A method for starting up a diesel hydrocracking unit

Abstract

The application discloses a starting-up method of diesel oil hydrocracking, and a hydrocracking device comprises a hydroprocessing reaction zone and a hydrocracking reaction zone, the hydroprocessing reaction zone is filled with sulfided hydroprocessing catalyst, and the hydrocracking reaction zone is filled with oxidized hydrocracking catalyst. The starting-up method can directly process diesel oil raw materials, greatly reduces the amount of sulfided agent, and shortens the starting-up time.

Description

Technical Field

[0001] This invention relates to a start-up method for diesel hydrocracking, and more specifically to a low-cost start-up method for diesel hydrocracking. Background Technology

[0002] Most industrial diesel hydrotreating catalysts use metal elements such as Co, Mo, Ni, and W as active components. These metal elements are generally dispersed in oxide form on a porous support. Before use, they need to be pre-sulfurized, that is, in the presence of a sulfiding agent and hydrogen, the active components are converted from the oxidized state to the sulfidized state, thereby improving the activity, stability, and selectivity of the hydrotreating catalyst.

[0003] CN201210432673.5 discloses a start-up method for a hydrocracking unit. The hydrocracking unit's reaction zone is loaded with a sulfide-type hydrocracking catalyst. The start-up process begins with activation oil being heated to a certain temperature via heat exchange and / or heating before passing through the catalyst bed. The temperature is then further increased to 230±15℃ for isothermal activation. At 245±15℃, nitrogen-containing light distillate oil is introduced. When the temperature reaches 290±15℃ or higher, nitrogen-containing heavy distillate oil is introduced. Finally, at 320±15℃, feedstock oil is introduced in stages, and normal production commences.

[0004] CN201110321298.2 discloses a start-up method for a hydrocracking unit. During the wet sulfidation start-up process of the hydrocracking unit, when the reactor is still difficult to heat up even when the heater is operating near full load, an appropriate amount of unsaturated hydrocarbon-rich oil or high-sulfur light oil is added to the low-NOx start-up oil. This fully utilizes the temperature rise generated by the exothermic reaction during the hydrogenation of the unsaturated hydrocarbon-rich oil or high-sulfur light oil to assist in raising the temperature during the wet start-up process.

[0005] CN200810010242.3 discloses a start-up method for a hydrocracking process. The method involves pre-sulfurizing the hydrocracking pre-refining catalyst externally, or not pre-sulfurizing the hydrocracking catalyst externally, or partially pre-sulfurizing it. The amount of sulfur introduced into the pre-sulfurized hydrocracking pre-refining catalyst and the hydrocracking catalyst is 90%–120% of the theoretical sulfur requirement of all catalysts. The pre-sulfurized hydrocracking catalyst and the hydrocracking catalyst are layered and packed in the reactor, followed by heating and activation to ensure effective sulfurization of all catalysts.

[0006] CN111378489A discloses a start-up method for a hydrogenation unit. The start-up method includes the following: (1) The hydrogenation unit includes a hydrorefining reaction zone and a hydrocracking reaction zone, wherein the hydrorefining reaction zone is filled with a sulfidation-type hydrorefining catalyst and the hydrocracking reaction zone is filled with a hydrocracking catalyst; (2) After the catalyst is filled, the hydrogenation unit is sealed; (3) After the sealing is completed, the hydrogenation unit is heated to perform sulfidation; (4) After the sulfidation is completed, the hydrogenation unit is cooled and feedstock oil is introduced to start the hydrogenation reaction.

[0007] CN201010222031.3 discloses a sulfidation method for starting a hydrocracking process, (1) the hydrocracking process includes a hydrocracking pre-refining reactor and a hydrocracking reactor, each reactor uses an oxidized catalyst, and the reactors are subjected to gas replacement, catalyst drying and gas tightness operations; (2) under the catalyst sulfidation operation conditions, after the sulfided oil and hydrogen enter the hydrocracking pre-refining reactor, they enter the gas-liquid separator. The liquid phase separated by the gas-liquid separator is recycled back to the hydrocracking pre-refining reactor and circulates in a closed loop in the hydrocracking pre-refining reactor. The gas phase separated by the gas-liquid separator enters the hydrocracking reactor, and the gas phase discharged from the hydrocracking reactor is recycled back to the hydrocracking pre-refining reactor.

[0008] CN201110353213.9 discloses a wet sulfidation start-up method for a hydrocracking unit, comprising: (a) introducing light distillate working oil at low temperature; (b) introducing a sulfiding agent when the reactor inlet temperature reaches the decomposition temperature of the sulfiding agent; (c) after hydrogen sulfide penetrates the reactor catalyst bed, the temperature is raised according to the conventional hydrocracking catalyst sulfidation process. After the catalyst bed reaches 235-300°C, heavy distillate sulfur-containing start-up oil is introduced, liquid ammonia is introduced, and the introduction of sulfiding agent is stopped; (d) after the heavy distillate sulfur-containing start-up oil is introduced, the final sulfidation process of the catalyst is completed by hydrogen sulfide obtained from the hydrogenolysis reaction of sulfides in the start-up oil; (e) after sulfidation, feedstock oil is directly introduced in stages. When 60%-85% of the feedstock oil is introduced, the introduction of liquid ammonia is stopped, and normal production is resumed.

[0009] CN201711118996.6 discloses a rapid start-up method for a hydrocracking catalyst. The start-up method involves introducing feedstock oil during sulfidation, and after sulfidation, adjusting the reaction temperature to maintain a light oil yield of 35-40% at <360℃, then adjusting to hydrocracking reaction conditions for hydrocracking. The hydrocracking catalyst contains 0%-10% molecular sieve by weight, including but not limited to Y-type or USY-type molecular sieves.

[0010] In summary, existing technologies for hydrogenation catalyst sulfidation can employ two methods: in-reactor presulfidation and external presulfidation. In-reactor presulfidation involves loading the oxidized hydrogenation catalyst into the reactor, then introducing starter oil and a sulfiding agent. Once the sulfiding agent releases sulfur, converting the oxidized hydrogenation catalyst into a sulfidized hydrogenation catalyst, feedstock oil is introduced for reaction. External presulfidation involves pre-selectively introducing the sulfiding agent onto the hydrogenation catalyst through adsorption, then loading the hydrogenation catalyst with the adsorbed sulfiding agent into the reactor, introducing starter oil, and heating to release sulfur from the pre-adsorbed sulfiding agent for sulfidation. After complete sulfidation, feedstock oil is introduced for stable operation. Therefore, both in-reactor and external presulfidation methods generally suffer from drawbacks such as slow start-up processes, the need for large amounts of sulfiding agent, and the inability to directly process feedstock oil. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a start-up method for diesel hydrocracking, which can directly process diesel feedstock, significantly reduce the amount of sulfiding agent used, and shorten the start-up time.

[0012] A start-up method for a diesel hydrocracking unit, comprising a hydrotreating reaction zone and a hydrocracking reaction zone, wherein the hydrotreating reaction zone is filled with a sulfidation-type hydrotreating catalyst, and the hydrocracking reaction zone is filled with an oxidation-type hydrocracking catalyst; the specific start-up steps are as follows:

[0013] (1) The diesel feedstock enters the hydrotreating pretreatment reaction zone for reaction;

[0014] (2) After the reaction in step (1), the material enters the hydrocracking reaction zone. The temperature control of the hydrocracking reaction zone is at least three stages: the first stage operating temperature is 250℃~280℃, preferably 260℃~270℃; constant temperature for 12h~24h, preferably 16h~20h; the second stage operating temperature is 290℃~320℃, preferably 300℃~310℃; constant temperature for 12h~24h, preferably 16h~20h; the third stage operating temperature is 330℃~380℃, preferably 340℃~370℃, and it operates continuously and stably.

[0015] In the above method, the degree of sulfidation of the sulfidation-type hydrotreating catalyst is at least 20%, preferably 30% to 60%, and more preferably 40% to 50%. The degree of sulfidation is defined as the mass percentage of sulfided metals in the catalyst relative to the total metal content.

[0016] In the above method, the preparation process of the sulfide-type hydrotreating catalyst in one embodiment is as follows: the oxidized hydrotreating catalyst is reacted in a mixed atmosphere of hydrogen and hydrogen sulfide to convert part of the oxidized metal into sulfide metal. The reaction pressure is 1.0 MPa to 6.0 MPa, preferably 2.0 MPa to 5.0 MPa; the reaction temperature is 200℃ to 260℃, preferably 220℃ to 240℃; and the reaction time is 2 to 8 hours, preferably 4 to 6 hours.

[0017] In the above method, the upper part of the hydrogenation reaction zone is filled with a sulfidation-type hydrogenation catalyst, and the lower part is filled with an oxidation-type hydrogenation catalyst. The volume ratio of the sulfidation-type hydrogenation catalyst to the oxidation-type hydrogenation catalyst is 1:4 to 4:1, preferably 3:7 to 7:3.

[0018] In the above method, the hydrogenation catalyst comprises a support and a hydrogenation active metal. The support is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous aluminum silicate, silica, or titanium dioxide; the hydrogenation active metal comprises Group VIB and / or Group VIII metal components, wherein the Group VIB component is selected from tungsten and / or molybdenum, and its mass content in the hydrogenation catalyst, based on oxides, is 10%–35%, preferably 15%–30%; and the Group VIII component is selected from nickel and / or cobalt, and its mass content in the hydrogenation catalyst, based on oxides, is 1%–7%, preferably 1.5%–6%.

[0019] In the above method, the operating conditions of the hydrogenation reaction zone in step (1) are as follows: reaction pressure 1.0 MPa~6.0 MPa, preferably 2.0 MPa~5.0 MPa; reaction temperature 200℃~260℃, preferably 220℃~240℃; liquid hourly space velocity 0.5 h⁻¹. -1 ~5.0h -1 1.0h is preferred -1 ~3.0h -1 The hydrogen-to-oil ratio is 200:1 to 2000:1, preferably 400:1 to 1000:1.

[0020] In the above method, the diesel feedstock in step (1) can be one or more of straight-run diesel, coking diesel, catalytic diesel or fluidized bed residue hydrotreated diesel, etc. The sulfur content of the diesel feedstock is 0.5wt%~2wt%, preferably 1wt%~1.5wt%, and the nitrogen content is 0.01wt%~0.1wt%, preferably 0.03wt%~0.05wt%.

[0021] In the above method, the hydrocracking catalyst packed in the hydrocracking reactor in step (2) typically includes a cracking component, a hydrogenation component, and a binder. It can be any suitable hydrocracking catalyst, including those in the prior art. The cracking component typically includes amorphous silica-alumina and / or molecular sieves, commonly using Y-type or USY-type molecular sieves. The binder is typically alumina or silica. The hydrogenation active component is a group VIB and / or group VIII metal.

[0022] In the above method, the operating conditions for hydrocracking in step (2) are as follows: reaction pressure 3.0 MPa~25.0 MPa, preferably 6.0 MPa~15.0 MPa; liquid hourly space velocity 0.1~15.0 h⁻¹. -1 Preferably 0.2–3.0 h -1 The hydrogen-to-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0023] In the above method, the material obtained after stable operation in step (2) is subjected to gas-liquid separation. The hydrogen-rich gas obtained by separation is recycled, and the liquid phase enters the fractionation tower to separate naphtha, jet fuel and diesel.

[0024] Compared with the prior art, the diesel hydrocracking method of the present invention has the following advantages:

[0025] (1) The hydrotreating reaction zone is filled with a sulfurized hydrotreating catalyst, and a small amount and / or a shallowly sulfurized sulfurized hydrotreating catalyst can be further filled. No sulfurization or activation is required during the start-up of diesel hydrocracking. Fresh feedstock is processed directly during the start-up process, and the sulfides in the feedstock are used to deeply sulfurize the catalyst, which greatly shortens the start-up time and saves the amount of sulfurizing agent.

[0026] (2) No passivating agent needs to be injected into the hydrocracking reaction zone, which is beneficial for the passivation of the hydrocracking catalyst by organic nitrogen compounds with relatively simple molecular structures in diesel oil, and the catalyst can be gradually restored to activity by gradually increasing the reaction temperature. The operation process is safe and simple. Detailed Implementation

[0027] The following examples further illustrate the function and effect of the present invention, but the following examples do not constitute a limitation on the method of the present invention. Unless otherwise specified, all percentages in this application are mass percentages.

[0028] In the examples, hydrogenation catalysts with different degrees of sulfidation were prepared by controlling the reaction conditions. The degree of sulfidation was determined as follows: XPS characterization was performed using a photoelectron spectroscopy (PES) instrument. Operating conditions: excitation source MgK... α (1253.6 eV), resolution Ag 3d3 / 2 (Half-width at half maximum 1.15 eV), vacuum level in the analysis chamber higher than 5 × 10⁻⁶ eV.-4 Pa. With contamination of the C peak C 1s (284.6 eV) was used as an internal standard to correct for the charge effect. Data processing and spectral interpretation were both performed by a computer with a dedicated program.

[0029] In this embodiment of the invention, the hydrotreating catalyst is FF-46, and the hydrocracking catalyst is FC-76. Both catalysts are manufactured by Sinopec Catalyst Co., Ltd. The properties of the feedstock are shown in Table 1, the main physicochemical properties of the catalyst are shown in Table 2, and the process conditions and test results of the examples are shown in Table 3.

[0030] Table 1

[0031]

[0032] Table 2

[0033]

[0034] Table 3

[0035]

[0036] As can be seen from the above embodiments, the method of the present invention allows for the direct input of fresh diesel feedstock while obtaining qualified products; it effectively shortens the start-up time and saves on the amount of vulcanizing agent used.

Claims

1. A start-up method for diesel hydrocracking, characterized in that: The hydrocracking unit includes a hydrotreatment reaction zone and a hydrocracking reaction zone. The upper part of the hydrotreatment reaction zone is filled with a sulfide-type hydrotreatment catalyst, and the lower part is filled with an oxidizing hydrotreatment catalyst. The volume ratio of the sulfide-type hydrotreatment catalyst to the oxidizing hydrotreatment catalyst is 1:4 to 4:

1. The hydrocracking reaction zone is filled with an oxidizing hydrocracking catalyst. The specific start-up steps are as follows: (1) Diesel feedstock enters the hydrotreating reaction zone for reaction; (2) After the reaction in step (1), the material enters the hydrocracking reaction zone. The temperature of the hydrocracking reaction zone is controlled in at least three stages: the first stage operating temperature is 250℃~280℃; constant temperature for 12h~24h; the second stage operating temperature is 290℃~320℃; constant temperature for 12h~24h; the third stage operating temperature is 330℃~380℃ and operates continuously and stably. The preparation process of the sulfide-type hydrotreating catalyst is as follows: the oxidized state hydrotreating catalyst is reacted in a mixed atmosphere of hydrogen and hydrogen sulfide to convert part of the oxidized state metal into sulfide state metal. The reaction pressure is 1.0 MPa to 6.0 MPa, the reaction temperature is 200℃ to 260℃, and the reaction time is 2 to 8 hours. During the start-up process, the catalyst is deeply sulfided using sulfides from the diesel feedstock.

2. The method according to claim 1, characterized in that: The temperature control of the hydrocracking reaction zone is at least in three stages: the first stage operating temperature is 260℃~270℃; constant temperature for 16h~20h; the second stage operating temperature is 300℃~310℃; Maintain constant temperature for 16-20 hours; the third stage operating temperature is 340℃-370℃, ensuring continuous and stable operation.

3. The method according to claim 1, characterized in that: The degree of sulfidation of the sulfidation-type hydrogenation catalyst is above 20%.

4. The method according to claim 3, characterized in that: The degree of sulfidation of the sulfidation-type hydrotreating catalyst is 30%~60%.

5. The method according to claim 4, characterized in that: The degree of sulfidation of the sulfidation-type hydrotreating catalyst is 40%~50%.

6. The method according to claim 1, characterized in that: In the preparation of the sulfurized hydrogenation catalyst, the reaction pressure is 2.0 MPa to 5.0 MPa, the reaction temperature is 220°C to 240°C, and the reaction time is 4 to 6 hours.

7. The method according to claim 1, characterized in that: The volume ratio of the sulfidation-type hydrotreating catalyst to the oxidation-type hydrotreating catalyst is 3:7 to 7:

3.

8. The method according to claim 1, characterized in that: The hydrogenation catalyst comprises a support and a hydrogenation active metal. The support is an inorganic refractory oxide, and the hydrogenation active metal comprises Group VIB and / or Group VIII metal components.

9. The method according to claim 1, characterized in that: The operating conditions of the hydrogenation reaction zone in step (1) are as follows: reaction pressure is 1.0 MPa to 6.0 MPa, reaction temperature is 200℃ to 260℃, and liquid hourly space velocity is 0.5 h⁻¹. -1 ~5.0h -1 The hydrogen-to-oil ratio is 200:1 to 2000:

1.

10. The method according to claim 9, characterized in that: The operating conditions of the hydrogenation reaction zone in step (1) are as follows: reaction pressure is 2.0 MPa to 5.0 MPa, reaction temperature is 220°C to 240°C, and liquid hourly space velocity is 1.0 h⁻¹. -1 ~3.0h -1 The hydrogen-to-oil ratio is 400:1 to 1000:

1.

11. The method according to claim 1, characterized in that: The diesel feedstock mentioned in step (1) is one or more of coking diesel, catalytic diesel, or fluidized bed residue hydrotreated diesel.

12. The method according to claim 1, characterized in that: The hydrocracking catalyst packed in the hydrocracking reaction zone in step (2) includes a cracking component, a hydrogenation component, and a binder. The cracking component includes amorphous silica-alumina and / or molecular sieves, the binder is alumina and / or silica, and the hydrogenation active component is VIB and / or group VIII metals.

13. The method according to claim 1, characterized in that: The operating conditions for hydrocracking in step (2) are as follows: reaction pressure is 3.0 MPa to 25.0 MPa, and liquid hourly space velocity is 0.1 to 15.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 100:1 to 2500:

1.

14. The method according to claim 13, characterized in that: The operating conditions for hydrocracking in step (2) are as follows: reaction pressure is 6.0 MPa to 15.0 MPa, and liquid hourly space velocity is 0.2 to 3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 400:1 to 2000:

1.

15. The method according to claim 1, characterized in that: After the material is stabilized in step (2), it is subjected to gas-liquid separation. The hydrogen-rich gas obtained is recycled, and the liquid phase enters the fractionation tower to separate naphtha, jet fuel and diesel.

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