastics can be improved, and the yield and selectivity of the target product can be increased. Summary of the Invention

[0004] The present invention addresses the problems of high conversion temperature and low yield of waste plastics in the prior art. By adjusting appropriate cracking catalysts and hydrogenation catalysts, matching the reaction rates between the two, and preventing the cracking reaction or hydrogenation reaction from being too fast, resulting in a large amount of gas products and easy carbon deposition, the active metal particles are stabilized and the activity of the reaction system is improved, thereby solving the shortcomings of the prior art such as high reaction temperature and low yield, and has good application prospects.

[0005] In a first aspect, the present invention provides a hydrocracking catalyst comprising a primary cracking catalyst and an intermediate hydrogenation catalyst, wherein the mass ratio of the primary cracking catalyst to the intermediate hydrogenation catalyst is 0.1-5:1. The primary cracking catalyst is a solid acid, and the intermediate hydrogenation catalyst comprises an S-1 molecular sieve and an active metal, wherein the active metal is disposed in the pores of the S-1 molecular sieve. By separating the cracking catalyst from the hydrogenation catalyst to form a tandem catalytic system, the hydrogenation catalyst pulls the intermediate olefin product, thereby reducing the product concentration on the cracking catalyst, effectively preventing excessive cracking of waste plastics on the cracking catalyst, which could generate a large amount of gas or cause carbon deposition and deactivation, thereby generating high-value-added liquid products.

[0006] Preferably, the solid acid is selected from one or more of HZSM-5 molecular sieve, Beta molecular sieve, HY molecular sieve, and WO3 / ZrO2. The B acid sites on the solid acid can promote the initial cracking of waste plastics to produce intermediate products such as small molecule olefins and alkanes.

[0007] Preferably, the active metal is selected from one or more of ruthenium, platinum or palladium. The active metal in the present invention has good hydrogenation activity.

[0008] Preferably, the mass ratio of the active metal to the S-1 molecular sieve is 0.05-0.5: 1. In the present invention, the amount of the active metal used within this range can provide good hydrogenation activity.

[0009] Preferably, the preparation method of the intermediate hydrogenation catalyst is: mixing the precursor of the active metal and S-1 molecular sieve, stirring, crystallizing, centrifuging, washing, calcining and reducing to obtain the intermediate hydrogenation catalyst.

[0010] Preferably, the active metal is selected from one or more of ruthenium, platinum or palladium.

[0011] The preparation of S-1 molecular sieve belongs to the existing technology, for example, it can be prepared by mixing tetrapropylammonium hydroxide solution and tetraethyl orthosilicate.

[0012] Preferably, the stirring time is 3-8h, for example, 3-4h, 3-5h, 3-6h, 3-7h and 4-8h. In the present invention, if the stirring time is too short, it is difficult to stir dry, and if the time is too long, the catalyst may be damaged.

[0013] Preferably, the stirring temperature is 20-40°C, for example, 25-40°C, 30-40°C, 35-40°C, 20-35°C, etc. In the present invention, the stirring temperature is basically maintained at room temperature and does not require heating.

[0014] Preferably, the crystallization time is 3-5 days, for example, 3-4 days, 4-5 days, etc. If the crystallization time is too short, it is difficult to generate the required crystal phase. If the time is too long, the crystal particles will grow. The required crystal phase can be achieved within 3-5 days.

[0015] Preferably, the crystallization temperature is 150-180°C, for example, 155-180°C, 160-180°C, 165-180°C, 170-180°C, or 175-180°C.

[0016] Preferably, the washing reagent is selected from one or more of ethanol and water;

[0017] Preferably, the reducing substance is one or more of hydrogen and carbon monoxide;

[0018] Preferably, the reduction temperature is 250-300°C, for example, 260-300°C, 270-300°C, 280-300°C, 290-300°C, etc.

[0019] Preferably, the reduction pressure is 1-5 MPa, for example, 2-5 MPa, 3-5 MPa, 4-5 MPa, etc. In the present invention, if the pressure is lower than 1 MPa, the raw materials are difficult to react, and if the pressure is higher than 5 MPa, the residual solid content will increase.

[0020] Preferably, the reduction time is 30-240 min, for example, 40-240 min, 60-240 min, 80-240 min, 100-240 min, 120-240 min, 140-240 min, 160-240 min, 180-240 min, 200-240 min, 220-240 min, etc.

[0021] The second aspect of the present invention provides the above-mentioned hydrocracking catalyst for use in the hydrocracking of waste plastics.

[0022] The third aspect of the present invention provides a method for cracking waste plastics using the above-mentioned hydrogenation catalyst, wherein the waste plastics are first cracked using a primary cracking catalyst, and then hydrogenated using an intermediate hydrogenation catalyst.

[0023] Preferably, the cracking temperature is 200-240° C., for example, 210-240° C., 220-240° C., or 230-240° C., which is significantly lower than the conventional cracking temperature (>360° C.). Preferably, the cracking time is 40-150 min, for example, 50-150 min, 60-150 min, 70-150 min, 80-150 min, 90-150 min, 100-150 min, 110-150 min, 120-150 min, 130-150 min, or 140-150 min.

[0024] Preferably, the hydrogen is reacted with hydrogen during the hydrogenation. Preferably, the pressure of the hydrogen is 1-4 MPa, for example, 2-4 MPa, 3-4 MPa, etc.

[0025] Preferably, the hydrogenation temperature is 200-240° C., for example, 210-240° C., 220-240° C., or 230-240° C., which is lower than the conventional hydrogenation temperature (higher than 250° C.).

[0026] Preferably, the hydrogenation time is 40-150 min, for example, 50-150 min, 60-150 min, 70-150 min, 80-150 min, 90-150 min, 100-150 min, 110-150 min, 120-150 min, 130-150 min, or 140-150 min.

[0027] Preferably, the hydrogen is reacted with hydrogen during the hydrogenation. Preferably, the pressure of the hydrogen is 1-4 MPa, for example, 2-4 MPa, 3-4 MPa, etc.

[0028] As described above, the hydrocracking catalyst, application and cracking method provided by the present invention have the following beneficial effects:

[0029] 1) This invention utilizes a tandem cracking and hydrogenation catalytic system. The physical space between the cracking and hydrogenation catalysts allows for separation of the active components, minimizing the aggregation of intermediates and carbon deposition. The catalyst's structural design encapsulates the active metal within the molecular sieve pores, significantly improving catalyst stability.

[0030] 2) This invention utilizes low levels of active metals to achieve low-temperature activation of waste plastics, significantly reducing the pyrolysis temperature (>360°C) compared to traditional pyrolysis. This allows for efficient conversion of raw materials at lower temperatures, including naphtha (with selectivity up to 98% for C5-C11) and gasoline and diesel components (with selectivity up to 95% for C6-C18). Different product compositions can be selectively generated as needed. The catalyst preparation process is simple, and the reaction process is convenient and controllable, making it suitable for the chemical recycling of various polyethylene and polypropylene waste plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the TEM image of the S-1 molecular sieve wrapped with active metal in Example 4. DETAILED DESCRIPTION

[0032] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different perspectives and applications without departing from the spirit of the present invention. It should be noted that any process equipment or devices not specifically noted in the following examples are conventional equipment or devices in the art.

[0033] Example 1

[0034] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed. A certain amount of 0.1 mol / L chloroplatinic acid was added to achieve a mass ratio of Pt to S-1 molecular sieve of 0.05. The mixture was then stirred at 20°C for 8 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100mL hydrothermal kettle and crystallized in a 150°C oven for 5 days. After cooling naturally to room temperature, the solution was washed three times with ethanol and water, dried, and calcined in air at 550°C for 6 hours to obtain the Pt-coated S-1 molecular sieve. This was then reduced with H2 at 250°C for 2 hours to obtain an intermediate hydrogenation catalyst.

[0035] Using waste polyethylene as the raw material, 0.05 g each of HZSM-5 and intermediate hydrogenation catalyst were reacted at 240°C and a H₂ pressure of 5 MPa for 240 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis determined the liquid composition, and the product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁ and C₆₁ ...

[0036] Example 2

[0037] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed, and a certain amount of 0.1 mol / L palladium nitrate was added to achieve a mass ratio of palladium to S-1 molecular sieve of 0.5. The mixture was then stirred at 40°C for 3 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100mL hydrothermal kettle and crystallized in an oven at 180°C for 3 days. After naturally cooling to room temperature, the solution was washed three times with ethanol and water, dried, calcined in air at 550°C for 6 hours, and reduced with H2 at 280°C for 2 hours to obtain the palladium-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0038] Using waste polypropylene as the raw material, 0.05 g each of Beta molecular sieve and intermediate hydrogenation catalyst were reacted at 200°C and 3 MPa of H₂ pressure for 30 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis determined the liquid composition, and the product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁ and C₆₁ ...

[0039] Example 3

[0040] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed, and a certain amount of 0.1 mol / L ruthenium acetate was added to make the mass ratio of ruthenium to S-1 molecular sieve 0.3%. The solution was then stirred at 30°C for 6 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100mL hydrothermal kettle and crystallized in a 170°C oven for 4 days. After naturally cooling to room temperature, it was washed three times with ethanol and water. After drying, it was calcined in air at 550°C for 6 hours and reduced with H2 at 300°C for 2 hours to obtain the ruthenium-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0041] Using waste polypropylene as the raw material, 0.05 g of each HY molecular sieve and intermediate hydrogenation catalyst were reacted at 230°C and 1 MPa of H₂ pressure for 180 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis was used to determine the liquid composition. The product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁ and C₆₁ ...

[0042] Example 4

[0043] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed with a certain amount of 0.1 mol / L chloroplatinic acid, so that the mass ratio of platinum to S-1 molecular sieve was 0.2. The solution was then stirred at 20°C for 6 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100mL hydrothermal kettle and crystallized in a 170°C oven for 3 days. After natural cooling to room temperature, it was washed three times with ethanol and water, dried, calcined in air at 550°C for 6 hours, and reduced with H2 at 300°C for 2 hours to obtain the Pt-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0044] Using waste polyethylene as the raw material, 0.05 g each of Beta molecular sieve and intermediate hydrogenation catalyst were used, and the reaction was carried out at 240°C and 3 MPa of H₂ pressure for 120 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis was used to determine the liquid composition. The product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁₁ and C₆₁ ...

[0045] Example 5

[0046] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed with a certain amount of 0.1 mol / L chloroplatinic acid, so that the mass ratio of platinum to S-1 molecular sieve was 0.2. The solution was then stirred at 20°C for 6 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100mL hydrothermal kettle and crystallized in a 170°C oven for 3 days. After natural cooling to room temperature, it was washed three times with ethanol and water, dried, calcined in air at 550°C for 6 hours, and reduced with H2 at 300°C for 2 hours to obtain the Pt-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0047] Using waste polyethylene as the raw material, 0.05 g each of Beta molecular sieve and intermediate hydrogenation catalyst were used, and the reaction was carried out at 240°C and 3 MPa of H₂ pressure for 120 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis was used to determine the liquid composition. The product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁₁ and C₆₁ ...

[0048] Example 6

[0049] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed. A certain amount of 0.1 mol / L chloroplatinic acid was added to achieve a platinum to S-1 molecular sieve mass ratio of 0.3. The solution was then stirred at 30°C for 6 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100mL hydrothermal kettle and crystallized in a 170°C oven for 4 days. After naturally cooling to room temperature, it was washed three times with ethanol and water. After drying, it was calcined in air at 550°C for 6 hours and reduced with H2 at 300°C for 2 hours to obtain the Pt-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0050] Using waste polyethylene as the raw material, 0.05 g each of HZSM-5 molecular sieve and intermediate hydrogenation catalyst were reacted at 240°C and 3 MPa of H₂ pressure for 120 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis determined the liquid composition, and the product content was determined based on the peak areas of the various substances and the ratio of the C₂ internal standard. The total amounts of C₅-C₁₁ and C₆-C₁ ...

[0051] Example 7

[0052] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed. A certain amount of 0.1 mol / L chloroplatinic acid was added to adjust the mass ratio of Pt to S-1 molecular sieve to 0.3. The mixture was then stirred at 30°C for 6 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100 mL hydrothermal kettle and crystallized in a 140°C oven for 10 days. After naturally cooling to room temperature, the solution was washed three times with ethanol and water, dried, calcined in air at 550°C for 6 hours, and reduced with H2 at 250°C for 2 hours to obtain the Pt-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0053] Using waste polyethylene as the raw material, 0.1 g of Beta molecular sieve and intermediate hydrogenation catalyst were used, and the reaction was carried out at 250°C and 3 MPa of H₂ pressure for 120 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis was used to determine the liquid composition. The product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁ and C₆₁ ...

[0054] Example 8

[0055] First, a 25% mass concentration of tetrapropylammonium hydroxide solution and tetraethyl orthosilicate were mixed. A certain amount of 0.1 mol / L chloroplatinic acid was added to adjust the mass ratio of Pt to S-1 molecular sieve to 0.3. The mixture was then stirred at 30°C for 6 hours until the solution became completely colorless and transparent. The solution was then transferred to a 100 mL hydrothermal kettle and crystallized in a 140°C oven for 10 days. After naturally cooling to room temperature, the solution was washed three times with ethanol and water, dried, calcined in air at 550°C for 6 hours, and reduced with H2 at 250°C for 2 hours to obtain the Pt-coated S-1 molecular sieve, thus obtaining an intermediate hydrogenation catalyst.

[0056] Using waste polyethylene as the raw material and 0.1 g of hydrogenation catalyst, the reaction was carried out at 240°C and 3 MPa of H₂ pressure for 120 minutes. After the reaction, the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis was used to determine the liquid composition. The product content was determined based on the peak areas of the various substances and the ratio of the C₂₂ internal standard. The total amounts of C₅₁₁ and C₆₁ ...

[0057] Example 9

[0058] Using waste polyethylene as the raw material and 0.1 g of Beta molecular sieve, the reaction was carried out at a temperature of 240°C and a hydrogen pressure of 3 MPa for 120 minutes. After the reaction, the masses of the gas, liquid, and solid components were weighed and the liquid yield was calculated. GC / MS analysis was used to determine the liquid composition. The relevant product content was determined based on the peak areas of different substances and the ratio of the C22 internal standard. The total amount of C5-C11 and C6-C18 products was calculated, and the product selectivity was calculated. The results are shown in Table 1.

[0059] Table 1 Results of Examples 1-9

[0060] Raw material conversion rate% Liquid yield% C5-C11 selectivity % C6-C18 selectivity % Example 1 99 91 —— 96 Example 2 99 79 96 —— Example 3 99 91 —— 96 Example 4 96 90 98 —— Example 5 99 86 96 —— Example 6 95 89 —— 95 Example 7 98 89 96 Unable to generate Example 8 5 3 35 55 Example 9 15 14 78 10

[0061] From the results of the examples, it can be seen that the catalyst of the invention has good activity in catalytic conversion of waste plastics. Figure 1 The TEM image of the active metal wrapped in the S-1 molecular sieve in Example 4 is given, which shows that the catalyst can wrap the active metal in the pores, thereby increasing the stability of the catalyst to a certain extent.

[0062] At the same time, it can be seen from Examples 1-6 that the products can be switched between different products according to the change of the catalyst ratio to generate naphtha (C5-C11 selectivity up to 98%) or gasoline and diesel components (C6-C18 selectivity up to 95%).

[0063] Furthermore, it should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before or after the combination step, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified. It should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the presence of other devices / apparatuses before or after the combination device / apparatus, or the insertion of other devices / apparatuses between two explicitly mentioned devices / apparatuses, unless otherwise specified. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the present invention.

Claims

1. A hydrocracking catalyst, characterized in that The invention comprises a primary cracking catalyst and an intermediate hydrogenation catalyst, wherein the mass ratio of the primary cracking catalyst to the intermediate hydrogenation catalyst is 0.1-5:1, the primary cracking catalyst is a solid acid, and the intermediate hydrogenation catalyst comprises an S-1 molecular sieve and an active metal, wherein the active metal is arranged in the pores of the S-1 molecular sieve.

2. The hydrocracking catalyst according to claim 1, characterized in that The solid acid is selected from one or more of HZSM-5 molecular sieve, Beta molecular sieve, HY molecular sieve and WO3 / ZrO2.

3. The hydrocracking catalyst according to claim 1, characterized in that The active metal is selected from one or more of ruthenium, platinum or palladium.

4. The hydrocracking catalyst according to claim 1, characterized in that The mass ratio of the active metal to the S-1 molecular sieve is 0.05-0.5:

1.

5. The hydrocracking catalyst according to claim 1, characterized in that The preparation method of the intermediate hydrogenation catalyst comprises: mixing the precursor of the active metal with a silicon precursor solution for preparing S-1 molecular sieve and a template agent, stirring, crystallizing, centrifuging, washing, calcining and reducing to obtain the intermediate hydrogenation catalyst.

6. The hydrocracking catalyst according to claim 5, characterized in that The precursor of the active metal is selected from one or more of nitrates, acetates or chlorates of the active metal.

7. The hydrocracking catalyst according to claim 5, characterized in that Include one or more of the following technical features: A1) The stirring time is 3-8h; A2) the stirring temperature is 20-40°C; A3) the crystallization time is 3-5 days; A4) the crystallization temperature is 150-180°C; A5) the washing reagent is selected from one or more of ethanol and water; A6) The substance used for the reduction is one or more of hydrogen and carbon monoxide; A7) the reduction temperature is 250-300°C; A8) The reduction pressure is 1-5 MPa; A9) The reduction time is 30-240 min.

8. The hydrocracking catalyst according to any one of claims 1 to 7, characterized in that Used for hydrocracking of waste plastics.

9. A method for cracking waste plastics with a hydrogenation catalyst, characterized in that: The waste plastics are first cracked using the preliminary cracking catalyst as claimed in any one of claims 1 to 7, and then the waste plastics are hydrogenated using the intermediate hydrogenation catalyst as claimed in any one of claims 1 to 7.

10. The method for hydrogenating catalyst cracking waste plastics according to claim 9, characterized in that: Include at least one of the following technical features: B1) the cracking temperature is 200-240°C; B2) the lysis time is 40-150 min; B3) the hydrogenation temperature is 200-240°C; B4) the hydrogenation time is 40-150min; B5) reacting with hydrogen during the hydrogenation, wherein the pressure of the hydrogen is 1-4 MPa.

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