CN111100706B

CN111100706B - Hydrocracking method for producing fuel oil

Info

Publication number: CN111100706B
Application number: CN201811268931.4A
Authority: CN
Inventors: 赵阳; 章然; 赵广乐; 毛以朝
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2018-10-29
Filing date: 2018-10-29
Publication date: 2022-04-08
Anticipated expiration: 2038-10-29
Also published as: CN111100706A

Abstract

A hydrocracking process for producing fuel oil comprising: in the presence of hydrogen, raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel fraction and a tail oil fraction, and part of the tail oil fraction is recycled. The method provided by the invention has the advantages of high device operation efficiency, long period and high selectivity of middle distillate oil in the product.

Description

Hydrocracking method for producing fuel oil

Technical Field

The present invention belongs to a method for cracking hydrocarbon oil in the presence of hydrogen, more specifically to a hydrocracking method for producing high-quality fuel oil.

Background

Hydrocracking technology is one of effective means for crude oil conversion because of its ability to process heavy feedstocks, high liquid yield, good product properties, and flexible product scheme and equipment operation. With the stricter environmental protection requirements worldwide and the heavy and inferior crude oil, the hydrocracking technology is more favored by people as an effective means for environmental protection requirements. From the development trend of foreign oil refining industry, based on the requirements of clean fuel production and integration of oil refining and chemical industry, the application development of the hydrocracking technology is rapid, and the total processing capacity of a hydrocracking device is greatly improved in the primary processing capacity of crude oil. In addition, due to the wide range of hydrocracking raw materials, good product quality and flexible production scheme, the hydrocracking technology can be used by oil refining enterprises to improve the production flexibility and economic benefit, and the application of the hydrocracking technology in the future is more and more extensive.

After the hydrocracking technology is industrially applied from the 50 th of the 20 th century, the target products of the hydrocracking technology are continuously changed along with the market requirements. In the early 60 s, hydrocracking technology was mainly used to produce gasoline and reformate from vacuum light gas oil and catalytically cracked light cycle oil; the market demand for middle distillates such as jet fuel and diesel oil is increasing from the late 60 s to the 70 s; by the end of the 80 s, the hydrocracking unit newly built accounts for 90% of middle distillate oil, and the middle distillate oil fraction mainly comprises aviation kerosene fraction and diesel oil fraction.

The continuous development of national economy of China promotes the rapid improvement of traffic and transportation capacity, and the demand of recent air transportation fuel is increasing. Generally, the aviation kerosene fraction is mainly derived from the following sources: removing mercaptan from the kerosene fraction obtained by the distillation device; the vacuum wax oil is used for producing aviation kerosene through a hydrocracking process. The yield of the aviation kerosene fraction obtained by the distillation device is relatively fixed due to the limitation of crude oil processing capacity and aviation kerosene fraction yield; the hydrocracking process can convert heavy distillate oil into light products, and the yield of the aviation kerosene can be flexibly changed in a large range by means of adjusting operation, improving the selectivity of the catalyst, improving the process flow and the like.

Diesel oil is the engine fuel with the largest consumption in China, and has a great relation with the nation's countrymen. With the increase of the processing capacity of crude oil in China, the yield of light diesel oil is increased year by year, but with the continuous improvement of environmental protection and requirements, the specification requirements of people on vehicle fuel, especially diesel oil, are higher and higher. In the latest fuel specification worldwide, the diesel fuel index is strictly controlled, the sulfur content in the Euro IV emission standard which is implemented in the beginning of the European 2005 is required to be reduced to below 50 mug/g, and the sulfur content in the Euro V standard which is implemented in the 2009 is further reduced to below 10 mug/g. Meanwhile, strict regulations are made on various standard polycyclic aromatic hydrocarbons, cetane numbers and the like, for example, the cetane number of diesel oil is not less than 51, and the content of polycyclic aromatic hydrocarbons is not more than 11% by volume. In recent years, diesel indexes are started in China, the national III diesel indexes basically equivalent to Euro III are started in 2010, and the more rigorous national IV diesel indexes are planned to be implemented in 2012.

At present, catalytic diesel oil, coking diesel oil and visbreaking diesel oil can not meet the requirements of clean diesel oil on sulfur content, aromatic hydrocarbon content and cetane number, even straight-run diesel oil has a considerable part which is difficult to meet the specification requirements of EuroIV and EuroV, and the diesel oil blending component needs to be subjected to deep hydrodesulfurization and/or deep hydrogenation dearomatization. But the hydrocracked diesel oil can meet the above requirements.

In view of this situation, hydrocracking technology for maximum production of middle distillates is of practical significance for future demand.

USP4,172,815 discloses a single stage cycle hydrocracking process for the simultaneous production of aviation kerosene and diesel fuel having a feedstock with an initial boiling point greater than 500 ° f (about 260 ℃). The process flow is simply described as follows: hydrocracking raw oil at a reaction temperature of less than 900 ℉ (about 482 deg.C) and a pressure of greater than 1000psig (about 6.9MPa), fractionating the reaction effluent to obtain naphtha fraction, aviation kerosene fraction, diesel oil fraction and tail oil, mixing all or part of the aviation kerosene fraction with the tail oil, and returning the mixture to the cracking reaction zone. The method can achieve the aim of producing aviation kerosene and diesel oil to the maximum extent at the same time under mild hydrocracking conditions, and the quality of aviation kerosene is improved.

CN 1075551C describes a hydrocracking process for producing middle distillate. The method adopts a high and medium distillate type nitrogen-resistant hydrocracking catalyst, and the hydrocracking process allows high nitrogen feeding in a cracking section, has high medium oil selectivity, and can be used for producing medium distillate.

CN 1202216C describes a hydrocracking process for maximum production of middle distillates. The method designs a one-stage series hydrocracking process for producing the middle oil to the maximum extent, heavy petroleum hydrocarbon subjected to hydrofining contacts a first hydrocracking catalyst containing beta zeolite firstly, then contacts a second hydrocracking catalyst containing Y zeolite, the hydrocracking catalyst containing the beta zeolite bears main cracking load, unconverted tail oil is completely circulated, and the second hydrocracking catalyst containing the Y zeolite and having better ring-opening performance compared with the beta zeolite catalyst plays a role in supplementary cracking.

Shell company has already proposed a kind of hydrocracking process which allows the high nitrogen to feed, the characteristic is that this process uses the commercial anti-nitrogen type hydrocracking catalyst Z-763, this hydrocracking catalyst allows the nitrogen content of feed to be 30-50 mug/g, but the use mode is packed in the upper bed layer of the reactor of cracking stage, this has improved the adaptability to the heavy raw materials of inferior quality and ability to cope with the harsh reaction condition in the whole hydrocracking process, but the catalyst of different performance of packing of the same reactor, will appear the temperature difference of bed layer, bring difficulty for the equilibrium operation of the whole process.

At present, the catalysts used in the market for producing fuel oil mainly comprise amorphous silica-alumina (containing no molecular sieve) catalysts, and also hydrocracking catalysts which contain a small amount of molecular sieve and have slightly higher activity. In practical situations, the above two catalysts also have disadvantages, which are mainly expressed in the following basic aspects that (1) the cracking activity is still low in the current catalyst system, and although higher middle distillate selectivity is ensured, under the conditions of a certain processing amount and the same space velocity, the required cracking reaction temperature is higher, the corresponding operation period is shorter, or the required catalyst amount is higher (the space velocity is lower), and the production cost is higher; (2) the two catalysts mainly improve the yield of diesel oil in the aspect of improving fuel oil, the demand of aviation kerosene on the market is larger at present, and the requirements of enterprises cannot be met in the aspect.

Disclosure of Invention

In order to overcome the problems of short operation period and low selectivity of aviation kerosene in the prior art, the invention provides a hydrocracking method for producing fuel oil, which realizes high-efficiency production of fuel oil and gives consideration to high yield of aviation kerosene.

A hydrocracking process for producing fuel oil comprising: in the presence of hydrogen, raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel fraction and a tail oil fraction, and part of the tail oil fraction is recycled;

the hydrocracking catalyst comprises 45-90 wt% of a carrier, 1-40 wt% of a first metal component and 1-15 wt% of a second metal component, wherein the carrier is calculated by the weight of the hydrocracking catalyst on a dry basis, and the first metal component is calculated by the weight of a metal oxide; the carrier comprises a phosphorus-containing Y-type molecular sieve and a heat-resistant inorganic oxide, wherein the weight ratio of the phosphorus-containing Y-type molecular sieve to the heat-resistant inorganic oxide is (0.03-20): 1; the first metal component is a metal selected from group VIB; the second metal component is a metal selected from group VIII; calculated by oxide, the phosphorus content of the phosphorus-containing Y-type molecular sieve is 0.3-5 wt%, the pore volume is 0.2-0.95 mL/g, and the ratio of pyridine infrared B acid to pyridine infrared L acid is 2-10.

The method provided by the invention can greatly increase the yield of the intermediate distillate oil of the product, and can also produce naphtha at the same time, and the selectivity of the aviation kerosene fraction is high. Compared with the prior art, the optimized hydrocracking catalyst has high activity and good stability, so that the hydrocracking device has high space velocity and high efficiency and can run for a long period.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The hydrocracking method for producing the fuel oil provided by the invention comprises the following steps: in the presence of hydrogen, raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel fraction and a tail oil fraction, and part of the tail oil fraction is recycled;

Optionally, the raw oil is at least one selected from the group consisting of straight run gas oil, vacuum gas oil, demetallized oil, atmospheric residue, deasphalted vacuum residue, coker distillate, catalytically cracked distillate, shale oil, tar sand oil, and coal liquefied oil.

Preferably, the reaction zone is pretreated by hydrogenationThe reaction conditions are as follows: the hydrogen partial pressure is 6.0MPa to 20.0MPa, the reaction temperature is 280 ℃ to 400 ℃, and the liquid hourly space velocity is 0.5h^-1～6h^-1The volume ratio of hydrogen to oil is 300-2000.

Preferably, the reaction conditions of the hydrocracking reaction zone are: the hydrogen partial pressure is 6.0MPa to 20.0MPa, the reaction temperature is 290 ℃ to 420 ℃, and the liquid hourly space velocity is 0.3h^-1～5h^-1The volume ratio of hydrogen to oil is 300-2000.

Preferably, a hydrogenation pretreatment reaction area is filled with a hydrogenation refining catalyst, and the hydrogenation refining catalyst is at least one catalyst selected from VIB non-noble metals or at least one catalyst selected from VIII non-noble metals or a combination thereof, which is loaded on amorphous alumina or/and silica. Further preferably, the group VIII non-noble metal is selected from nickel and/or cobalt, the group VIB non-noble metal is selected from molybdenum and/or tungsten, based on the total weight of the hydrorefining catalyst, the total content of nickel and/or cobalt in terms of oxide is 1 to 15 wt%, the total content of molybdenum and/or tungsten in terms of oxide is 5 to 40 wt%, and the balance is a carrier.

In the preferred situation, the reaction product is subjected to gas-liquid separation through a high-pressure separator, the obtained liquid phase material flow enters a low-pressure separator for further gas-liquid separation, and then the obtained liquid phase material flow enters a fractionation system for fractionation to obtain gas, light naphtha fraction (the distillation range is that the final distillation point is less than 92 ℃), heavy naphtha fraction (the distillation range is 92-150 ℃), aviation kerosene fraction (the distillation range is 150-220 ℃), diesel fraction (the distillation range is 220-375 ℃) and tail oil fraction (the distillation range is that the initial distillation point is more than 370 ℃).

In the invention, the selectivity of the middle distillate oil is calculated by the mass fraction of the fraction at 150-375 ℃ in the liquid product accounting for the fraction at less than 375 ℃.

In the invention, the selectivity of the aviation kerosene is calculated by the mass fraction of the 150-220 ℃ fraction in the liquid product in all the fractions at the temperature of less than 220 ℃.

In one preferred embodiment of the invention, a major portion of the tail oil fraction is recycled back to the process for the production of a higher amount of middle distillate. Wherein, raw oil is fresh oil, the circulating tail oil fraction is circulating oil, and the mass fraction (circulation ratio) of the circulating oil in the total feeding is at least 50%.

In one preferred embodiment of the invention, a major portion of the diesel fraction and the tail oil fraction are recycled back together to produce a high yield aviation kerosene fraction. Raw oil is used as fresh oil, the recycled diesel oil fraction and the tail oil fraction are used as recycled oil, and the mass fraction (recycle ratio) of the recycled oil in the total feed is at least 50%.

In the hydrocracking catalyst adopted by the invention, the phosphorus-containing Y-type molecular sieve as a carrier component has special performance, so that the hydrocracking catalyst has higher hydrocracking activity and ring opening selectivity, the naphthenic rings of tetrahydronaphthalene, tetrahydrophenanthrene and decahydrophenanthrene can be opened, and monocyclic naphthenic hydrocarbon is reserved, thereby reducing the density and improving the hydrogen content. Calculated by oxide, the phosphorus content of the phosphorus-containing Y-type molecular sieve is 0.3-5 wt%, the pore volume is 0.2-0.95 mL/g, and the ratio of pyridine infrared B acid to pyridine infrared L acid is 2-10.

The phosphorus-containing Y-type molecular sieve has a higher ratio of the B acid content to the L acid content. Particularly, the phosphorus-containing Y-type molecular sieve not only reserves high ratio of framework aluminum to non-framework aluminum, but also reserves certain non-framework aluminum at a position of-4 to-6 ppm or at a position of 3 to 7ppm at the position of the non-framework aluminum. Specifically, in an Al27-NMR structural spectrum of the molecular sieve, the peak height ratio of framework aluminum to non-framework aluminum of 60 +/-1 ppm and-1 +/-1 ppm, namely I60ppm/I-1ppm, can be 5-40; and the chemical shift position of 0ppm of non-framework aluminum has two obvious characteristic peaks: -1 + -1ppm, and-5.5 + -2 ppm or 3-7 ppm, the ratio of the peak heights of the two, i.e., I-1ppm/I + -6ppm, may be 0.4-2, preferably 0.8-2, wherein I + -6ppm is the greater of the peak heights of-5.5 + -2 ppm and 3-7 ppm.

Preferably, the phosphorus-containing Y-type molecular sieve is prepared by performing special hydrothermal treatment and acid washing treatment on a phosphorus-containing molecular sieve raw material. Specifically, the preparation step of the phosphorus-containing Y-type molecular sieve may include:

a. carrying out hydro-thermal treatment on a phosphorus-containing molecular sieve raw material for 0.5-10h at the temperature of 350-700 ℃ and the pressure of 0.1-2MPa in the presence of water vapor to obtain a hydro-thermally treated molecular sieve material; calculated by oxide and based on the dry weight of the phosphorus-containing molecular sieve raw material, the phosphorus content of the phosphorus-containing molecular sieve raw material is 0.1-15 wt%, and the sodium content is 0.5-4.5 wt%;

b. b, adding water into the molecular sieve material subjected to the hydrothermal treatment obtained in the step a for pulping to obtain molecular sieve slurry, heating the molecular sieve slurry to 40-95 ℃, keeping the temperature, and continuously adding an acid solution into the molecular sieve slurry, wherein the ratio of the weight of acid in the acid solution to the dry weight of the phosphorus-containing molecular sieve raw material is (0.01-0.6): 1, taking 1L of the molecular sieve slurry as a reference, taking H + as the reference, adding the acid solution at a speed of 0.05-10 mol/H, reacting at constant temperature for 0.5-20H after the acid is added, and collecting a solid product.

In the step a, the phosphorus-containing molecular sieve raw material refers to a phosphorus-containing molecular sieve. By adopting the phosphorus-containing molecular sieve as a raw material, the phosphorus-aluminum species outside the molecular sieve framework can improve the framework stability of the molecular sieve, thereby further improving the performance of the molecular sieve. The structure of the phosphorus-containing molecular sieve raw material can be an octahedral zeolite molecular sieve structure, preferably a phosphorus-containing Y-type molecular sieve, the unit cell constant of the phosphorus-containing molecular sieve raw material can be 2.425-2.47 nm, and the specific surface area of the phosphorus-containing molecular sieve raw material can be 250-750 m²The pore volume may be 0.2 to 0.95 ml/g.

In the step a, the water content of the phosphorus-containing molecular sieve raw material is preferably 10-40 wt%. The phosphorus-containing molecular sieve raw material with the water content can be obtained by adding water into the molecular sieve, pulping, filtering and drying. The phosphorus-containing molecular sieve raw material is preferably granular, and the content of the phosphorus-containing molecular sieve raw material with the granularity range of 1 mm-500 mm can be 10-100 wt%, preferably 30-100 wt% of the total weight of the phosphorus-containing molecular sieve raw material. Further, the content of the phosphorus-containing molecular sieve raw material with the granularity range of 5 mm-100 mm is 30-100 wt% of the total weight of the phosphorus-containing molecular sieve raw material. Wherein the particle size is in terms of the diameter of the circumscribed circle of particles. The adoption of the phosphorus-containing molecular sieve raw material with the granularity range for hydrothermal treatment can obviously improve the mass transfer effect of the hydrothermal treatment, reduce the material loss and improve the stability of operation. The particle size control method of the molecular sieve raw material can be conventional in the field, such as a sieving method, an extrusion strip method, a rolling ball method and the like.

Wherein, the meaning of the water adding and pulping in the step b is well known to those skilled in the art, and the ratio of the weight of the water in the molecular sieve slurry obtained after pulping to the dry weight of the phosphorus-containing molecular sieve raw material can be (14-5): 1.

in the step b, the molecular sieve slurry is preferably heated to 50-85 ℃, and then the acid solution is continuously added into the molecular sieve slurry while maintaining the temperature until the weight of the acid in the acid solution reaches a set amount. The most important of the preparation steps of the phosphorus-containing Y-type molecular sieve is that a continuous acid adding mode is adopted, acid adding and acid washing reaction are carried out simultaneously, the acid adding speed is low, the dealumination process is more moderate, and the improvement of the performance of the molecular sieve is facilitated.

Wherein, the acid solution can be continuously added into the molecular sieve slurry at one time, namely, the whole acid solution is continuously added according to a specific acid adding speed, and then the reaction is carried out at constant temperature. In particular, the acid solution may also be added in multiple portions in order to increase the utilization of the material and reduce the waste output. For example, the acid solution can be added to the molecular sieve slurry at a specific acid addition rate of 2-10 times, and after each acid addition, the reaction can be carried out at constant temperature for a period of time to continue the next acid addition until the set amount of the acid solution is added. When the acid solution is added in multiple portions, the ratio of the weight of acid in the acid solution to the dry weight of the phosphorus-containing molecular sieve starting material is preferably (0.01-0.3): 1. the acid concentration of the acid solution can be 0.01-15.0 mol/L, and the pH value can be 0.01-3. The acid may be a conventional inorganic acid and/or organic or acid, and for example, may be at least one selected from phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid, tartaric acid, formic acid and acetic acid.

Wherein, the preparation step of the phosphorus-containing Y-type molecular sieve can also comprise the following steps: in step b, adding an ammonium salt into the molecular sieve slurry during the adding of the acid solution, wherein the ammonium salt can be at least one selected from ammonium nitrate, ammonium chloride and ammonium sulfate, and the weight ratio of the ammonium salt to the dry weight of the phosphorus-containing molecular sieve raw material can be (0.1-2.0): 1. the ammonium salt may be added to the molecular sieve slurry independently of the acid solution, or an aqueous solution containing the ammonium salt and the acid may be prepared in a desired amount and added to the molecular sieve slurry.

Wherein, the preparation step of the phosphorus-containing Y-type molecular sieve can also comprise the following steps: and collecting the solid product, and then washing and drying to obtain the phosphorus-containing Y-type molecular sieve. The washing and drying are conventional steps for preparing the molecular sieve, and the disclosure is not particularly limited. For example, the drying may be performed by using an oven, a mesh belt, a converter, or the like, and the drying conditions may be: the temperature is 50-350 ℃, and preferably 70-200 ℃; the time is 1-24 h, preferably 2-6 h.

According to the invention, the heat-resistant inorganic oxide can improve the strength of the catalyst, and improve and adjust the physicochemical properties of the catalyst, such as improving the pore structure of the catalyst. The heat-resistant inorganic oxide may be an inorganic oxide commonly used for hydrogenation catalyst supports, such as alumina, silica, amorphous silica-alumina compounds, zirconia, magnesia, thoria, beryllia, boria, cadmium oxide, and the like. In a preferred embodiment of the present disclosure, the heat-resistant inorganic oxide is preferably alumina, which may include gibbsite such as gibbsite (gibbsite), bayerite nordstrandite (bayerite) and diaspore such as boehmite (boehmite, diasporite, pseudoboehmite). In other embodiments, the refractory inorganic oxide is of another species or combination.

Preferably, the first metal component is molybdenum and/or tungsten; the second metal component is at least one selected from iron, nickel and cobalt.

The hydrocracking catalyst can be prepared by a conventional method, for example, the preparation method of the hydrocracking catalyst can comprise the following steps: the impregnation liquid containing the metal precursor is contacted with the carrier for impregnation, and then the material obtained after the impregnation is dried.

The preparation method of the carrier is well known to those skilled in the art, and may include, for example: mixing the phosphorus-containing Y-type molecular sieve, the heat-resistant inorganic oxide, the solvent and the optional auxiliary agent, and then molding and drying to obtain the carrier. The molding method can adopt various conventional methods, such as tabletting molding, rolling ball molding or extrusion molding. The solvent is a common solvent in the catalyst forming process. When the extrusion molding method is employed, an appropriate amount of an auxiliary is preferably added to facilitate molding.

In an alternative embodiment, the support may be prepared as disclosed in patent CN107029779A, in particular: (1) mixing the phosphorus-containing Y-type molecular sieve with heat-resistant inorganic oxide, peptizing agent, lubricant and water to obtain a mixture, wherein the dosage of each component is such that the weight ratio of the mass of the peptizing agent to the powder in the mixture is 0.28 x 10^-4～4.8×10^-4mol/g, the ratio of the weight of water to the amount of mass of peptizing agent is 2.0X 10³～30×10³g/mol, wherein the weight of the powder is the sum of the weights of the phosphorus-containing Y-type molecular sieve and the heat-resistant inorganic oxide, and the mass of the peptizing agent refers to the mole number of the metered H protons in the peptizing agent; the lubricant is one or two of sesbania powder and graphite; (2) and (2) kneading, molding, drying and roasting the mixture obtained in the step (1) to obtain the carrier.

The metal precursors may include a first metal precursor and a second metal precursor. Wherein the first metal precursor is a soluble compound containing the first metal, and comprises at least one of an inorganic acid of the first metal, an inorganic salt of the first metal and a first metal organic compound; the inorganic salt may be at least one selected from the group consisting of nitrate, carbonate, hydroxycarbonate, hypophosphite, phosphate, sulfate and chloride; the organic substituent in the first metal organic compound is at least one selected from hydroxyl, carboxyl, amino, ketone, ether and alkyl. For example, when the first metal is molybdenum, the first metal precursor may be at least one selected from the group consisting of molybdic acid, paramolybdic acid, molybdate, paramolybdate, and the like; when the first metal component is tungsten, the first metal precursor may be at least one selected from tungstic acid, metatungstic acid, ethyl metatungstic acid, tungstate, metatungstate, and ethyl metatungstate. The second metal precursor is a soluble compound containing the second metal and comprises at least one of inorganic acid of the second metal, inorganic salt of the second metal and organic compound of the second metal; the inorganic salt may be at least one selected from the group consisting of nitrate, carbonate, hydroxycarbonate, hypophosphite, phosphate, sulfate and chloride; the organic substituent in the second metal organic compound is at least one selected from hydroxyl, carboxyl, amino, ketone, ether and alkyl.

The impregnation liquid can also contain organic additives; the concentration of the organic additive may be 2-300 g/L. The organic additive is an oxygen-containing organic compound and/or a nitrogen-containing organic compound. Specifically, the oxygen-containing organic compound may be at least one selected from the group consisting of ethylene glycol, glycerol, polyethylene glycol (molecular weight may be 200 to 1500), diethylene glycol, butanediol, acetic acid, maleic acid, oxalic acid, nitrilotriacetic acid, 1, 2-cyclohexanediaminetetraacetic acid, citric acid, tartaric acid, and malic acid; the nitrogen-containing organic compound may be at least one selected from the group consisting of ethylenediamine, diethylenetriamine, cyclohexanediaminetetraacetic acid, glycine, nitrilotriacetic acid, ethylenediaminetetraacetic acid and ammonium ethylenediaminetetraacetate.

The contacting temperature in the preparation of the hydrocracking catalyst is not particularly limited, and may be various temperatures that the impregnation solution can reach. The time for the impregnation is also not particularly limited as long as the catalyst carrier can be supported with the desired amount of the metal active component precursor. In general, the higher the impregnation temperature, the higher the concentration of the impregnation solution, and the shorter the time required to achieve the same impregnation amount (i.e., the weight difference between the catalyst support after impregnation and the catalyst support before impregnation); and vice versa. When the desired amount and conditions of impregnation are determined, one skilled in the art can readily select an appropriate impregnation time based on the teachings of the present disclosure. The present disclosure does not specifically require an impregnation method, which may be either a saturated impregnation or a supersaturated impregnation. The impregnation may be carried out under a sealed condition or in an open environment according to a conventional method in the art, and the loss of the aqueous solvent may or may not be replenished during the impregnation. Various gases, such as air, nitrogen, water vapor, etc., may be introduced during the impregnation process, or any new components may not be introduced.

In the preparation of the hydrocracking catalyst, the drying conditions are not particularly limited, and may be various drying conditions commonly used in the art, for example, may be: the temperature is 80-350 ℃, preferably 100-300 ℃ and the time is 0.5-24 hours, preferably 1-12 hours.

In the preparation of the hydrocracking catalyst, a step of drying the contacted material and then calcining the dried material, which is a conventional step for preparing the catalyst, may be further included, and the disclosure is not particularly limited. The conditions for the calcination may be, for example: the temperature is 350-600 ℃, and preferably 400-550 ℃; the time is 0.2 to 12 hours, preferably 1 to 10 hours.

The following examples further illustrate the process of the present invention, but are not intended to limit the invention thereto.

The pore volume and specific surface area of the molecular sieve were measured by a static low-temperature adsorption capacity method using an ASAP 2400 model automatic adsorption apparatus (micromeritics instruments, USA) (using the method of national Standard GB/T5816-1995).

The unit cell constant is determined by an X-ray diffractometer model D5005 of Siemens Germany, and is in accordance with the method of industry standard SH/T0339-92.

The phosphorus content and the sodium content of the molecular sieve are measured by a 3271E type X-ray fluorescence spectrometer of Japan science and Motor industry Co., Ltd, and the measuring method comprises the following steps: tabletting and forming a powder sample, carrying out rhodium target, detecting the spectral line intensity of each element by a scintillation counter and a proportional counter under the laser voltage of 50kV and the laser current of 50mA, and carrying out quantitative and semi-quantitative analysis on the element content by an external standard method.

The ratio of the B acid amount to the L acid amount of the molecular sieve is measured by a Bio-Rad IFS-3000 type infrared spectrometer. The specific method comprises the following steps: the molecular sieve sample is ground and pressed into 10mg/cm²The self-supporting sheet is placed in an in-situ cell of an infrared spectrometer at 350 ℃ and 10 DEG C^-3Surface purification treatment is carried out for 2 hours under Pa vacuum degree, pyridine saturated vapor is introduced after the temperature is reduced to room temperature, and adsorption is carried outAfter 15 minutes of equilibration, the solution is subjected to vacuum desorption at 350 ℃ for 30 minutes, and the absorption spectrum of the pyridine is measured after the solution is cooled to room temperature. The scanning range is 1400cm^-1-1700cm^-1At 1540 + -5 cm^-1The ratio of the infrared absorption of the band to the weight and area of the sample piece defines the amount of B acid [ infrared absorption per unit area, per unit mass of the sample, expressed as: AB (cm)²·g)^-1]. At 1450 + -5 cm^-1The ratio of the infrared absorption value of the band to the weight and area of the sample piece defines the L acid amount [ infrared absorption value per unit area, unit mass of the sample, expressed as: AL (cm)²·g)^-1]The value of AB/AL is defined as the ratio of the amount of B acid to the amount of L acid of the zeolite molecular sieve.

The molecular sieve adopts a Varian UNITYINOVA300M nuclear magnetic resonance instrument to perform sample analysis, wherein the resonance frequency of Al MAS is 78.162MHzs, the rotor speed is 3000Hz, the repetition delay time is 0.5s, the sampling time is 0.020s, the pulse width is 1.6 mus, the spectrum width is 54.7kHz, the data is collected at 2000 points, the cumulative frequency is 800 times, and the test temperature is room temperature.

The hydrocracking catalyst A is prepared by the following method:

taking PSRY molecular sieve (product of China petrochemical catalyst Chang Ling division, trade name PSRY, unit cell constant of 2.456nm, specific surface area of 620 m)²Per g, pore volume of 0.39ml/g, Na₂O content 2.2 wt.%, P₂O₅Content of 1.5 wt.%, Al₂O₃Content of 18 wt%) of the phosphorus-containing molecular sieve, adding deionized water, pulping, wherein the total amount of water is 1000ml, filtering, and drying at 70 ℃ for 2h to obtain the phosphorus-containing molecular sieve raw material with the water content of 35 wt%.

Crushing the phosphorus-containing molecular sieve raw material, sieving to 5-20 meshes (wherein 1-500 mm particles account for 70 wt% of the total weight of the phosphorus-containing molecular sieve raw material), placing into a hydrothermal treatment device, introducing 100% of steam, heating to 580 ℃, controlling the pressure in the device to be 0.4MPa, performing hydrothermal treatment for 2 hours constantly, and taking out the molecular sieve material after the hydrothermal treatment.

According to the weight ratio of sulfuric acid to phosphorus-containing molecular sieve raw material (dry basis) of 0.02: 1 preparing 250ml of sulfuric acid aqueous solution, wherein the concentration of sulfuric acid in the aqueous solution is 0.2 mol/L.

Taking 50g (dry basis) of the molecular sieve material subjected to the hydrothermal treatment, adding 500ml of deionized water, stirring and pulping to obtain molecular sieve slurry, and heating to 80 ℃. Based on 1L of molecular sieve slurry and H⁺Adding the prepared sulfuric acid aqueous solution into the molecular sieve slurry at a constant speed for three times at a speed of 0.5mol/h, reacting for 2 hours at a constant temperature after each time of acid addition, filtering, and taking a filter cake to continue to add acid for the next time in the same manner. After the last time of acid addition and reaction for 2 hours, collecting a solid product, and drying at 100 ℃ for 8 hours to obtain the phosphorus-containing Y-type molecular sieve Y-1, wherein the phosphorus content is 0.6 weight percent, the pore volume is 0.38ml/g, the acid content of B acid/L acid content is 4.2, I_60ppm/I_-1ppmIs 5.2, I_-1ppm/I_±6ppmIs 1.2.

583.3g of pseudo-boehmite powder PB90 (produced by Zhongpetrochemical catalyst ChangLing division, with a pore volume of 0.9ml/g and a water content of 28 wt%) and 98.8g Y-1 molecular sieve (with a water content of 19 wt%) and 18 g of sesbania powder are mixed uniformly, 580ml of aqueous solution containing 18ml of nitric acid (65-68 wt% in Beijing chemical reagent factory) is added, and extruded into trilobal strips with a circumscribed circle diameter of 1.6 mm, and the three-leaf strips are dried at 120 ℃ and calcined at 600 ℃ for 3 hours to obtain the carrier CS.

After the temperature is reduced to room temperature, 100g of CS carrier is taken and dipped in 80ml of aqueous solution containing 52 g of ammonium metatungstate (82 wt% of tungsten oxide in Sichuan tribute cemented carbide factory), 8.7 g of basic nickel carbonate (51 wt% of nickel oxide in Jiangsu Yixing brady chemical Co., Ltd.) and 10.5g of citric acid, and the carrier is baked for 10 hours at 120 ℃ to obtain the hydrocracking catalyst A, wherein the carrier comprises the following components: 84 wt% of heat-resistant oxide, 16 wt% of phosphorus-containing molecular sieve; catalyst composition, calculated as oxides: 29% by weight of tungsten, 3% by weight of nickel and 68% by weight of support.

The hydrocracking catalyst B is prepared by the following method:

the preparation method of the phosphorus-containing molecular sieve of the comparative example can refer to the preparation method of the phosphorus-containing zeolite disclosed in CN1088407C, which comprises directly mixing a phosphorus-containing compound and a raw material zeolite in a weight ratio of 0.1-40, heating at 50-550 ℃ for at least 0.1 hour under a closed condition, washing the obtained product with deionized water until no acid radical ions exist, and obtaining the phosphorus-containing molecular sieve named as Y-2, wherein the phosphorus content is 2.3 wt%, the pore volume is 0.37ml/g, the amount of B acid/L acid is 3.2, I60ppm/I-1ppm is 5.5, and I-1ppm/I ± 6ppm is 2.7.

A catalyst was prepared according to the method of example 1, except that the molecular sieve used was Y-2, yielding hydrocracking catalyst B having a support composition of: 84 wt% of heat-resistant oxide, 16 wt% of phosphorus-containing molecular sieve; catalyst composition, calculated as oxides: 29% by weight of tungsten, 3% by weight of nickel and 68% by weight of support.

The hydrocracking catalyst C has a commercial designation of RT-5. The product of the hydrofining catalyst is RN-32V, and is produced by China petrochemical catalyst division.

The VGO properties of the feedstock oils used in the examples and comparative examples are shown in Table 1.

Example 1

Raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst A for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel oil fraction and a tail oil fraction, most of the tail oil fraction is circulated to a raw material buffer tank for circular recycling, and the circulation ratio is 50%. The reaction conditions, product distribution and key product properties are listed in tables 2 and 3.

As shown in tables 2 and 3, after the reaction of the VGO in the middle east by adopting the method in the embodiment 1, the tail oil can be basically and completely converted at the cracking temperature of 375 ℃, the yield of the aviation kerosene fraction and the diesel oil fraction reaches 24.54 percent and 53.56 percent, the selectivity of the middle distillate oil reaches 81.59 percent, the smoke point of the aviation kerosene is 29mm, the freezing point is less than < -50 ℃, the key properties meet the requirements of 3# jet fuel, the cetane index of the diesel oil fraction is as high as 67, and the sulfur mass fraction is less than 5mg/kg, so that the VGO can be used as a high-quality national VI diesel oil blending component.

Comparative example 1

Raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst B for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel oil fraction and a tail oil fraction, most of the tail oil fraction is circulated to a raw material buffer tank for circular refining, and the circulation ratio is 50%. The reaction conditions, product distribution and key product properties are listed in tables 2 and 3.

As shown in tables 2 and 3, after the feedstock oil was reacted by the method of comparative example 1, the yield and selectivity of middle distillate oil were similar to those of example 1 under 50% cycle conversion of tail oil, but higher hydrocracking reaction temperature (about 10 ℃ higher reaction temperature) was required. Although the product quality is satisfactory, higher reaction temperatures can affect the operating cycle of the plant.

Comparative example 2

As shown in tables 2 and 3, after the feedstock oil is reacted by the method of comparative example 2, the yield and selectivity of middle distillate oil are similar to those of example 1 under the condition of 50% tail oil recycle conversion, but lower space velocity of hydrocracking reaction is required (compared with example 1, the space velocity is 1.5h^-1Reduced to 1.1h^-1). Although the product quality meets the requirement, the lower volume space velocity affects the processing load of the device and the economic benefit is poor.

Comparative example 3

Raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst C for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel oil fraction and a tail oil fraction, most of the tail oil fraction is circulated to a raw material buffer tank for circular refining, and the circulation ratio is 50%. The reaction conditions, product distribution and key product properties are listed in tables 2 and 3.

As shown in tables 2 and 3, the feedstock oil was reacted by the method of comparative example 3, although the reaction temperature and the volume space velocity were comparable to those of example 1, the yield of middle distillate oil and the selectivity were much lower than those of example under the condition of the essential conversion of tail oil, and the yield was about four percentage points lower.

The results show that the method provided by the invention can obtain high-yield aviation kerosene fraction and diesel oil fraction at a lower reaction temperature or a higher space velocity under the condition of equivalent circulating tail oil amount, and the product quality is also better.

Example 2

Raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst A for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel oil fraction and a tail oil fraction, and most of the diesel oil fraction and the tail oil fraction are circulated to a raw material buffer tank for circular remill with the circulation ratio of 50%. The reaction conditions, product distribution and key product properties are listed in tables 4 and 5.

As shown in tables 4 and 5, after the VGO in the middle east is reacted by the method in the example 2, the basically full conversion can be realized at the hydrocracking temperature of 380 ℃, wherein the yield of the aviation kerosene fraction reaches 58.98%, the selectivity of the aviation kerosene fraction reaches 61.39%, the smoke point of the aviation kerosene is 28mm, the freezing point is less than < -50 ℃, and the key properties meet the requirements of 3# jet fuel.

Comparative example 4

Raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst B for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel oil fraction and a tail oil fraction, and most of the diesel oil fraction and the tail oil fraction are circulated to a raw material buffer tank for circular recycling, wherein the circulation ratio is 50%. The reaction conditions, product distribution and key product properties are listed in tables 4 and 5.

As shown in tables 4 and 5, the middle east VGO reacted using the method of comparative example 4, which showed a similar selectivity to aviation kerosene as in example 2, but required a higher hydrocracking reaction temperature (about 10 ℃ higher reaction temperature). Although the product quality is satisfactory, the higher reaction temperature affects the operation cycle of the apparatus.

Comparative example 5

As shown in tables 4 and 5, the yield and selectivity of aviation kerosene are similar to those of example 2, but lower space velocity of hydrocracking reaction is required (compared with example 2, space velocity is 1.5 h)^-1Reduced to 1.1h^-1). Although the product quality meets the requirement, the lower volume space velocity affects the processing load of the device and the economic benefit is poor.

Comparative example 6

Raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst C for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel oil fraction and a tail oil fraction, and most of the diesel oil fraction and the tail oil fraction are circulated to a raw material buffer tank for circular recycling, wherein the circulation ratio is 50%. The reaction conditions, product distribution and key product properties are listed in tables 4 and 5.

As shown in tables 4 and 5, although the reaction temperature and the volume space velocity of the VGO in the middle east were equivalent to those of example 2, the yield and selectivity of the aviation kerosene fraction were much lower than those of example 2 under the condition that the diesel oil fraction and the tail oil fraction were substantially converted, and the yield was about four percentage points lower, after the reaction of the VGO in the middle east using the method of comparative example 6.

The results show that the method provided by the invention can obtain high-yield aviation kerosene fraction at lower reaction temperature or higher airspeed and under the condition of equivalent amounts of circulating diesel oil and tail oil, and the product quality is also better.

TABLE 1 Properties of the raw materials

Item	Middle east VGO
		Density (20 ℃ C.)/(g/cm)³)	0.9058
Sulfur mass fraction/%	2.47
		Mass fraction of nitrogen/(μ g/g)	753
Distillation range (D-1160)/. deg.C
		Initial boiling point	207
10％	346
		30％	399
50％	425
		70％	443
90％	477
		95％	497

TABLE 2 Process conditions and product distribution

Description of the drawings: the volume space velocity is the volume space velocity of fresh feeding

Table 3 key product properties primary product properties

	Example 1	Comparative example 1	Comparative example 2	Comparative example 3
					Heavy naphtha fraction (93-150 ℃ C.)
Density at 20 deg.C/(g/mL)	0.753	0.752	0.756	0.751
					Sulfur mass fraction/(mg/kg)	<0.5	<0.5	<0.5	<0.5
Mass fraction of nitrogen/(mg/kg)	<0.5	<0.5	<0.5	<0.5
					Potential content of aromatic hydrocarbons/%)	>50	>50	>50	>50
Aviation kerosene fraction (150-
					Density at 20 deg.C/(g/mL)	0.795	0.798	0.799	0.793
Freezing point/. degree.C	<-50	<-50	<-50	<-50
					Smoke point/mm	29	28.7	28.5	29.2
Diesel oil fraction (220-375 deg.C)
					Density at 20 deg.C/(g/mL)	0.828	0.829	0.83	0.827
Freezing point/. degree.C	-20	-19	-18	-20
					Sulfur mass fraction/(mg/kg)	2	1	3	2
Cetane index	67	65	66	68

TABLE 4 Process conditions and product distribution

TABLE 5 Key product Properties Primary product Properties

Claims

1. A hydrocracking process for producing fuel oil comprising: in the presence of hydrogen, raw oil sequentially passes through a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone to respectively contact with a hydrofining catalyst and a hydrocracking catalyst for reaction, the obtained reaction effluent is subjected to gas-liquid separation and fractionation to obtain a light naphtha fraction, a heavy naphtha fraction, a aviation kerosene fraction, a diesel fraction and a tail oil fraction, and part of the tail oil fraction is recycled;

the hydrocracking catalyst comprises 45-90 wt% of a carrier, 1-40 wt% of a first metal component and 1-15 wt% of a second metal component, wherein the carrier is calculated by the weight of the hydrocracking catalyst on a dry basis, and the first metal component is calculated by the weight of a metal oxide; the carrier comprises a phosphorus-containing Y-type molecular sieve and a heat-resistant inorganic oxide, wherein the weight ratio of the phosphorus-containing Y-type molecular sieve to the heat-resistant inorganic oxide is (0.03-20): 1; the first metal component is a metal selected from group VIB; the second metal component is a metal selected from group VIII; calculated by oxide, the phosphorus content of the phosphorus-containing Y-type molecular sieve is 0.3-5 wt%, the pore volume is 0.2-0.95 mL/g, and the ratio of pyridine infrared B acid to L acid is 2-10; the preparation method of the phosphorus-containing Y-type molecular sieve comprises the following steps:

2. The method of claim 1, wherein in the step a, the phosphorus-containing molecular sieve raw material is a phosphorus-containing Y-type molecular sieve, the unit cell constant of the phosphorus-containing Y-type molecular sieve is 2.425-2.47 nm, and the specific surface area is 250-750 m²The pore volume is 0.2-0.95 ml/g;

the water content of the phosphorus-containing molecular sieve raw material is 10-40 wt%.

3. The method of claim 1, wherein the phosphorus-containing molecular sieve feedstock is in the form of particles, and the content of the phosphorus-containing molecular sieve feedstock having a particle size ranging from 1mm to 500mm is 10 to 100 wt% of the total weight of the phosphorus-containing molecular sieve feedstock, the particle size being based on the diameter of the circumscribed circle of the particles.

4. The method of claim 1, wherein in the step b, the ratio of the weight of water in the molecular sieve slurry obtained after beating to the dry weight of the phosphorus-containing molecular sieve raw material is (14-5): 1.

5. the method according to claim 1, wherein in the step b, the acid solution has an acid concentration of 0.01 to 15.0mol/L, and the acid is at least one selected from phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid, tartaric acid, formic acid and acetic acid.

6. The method according to claim 1, wherein the heat-resistant inorganic oxide is at least one selected from the group consisting of alumina, zirconia, magnesia, thoria, beryllia, boria, and cadmium oxide; the first metal component is molybdenum and/or tungsten; the second metal component is at least one selected from iron, nickel and cobalt.

7. The method of claim 1, wherein the reaction conditions in the hydrotreating pretreatment reaction zone are: the hydrogen partial pressure is 6.0MPa to 20.0MPa, the reaction temperature is 280 ℃ to 400 ℃, and the liquid hourly space velocity is 0.5h^-1～6h^-1The volume ratio of hydrogen to oil is 300-2000.

8. The process of claim 1, wherein the reaction conditions in the hydrocracking reaction zone are: the hydrogen partial pressure is 6.0MPa to 20.0MPa, the reaction temperature is 290 ℃ to 420 ℃, and the liquid hourly space velocity is 0.3h^-1～5h^-1The volume ratio of hydrogen to oil is 300-2000.

9. The process of claim 1 wherein a hydrotreating catalyst is loaded in the hydrotreating reaction zone, said hydrotreating catalyst being at least one non-noble group VIB metal, or at least one non-noble group VIII metal, or a combination thereof, supported on amorphous alumina or/and silica.

10. The process of claim 9, wherein the group VIII non-noble metal is selected from nickel and/or cobalt, the group VIB non-noble metal is selected from molybdenum and/or tungsten, the total content of nickel and/or cobalt in terms of oxides is 1 to 15 wt%, the total content of molybdenum and/or tungsten in terms of oxides is 5 to 40 wt%, and the balance is a support, based on the total weight of the hydrofinishing catalyst.

11. The process of claim 1, wherein the raw oil is fresh oil, the recycled tail oil fraction is recycled oil, and the mass fraction of the recycled oil in the total feed is at least 50%.

12. The process according to claim 1, wherein the raw oil is fresh oil, the recycled diesel fraction and the tail oil fraction are recycled oil, and the mass fraction of the recycled oil in the total feed is at least 50%.