CN112708453B

CN112708453B - Method for producing propylene

Info

Publication number: CN112708453B
Application number: CN201911024392.4A
Authority: CN
Inventors: 杨超; 龚剑洪; 谢朝钢; 朱根权; 沙有鑫; 成晓洁
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2019-10-25
Filing date: 2019-10-25
Publication date: 2022-11-15
Anticipated expiration: 2039-10-25
Also published as: CN112708453A

Abstract

The invention relates to the field of propylene production, and discloses a method for producing propylene, which comprises the following steps: (1) Carrying out a first catalytic cracking reaction on light raw oil and a first regenerated catalyst to obtain a first oil-agent mixture, separating the first oil-agent mixture to obtain a first oil gas and a first to-be-generated catalyst, and dividing the first to-be-generated catalyst into a first to-be-generated catalyst A and a first to-be-generated catalyst B; (2) Carrying out a second catalytic cracking reaction on the heavy raw oil, the first to-be-regenerated catalyst A and a second regenerated catalyst to obtain a second oil mixture; (3) Carrying out a third catalytic cracking reaction on the second oil agent mixture to obtain a third oil agent mixture; introducing the spent catalyst into a stripper for stripping, and regenerating and recycling the stripped spent catalyst; the mass ratio of the heavy raw oil to the light raw oil is 0.5-2:1. the method provided by the invention can improve the yield of propylene while processing a large proportion of light raw oil.

Description

Method for producing propylene

Technical Field

The invention relates to the field of propylene production, in particular to a method for producing propylene.

Background

In 2015, the crude oil processing capacity of a domestic catalytic cracking unit is about 7.5 hundred million tons per year, the operating rate of the catalytic cracking unit is about 70 percent, and the consumption demand of diesel oil is turned. With the further expansion of oil refining capacity and the popularization of new energy automobiles, the demand of automobile fuel continues to decline, and by 2020, the operation rate of a catalytic cracking unit is reduced to 68%, and the demand of gasoline consumption will have inflection points. A large number of oil refining devices will be idle, and transformation to chemical engineering will be the exit of oil refining enterprises.

The catalytic cracking technology of heavy oil developed by the Chinese petrochemical science and chemistry institute is the first catalytic cracking technology which is verified by industry and takes the production of propylene as a main target product. The heavy oil is used as a raw material, and the yield of the propylene is up to 15-25%. The DCC technology for producing low carbon olefins by catalytic cracking of heavy oil is described in CN1234426A, CN1388215A, CN1566272A, etc.

On the basis of the DCC technology, the reaction environment of a bed reactor is flexibly controlled by adopting a second lifting pipe, the primary cracking reaction of heavy oil and the secondary cracking reaction environment of gasoline are optimized, the yield of dry gas and coke is further reduced, and the DCC-plus technology is developed. The DCC-plus technology is described in detail in CN1333046C, CN1978411A, CN1986505A, CN100465250C, CN101029248A, etc.

The DCC-plus process recycles the C4/cracked naphtha to the second reaction zone for continuous reaction, and the propylene is further increased through oligomerization and cracking, so that the method has obvious economic advantages in a plurality of carbon four processing and utilizing schemes. After the MTBE unit is shut down, a significant amount of the carbon four resource is available as feed to the DCC-plus unit, and it is known that small molecules such as carbon four need to be cracked at high reaction temperatures, and the propylene yield is significantly reduced in the catalytic cracking unit if the throughput of the second reaction zone is increased.

Disclosure of Invention

The invention aims to provide a novel method for producing propylene, which can process a large-proportion light raw oil and improve the yield of the propylene.

The present invention provides a process for producing propylene, the process comprising:

(1) The method comprises the steps of contacting light raw oil with a first regenerated catalyst in a first fluidized bed reactor to perform a first catalytic cracking reaction to obtain a first oil mixture, separating the first oil mixture to obtain a first oil gas and a first to-be-generated catalyst, and dividing the first to-be-generated catalyst into a first to-be-generated catalyst A and a first to-be-generated catalyst B;

(2) Contacting the heavy raw oil with a first catalyst A to be regenerated and a second regenerated catalyst in a riser reactor to perform a second catalytic cracking reaction to obtain a second oil mixture;

(3) Introducing the second oil mixture into a second fluidized bed reactor to carry out a third catalytic cracking reaction to obtain a third oil mixture; separating the third oil agent mixture to obtain third oil gas and a third spent catalyst, introducing the first spent catalyst B and the third spent catalyst into a stripper for steam stripping, regenerating the stripped spent catalyst, and introducing the obtained regenerated catalyst into the first fluidized bed reactor and the riser reactor for recycling;

the mass ratio of the heavy raw oil to the light raw oil is 0.5-2:1.

preferably, the mass ratio of the first catalyst A to be regenerated to the second regenerated catalyst is 0.1-1:1, preferably 0.2 to 0.5:1.

the method for producing propylene provided by the invention processes the light raw oil in the fluidized bed reactor independently, and because the coking rate of the light raw oil is low, the activity of the catalyst after the reaction is still higher, and part of the catalyst is introduced into the heavy raw oil cracking reactor, the oil agent contact temperature of the heavy raw oil can be reduced, the coking reaction of the heavy raw oil is inhibited, and the propylene yield of the heavy raw oil is improved.

The method for producing propylene provided by the invention can obviously improve the yield of propylene and simultaneously reduce the yield of dry gas and coke. In addition, the method provided by the invention is not limited by the processing proportion of the light raw oil, and the oil ratio of the heavy raw oil cracking agent can be flexibly adjusted.

Drawings

FIG. 1 is a schematic flow diagram of the process for producing propylene described in example 1.

Description of the reference numerals

1. Riser reactor 11 second regenerated catalyst transfer pipe

12. Heavy raw oil feed nozzle 13 riser reactor outlet

2. First fluidized bed reactor

21. First regenerated catalyst delivery pipe 22 light feedstock oil feed nozzle

23. Spent catalyst return inclined pipe 24 first spent catalyst conveying pipe

3. Second fluidized bed reactor 4 second settler

5. First settler 6 stripper

61. Second spent catalyst conveying pipe 7 regenerator

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.

In the present invention, the terms "first" and "second" do not have any limiting effect, but are used only for clarity and convenience of description to distinguish the operations performed at different stages and the added materials.

the mass ratio of the heavy raw oil to the light raw oil is 0.5-2:1.

the distribution ratio of the first to-be-regenerated catalyst a to the first to-be-regenerated catalyst B is not particularly limited in the present invention, and preferably, the mass ratio of the first to-be-regenerated catalyst a to the second regenerated catalyst is 0.1 to 1:1, more preferably 0.2 to 0.5:1. with this preferred embodiment, the reduction of the oil contact temperature of the heavy feedstock is more facilitated, the coking reaction of the heavy feedstock is suppressed, and the propylene yield of the heavy feedstock is further improved.

The present invention has a wide range of operating conditions for the first fluidized bed reactor, preferably, the operating conditions for the first fluidized bed reactor include: the reaction temperature is 610-670 ℃, and the weight hourly space velocity is 2-8h ^-1 It is further preferable that the reaction temperature is 630-650 ℃ and the weight hourly space velocity is 3-6h ^-1 。

According to the invention, in the step (2), the heavy raw oil is contacted with a catalyst in a riser reactor to carry out catalytic cracking reaction, and the catalyst consists of a first catalyst A to be regenerated and a second regenerated catalyst. The operation mode of the second catalytic cracking reaction in step (2) is not particularly limited, and specifically, the first to-be-regenerated catalyst a and the second regenerated catalyst are introduced into the bottom of the riser reactor, and the heavy raw oil is injected through the nozzle, so that the heavy raw oil is in contact reaction with the first to-be-regenerated catalyst a and the second regenerated catalyst.

According to the present invention, preferably, the operating conditions of said riser reactor comprise: the agent-oil ratio is 5-25, the oil-gas retention time is 0.5-5s, and the outlet temperature is 550-590 ℃; further preferably, the agent-oil ratio is 8-15, the oil-gas retention time is 1-3s, and the outlet temperature is 560-580 ℃. The method provided by the invention can not only operate in a riser reactor at a larger catalyst-to-oil ratio, but also reduce the oil-to-oil contact temperature of the heavy raw oil, inhibit the coking reaction of the heavy raw oil and improve the propylene yield of the heavy raw oil.

The present invention has a wide range of operating conditions for the second fluidized bed reactor, and preferably, the operating conditions for the second fluidized bed reactor include: the reaction temperature is 540-580 ℃, and the weight hourly space velocity is 2-8h ^-1 Further preferably, the reaction temperature is 560-580 ℃, and the weight hourly space velocity is 4-7h ^-1 。

The first fluidized bed reactor, the second fluidized bed reactor, and the riser reactor may each independently be a reactor conventionally used in the art. The riser reactor can be of the same diameter or variable diameter, and can be of a straight pipe or a curved pipe. Preferably, the riser reactor is a straight pipe with equal diameter or variable diameter, or a curved pipe with equal diameter or variable diameter. Further preferably, the riser reactor is a straight pipe of equal diameter.

According to a preferred embodiment of the invention, the method further comprises: dividing the light raw oil into a light raw oil I and a light raw oil II, and introducing the light raw oil II into a riser reactor; wherein the mass ratio of the total amount of the light raw oil II and the heavy raw oil to the light raw oil I is 4-5:1. in this preferred embodiment, when a larger amount of light raw oil is processed, the light raw oil is separated into two parts, light raw oil I and light raw oil II, and the light raw oil II is sent to the riser reactor and processed.

According to the invention, preferably, the light raw oil II is contacted with the first catalyst A to be regenerated and the second regenerated catalyst to carry out catalytic cracking reaction to obtain a mixture, and then the heavy raw oil is introduced into the riser reactor to be contacted with the mixture to carry out reaction to obtain the second oil mixture. In this preferred embodiment, the light raw oil II is first contacted with the first catalyst a to be regenerated and the second regenerated catalyst to react, then the heavy raw oil is introduced, and the mixture obtained by the contact reaction of the heavy raw oil II with the light raw oil a and the first catalyst a to be regenerated and the second regenerated catalyst is further contacted to react. By adopting the preferred embodiment, the light raw oil is cracked by utilizing the high-temperature, high-activity and high-density catalyst reaction zone at the bottom of the riser reactor, and meanwhile, the contact temperature of the heavy raw oil and the catalyst can be reduced. The preferred embodiment is more beneficial to flexibly adjusting the circulation ratio of the first regenerated catalyst and the second regenerated catalyst, and is more beneficial to further improving the yield of propylene and simultaneously reducing the yield of dry gas and coke.

According to a preferred embodiment of the present invention, the heavy feed oil is introduced after the introduction of the light feed oil II into the riser reactor for 0.1 to 2 seconds, preferably 0.3 to 1 second.

According to an embodiment of the present invention, the heavy feedstock oil is introduced into the upper portion of the light feedstock oil II, and the introduction of the heavy feedstock oil is to terminate the reaction of the light feedstock oil II, and the reaction time of the light feedstock oil II is to delay the introduction time of the heavy feedstock oil to the light feedstock oil II.

According to the present invention, specifically, the separation of the first oil mixture in the step (1) and the separation of the third oil mixture in the step (3) (gas-solid separation) are not particularly limited, and can be performed according to the conventional technical means in the field. The gas-solid separation may be carried out in a settler.

The first oil gas obtained by separating the first oil agent mixture and the third oil gas obtained by separating the third oil agent mixture can be respectively sent to a subsequent separation system, or the first oil gas and the third oil gas can be mixed and then sent to the subsequent separation system together. Introducing a first catalyst to be generated (a first catalyst B to be generated) obtained by separating the first oil agent mixture and a third catalyst to be generated obtained by separating the third oil agent mixture into a stripper for steam stripping.

The stripping method in step (3) is not particularly limited, and the stripping can strip out the adsorbed hydrocarbon products, and the stripping can be a conventional method in the art, and the stripping is not particularly limited, and is well known to those skilled in the art and will not be described herein again.

The regeneration method in the step (3) is not particularly limited in the present invention, and various regeneration methods conventionally used in the art, such as coke-burning regeneration, may be used. Preferably, the temperature of the regeneration is 660 to 720 ℃.

According to the present invention, the heavy raw oil and the light raw oil have meanings conventionally explained in the art, and preferably, the heavy raw oil is at least one selected from the group consisting of vacuum gas oil, atmospheric gas oil, coker gas oil, deasphalted oil, vacuum residue, atmospheric residue, hydrogenated heavy oil, oil sand oil, shale oil, synthetic oil, animal and vegetable fats and oils, and coal liquefied oil. Specifically, the distillation range of the heavy raw oil is above 300 ℃.

According to the present invention, the light feedstock oil is preferably a hydrocarbon fraction having 4 to 20 carbon atoms and a distillation range of 300 ℃ or lower, and more preferably the light feedstock oil is at least one selected from the group consisting of a catalytically cracked C4 hydrocarbon fraction, a catalytically cracked light gasoline fraction, a straight run naphtha and a straight run diesel.

The catalyst of the present invention is not particularly limited in kind, and may be various catalytic cracking catalysts conventionally used in the art. Specifically, the first regenerated catalyst and the second regenerated catalyst contain molecular sieves. It is preferred for the present invention that the molecular sieve is selected from at least one of Y zeolite, ZSM-5 zeolite, high-silica zeolite having a pentasil structure, and beta type zeolite. More preferably, the molecular sieve selects at least one of Y or HY type zeolite with or without rare earth, ultrastable Y type zeolite with or without rare earth, ZSM-5 series zeolite, high silica zeolite having a pentasil structure, and beta zeolite.

The catalyst can be obtained by commercial products or can be prepared by the existing method.

The present invention will be described in detail below by way of examples.

The catalytic cracking catalysts used in the examples and comparative examples were industrially produced by Qilu Branch of catalyst, china petrochemical Co., ltd., trade name MMC-2. The catalyst contains ultrastable Y-type zeolite and ZSP zeolite with the average pore diameter less than 0.7 nanometer, and the main physicochemical properties of the catalyst are shown in Table 1 after the catalyst is hydrothermally aged for 17 hours at 800 ℃ before use by saturated steam. The properties of the heavy feed oil and the light feed oil used in examples and comparative examples are shown in tables 2 and 3.

TABLE 1 physicochemical Properties of the catalyst

TABLE 2

TABLE 3

Example 1

This example is intended to illustrate the process for producing propylene of the present invention, wherein the mass ratio of processed heavy feed oil to light feed oil is 1:1.

the experiment was carried out using a modified medium-sized apparatus for continuous reaction-regeneration operation, the flow of which is shown in fig. 1, the riser reactor 1 of which inner diameter is 16 mm and length is 3800 mm, the first fluidized bed reactor 2 of which inner diameter is 68 mm and height is 600 mm, and the second fluidized bed reactor 3 of which inner diameter is 64 mm and height is 600 mm. The 690 ℃ high-temperature regenerated catalyst is respectively introduced into the bottoms of the riser reactor 1 and the first fluidized bed reactor 2 through the second regenerated catalyst delivery pipe 11 and the first regenerated catalyst delivery pipe 21 by the regenerator 6, and flows upwards under the action of pre-lift steam. After being mixed with atomized water vapor, the light raw oil enters the first fluidized bed reactor 2 through the light raw oil feeding nozzle 22 to contact with a hot regenerant for catalytic conversion reaction, and the reacted oil gas is settled and separated by the first settler 5 to obtain a first catalyst to be generated and first oil gas. Part of the first catalyst to be regenerated returns to the bottom of the riser reactor 1 through a catalyst to be regenerated return inclined pipe 23, and the rest of the first catalyst to be regenerated enters the regenerator 7 through a first catalyst to be regenerated delivery pipe 24 for coke burning regeneration.

The heavy raw oil is sprayed into the riser reactor 1 through the heavy raw oil feeding nozzle 12 under the atomized water vapor medium, and contacts and reacts with the catalyst (the part of the first catalyst to be regenerated and the regenerated catalyst introduced through the second regenerated catalyst conveying pipe 11) from the bottom of the riser reactor, and the reacted oil gas is introduced into the second fluidized bed reactor 3 through the outlet 13 of the riser reactor for reaction. The reaction oil is introduced into a second settler 4 for oil separation, and the reaction oil gas is introduced into a product separation system for separation into gas and liquid products.

The spent catalyst containing coke from the second fluidized bed reactor 3 enters a stripper 6, and steam generated by steam stripping is used for removing hydrocarbon products adsorbed on the spent catalyst and then enters a settler through the second fluidized bed reactor for gas-solid separation. The stripped spent catalyst enters the regenerator 7 through a second spent catalyst conveying pipe 61 and contacts with air for high-temperature scorching regeneration at 690 ℃. The regenerated catalyst is introduced into the bottom of the riser reactor 1 and the first fluidized bed reactor 2 through the second regenerated catalyst delivery pipe 11 and the first regenerated catalyst delivery pipe 21, respectively. Medium-sized devices use electrical heating to maintain the reaction-regeneration system temperature.

The main operating conditions and results are listed in table 4.

Example 2

The procedure and flow were as in example 1, with the main operating conditions and results as indicated in Table 4.

Comparative example 1

The process of example 1 was followed except that the first catalyst to be generated after the reaction of the light feedstock was not returned to the bottom of the heavy feedstock cracking riser reactor. The reaction apparatus used was the same as in example 1, and the raw materials, catalysts and main experimental steps used were the same as in example 1, except that the spent catalyst after the reaction in the first fluidized bed reactor was not returned to the bottom of the riser reactor.

The main operating conditions and results are listed in table 4.

TABLE 4

Example 3

The experiment was carried out using a modified medium-sized apparatus for continuous reaction-regeneration operation, the flow of which is shown in fig. 1, the riser reactor 1 of the medium-sized apparatus having an inner diameter of 16 mm and a length of 3800 mm, the heavy feedstock oil feed nozzle 12 being 600 mm above the light feedstock oil II nozzle (not shown); the first fluidized bed reactor 2 had an inner diameter of 68 mm and a height of 600 mm, and the second fluidized bed reactor 3 had an inner diameter of 64 mm and a height of 600 mm. The 690 ℃ high-temperature regenerated catalyst is respectively introduced into the bottoms of the riser reactor 1 and the first fluidized bed reactor 2 through the second regenerated catalyst delivery pipe 11 and the first regenerated catalyst delivery pipe 21 by the regenerator 6, and flows upwards under the action of pre-lift steam.

After being mixed with atomized water vapor, the light raw oil I enters the first fluidized bed reactor 2 through the light raw oil feeding nozzle 22 to contact with a hot regenerant for catalytic conversion reaction, and the reacted oil gas is settled and separated through the first settler 5 to obtain a first catalyst to be regenerated and first oil gas. Part of the first catalyst to be generated returns to the bottom of the riser reactor 1 through the catalyst to be generated return inclined pipe 23, and the rest part of the first catalyst to be generated enters the regenerator 7 through the first catalyst to be generated conveying pipe 24 for coke burning regeneration.

The light raw oil II is sprayed into the lower part of the riser reactor 1 through a light raw oil II nozzle (not shown) under the atomizing steam medium to contact and react with the catalyst (the part of the first catalyst to be regenerated and the regenerated catalyst introduced through the second regenerated catalyst delivery pipe 11) from the bottom of the riser reactor, the heavy raw oil is sprayed into the riser reactor 1 through a heavy raw oil feeding nozzle 12 under the atomizing steam medium to contact and react with the mixture formed by the contact and reaction of the light raw oil II and the catalyst, and the reacted oil gas is introduced into the second fluidized bed reactor 3 through an outlet 13 of the riser reactor to react. The reaction oil is introduced into a second precipitator 4 for oil separation, and the reaction oil gas is introduced into a product separation system for separation into gas and liquid products.

The spent catalyst containing coke from the second fluidized bed reactor 3 enters a stripper 6, and steam of stripping steam is used for stripping hydrocarbon products adsorbed on the spent catalyst and then enters a settler through the second fluidized bed reactor for gas-solid separation. The stripped spent catalyst enters the regenerator 7 through a second spent catalyst conveying pipe 61 and contacts with air to be burnt and regenerated at a high temperature of 690 ℃. The regenerated catalyst is introduced into the bottom of the riser reactor 1 and the first fluidized bed reactor 2 through the second regenerated catalyst delivery pipe 11 and the first regenerated catalyst delivery pipe 21, respectively. The medium-sized devices use electrical heating to maintain the temperature of the reaction-regeneration system.

The main operating conditions and results are listed in table 5.

Example 4

The procedure and flow of example 3 were followed, with the main operating conditions and results listed in Table 5.

TABLE 5

It can be seen from the above data of the examples that the propylene yield can be significantly improved while the dry gas and coke yields are reduced by using the method for producing propylene provided by the present invention.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A process for producing propylene, the process comprising:

(1) The method comprises the steps of contacting light raw oil with a first regenerated catalyst in a first fluidized bed reactor to perform a first catalytic cracking reaction to obtain a first oil mixture, separating the first oil mixture to obtain a first oil gas and a first to-be-generated catalyst, and dividing the first to-be-generated catalyst into a first to-be-generated catalyst A and a first to-be-generated catalyst B; the operating conditions of the first fluidized bed reactor include: the reaction temperature is 610-670 ℃, and the weight hourly space velocity is 2-8h ^-1 ；

(2) Contacting heavy raw oil with a first catalyst A to be regenerated and a second regenerated catalyst in a riser reactor to perform a second catalytic cracking reaction to obtain a second oil mixture, wherein the mass ratio of the first catalyst A to the second regenerated catalyst is (0.1-1): 1;

(3) Introducing the second oil mixture into a second fluidized bed reactor to carry out a third catalytic cracking reaction to obtain a third oil mixture; separating the third oil agent mixture to obtain third oil gas and a third spent catalyst, introducing the first spent catalyst B and the third spent catalyst into a stripper for steam stripping, regenerating the stripped spent catalyst, and introducing the obtained regenerated catalyst into the first fluidized bed reactor and the riser reactor for recycling; the operating conditions of the second fluidized bed reactor include: the reaction temperature is 540-580 ℃, andthe hourly space velocity is 2-8h ^-1 ；

The mass ratio of the heavy raw oil to the light raw oil is 0.5-2:1;

the operating conditions of the riser reactor include: the agent-oil ratio is 5-25, the oil-gas retention time is 0.5-5s, and the outlet temperature is 550-590 ℃.

2. The process according to claim 1, wherein the mass ratio of the first to-be-regenerated catalyst a to the second regenerated catalyst is from 0.2 to 0.5:1.

3. the process of claim 1 wherein the operating conditions of the riser reactor comprise: the agent-oil ratio is 8-15, the oil-gas retention time is 1-3s, and the outlet temperature is 560-580 ℃.

4. The method of any of claims 1-3, wherein the method further comprises: dividing light raw oil into a light raw oil I and a light raw oil II, and introducing the light raw oil II into a riser reactor; wherein the mass ratio of the total amount of the light raw oil II and the heavy raw oil to the light raw oil I is 4-5:1.

5. the method according to claim 4, wherein the light raw oil II is contacted with the first catalyst A to be regenerated and the second regenerated catalyst to carry out catalytic cracking reaction to obtain a mixture, and then the heavy raw oil is introduced into the riser reactor to be contacted with the mixture to carry out reaction to obtain the second oil mixture.

6. The method of claim 5, wherein,

and introducing the heavy raw oil 0.1-2 seconds after the light raw oil II is introduced into the riser reactor.

7. A process according to any one of claims 1 to 3, wherein the temperature of the regeneration is 660 to 720 ℃.

8. The process of any of claims 1-3, wherein the heavy feedstock oil is selected from at least one of vacuum gas oil, atmospheric gas oil, coker gas oil, deasphalted oil, vacuum residue, atmospheric residue, hydrogenated heavy oil, oil sand oil, shale oil, synthetic oil, animal and vegetable fats and oils, and coal liquefied oil;

the light raw oil is at least one selected from catalytic cracking C4 hydrocarbon fraction, catalytic cracking light gasoline fraction, straight-run naphtha and straight-run diesel.

9. The method according to any one of claims 1 to 3, wherein the first regenerated catalyst and the second regenerated catalyst contain a molecular sieve selected from at least one of Y zeolite, ZSM-5 zeolite, high-silica zeolite having a pentasil structure, and beta zeolite.