A method for preparing diesel fraction by catalytic hydrogenation of waste tire pyrolysis oil, and the obtained diesel fraction.

Abstract

This invention discloses a method for preparing diesel fraction from waste tire pyrolysis oil via catalytic hydrogenation, and the resulting diesel fraction, belonging to the field of solid waste resource utilization and petroleum hydrorefining technology. This invention addresses the problems of high sulfur, nitrogen, and gum content in waste tire pyrolysis oil, easy catalyst deactivation in laboratory trials, difficulty in controlling the hydrogenation upgrading effect, and the inability of the product to consistently meet the China VI standard. The method first removes solid slag, heavy gum, and moisture through a stepped pretreatment process to obtain refined raw materials. Then, hydrogenation upgrading is completed in an intermittent high-pressure reactor using a pre-sulfurized hydrogenation catalyst. Finally, the target product is obtained through fractionation. This invention's process is compatible with conventional laboratory equipment, is safe and controllable, and the core indicators of the product diesel fraction fully comply with the China VI b automotive diesel standard.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and petroleum hydrorefining technology, and particularly relates to a method for preparing diesel fraction by catalytic hydrogenation of waste tire pyrolysis oil, and the obtained diesel fraction. Background Technology

[0002] With the rapid development of my country's automobile industry, the amount of waste tires generated has been increasing year by year, exceeding ten million tons annually. Waste tires are non-degradable industrial solid waste; indiscriminate dumping or landfilling will cause serious environmental pollution and safety hazards, while also wasting a large amount of rubber hydrocarbon resources. Pyrolysis technology is the core technical route for achieving the harmless and resource-based utilization of waste tires. It can convert waste tires into pyrolysis oil, pyrolysis carbon black, steel wire, and combustible gas. Among these, the yield of pyrolysis oil can reach 40-50 wt%, making it the most important liquid-phase product.

[0003] However, waste tire pyrolysis oil has significant quality defects: First, it has high levels of sulfur and nitrogen impurities, with sulfur content typically reaching thousands to tens of thousands of mg / kg, which would cause serious air pollution if burned directly; second, it has high levels of aromatics and olefins, low proportion of saturated hydrocarbons, and a cetane number of only 25-30, far below the standard requirements for automotive diesel; third, it contains a large amount of carbon black slag, gum, and asphalt, which can easily lead to equipment coking and catalyst poisoning and deactivation; fourth, it has poor stability and is prone to oxidation, discoloration, and precipitation during storage, making it unsuitable for direct use as automotive fuel, which greatly limits the high-value and large-scale utilization of waste tire pyrolysis oil.

[0004] Hydrogenation is the core technology for upgrading waste tire pyrolysis oil to produce clean fuels. In existing technologies, hydrogenation solutions for waste tire pyrolysis oil are mostly concentrated in industrial continuous fixed-bed processes, which require large-scale equipment such as multi-stage series reactors, continuous feeding systems, and circulating hydrogen systems. The equipment investment is large and the operation threshold is high, making it impossible to replicate in the laboratories of conventional universities and research institutes, and making it difficult to carry out pilot-scale research and process optimization.

[0005] Existing hydrogenation schemes for waste tire pyrolysis oil suitable for laboratory use generally suffer from the following drawbacks: 1. The raw material pretreatment process is simple, only removing impurities through simple filtration, which cannot completely remove ultrafine carbon black, gum, and asphalt. During the hydrogenation reaction, this easily leads to catalyst coking, poisoning, and deactivation, resulting in poor reaction repeatability and unstable hydrogenation effects; 2. Most schemes use a single hydrogenation refining catalyst and a single-stage hydrogenation process, which can only achieve simple desulfurization and denitrification, but cannot simultaneously achieve aromatic saturation ring opening and cetane number improvement, making it difficult for the product to consistently meet the China VI standard requirements for automotive diesel; 3. To achieve deep quality improvement, harsh reaction conditions of ultra-high temperature and ultra-high pressure are often used, which not only increases the operational safety risks in the laboratory but also leads to excessive cracking of the raw materials and a significant reduction in diesel fraction yield; 4. Some schemes require the independent synthesis of special catalysts, which involves complex catalyst preparation processes and long cycles, significantly raising the experimental threshold and making it difficult to quickly carry out verification experiments.

[0006] Therefore, developing a hydrogenation method for waste tire pyrolysis oil that is compatible with conventional laboratory equipment, simple and safe to operate, has a stable hydrogenation and upgrading effect, and whose products can stably meet the China VI standard for automotive diesel is of great significance for promoting the high-value utilization of waste tire pyrolysis oil. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is that the method for preparing diesel fractions from waste tire pyrolysis oil via catalytic hydrogenation is not fully compatible with conventional laboratory equipment, and the resulting products do not meet the China VI b standard for automotive diesel. This invention proposes a method for preparing diesel fractions from waste tire pyrolysis oil via catalytic hydrogenation, which is fully compatible with conventional laboratory equipment, safe and controllable in operation, and can simultaneously achieve deep desulfurization and denitrogenation of pyrolysis oil and increase its cetane number. The resulting product stably meets the China VI b standard for automotive diesel while ensuring a high diesel yield. This method provides reliable pilot-scale technical support for the high-value utilization of waste tire pyrolysis oil, and also provides the obtained diesel fractions.

[0008] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing diesel fraction by catalytic hydrogenation of waste tire pyrolysis oil, comprising the following steps: Raw material cascade pretreatment: Waste tire pyrolysis oil is sequentially filtered through two stages to remove solid slag and impurities, vacuum distilled to remove heavy rubber and asphalt, and dehydrated by molecular sieve adsorption to obtain refined pyrolysis oil raw material; Catalyst presulfurization: The hydrogenation catalyst assembly is presulfurized to obtain a sulfidated hydrogenation catalyst; Intermittent hydrorefining reaction: Refined pyrolysis oil feedstock and sulfurized hydrorefining catalyst are added to a high-pressure reactor. After being replaced with inert gas and hydrogen, high-purity hydrogen is introduced. The hydrorefining reaction is completed under set conditions to obtain hydrorefined crude product. Product separation and refining: The crude hydrogenation product is filtered to remove the waste catalyst, and then distilled to obtain diesel fractions at 180-360℃.

[0009] In some embodiments, the hydrogenation catalyst combination is composed of a hydrogenation protection catalyst, a hydrogenation refining catalyst, and a hydrogenation reforming catalyst; the mass ratio of the hydrogenation protection catalyst, the hydrogenation refining catalyst, and the hydrogenation reforming catalyst is 0.5-1.5:5-7:2-4.

[0010] In some embodiments, the hydroprotection catalyst is a supported Ni-Mo / alumina catalyst for removing easily coking components, the hydrorefining catalyst is a supported Co-Mo-Ni / modified alumina catalyst for deep desulfurization and denitrification, and the hydroreforming catalyst is a supported Ni-W / molecular sieve-alumina composite support catalyst for selective saturated ring-opening upgrading of aromatics.

[0011] In some embodiments, the pre-sulfurization treatment is laboratory wet sulfidation, comprising: mixing the hydrogenation catalyst assembly with a sulfiding agent and a solvent and adding the mixture to a high-pressure reactor; after gas replacement, introducing hydrogen gas; and isothermal sulfidation at 280-320°C and 3-5 MPa for 1-3 hours to obtain a sulfidated hydrogenation catalyst; the sulfiding agent is carbon disulfide, the amount of which is 3-8% of the total mass of the hydrogenation catalyst assembly; and the solvent is n-heptane.

[0012] In some embodiments, the two-stage filtration consists of a primary diatomaceous earth-aided coarse filtration and a secondary precision filtration, with the filtration accuracy of the secondary precision filtration being ≤2μm; the absolute pressure of vacuum distillation is 3-10kPa, and the distillation temperature is 320-360℃, removing heavy fractions, colloids, and asphaltenes with boiling points greater than 360℃; adsorption dehydration uses activated 3A molecular sieves, with the amount of molecular sieves being 38% of the mass of the pyrolysis oil, and the water content of the refined pyrolysis oil raw material after dehydration is ≤100mg / kg.

[0013] In some embodiments, the total amount of sulfurized hydrogenation catalyst added is 5-12% of the mass of the refined pyrolysis oil feedstock.

[0014] In some embodiments, the operating conditions for the hydrogenation reaction are as follows: the initial hydrogen charging pressure is 5-7 MPa, the reaction temperature is 320-360°C, the reaction isothermal time is 4-8 h, the stirring speed is 300-500 rpm, and the hydrogen partial pressure inside the reactor is maintained at ≥7 MPa during the reaction.

[0015] In some embodiments, the distillation used for product separation and purification is atmospheric distillation or vacuum distillation. During the fractionation process, naphtha fraction with a boiling point less than 180°C and diesel fraction with a boiling point of 180-360°C are collected, while tail oil fraction with a boiling point greater than 360°C is recycled to the vacuum distillation unit for raw material stage pretreatment.

[0016] In some embodiments, the hydrotreating reaction adopts a stepwise hydrotreating method, which includes: first, adding the refined pyrolysis oil feedstock and the hydrotreating protection catalyst into a high-pressure reactor, and completing the pre-hydrotreating protection reaction at 220-280°C and 3-5 MPa, and obtaining a pre-hydrotreating oil sample after filtration; then, adding the pre-hydrotreating oil sample, the hydrorefining catalyst, and the hydrotreating catalyst into a high-pressure reactor, and completing the deep hydrorefining and remediating reaction at 320-360°C and 6-10 MPa to obtain the hydrotreating crude product.

[0017] In another aspect, the present invention provides a diesel fraction prepared by any of the above technical solutions, wherein the yield of the diesel fraction is ≥62wt%, the sulfur content is ≤10mg / kg, the cetane number is ≥51, and the mass fraction of polycyclic aromatic hydrocarbons is ≤7%.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Fully compatible with conventional laboratory equipment, low operating threshold. This invention uses an intermittent high-pressure reactor as the core reaction equipment, eliminating the need for large-scale industrial equipment such as continuous feeding and circulating hydrogen systems. It can be implemented in conventional chemical laboratories of universities and research institutes. The experimental process is simple and controllable, and a single person can complete all operations, enabling rapid process optimization and verification experiments.

[0019] 2. The cascade pretreatment process is highly targeted, solving the catalyst deactivation problem at its source. This invention, through a cascade pretreatment of "two-stage filtration - vacuum distillation - molecular sieve dehydration," can completely remove carbon black solids, heavy gums, asphalt, and moisture from waste tire pyrolysis oil. This effectively avoids problems such as catalyst pore blockage, coking, and poisoning deactivation during the hydrogenation reaction, significantly improving the stability and repeatability of the hydrogenation reaction.

[0020] 3. The catalyst composition is well-suited for strong compatibility, simultaneously achieving deep refining and upgrading. This invention employs a three-stage catalyst complex system of hydrogenation protection, hydrogenation refining, and hydrogenation upgrading. In a single-reactor batch reaction, it can simultaneously achieve the removal of easily coking components, deep desulfurization and denitrogenation, olefin saturation, and selective ring-opening upgrading of aromatics. This solves the problem that traditional single-stage hydrogenation processes cannot simultaneously address desulfurization, denitrogenation, and cetane number improvement. The product can stably meet the China VI b standard for automotive diesel.

[0021] 4. Mild process conditions, safe operation, and high diesel yield. The hydrogenation reaction conditions of this invention are mild, requiring no harsh conditions of ultra-high temperature and ultra-high pressure, thus reducing the safety risks of laboratory hydrogenation operations; at the same time, it can effectively inhibit excessive cracking of feedstock, with a diesel fraction yield of ≥62wt%, high feedstock utilization rate, and excellent economic performance.

[0022] 5. The technical solution has strong scalability and can provide reliable support for industrial scale-up. The process logic of this invention is highly compatible with industrial hydrogenation devices. The optimized parameters obtained from laboratory pilot tests can directly provide data support for pilot-scale and industrial scale-up. At the same time, it can be adapted to waste tire pyrolysis oil from different sources and with different properties, making it highly versatile. Detailed Implementation

[0023] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0024] This invention provides a method for preparing diesel fraction by catalytic hydrogenation of waste tire pyrolysis oil, comprising the following steps: Raw material cascade pretreatment: Waste tire pyrolysis oil is sequentially filtered through two stages to remove solid slag and impurities, vacuum distilled to remove heavy rubber and asphalt, and dehydrated by molecular sieve adsorption to obtain refined pyrolysis oil raw material.

[0025] Catalyst pre-sulfurization: The hydrogenation catalyst combination is pre-sulfurized to obtain a sulfidated hydrogenation catalyst. The hydrogenation catalyst combination is composed of a hydrogenation protection catalyst, a hydrogenation refining catalyst, and a hydrogenation reforming catalyst. This composite catalyst system and the pre-sulfurization process can form a highly active sulfidated phase that is different from that of general sulfide catalysts. It has excellent hydrogenation protection, deep desulfurization and denitrogenation, and aromatic shape-selective ring-opening reforming performance, which solves the defect that a single sulfide catalyst cannot achieve both refining and reforming effects.

[0026] Intermittent hydrorefining reaction: Refined pyrolysis oil feedstock and sulfurized hydrorefining catalyst are added to a high-pressure reactor. After being replaced with inert gas and hydrogen, high-purity hydrogen is introduced. The hydrorefining reaction is completed under set conditions to obtain hydrorefined crude product. Product separation and refining: The crude hydrogenation product is filtered to remove waste catalyst, and then distilled to obtain a diesel fraction at 180-360℃. The diesel fraction meets the requirements of the China VI b vehicle diesel standard as specified in GB 19147-2016.

[0027] In some embodiments, the two-stage filtration consists of a primary diatomaceous earth-aided coarse filtration and a secondary precision filtration. The secondary precision filtration has a filtration accuracy of ≤2μm, which can completely remove large particulate mechanical impurities and ultrafine carbon black solids from the pyrolysis oil, thus avoiding catalyst wear and pore blockage in subsequent hydrogenation reactions.

[0028] In some embodiments, the absolute pressure of vacuum distillation is 3-10 kPa (corresponding to a vacuum degree of -0.090 to -0.098 MPa), and the distillation temperature is 320-360°C. This removes heavy fractions, gums, and asphaltenes with boiling points greater than 360°C, eliminating coking precursors in the hydrogenation reaction process from the source and extending the catalyst's lifespan.

[0029] In some embodiments, adsorption and dehydration are performed using activated 3A molecular sieves, with the amount of molecular sieves being 38% of the mass of the pyrolysis oil. The water content of the refined pyrolysis oil feedstock after dehydration is ≤100mg / kg, so as to avoid the inhibition of the hydrogenation catalyst activity by water.

[0030] In some embodiments, the hydrotreating protection catalyst is a supported Ni-Mo / alumina catalyst for removing easily coking components, which can efficiently remove easily coking components such as dienes from pyrolysis oil and protect the activity of the main catalyst; the hydrorefining catalyst is a supported Co-Mo-Ni / modified alumina catalyst for deep desulfurization and denitrification, which has excellent deep hydrodesulfurization and denitrification activity and can remove sulfur and nitrogen impurities to below the national standard limits; the hydroreforming catalyst is a supported Ni-W / molecular sieve-alumina composite support catalyst for selective saturation and ring-opening upgrading of aromatics, which has excellent selective saturation and ring-opening performance of aromatics, can significantly improve the cetane number of the product, while inhibiting excessive cracking and ensuring the yield of diesel fraction.

[0031] In some embodiments, the mass ratio of the hydrogenation protection catalyst, the hydrogenation refining catalyst, and the hydrogenation reforming catalyst is 0.5-1.5:5-7:2-4. This ratio can take into account the effects of hydrogenation protection, deep refining, and quality improvement, and achieve the optimal matching of hydrogenation performance.

[0032] In some embodiments, the pre-sulfurization treatment is a laboratory wet sulfidation process, comprising: mixing the hydrogenation catalyst assembly with a sulfiding agent and a solvent, adding the mixture to a high-pressure reactor, purging with hydrogen gas after gas replacement, and isothermal sulfidation at 280-320°C and 3-5 MPa for 1-3 hours to obtain a sulfidated hydrogenation catalyst; the sulfiding agent is carbon disulfide, and the amount of sulfiding agent is 3-8% of the total mass of the hydrogenation catalyst assembly; the solvent is n-heptane. This sulfidation method is suitable for laboratory batch high-pressure reactors, is simple to operate, provides stable sulfidation results, and can fully activate the activity of the hydrogenation catalyst. Optionally, commercially available pre-sulfidated hydrogenation catalysts can also be used directly, eliminating the need for additional sulfidation operations and further simplifying the experimental procedure.

[0033] In some embodiments, the total amount of sulfurized hydrogenation catalyst added is 5-12% of the mass of the refined pyrolysis oil feedstock.

[0034] In some embodiments, in the intermittent hydrogenation reaction, the gas replacement specifically involves replacing the air inside the reactor with high-purity nitrogen 2-4 times, and then replacing it with high-purity hydrogen 2-4 times to completely remove oxygen from the reactor and ensure the safe operation of the hydrogenation reaction.

[0035] In some embodiments, the operating conditions for the hydrogenation reaction are as follows: the initial hydrogen charging pressure is 5-7 MPa, the reaction temperature is 320-360℃, the reaction isothermal time is 4-8 h, the stirring speed is 300-500 rpm, and the hydrogen partial pressure inside the reactor is maintained at ≥7 MPa during the reaction to ensure the full progress of the hydrogenation reaction.

[0036] In some embodiments, the distillation used for product separation and purification is atmospheric distillation or vacuum distillation. During the fractionation process, naphtha fraction with a boiling point of less than 180°C and diesel fraction with a boiling point of 180-360°C are collected, while tail oil fraction with a boiling point of greater than 360°C is recycled to the vacuum distillation unit for raw material stage pretreatment, thereby improving the overall utilization rate of raw materials.

[0037] In some embodiments, the hydrotreating reaction adopts a stepwise hydrotreating method, which includes: first, adding the refined pyrolysis oil feedstock and the hydrotreating protection catalyst into a high-pressure reactor, and completing the pre-hydrotreating protection reaction at 220-280°C and 3-5 MPa, and obtaining a pre-hydrotreating oil sample after filtration; then, adding the pre-hydrotreating oil sample, the hydrorefining catalyst, and the hydrotreating catalyst into a high-pressure reactor, and completing the deep hydrorefining and remediating reaction at 320-360°C and 6-10 MPa to obtain the hydrotreating crude product.

[0038] The aforementioned stepwise hydrogenation can further enhance the hydrogenation effect, reduce catalyst coking, and improve product quality stability. Specifically, stepwise hydrogenation can further leverage the functional differences of the three-stage catalyst, avoid the impact of easily coking components on the activity of the main catalyst, and further improve the activity stability and hydrogenation effect of the sulfide-state catalyst.

[0039] In another aspect, the present invention provides a diesel fraction prepared by any of the above-mentioned technical solutions, wherein the yield of the diesel fraction is ≥62wt%, the sulfur content is ≤10mg / kg, the cetane number is ≥51, and the mass fraction of polycyclic aromatic hydrocarbons is ≤7%. All indicators of this diesel fraction meet the requirements of the China VI b vehicle diesel standard specified in GB 19147-2016.

[0040] To more clearly and in detail introduce the method for preparing diesel fraction by catalytic hydrogenation of waste tire pyrolysis oil and the obtained diesel fraction provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0041] In the following embodiments and comparative examples of the present invention, the waste tire pyrolysis oil used was taken from an industrial continuous waste tire pyrolysis unit, and its basic properties are shown in Table 1; the hydrogenation catalysts used were all commercial oil refining grade hydrogenation catalysts, or similar hydrogenation catalysts synthesized in the laboratory could also be used; all reagents used were of analytical grade, and all instruments used were conventional laboratory instruments.

[0042] Table 1 Basic Properties of Waste Tire Pyrolysis Oil Raw Material

[0043] Example 1 This embodiment provides a method for preparing China VI standard diesel fractions by catalytic hydrotreating waste tire pyrolysis oil. The specific steps are as follows: S1, Raw material staged pretreatment Take 200 mL of the above-mentioned waste tire pyrolysis oil and perform two-stage filtration to remove solids: the first stage of coarse filtration uses a Buchner funnel for vacuum filtration, with two layers of qualitative filter paper and 2 g of diatomaceous earth filter aid added to complete the coarse filtration; the second stage of fine filtration uses a sand core filtration device with a 2 μm microporous filter membrane to perform a second fine filtration on the coarse oil sample to obtain a clear oil sample without solids.

[0044] The finely filtered oil sample was added to a vacuum distillation apparatus, and the absolute pressure was controlled at 5 kPa (vacuum degree -0.095 MPa). The distillation temperature was 350℃. The light fraction below 360℃ was collected, and the heavy fraction, gums and asphaltenes above 360℃ were removed.

[0045] The light distillate oil sample obtained from distillation was added to an activated 3A molecular sieve at a concentration of 5% of the oil sample mass. The mixture was then sealed and stirred at room temperature for 2 hours to complete deep dehydration, yielding a refined pyrolysis oil feedstock. The water content of the feedstock was measured to be 62 mg / kg. The feedstock was then sealed and stored for later use.

[0046] S2, catalyst presulfurization Hydrogenation protection catalyst, hydrorefining catalyst, and hydromodification catalyst were compounded in a mass ratio of 1:6:3, with a total mass of 8g. The compounded catalyst, 0.4g of carbon disulfide (sulfiding agent, 5% of the catalyst mass), and 20mL of n-heptane were added to a 500mL high-pressure reactor, and the reactor was sealed. The air inside the reactor was first replaced three times with high-purity nitrogen, and then three times with high-purity hydrogen. Hydrogen was then introduced to a pressure of 4MPa, stirring was started, and the temperature was raised to 300℃. Sulfidation was carried out at this temperature for 2 hours to complete the pre-sulfidation of the catalyst. After sulfidation, the reactor was cooled to room temperature, the pressure was slowly released, the solvent was poured out, and the sulfided catalyst was retained in the reactor for later use.

[0047] S3, intermittent hydrogenation reforming reaction Add 100 mL of the refined pyrolysis oil raw material obtained in step S1 to the high-pressure reactor. Seal the reactor and check its airtightness. First, purge with high-purity nitrogen three times, then purge with high-purity hydrogen three times to completely remove air from the reactor. Charge the reactor with high-purity hydrogen to the initial pressure of 6.0 MPa, turn on the magnetic stirrer, set the stirring speed to 350 rpm, and raise the temperature to 340°C at a rate of 5°C / min. At this point, the pressure inside the reactor will rise to about 8.0 MPa. Maintain the reaction at this temperature for 6 hours. If the pressure drops by more than 1 MPa during the reaction, add hydrogen to bring it up to 8.0 MPa to maintain a stable hydrogen partial pressure inside the reactor.

[0048] After the reaction is complete, stop heating and stirring, allow it to cool naturally to room temperature (≤40℃), slowly release the pressure to atmospheric pressure, open the vessel, and pour out all the reaction products.

[0049] Repeat the above steps 3 times.

[0050] S4. Product separation and purification The reaction product was filtered under vacuum to remove the spent catalyst, resulting in a clear crude hydrogenated product. The crude hydrogenated product was then added to an atmospheric distillation unit for fractionation. The naphtha fraction with a boiling point below 180°C, the diesel fraction with a boiling point between 180°C and 360°C were collected, while the tail oil fraction with a boiling point above 360°C was recovered for later use.

[0051] The diesel fraction prepared in this embodiment was tested, and the results of various indicators are shown in Table 2. The diesel fraction yield was 65.1 wt%.

[0052] Example 2 This embodiment provides a method for preparing China VI standard diesel fraction by catalytic hydrotreating waste tire pyrolysis oil. The method employs a step-by-step hydrotreating approach, and the specific steps are as follows: S1, Raw material staged pretreatment Following the same step S1 as in Example 1, refined pyrolysis oil raw material is obtained.

[0053] S2, catalyst presulfurization Presulfurization was performed on the hydrogenation protection catalyst and the composite catalyst for hydrogenation refining and modification, respectively: Pre-sulfurization of hydrogenated protective catalyst: Take 1g of hydrogenated protective catalyst, add 0.05g of carbon disulfide and 10mL of n-heptane, and complete the pre-sulfurization according to the sulfidation process in Example 1, and set aside for later use; Pre-sulfurization of the hydrorefining and reforming composite catalyst: Take 6g of hydrorefining catalyst and 3g of hydroreforming catalyst, mix them evenly, add 0.45g of carbon disulfide and 20mL of n-heptane, and complete the pre-sulfurization according to the sulfidation process in Example 1, and set aside for later use.

[0054] S3, Stepwise hydrogenation reforming reaction First stage: Pre-hydrogenation protection reaction. 100 mL of refined pyrolysis oil feedstock and pre-sulfurized hydrogenation protection catalyst were added to a high-pressure reactor. After sealing and purging, hydrogen was introduced to an initial pressure of 3 MPa, the temperature was raised to 260°C, the stirring speed was 300 rpm, and the reaction was maintained at this temperature for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, filtered to remove the catalyst, and the pre-hydrogenated oil sample was obtained.

[0055] The second stage: Deep hydrorefining and upgrading reaction. The pre-hydrogenated oil sample and the pre-sulfurized refining + upgrading composite catalyst were added to a high-pressure reactor. After sealing and purging, hydrogen was introduced to an initial pressure of 6 MPa, the temperature was raised to 340℃, the stirring speed was 400 rpm, and the reaction was maintained at this temperature for 5 hours, keeping the hydrogen partial pressure inside the reactor ≥7.5 MPa. After the reaction was completed, the pressure was released by cooling, yielding the crude hydrotreated product.

[0056] Repeat the above steps 3 times.

[0057] S4. Product separation and purification Following the same procedure as in Example 1, step S4 is performed to complete the fraction cutting and obtain the target diesel fraction.

[0058] The diesel fraction prepared in this embodiment was tested, and the results of various indicators are shown in Table 2. The diesel fraction yield was 63.6 wt%.

[0059] Example 3 This embodiment provides a method for preparing China VI standard diesel fractions by catalytic hydrotreating waste tire pyrolysis oil. The specific steps are as follows: S1, Raw material staged pretreatment Take 200 mL of waste tire pyrolysis oil, and perform coarse filtration with diatomaceous earth aid and 1 μm precision filtration to remove solids; then perform vacuum distillation at an absolute pressure of 8 kPa and a distillation temperature of 330℃ to remove heavy gums; then soak in activated 3A molecular sieve for 12 h to remove water, with the amount of molecular sieve being 7% of the oil sample mass, to obtain refined pyrolysis oil raw material with a water content of 78 mg / kg.

[0060] S2, catalyst presulfurization Hydrogenation protection catalyst, hydrorefining catalyst, and hydromodification catalyst were compounded in a mass ratio of 0.8:5.5:3.7, with a total amount of 10% of the mass of refined pyrolysis oil. Pre-sulfurization was completed using the wet sulfidation process of Example 1 to obtain the sulfidated catalyst.

[0061] S3, intermittent hydrogenation reforming reaction 100 mL of refined pyrolysis oil feedstock and sulfide-state catalyst were added to a high-pressure reactor. After successful purging, hydrogen was introduced to an initial pressure of 5.5 MPa, the temperature was raised to 350 °C, the stirring speed was 400 rpm, and the reaction was maintained at this temperature for 5 hours, keeping the hydrogen partial pressure inside the reactor ≥7 MPa. After the reaction was completed, the reactor was cooled and depressurized to obtain the hydrogenated crude product.

[0062] Repeat the above steps 3 times.

[0063] S4. Product separation and purification Following the same procedure as in Example 1, step S4 is performed to complete the fraction cutting and obtain the target diesel fraction.

[0064] The diesel fraction prepared in this embodiment was tested, and the results of various indicators are shown in Table 2. The diesel fraction yield was 62.3 wt%.

[0065] Comparative Example 1 This comparative example omits the raw material pretreatment step; the remaining operations are the same as in Example 1, specifically: Take 100 mL of waste tire pyrolysis oil, filter it simply through a single layer of filter paper, and add it directly to a high-pressure reactor. Mix it with the same pre-sulfurization catalyst as in Example 1, and operate according to the hydrogenation reaction conditions and product separation steps of Example 1 to obtain diesel fraction.

[0066] The product of this comparative example was tested, and the results of various indicators are shown in Table 2. The diesel fraction yield was 48.7 wt%.

[0067] Comparative Example 2 This comparative example uses only a single hydrorefining catalyst, without using a hydroprotection catalyst or a hydromodification catalyst. All other operations are the same as in Example 1, specifically: S1. The raw material pretreatment is the same as in Example 1 to obtain refined pyrolysis oil raw material; S2. Using only commercially available Co-Mo-Ni hydrorefining catalyst, presulfurization was carried out according to the process of Example 1, with a total catalyst dosage of 8g. S3, the hydrogenation reaction conditions and product separation steps are the same as in Example 1, to obtain diesel fraction.

[0068] The product of this comparative example was tested, and the results of various indicators are shown in Table 2. The diesel fraction yield was 61.2 wt%.

[0069] Comparative Example 3 This comparative example uses hydrogenation reaction process parameters that are outside the scope of this invention, while the remaining operations are the same as in Example 1, specifically: The hydrogenation reaction temperature was set to 280℃, and the reaction time was kept constant for 3 hours. The remaining pretreatment, catalyst sulfidation, and product separation steps were the same as in Example 1, and diesel fraction was obtained.

[0070] The product of this comparative example was tested, and the results of various indicators are shown in Table 2. The diesel fraction yield was 64.5 wt%.

[0071] Table 2. Test results of key indicators of diesel fractions in each example and comparative example.

[0072] The test results in Table 2 show that: 1. The diesel fractions prepared in Examples 1-3 of this invention fully meet the standard requirements of GB 19147-2016 National VI b diesel for vehicles in all core indicators, and the diesel fraction yield is ≥62wt%, realizing the efficient and high-value utilization of waste tire pyrolysis oil.

[0073] 2. Comparative Example 1 omitted the step of staged pretreatment. The raw material, which was only simply filtered, contained a large amount of carbon black and gum, which led to severe catalyst deactivation, insufficient hydrogenation reaction, and the sulfur, nitrogen and aromatic hydrocarbon content of the product far exceeded the national standard limit. The cetane number was only slightly improved, and a large amount of heavy components coked, resulting in a significant decrease in diesel yield. This proves the necessity of the staged pretreatment of the present invention.

[0074] 3. Comparative Example 2 uses only a single hydrorefining catalyst, which can achieve a certain desulfurization effect, but cannot achieve selective ring-opening and upgrading of aromatics. The cetane number of the product is far below the national standard requirement, and the content of polycyclic aromatic hydrocarbons exceeds the standard, which cannot meet the National VI diesel standard. This proves the core role of the catalyst compound system of the present invention.

[0075] 4. Comparative Example 3 used too low a reaction temperature and too short a reaction time, resulting in insufficient hydrogenation reaction, poor removal of sulfur and nitrogen impurities, low aromatic saturation, and failure to meet the core indicators of the product. This proves the rationality of the process parameter range of the present invention.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing diesel fraction by catalytic hydrogenation of waste tire pyrolysis oil, characterized in that, Includes the following steps: Raw material cascade pretreatment: Waste tire pyrolysis oil is sequentially filtered through two stages to remove solid slag and impurities, vacuum distilled to remove heavy rubber and asphalt, and dehydrated by molecular sieve adsorption to obtain refined pyrolysis oil raw material; Catalyst presulfurization: The hydrogenation catalyst assembly is presulfurized to obtain a sulfidated hydrogenation catalyst; Intermittent hydrorefining reaction: The refined pyrolysis oil feedstock and the sulfurized hydrorefining catalyst are added to a high-pressure reactor. After being replaced with inert gas and hydrogen, high-purity hydrogen is introduced. The hydrorefining reaction is completed under set conditions to obtain the hydrorefined crude product. Product separation and refining: The crude hydrogenation product is filtered to remove the waste catalyst, and then distilled to obtain a diesel fraction at 180-360℃.

2. The method according to claim 1, characterized in that, The hydrogenation catalyst combination is composed of a hydrogenation protection catalyst, a hydrogenation refining catalyst, and a hydrogenation reforming catalyst; the mass ratio of the hydrogenation protection catalyst, the hydrogenation refining catalyst, and the hydrogenation reforming catalyst is 0.5-1.5:5-7:2-4.

3. The method according to claim 2, characterized in that, The hydrogenation protection catalyst is a supported Ni-Mo / alumina catalyst for removing easily coking components; the hydrogenation refining catalyst is a supported Co-Mo-Ni / modified alumina catalyst for deep desulfurization and denitrification; and the hydrogenation upgrading catalyst is a supported Ni-W / molecular sieve-alumina composite support catalyst for selective saturated ring-opening upgrading of aromatics.

4. The method according to claim 1, characterized in that, The pre-sulfurization treatment is a laboratory wet sulfidation process, comprising: mixing the hydrogenation catalyst combination with a sulfiding agent and a solvent, adding the mixture to a high-pressure reactor, purging with hydrogen after gas replacement, and sulfiding at a constant temperature of 280-320℃ and 3-5MPa for 1-3 hours to obtain the sulfidated hydrogenation catalyst; the sulfiding agent is carbon disulfide, the amount of the sulfiding agent is 3-8% of the total mass of the hydrogenation catalyst combination, and the solvent is n-heptane.

5. The method according to claim 1, characterized in that, The two-stage filtration consists of a primary diatomaceous earth-aided coarse filtration and a secondary precision filtration, with the secondary precision filtration having a filtration accuracy of ≤2μm. The vacuum distillation operates at an absolute pressure of 3-10kPa and a distillation temperature of 320-360℃, removing heavy fractions, colloids, and asphaltenes with boiling points greater than 360℃. The adsorption dehydration uses activated 3A molecular sieves, with the molecular sieve dosage being 38% of the pyrolysis oil mass, resulting in a water content of ≤100mg / kg for the refined pyrolysis oil raw material after dehydration.

6. The method according to claim 1, characterized in that, The total amount of the sulfide-state hydrogenation catalyst added is 5-12% of the mass of the refined pyrolysis oil feedstock.

7. The method according to claim 1, characterized in that, The operating conditions for the hydrogenation reaction are as follows: initial hydrogen pressurization pressure is 5-7 MPa, reaction temperature is 320-360℃, reaction isothermal time is 4-8 h, stirring speed is 300-500 rpm, and the hydrogen partial pressure inside the reactor is maintained at ≥7 MPa during the reaction.

8. The method according to claim 1, characterized in that, The product separation and purification process employs atmospheric distillation or vacuum distillation. During the fractionation process, naphtha fractions with boiling points below 180°C and diesel fractions with boiling points between 180°C and 360°C are collected, while tail oil fractions with boiling points above 360°C are recycled back to the vacuum distillation unit of the raw material stage pretreatment.

9. The method according to claim 1, characterized in that, The hydrotreating reaction adopts a stepwise hydrotreating method, which includes: first, adding the refined pyrolysis oil feedstock and the hydrotreating protective catalyst into a high-pressure reactor, and completing the pre-hydrotreating protective reaction at 220-280℃ and 3-5MPa, and obtaining a pre-hydrotreating oil sample after filtration; then, adding the pre-hydrotreating oil sample, the hydrorefining catalyst, and the hydrotreating catalyst into a high-pressure reactor, and completing the deep hydrorefining and remediating reaction at 320-360℃ and 6-10MPa to obtain the hydrotreating crude product.

10. The diesel fraction prepared by the method according to any one of claims 1-9, characterized in that, The diesel fraction has a yield of ≥62wt%, a sulfur content of ≤10mg / kg, a cetane number of ≥51, and a polycyclic aromatic hydrocarbon mass fraction of ≤7%.

Images