Method for efficiently preparing saturated chain hydrocarbon from waste polyolefin

Abstract

The invention discloses a method for efficiently preparing saturated chain hydrocarbon from waste polyolefin. The method comprises the following steps: (1) taking titanium oxide as a carrier, dissolving an active metal-containing precursor in water to form a precursor solution, and loading the precursor solution on the surface of the titanium oxide carrier in a dipping manner to obtain a precursor-loaded catalyst precursor; (2) placing the catalyst precursor in a graphite pipe provided with a Joule heating device, applying instantaneous current, rapidly heating to a target temperature, and completing calcination treatment to construct a catalyst; and (3) jointly placing the catalyst and the waste polyolefin raw material in a hydrogen atmosphere for hydrogenolysis reaction to obtain a product mainly containing liquid hydrocarbon. According to the invention, rapid construction of the high-performance catalyst and application of the high-performance catalyst in directional conversion of waste polyolefin are realized through the steps of impregnation loading, flash Joule calcination, high-efficiency low-consumption hydrogenolysis and the like.

Description

Technical Field

[0001] This invention relates to the field of waste plastic recycling and resource recycling technology, and in particular to a method for efficiently preparing saturated chain hydrocarbons from waste polyolefins. Background Technology

[0002] Due to their stable molecular skeletons and difficulty in natural degradation, the efficient conversion and resource utilization of waste polyolefins has always been an important issue in the field of solid waste treatment. Converting waste polyolefins into high-value-added hydrocarbon products through catalytic cracking, hydrogenolysis, or hydrocracking is considered an effective way to achieve their high-value utilization. Among these methods, catalysts play a decisive role in reaction activity, product selectivity, and operational stability.

[0003] Existing technologies generally employ supported metal catalyst systems, such as loading noble metals onto the surface of oxide supports to achieve selective C-C bond cleavage. However, such catalysts typically rely on multi-step preparation processes involving impregnation, calcination, and reduction, resulting in long preparation cycles, high energy consumption, and difficulty in precisely controlling metal-support interactions, thus affecting catalytic performance and reusability. Furthermore, traditional high-temperature calcination processes primarily rely on fossil fuel heating, which is detrimental to reducing overall carbon emissions.

[0004] With the energy structure moving towards low-carbon and electrification, the direct use of renewable electricity to drive the synthesis of materials and the preparation of catalysts has gradually attracted attention. There is an urgent need to propose new methods for synthesizing catalysts using electricity. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the efficient preparation of saturated chain hydrocarbons from waste polyolefins. This invention proposes a method for preparing catalysts that can complete catalyst preparation and structural regulation in a very short time through electric drive, and significantly improve catalytic performance, so as to meet the needs of the development of efficient conversion and low-carbonization processes for waste polyolefins.

[0006] This invention is achieved through the following technical solutions:

[0007] This invention protects a method for efficiently preparing saturated chain hydrocarbons from waste polyolefins, comprising the following steps:

[0008] (1) Impregnation loading: Using titanium oxide as a support, a precursor containing an active metal is dissolved in water to form a precursor solution. The active metal is selected from one or two of platinum (Pt), nickel (Ni) and ruthenium (Ru). The precursor solution is loaded onto the surface of the titanium oxide support by impregnation to obtain a catalyst precursor loaded with the precursor, which is then dried.

[0009] (2) Flash Joule calcination: The dried catalyst precursor obtained in step (1) is placed in the graphite tube of the flash Joule heating device, and an instantaneous current is applied to rapidly heat the catalyst precursor to the target temperature under the action of the current and complete the calcination treatment. The heating time of flash Joule calcination is 0.1-2.0 s, and the target temperature is 300℃-1500℃, thereby constructing a catalyst with small metal clusters, Ru semi-encapsulated anti-sintering, and enhanced metal-support interaction.

[0010] (3) Low-consumption hydrogenolysis reaction: The catalyst obtained in step (2) and the waste polyolefin raw material are placed together in a hydrogen atmosphere to carry out hydrogenolysis reaction to obtain a mixed product of mixed gas and liquid hydrocarbon;

[0011] This invention achieves the rapid construction of high-performance catalysts and their application in the directional conversion of waste polyolefins through steps such as impregnation loading, flash Joule calcination, and efficient and low-consumption hydrogenolysis.

[0012] The catalyst proposed in this invention replaces the traditional high-temperature, long-term calcination process with flash Joule calcination, significantly shortening the catalyst preparation cycle and reducing energy consumption. This facilitates the high dispersion of ruthenium species and the regulation of the metal-support interface structure. Simultaneously, non-equilibrium heating creates numerous oxygen vacancies on TiO2, promoting adsorption and electron transfer, thereby improving the catalyst's activity and selectivity in the hydrogenolysis of waste polyolefins. Furthermore, Ru is absorbed by TiO2... x The semi-encapsulated structure prevents Ru clusters from sintering during hydrogenolysis and catalyst recovery, improving catalyst reuse performance. It also enables efficient breaking of carbon-carbon bonds in the main chain of waste polyolefin molecules under conditions of lower hydrogen consumption and shorter reaction time, yielding products mainly composed of liquid hydrocarbons.

[0013] Preferably, the titanium oxide in step (1) is anatase phase titanium oxide. The concentration of the precursor solution is 15 mg / mL.

[0014] In step (1), the impregnation, loading, and drying processes are carried out under conditions of vibration, reduced pressure, or a combination of vibration and reduced pressure to improve the uniformity of the ruthenium precursor distribution on the support surface. The catalyst precursor with the supported precursor is thoroughly dried and pulverized for later use.

[0015] In step (1), ruthenium-containing precursors include ruthenium nitrite, ruthenium chloride, and ruthenium nitrate, platinum-containing precursors include chloroplatinic acid and platinum nitrate, and nickel-containing precursors include nickel chloride and ruthenium nitrate.

[0016] The impregnation-loading to complete drying process proposed in this invention can be completed in a vortex oscillation evaporation device. The negative pressure environment can accelerate the evaporation of water in the solution, shorten the time required, and the high-frequency oscillation can ensure the uniformity of the ruthenium precursor loading.

[0017] Preferably, the vortex evaporation device is set to a constant temperature of 60°C, a constant pressure of 0.2 bar, and an oscillation frequency of 300 RPM, which can evaporate the moisture within 2 hours.

[0018] Preferably, the flash Joule calcination process in step (2) is carried out under an inert atmosphere, wherein the inert atmosphere is selected from argon and / or nitrogen.

[0019] The flash Joule calcination process proposed in this invention uses electricity as a direct energy input, resulting in a short heating time, high energy utilization efficiency, and the ability to be combined with renewable energy power systems, thereby significantly reducing overall carbon emissions. The resulting catalyst has smaller metal clusters, Ru semi-encapsulated anti-sintering properties, a higher oxygen vacancy ratio, and stronger metal-support interaction, exhibiting higher activity and selectivity in the hydrogenolysis of waste polyolefins.

[0020] Preferably, the flash Joule calcination process is performed under an argon atmosphere, with the target temperature set at 300°C. o C, 600 o C, 900 o C, 1200 o C, 1500 o C, the applied voltage-current are: 12V-50A, 12V-120A, 15V-120A, 20V-90A, 20V-120A respectively. The flash Joule calcination process uses electrical energy as the direct energy input and can be powered by renewable energy sources.

[0021] Preferably, in the catalyst described in step (2), the loading of active metal on the titanium oxide support is 0.5%-15%, and the average particle size of the active metal is 0.5-4.0 nm.

[0022] Further preferred, in the catalyst described in step (2), the loading of active metal on the titanium oxide support is 1%-10%, the average particle size of the active metal is 1.1±0.3 nm, and it is highly dispersed.

[0023] Further preferred, the active metal in the catalyst described in step (2) is loaded onto the titanium oxide support at a rate of 5%.

[0024] Preferably, the mass ratio of the waste polyolefin raw material to the catalyst in step (3) is 5-40:1.

[0025] Further preferred, the mass ratio of the waste polyolefin raw material to the catalyst in step (3) is 10:1.

[0026] Preferably, the conditions for the hydrogenolysis reaction in step (3) are: a reaction temperature of 180℃-300℃, an initial hydrogen pressure of 1-5 MPa, and a reaction time of 1-6 h. In this invention, a stirring speed of 500 RPM is set for the hydrogenolysis reaction.

[0027] Further preferred, the conditions for the hydrogenolysis reaction in step (3) are: reaction temperature of 250°C, initial hydrogen pressure of 3 MPa, and reaction time of 2 h.

[0028] Preferably, the waste polyolefin raw material in step (3) is selected from polyethylene and / or polypropylene.

[0029] Preferably, the liquid hydrocarbon in step (3) is a saturated alkane in the C5-C35 range.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. This invention replaces the traditional high-temperature, long-term calcination process with flash Joule calcination, significantly shortening the catalyst preparation cycle and reducing energy consumption; it facilitates the high dispersion of metal species, semi-encapsulated metal clusters to prevent sintering, and the regulation of the metal-support interface structure, thereby improving the activity and selectivity of the catalyst in the hydrogenolysis of waste polyolefins; the use of Ru-Ni and Ru-Pt bimetallic calcination to form an alloy structure can further suppress the reaction of C-C bond breaking to generate methane; while reducing the reaction time, it achieves efficient conversion of waste polyolefins, making it suitable for complex raw material systems; the preparation process is electrified, the process is simple, and it has strong scalability, meeting the industrial application requirements of low-carbonization and sustainable development.

[0032] 2. The hydrogenolysis reaction proposed in this invention can basically complete the conversion of waste polyolefins in a reaction time of 4 hours, and the yield of the obtained liquid phase oil is up to 92.0 wt.%, while the methane yield is only 3.8 wt.%. Attached Figure Description

[0033] Figure 1 This is a TEM image of the catalyst prepared in Example 1.

[0034] Figure 2 This is a TEM image of the catalyst prepared in Example 2.

[0035] Figure 3 This is a TEM image of the catalyst prepared in Comparative Example 1.

[0036] Figure 4 This is a semi-encapsulated TEM image of the catalyst prepared in Example 1. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are considered to be commercially available through conventional markets. The flash Joule heating device proposed in this invention was purchased from Hefei In-situ Technology Co., Ltd., model CIS-JH3.3-p.

[0038] The FJH (Flash Joule Heating) device proposed in this invention consists of a Joule-heated graphite tube, an argon cylinder, and a water-cooled cooling system (10℃-20℃). The reaction temperature is measured by an infrared temperature probe (250℃-2000℃).

[0039] In the following examples, the product obtained from the method for efficiently preparing saturated chain hydrocarbons from waste polyolefins is analyzed to determine its content. The specific process is as follows:

[0040] (1) The gas to be tested was detected by GC-MS (gas chromatography-mass spectrometry) to determine the content of each component. The instrument includes an FID detector and a TCD detector, and qualitative and quantitative analysis was performed using a program calibrated with a standard mixed gas. The sample can be injected when the temperature (40°C) is ready, and the injection time is approximately 40 s.

[0041] (2) The test liquid was analyzed using GC-FID (Gas Chromatography-Flame Ionization Detector), and the product was qualitatively and quantitatively analyzed using a certified C7-C40 n-alkane standard mixture. The column oven temperature program was as follows: 50°C for 10 min, then increased to 100°C at 5°C / min and held for 3 min, then increased to 220°C at 5°C / min, and finally increased to 310°C at 10°C / min and held for 5 min. In addition, the product types were classified according to the carbon number range: gasoline (C5-C12), diesel (C9-C22), and lubricating oil (C20-C35).

[0042] (3) According to the law of conservation of mass, the formula for calculating the yield of the product is as follows:

[0043] Eq.(1)

[0044] Eq.(2)

[0045] Eq.(3)

[0046] Example 1

[0047] The Ru / TiO2 catalyst was synthesized using the flash Joule calcination method, and the specific process is as follows:

[0048] (1) Measure 3.335 mL of a 15 mg / mL ruthenium nitrosamine solution and place it in a magnetic rotor. Turn on the magnetic stirrer to make the rotor stir evenly. Then, slowly pour 1 g of TiO2 powder (anatase phase) into the precursor solution to obtain a uniformly loaded slurry;

[0049] (2) Transfer the slurry to a vortex evaporator, check its airtightness, and set it to 60°C. o The instrument was started at a constant temperature of C, constant pressure of 0.2 bar, and oscillation frequency of 300 RPM; after the slurry evaporated to dryness, it was transferred to an 80°C inlet. o The solid was dried overnight in an oven at C to completely remove internal moisture, resulting in a blocky solid. The blocky solid was then placed in a mortar and carefully ground into a fine white-gray powder, which became the catalyst precursor particles for the supported precursor.

[0050] (3) Place the catalyst precursor particles into the graphite tube of the FJH (Flash Joule Heating) device and start the FJH device at the target temperature of 600℃, voltage of 12 V and current of 120 A. After the temperature cools down, take it out to obtain the prepared Ru / TiO2 catalyst, labeled FH600.

[0051] like Figure 1 As shown, the Ru clusters have a particle size of 1.1 ± 0.3 nm. Smaller Ru clusters in FH600 facilitate the breaking of internal C-C bonds, resulting in a lower average carbon number in the generated liquid-phase product. Figure 4 As shown, the unique semi-encapsulated structure formed by FH600 is beneficial to improving the catalyst's anti-sintering performance.

[0052] The catalyst FH600 was used for the hydrogenolysis of LDPE (low-density polyethylene). The specific steps are as follows:

[0053] (1) Weigh 0.1 g of catalyst FH600 and 1 g of low-density polyethylene respectively and place them at the bottom of the reactor, and place an additional magnetic rotor; after the device is connected to the hydrogen cylinder, first fill it with 2 MPa of hydrogen, then close the gas path and slowly exhaust the gas to near atmospheric pressure. Repeat the operation 4 times to completely exhaust the air in the device.

[0054] (2) Charge the apparatus with 3 MPa of hydrogen, then set the target temperature to 250°C and the holding time to 2 h, and start the heating program. When the apparatus is heated to 150°C, start the magnetic stirrer and set the stirring speed to 500 RPM. After the reaction is complete and the apparatus is completely cooled, first use a gas bag to collect the reaction gas, and then use 5 mL of cyclohexane to dissolve and collect the liquid product.

[0055] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 1.

[0056] Table 1 Example 2

[0057] The preparation process of the Ru / TiO2 catalyst is the same as in Example 1, except that the FJH device is started at a target temperature of 300°C, a voltage of 12 V and a current of 50 A to obtain catalyst FH300.

[0058] like Figure 2 As shown, the Ru clusters have a particle size of 3.7 ± 0.8 nm.

[0059] The catalyst FH300 was used for the hydrogenolysis of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0060] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 2.

[0061] Table 2 Example 3

[0062] The preparation process of Ru / TiO2 catalyst is the same as in Example 1, except that the FJH device is started at a target temperature of 900℃, a voltage of 15 V and a current of 120 A to obtain catalyst FH900.

[0063] The catalyst FH900 was used for the hydrogenolysis of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0064] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 3.

[0065] Table 3 Example 4

[0066] The preparation process of Ru / TiO2 catalyst is the same as in Example 1, except that: the FJH device is started at a target temperature of 1200℃, a voltage of 20 V and a current of 90 A to obtain catalyst FH1200.

[0067] The catalyst FH1200 was used for the hydrogenolysis of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0068] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 4.

[0069] Table 4 Example 5

[0070] The preparation process of Ru / TiO2 catalyst is the same as in Example 1, except that the FJH device is started at a target temperature of 1500℃, a voltage of 20 V and a current of 120 A to obtain catalyst FH1500.

[0071] The catalyst FH1500 was used for the hydrogenolysis of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0072] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 5.

[0073] Table 5 Comparative Example 1

[0074] Similar to Example 1, except that in step (3), the FJH (flash Joule heating) device is replaced with a conventional vertical tube furnace, the target temperature is set to 300℃, the heating rate is 10℃ / min, and the temperature is immediately cooled after reaching the target temperature. The resulting Ru / TiO2 catalyst is labeled CH300.

[0075] like Figure 3 As shown, the Ru clusters have a particle size of 3.9 ± 1.0 nm.

[0076] The catalyst CH300 was used for the hydrogenolysis of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0077] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 6.

[0078] Table 6 Comparative Example 2

[0079] Similar to Comparative Example 1, except that: the target temperature was set to 600℃, the heating rate was 10℃ / min, and the temperature was immediately lowered after reaching the target temperature. The resulting product was the prepared Ru / TiO2 catalyst, labeled CH600.

[0080] The catalyst CH600 was used for the hydrogenolysis of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0081] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 7.

[0082] Table 7 Comparative Example 3

[0083] Same as Comparative Example 1, except that: the target temperature is set at 900 °C, the heating rate is 10 °C / min, and it is immediately cooled after reaching the target temperature. The obtained Ru / TiO2 catalyst is marked as CH900 after being taken out.

[0084] The catalyst CH900 was used for the hydrocracking of LDPE (low-density polyethylene), and the specific steps were the same as in Example 1.

[0085] The product yields, liquid product compositions, and gas product compositions obtained are shown in Table 8:

[0086] Table 8

[0087] There are significant differences in the product yields between Examples 1-5 and Comparative Examples 1-3, which are reflected in: in Example 1, the catalyst FH600 showed the highest liquid yield, gasoline yield, and diesel mass yield of 87.1%, 55.4%, and 60.3%, respectively, all higher than those of Comparative Examples 1-3; as the calcination temperature further increased, different degrees of performance decay occurred in both Examples 1-5 and Comparative Examples 1-3, but the performance decay in Examples 1-5 occurred at 600 °C - 900 °C, significantly higher than 300 °C - 600 °C of Comparative Examples 1-3; the catalysts with the highest yields were CH300, FH300, and FH600, but their liquid product carbon number distributions were different, among which the peak carbon numbers were FH600 < FH300 < CH300, indicating that the catalysts proposed in this invention have higher selectivity for low-carbon number liquid products.

[0088] The reasons for the differences in the product yields between Examples 1-5 and Comparative Examples 1-3 are as follows:

[0089] 1. The heating time of FJH is extremely short compared to the traditional calcination method, controlling the phase transformation of the carrier TiO2 on the time scale, and thus it can withstand a higher calcination temperature.

[0090] 2. At a higher calcination temperature, Ru / TiO2 can be regulated at the particle size level and the electronic level, thereby affecting the catalytic performance. At the particle size level, FJH withstands a higher temperature, which is conducive to the formation of smaller Ru clusters, and smaller Ru clusters tend to break the internal C-C bonds during the reaction, having a higher degree of cleavage for polyolefins, and showing a lower peak carbon number in the products.

[0091] 3. At the electronic level, FJH withstands a higher temperature, which is conducive to the formation of a stronger MSI (metal-support interaction) effect, and a stronger MSI means a higher hydrogen storage capacity around the active sites, which enables the active sites to selectively break the internal C-C bonds, having a higher degree of cleavage for polyolefins, and showing a lower peak carbon number in the products.

[0092] 4. FH600, i.e., the Ru / TiO2 system, under the heat treatment of FJH impact at 600℃, can make the Ru cluster particle size the smallest and the MSI effect the strongest. In the examples, it shows the highest liquid phase yield, gasoline yield and diesel yield.

[0093] In summary, compared with traditional calcination methods, the Ru / TiO2 catalyst prepared by the method of this invention can significantly improve the yield of oil products, especially gasoline and diesel, during the catalytic hydrogenolysis of waste polyolefins. Furthermore, the Ru / TiO2 catalyst exhibits the best effect on improving the yield of oil products, particularly gasoline and diesel, when calcined using FH600. Example 6

[0094] Similar to Example 1, except that the Pt / TiO2 catalyst was synthesized using a flash Joule calcination method, with a tetraammineplatinum nitrate solution as the precursor at a concentration of 15 mg / mL, platinum loading on the titanium oxide support at 5%, and a calcination temperature of 600°C. The Pt / TiO2 catalyst was then used for the hydrogenolysis of LDPE (low-density polyethylene), following the same steps as in Example 1.

[0095] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 9.

[0096] Table 9 Example 7

[0097] Similar to Example 1, except that the Ru-Pt / TiO2 catalyst was synthesized using a flash Joule calcination method. The precursor was a mixed solution of ruthenium nitrosamine nitrate and platinum tetraamminenitrate, with a ruthenium:platinum weight ratio of 1:1. The loading of both ruthenium and platinum on the titanium oxide support was 2.5%, and the calcination temperature was 600°C. The Ru-Pt / TiO2 catalyst was used for the hydrogenolysis of LDPE (low-density polyethylene), following the same steps as in Example 1.

[0098] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 10.

[0099] Table 10 Example 8

[0100] Similar to Example 1, except that the Ru-Ni / TiO2 catalyst was synthesized using a flash Joule calcination method. The precursor was a mixed solution of ruthenium nitrosamine and nickel nitrate, with a ruthenium:nickel weight ratio of 1:1. The loading of both ruthenium and nickel on the titanium oxide support was 2.5%, and the calcination temperature was 600°C. The Ru-Ni / TiO2 catalyst was used for the hydrogenolysis of LDPE (low-density polyethylene), following the same steps as in Example 1.

[0101] The yields, liquid product compositions, and gaseous product compositions of the collected products are shown in Table 11.

[0102] Table 11 Based on the comparison of the aforementioned examples, it can be seen that the Ru / TiO2 catalyst prepared by the FH600 method can significantly improve the yield of oil products, especially gasoline and diesel. Comparing Example 1 with Examples 6-8, it is evident that Ru-Pt / TiO2 and Ru-Ni / TiO2, based on the high gasoline and diesel yields of Ru / TiO2, further reduce the methane yield. This is because Ru-Pt and Ru-Ni alloys promote carbon chain adsorption and intermediate desorption, thereby further inhibiting the breaking of terminal C / C bonds and reducing methane formation. Example 9

[0103] Similar to Example 1, except that: the Ni / TiO2 catalyst was synthesized by flash Joule calcination, the precursor was nickel nitrate solution with a concentration of 15 mg / mL, and the nickel loading on the titanium oxide support was 1%.

[0104] The specific steps for using Ni / TiO2 catalyst in the hydrogenolysis of polypropylene are as follows:

[0105] (1) Weigh 0.1 g of catalyst Ni / TiO2 and 0.5 g of polypropylene and place them at the bottom of the reactor, and place an additional magnetic rotor. After the device is connected to the hydrogen cylinder, first fill it with 1 MPa of hydrogen, then close the gas path and slowly exhaust the gas to near atmospheric pressure. Repeat the operation 4 times to completely exhaust the air in the device.

[0106] (2) Charge the apparatus with 1 MPa of hydrogen, then set the target temperature to 180°C and the holding time to 6 h, and start the heating program. When the apparatus is heated to 150°C, start the magnetic stirrer and set the stirring speed to 500 RPM. After the reaction is complete and the apparatus is completely cooled, first use a gas bag to collect the reaction gas, and then use 5 mL of cyclohexane to dissolve and collect the liquid phase product. Example 10

[0107] Same as in Example 1, except that the loading of ruthenium on the titanium oxide support is 10%.

[0108] The Ru / TiO2 catalyst was used for the hydrogenolysis of polypropylene, and the specific steps are as follows:

[0109] (1) Weigh 0.1 g of catalyst Ru / TiO2 and 4 g of low-density polyethylene respectively and place them at the bottom of the reactor, and place an additional magnetic rotor; after the device is connected to the hydrogen cylinder, first fill it with 2 MPa of hydrogen, then close the gas path and slowly exhaust the gas to near atmospheric pressure. Repeat the operation 4 times to completely exhaust the air in the device.

[0110] (2) Charge the apparatus with 5 MPa of hydrogen, then set the target temperature to 300℃ and the holding time to 1 h, and start the heating program. When the apparatus is heated to 150℃, start the magnetic stirrer and set the stirring speed to 500 RPM. After the reaction is completed and the apparatus is completely cooled, first use a gas bag to collect the reaction gas, and then use 5 mL of cyclohexane to dissolve and collect the liquid phase product.

[0111] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for efficiently preparing saturated chain hydrocarbons from waste polyolefins, characterized in that, Includes the following steps: (1) Impregnation loading: Using titanium oxide as a carrier, a precursor containing an active metal is dissolved in water to form a precursor solution. The active metal is selected from one or two of ruthenium, platinum, and nickel. The precursor solution is loaded onto the surface of the titanium oxide carrier by impregnation to obtain a catalyst precursor loaded with the precursor, which is then dried. (2) Flash Joule calcination: The dried catalyst precursor obtained in step (1) is placed in the graphite tube of a flash Joule heating device, and an instantaneous current is applied to rapidly heat the catalyst precursor to the target temperature under the action of the current and complete the calcination treatment. The heating time of flash Joule calcination is 0.1-2.0 s, and the target temperature is 300℃-1500℃, thereby constructing small metal clusters and TiO2. x Catalysts with semi-encapsulated metal clusters that resist sintering and enhanced metal-support interactions; (3) Low-consumption hydrogenolysis reaction: The catalyst obtained in step (2) and the waste polyolefin raw material are placed together in a hydrogen atmosphere to carry out hydrogenolysis reaction, and a mixed product with liquid saturated chain hydrocarbons as the main component and a small amount of gaseous alkanes is obtained.

2. The method according to claim 1, characterized in that, The titanium oxide mentioned in step (1) is anatase phase titanium oxide.

3. The method according to claim 1, characterized in that, In step (2), the flash Joule calcination process is carried out under an inert atmosphere, which is selected from argon and / or nitrogen.

4. The method according to claim 1, characterized in that, In step (2), the active metal in the catalyst is loaded with 0.5-15 wt% on the titanium oxide support, and the average particle size of the active metal is 0.5-4.0 nm.

5. The method according to claim 4, characterized in that, The active metal in the catalyst described in step (2) is loaded onto the titanium oxide support at an amount of 1-10 wt%.

6. The method according to claim 1, characterized in that, The mass ratio of the waste polyolefin raw material to the catalyst in step (3) is 5-40:

1.

7. The method according to claim 1 or 6, characterized in that, The conditions for the hydrogenolysis reaction in step (3) are: reaction temperature of 180℃-300℃, initial hydrogen pressure of 1-5 MPa, and reaction time of 1-6 h.

8. The method according to claim 7, characterized in that, The conditions for the hydrogenolysis reaction in step (3) are: reaction temperature of 250℃, initial hydrogen pressure of 3 MPa, and reaction time of 2 h.

9. The method according to claim 1, characterized in that, The waste polyolefin raw material mentioned in step (3) is selected from polyethylene and / or polypropylene.

10. The method according to claim 1 or 9, characterized in that, The liquid hydrocarbon mentioned in step (3) is C5-C 35 Saturated alkanes within the specified range.

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