Method for producing low-carbon olefin and light aromatic hydrocarbon from ethylene tar

Abstract

A method for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar relates to the technical field of petrochemical engineering, and comprises the following steps: cutting and fractionating the ethylene tar at a cutting point of 250-350 DEG C into an ethylene tar light fraction and an ethylene tar heavy fraction; the method comprises the following steps: carrying out selective hydrogenation saturation on the ethylene tar light fraction to obtain a hydrogenated light fraction, and carrying out catalytic cracking on the hydrogenated light fraction in a main riser of a double-riser catalytic cracking device to obtain dry gas, liquefied gas and main riser catalytic gasoline; carrying out delayed coking on the ethylene tar heavy fraction to obtain coker gasoline and coker diesel oil; the coker gasoline enters a second riser for catalytic cracking reaction, and dry gas, liquefied gas and second riser catalytic gasoline are obtained; separating the dry gas and the liquefied gas to obtain a low-carbon olefin product; carrying out cutting fractionation on the main riser catalytic gasoline and the second riser catalytic gasoline to obtain a gasoline light fraction, and carrying out aromatic hydrocarbon extraction on the gasoline light fraction to obtain light aromatic hydrocarbon; according to the invention, the hydrogen consumption can be reduced, the full fraction of the ethylene tar is fully utilized, and the added value of the product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petroleum chemical industry, in particular to a method for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar. BACKGROUND

[0002] As a by-product with high polymerization degree produced in the process of ethylene cracking, ethylene tar is mainly composed of condensed ring aromatic hydrocarbons with short alkyl side chains. Due to the high polymerization and high carbon content of ethylene tar, it is currently mainly used for producing low-value-added products such as road asphalt, fuel blending oil and carbon black, and has not been fully utilized.

[0003] Currently, some methods for improving the added value of ethylene tar have been disclosed.

[0004] For example, CN116004284A discloses a method for producing clean fuel oil from ethylene tar. In this method, ethylene tar is fractionated into light fraction and heavy fraction, the heavy fraction is mixed with conventional coking raw material, and delayed coking is performed to obtain coking gasoline and coking diesel. The obtained coking gasoline is subjected to hydrofining, and the coking diesel is mixed with the light fraction of ethylene tar and subjected to hydroprocessing. The reaction effluent is separated together with the hydrofining product of coking gasoline in a fractionating column to obtain clean gasoline and diesel products. This invention mainly focuses on improving the yield of light fuel oil.

[0005] For example, CN116004284A discloses a method and system for hydrogenation of ethylene tar to light hydrocarbons. However, the aromatic hydrocarbon resources in the heavy aromatic solvent oil are not fully utilized. CN103102976A discloses a method for treating ethylene tar, which mainly focuses on improving the yield of chemical raw material naphthalene. The technical development and economic analysis of hydrogenation of ethylene tar to produce aromatic hydrocarbons (Suying, He Libin, Liaoning Chemical, Vol. 50, No. 12) discloses a technology for producing BTX light aromatic hydrocarbons by three-stage hydrogenation using ethylene tar as raw material. However, this method requires high hydrogen consumption and special equipment, which increases the investment cost.

[0006] In summary, there is no relatively mature technology for producing light aromatic hydrocarbons and low-carbon olefins from ethylene tar on the market. Developing a method for producing light aromatic hydrocarbons and low-carbon olefins from the whole fraction of ethylene tar and fully utilizing the rich aromatic hydrocarbon resources in ethylene tar is an effective development of the technology for producing light aromatic hydrocarbons and low-carbon olefins from ethylene tar. SUMMARY

[0007] The present application aims to provide a method for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar, which is different from the prior art and utilizes ethylene tar in a high-value way.

[0008] In order to solve the above technical problems, the specific scheme adopted by the present application is as follows: a method for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar, the ethylene tar is cut and fractionated into ethylene tar light fraction and ethylene tar heavy fraction at a cutting point of 250-350 DEG C; the ethylene tar light fraction is selectively hydrogenated and saturated to obtain a hydrogenated light fraction, the hydrogenated light fraction enters the main riser catalytic cracking of a dual-riser catalytic cracking device to obtain dry gas, liquefied gas, main riser catalytic gasoline, main riser catalytic diesel and main riser catalytic slurry; the ethylene tar heavy fraction is delayed coking to obtain coking gasoline and coking diesel; the coking gasoline enters the second riser catalytic cracking reaction to obtain dry gas, liquefied gas, second riser catalytic gasoline, second riser catalytic diesel and second riser catalytic slurry; the dry gas and the liquefied gas are separated to obtain low-carbon olefin products; the main riser catalytic gasoline and the second riser catalytic gasoline are cut and fractionated to obtain gasoline light fraction and gasoline heavy fraction, and the gasoline light fraction is pre-hydrogenated and aromatic hydrocarbon-extracted to obtain light aromatic hydrocarbons; wherein, the gasoline heavy fraction returns to the second riser of the dual-riser catalytic cracking device for catalytic cracking reaction; the main riser catalytic slurry and the second riser catalytic slurry are mixed with the ethylene tar heavy fraction for delayed coking; and the main riser catalytic diesel, the second riser catalytic diesel, the coking diesel and the ethylene tar light fraction are mixed for hydrogenation saturation.

[0009] As a further optimization of the above technical solution, the reaction temperature of selective hydrogenation saturation is 320-400 DEG C, the hydrogen partial pressure is 5.0-10.0 MPa, the volume space velocity is 0.5-3 h -1 -1, and the hydrogen / oil volume ratio is 300-800:1.

[0010] As a further optimization of the above technical solution, the catalyst for selective hydrogenation saturation of polycyclic aromatic hydrocarbons can be one or a combination of hydrogenation refining catalysts and hydrogenation cracking catalysts, the active metal in the catalyst for selective hydrogenation saturation of polycyclic aromatic hydrocarbons includes one or several of nickel, cobalt, molybdenum or tungsten, and the mass of the active metal is 10%-30%.

[0011] As a further optimization of the above technical solution, the reaction conditions of the main riser catalytic cracking reaction are as follows: the reaction temperature is 500-600 DEG C, the catalyst / oil ratio is 5-15, the reaction pressure is 0.1-0.5 MPa, the reaction time is 2-5 s, and the atomized steam accounts for 1-5 w% of the feed amount.

[0012] As a further optimization of the above technical solution, the reaction conditions of the second riser catalytic cracking reaction are as follows: the reaction temperature is 550-650 DEG C, the catalyst / oil ratio is 5-15, the reaction pressure is 0.1-0.5 MPa, the reaction time is 2-5 s, and the atomized steam accounts for 1-5 w% of the feed amount.

[0013] As the further optimization of the above technical scheme, the reaction conditions of the ethylene tar heavy fraction, the main riser catalytic slurry and the second riser catalytic slurry for the delayed coking reaction are as follows: the reaction temperature is 420-500 DEG C, the reaction pressure is 0.10-0.15 MPa, and the circulation ratio is 0.10-0.30.

[0014] As the further optimization of the above technical scheme, when the main riser catalytic gasoline and the second riser catalytic gasoline are subjected to cutting fractionation, the cutting temperature used is 50-180 DEG C.

[0015] As the further optimization of the above technical scheme, the reaction temperature during the pre-hydrogenation is 300-420 DEG C, the hydrogen partial pressure is 2.5-3.5 MPa, the hydrogen / oil volume ratio is 300-500:1, and the volume space velocity is 1.5-4 h -1 .

[0016] As the further optimization of the above technical scheme, the extraction solvent used during the aromatic extraction is one or more of sulfolane, dimethyl sulfoxide, dimethyl formamide, N-methyl pyrrolidone, N-formyl morpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol or acetonitrile.

[0017] As the further optimization of the above technical scheme, during the aromatic extraction process, the mass ratio of the extraction solvent to the gasoline light fraction is 3-8:1, the overhead temperature of the extraction column used for the aromatic extraction is 130-190 DEG C, and the pressure is 1.1-2.0 MPa.

[0018] Compared with the prior art, the method has the following beneficial effects:

[0019] 1. The method can convert the ethylene tar which is difficult to be treated by a chemical enterprise into high-quality chemical raw materials such as low-carbon olefins and light aromatic hydrocarbons through the selective cutting fractionation-selective hydrogenation-double riser catalytic cracking-coking combined process, and the product added value is significantly improved.

[0020] 2. The method can maximize the double-ring aromatic hydrocarbons and the polycyclic aromatic hydrocarbons above the double ring by cutting and fractionating the ethylene tar at a suitable cutting point (250-350 DEG C) to obtain the ethylene tar light fraction and the ethylene tar heavy fraction, and the aromatic hydrocarbon resources in the ethylene tar are fully utilized to improve the product added value.

[0021] 3、The application matches different operating conditions in the main riser and the second riser of the dual riser catalytic cracking device, and catalytically cracks the hydrogenated light fraction in the main riser, so that dry gas and liquefied gas are obtained, and the low carbon olefins are obtained through subsequent separation; the catalytic gasoline obtained after the catalytic cracking of the main riser is cut and fractionated, and the heavy fraction of the aromatic-rich gasoline obtained through the cutting and fractionation is catalytically cracked in the second riser, and the reaction severity in the second riser is higher than that in the main riser, so that the heavy fraction of the aromatic-rich gasoline is further cracked into gasoline containing C6-C8 light aromatic hydrocarbons and low carbon olefins such as ethylene and propylene, thereby improving the yield of the low carbon olefins and the light aromatic hydrocarbons in the light fraction of the ethylene tar; meanwhile, the heavy fraction of the ethylene tar, the catalytic slurry obtained through the catalytic cracking of the main riser, and the catalytic slurry obtained through the catalytic cracking of the second riser are subjected to delayed coking, and the catalytic gasoline obtained after the delayed coking is cracked into gasoline containing C6-C8 light aromatic hydrocarbons in the second riser with high severity and produces low carbon olefins such as ethylene and propylene, so that the light aromatic hydrocarbons and the low carbon olefins are produced through the heavy fraction of the ethylene tar; the intermediate products in the catalytic cracking processes of the main riser and the second riser are returned to different processing procedures for reprocessing, and the final yield of the light aromatic hydrocarbons and the low carbon olefins is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a process flow diagram of the application.

[0023] Figure 2 It is a process flow diagram of Comparative Example 1. DETAILED DESCRIPTION

[0024] The technical solutions of the application are further described in detail below. The parts not described and disclosed in detail in the following examples of the application, such as the structure of the hydrogenation device and the dual riser catalytic cracking device, the aromatic hydrocarbon combination device, and the gas separation device, should be understood as the prior art known or should be known by those skilled in the art.

[0025] As shown in Figure 1 The application discloses a method for producing low carbon olefins and light aromatic hydrocarbons from ethylene tar. The ethylene tar is cut and fractionated into a light fraction and a heavy fraction at a cutting point of 250-350℃, and the light fraction and the heavy fraction are treated by different processing methods to improve the added value of the ethylene tar. The content of the bicyclic aromatic hydrocarbons in the ethylene tar can be maximized by using the cutting point of 250-350℃.

[0026] Specifically, the ethylene tar light fraction is selectively hydrogenated and saturated to selectively hydrogenate and saturate polycyclic aromatic hydrocarbons in the ethylene tar light fraction into monocyclic aromatic hydrocarbons, to obtain a hydrogenated light fraction; the ethylene tar light fraction is selectively hydrogenated and saturated in a hydrogenation device, the reaction temperature is 320-400℃, the hydrogen partial pressure is 5.0-10.0 MPa, the volume space velocity is 0.5-3 h -1 , and the hydrogen / oil volume ratio is 300-800:1. The catalyst for selectively hydrogenating and saturating the polycyclic aromatic hydrocarbons can be one or a combination of hydrogenation refining catalysts and hydrogenation cracking catalysts; in a preferred embodiment of the present application, the hydrogenation refining catalyst is a catalyst containing active metals, the active metals including one or several of nickel, cobalt, molybdenum or tungsten, and the mass of the active metals is 10%-30%.

[0027] The hydrogenated light fraction enters a main riser catalytic cracking device of a dual-riser catalytic cracking device to obtain dry gas, liquefied gas, main riser catalytic gasoline, main riser catalytic diesel and main riser catalytic slurry; the reaction temperature of the in-riser cracking reaction is 500-600℃, the catalyst / oil ratio is 5-15, the reaction pressure is 0.1-0.5 MPa (gauge pressure), the reaction time is 2-5 s, the atomized water vapor accounts for 1-5 w% of the feed amount, and the catalyst for the in-riser cracking reaction is a conventional catalytic cracking catalyst.

[0028] The ethylene tar heavy fraction is subjected to delayed coking to obtain coking dry gas, coking liquefied gas, coking gasoline, coking diesel, coking wax oil and petroleum coke; the delayed coking reaction is carried out in a delayed coking device, the selected reaction temperature is 420-500℃, the reaction pressure is 0.10-0.15 MPa, and the circulation ratio is 0.10-0.30. The coking dry gas and the coking liquefied gas are separated and extracted by a subsequent gas separation device to obtain a low-carbon olefin product.

[0029] The coking gasoline obtained after the delayed coking enters a second riser catalytic cracking reaction to obtain dry gas, liquefied gas, second riser catalytic gasoline, second riser catalytic diesel and second riser catalytic slurry; the reaction temperature of the second riser catalytic cracking reaction is 550-650℃, the catalyst / oil ratio is 5-15, the reaction pressure is 0.1-0.5 MPa (gauge pressure), the reaction time is 2-5 s, the atomized water vapor accounts for 1-5 w% of the feed amount, and the catalyst in the second riser is a conventional catalytic cracking catalyst.

[0030] The dry gas and the liquefied gas produced by the main riser and the second riser are separated by a gas separation device to obtain a low-carbon olefin product; the low-carbon olefin product includes ethylene and propylene, and the operating conditions of the gas separation device are consistent with the conventional industrial operating conditions.

[0031] The main riser catalytic gasoline and the second riser catalytic gasoline are subjected to cutting fractionation to obtain gasoline light fraction and gasoline heavy fraction, the cutting fractionation process adopts a conventional flash tower or a fractionating tower, the cutting temperature is 50-180 DEG C, the gasoline light fraction is distilled from the upper part of the tower, and the gasoline heavy fraction is distilled from the lower part of the tower, the gasoline light fraction obtained by cutting fractionation is rich in C6-C8 light aromatic hydrocarbon, and the gasoline heavy fraction obtained is rich in C9 aromatic hydrocarbon gasoline heavy fraction.

[0032] The fractionated gasoline light fraction is subjected to pre-hydrogenation, aromatic extraction and aromatic fractionation in an aromatic combination device to obtain light aromatic hydrocarbon and raffinate gasoline, the main component of the light aromatic hydrocarbon is BTX; the pre-hydrogenation treatment reaction temperature is 300-420 DEG C, the hydrogen partial pressure is 2.5-3.5 MPa, the hydrogen / oil volume ratio is 300-500:1, the volume space velocity is 1.5-4 h -1 -1; the extraction solvent is one or more of sulfolane, dimethyl sulfoxide, dimethyl formamide, N-methyl pyrrolidone, N-formyl morpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol or acetonitrile; the mass ratio of the extraction solvent to the gasoline light fraction is 3-8:1, the aromatic extraction extraction tower top temperature is 80-190 DEG C, and the pressure is 1.1-2.0 MPa.

[0033] The above method selects appropriate processing technology and treatment conditions for the ethylene tar light fraction and the ethylene tar heavy fraction, so as to obtain light aromatic hydrocarbon and low-carbon olefin, and the intermediate product in the treatment process of the ethylene tar light fraction and the ethylene tar heavy fraction is further processed.

[0034] The gasoline heavy fraction obtained by cutting fractionation of the main riser catalytic gasoline and the second riser catalytic gasoline is returned to the second riser for catalytic cracking reaction, at this time, the catalytic cracking reaction conditions are consistent with the conditions when the coking gasoline obtained after delayed coking enters the second riser catalytic cracking reaction.

[0035] The main riser catalytic slurry and the second riser catalytic slurry are returned to the delayed coking device for delayed coking, and the reaction conditions are consistent with those when the ethylene tar heavy fraction is delayed coked. Since the main riser catalytic slurry and the second riser catalytic slurry are both heavy products obtained from catalytic cracking process, the added value of this part of product is low and it is difficult to process, in the further processing process, if it is recycled back to the catalytic cracking device, the product distribution of the catalytic cracking device will be deteriorated, the present application recycles it back to the delayed coking device, since the delayed coking device can process relatively poor raw materials, the yield of low-carbon olefin and light aromatic hydrocarbon is further improved by recycling the catalytic slurry.

[0036] The main riser catalytic diesel, the second riser catalytic diesel and the coking diesel are returned to the hydrogenation device for selective hydrogenation saturation, and the reaction conditions are consistent with those when the ethylene tar light fraction is selectively hydrogenated and saturated.

[0037] The method for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar according to the present application separates the ethylene tar according to a suitable cutting point to obtain ethylene tar light fraction, which is first saturated by selective hydrogenation to saturate polycyclic aromatic hydrocarbons in the ethylene tar light fraction into monocyclic aromatic hydrocarbons, and then cracked in the main riser of a dual-riser catalytic cracking device to break the side chains of the monocyclic aromatic hydrocarbons, thereby obtaining main riser catalytic gasoline containing a large amount of monocyclic aromatic hydrocarbon components; the aromatic hydrocarbon-rich heavy fraction obtained by selective cutting and fractionation of the main riser catalytic gasoline is further cracked into C6-C8 light aromatic hydrocarbon gasoline and low-carbon olefins such as ethylene and propylene in the second riser at a higher reaction severity, the second riser catalytic gasoline returns to the cutting and fractionation device to further tap the aromatic hydrocarbon resources in the gasoline, and the aromatic hydrocarbon-rich gasoline light fraction enters an aromatic hydrocarbon extraction device to produce light aromatic hydrocarbons such as BTX; the ethylene tar heavy fraction enters a delayed coking device together with the main riser catalytic slurry and the second riser catalytic slurry to be subjected to coking reaction for lightening treatment, and then the coking diesel oil and catalytic diesel oil rich in aromatic components obtained are returned to a hydrogenation device for selective hydrogenation saturation, thereby further improving the utilization of aromatic hydrocarbon resources, and the hydrogenation products are further converted into catalytic gasoline containing a large amount of monocyclic aromatic hydrocarbon components through a catalytic cracking device, and the easily cracked coking gasoline can increase the production of low-carbon olefins such as ethylene and propylene in the second riser at high severity.

[0038] The method can convert the ethylene tar that is difficult for a chemical enterprise to process into high-quality chemical raw materials such as low-carbon olefins and light aromatic hydrocarbons through a selective cutting and fractionation-selective hydrogenation-dual-riser catalytic cracking-coking combined process, and match corresponding processing processes and operating conditions for different intermediate products, thereby significantly improving the product added value.

[0039] Example 1

[0040] A method for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar, the process flow is as shown in Figure 1 Table 1, the main operating conditions of the whole process are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0041] The specific method is as follows:

[0042] The ethylene tar is cut and fractionated into ethylene tar light fraction and ethylene tar heavy fraction at a cutting point of 280°C, wherein the polycyclic aromatic hydrocarbons in the ethylene tar light fraction are selectively hydrogenated and saturated into monocyclic aromatic hydrocarbons to obtain hydrogenated light fraction, and the ethylene tar light fraction is selectively hydrogenated and saturated in the hydrogenation device, the reaction temperature is 385°C, the hydrogen partial pressure is 8.0 MPa, the volume space velocity is 2.5 h -1 , and the hydrogen / oil volume ratio is 600:1. The active metal in the polycyclic aromatic hydrocarbon selective hydrogenation treatment catalyst is nickel, and the mass of the active metal is 13%.

[0043] The hydrogenated light fraction enters the main riser cracking of the dual riser catalytic cracking device to obtain dry gas, liquefied gas, main riser catalytic gasoline, main riser catalytic diesel and main riser catalytic slurry; the reaction temperature of the in-riser cracking reaction is 550°C, the catalyst / oil ratio is 10, the reaction pressure is 0.2 MPa (gauge pressure), the reaction time is 2.5 s, the atomized water vapor accounts for 3% of the feed amount, and the catalyst for the in-riser cracking reaction is a conventional catalytic cracking catalyst.

[0044] The heavy fraction of the ethylene tar is subjected to delayed coking to obtain coking gasoline and coking diesel; the delayed coking reaction is carried out in a delayed coking device, and the selected reaction temperature is 480°C, the reaction pressure is 0.13 MPa, and the circulation ratio is 0.25.

[0045] The coking gasoline obtained after the delayed coking enters the second riser catalytic cracking reaction to obtain dry gas, liquefied gas, second riser catalytic gasoline, second riser catalytic diesel and second riser catalytic slurry; the reaction temperature of the second riser catalytic cracking reaction is 580°C, the catalyst / oil ratio is 10, the reaction pressure is 0.2 MPa (gauge pressure), the reaction time is 3 s, the atomized water vapor accounts for 3% of the feed amount, and the catalyst in the second riser is a conventional catalytic cracking catalyst.

[0046] The dry gas and the liquefied gas produced by the main riser and the second riser are separated by a gas fractionation device to obtain a low-carbon olefin product; the low-carbon olefin product includes ethylene and propylene; the operating conditions of the gas fractionation device are consistent with the conventional industrial operating conditions.

[0047] The main riser catalytic gasoline and the second riser catalytic gasoline are subjected to cutting fractionation to obtain gasoline light fraction and gasoline heavy fraction; the cutting fractionation process uses a fractionation column, the cutting temperature used is 150°C, the gasoline light fraction is distilled from the upper part of the column, and the gasoline heavy fraction is distilled from the lower part of the column.

[0048] The gasoline light fraction obtained by the fractionation is subjected to pre-hydrogenation and aromatic extraction to obtain light aromatic hydrocarbons; the reaction temperature of the pre-hydrogenation treatment is 350°C, the hydrogen partial pressure is 3.2 MPa, the hydrogen / oil volume ratio is 400:1, the volume space velocity is 2.5 h -1 ; the extraction solvent is sulfolane; the mass ratio of the extraction solvent to the gasoline light fraction is 8:1, the overhead temperature of the extraction column used for the aromatic extraction is 80°C, and the pressure is 2.0 MPa.

[0049] The gasoline heavy fraction obtained by the cutting fractionation of the main riser catalytic gasoline and the second riser catalytic gasoline is returned to the second riser for catalytic cracking reaction; at this time, the conditions of the catalytic cracking reaction are consistent with the conditions of the second riser catalytic cracking reaction of the coking gasoline obtained after the delayed coking.

[0050] The main riser catalytic oil slurry and the second riser catalytic oil slurry are returned to the delayed coking device for delayed coking, and the reaction conditions are consistent with those when the ethylene tar heavy fraction is delayed coked.

[0051] The main riser catalytic diesel oil, the second riser catalytic diesel oil and the coking diesel oil are returned to the hydrogenation device for selective hydrogenation saturation, and the reaction conditions are consistent with those when the ethylene tar light fraction is selectively hydrogenated and saturated.

[0052] Example 2

[0053] According to the process flow as described in Example 1, the difference is that the cutting temperature of the ethylene tar is different, and in this example, the cutting temperature is 320°C. The main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0054] Example 3

[0055] According to the process flow as described in Example 1, the difference is that the cutting temperature of the ethylene tar and the reaction temperature of the main riser of the catalytic cracking are different, and in this example, the cutting temperature of the ethylene tar is 320°C, and the reaction temperature of the main riser of the catalytic cracking is 580°C. The main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0056] Example 4

[0057] According to the process flow as described in Example 1, the difference is that the cutting temperature of the ethylene tar and the reaction temperature of the main riser and the reaction temperature of the second riser of the catalytic cracking are different, and in this example, the cutting temperature of the ethylene tar is 320°C, the reaction temperature of the main riser of the catalytic cracking is 580°C, and the reaction temperature of the second riser is 620°C. The main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0058] Comparative Example 1

[0059] According to the process flow as shown in Figure 2 The main difference between Examples 3 and 4 is that a single riser of catalytic cracking is used, and the hydrogenated light fraction, the gasoline heavy fraction and the coking gasoline directly enter the riser for cracking. The main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3. Table 1 Properties of ethylene tar Table 2 Main operating conditions Table 3 Product distribution of the whole process

[0060] As can be seen from Table 3, the method of the present application can convert ethylene tar into high-value-added low-carbon olefin and light aromatic products. With the operating conditions in the examples, the low-carbon olefin + light aromatic product yield can generally reach more than 40 w%.

[0061] Compared with Comparative Example 1, Examples 3 and 4 use the method provided by the present application to further tap the aromatic resources in the raw materials, significantly improve the BTX yield of the process, and thus improve the low-carbon olefin + light aromatic product yield. By selecting appropriate ethylene tar cutting temperature and operating conditions, the low-carbon olefin + light aromatic product yield can be further improved, thereby improving the overall economic benefit of the process.

[0062] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing low-carbon olefins and light aromatics from ethylene tar, characterized in that: The ethylene tar is cut and fractionated at a cutting point of 250-350° C. into an ethylene tar light fraction and an ethylene tar heavy fraction; The ethylene tar light fraction is selectively hydrogenated to obtain a hydrogenated light fraction, and the hydrogenated light fraction is fed into the main riser of a double riser catalytic cracking unit for cracking to obtain dry gas, liquefied gas, main riser catalytic gasoline, main riser catalytic diesel and main riser catalytic oil slurry; The heavy fraction of ethylene tar is subjected to delayed coking to obtain coker gasoline and coker diesel; the coker gasoline enters the second riser for catalytic cracking reaction to obtain dry gas, liquefied gas, second riser catalytic gasoline, second riser catalytic diesel and second riser catalytic oil slurry; Dry gas and liquefied gas are extracted to obtain light olefin products; The main riser catalytic gasoline and the second riser catalytic gasoline are cut and fractionated to obtain gasoline light fraction and gasoline heavy fraction, and the gasoline light fraction is pre-hydrogenated and aromatics extracted to obtain light aromatics; Among them, the gasoline heavy fraction is returned to the second riser of the double riser catalytic cracking unit for catalytic cracking reaction; the main riser catalytic oil slurry and the second riser catalytic oil slurry are mixed with the ethylene tar heavy fraction for delayed coking; the main riser catalytic diesel, the second riser catalytic diesel, the coking diesel and the ethylene tar light fraction are mixed for hydrogenation and saturation.

2. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The reaction temperature for selective hydrogenation saturation is 320-400°C, the hydrogen partial pressure is 5.0-10.0 MPa, and the volume space velocity is 0.5-3 h -1 , the hydrogen / oil volume ratio is 300~800:

1.

3. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The selective hydrogenation saturation catalyst is a catalyst containing active metals, wherein the active metals include one or more of nickel, cobalt, molybdenum or tungsten, and the mass of the active metals is 10% to 30%.

4. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The reaction conditions of the main riser catalytic cracking reaction are as follows: reaction temperature of 500-600°C, catalyst-oil ratio of 5-15, reaction pressure of 0.1-0.5 MPa, reaction time of 2-5 seconds, and atomized water vapor accounting for 1-5w% of the feed amount.

5. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The reaction conditions of the second riser catalytic cracking reaction are as follows: reaction temperature of 550-650°C, catalyst-oil ratio of 5-15, reaction pressure of 0.1-0.5 MPa, reaction time of 2-5 s, and atomized water vapor accounting for 1-5 w% of the feed amount.

6. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The reaction conditions for the delayed coking reaction of the ethylene tar heavy fraction, the main riser catalytic oil slurry and the second riser catalytic oil slurry are as follows: reaction temperature of 420-500°C, reaction pressure of 0.10-0.15 MPa, and circulation ratio of 0.10-0.

30.

7. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: When the catalytic gasoline of the main riser and the catalytic gasoline of the second riser are cut and fractionated, the cutting temperature adopted is 50-180°C.

8. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The reaction temperature during pre-hydrogenation is 300-420°C, the hydrogen partial pressure is 2.5-3.5 MPa, the hydrogen / oil volume ratio is 300-500:1, and the volume space velocity is 1.5-4 h -1 .

9. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The extraction solvent for the aromatic hydrocarbon extraction is one or more of sulfolane, dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, N-formylmorpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol or acetonitrile.

10. The method for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: During the aromatics extraction process, the mass ratio of the extraction solvent to the gasoline light fraction is 3 to 8:1, the top temperature of the extraction tower used for aromatics extraction is 130 to 190°C, and the pressure is 1.1 to 2.0 MPa.

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