CN115895709A - Method for preparing propylene and gasoline with low olefin content - Google Patents

Abstract

The present disclosure relates to a process for producing propylene and low olefin content gasoline, the process comprising: the hydrocarbon oil raw material is contacted with a catalytic cracking catalyst in a first reactor to carry out catalytic cracking reaction, so as to obtain a spent catalyst and a reaction product; carrying out first separation on the reaction product to obtain a C4 fraction, light gasoline and heavy gasoline; introducing the C4 fraction and the light gasoline into a second reactor to contact with a polymerization catalyst for catalytic polymerization reaction, and performing second separation on the obtained polymerization product to obtain light polymerization oil and overlapped polymerization oil; returning at least a portion of the refolded oil to the first reactor; and mixing the light superimposed oil with the heavy gasoline after optional hydrotreatment to obtain the product gasoline. By adopting the method disclosed by the invention, the olefin content of the catalytic cracking gasoline can be reduced, the octane number of the gasoline and the yield of the gasoline can be improved, and meanwhile, the graded efficient utilization of the superimposed oil can be realized.

Description

A method for preparing propylene and low olefin content gasoline

Technical Field

The present invention relates to the field of petrochemical industry, and in particular, to a method for preparing propylene and gasoline with low olefin content.

Background Art

In recent years, the environmental pollution problem caused by automobile exhaust emissions has become increasingly serious, so the requirements for automotive gasoline have become more stringent. The current automotive gasoline standard GB17930-2016 stipulates that the upper limit of the volume fraction of olefins in the VIA stage and VIB stage of automotive gasoline is 18% and 15% respectively. At present, the mass fraction of catalytic cracking gasoline in my country's gasoline pool is about 60% to 70%. The olefin content of catalytic cracking gasoline is high, and its volume fraction is generally higher than 30%. Olefins are the main contributors to the octane number of catalytic cracking gasoline, especially small molecular olefins such as C5 and C6. How to reduce the olefin content while increasing the octane number of gasoline is a challenge facing the catalytic cracking process.

CN1069054A discloses a catalytic cracking method using two risers to process light hydrocarbons and heavy hydrocarbons respectively. In the first riser reactor, light hydrocarbons react with hot catalysts at 600-700°C, catalyst-oil weight ratio of 10-40, residence time of 2-20 seconds, and catalyst carbon content of 0.1-0.4 weight % to achieve the purpose of increasing olefin production and improving gasoline octane number; then the catalyst enters the conventional riser to participate in the catalytic cracking reaction of heavy hydrocarbons. This method has limited ability to improve octane number and is not conducive to reducing gasoline olefin content.

CN102952577A discloses a catalytic conversion method for improving propylene yield. High-quality catalytic cracking feedstock oil and thermally regenerated catalyst are contacted and reacted in the first reaction zone of the reactor. The generated oil gas and carbon-containing catalyst are selectively hydrogenated and isomerized in the second reaction zone. The separated C4 fraction and/or light gasoline fraction are injected into the reactor for further reaction. The method can increase the propylene yield by 1.3 percentage points and improve the product distribution.

CN103571536A discloses a device and method for producing clean gasoline and increasing propylene production by catalytic cracking and hydrogenation, wherein a gasoline fractionation tower is added to the top of a catalytic cracking fractionation tower to separate crude gasoline into light and heavy fractions, and the heavy gasoline enters a hydrogenation unit for refining; a portion of the light gasoline enters an absorption stabilization system to obtain stabilized gasoline, and the other portion directly returns to the lower part of the catalytic cracking riser reactor to be cracked under harsh reaction conditions to increase propylene production; finally, the stabilized light gasoline and the modified heavy gasoline are blended to obtain a clean gasoline product. The method efficiently modifies gasoline and increases propylene production.

The existing technology mainly reduces the olefin content of gasoline by recycling light gasoline and increases the production of propylene, but this method causes a large loss of gasoline octane number.

In addition, etherification of light gasoline is also an important way to increase the octane number of gasoline. However, the E10 ethanol gasoline standard GB18351-2017 implemented in September 2017 clearly stipulates that "the volume fraction of ethanol is 10% ± 2%", and oxygen-containing compounds such as MTBE and etherified light gasoline cannot be artificially added to the gasoline pool.

Summary of the invention

The purpose of the present invention is to solve the problem in the prior art that the octane number of gasoline is greatly lost when recycling light gasoline.

In order to achieve the above-mentioned object, the present disclosure provides a method for preparing gasoline with low olefin content of propylene, which comprises: contacting a hydrocarbon oil feedstock with a catalytic cracking catalyst in a first reactor to carry out a catalytic cracking reaction to obtain a spent catalyst and a reaction product; subjecting the reaction product to a first separation to obtain a C4 fraction, light gasoline and heavy gasoline; introducing the C4 fraction and the light gasoline into a second reactor to contact with a superimposed catalyst to carry out a catalytic superposition reaction, subjecting the obtained superimposed product to a second separation to obtain a light superimposed oil and a superimposed oil; returning at least a part of the superimposed oil to the first reactor; and mixing the light superimposed oil with the heavy gasoline after optional hydrogenation treatment to obtain a product gasoline.

Optionally, the conditions of the catalytic cracking reaction include: a reaction temperature of 450-580°C, an oil-gas residence time of 0.5-5 seconds, a reaction pressure of 0.1-1MPa, and a catalyst-oil weight ratio of 4-50; the first reactor is selected from one or a combination of two or more of a riser reactor, a fluidized bed reactor, an upward conveying line and a downward conveying line, and the combination includes series and/or parallel connection.

Optionally, the first reactor is a riser reactor; preferably, the riser reactor is a constant diameter riser reactor or a variable diameter riser reactor; according to the flow direction of the catalyst, the catalytic cracking catalyst first contacts the superimposed oil and then contacts the hydrocarbon oil feedstock.

Optionally, the catalytic cracking catalyst comprises natural minerals, oxides and zeolites; based on the total weight of the catalytic cracking catalyst, the content of the natural minerals is 15-65% by weight, the content of the oxides is 10-30% by weight, and the content of the zeolite is 25-75% by weight; wherein the natural ore is selected from one or more of kaolin, montmorillonite, diatomaceous earth, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite; the oxide is an inorganic oxide, preferably one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silica-aluminum; the zeolite is selected from one or more of Y zeolite, ZSM-5 zeolite and Beta zeolite.

Optionally, the method further comprises: injecting a pre-lifting medium into the bottom of the first reactor; the pre-lifting medium is selected from one or more of water vapor, dry gas and nitrogen, and the weight ratio of the pre-lifting medium to the hydrocarbon oil feedstock is 0.01-2, preferably 0.05-1;

Optionally, the method further comprises preheating the hydrocarbon oil feedstock to 180-400° C. before entering the first reactor.

Optionally, the cutting temperature of the light gasoline and the heavy gasoline is 50-80°C, preferably 60-70°C.

Optionally, the reaction conditions of the catalytic superposition reaction include: reaction temperature of 50-200°C, preferably 60-160°C; reaction pressure of 0.1-5MPa, preferably 0.5-3MPa; liquid volume space velocity of 0.5-10h ^-1 , preferably 0.8-5h ^-1 ; the second reactor is selected from one of a fixed bed reactor, a stirred tank reactor and a tower reactor.

Optionally, the stacked catalyst is selected from one or more of solid phosphoric acid, ion exchange resin and zeolite molecular sieve, preferably ion exchange resin.

Optionally, the cutting temperature of the light superimposed oil and the overlapping oil is 110-150°C, preferably 120-130°C; the total content of trimethylpentene and trimethylhexene in the light superimposed oil is more than 80 volume%, preferably more than 85 volume%; the content of C12 and higher carbon number olefins in the overlapping oil is more than 70 volume%, preferably more than 75 volume%.

Optionally, the conditions of the hydroprocessing include: reaction temperature of 50-180°C, reaction pressure of 1-3MPa, volume space velocity of 0.2-10h ^-1 ; the hydrogenation catalyst is selected from one or more of supported cobalt-molybdenum catalysts and/or supported nickel-based catalysts, preferably supported nickel-based catalysts.

Optionally, the method further comprises: after introducing the catalyst to be regenerated into a regenerator for regeneration, returning the obtained regenerated catalyst to the first reactor.

Optionally, the hydrocarbon oil feedstock is selected from one or more of vacuum gas oil, vacuum residue oil, atmospheric gas oil, atmospheric residue oil, coker gas oil, deasphalted oil, hydrorefined oil, hydrocracking tail oil, crude oil, coal liquefaction oil, shale oil and oil sands oil.

Through the above technical solution, the method disclosed in the present invention is adopted to perform a superposition treatment on the C4 fraction obtained by the catalytic cracking reaction and the light gasoline fraction, which can reduce the olefin content of the catalytic cracking gasoline, improve the octane number and gasoline yield of the gasoline, and obtain a high-octane gasoline product. In addition, the superimposed oil is fractionated into a light fraction and a heavy fraction, which can achieve graded and efficient utilization of the superimposed oil.

Other features and advantages of the present disclosure will be described in detail in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

FIG1 is a schematic diagram of a specific embodiment of the process for preparing propylene and low-olefin content gasoline provided by the present disclosure.

Description of Reference Numerals

1. Riser reactor; 2. Regenerator; 3. Separation device; 4. Composite reactor; 5. Fractionation tower; 6. Hydroprocessor; 7. Riser reactor pre-lifting medium; 8. Composite oil; 9. Hydrocarbon oil feedstock; 10. Cyclone separator; 11. Stripping section; 12. Catalyst to be regenerated; 13. Regenerated catalyst; 14. Reaction oil and gas; 15. C4 fraction; 16. Light gasoline; 17. Composite product; 18. Light composite oil; 19. Light composite oil after hydrotreatment; 20. Heavy gasoline.

DETAILED DESCRIPTION

The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

The present disclosure provides a method for preparing gasoline with low olefin content and propylene, which comprises: contacting a hydrocarbon oil feedstock with a catalytic cracking catalyst in a first reactor to carry out a catalytic cracking reaction to obtain a spent catalyst and a reaction product; subjecting the reaction product to a first separation to obtain a C4 fraction, light gasoline and heavy gasoline; introducing the C4 fraction and the light gasoline into a second reactor to contact with a superimposed catalyst to carry out a catalytic superposition reaction, subjecting the obtained superimposed product to a second separation to obtain a light superimposed oil and a superimposed oil; returning at least a portion of the superimposed oil to the first reactor; and mixing the light superimposed oil with the heavy gasoline after optional hydrogenation treatment to obtain a product gasoline.

By the above technical scheme, the method disclosed in the present invention is adopted to overlap the C4 fraction with light gasoline, which can reduce the olefin content of catalytic cracking gasoline and improve the octane number and gasoline yield of gasoline. Catalytic cracking light gasoline is rich in C5 and C6 olefins, which are key components for increasing propylene production and improving the octane number of gasoline. Compared with small molecule olefins, polymethyl-substituted isomeric hydrocarbons, such as 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, usually have higher octane numbers. The inventors of the present invention found in the research process that in the C4 olefin overlap process, adding small molecule olefins, such as C5 olefins, helps to improve the selectivity of trimethylpentene and trimethylhexene in the overlap product, thereby improving the octane number of gasoline; the overlap oil is fractionated into light and heavy fractions, and the light overlap oil mainly contains trimethylpentene and trimethylhexene, which can be used as a high-octane gasoline blending component, and the overlap oil is mainly C12 and higher carbon number olefins, which are suitable for cracking to increase the production of gasoline and propylene. The method disclosed in the present invention fractionates the superimposed oil into light fractions and heavy fractions, and can achieve graded and efficient utilization of the superimposed oil.

In one embodiment, the method disclosed herein can be applied to the treatment of a variety of hydrocarbon oil feedstocks with good treatment effects. For example, the hydrocarbon oil feedstock can be selected from one or more of vacuum gas oil, vacuum residue oil, atmospheric gas oil, atmospheric residue oil, coker gas oil, deasphalted oil, hydrorefined oil, hydrocracking tail oil, crude oil, coal liquefaction oil, shale oil and oil sands oil, among which the treatment effects on vacuum gas oil, atmospheric residue oil and hydrocracking tail oil are better.

In one embodiment, the conditions of the catalytic cracking reaction include: reaction temperature of 450-580°C, preferably 490-540°C; oil and gas residence time of 0.5-5 seconds, preferably 1-5 seconds; reaction pressure of 0.1-1MPa, preferably 0.1-0.3MPa; catalyst-oil weight ratio of 4-50, preferably 5-20.

In this embodiment, under the above catalytic cracking reaction conditions, the cracking effect of the hydrocarbon oil feedstock is good. In order to further enhance the effect of the cracking reaction, the conditions for the catalytic cracking reaction are optimized.

In one embodiment, the first reactor is selected from a riser reactor, a fluidized bed reactor, an upward conveying line, and a downward conveying line, or a combination of two or more thereof, wherein the combination includes series connection and/or parallel connection.

According to a preferred embodiment of the present invention, the first reactor is a riser reactor; preferably, the riser reactor is a constant diameter riser reactor or a variable diameter riser reactor.

According to one embodiment of the present invention, the first reactor includes multiple reaction positions, and part and/or all of the overlapping oil can be introduced into the first reactor at one feed position, or the overlapping oil can be introduced into the reactor in the same or different proportions at at least two different feed positions.

Further, according to a preferred embodiment of the present invention, the feeding position of the superimposed oil is located at the lower part of the first reactor.

In an embodiment where the first reactor is a riser reactor, it is further preferred that, according to the flow direction of the catalyst, the catalytic cracking catalyst first contacts the superimposed oil and then contacts the hydrocarbon oil feedstock, so as to improve the activity of the catalytic cracking catalyst and the degree of matching between the properties of the superimposed oil and the hydrocarbon oil feedstock, thereby further improving the product distribution and avoiding the occurrence of side reactions.

In this embodiment, when the reactor is a riser reactor, the reaction temperature refers to the outlet temperature of the riser reactor or a reaction zone of the riser reactor; and the reaction pressure refers to the gauge pressure.

In one embodiment, the catalytic cracking catalyst comprises natural minerals, oxides and zeolites; based on the total weight of the catalytic cracking catalyst, the content of the natural minerals is 15-65% by weight, the content of the oxides is 10-30% by weight, and the content of the zeolite is 25-75% by weight; wherein the natural ore is selected from one or more of kaolin, montmorillonite, diatomaceous earth, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite; the oxide is an inorganic oxide, preferably one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silica-aluminum; the zeolite is selected from one or more of Y zeolite, ZSM-5 zeolite and Beta zeolite.

In the above embodiment, the use of the above preferred catalytic cracking catalyst can further enhance the activity of the catalytic cracking catalyst and improve the product distribution.

In one embodiment, the method of the present disclosure further includes the step of regenerating the catalyst to be regenerated obtained by the reaction. The catalyst regeneration method can be implemented according to conventional methods in the art, for example: introducing the catalyst to be regenerated into a regenerator, introducing an oxygen-containing gas (such as air) from the bottom of the regenerator, the catalyst to be regenerated is contacted with oxygen and charred and regenerated, the generated flue gas is separated into gas and solid by a cyclone separator of the regenerator, and enters a subsequent energy recovery system, and the regenerated catalyst is returned to the first reactor for continued use. The regeneration conditions of the catalyst to be regenerated can be: the regeneration temperature is 600-750°C, preferably 640-720°C; the gas superficial linear velocity is 0.2-3 m/s, preferably 0.4-2.5 m/s; the average residence time of the catalyst to be regenerated is 0.5-3 minutes, preferably 0.6-2.6 minutes.

In one embodiment, the method further comprises: injecting a pre-lifting medium into the bottom of the first reactor; the pre-lifting medium is selected from one or more of water vapor, dry gas and nitrogen, and the weight ratio of the pre-lifting medium to the hydrocarbon oil feedstock is 0.01-2, preferably 0.05-1.

In one embodiment, the method further comprises preheating the hydrocarbon oil feedstock to 180-400° C. before entering the first reactor.

In this embodiment, the hydrocarbon oil feedstock is preheated and then enters the first reactor. When entering the first reactor, the temperature can be quickly raised to the reaction temperature, so that the hydrocarbon oil feedstock can fully react in the first reactor, reducing the generation of unreacted hydrocarbon oil feedstock or reaction by-products.

In one embodiment, the first separation is carried out in a fractionation tower; the cutting temperature of the light gasoline and the heavy gasoline is 50-80°C, preferably 60-70°C. Wherein, when the final boiling point of the light gasoline is lower than 70°C, the volume content of C5 olefins in the light gasoline is above 80%. The above preferred cutting temperature helps to further improve the selectivity of trimethylpentene in the superposition product of the catalytic superposition reaction of the light gasoline fraction and the C4 fraction, improve the octane number of gasoline, and is conducive to the generation of high carbon number superposition products that are easy to crack into propylene.

In one embodiment, the reaction conditions of the catalytic superposition reaction include: reaction temperature of 50-200°C, preferably 60-160°C; reaction pressure of 0.1-5MPa, preferably 0.5-3MPa; liquid volume space velocity of 0.5-10h ^-1 , preferably 0.8-5h ^-1 ; the second reactor is selected from one of a fixed bed reactor, a stirred tank reactor and a tower reactor, preferably a fixed bed reactor.

Optionally, the second reactor can be operated batchwise or continuously, preferably continuously.

In one embodiment, the stacked catalyst is selected from one or more of solid phosphoric acid, ion exchange resin and zeolite molecular sieve, preferably ion exchange resin. In the above embodiment, the ion exchange resin is obtained by cross-linking styrene and divinylbenzene and then introducing sulfonic acid groups. Such resins can be synthesized according to existing methods or purchased from the market, such as one or more of Amberlyst15, Amberlyst35 strong acid cation exchange resins and Nafion perfluorosulfonic acid new resin catalysts.

In one embodiment, the second separation is carried out in a fractionation tower, and the cutting temperature between the light superposed oil and the superposed oil is 110-150°C, preferably 120-130°C.

In one embodiment, the total content of trimethylpentene and trimethylhexene in the light superimposed oil is greater than 80 volume %, preferably greater than 85 volume %; the content of C12 and higher carbon number olefins in the superimposed oil is greater than 70 volume %, preferably greater than 75 volume %.

According to the present disclosure, the light superimposed oil may or may not be hydrotreated before being mixed with heavy gasoline. Under the premise of meeting the olefin content requirements of the blended gasoline, the light superimposed oil may not be hydrotreated. In this embodiment, the olefin content of the product oil prepared by the present disclosure is less than 20 volume %. In order to reduce the olefin content of gasoline, the light superimposed oil is preferably hydrotreated under mild conditions to convert isoolefins into isoparaffins.

In one embodiment, the hydroprocessing is carried out in a fixed bed reactor; the conditions of the hydroprocessing include: a reaction temperature of 50-180°C, preferably 60-120°C, a reaction pressure of 1-3MPa, preferably 1.2-2.5MPa, and a volume space velocity of 0.2-10h ^-1 , preferably 0.5-8h ^-1 ; the hydrogenation catalyst is selected from one or more of a supported cobalt-molybdenum catalyst and a supported nickel-based catalyst, preferably a supported nickel-based catalyst, which has better olefin hydrogenation saturation activity, good thermal stability and high mechanical strength.

The present invention will be further described in the following examples, but the present invention is not limited thereto.

The weight ratio of atmospheric residue to hydrocracking tail oil in the heavy oil feedstock used in the examples and comparative examples is 3, and the properties are listed in Table 1.

The catalytic cracking catalyst used was a cracking catalyst with a trade name of CDOS produced by the Qilu Branch of Sinopec Catalyst Co., Ltd. The properties are listed in Table 2.

The RON octane number of gasoline is determined according to the method of GB/T 5487.

Table 1 Properties of heavy oil feedstock

Table 2 Properties of catalytic cracking catalysts

Example 1

The composite catalyst is Amberlyst 35 resin (commercially available), and the light composite oil hydrotreating catalyst adopts a hydrogenation catalyst with a trade name of RS-40 produced by the Changling Branch of Sinopec Catalyst Co., Ltd.

As shown in FIG. 1 , a pre-lifting medium 7 (having a weight ratio of 0.06 to the hydrocarbon oil feedstock) enters the bottom of the riser reactor 1 through a pipeline, and a high-temperature regenerated catalyst 13 from the regenerator accelerates upward under the action of the pre-lifting medium. The atomized superimposed oil 8 is introduced into the riser reactor 1, where it contacts and reacts with the high-temperature regenerated catalyst 13. The preheated hydrocarbon oil feedstock (heavy oil feedstock) 9 is injected into the riser reactor 1 together with the atomized medium (steam), and a catalytic cracking reaction occurs on the hot catalytic cracking catalyst. The operating conditions are: reaction temperature of 520° C., reaction pressure of 0.14 MPa, catalyst-oil weight ratio of 6, reaction time of 3 s, and the generated reaction product and the catalyst to be regenerated with carbon enter the cyclone separator 10 to separate the catalyst to be regenerated 12 from the reaction oil gas 14. The catalyst to be regenerated is stripped in the stripping section 11, and the stripped catalyst 12 enters the regenerator 2 through the conveying inclined pipe for charring and regeneration, and then returns to the riser reactor 1. The reaction oil gas 14 enters the subsequent separation device 3. After separation operations such as distillation and absorption, the C4 fraction 15 and the light gasoline 16 with a final boiling point not higher than 70°C are introduced into the superposition reactor 4. Under the action of Amberlyst35 resin catalyst, a catalytic superposition reaction is carried out. The operating conditions are: reaction temperature is 80°C, reaction pressure is 1.0MPa, liquid volume space velocity is 2h ^-1 , and a fixed bed reactor is used. The superposition product 17 is introduced into the fractionation tower 5. The light superposition oil 18 with a final boiling point not higher than 120°C is distilled from the top of the fractionation tower and then enters the hydroprocessor 6. Under the action of hydrogen and RS-40 hydrogenation catalyst, isoolefins are converted into isoparaffins. The operating conditions of the hydrogenation treatment are: reaction temperature is 70°C, reaction pressure is 1.6MPa, volume space velocity is 2h ^-1 , and a fixed bed reactor is used. The light superposition oil 19 after hydrogenation treatment is mixed with the heavy gasoline 20 from the separation device 3 to obtain high-octane gasoline. The overlapped oil 8 is returned to the riser reactor 1. The operating conditions and product distribution are listed in Table 3.

Example 2

The method and apparatus for preparing propylene and low olefin content gasoline are the same as those in Example 1, except that the light superimposed oil is not hydrotreated but directly mixed with heavy gasoline. The operating conditions and product distribution are listed in Table 3.

Example 3

The method and apparatus for preparing propylene and low olefin content gasoline are the same as those in Example 1, except that the superposition reaction conditions are: reaction temperature is 80°C, reaction pressure is 1.2 MPa, and liquid volume space velocity is 1.5 h ^-1 . The operating conditions and product distribution are listed in Table 3.

Example 4

The method and apparatus for preparing propylene and low olefin content gasoline are the same as those in Example 1, except that the composite catalyst uses solid phosphoric acid (commercially available). The operating conditions and product distribution are listed in Table 3.

Comparative Example 1

The method and apparatus for preparing propylene and low olefin content gasoline are the same as those in Example 1, except that in this comparative example, the C4 fraction and light gasoline are not introduced into the stacked reactor, but are mixed with heavy gasoline and then withdrawn as products. The operating conditions and product distribution are listed in Table 3.

Comparative Example 2

The method and apparatus for preparing propylene and low olefin content gasoline are the same as those in Example 1, except that in this comparative example, the light gasoline does not enter the superposition reactor, and only the C4 fraction is introduced into the superposition reactor for superposition reaction, and the light superposition oil after hydrogenation is mixed with the light gasoline and heavy gasoline from the separation device to obtain a gasoline product. The operating conditions and product distribution are listed in Table 3.

Table 3 Operating conditions and product distribution

As can be seen from Table 3, by comparing the data in Examples 1-4 with Comparative Examples 1-2, it can be seen that, compared with the comparative examples, by using the method provided by the present invention, the gasoline yield increases by 2.1-4.5 percentage points, the propylene yield increases by 0.4-1.9 percentage points, the gasoline olefin content decreases by 7.3-17.8 percentage points, and the gasoline research octane number increases by 2.1-3.7 units. By using the method provided by the present invention, the content of trimethylpentene and trimethylhexene in light superimposed oil can be significantly increased, while helping to increase the propylene yield, obtain a high-octane gasoline component with a low olefin content, and the gasoline yield is increased. By comparing the data in Example 1 with that in Example 2, it can be seen that hydrotreating can further reduce the olefin content in the product oil. By comparing the data in Example 1 with that in Example 4, it can be seen that using ion exchange resin as a superimposed reaction catalyst can further optimize the composition of superimposed gasoline, and the effect of preparing propylene and low olefin content gasoline is better.

The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims (12)

1. A process for producing propylene and a gasoline having a low olefin content, the process comprising:

contacting a hydrocarbon oil raw material with a catalytic cracking catalyst in a first reactor to carry out catalytic cracking reaction to obtain a spent catalyst and a reaction product; carrying out first separation on the reaction product to obtain a C4 fraction, light gasoline and heavy gasoline;

introducing the C4 fraction and the light gasoline into a second reactor to contact with a polymerization catalyst for catalytic polymerization reaction, and performing second separation on the obtained polymerization product to obtain light polymerization oil and overlapped polymerization oil;

returning at least a portion of the refolded oil to the first reactor; and mixing the light superimposed oil with the heavy gasoline after optional hydrotreatment to obtain the product gasoline.

2. The process according to claim 1, characterized in that the conditions of the catalytic cracking reaction comprise: the reaction temperature is 450-580 ℃, the oil gas residence time is 0.5-5 seconds, the reaction pressure is 0.1-1MPa, and the weight ratio of the solvent to the oil is 4-50;

the first reactor is selected from one or more of a riser reactor, a fluidized bed reactor, an ascending conveyor line and a descending conveyor line, and the combination comprises series connection and/or parallel connection.

3. The method of claim 2, wherein the first reactor is a riser reactor; preferably, the riser reactor is an equal-diameter riser reactor or a reducing riser reactor;

according to the flowing direction of the catalyst, the catalytic cracking catalyst is firstly contacted with the heavy superposed oil and then contacted with the hydrocarbon oil raw material.

4. The process of claim 1 or 2, wherein the catalytic cracking catalyst comprises natural minerals, oxides, and zeolites; based on the total weight of the catalytic cracking catalyst, the content of the natural mineral is 15-65 wt%, the content of the oxide is 10-30 wt%, and the content of the zeolite is 25-75 wt%;

wherein the natural ore is selected from one or more of kaolin, montmorillonite, diatomite, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite;

the oxide is an inorganic oxide, preferably one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silica-alumina;

the zeolite is selected from one or more of Y zeolite, ZSM-5 zeolite and Beta zeolite.

5. The method of claim 1, further comprising: injecting a pre-lifting medium at the bottom of the first reactor; the pre-lifting medium is selected from one or more of steam, dry gas and nitrogen, and the weight ratio of the pre-lifting medium to the hydrocarbon oil raw material is 0.01-2, preferably 0.05-1;

optionally, the process further comprises preheating the hydrocarbon oil feedstock to 180-400 ℃ prior to entering the first reactor.

6. The method according to claim 1, characterized in that the cutting temperature of the light gasoline and the heavy gasoline is 50-80 ℃, preferably 60-70 ℃.

7. The method of claim 1, wherein the reaction conditions of the catalytic polymerization reaction include: the reaction temperature is 50-200 ℃, preferably 60-160 ℃; the reaction pressure is 0.1-5MPa, preferably 0.5-3MPa; the liquid volume space velocity is 0.5-10h ^-1 Preferably 0.8 to 5 hours ^-1 ；

The second reactor is selected from one of a fixed bed reactor, a stirred tank reactor and a tower reactor.

8. The method according to claim 1, wherein the polymerization catalyst is selected from one or more of solid phosphoric acid, ion exchange resin and zeolite molecular sieve, preferably ion exchange resin.

9. The method according to claim 1, characterized in that the cutting temperature of the light laminating oil and the heavy laminating oil is 110-150 ℃, preferably 120-130 ℃;

the total content of trimethylpentene and trimethylhexene in the light superimposed oil is more than 80 volume percent, and preferably more than 85 volume percent;

the content of C12 and higher olefins in the heavy overlapping oil is 70 vol% or more, preferably 75 vol% or more.

10. The method of claim 1, wherein the hydrotreating conditions comprise: the reaction temperature is 50-180 ℃, the reaction pressure is 1-3MPa, and the volume space velocity is 0.2-10h ^-1 ；

The hydrogenation catalyst is selected from supported cobalt molybdenum catalyst and/or supported nickel-based catalyst, preferably supported nickel-based catalyst.

11. The method of claim 1, further comprising: introducing the spent catalyst into a regenerator for regeneration, and returning the obtained regenerated catalyst to the first reactor.

12. The process of claim 1, wherein the hydrocarbon oil feedstock is selected from one or more of vacuum gas oil, vacuum residuum, atmospheric gas oil, atmospheric residuum, coker gas oil, deasphalted oil, hydrofinished oil, hydrocracked tail oil, crude oil, coal liquefied oil, shale oil, and oil sand oil.

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