CN111484876B

CN111484876B - Method for producing aromatic hydrocarbon and high-quality gasoline from poor-quality catalytic cracking diesel oil

Info

Publication number: CN111484876B
Application number: CN202010302431.9A
Authority: CN
Inventors: 孙世源; 孟凡东; 闫鸿飞; 张亚西; 武立宪; 张瑞风; 杨鑫
Original assignee: China Petroleum and Chemical Corp; Sinopec Engineering Group Co Ltd
Current assignee: China Petroleum and Chemical Corp; Sinopec Engineering Group Co Ltd
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2022-02-22
Anticipated expiration: 2040-04-16
Also published as: CN111484876A

Abstract

The invention discloses a method for producing aromatic hydrocarbon and high-quality gasoline from poor-quality catalytic cracking diesel oil, and relates to the technical field of petroleum refining. Which comprises the following steps: hydrofining poor-quality catalytic cracking diesel to obtain hydrofined diesel, then performing property analysis on the hydrofined diesel to determine a cutting point, and performing cutting separation on the hydrofined diesel to obtain light fraction and heavy fraction; wherein, the heavy fraction is subjected to aromatic extraction by an aromatic extraction device; the raffinate oil rich in saturated hydrocarbon is mixed with light fraction and then is subjected to catalytic cracking reaction to produce high-quality gasoline. The method processes the poor quality catalytic cracking diesel oil by using the hydrogenation-fractionation-extraction combined process, can greatly reduce the yield of poor quality catalytic cracking, produces aromatic hydrocarbon products with high added value and high quality gasoline, can solve the problem of the poor quality diesel oil of refineries while improving the economic benefit, and has good economic benefit and social benefit.

Description

Method for producing aromatic hydrocarbon and high-quality gasoline from poor-quality catalytic cracking diesel oil

Technical Field

The invention relates to the technical field of petroleum refining, in particular to a method for producing aromatic hydrocarbon and high-quality gasoline from poor-quality catalytic cracking diesel oil.

Background

The catalytic cracking diesel oil has a high proportion in the diesel oil pool of China, which accounts for about 30 percent and is a main secondary processing diesel oil component. With the development and change of domestic market demands and environmental requirements, LCO with low cetane number is increasingly difficult to be used as a blending component of the diesel oil for vehicles, and LCO with high cetane number is urgently needed to be provided as a blending component of the diesel oil for vehicles. At present, catalytic diesel is mainly used for blending diesel products after being subjected to hydrotreating. Although the conventional hydrorefining or hydroupgrading route can basically remove sulfur and nitrogen in the catalytic diesel and improve the cetane number of the catalytic diesel to different degrees, the problems of high hydrogen consumption, harsh operating conditions and the like exist, and high aromatic hydrocarbon components in the catalytic diesel cannot be effectively utilized, so that a new catalytic diesel processing route is urgently needed to be found.

Patent document No. CN103214332 discloses a method for producing light aromatic hydrocarbons and high-quality oil products from catalytic cracking diesel oil, in which the catalytic cracking diesel oil is extracted with a solvent to obtain an extract oil rich in polycyclic aromatic hydrocarbons and a raffinate oil rich in alkanes, and the extract oil is subjected to hydrorefining and hydrocracking under hydrogenation conditions to produce light aromatic hydrocarbons and high octane gasoline fractions. The method can obtain light aromatic hydrocarbon and can produce diesel oil with high cetane number and gasoline with high octane number as by-products. However, the method has low diesel oil utilization rate and low byproduct value.

The patent document with publication number CN103805247B discloses a combined process for processing poor diesel oil. Firstly, carrying out hydro-upgrading reaction on inferior diesel fractions such as secondary processing diesel oil and the like, and carrying out aromatic hydrocarbon selective ring-opening reaction; the liquid obtained by separating the reaction effluent is subjected to aromatic extraction; the aromatic hydrocarbon component is used as catalytic cracking feed to carry out catalytic cracking reaction, and gas, catalytic gasoline and catalytic diesel oil are obtained through separation and fractionation, and the catalytic diesel oil can be recycled to the hydrogenation modification reactor. The method converts the poor diesel oil into the catalytic gasoline product with high octane number to the maximum extent, improves the gasoline yield and the octane number of the catalytic device to the maximum extent, but increases the yield of dry gas and coke by taking the aromatic hydrocarbon component as a catalytic cracking raw material to carry out catalytic cracking reaction, and the performance of the cracked diesel oil is worse.

Patent document No. CN106753551 discloses a method for producing gasoline with high octane number by catalytic cracking diesel oil. The method cuts the catalytic diesel oil after hydrofining into fractions with the temperature of less than 280 ℃ and fractions with the temperature of more than 280 ℃, raffinate oil obtained by extracting the fractions with the temperature of more than 280 ℃ with aromatic hydrocarbon enters a catalytic cracking device together with the fractions with the temperature of less than 280 ℃ to produce high-octane gasoline, and extract oil rich in aromatic hydrocarbon is used for aromatic hydrocarbon. However, LCO in the secondary fractionating tower of the catalytic cracking device contains a large amount of bicyclic and tricyclic aromatic hydrocarbons which are not utilized and directly discharged out of the device, and the overall economic benefit is poor.

Patent document No. CN107880934 discloses a method for utilization of catalytic cracking diesel. The method analyzes the composition and the property of the catalytic cracking diesel oil and determines a cutting point; fractionating and cutting the catalytic cracking diesel oil, and separating to obtain light fraction and heavy fraction; performing single-solvent liquid-liquid extraction on the heavy fraction to obtain extract oil rich in aromatic hydrocarbon and raffinate oil rich in saturated hydrocarbon; and carrying out catalytic cracking on the raffinate oil and the light fraction rich in saturated hydrocarbon to produce high-octane gasoline or high-octane gasoline blending components. The method has high gasoline yield, but the aromatic hydrocarbon content of the gasoline is too high, so that the gasoline is difficult to blend with the motor gasoline.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a method for producing aromatic hydrocarbon and high-quality gasoline by poor-quality catalytic cracking diesel oil so as to solve the technical problems.

The invention is realized by the following steps:

a method for producing aromatic hydrocarbon and high-quality gasoline by poor-quality catalytic cracking diesel oil comprises the following steps: which comprises the following steps:

hydrofining poor-quality catalytic cracking diesel to obtain hydrofined diesel;

then, performing property analysis on the hydrofined diesel to determine a cutting point, and performing cutting separation on the hydrogenated catalytic diesel to obtain light fraction and heavy fraction;

performing aromatic extraction on the heavy fraction by using an aromatic extraction device to obtain extract oil rich in aromatic hydrocarbons and raffinate oil rich in saturated hydrocarbons;

then the raffinate oil rich in saturated hydrocarbon is mixed with light fraction to carry out catalytic cracking reaction to produce gasoline.

Poor quality catalytic cracking diesel is a diesel fraction that is difficult to blend into automotive diesel even after hydrofinishing.

The invention provides a method for producing aromatic hydrocarbon and high-quality gasoline by using poor-quality catalytic cracking diesel oil. The hydrorefined diesel is subjected to a property analysis to determine an appropriate cut point so that the light fraction contains as many saturated hydrocarbon components as possible and the heavy fraction contains as many aromatic hydrocarbon components as possible.

And (3) performing aromatic extraction on the heavy fraction to separate extract oil rich in aromatic hydrocarbon and raffinate oil rich in saturated hydrocarbon, and performing catalytic cracking reaction on the saturated hydrocarbon and the light fraction to obtain high-quality gasoline. The extract oil rich in aromatic hydrocarbon can be used for preparing aromatic hydrocarbon products with high added values. The method for producing high-quality gasoline can prepare gasoline with high octane number, low olefin and low aromatic hydrocarbon, and is a vehicle gasoline blending component with excellent performance.

In the preferred embodiment of the present invention, the reaction temperature of the above raffinate oil rich in saturated hydrocarbon and the light fraction for catalytic cracking is 440-650 ℃, preferably 440-530 ℃, and more preferably 440-480 ℃.

The invention adopts a low-temperature catalytic cracking mode to carry out catalytic cracking on the raffinate oil rich in saturated hydrocarbon and the light fraction, thereby obviously reducing the energy consumption of a reaction device and having better economic benefit. Compared with the operation mode of the conventional catalytic cracking unit, the low-temperature cracking method has the advantages that after the second riser is subjected to low-temperature cracking, the yield of dry gas, slurry oil and coke is obviously reduced, and meanwhile, the yield of gasoline is obviously improved.

The catalytic cracking of the raffinate oil rich in saturated hydrocarbon and light fraction mixture is carried out under the low temperature condition, so that the reaction depth of the catalytic cracking can be effectively reduced, and the reduction of the content of aromatic hydrocarbon in gasoline is facilitated.

In the preferred embodiment of the present invention, the reaction temperature for hydrorefining poor quality catalytic cracking diesel oil is 320-390 ℃; preferably, the hydrogen partial pressure of hydrofining is 5.0-10.0MPa, and the volume space velocity is 0.5-1.5h^-1Preference is given toThe volume ratio of hydrogen to oil is 300-800: 1.

The catalyst is selected from conventional hydrofining catalysts, and the inferior catalytic cracking diesel oil is subjected to hydrodesulfurization, hydrodenitrogenation, hydrogenation metal dragging, olefin saturation and partial aromatic saturation reactions under the action of the hydrofining catalysts.

The hydrorefining catalyst contains hydrogenation active component and carrier, the hydrogenation active component is metal of VI group and/or VIII group, and the carrier is thermal inorganic oxide carrier.

The mass of the metal in the hydrogenation active component accounts for 12-30% of the mass of the hydrofining catalyst.

The hydrogenation active component comprises at least one of molybdenum oxide, nickel oxide and tungsten oxide.

In a preferred embodiment of the present invention, the analysis of the properties of the hydrorefined diesel oil includes at least one of density analysis, distillation range analysis, elemental composition analysis and hydrocarbon group composition analysis.

The national standard for density analysis is GB/T13377, the standard for distillation range analysis is ASTM D86, the standard for elemental analysis is SH/T0656, and the standard for hydrocarbon group composition analysis is RAD-T-AN 2033.

And setting the distillation range of the heavy fraction according to the content percentage of the aromatic hydrocarbon in the hydrocarbon family composition analysis, and further determining the cutting point.

In actual use, the distillation ranges of the heavy fraction and the light fraction are determined and the cut point is determined according to the analysis result of the hydrocarbon group composition of the hydrofined diesel. The person skilled in the art can derive the cut point from past experience by analyzing the results.

By analyzing the hydrocarbon components, elements and density in the mixed oil, a more scientific and reasonable distillation range can be designed, and a theoretical reference basis is provided for the subsequent separation of light fraction and heavy fraction. This is beneficial to reducing the aromatic hydrocarbon content in the reaction product gasoline.

In the preferred embodiment of the present invention, after the cutting point is determined by the property analysis, the hydrogenated catalytic diesel oil is cut and separated by using the fractionating tower.

In the preferred embodiment of the present invention, the material temperature of the fractionating tower is set at 220-320 deg.C, preferably, the tower bottom temperature is 100-350 deg.C, the tower top temperature is 100-320 deg.C, and the pressure at the tower top is 0.01-1MPa (gauge pressure).

Light fraction rich in saturated hydrocarbon and monocyclic aromatic hydrocarbon is obtained from the top of the fractionating tower, and heavy fraction rich in bicyclic aromatic hydrocarbon and tricyclic aromatic hydrocarbon is obtained from the bottom of the fractionating tower.

In the preferred embodiment of the present invention, when the heavy fraction is subjected to aromatics extraction by an aromatics extraction apparatus, the extraction solvent used is at least one of dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, N-formylmorpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol and acetonitrile.

In the preferred embodiment of the present invention, the mass ratio of the extraction solvent to the heavy fraction is 0.5-4: 1.

In the preferred embodiment of the present invention, the temperature of the top of the extraction tower used for the extraction is 40-100 ℃, the temperature of the bottom of the extraction tower is 30-90 ℃, and the pressure is 0-2 MPa.

In the preferred embodiment of the present invention, the extracted component is subjected to aromatic fractionation to obtain an extract oil rich in aromatic hydrocarbons and a raffinate oil rich in saturated hydrocarbons.

In the preferred embodiment of the present invention, the raffinate oil and the light fraction are mixed for catalytic cracking, and the catalyst-to-oil ratio of the catalytic cracking is 3-14:1, preferably 3-13:1, and more preferably 4-6: 1.

In a preferred embodiment of the present invention, the catalytic cracking reaction pressure is 0.1-0.4MPa, preferably 0.12-0.38MPa, and more preferably 0.15-0.35 MPa.

In the preferred embodiment of the present invention, the reaction time of the above catalytic cracking is 2 to 5s, preferably 2.2 to 4.5s, and more preferably 2.5 to 4 s.

In the preferred embodiment of the present invention, the above atomized water vapor is 1 to 4 wt%, preferably 1.2 to 3.5 wt%, more preferably 1.5 to 3 wt% of the feed amount.

Under the above catalytic cracking process conditions, gasoline with low aromatic hydrocarbon and high saturated hydrocarbon can be obtained.

The catalyst selected for catalytic cracking is a conventional catalytic cracking catalyst.

In the preferred embodiment of the present invention, the above-mentioned catalytic diesel oil fraction obtained by mixing raffinate oil and light fraction and catalytic cracking is hydrofined and fractionated again.

In order to increase the utilization of the catalytic diesel fraction, the catalytic diesel fraction obtained from the last catalytic cracking may be hydrofinished again.

The invention has the following beneficial effects:

the invention provides a method for producing aromatic hydrocarbon and high-quality gasoline from poor-quality catalytic cracking diesel oil, which is characterized in that the poor-quality catalytic cracking diesel oil is processed by utilizing a hydrogenation-fractionation-extraction combined process, so that the yield of poor-quality catalytic cracking can be greatly reduced, aromatic hydrocarbon products with high additional value and high-quality gasoline are produced, the problem of the outlet of refinery poor-quality diesel oil can be solved while the economic benefit is improved, and the economic benefit and the social benefit are good. The cut point is determined by property analysis, which is beneficial to reducing the content of aromatic hydrocarbon in light fraction.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a schematic flow chart of a production method provided by an embodiment of the invention.

1-conventional catalytic cracking feedstock; 2-a main riser of a catalytic cracking unit; 3-a first reaction product; 4-main fractionation column; 5-a first gas; 6-first catalytic gasoline; 7-first catalytic diesel; 8-first catalytic slurry oil; 9-a hydrogenation reactor; 10-the reaction effluent; 11-a fractionation column; 12-light fraction; 13-heavy fraction; 14-aromatic extraction unit; 15-an extraction solvent; 16-raffinate oil; 17-extract oil; 18-a second riser; 19-a second reaction effluent; 20-a secondary fractionation column; 21-a second gas; 22-second catalytic gasoline; 23-a second catalytic diesel; 24-second catalytic slurry oil.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

Referring to the flow chart of fig. 1, the invention provides a method for producing aromatic hydrocarbon and high-quality gasoline from poor quality catalytic cracking diesel.

The conventional catalytic cracking raw material 1 is firstly introduced into the bottom of a main riser 2 of a catalytic cracking device, and catalytic cracking reaction is carried out at the bottom of the main riser 2 of the catalytic cracking device.

In this example, the outlet temperature of the main riser 2 of the catalytic cracking unit was 510 ℃, the reaction pressure (gauge pressure) was 0.15MPa, the catalyst-to-oil ratio was 6.5:1, and the reaction time was 3.1 s.

The first reaction product 3 is obtained by the reaction and introduced into the main fractionation column 4, and fractionated in the main fractionation column 4. The first gas 5, the first catalytic gasoline 6 and the first catalytic slurry oil 8 separated from the main fractionating tower 4 enter a downstream system. The first catalytic diesel oil 7 separated from the main fractionating tower 4 enters a hydrogenation reactor 9 for hydrofining.

The reaction temperature for hydrofining poor quality catalytic cracking diesel oil is 350 ℃; the hydrogen partial pressure of hydrofining is 5.0MPa, and the volume space velocity is 0.5h^-1The volume ratio of hydrogen to oil was 300: 1.

In the hydrogenation reactor 9, the bicyclic and tricyclic aromatics in the first catalytic diesel 7 are converted into saturated and monocyclic aromatics.

The cut point is determined by analyzing the properties of the hydrofined diesel, the national standard for reference of density analysis is GB/T13377, the standard for reference of distillation range analysis is ASTM D86, the standard for reference of elemental analysis is SH/T0656, and the standard for reference of hydrocarbon group composition analysis is RAD-T-AN 2033.

The reaction effluent 10 (namely refined diesel oil) enters a fractionating tower 11, and the separated light fraction 12 enters the bottom of a second riser 18 to carry out catalytic cracking reaction at a lower reaction temperature.

The material temperature when the fractionating tower 11 feeds is set to be 220 ℃, the bottom temperature is 100 ℃, the top temperature is 100 ℃ and the top pressure is 0.01 MPa.

Heavy fraction 13 fractionated by the fractionating tower 11 flows out from the bottom of the fractionating tower 11 and enters an aromatic hydrocarbon extraction device 14, and after the heavy fraction and an extraction solvent 15 are in countercurrent contact, raffinate oil 16 flows out from the top of the aromatic hydrocarbon extraction device 14, and after being mixed with light fraction 12, the raffinate oil and the light fraction enter the bottom of a second riser 18 of a catalytic cracking device together for catalytic cracking reaction.

In this embodiment, the extraction solvent 15 is dimethylformamide, and in other embodiments, self-adaptive adjustment may be performed as needed.

The mass ratio of the extraction solvent 15 to the heavy fraction is 0.5: 1; the temperature of the top of the extraction device 14 for extracting the aromatic hydrocarbon is 40 ℃, the temperature of the bottom of the extraction device is 30 ℃, and the pressure is 1 MPa.

In addition, in other embodiments, the raffinate 16 may be fed into the bottom of the second riser 18 from other nozzles for catalytic cracking. The raffinate 16 is rich in saturated hydrocarbons.

The extract oil 17, which is rich in aromatics, can be passed to downstream systems for the production of aromatic products.

After the catalytic cracking reaction of the light ends 12 and raffinate 16 in the second riser 18, the second reaction effluent 19 enters a secondary fractionator 20. And the second gas 21, the second catalytic gasoline 22 and the second catalytic slurry oil 24 separated from the secondary fractionating tower 20 enter a downstream system, the separated second catalytic diesel oil 23 is mixed with the first catalytic diesel oil 7 separated from the main fractionating tower 4 and then enters the hydrogenation reactor 9, and hydrofining is carried out in the hydrogenation reactor 9.

The outlet temperature of the second riser 18 was 460 ℃, the reaction pressure (gauge pressure) was 0.15MPa, the catalyst to oil ratio was 4.5:1, the reaction time was 3.2s, the atomized water vapor accounted for 1 wt% of the feed, and the main operating conditions for catalytic cracking were as shown in table 1.

The operation method provided by the embodiment can ensure that the processing capacity of the main riser 2 of the catalytic cracking unit reaches 100 million tons/year, and the processing capacity of the second riser 18 reaches 39.15 million tons/year. The product distribution of the overall process is shown in table 2 and the properties of the resulting catalytic gasoline are shown in table 3.

Example 2

Referring to the flow chart of fig. 1, the present example provides a method for producing aromatic hydrocarbons and high-quality gasoline from poor quality catalytic cracking diesel.

In this example, the outlet temperature of the main riser 2 of the catalytic cracking unit was 500 ℃, the reaction pressure (gauge pressure) was 0.2MPa, the catalyst-to-oil ratio was 6:1, and the reaction time was 2.8 s.

The reaction temperature for hydrofining poor quality catalytic cracking diesel oil is 390 ℃; the hydrogen partial pressure of hydrofining is 10.0MPa, and the volume space velocity is 1.5h^-1The volume ratio of hydrogen to oil was 800: 1.

In the hydrogenation reactor 9, the bicyclic and tricyclic aromatics in the first catalytic diesel 7 are converted into saturated and monocyclic aromatics. The reaction effluent 10 (namely refined diesel oil) enters a fractionating tower 11, and the separated light fraction 12 enters the bottom of a second riser 18 to carry out catalytic cracking reaction at a lower reaction temperature.

The material temperature when the fractionating tower 11 feeds is set to be 320 ℃, the bottom temperature is 350 ℃, the top temperature is 200 ℃ and the top pressure is 0.1 MPa.

In this embodiment, the extraction solvent 15 is N-methylpyrrolidone, and in other embodiments, self-adaptive adjustment may be performed as needed.

The mass ratio of the extraction solvent 15 to the heavy fraction is 3: 1; the temperature of the top of the aromatic extraction device 14 used for extraction is 60 ℃, the temperature of the bottom of the aromatic extraction device is 40 ℃, and the pressure is 1.5 MPa.

The outlet temperature of the second riser 18 was 440 ℃, the reaction pressure (gauge pressure) was 0.2MPa, the catalyst to oil ratio was 4:1, the reaction time was 2.9s, the atomized water vapor accounted for 1 wt% of the feed, and the main operating conditions for catalytic cracking were as shown in table 1.

The operation method provided by the embodiment can ensure that the processing capacity of the main riser 2 of the catalytic cracking unit reaches 100 ten thousand tons per year, and the processing capacity of the second riser 18 reaches 41.4 ten thousand tons per year. The product distribution of the overall process is shown in table 2 and the properties of the resulting catalytic gasoline are shown in table 3.

Comparative example 1

This comparative example provides a process for producing aromatics and high quality gasoline from poor quality catalytic cracking diesel, which differs from example 1 only in that the second riser 18 has a reaction temperature of 530 ℃, a catalyst-to-oil ratio of 8.5:1 for the second riser 18, and a reaction time of 3.1 s. The remaining process conditions were identical to those of example 1.

The operation method provided by the embodiment can enable the processing capacity of the main riser 2 of the catalytic cracking unit to reach 100 million tons/year and the processing capacity of the second riser 18 to reach 34.15 million tons/year. The operation adjustments are shown in table 1, the product distribution of the overall process flow is shown in table 2, and the properties of the resulting catalyzed gasoline are shown in table 3.

Comparative example 2

The comparative example provides a method for producing aromatic hydrocarbon and high-quality gasoline from poor-quality catalytic cracking diesel oil, and adopts a conventional high-low parallel or coaxial heavy oil catalytic cracking process. The main operating conditions of catalytic cracking are shown in Table 1, the product distribution is shown in Table 2, and the properties of the resulting catalytic gasoline are shown in Table 3.

Comparing example 1 with comparative example 2, compared with the conventional process (comparative example 2), by adopting the combined cracking-hydrogenation-fractionation-extraction process of example 1, the yield of liquefied gas is improved by about 1 percent, the yield of gasoline is improved by about 14 percent, catalytic diesel with low additional value is not produced, and the total content of monocyclic aromatic hydrocarbon, bicyclic aromatic hydrocarbon and tricyclic aromatic hydrocarbon is 8.4 percent; the olefin content in the produced gasoline is reduced by about 3 percent, the octane number is improved by nearly 1 unit, and the gasoline can be used as a qualified blending component of the motor gasoline. The production method provided by the invention is beneficial to producing more aromatic hydrocarbon and gasoline.

Comparing example 1 with comparative example 1, the second riser in the combined cracking-hydrogenation-fractionation-extraction process of example 1 adopts lower reaction temperature, and breaks through the operation mode of the conventional catalytic cracking device. Compared with the second riser high-temperature cracking in the comparative example 1, the yield of dry gas, slurry oil and coke in the example 1 is obviously reduced, the yield of gasoline is improved by about 2 percent, the yield of monocyclic aromatic hydrocarbon, bicyclic aromatic hydrocarbon and tricyclic aromatic hydrocarbon is increased by about 1 percent, the content of saturated hydrocarbon of the gasoline is higher, and the content of olefin and aromatic hydrocarbon is lower. Therefore, the gasoline produced by the production process provided by the invention is a more excellent blending component of the motor gasoline. Further, the second riser 18 is operated at low temperature, so that the energy consumption of the device is obviously reduced, and the economic benefit is more obvious.

Comparing example 2 with comparative example 2, compared with the conventional process (comparative example 2), by adopting the cracking-hydrogenation-fractionation-extraction combined process of the invention example 2, the yield of liquefied gas is improved by about 0.48 percent, the yield of gasoline is improved by about 13.9 percent, and the catalytic diesel oil with low added value, monocyclic aromatic hydrocarbon, bicyclic aromatic hydrocarbon and tricyclic aromatic hydrocarbon are not produced by 8.88 percent in total; the olefin content in the produced gasoline is reduced by about 1.7 percent, and the gasoline can be used as a qualified blending component of the motor gasoline. The production method provided by the invention is beneficial to producing more aromatic hydrocarbon and gasoline.

Comparing example 2 with comparative example 1, the second riser in the combined cracking-hydrogenation-fractionation-extraction process of example 2 adopts lower reaction temperature, and breaks through the operation mode of the conventional catalytic cracking device. Compared with the second riser high-temperature cracking in the comparative example 1, the yield of dry gas, slurry oil and coke in the example 2 is obviously reduced, the yield of gasoline is improved, the saturated hydrocarbon content of the gasoline is higher, and the olefin content and the aromatic hydrocarbon content are lower.

The process production method provided by the invention fully utilizes the existing device of the refinery plant, utilizes the poor quality catalytic cracking diesel oil to produce the light aromatic hydrocarbon product with high added value at low cost, and can better solve the problem of the poor quality diesel oil.

Table 1 catalytic cracker main operating conditions.

Table 2 product distribution.

Table 3 yields gasoline properties.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing aromatic hydrocarbon and high-quality gasoline by poor-quality catalytic cracking diesel oil is characterized by comprising the following steps:

hydrofining the poor quality catalytic cracking diesel to obtain hydrofined diesel, wherein the reaction temperature for hydrofining the poor quality catalytic cracking diesel is 320-390 ℃; the hydrogen partial pressure of hydrofining is 5.0-10.0MPa, and the volume space velocity is 0.5-1.5h^-1The volume ratio of hydrogen to oil is 300-800: 1;

then, performing property analysis on the hydrofined diesel to determine a cutting point, and performing cutting separation on the hydrogenated catalytic diesel to obtain light fraction and heavy fraction; analyzing at least one of density analysis, distillation range analysis, element composition analysis and hydrocarbon group composition analysis on the hydrofined diesel oil; setting the distillation range of heavy fraction according to the content percentage of aromatic hydrocarbon in the hydrocarbon group composition analysis, further determining a cutting point, and cutting and separating the hydrogenated catalytic diesel oil by adopting a fractionating tower after determining the cutting point through the property analysis; setting the material temperature of the fractionating tower at 220-320 ℃; the temperature at the bottom of the tower is 100-350 ℃, the temperature at the top of the tower is 100-320 ℃, and the pressure at the top of the tower is 0.01-1 MPa;

performing aromatic extraction on the heavy fraction by using an aromatic extraction device, and performing aromatic fractionation on the extracted components to obtain extract oil rich in aromatic hydrocarbons and raffinate oil rich in saturated hydrocarbons; the extraction solvent is at least one of dimethylformamide, N-methylpyrrolidone, N-formylmorpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol and acetonitrile; the temperature of the top of an extraction tower used for extraction is 40-100 ℃, the temperature of the bottom of the extraction tower is 30-90 ℃, and the pressure is 0-2 MPa; the mass ratio of the extraction solvent to the heavy fraction is 0.5-4: 1;

then mixing raffinate oil rich in saturated hydrocarbon with light fraction, and then carrying out catalytic cracking reaction to produce gasoline, wherein the poor-quality catalytic cracking diesel oil is non-automotive diesel oil, and the reaction temperature of the raffinate oil rich in saturated hydrocarbon and the light fraction which are mixed for catalytic cracking is 460-480 ℃; the catalyst-oil ratio of the catalytic cracking is 3-14:1, and the reaction pressure of the catalytic cracking is 0.1-0.4 MPa; the reaction time of the catalytic cracking is 2-5 s.

2. The process of claim 1, wherein the catalytic cracking has a catalyst to oil ratio of 3 to 13: 1.

3. The process of claim 2, wherein the catalytic cracking has a catalyst to oil ratio of 4-6: 1.

4. The process of claim 1, wherein the catalytic cracking reaction pressure is 0.12 to 0.38 MPa.

5. The process of claim 4, wherein the catalytic cracking reaction pressure is 0.15 to 0.35 MPa.

6. The process according to claim 1, characterized in that the reaction time of the catalytic cracking is 2.2-4.5 s.

7. The process according to claim 6, characterized in that the reaction time of the catalytic cracking is 2.5-4 s.

8. The process of claim 1, wherein the atomizing steam comprises from 1.2 to 3.5 wt.% of the feed.

9. The process of claim 8, wherein the atomizing steam comprises from 1.5 to 3 wt.% of the feed.

10. The method according to claim 1, wherein the raffinate oil and the light fraction are mixed and subjected to catalytic cracking to obtain a catalytic diesel fraction, and the catalytic diesel fraction is subjected to hydrofining and fractionation again.