Hydrofining method for petroleum cracking carbon five fraction oil

Abstract

The present application relates to the technical field of deep processing of petroleum chemical carbon five fraction oil, and particularly relates to a petroleum cracking carbon five fraction oil hydrofining method, wherein a polar competitive adsorbent is added into raw oil before the raw oil enters a main hydrogenation reaction, so that enrichment and deposition of cyclopentadiene (CPD) / dicyclopentadiene (DCPD) and chain double bond components in the catalyst are reduced; meanwhile, a low-acid hole-expanding Ni catalyst is used to reduce the polymerization deposition risk and maintain an effective hydrogenation rate, so that the problems of colloid deposition and pressure drop increase in the front section of the catalyst bed are relieved, and the problem that a Ni-based catalyst in the prior art cannot effectively inhibit the deposition of CPD components for a long time when hydrofining the CPD-containing carbon five fraction oil is solved.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a method for hydrorefining C5 fraction oil from petroleum cracking. Background Technology

[0002] C5 fraction from petroleum cracking is an important byproduct of ethylene cracking units. It typically contains isoprene, isoprene, cyclopentadiene, dicyclopentadiene, monoolefins, and trace amounts of sulfur compounds. This type of fraction has the potential for further separation and utilization. However, it contains a high content of highly reactive dienes, which are prone to dimerization, copolymerization, or oligomerization during storage, transportation, and subsequent processing, forming gums or polymers. This results in poor oil stability and seriously affects downstream separation, purification, and comprehensive utilization.

[0003] To address the aforementioned issues, existing technologies primarily employ selective hydrogenation processes to remove diolefins. For instance, Chinese utility model patent CN102485707B discloses a method that uses thermal polymerization pretreatment and multi-tower distillation to suppress the self-polymerization of light components and unsaturated compounds, thereby reducing the unsaturated content of the feedstock before it enters the hydrogenation step. Furthermore, Chinese utility model patent CN102989476A discloses a Ni-based catalyst for the saturated hydrogenation of C5 fractions, which uses alkaline additives such as MgO to adjust its acidity to accommodate the hydrogenation of unsaturated hydrocarbons.

[0004] Although the above methods have improved diene conversion to some extent, simply optimizing the catalyst composition or conventional process parameters is insufficient to reduce the tendency of active dienes such as CPD to undergo Diels-Alder cycloaddition and cationic polymerization at Lewis acid sites on Ni catalysts. The resulting polymers gradually deposit in the catalyst channels, leading to a rapid increase in bed pressure drop, aggravated local temperature rise in the bed, rapid decay of catalyst activity, and short operating cycle of the unit. Existing Ni-based catalysts are difficult to effectively suppress the deposition of CPD components in the long term when processing C5 fractions with high CPD content. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that in the existing process of hydrorefining of C5 fraction oil from petroleum cracking in a Ni-based fixed bed, cyclopentadiene, dicyclopentadiene and chain diene components are prone to local enrichment and deposition in the inlet section of the catalyst bed, which leads to blockage of the pores in the front section of the bed, increased pressure drop and catalytic activity decay. Simply adjusting the catalyst composition or increasing the hydrogenation intensity is difficult to achieve both the effectiveness and long-term stability of deposition inhibition.

[0006] To achieve the above objectives, this application adopts the following technical solution: a method for hydrorefining C5 fraction oil from petroleum cracking, comprising the following steps: S1. The composition of the petroleum cracked C5 fraction oil is analyzed, and then the feed oil is subjected to alkaline washing and adsorption pretreatment to obtain purified feed oil. S2. Prepare a polar competitive adsorbent, wherein the polar competitive adsorbent comprises a polar competitive adsorbent body and a weakly alkaline regulating component; S3. Prepare a low-acid expanded-pore Ni / γ-Al2O3 catalyst, wherein the low-acid expanded-pore Ni / γ-Al2O3 catalyst uses expanded-pore γ-Al2O3 as a support and loads Ni active components. S4. The purified feed oil obtained in step S1 is pre-contacted with the polar competitive adsorbent obtained in step S2 before hydrogenation to obtain pre-contact feed oil; then the pre-contact feed oil is continuously fed into a fixed bed hydrogenation reactor filled with the low acid expanded pore Ni / γ-Al2O3 catalyst, and enters the catalyst bed together with hydrogen to carry out hydrogenation reaction to obtain hydrogenation reaction product. S5. The hydrogenation reaction product is subjected to gas-liquid separation, flash evaporation and distillation stabilization to obtain hydrogenated refined C5 fraction oil.

[0007] Preferably, in S1, the feedstock oil before the hydrogenation reaction contains no more than 15% cyclopentadiene and dicyclopentadiene.

[0008] Preferably, in S2, the competitive adsorbent in the polar competitive adsorbent is selected from at least one of N-methylpyrrolidone, ethylene glycol, and sulfolane; the weakly alkaline adjusting component of the polar competitive adsorbent is selected from at least one of sodium ethoxide, sodium carbonate, and potassium carbonate.

[0009] Preferably, the amount of the weakly alkaline adjusting component added in S2 is 0.001-0.01 parts per 100 parts of purified raw material oil.

[0010] Preferably, in S3, the low-acid, porous Ni / γ-Al2O3 catalyst is prepared according to the following method: The γ-Al2O3 support was impregnated in citric acid solution to expand the pores. After impregnation, it was dried and calcined to obtain the expanded γ-Al2O3 support. The expanded γ-Al2O3 support was impregnated with nickel salt solution. After impregnation, it was dried, calcined and reduced with hydrogen in sequence to obtain the low acid expanded pore Ni / γ-Al2O3 catalyst.

[0011] Preferably, in the method for preparing the low-acid pore-expanding Ni / γ-Al2O3 catalyst, the concentration of the citric acid solution is 0.10-0.35 mol / L, and the impregnation and pore-expanding time is 1-4 h; the nickel salt solution is a nickel nitrate solution with a concentration of 2.0-3.5 mol / L and an impregnation time of 2-5 h.

[0012] Preferably, in S4, the amount of the polar competitive adsorbent added is 0.00005-0.0005 parts per 100 parts of purified raw material oil.

[0013] Preferably, in step S4, when the feed oil and the polar competitive adsorbent are pre-contacted, the pre-contact temperature is 40-70℃, the pre-contact time is 5-15min, and the stirring speed is 300-600r / min.

[0014] Preferably, in step S4, the hydrogenation reaction is carried out at a temperature of 80-110°C, a pressure of 2.0-4.0 MPa, and a liquid hourly space velocity of 1.0-3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 150:1-350:1.

[0015] Preferably, the total alkyne content in the hydrorefined C5 fraction oil obtained by the above method is not higher than 50 mg / kg, the gum content is not higher than 3.0 mg / 100 mL, and the retention rate of effective C5 unsaturated components is not less than 60%.

[0016] This invention provides a method for hydrorefining C5 fraction oil from petroleum cracking. This method controls the feedstock composition at the source, allowing the C5 fraction oil to pre-contact with a polar competitive adsorbent to form a pre-contact feedstock oil. This pre-contact feedstock oil then enters a fixed-bed hydrorefining reactor packed with Ni / γ-Al2O3 catalyst. Upon entering the fixed-bed hydrorefining reactor, the polar competitive adsorbent travels with the feedstock oil to the catalyst bed inlet section. There, it competes with CPD / DCPD and chain diene components for adsorption at acidic sites, polar adsorption sites, and pore areas of the catalyst. This reduces the rate of CPD / DCPD polymer formation on and inside the catalyst bed, slows the rate of pressure drop in the bed, and helps maintain the effective hydrogenation rate and long-term operational stability of the catalyst. Attached Figure Description

[0017] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 A bar chart showing the calculated CPD / DCPD content in each sample; Figure 2 Bar chart showing the alkyne content in each sample; Figure 3 Bar chart showing the gel content in each sample; Figure 4 Bar chart showing the retention rate of effective C5 unsaturated components in each sample; Figure 5 Line graphs showing the change in fixed-bed pressure drop over 100 hours for each preparation method. Detailed Implementation

[0018] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0019] This invention provides a method for hydrorefining C5 fraction oil from petroleum cracking, the specific steps of which are as follows: S1: Composition analysis was performed on 100-104 parts of industrial cracked C5 fraction feedstock oil to confirm that the total CPD monomer content in the feedstock oil was <16%. Subsequently, 30-35 parts of 5-15% NaOH or KOH aqueous solution were mixed with the feedstock oil, ensuring an oil-to-water volume ratio of 1:0.1-0.3. The mixture was stirred for 30-60 minutes at 40-60℃ and a stirring speed of 300-600 r / min. After that, the mixture was allowed to stand for 2 hours to separate the aqueous phase. The oil phase after standing was then passed through an adsorber filled with activated alumina at a temperature of 40-80℃ and a liquid hourly space velocity of 2-5 h⁻¹. -1 Under these conditions, trace amounts of organic sulfur and residual polar impurities are further removed to obtain purified feedstock oil; S2: Add 0.0003 parts of at least one of the competitive adsorbents such as N-methylpyrrolidone, EG, and Sulfolane, and 0.000003 parts of at least one of the weakly basic adjusting components such as sodium ethoxide, sodium carbonate, or potassium carbonate to a reaction vessel. The addition ratio is 0.001-0.01 parts of the weakly basic adjusting component per 100 parts of the competitive adsorbent. Stir for 30-60 minutes at an ambient temperature of 25°C and a stirring speed of 300-800 r / min to obtain a polar competitive adsorbent. S3: The γ-Al2O3 support is impregnated in a 0.1-0.5 mol / L citric acid solution at room temperature for 1-3 h. After impregnation, it is dried at 120 °C for 8-12 h, and then calcined at a rate of 2 °C / min to 450-550 °C for 4-6 h. The above impregnation-drying-calcination process is repeated 1-3 times to form a porous γ-Al2O3 support; Ni(NO3)2·6H2O is dissolved in deionized water to prepare a nickel nitrate solution with a concentration of 2-4 mol / L. The porous γ-Al2O3 support was impregnated in nickel nitrate solution at room temperature for 2-4 hours. After impregnation, it was dried at 120℃ for 6-12 hours. Then, the temperature was increased to 450-550℃ at a rate of 2℃ / min and calcined for 4-6 hours. After calcination, it was reduced in a gas system with a hydrogen concentration of ≥99% for 4-8 hours at a hydrogen flow rate of 100-300 mL / g-cat·h to obtain a low-acid porous Ni / γ-Al2O3 catalyst. This catalyst was then added to a fixed-bed hydrogenation reactor. S4: Before hydrogenation, 100-104 parts of purified feedstock oil are pre-contacted with 0.0003 parts of polar competitive adsorbent in a reactor by stirring for 5-15 minutes at a speed of 300-500 r / min and a temperature of 40-70℃. The pre-contacted feedstock oil is prepared by mixing 0.00005-0.0005 parts of polar competitive adsorbent with 100 parts of purified feedstock oil. Before the reaction, the air in the fixed-bed hydrogenation reactor is replaced with nitrogen gas of not less than 99% purity, followed by hydrogen gas replacement and pressurization. The pre-contacted feedstock oil is then continuously fed into the fixed-bed hydrogenation reactor via a metering pump and enters the catalyst bed along with the hydrogen gas. The reaction is carried out at a temperature of 60-120℃, a pressure of 2.0-4.0 MPa, and a liquid hourly space velocity of 1.0-3.0 h⁻¹. -1 Hydrogenation reaction of pre-contact feedstock oil is carried out under conditions of hydrogen-to-oil volume ratio of 100-400:1. S5: The hydrogenation reaction product obtained in step S4 is fed into a gas-liquid separator for gas-liquid separation. The gas-liquid separation temperature is controlled at 25-40℃, and the gas-liquid separation pressure is controlled at 2.5-3.0 MPa. After the gas-liquid phase separation is completed, the obtained liquid phase is recovered. The liquid phase is then fed into a flash tank for flash evaporation. The flash evaporation temperature is controlled at 30-50℃, and the flash evaporation pressure is controlled at 0.1-0.3 MPa to obtain a flash liquid phase. The flash liquid phase is then fed into a distillation column for distillation stabilization treatment. The distillation column has 15-25 theoretical plates, a reflux ratio of 1.0-3.0, and a top pressure of 0.10-0.20 MPa. The C5 fraction is collected as hydrorefined C5 oil.

[0020] Specifically, in S1, during the detection of industrial cracked C5 fraction feedstock oil, CPD in the feedstock oil is the most important precursor leading to polymerization and deposition. If the CPD content exceeds 15%, even with excessive polar competitive adsorbents and optimized catalysts, it is difficult to completely suppress the aggregation and deposition of CPD on the Lewis acid sites of the Ni catalyst, resulting in a significant increase in polymer formation, a rapid increase in bed pressure drop, and rapid catalyst deactivation.

[0021] Specifically, in S3, the Ni / γ-Al2O3 catalyst uses γ-Al2O3 as a support, and the Ni loading in the catalyst is 5-20%. This catalyst can improve the diffusion state of C5 unsaturated components, oligomer precursors and hydrogenation products in the catalyst channels, reduce the local enrichment of CPD near Lewis acid sites, polar sites and pore openings, and reduce the retention and deposition of polymerization precursors in the channels.

[0022] Specifically, in S4, hydrogen is introduced into the fixed-bed hydrogenation reactor to ensure a hydrogen concentration of 99% and to keep the Ni / γ-Al2O3 catalyst in a reduced state. 0.00005-0.0005 parts of polar competitive adsorbent are added to every 100 parts of purified feedstock oil. If the amount added is too low, the distribution of polar competitive adsorbent in the feedstock oil will be insufficient, and after entering the catalyst bed, it will be difficult to form effective competition for acidic sites, polar adsorption sites and pore retention areas, and it will not be able to weaken the local enrichment of CPD components. If the amount added is too high, it may cover or interfere with the Ni metal hydrogenation active sites on the surface of the Ni / γ-Al2O3 catalyst.

[0023] The short-term, mild contact between the polar competitive adsorbent and the feedstock oil allows the polar adsorbent molecules to preferentially occupy the Lewis acid sites on the surface of the Ni catalyst, competitively blocking the polymerization pathway of CPD. At the same time, due to the extremely low dosage and the strict control of contact time and temperature, it does not interfere with the activation reaction intensity of H2 on the Ni active sites of the Ni / γ-Al2O3 catalyst and the main hydrogenation reaction rate of the feedstock oil.

[0024] The present invention will be described in detail below with reference to specific embodiments. It should be noted that these embodiments are only used to explain the present invention and do not constitute any limitation on the scope of protection of the present invention. Those skilled in the art can make adaptive adjustments to the embodiments based on their understanding of the technical solutions of the present invention, and these adjustments still fall within the scope of protection of the present invention.

[0025] Example 1 This embodiment provides a method for hydrorefining C5 fraction oil from petroleum cracking, including the following steps: S1: Take 102 parts of industrial petroleum cracked C5 fraction oil, with a CPD / DCPD conversion content of 10%, and add 10% NaOH aqueous solution at an oil-water volume ratio of 1:0.2. Stir at 50℃ for 45 min, and after stirring, let stand for 2 h to separate the layers. Remove the aqueous phase to obtain the alkaline washed oil phase. Subsequently, the alkaline washed oil phase is subjected to adsorption treatment through a fixed bed adsorber packed with activated alumina at an adsorption temperature of 60℃ and a liquid hourly space velocity of 3 h⁻¹. -1 After adsorption treatment, purified raw material oil is obtained, and the CPD / DCPD conversion content is the conversion content of cyclopentadiene and dicyclopentadiene. S2: Prepare 1 part of N-methylpyrrolidone and 0.00005 parts of sodium ethoxide, and stir at 25℃ and 500r / min for 40min to obtain a polar competitive adsorbent. S3: γ-Al2O3 was impregnated in 0.25 mol / L citric acid solution for 2 h. After impregnation, it was dried at 120 °C for 10 h, and then heated to 500 °C at a heating rate of 2 °C / min and calcined for 5 h to obtain a porous γ-Al2O3 support. Ni(NO3)2·6H2O was dissolved in deionized water to prepare a 3 mol / L nickel nitrate solution. The above porous γ-Al2O3 support was added to the nickel nitrate impregnation solution for impregnation for 3 h. After impregnation, it was dried at 120 °C for 10 h, and then heated to 500 °C at a heating rate of 2 °C / min and calcined for 5 h. After calcination, it was reduced in 99% pure hydrogen at 420 °C for 6 h to obtain a low-acid porous Ni / γ-Al2O3 catalyst. S4: The low-acid, expanded-pore Ni / γ-Al2O3 catalyst obtained in step S3 is packed into a fixed-bed hydrogenation reactor; 103 parts of the purified feedstock oil obtained in step S1 are taken, and 0.0003 parts of the polar competitive adsorbent obtained in step S2 are added. The mixture is pre-contaminated for 5 minutes at 50℃ and 400 r / min to obtain pre-contaminated feedstock oil; then, hydrogen is introduced into the fixed-bed hydrogenation reactor to ensure a hydrogen concentration of 99%; the pre-contaminated feedstock oil is continuously fed into the fixed-bed hydrogenation reactor through a metering pump and enters the catalyst bed together with the hydrogen for hydrogenation reaction; the reaction temperature is controlled at 90℃, the reaction pressure at 3.0 MPa, and the liquid hourly space velocity at 2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 250:1, yielding the hydrogenation reaction product; S5: The hydrogenation reaction product obtained in step S4 is sent to a gas-liquid separator for gas-liquid separation at a temperature of 30°C and a pressure of 2.8 MPa. After the gas-liquid phase separation is completed, the obtained liquid phase is recovered. The recovered liquid phase is sent to a flash tank for flash evaporation at a temperature of 40°C and a pressure of 0.2 MPa to obtain a flash liquid phase. The flash liquid phase is sent to a distillation column for distillation stabilization treatment. The distillation column has 20 theoretical trays, a reflux ratio of 2.0, and a top pressure controlled at 0.15 MPa. The C5 fraction is collected as hydrorefined C5 oil.

[0026] Example 2 This embodiment provides a method for hydrorefining petroleum cracked C5 fraction oil. The difference from Example 1 is that the CPD monomer content in the feed oil is as follows: 102 parts of industrial petroleum cracked C5 fraction oil are taken, and the total CPD / DCPD content of the feed oil is 14%.

[0027] Example 3 This embodiment provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is the weakly alkaline adjusting component of the polar competitive adsorbent in S2, which is as follows: Prepare 1 part of N-methylpyrrolidone and 0.00005 parts of potassium carbonate, and stir for 40 min at 25°C and 500 r / min to obtain the polar competitive adsorbent.

[0028] Example 4 This embodiment provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is that in S3, a low-acid expanded-pore Ni / γ-Al2O3 catalyst with a different pore structure than that in Example 1 is obtained by impregnating γ-Al2O3 in a 0.15 mol / L citric acid solution for 2 h.

[0029] Example 5 This embodiment provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is that in S3, γ-Al2O3 is impregnated in a 0.25 mol / L citric acid solution for 2 h, dried at 120 °C for 10 h after impregnation, and then calcined at 490 °C for 5 h at a heating rate of 2 °C / min to obtain a low-acid expanded-pore Ni / γ-Al2O3 catalyst with a different pore structure than that in Example 1.

[0030] Example 6 This embodiment provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is that in S3, Ni(NO3)2·6H2O is dissolved in deionized water to prepare a 2.5 mol / L nickel nitrate solution, and the expanded γ-Al2O3 support is added to the nickel nitrate solution and impregnated for 3 hours; thus, a low-acid expanded pore Ni / γ-Al2O3 catalyst with a different Ni loading state than that in Example 1 is obtained.

[0031] Comparative Example 1 This comparative example provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is that no polar competitive adsorbent is added, and a Ni / γ-Al2O3 catalyst without pore expansion and low acid site regulation is used.

[0032] Comparative Example 2 This comparative example provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is that the Ni / γ-Al2O3 catalyst in S3 is not subjected to organic acid pore expansion and low acid site regulation. Specifically, the γ-Al2O3 support is directly added to a 3 mol / L nickel nitrate solution for 3 h of impregnation. After impregnation, it is dried at 120 °C for 10 h, and then calcined at 500 °C for 5 h at a heating rate of 2 °C / min. After calcination, it is reduced at 420 °C for 6 h in 99% hydrogen to obtain a conventional Ni / γ-Al2O3 catalyst.

[0033] Comparative Example 3 This comparative example provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is that step S2 is not performed and no polar competitive adsorbent is added.

[0034] Comparative Example 4 This comparative example provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 is the amount of polar competitive adsorbent added in S2, specifically as follows: 103 parts of the purified feedstock oil are taken, and 0.003 parts of the polar competitive adsorbent are added. The mixture is stirred and pre-contacted for 5 minutes at 50°C and 400 r / min to obtain feedstock oil with excess competitive adsorbent pre-contact.

[0035] Comparative Example 5 This comparative example provides a method for hydrorefining C5 fraction oil from petroleum cracking. The difference from Example 1 lies in the order of adding the polar competitive adsorbent in S4, as follows: 103 parts of purified feedstock oil are taken and fed directly into a fixed-bed hydrorefining reactor packed with low-acid expanded-pore Ni / γ-Al2O3 catalyst via a metering pump without adding the polar competitive adsorbent. The adsorbent enters the catalyst bed along with hydrogen for the hydrorefining reaction. After gas-liquid separation, 0.0003 parts of the polar competitive adsorbent are added to the resulting liquid phase product, and the mixture is stirred for 5 minutes at 50°C and 400 r / min.

[0036] Comparative Example 6 This comparative example provides a method for hydrorefining petroleum cracking C5 fraction oil. The difference from Example 1 lies in the CPD / DCPD conversion content of the raw material, as follows: 104 parts of industrial petroleum cracking C5 fraction oil with a CPD / DCPD conversion content of 18.3% were taken as the raw material oil.

[0037] Experimental Example 1 This experiment aims to evaluate the hydrogenation effect of the hydrorefined C5 fraction oils obtained in the examples and comparative examples. The C5 fraction oils prepared using the methods of Examples 1-4 and Comparative Examples 1-6 were analyzed for their components. Each sample group underwent three parallel sampling tests, with 10 mL samples taken to determine the CPD / DCPD equivalent content, alkyne content, gum content, and effective C5 unsaturated components. The CPD / DCPD equivalent content was used to characterize the cyclopentadiene and highly reactive diene loading in the feedstock oil; the alkyne content was used to characterize the hydrogenation effect; the gum content was used to characterize the gum formation tendency of the hydrorefined fraction oil; and the effective C5 unsaturated component retention rate was used to determine whether the hydrorefining process retains its value for subsequent use as a petroleum resin feedstock or for stabilizing C5 resources.

[0038] The CPD / DCPD equivalent content, alkyne content, and effective C5 unsaturated component content were determined using gas chromatography. For testing, standard solutions containing cyclopentadiene, dicyclopentadiene, isoprene, isoprene, and alkyne components were prepared and injected using an autosampler at a volume of 1.0 μL. The injection was performed in a split configuration with a split ratio of 50:1. The injection port temperature was 150℃, and the detector temperature was 250℃. The column temperature program was as follows: initial temperature 35℃, held for 5 min, then increased to 80℃ at 5℃ / min, followed by an increase to 180℃ at 10℃ / min and held for 10 min. The peak area was plotted on the x-axis as the mass concentration of the standard components. A standard curve was plotted with the vertical axis as the ordinate. Subsequently, 10 mL of the sample to be tested was subjected to chromatographic detection under the same conditions. The peak area of ​​the sample was substituted into the standard curve for quantification, and the CPD / DCPD equivalent content, alkyne content, and effective C5 unsaturated component content were calculated. Among them, the CPD / DCPD equivalent content was calculated as the sum of the free cyclopentadiene content and the dicyclopentadiene content, the total alkyne content was calculated as the sum of the contents of each alkyne component and each alkyne component, and the retention rate of effective C5 unsaturated components was calculated as the percentage of the total content of isoprene, isoprene, and the target monoolefin in the hydrogenated sample relative to the total content of the corresponding components in the feedstock oil.

[0039] The gum content was determined by the evaporation residue method. During the test, another 100 mL of the sample to be tested was placed in a clean weighing dish and evaporated at 160℃ to remove volatile hydrocarbon components. The residue was dried to constant weight and weighed to calculate the actual gum content. The results are expressed as mg / 100 mL. The specific results are shown in Table 1.

[0040] Table 1. CPD / DCPD equivalent content, alkyne content, gum content, and retention rate of effective C5 unsaturated components in each sample. From Table 1 and Figure 1-4 It can be seen that the CPD / DCPD equivalent content in the hydrotreated C5 fraction oils obtained in Examples 1-4 is all below 6.0%, the alkyne content is reduced to below 50 mg / kg, and the gum content is reduced to below 2.5 mg / 100 mL. In contrast, the alkyne content in the C5 fraction oils obtained in the comparative examples is all above 50 mg / kg, the gum content is all above 3.4 mg / 100 mL, and the CPD / DCPD equivalent content is higher than that in Examples 1-4. This indicates that the process of the present invention can reduce the formation of highly active unsaturated impurities and gums in the hydrotreated C5 fraction oils. At the same time, the effective C5 unsaturated component retention rate in Examples 1-4 is still maintained in the range of 64.3%-68.5%, indicating that the present invention does not aim to completely saturate all C5 unsaturated components, but rather retains some usable C5 unsaturated components while reducing alkyne, cyclopentadiene polymerization precursors, and gum formation.

[0041] Experiment Example 2 This experiment aims to evaluate the impact of the preparation methods of the examples and comparative examples on the stability of the hydrogenation catalytic reactor. The pressure drop change in the fixed bed within the fixed-bed hydrogenation reactor was measured to verify the inhibitory effect of the present invention on deactivation and pressure drop increase in the front section of the bed. During the test, continuous fixed-bed hydrogenation was conducted according to the process conditions of Examples 1-4 and Comparative Examples 1-6, respectively. All experiments used fixed-bed hydrogenation reactors of the same specifications, with consistent catalyst loading volume. For reactors without catalyst, a consistent volume of γ-Al₂O₃ was loaded. After the reaction started, the reactor was run for 2 hours to reach a stable state, which was then used as the starting point for continuous operation. During the operation, the reactor inlet and outlet pressures were recorded at 0h, 20h, 50h, and 100h, and the difference between the two was taken as the bed pressure drop. The results are shown in Table 2. Figure 5 As shown.

[0042] Table 2. Test results of pressure drop over time in the fixed bed for each preparation method within 100 h. From Table 2, Figure 5 The results show that after 100 hours of continuous operation, the bed pressure drop in each group of examples increased from a minimum of 0.018 MPa to a maximum of 0.036 MPa, with a pressure drop growth rate of less than 90%. In contrast, after 100 hours of continuous operation, the bed pressure drop in each comparative example increased from a minimum of 0.018 MPa to a maximum of 0.088 MPa, with a pressure drop growth rate generally exceeding 150%. This indicates that under the basic conditions of micro-competitive adsorption and low-acid pore-expanding catalyst, the hydrorefining of C5 distillate oil can maintain a low bed pressure drop growth in a fixed bed, reducing the local enrichment and deposition of CPD components in the bed inlet section.

[0043] Experimental Example 3 This experiment aims to evaluate whether the preparation methods of the examples and comparative examples inhibited the formation of polymer deposits in the inlet section of the fixed-bed hydrotreating reactor. The catalyst beds of Examples 1-4, Comparative Examples 1-3, and Comparative Examples 5-6 were sampled and analyzed in segments after 100 hours of continuous operation. Each sample group was sampled and measured in triplicate. After operation, the feedstock was stopped, and hydrogen was continuously introduced for 30 minutes to remove residual liquid hydrocarbon components from the reactor. Then, nitrogen was switched and the reactor was cooled to below 40°C. After disassembling the fixed-bed hydrotreating reactor, the catalyst bed was divided into two equal sections along the flow direction of the pre-contact feedstock. The reactor consists of three sections: the front section (the first third of the bed closest to the reactor inlet), the middle section (the middle third of the bed), and the rear section (the third of the bed closest to the reactor outlet). Catalyst samples from each section were taken and placed in sealed sample vials to detect changes in soluble colloidal deposits, coke deposits, pore volume, and specific surface area on the catalyst surface. The soluble colloidal deposits characterize the content of toluene-extractable colloidal or oligomeric deposits on the catalyst surface and within the pores; the coke deposits characterize the degree of insoluble carbonaceous deposition; and the pore volume reduction rate characterizes the degree of pore structure loss caused by deposits occupying or blocking the catalyst pores.

[0044] The amount of soluble colloidal deposits was determined by toluene extraction and weighing method. Catalyst samples from each segment were weighed, purged with nitrogen, and dried at 60℃ under nitrogen atmosphere with a purity of not less than 99% for 2 hours until the sample constant weight was 5.000 g. The dried sample was added to 50 mL of toluene and ultrasonically extracted at 40℃ for 30 min. After filtration with filter paper, the extraction was repeated once, and the filtrates from the two filtrations were combined. The combined filtrate was transferred to a pre-weighed round-bottom evaporator and toluene was removed using a rotary evaporator at 60℃ water bath temperature and reduced pressure until no obvious toluene droplets flowed out from the condenser end, and this was maintained for 5 min to obtain non-volatile residues. The residues were dried at 105℃ under 99% nitrogen atmosphere for 30 min until constant weight, and then cooled. After cooling, the mass of the residues was weighed and converted into the mass of soluble colloidal deposits per gram of catalyst.

[0045] The amount of coke deposited was determined by thermogravimetric analysis. Approximately 20 mg of each dried catalyst sample was placed in a thermogravimetric analyzer. The sample was first heated to 120 °C under 99% nitrogen atmosphere and held for 20 min to remove adsorbed water and low-boiling-point volatiles. Then, the temperature was raised to 200 °C and the sample mass was recorded. After raising the temperature to 200 °C, the temperature was raised to 750 °C at a rate of 10 °C / min under normal air conditions. The sample mass at 650 °C was recorded. The amount of coke deposited on the catalyst was calculated by dividing the difference between the sample mass at 200 °C and the sample mass at 650 °C by the sample mass at 200 °C and then multiplying by 100%.

[0046] Pore ​​volume and specific surface area changes were determined using a low-temperature nitrogen adsorption method. Before testing, 1.0 g of dried catalyst sample was degassed under vacuum at 120 °C for 4 h, followed by nitrogen adsorption-desorption testing in liquid nitrogen. The specific surface area was calculated using the BET method. Adsorption data points satisfying the BET linear relationship within the relative pressure P / P0 range of 0.05-0.30 were selected for fitting, and the BET specific surface area was output by the instrument software. The results are expressed in m³. 2 / g represents the adsorption capacity at a relative pressure close to 0.99; the pore volume is calculated based on the adsorption capacity at a relative pressure close to 0.99; the pore volume reduction rate and the specific surface area reduction rate are calculated based on the detection values ​​of the corresponding fresh catalyst. The pore volume reduction rate is equal to the difference between the total pore volume of the fresh catalyst and the total pore volume of the catalyst after operation, divided by the total pore volume of the fresh catalyst and then multiplied by 100%; the specific surface area reduction rate is equal to the difference between the specific surface area of ​​the fresh catalyst and the specific surface area of ​​the catalyst after operation, divided by the specific surface area of ​​the fresh catalyst and then multiplied by 100%. The test results are shown in Table 3-4.

[0047] Table 3. Deposition distribution of catalyst bed in the front, middle and rear sections during the preparation of each sample. Table 4. Deposition of catalyst in the front section of the bed during the preparation of each sample Table 3 shows that the deposits in each group of samples are mainly distributed in the front section of the catalyst bed, indicating that the CPD / DCPD and chain diene components in the C5 fraction of petroleum cracking mainly form a risk of polymerization and deposition in the inlet section of the bed. In Example 1, the mass of soluble colloids in the front, middle and rear sections are 3.8 mg / g, 1.8 mg / g and 1.2 mg / g, respectively. Although the deposition in the front section is higher than that in the middle and rear sections, the overall level is low. In contrast, the deposition in the front section of Comparative Examples 1, 2, 3, 5 and 6 is higher than that in the middle and rear sections, and the overall level is higher than that in Example 1. This indicates that the lack of polar competitive adsorbents, the lack of low-acid pore-expanding catalysts, improper timing of adsorbent addition, or excessively high CPD load of feedstock in the preparation of hydrorefined C5 fraction oil can all lead to increased deposition in the catalyst bed section of the hydrotreating reactor, mainly in the front end of the catalyst bed.

[0048] Further analysis of catalyst deposition at the front end of the bed was conducted. Table 4 shows that in Examples 1-4, the amount of coke deposited in the front section of the catalyst bed was less than 2.5%, the mass of soluble colloid was less than 6 mg / g, and the pore volume reduction rate and specific surface area reduction rate were lower than those of Comparative Examples 1-3, Comparative Example 5, and Comparative Example 6. This indicates that the present invention, by pre-contaminating a trace amount of polar competitive adsorbent before hydrogenation of the feedstock oil, allows the adsorbent to enter the inlet section of the catalyst bed. Combined with a low-acid, pore-expanding Ni / γ-Al2O3 catalyst, it can reduce the local enrichment and deposition of cyclopentadiene / dicyclopentadiene and chain diene components in the inlet section of the bed.

[0049] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A method for hydrorefining C5 fraction oil from petroleum cracking, characterized in that, The steps include the following: S1: The composition of the petroleum cracked C5 fraction oil is analyzed, and then the feed oil is subjected to alkaline washing and adsorption pretreatment to obtain purified feed oil; S2: Prepare a polar competitive adsorbent, wherein the polar competitive adsorbent comprises a polar competitive adsorbent substrate and a weakly alkaline regulating component; S3: Prepare a low-acid expanded-pore Ni / γ-Al2O3 catalyst, wherein the low-acid expanded-pore Ni / γ-Al2O3 catalyst uses expanded-pore γ-Al2O3 as a support and loads Ni active components; S4: The purified feed oil obtained in step S1 is pre-contacted with the polar competitive adsorbent obtained in step S2 before hydrogenation to obtain pre-contact feed oil; then the pre-contact feed oil is continuously fed into a fixed bed hydrogenation reactor filled with the low acid expanded pore Ni / γ-Al2O3 catalyst, and enters the catalyst bed together with hydrogen to carry out hydrogenation reaction to obtain hydrogenation reaction product. S5: The hydrogenation reaction product is subjected to gas-liquid separation, flash evaporation and distillation stabilization to obtain hydrogenated refined C5 fraction oil.

2. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, In step S1, the feedstock oil before hydrogenation reaction contains no more than 15% cyclopentadiene and dicyclopentadiene.

3. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, In step S2, the competitive adsorbent in the polar competitive adsorbent is selected from at least one of N-methylpyrrolidone, ethylene glycol, and sulfolane; the weakly basic adjusting component of the polar competitive adsorbent is selected from at least one of sodium ethoxide, sodium carbonate, and potassium carbonate.

4. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 3, characterized in that: The weakly alkaline adjusting component is added at a rate of 0.001-0.01 parts per 100 parts of purified raw material oil.

5. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, In step S4, the amount of the polar competitive adsorbent added is 0.00005-0.0005 parts per 100 parts of purified raw material oil.

6. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, In step S4, when the feed oil and the polar competitive adsorbent are pre-contacted, the pre-contact temperature is 40-70℃, the pre-contact time is 5-15min, and the stirring speed is 300-600r / min.

7. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, In step S3, the low-acid, expanded-pore Ni / γ-Al2O3 catalyst is prepared according to the following method: The γ-Al2O3 support was impregnated in citric acid solution to expand the pores. After impregnation, it was dried and calcined to obtain the expanded γ-Al2O3 support. The expanded γ-Al2O3 support was impregnated with nickel salt solution. After impregnation, it was dried, calcined and reduced with hydrogen in sequence to obtain the low acid expanded pore Ni / γ-Al2O3 catalyst.

8. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 7, characterized in that: The concentration of the citric acid solution is 0.10-0.35 mol / L, and the impregnation and pore-expansion time is 1-4 h; the nickel salt solution is a nickel nitrate solution with a concentration of 2.0-3.5 mol / L, and the impregnation time is 2-5 h.

9. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, In step S4, the hydrogenation reaction is carried out at a temperature of 80-110℃, a pressure of 2.0-4.0 MPa, and a liquid hourly space velocity of 1.0-3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 150:1-350:

1.

10. The method for hydrorefining C5 fraction oil from petroleum cracking according to claim 1, characterized in that, The total alkyne content in the obtained hydrotreated C5 fraction oil is not higher than 50 mg / kg, the actual gum content is not higher than 3.0 mg / 100 mL, and the retention rate of effective C5 unsaturated components is not less than 60%.

Images