阅读说明：本技术 一种催化裂化柴油生产btx馏分的方法 (Method for producing BTX fraction by catalytically cracking diesel oil ) 是由 严张艳 任亮 胡志海 吴昊 张毓莹 许双辰 杨平 于 2018-05-31 设计创作，主要内容包括：一种催化裂化柴油生产BTX馏分的方法,将催化裂化柴油切割为轻催化裂化柴油馏分和重催化裂化柴油馏分,轻催化裂化柴油馏分进入低压加氢裂化单元进行反应,重催化裂化柴油馏分进入加氢处理单元后,所得液相物流进入催化裂化单元,与催化裂化催化剂接触进行反应,其反应生成物进入分馏系统,分馏后得到干气、液化气、富含BTX馏分、柴油馏分。本发明根据催化裂化柴油原料硫氮杂质多,芳烃含量高的特点,采用组合工艺的技术方案来生产富含BTX馏分,从而降低柴汽比,并且以BTX馏分以填补我国轻质芳烃的市场缺口。(A method for producing BTX fraction by catalytic cracking diesel oil comprises the steps of cutting the catalytic cracking diesel oil into light catalytic cracking diesel oil fraction and heavy catalytic cracking diesel oil fraction, enabling the light catalytic cracking diesel oil fraction to enter a low-pressure hydrocracking unit for reaction, enabling the heavy catalytic cracking diesel oil fraction to enter a hydrotreating unit, enabling obtained liquid phase material flow to enter the catalytic cracking unit, enabling the obtained liquid phase material flow to contact with a catalytic cracking catalyst for reaction, enabling reaction products to enter a fractionation system, and fractionating to obtain dry gas, liquefied gas, BTX-enriched fraction and diesel oil fraction. According to the characteristics of more sulfur and nitrogen impurities and high aromatic hydrocarbon content of the catalytic cracking diesel oil raw material, the BTX-rich fraction is produced by adopting the technical scheme of a combined process, so that the diesel-gasoline ratio is reduced, and the BTX fraction is used for filling the market gap of light aromatic hydrocarbons in China.)

1. A process for catalytically cracking diesel to produce a BTX fraction comprising:

(1) The catalytic cracking diesel oil is cut into light catalytic cracking diesel oil fraction and heavy catalytic cracking diesel oil fraction, the cutting point is between 260 and 340 ℃,

(2) The light catalytic cracking diesel oil fraction obtained in the step (1) enters a low-pressure hydrocracking unit, and is sequentially contacted with a hydrofining catalyst and a hydrocracking catalyst for reaction in the presence of hydrogen, the reaction effluent is separated to obtain hydrogen-rich gas, and then enters a fractionation system to obtain a BTX-rich fraction, wherein the hydrogen partial pressure in the low-pressure hydrocracking unit is 2.5 MPa-7.0 MPa,

(3) The heavy catalytic cracking diesel oil fraction obtained in the step (1) enters a hydrotreating unit, and contacts with a hydrotreating catalyst to react in the presence of hydrogen, and the reaction effluent is separated to obtain a gas phase material flow and a liquid phase material flow, wherein the hydrogen partial pressure in the hydrotreating unit is 4.0 MPa-22.0 MPa,

(4) And (4) allowing the liquid phase material flow obtained in the step (3) to enter a catalytic cracking unit, contacting with a catalytic cracking catalyst for reaction, allowing a reaction product to enter a fractionation unit, and fractionating to obtain dry gas, liquefied gas, a fraction rich in BTX and a diesel fraction.

2. The method according to claim 1, wherein the light catalytic cracking diesel fraction obtained in the step (1) has a composition in which the sum of the contents of monocyclic aromatic hydrocarbons and bicyclic aromatic hydrocarbons is 70% or more and the content of tricyclic aromatic hydrocarbons is less than 5% based on the weight of the light catalytic cracking diesel fraction; the weight of the nitrogen-containing compounds in the light catalytic cracking diesel oil fraction is lower than 50 percent based on the total weight of the nitrogen-containing compounds in the catalytic cracking diesel oil.

3. the process according to claim 2, wherein the nitrogen content of the light cat cracked diesel fraction obtained in step (1) is less than 500 μ g/g.

4. The method according to claim 1, wherein the heavy catalytic cracking diesel fraction obtained in the step (1) has a composition in which the sum of the contents of bicyclic aromatics and tricyclic aromatics is 70% or more and the content of monocyclic aromatics is less than 10% based on the weight of the heavy catalytic cracking diesel fraction; the weight of the nitrogen-containing compounds in the heavy catalytic cracking diesel oil fraction is not less than 50 percent based on the total weight of the nitrogen-containing compounds in the catalytic cracking diesel oil.

5. The process according to claim 4, wherein the nitrogen content of the heavy catalytically cracked diesel fraction obtained in step (1) is not less than 1000. mu.g/g.

6. The process of claim 4 wherein the heavy catalytically cracked diesel fraction from step (1) has a composition which has a tricyclic aromatic content of less than 25% by weight of the heavy catalytically cracked diesel fraction.

7. The method of claim 1, wherein the upper limit value of the range of the cutting points in step (1) is T,X₁The weight of carbazole nitride in the catalytic cracking diesel oil accounts for the total weight of nitrogen-containing compounds, X₂The polycyclic aromatic hydrocarbon is the sum of aromatic hydrocarbons above a double ring in the mass fraction of the polycyclic aromatic hydrocarbon in the catalytic cracking diesel oil.

8. The method of claim 7, wherein X is₁The value range of (A) is 0-85%, and the X is₂The value range of (A) is 35-70%.

9. The process according to claim 1, wherein the catalytically cracked diesel fuel has an initial boiling point of 100 ℃ or higher, preferably 150 ℃ or lower, and an end point of 450 ℃ or lower.

10. The method of claim 1, wherein step (2) and step (4) share a single fractionation system.

11. The process according to claim 1 or 10, wherein the BTX-rich fraction obtained in step (2) and step (4) has a distillation range of 50 to 205 ℃.

12. The process of claim 1, wherein the low pressure hydrocracking unit comprises a hydrofinishing reaction zone and a hydrocracking reaction zone, and the reaction conditions of the hydrofinishing reaction zone are as follows: the hydrogen partial pressure is 2.5MPa to 7.0MPa, the reaction temperature is 200 ℃ to 420 ℃, and the volume ratio of hydrogen to oil is 300Nm to 1500Nm³/m³The volume airspeed is 0.5-6.0 h^-1；

The reaction conditions of the hydrocracking reaction zone are as follows: the hydrogen partial pressure is 2.5MPa to 7.0MPa, the reaction temperature is 260 ℃ to 450 ℃, and the volume ratio of hydrogen to oil is 600 Nm to 2000Nm³/m³The volume airspeed is 0.5-3.0 h^-1。

13. The process of claim 12, wherein the reaction conditions in the hydrofinishing reaction zone are: the hydrogen partial pressure is 4.0-6.0 MPa, the reaction temperature is 280-390 ℃, and the volume ratio of hydrogen to oil is 400-1300 Nm³/m³The volume airspeed is 1.0-6.0 h^-1；

The reaction conditions of the hydrocracking reaction zone are as follows: the hydrogen partial pressure is 4.0-6.0 MPa, the reaction temperature is 350-450 ℃, and the volume ratio of hydrogen to oil is 800-1800 Nm³/m³The volume airspeed is 0.5-2.0 h^-1。

14. The process of claim 1, wherein the reaction conditions of the hydroprocessing unit are: the hydrogen partial pressure is 4.0-22.0 MPa, the reaction temperature is 330-460 ℃, and the volume ratio of hydrogen to oil is 300-2000 Nm³/m³The volume airspeed is 0.1-10.0 h^-1。

15. the process of claim 14, wherein the reaction conditions of the hydroprocessing unit are: the hydrogen partial pressure is 7.0MPa to 15MPa0MPa, the reaction temperature is 350-400 ℃, and the volume ratio of hydrogen to oil is 500-1400 Nm³/m³The volume airspeed is 1.0-6.0 h^-1。

16. The process of claim 1, wherein the reaction conditions of the catalytic cracking unit are: the reaction temperature is 400-550 ℃, the agent-oil ratio is 4-20, the oil-gas residence time is 1-6 seconds, the pressure is 0.15-0.4 MPa, and the weight ratio of the water vapor to the raw materials is 0.01-0.5, preferably 0.02-0.2.

Technical Field

The invention relates to a method for producing BTX fraction by catalytic cracking diesel oil.

Background

As crude oil is increasingly degraded, more and more heavy vacuum gas oil components and even residues become the feedstock of a Fluid Catalytic Cracking (FCC) unit, resulting in an increasing degree of feedstock conversion. Catalytic cracking diesel (LCO) fractionated from an FCC unit has the characteristics of high content of sulfur and nitrogen impurities and high content of aromatic hydrocarbon, the requirement of clean fuel is difficult to achieve through the traditional hydrofining and hydro-upgrading processes, the aromatic hydrocarbon component rich in the LCO cannot be effectively utilized, and the LCO is more and more important to be processed by finding a new path.

On the other hand, the production of BTX (benzene, toluene and xylene) at home and abroad mainly adopts a catalytic reforming process and a steam cracking ethylene preparation process which take naphtha as a raw material, and because the naphtha raw material is in short supply, the light aromatic hydrocarbon in China has a larger market gap, high external dependence and wide market prospect. Therefore, how to effectively utilize LCO to produce BTX is a technical problem to be solved at present.

CN103214332B discloses a method for producing light aromatic hydrocarbons and high-quality oil products from catalytic cracking diesel oil. Extracting catalytic cracking diesel oil with an extraction solvent to obtain extract oil rich in polycyclic aromatic hydrocarbon and raffinate oil rich in alkane, and carrying out hydrofining and hydrocracking on the extract oil under the condition of hydrogenation reaction to produce light aromatic hydrocarbon and high-octane gasoline fractions.

CN104560166B discloses a catalytic conversion method for producing high octane gasoline from petroleum hydrocarbon. Cutting the catalytic cracking diesel into light and heavy components, wherein the cutting temperature is 250-260 ℃, the light components enter the lower layer of the catalytic cracking auxiliary lifting pipe, and the heavy components are subjected to hydrotreating and then enter the upper layer of the catalytic cracking auxiliary lifting pipe. And carrying out subsequent separation on the light and heavy components after catalytic cracking to obtain the high-octane gasoline.

CN104560164A discloses a hydro-upgrading process for producing high octane gasoline components or BTX fractions as products. The inferior diesel oil fraction is used as raw material, mainly providing a method for combined loading of hydrogenation modified catalyst, producing high-octane gasoline through hydrogenation refining and hydrogenation modification processes, wherein the BTX content in the high-octane gasoline fraction can reach 40 mass percent, but the inferior diesel oil is used as raw material to directly carry out hydrogenation refining, so that the aromatics hydrogenation saturation depth and denitrification intensity are difficult to reach better balance, and the inferior diesel oil can be converted into high-octane gasoline or BTX only by demanding operation conditions, thus leading to more aromatics loss.

When LCO is processed to produce BTX by the prior art, the yield of BTX is often lower, the selectivity is poor, and the problems of harsh reaction conditions, easy poisoning and inactivation of a hydrocracking catalyst, short service life of the catalyst and the like are faced.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for producing BTX fraction by catalytic cracking diesel oil, so as to solve the technical problem of poor BTX selectivity in the process of processing LCO to produce BTX and effectively reduce the possibility of poisoning and inactivation of a hydrocracking catalyst.

the method provided by the invention comprises the following steps:

(1) The catalytic cracking diesel oil is cut into light catalytic cracking diesel oil fraction and heavy catalytic cracking diesel oil fraction, the cutting point is between 260 and 340 ℃,

(2) The light catalytic cracking diesel oil fraction obtained in the step (1) enters a low-pressure hydrocracking unit, and is sequentially contacted with a hydrofining catalyst and a hydrocracking catalyst for reaction in the presence of hydrogen, the reaction effluent is separated to obtain hydrogen-rich gas, and then enters a fractionation system to obtain a BTX-rich fraction, wherein the hydrogen partial pressure in the low-pressure hydrocracking unit is 2.5 MPa-7.0 MPa,

(3) The heavy catalytic cracking diesel oil fraction obtained in the step (1) enters a hydrotreating unit, and contacts with a hydrotreating catalyst to react in the presence of hydrogen, and the reaction effluent is separated to obtain a gas phase material flow and a liquid phase material flow, wherein the hydrogen partial pressure in the hydrotreating unit is 4.0 MPa-22.0 MPa,

(4) And (4) allowing the liquid phase material flow obtained in the step (3) to enter a catalytic cracking unit, contacting with a catalytic cracking catalyst for reaction, allowing a reaction product to enter a fractionation system, and fractionating to obtain dry gas, liquefied gas, a fraction rich in BTX and a diesel fraction.

In the invention, in the preferable composition of the light catalytic cracking diesel fraction obtained in the step (1), the sum of the contents of monocyclic aromatic hydrocarbon and bicyclic aromatic hydrocarbon is more than or equal to 70 percent and the content of tricyclic aromatic hydrocarbon is less than 5 percent by taking the weight of the light catalytic cracking diesel fraction as a reference; the weight of the nitrogen-containing compounds in the light catalytic cracking diesel oil fraction is lower than 50 percent based on the total weight of the nitrogen-containing compounds in the catalytic cracking diesel oil. Further preferably, the nitrogen content of the light catalytic cracking diesel oil fraction is less than 500 [ mu ] g/g.

In the invention, in the preferable composition of the heavy catalytic cracking diesel fraction obtained in the step (1), the sum of the contents of bicyclic aromatics and tricyclic aromatics is more than or equal to 70 percent and the content of monocyclic aromatics is less than 10 percent on the basis of the weight of the heavy catalytic cracking diesel fraction; further preferably, the tricyclic aromatic content is less than 25%. The weight of the nitrogen-containing compounds in the heavy catalytic cracking diesel oil fraction is not less than 50 percent based on the total weight of the nitrogen-containing compounds in the catalytic cracking diesel oil. Further preferably, the nitrogen content of the heavy catalytic cracking diesel oil fraction is not lower than 1000 mu g/g.

In the present invention, the upper limit value of the cutting point range in step (1) is T, and preferably T can be obtained by using the following relation: T65X 1²+356X₂+86 wherein X₁The weight of carbazole nitride in the catalytic cracking diesel oil accounts for the total weight of nitrogen-containing compounds, X₂The polycyclic aromatic hydrocarbon is the sum of aromatic hydrocarbons above a double ring in the mass fraction of the polycyclic aromatic hydrocarbon in the catalytic cracking diesel oil. Further preferably, X is₁The value range of (A) is 0-85%, and the X is₂the value range of (A) is 35-70%.

In the invention, the initial boiling point of the catalytic cracking diesel oil is more than or equal to 100 ℃, preferably 150 ℃, and the final boiling point is less than 450 ℃. According to the conventional physicochemical properties of the catalytic cracking diesel oil, the upper limit value of the range of the cutting point is determined according to the relational expression, the actual cutting point is less than or equal to the upper limit value, the catalytic cracking diesel oil raw material is cut into light and heavy components, the obtained light catalytic cracking diesel oil fraction enters a low-pressure hydrocracking unit, and the obtained heavy catalytic cracking diesel oil fraction enters a hydrotreating unit and a catalytic cracking unit.

In the low-pressure hydrocracking unit, the light catalytic cracking diesel fraction is sequentially contacted with a hydrofining catalyst and a hydrocracking catalyst in the presence of hydrogen to react, and the reaction effluent is separated to obtain hydrogen-rich gas and then enters a fractionation system to obtain a BTX-rich fraction. The nitrogen-containing compound and the sulfur-containing compound of the light catalytic cracking diesel oil fraction are easier to carry out C-N, C-S bond breaking reaction, so that the hydrofining product can ensure that the nitrogen content is not more than 20 mu g/g at a higher space velocity, thereby effectively reducing the possibility of poisoning and inactivation of the hydrocracking catalyst. In addition, the research of the inventor of the invention finds that the hydrogenation saturation depth of polycyclic aromatic hydrocarbons in the light catalytic diesel oil fraction is relatively easier to control when the polycyclic aromatic hydrocarbons are converted into monocyclic aromatic hydrocarbons. Can convert the aromatic hydrocarbon of double ring and above double ring into monocyclic aromatic hydrocarbon as much as possible, but not to form cyclic alkane through over saturation. In the low-pressure hydrocracking unit, the total aromatic hydrocarbon loss is less than 5-10 mass%. In addition, in the hydrocracking process, unsaturated bicyclic aromatic hydrocarbons in the light catalytic cracking diesel oil fraction can be further saturated, and meanwhile, ring-opening and side chain breaking reactions of monocyclic aromatic hydrocarbons such as indane, tetrahydronaphthalene and alkylbenzene occur on a hydrocracking catalyst, so that most of the monocyclic aromatic hydrocarbons are converted into BTX components, and the purposes of improving BTX selectivity and yield are achieved.

Preferably, the low-pressure hydrocracking unit comprises a hydrofining reaction zone and a hydrocracking reaction zone, and the reaction conditions of the hydrofining reaction zone are as follows: the hydrogen partial pressure is 2.5MPa to 7.0MPa, the reaction temperature is 200 ℃ to 420 ℃, and the volume ratio of hydrogen to oil is 300Nm to 1500Nm³/m³The volume airspeed is 0.5-6.0 h^-1(ii) a The reaction conditions of the hydrocracking reaction zone are as follows: the hydrogen partial pressure is 2.5MPa to 7.0MPa, the reaction temperature is 260 ℃ to 450 ℃, and the volume ratio of hydrogen to oil is 600 Nm to 2000Nm³/m³The volume airspeed is 0.5-3.0 h^-1。

further preferably, the reaction conditions of the hydrofining reaction zone are as follows: the hydrogen partial pressure is 4.0-6.0 MPa, the reaction temperature is 280-390 ℃, and the volume ratio of hydrogen to oil is 400-1300 Nm³/m³The volume airspeed is 1.0-6.0 h^-1(ii) a The reaction conditions of the hydrocracking reaction zone are as follows: the hydrogen partial pressure is 4.0-6.0 MPa, the reaction temperature is 350-450 ℃, and the volume ratio of hydrogen to oil is 800-1800 Nm³/m³The volume airspeed is 0.5-2.0 h^-1。

The hydrofining catalyst is a conventional hydrofining catalyst, can be a commercially available hydrofining catalyst, and can also be a hydrofining catalyst prepared in a laboratory.

Preferably, the hydrofining catalyst comprises a carrier and an active metal element loaded on the carrier, wherein the carrier is selected from at least one of alumina, alumina-silica and titanium oxide, and the active metal element is selected from at least one of nickel, cobalt, molybdenum and tungsten; more preferably, in the hydrorefining catalyst, the content of nickel and/or cobalt in terms of oxide is 1 to 30 wt%, and the content of molybdenum and/or tungsten in terms of oxide is 5 to 35 wt%, based on the total weight of the hydrorefining catalyst.

The hydrocracking catalyst is a conventional hydrocracking catalyst, can be a commercial hydrocracking catalyst, and can also be a laboratory-prepared hydrocracking catalyst.

Preferably, the hydrocracking catalyst comprises a carrier and an active metal element loaded on the carrier, wherein the carrier comprises a molecular sieve and at least one of alumina, alumina-silica and titania, and the active metal element is at least one of nickel, cobalt, molybdenum and tungsten; more preferably, in the hydrocracking catalyst, the content of the molecular sieve is 3-40 wt%, the content of nickel and/or cobalt calculated by oxide is 1-30%, and the content of molybdenum and/or tungsten calculated by oxide is 5-40 wt% based on the total weight of the hydrocracking catalyst.

In the low-pressure hydrocracking unit, the hydrofining reaction and the hydrocracking reaction are conventional processes. The low-pressure hydrocracking unit has low hydrogen partial pressure and mild other reaction conditions, can react at a low reaction temperature, hydrogen partial pressure and hydrogen-oil ratio and a high volume airspeed, greatly reduces the operation cost and improves the production efficiency.

In the invention, the obtained heavy catalytic cracking diesel fraction enters a hydrotreating unit, and is in contact with a hydrotreating catalyst to react in the presence of hydrogen, so as to carry out hydrodesulfurization, hydrodenitrogenation and polycyclic aromatic hydrocarbon saturation reactions, and the reaction effluent is separated to obtain a gas-phase material flow and a liquid-phase material flow. In the hydrotreating unit, the polycyclic aromatic hydrocarbon in the heavy catalytic cracking diesel oil fraction is saturated as much as possible into monocyclic aromatic hydrocarbon, and then the component rich in BTX can be obtained through the subsequent catalytic cracking reaction. Thereby further achieving the purpose of improving the selectivity and yield of BTX.

Preferably, the reaction conditions of the hydroprocessing unit are: the hydrogen partial pressure is 4.0-22.0 MPa, the reaction temperature is 330-460 ℃, and the volume ratio of hydrogen to oil is 300-2000 Nm³/m³the volume airspeed is 0.1-10.0 h^-1. Further preferably: the hydrogen partial pressure is 7.0-15.0 MPa, the reaction temperature is 350-400 ℃, and the volume ratio of hydrogen to oil is 500-1400 Nm³/m³The volume airspeed is 1.0-6.0 h^-1。

The hydrotreating catalyst is a conventional hydrotreating catalyst, can be a commercially available hydrotreating catalyst, and can also be a hydrotreating catalyst prepared in a laboratory.

Preferably, the hydrotreating catalyst comprises a carrier and an active metal element loaded on the carrier, wherein the carrier is selected from alumina and/or alumina-silica, and the active metal element is selected from at least one of nickel, cobalt, molybdenum and tungsten; more preferably, in the hydrotreating catalyst, the content of nickel and/or cobalt in terms of oxide is 1 to 28 wt%, and the content of molybdenum and/or tungsten in terms of oxide is 3 to 38 wt%, based on the total weight of the hydrotreating catalyst.

In the invention, the liquid phase material flow obtained by the hydrotreating unit enters a catalytic cracking unit to contact with a catalytic cracking catalyst for reaction, and the reaction product enters a fractionation system to obtain dry gas, liquefied gas, BTX-rich fraction and catalytic cracking diesel after fractionation.

Preferably, the reaction conditions of the catalytic cracking unit are: the reaction temperature is 400-550 ℃, the agent-oil ratio is 4-20, the oil-gas residence time is 1-6 seconds, the pressure is 0.15-0.4 MPa (absolute pressure), and the weight ratio of the water vapor to the raw materials is 0.01-0.5, preferably 0.02-0.2.

The catalytic cracking catalyst is a conventional catalytic cracking catalyst, can be a commercial catalytic cracking catalyst, and can also be a catalytic cracking catalyst prepared in a laboratory.

In one embodiment of the present invention, step (2) and step (4) share a single fractionation system.

Preferably, the distillation range of the BTX-rich fraction obtained in the step (2) and the step (4) is 50-205 ℃. The sulfur content of the BTX-rich fraction obtained by the invention is less than 3 mu g/g, and the BTX component with lower impurity content can be obtained after aromatic extraction. In addition, the BTX-rich fraction can also be used as a high octane gasoline component.

In one preferred embodiment of the invention, the diesel fraction obtained by the fractionation system in step (4) is mixed with a catalytic cracking diesel feedstock, and the mixed feedstock is cut into a light catalytic cracking diesel fraction and a heavy catalytic cracking diesel fraction.

In one preferred embodiment of the present invention, the fractionation system in step (4) cuts the diesel fraction into light catalytic cracking diesel fraction and heavy catalytic cracking diesel fraction according to the properties of the diesel fraction.

the invention has the advantages that:

(1) according to the characteristics of more sulfur and nitrogen impurities and high aromatic hydrocarbon content of the catalytic cracking diesel oil raw material, the BTX-rich fraction is produced by adopting the technical scheme of a combined process, so that the diesel-gasoline ratio is reduced, and the BTX fraction is used for filling the market gap of light aromatic hydrocarbons in China.

(2) The invention divides the light catalytic cracking diesel oil fraction and the heavy catalytic cracking diesel oil fraction with proper cutting points, and adopts a combined process method, thereby generally improving the selective yield of BTX.

Detailed Description

The following examples further illustrate the invention but are not intended to limit the invention thereto.