Method for deep hydrofining of kerosene fraction

Abstract

The invention discloses a kerosene fraction deep hydrofining method which comprises the following steps: a fixed bed reactor is provided with a first catalyst bed layer and a second catalyst bed layer from top to bottom, the first catalyst bed layer is filled with a hydrogen activation catalyst, and the second catalyst bed layer is filled with a hydrofining catalyst; hydrogen I enters the reactor from the top of the reactor, is in contact with the first catalyst bed layer and is dissociated into active hydrogen, and the active hydrogen enters the second catalyst bed layer through surface diffusion; the hydrogen II and the kerosene fraction raw material are mixed and enter the reactor from the space between the first catalyst bed layer and the second catalyst bed layer, the active hydrogen, the hydrogen II and the kerosene fraction raw material are subjected to hydrogenation reaction in the second catalyst bed layer, and the hydrogenation reaction product flows out from the bottom of the reactor. According to the method disclosed by the invention, the high-efficiency removal of sulfur and nitrogen from the kerosene fraction can be realized under the conditions that the reaction conditions are milder, the chemical hydrogen consumption is smaller and the air speed is larger, and the sulfur content and the nitrogen content of the obtained refined oil are both less than 1ppm.

Description

Technical Field

[0001] This invention belongs to the field of distillate oil hydrorefining, specifically, it is a method for hydrorefining kerosene feedstock upstream of straight-chain alkylbenzenes. Background Technology

[0002] C10–C14 straight-chain olefins undergo alkylation with benzene to yield straight-chain alkylbenzenes, which are key intermediates in the synthesis of detergents. Currently, the main industrial process for producing straight-chain alkylbenzenes involves an upstream atmospheric pressure unit producing a straight-run kerosene fraction. This kerosene fraction undergoes molecular sieve dewaxing to obtain straight-chain alkanes. The straight-chain alkanes are then dehydrogenated using a specific catalyst to obtain a mixture of straight-chain alkanes and olefins (with a straight-chain olefin mass fraction of approximately 10%). Finally, the straight-chain alkanes and olefins, along with benzene, undergo alkylation to produce straight-chain alkylbenzenes. Straight-chain alkanes that did not participate in the alkylation reaction are separated by a fractionation unit for recycling.

[0003] Because molecular sieve dewaxing and straight-chain alkane dehydrogenation processes have high requirements for feedstock properties, deep hydrodesulfurization and denitrification of upstream kerosene fractions are necessary. After hydrotreating, the sulfur and nitrogen content of the kerosene must both be less than 1 ppm, thus requiring high-level deep desulfurization and denitrification capabilities. With the deterioration of crude oil quality, the sulfur and nitrogen content of kerosene fractions is increasing, and with the development of solid acid alkylation, future alkylation units will have increasingly stringent requirements for the quality of upstream kerosene feedstocks. Therefore, improving the deep hydrorefining effect of kerosene, utilizing kerosene for high-value-added products, and promoting "oil conversion" are of great significance.

[0004] CN101942334B discloses a method for producing molecular sieve dewaxing feedstock. Although the kerosene refining fraction in this patent can meet the feed requirements of downstream equipment, the patent is still a traditional trickle bed process, which is not efficient enough in utilizing hydrogen, and the reaction conditions are harsh, with high reaction pressure, high reaction temperature, and small throughput.

[0005] CN114456840B discloses a method for producing high-quality jet fuel. This patent uses kerosene distillate as raw material to produce high-quality jet fuel. The method involves multiple reaction zones, making the equipment more complex. Furthermore, the hydrogenated products often fail to meet the requirement of sulfur and nitrogen content being less than 1 ppm, and the refined oil cannot meet the quality requirements of straight-chain alkylbenzenes for upstream kerosene feedstocks. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for deep hydrorefining of kerosene fractions. This method enables efficient removal of sulfur and nitrogen from kerosene fractions under milder reaction conditions, lower chemical hydrogen consumption, and higher space velocity, resulting in refined oil with sulfur and nitrogen contents of less than 1 ppm.

[0007] The deep hydrorefining method for kerosene fractions of the present invention includes the following steps: a fixed-bed reactor is provided with a first catalyst bed and a second catalyst bed from top to bottom, wherein the first catalyst bed is filled with a hydrogen-activated catalyst and the second catalyst bed is filled with a hydrorefining catalyst; hydrogen I enters the reactor from the top of the reactor, contacts the first catalyst bed, dissociates into active hydrogen, and diffuses into the second catalyst bed through the surface; hydrogen II is mixed with the kerosene fraction feedstock and enters the reactor between the first and second catalyst beds; the active hydrogen, hydrogen II, and the kerosene fraction feedstock undergo a hydrorefining reaction in the second catalyst bed, and the hydrorefining reaction product flows out from the bottom of the reactor.

[0008] In the method of the present invention, the kerosene fraction feedstock has a distillation range of 150℃ to 320℃, more preferably 180℃ to 270℃, and a sulfur content greater than 4000ppm and a nitrogen content greater than 30ppm.

[0009] In the method of this invention, the hydrogen activation catalyst has a strong hydrogen dissociation function and can activate hydrogen at a relatively low temperature (150℃~250℃). It is generally a noble metal catalyst, with alumina as the support and Pt and / or Pd as the active component. The content of the active component in the catalyst, by weight, is not less than 0.1%, generally 0.1%~1.5%, preferably the HDO-18 catalyst developed by FRIPP. Before use, the catalyst is reduced and activated, with the first catalyst bed placed in a hydrogen gaseous atmosphere.

[0010] In the method of the present invention, based on the total amount of catalyst loaded in the reactor, the amount of catalyst loaded in the first catalyst bed is 1% to 30%, preferably 10% to 20%; the reaction temperature is 100℃ to 300℃, preferably 150℃ to 250℃; and the reaction pressure is 1.0MPa to 4.0MPa, preferably 1.5MPa to 3.0MPa.

[0011] In the method of this invention, the hydrorefining catalyst is a conventional kerosene hydrorefining catalyst of the Mo-Ni or Mo-Co type, such as the FH series light oil hydrorefining catalyst developed by FRIPP. Further, the FH-40C catalyst with higher hydrorefining and de-olefinization activity is preferred.

[0012] In the method of this invention, based on the total catalyst loading in the reactor, the catalyst loading of the second catalyst bed is 70%–99%, preferably 80%–90%; the reaction temperature is 100℃–300℃, preferably 150℃–250℃; and the volume hourly space velocity is 2.0 h⁻¹. -1 ~7.0h -1 Preferably 3.0h -1 ~5.0h -1The reaction pressure is 1.0 MPa to 4.0 MPa, preferably 1.5 MPa to 3.0 MPa.

[0013] In the method of this invention, the ratio of the total amount of hydrogen to the volume of kerosene feedstock is called the hydrogen-to-oil ratio (hydrogen volume under standard conditions), which is 50:1 to 300:1, preferably 100:1 to 200:1. Hydrogen I accounts for 10% to 40% of the total hydrogen (the total amount of hydrogen I and hydrogen II), preferably 20% to 30%.

[0014] Because the chemical hydrogen consumption for hydrodesulfurization and denitrification is relatively low, the amount of hydrogen required for the hydrogenation reaction is small, and the hydrogen-to-oil volume ratio required for the hydrogenation reaction is small, this invention eliminates the need for a hydrogen recirculation compressor, and hydrogen is supplied through a single-pass process. This invention activates a portion of the hydrogen on a noble metal catalyst before it diffuses into the conventional hydrogenation catalyst bed and participates in the hydrogenation reaction with the kerosene feedstock. The activation of the hydrogen and the hydrogenation reaction occur in different regions of the reactor, significantly different from traditional trickle-bed or liquid-phase hydrogenation processes. Since some hydrogen is first dissociated and activated in the noble metal catalyst bed, the direct hydrogenation activity of the conventional hydrogenation catalyst in the lower bed is enhanced, increasing the ability to hydrolyze kerosene and perform hydrodesulfurization, thus making the reaction conditions more moderate. Therefore, this invention has high desulfurization and denitrification efficiency, the amount of hydrogen entering different catalyst beds can be flexibly adjusted, hydrogen utilization efficiency is higher, and process parameters are more flexible to adjust. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the deep hydrorefining method for kerosene fractions according to the present invention.

[0016] Among them, 1-kerosene fraction feedstock; 2-hydrogen II; 3-hydrogen I; 4-first catalyst bed; 5-second catalyst bed; 6-refined oil. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, but this does not limit the invention. The reduction conditions for the noble metal catalyst are: reduction under a hydrogen atmosphere, a gas-to-catalyst ratio of 100, a temperature of 150°C, and a constant temperature reduction for 5 hours.

[0018] Examples 1-4 A 100 mL fixed-bed apparatus was used. The first catalyst bed (upper bed) was filled with 20 mL of HDO-18 noble metal catalyst, and the second catalyst bed (lower bed) was filled with 80 mL of FH-40C hydrorefining catalyst. Figure 1 As shown, the feed was introduced at the midpoint between the first and second catalyst beds. Catalyst properties are shown in Table 1, and kerosene feedstock properties are shown in Table 2. Reaction conditions and results are shown in Table 3.

[0019] Examples 5-8 A 100 mL fixed-bed reactor was used. The first catalyst bed was loaded with HDO-18 noble metal catalyst, and the second catalyst bed was loaded with FH-40C hydrorefining catalyst. The reaction apparatus was the same as in Examples 1-4, but the loading ratio of the first and second catalyst beds was different to illustrate the effect of different catalyst loading ratios on the hydrodesulfurization and denitrification effects. The reaction conditions and results are shown in Table 4.

[0020] Comparative Examples 1 and 2 A 100 mL fixed-bed apparatus was used. The first catalyst bed was filled with 20 mL of quartz sand (inactive for hydrogen dissociation), and the second catalyst bed was filled with 80 mL of FH-40C hydrorefining catalyst. The reaction apparatus and raw materials were the same as in Examples 1-4. This was used to illustrate the overall hydrodesulfurization and denitrification efficiency of the apparatus when the noble metal catalyst in the first catalyst bed was not used to dissociate and activate the upper catalyst bed with hydrogen. The reaction conditions and results are shown in Table 5.

[0021] Comparative Example 3 A 100 mL fixed-bed apparatus was used, with both the first and second catalyst beds packed with FH-40C hydrorefining catalyst. The reaction apparatus and raw materials were the same as in Examples 1-4. This was used to illustrate whether hydrogen could be effectively activated when the first catalyst bed was dissociated and activated using a conventional kerosene hydrorefining catalyst, and the overall hydrodesulfurization and denitrification effect of the apparatus. The reaction conditions and results are shown in Table 5.

[0022] Comparative Example 4 A 100 mL fixed-bed reactor was used, with both the first and second catalyst beds packed with FH-40C hydrorefining catalyst. Hydrogen and kerosene feedstocks entered the reactor from the top, and the reaction products flowed out from the bottom. This demonstrates the overall hydrodesulfurization and denitrification efficiency of the unit using a conventional kerosene hydrotreating process. The reaction conditions and results are shown in Table 5.

[0023] Table 1. Physicochemical properties of catalysts

[0024] Table 2 Properties of Kerosene Feedstock

[0025] Table 3 shows the hydrogenation process conditions and results for Examples 1-4.

[0026] As shown in Tables 3 (Examples 1-4), the refined oils all meet the quality requirements of downstream units for kerosene, with sulfur and nitrogen contents all less than 1 ppm. Furthermore, the higher the proportion of hydrogen in the upper bed, the better the hydrodesulfurization and denitrification effects. Examples 1-4 all demonstrate that the present invention can be used for deep hydrorefining of kerosene. The reaction conditions of this invention are mild, and it has excellent desulfurization and denitrification effects.

[0027] Table 4 shows the hydrogenation process conditions and results for Examples 5-8.

[0028] As shown in Tables 4 (Examples 5-8), under the same conditions, different catalyst loading ratios result in better hydrodesulfurization and denitrification effects with a higher amount of precious metal catalyst in the first bed. This indicates that a higher amount of precious metal catalyst leads to better hydrogen dissociation and more active hydrogen diffuses to the second catalyst bed, resulting in better deep hydrorefining and lower sulfur and nitrogen content in the refined oil. However, a higher amount of precious metal catalyst increases costs and reduces the amount of kerosene hydrorefining catalyst required. Therefore, the catalyst loading ratio needs to be flexibly selected based on actual production conditions.

[0029] Table 5 shows the hydrogenation process conditions and results for Comparative Examples 1–4.

[0030] As shown in Table 5, Comparative Examples 1 and 2 both have sulfur contents greater than 40 ppm and nitrogen contents greater than 1 ppm. The sulfur and nitrogen contents of the refined oil do not meet the quality requirements of downstream equipment for kerosene. Comparing Comparative Examples 1 and 2 with Examples 1 and 2, it is clear that under the same conditions, the sulfur and nitrogen contents of the refined oil in the comparative examples are significantly higher than those in the corresponding examples. This demonstrates that the present invention can significantly improve the deep hydrorefining effect of kerosene fractions.

[0031] As shown in Table 5, Comparative Example 3, when the first catalyst bed was filled with FH-40C hydrogenation catalyst, the sulfur and nitrogen content of the refined oil was significantly higher than that in Example 1. This indicates that the first catalyst bed filled with FH-40C hydrogenation refining catalyst cannot dissociate and activate hydrogen in the gas phase, and cannot improve the deep hydrogenation refining effect of kerosene feedstock.

[0032] As shown in Comparative Example 4 in Table 5, the kerosene processing capacity of Comparative Example 4 and Example 1 is the same, both at 258.6 g / h. The sulfur and nitrogen content of the refined oil is higher in Comparative Example 4 than in Example 1. The deep hydrorefining effect of Example 1 using the present invention is significantly better than that of Comparative Example 4. However, the loading amount of the kerosene hydrorefining catalyst FH-40C in the entire reactor in Example 1 is 80% of that in Comparative Example 4, while the loading amount of the precious metal catalyst is only 20%. This indicates that, compared with the traditional process, although the loading amount of the precious metal catalyst occupies more reactor volume, resulting in a reduction in the kerosene hydrorefining catalyst loading, the increased direct hydrogenation capacity means that the processing capacity of the kerosene will not decrease when the refined oil product meets the quality requirements of downstream units. Furthermore, the desulfurization and denitrification capabilities are significantly enhanced. Since the hydrogen I ratio is flexibly adjustable, the feedstock oil processing capacity of the unit can also be adjusted accordingly. In conclusion, the present invention improves the deep hydrorefining effect of kerosene without reducing the feedstock oil processing capacity.

[0033] In summary, this invention exhibits strong direct hydrogenation capability and excellent desulfurization and denitrification effects. Using this invention, deep hydrorefining of kerosene can be achieved, enabling flexible and efficient production of kerosene that meets the quality requirements of downstream equipment under mild conditions.

Claims

1. A method for deep hydrorefining of kerosene fractions, characterized in that... The reactor comprises the following components: a fixed-bed reactor with a first catalyst bed and a second catalyst bed arranged from top to bottom. The first catalyst bed is filled with a hydrogen-activated catalyst, and the second catalyst bed is filled with a hydrorefining catalyst. Hydrogen I enters the reactor from the top, contacts the first catalyst bed, dissociates into active hydrogen, and diffuses into the second catalyst bed through the surface. Hydrogen II is mixed with kerosene fraction feedstock and enters the reactor between the first and second catalyst beds. The active hydrogen, hydrogen II, and kerosene fraction feedstock undergo a hydrogenation reaction in the second catalyst bed, and the hydrogenation reaction products flow out from the bottom of the reactor.

2. The method according to claim 1, characterized in that: The kerosene distillate feedstock has a distillation range of 150℃ to 320℃, and more preferably a distillation range of 180℃ to 270℃.

3. The method according to claim 1, characterized in that: The kerosene distillate feedstock has a sulfur content greater than 4000 ppm and a nitrogen content greater than 30 ppm.

4. The method according to claim 1, characterized in that: The hydrogen activation catalyst described above has a strong hydrogen dissociation function and can activate hydrogen at 150℃~250℃.

5. The method according to claim 1, characterized in that: The hydrogen-activated catalyst is a noble metal catalyst, with alumina as the support and Pt and / or Pd as the active components. The content of the active components in the catalyst by weight is not less than 0.1%. The catalyst is reduced and activated before use, and the first catalyst bed is in a hydrogen gas phase atmosphere.

6. The method according to claim 1, characterized in that: Based on the total catalyst loading in the reactor, the catalyst loading of the first catalyst bed is 1% to 30%, preferably 10% to 20%; the reaction temperature is 100℃ to 300℃, preferably 150℃ to 250℃; and the reaction pressure is 1.0MPa to 4.0MPa, preferably 1.5MPa to 3.0MPa.

7. The method according to claim 1, characterized in that: The hydrogenation refining catalyst is a Mo-Ni or Mo-Co type kerosene hydrogenation catalyst.

8. The method according to claim 1, characterized in that: Based on the total catalyst loading in the reactor, the catalyst loading of the second catalyst bed is 70%–99%, preferably 80%–90%; the reaction temperature is 100℃–300℃, preferably 150℃–250℃; and the volume hourly space velocity is 2.0 h⁻¹. -1 ~7.0h -1 Preferably 3.0h -1 ~5.0h -1 The reaction pressure is 1.0 MPa to 4.0 MPa, preferably 1.5 MPa to 3.0 MPa.

9. The method according to claim 1, characterized in that: The ratio of the total amount of hydrogen to the volume of kerosene feedstock is called the hydrogen-to-oil ratio (hydrogen is the volume under standard conditions). The hydrogen-to-oil ratio is 50:1 to 300:1, preferably 100:1 to 200:

1.

10. The method according to claim 1, characterized in that: The proportion of hydrogen I in the total hydrogen (total amount of hydrogen I and hydrogen II) is 10% to 40%, preferably 20% to 30%.

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