A method for catalytic gasoline hydrogenation

Abstract

This invention discloses a method for catalytic gasoline hydrogenation, comprising the following steps: (1) subjecting a selective hydrodesulfurization catalyst to in-reactor sulfidation; (2) after sulfidation, introducing a certain amount of CO2 into the reactor; (3) maintaining the atmosphere conditions of step (2), introducing catalytic gasoline feedstock for reaction for a period of time; (4) switching to a hydrogen atmosphere, adjusting the reaction conditions to the selective hydrodesulfurization conditions for catalytic gasoline, and obtaining gasoline products. This method, when used in the selective hydrodesulfurization process of gasoline, can significantly improve the hydrogenation selectivity of catalytic gasoline.

Description

Technical Field

[0001] This invention belongs to the field of clean refining technology, and specifically relates to a catalytic gasoline hydrogenation method. Background Technology

[0002] High sulfur content in finished automotive gasoline directly increases SO2 levels in vehicle exhaust. X Emissions can poison the catalyst in a car's exhaust converter, leading to increased CO and NO emissions. X With the increase in VOCs, reducing the sulfur content in finished gasoline can effectively reduce the emission of harmful substances in vehicle exhaust. Although the traditional hydrodesulfurization (HDS) method can effectively remove organic sulfur compounds, olefins with a low degree of isomerization in FCC gasoline are easily hydrogenated to form alkanes with low octane numbers. During desulfurization, the octane number will inevitably drop sharply, and the hydrogen consumption will also increase significantly.

[0003] CN101724442B discloses a method for reducing octane number loss during deep hydrodesulfurization of gasoline. This method first pre-sulfurizes the catalyst, then performs hydrodesulfurization on inferior gasoline feedstock under hydrodesulfurization conditions. A key feature is the use of low-temperature sulfidation to improve the catalyst's selective hydrodesulfurization performance. CN103773439B discloses a start-up method for a gasoline selective hydrodesulfurization process. This method, after pre-sulfurizing the catalyst, reduces the reaction pressure while replacing the feedstock, maintaining the hydrodesulfurization reaction at a lower pressure for a period before increasing the pressure to normal production conditions. This can shorten the stabilization time of the selective hydrodesulfurization catalyst during the initial start-up phase and improve the selectivity of the catalyst's hydrodesulfurization. While the above methods can improve the selective hydrodesulfurization performance of the catalyst, there is still significant room for improvement in selectivity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for catalytic gasoline hydrogenation. This method, used in the selective hydrodesulfurization process of gasoline, can significantly improve the hydrogenation selectivity of catalytic gasoline.

[0005] The catalytic gasoline hydrogenation method of the present invention includes the following steps: (1) performing in-reactor sulfidation treatment on the selective hydrodesulfurization catalyst; (2) after sulfidation, introducing a certain amount of CO2 into the reactor; (3) maintaining the atmosphere conditions of step (2), introducing catalytic gasoline feedstock for reaction for a period of time; (4) switching to hydrogen atmosphere, adjusting the reaction conditions to the selective hydrodesulfurization conditions of catalytic gasoline for reaction, and obtaining gasoline product.

[0006] In the method of the present invention, before the sulfidation treatment described in step (1), the hydrodesulfurization reactor has completed the conventional operation process before the sulfidation treatment, such as nitrogen gas sealing, catalyst drying, hydrogen replacement, hydrogen gas sealing and establishing hydrogen circulation.

[0007] In the method of the present invention, the sulfidation treatment conditions in step (1) are as follows: the amount of sulfiding agent introduced is 90% to 150% of the theoretical sulfur required by the catalyst; the sulfidation process adopts programmed temperature rise, the temperature is raised to 200 to 230℃ and held at 260 to 290℃ for 4 to 16 hours; the sulfiding agent is generally one or more of carbon disulfide, dimethyl disulfide, methyl sulfide, and n-butyl sulfide.

[0008] In the method of this invention, the selective hydrogenation catalyst comprises a hydrogenation active component and a catalyst support. The hydrogenation active component is a catalyst containing at least one Group VIB metal (molybdenum) and at least one Group VIII metal (cobalt), with the molybdenum and cobalt metals comprising 4%–40% by weight of oxides. The catalyst support is generally alumina, amorphous aluminosilicate, silica, titanium dioxide, etc., and may contain other additives such as P, Si, B, Ti, Zr, Ca, etc. Commercially available catalysts can be used, such as Axens RT-225, ExxonMobil HR-806, and Sinopec (Dalian) Petrochemical Co., Ltd.'s FGH-21 and FGH-31 catalysts. The catalyst typically has a pore volume of 0.45–1.30 mL / g and a specific surface area of ​​180–400 m². 2 / g.

[0009] In the method of the present invention, the amount of CO2 introduced in step (2) is ≥3000μg / g, preferably ≥6000μg / g, based on its concentration in hydrogen gas;

[0010] In the method of the present invention, the catalytic gasoline feedstock introduced in step (3) is at a volume hourly space velocity (VHSV) of 2 to 10 h⁻¹. -1 The preferred volume hourly space velocity is 4-8 h⁻¹. -1 The reaction time is 48~600 hours, preferably 72~480 hours, and the reactor inlet temperature is ≥280℃, preferably ≥290℃;

[0011] In the method of this invention, the hydrodesulfurization conditions in step (4) are: reaction pressure 1.0~3.0 MPa, reaction temperature 250~300℃, and volume hourly space velocity 2.0~5.0 h⁻¹. -1 The volume ratio of hydrogen to oil is 200:1 to 500:1.

[0012] In the method of this invention, after the sulfidation in step (2) is completed, the hydrogen sulfide concentration in the hydrogen gas is generally replaced by hydrogen circulation, which is ≤300 mg / m³. 3 Preferred concentration ≤100mg / m³ 3.

[0013] In the method of the present invention, the CO2 content in the hydrogen atmosphere of steps (1) and (4) is generally ≤20μg / g, preferably ≤10μg / g.

[0014] This invention cleverly utilizes the different active sites on the catalyst in the hydrodesulfurization reaction and the olefin hydrogenation saturation reaction. A large amount of acidic CO2 molecules are adsorbed onto the active sites of the hydrodesulfurization reaction. When catalytic gasoline feedstock is introduced at a relatively high reaction temperature, carbon deposit formation on the catalyst is accelerated. Because a large number of CO2 molecules are adsorbed onto the active sites of the hydrodesulfurization reaction, more carbon deposits cover the active sites of the olefin hydrogenation saturation reaction, thus reducing the activity of the olefin hydrogenation saturation reaction. Since the adsorption of CO2 molecules on the catalyst is recoverable, when the CO2 content in the hydrogen gas returns to ≤20 μg / g, the hydrodesulfurization reaction activity of the catalyst is restored. However, at this time, the activity of the olefin hydrogenation saturation reaction has been inhibited, thereby significantly improving the selectivity of catalytic gasoline hydrodesulfurization. This method only increases the CO2 content in the hydrogen gas during the catalyst activity stabilization stage after start-up sulfidation, which is easily controlled by the refinery. After a short period of initial catalyst activity stabilization, the CO2 content in the hydrogen gas is then controlled back to a lower level, thus achieving the goal of improving the selectivity of catalytic gasoline hydrogenation. The method is simple and the effect is significant. Detailed Implementation

[0015] The following examples illustrate the effects of specific methods for improving the selectivity of catalytic gasoline hydrogenation, but do not constitute a limitation on the method of this invention. The catalyst used is FGH-31 catalyst from Sinopec (Dalian) Petrochemical Co., Ltd., and its properties are shown in Table 1. The comparison results of the catalytic gasoline hydrogenation selectivity of the examples and comparative examples are shown in Table 2.

[0016] Table 1 Properties of FGH-31 catalyst

[0017] project index Analytical methods Active metals <![CDATA[MoO3+CoO]]> Colorimetric method shape cylindrical Visual inspection Size, mm Ф (1.3~1.6)×(3~8) calipers Lateral compressive strength, N / cm ≮80 Progressive strength tester Bulk density, g / mL 0.70～0.80 graduated cylinder method Pore ​​volume, mL / g ≮0.40 Low-temperature nitrogen adsorption <![CDATA[Specific surface area, m 2 / g]]> ≮210 Low-temperature nitrogen adsorption Example 1

[0018] (1) After establishing the hydrogen circulation, the reactor inlet temperature was raised to 230℃ and kept at a constant temperature for 8 hours for sulfurization. Then, the reactor inlet temperature was raised to 280℃ and kept at a constant temperature for 8 hours for sulfurization. The circulating hydrogen H2S concentration was 11000 mg / m³. 3 (1) The CO2 content in the hydrogen gas is controlled at 5 μg / g during the sulfidation process; (2) The concentration of hydrogen sulfide in the replaced hydrogen gas is 90 mg / m³ after sulfidation. 3 The CO2 content is 6900 μg / g, and it is fed into a catalytic gasoline feedstock with a volumetric space velocity of 5 h⁻¹. -1, The reactor inlet temperature is controlled at 300℃; (3) After 240 hours of introducing catalytic gasoline feedstock, the CO2 content in hydrogen is restored to 5μg / g, and the reactor inlet temperature drops to the actual reaction temperature for normal production. Example 2

[0019] Same as Example 1, except that the CO2 content in step (2) is 4700 μg / g. Example 3

[0020] Same as Example 1, except that in step (3), catalytic gasoline feedstock is introduced for 390 hours. Example 4

[0021] Same as Example 2, except that in step (3), the volume space velocity of the catalytic gasoline feedstock is 6h. -1 The reactor inlet temperature is controlled at 290℃.

[0022] Comparative Example 1

[0023] Same as Example 1, except that the CO2 content in step (2) is 5 μg / g.

[0024] Comparative Example 2

[0025] Same as Example 1, except that in step (3), catalytic gasoline feedstock is introduced for 24 hours.

[0026] Comparative Example 3

[0027] Same as Example 1, except that the reactor inlet temperature is controlled at 250°C in step (3).

[0028] Comparative Example 4

[0029] Same as Example 1, except that in step (3), the volume space velocity of the catalytic gasoline feedstock is 1 h⁻¹. -1 .

[0030] Table 2 Comparison of Selectivity of Hydrogenation of Catalytic Gasoline

[0031] project raw material Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Octane number, RON 93.0 92.4 92.3 92.5 92.4 91.7 91.8 91.9 91.9 Sulfur content, μg / g 664 7.1 7.0 7.2 7.2 6.9 7.0 7.0 6.9 Multidimensional chromatographic composition Olefins, % 36.0 34.8 34.7 34.9 34.8 33.4 33.7 33.6 33.7

[0032] Note: Reaction conditions: P = 1.6 MPa, H2 / Oil = 300 Nm 3 / m 3 Volumetric hourly space velocity = 3.0 h -1 Average reactor temperature: 270℃;

[0033] Table 2 lists the comparative results of the selectivity of catalytic gasoline hydrogenation. It shows that using the method of the present invention to improve the selectivity of catalytic gasoline hydrogenation, the desulfurization activity of the catalyst is comparable, the olefin saturation rate is significantly reduced, and the octane number loss is small. The method of the present invention to improve the selectivity of catalytic gasoline hydrogenation significantly improves the selective hydrogenation reaction performance of the catalyst.

Claims

1. A method for catalytic hydrogenation of gasoline, characterized in that... The process includes the following steps: (1) treating the selective hydrodesulfurization catalyst in the reactor; (2) after the sulfurization is completed, introducing a certain amount of CO2 into the reactor; (3) maintaining the atmosphere conditions of step (2), introducing catalytic gasoline feedstock for a period of time; (4) switching to a hydrogen atmosphere, adjusting the reaction conditions to the selective hydrodesulfurization conditions of catalytic gasoline, and obtaining gasoline products; the amount of CO2 introduced in step (2) is ≥3000 μg / g based on its concentration in hydrogen; the amount of catalytic gasoline feedstock introduced in step (3) is a volume hourly space velocity of 2~10 h⁻¹. -1 The reaction time is 48~600 hours, and the reactor inlet temperature is ≥280℃; in the hydrogen atmosphere of steps (1) and (4), the CO2 content is ≤20μg / g.

2. The method according to claim 1, characterized in that: Before the sulfidation treatment described in step (1), the hydrodesulfurization reactor has completed nitrogen gas sealing, catalyst drying, hydrogen replacement, hydrogen gas sealing and established hydrogen circulation.

3. The method according to claim 1, characterized in that: The sulfidation conditions described in step (1) are as follows: the amount of sulfiding agent introduced is 90wt%~150wt% of the theoretical sulfur required by the catalyst; the sulfidation process adopts programmed temperature rise, and the temperature is raised to 200~230℃ and kept at a constant temperature for 4~16h, and then raised to 260~290℃ and kept at a constant temperature for 4~16h; the sulfiding agent is one or more of carbon disulfide, dimethyl disulfide, methyl sulfide, and n-butyl sulfide.

4. The method according to claim 1, characterized in that: The selective hydrodesulfurization catalyst comprises a hydrogenation active component and a catalyst support. The hydrogenation active component is metallic molybdenum and metallic cobalt, with a weight content of 4%–40% based on oxides. The catalyst support is one or more of alumina, amorphous silica-alumina, silica, and titanium oxide. The selective hydrodesulfurization catalyst has a pore volume of 0.45–1.30 mL / g and a specific surface area of ​​180–400 m² / g. 2 / g.

5. The method according to claim 4, characterized in that: Selective hydrodesulfurization catalysts contain one or more of the following additives: P, Si, B, Ti, Zr, and Ca.

6. The method according to claim 1, characterized in that: The amount of CO2 introduced in step (2) is ≥6000 μg / g, calculated based on its concentration in hydrogen.

7. The method according to claim 1, characterized in that: The feed rate of the catalytic gasoline feedstock in step (3) is 4-8 h⁻¹. -1 The reaction time is 72~480 hours, and the reactor inlet temperature is ≥290℃.

8. The method according to claim 1, characterized in that: The hydrodesulfurization conditions described in step (4) are: reaction pressure 1.0~3.0 MPa, reaction temperature 250~300℃, and volume hourly space velocity 2.0~5.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 200:1 to 500:

1.

9. The method according to claim 1, characterized in that: After step (2), the hydrogen sulfide concentration in the hydrogen gas is replaced by hydrogen circulation, with a hydrogen concentration ≤ 300 mg / m³. 3 .

10. The method according to claim 1, characterized in that: In the hydrogen atmosphere of steps (1) and (4), the CO2 content is ≤10μg / g.