CN109554193B

CN109554193B - Catalytic cracking method for increasing production of low-olefin and high-octane gasoline

Info

Publication number: CN109554193B
Application number: CN201710883617.6A
Authority: CN
Inventors: 龚剑洪; 唐津莲
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: 2017-09-26
Filing date: 2017-09-26
Publication date: 2021-02-09
Anticipated expiration: 2037-09-26
Also published as: CN109554193A

Abstract

The invention relates to a catalytic cracking method for increasing the yield of low-olefin and high-octane gasoline, which comprises the following steps: spraying heavy raw oil into a riser reactor from a first nozzle to perform catalytic cracking reaction to obtain a catalytic cracking reaction product and a spent catalyst; separating the catalytic cracking reaction products to obtain at least catalytic cracking gasoline and catalytic cracking light cycle oil, and cutting the obtained catalytic cracking gasoline to obtain light gasoline fraction, medium gasoline fraction and heavy gasoline fraction; carrying out hydrotreating on the obtained catalytic cracking light cycle oil to obtain hydrogenated diesel oil; mixing part of the light gasoline fraction with at least part of hydrogenated diesel oil to obtain a mixed fraction; and respectively injecting the mixed fraction and part of the medium gasoline fraction into the riser reactor from a second nozzle and a third nozzle to perform the catalytic cracking reaction. The method can produce catalytic cracking gasoline in a large amount, reduce the olefin content of the catalytic cracking gasoline and improve the octane number of the catalytic cracking gasoline.

Description

Catalytic cracking method for increasing production of low-olefin and high-octane gasoline

Technical Field

The invention relates to a catalytic cracking method for increasing the yield of low-olefin and high-octane gasoline.

Background

With the development of crude oil heaviness and the rapid increase of the market demand for light oil products, the catalytic cracking technology for heavy oil heaviness is rapidly developed in China. However, one must face the fact that catalytically cracked diesel (or "light cycle oil") has been relatively poor in quality, high in density, high in aromatics content, low in cetane number, and even by diesel hydro-upgrading technology, it has been difficult to meet increasingly stringent diesel specifications. While at the same time the economy has increased resulting in a structural excess of diesel. On the other hand, in the domestic market, more and more private cars using gasoline as fuel are used, and the demand for high-octane gasoline rises. However, with the stricter environmental regulations, the standards of finished gasoline are more stringent, and the requirement for gasoline olefin is further reduced, namely less than 15% by volume. Therefore, for oil refining enterprises, the diesel-steam ratio needs to be greatly reduced; there is a need for a catalytic cracking unit for an enterprise that produces clean, low olefin, high octane gasoline with little or no light cycle oil.

US patent US4585545 discloses a catalytic conversion method for producing gasoline rich in monocyclic aromatic hydrocarbons by hydrotreating a catalytic cracked light cycle oil whole fraction and subjecting the obtained hydrogenated diesel oil to catalytic cracking.

Chinese patent CN1422327A discloses a method for modifying catalytic cracking light cycle oil, which is to deeply hydrogenate light cycle oil produced by a first catalytic cracking unit using heavy oil as a raw material, and then feed the obtained hydrogenated cycle oil into a second catalytic cracking unit. Based on this process, the patent emphasizes that the catalyst in the second catalytic cracking unit requires 50-95% shape selective zeolite and 5-50% large pore zeolite with a pore size greater than or equal to about 0.7nm to selectively increase light olefin yield.

Chinese patent CN1466619A discloses a conversion method of catalytic cracking light cycle oil, which is to divide a catalytic cracking riser reactor into an upstream reaction zone and a downstream reaction zone, wherein heavy oil is injected into the downstream reaction zone, and hydrogenated cycle oil obtained by hydrotreating the catalytic cracking product light cycle oil is injected into the upstream reaction zone. On the basis of the method, the feed of the upstream zone in the method is added with naphtha besides the hydrogenated circulating oil.

From the above published literature, it can be found that one of the important routes for processing catalytically cracked light cycle oil is to subject it to hydrotreating followed by catalytic cracking, and to effect conversion to gasoline. It must be noted that the light cycle oil, whether hydrogenated or not, has a small molecular size and a large bond energy compared to the large molecules of the heavy oil, and therefore how to control the operating parameters of catalytic cracking is one of the keys in the light cycle oil processing. In addition, if the light cycle oil is hydrogenated, the operation control of the hydrogenation process is also one of the keys of the light cycle oil processing.

The prior publications do not solve the problem of how to maintain the ultralow olefin content of gasoline and ensure high octane number when the gasoline is increased by reducing the yield of light cycle oil to the maximum extent in the catalytic cracking process of heavy oil, namely, meet the increasingly strict clean high octane number gasoline standard.

Disclosure of Invention

The invention aims to provide a catalytic cracking method for increasing the yield of low-olefin and high-octane gasoline.

In order to achieve the above object, the present invention provides a catalytic cracking process for increasing the yields of low olefins and high octane gasoline, the process comprising: spraying heavy raw oil into a riser reactor from a first nozzle, contacting with a catalytic cracking catalyst from below, and carrying out catalytic cracking reaction from bottom to top to obtain a catalytic cracking reaction product and a spent catalyst; separating the catalytic cracking reaction products to obtain at least catalytic cracking gasoline and catalytic cracking light cycle oil, feeding the spent catalyst into a regenerator for coke burning regeneration, and feeding the obtained regenerated catalyst serving as the catalytic cracking catalyst into the riser reactor; cutting the obtained catalytic cracking gasoline to obtain light gasoline fraction, medium gasoline fraction and heavy gasoline fraction; contacting the obtained catalytic cracking light cycle oil with a hydrotreating catalyst in a hydrotreating reactor and carrying out hydrotreating to obtain hydrogenated diesel oil; mixing part of the light gasoline fraction with at least part of hydrogenated diesel oil to obtain a mixed fraction; and respectively injecting the mixed fraction and part of the medium gasoline fraction into the riser reactor from a second nozzle and a third nozzle to perform the catalytic cracking reaction.

Optionally, the method further includes: taking gasoline produced by an external catalytic cracking unit as the catalytic cracking gasoline for cutting; and/or the light cycle oil produced by an external catalytic cracking unit is used as the catalytic cracking light cycle oil for the hydrotreatment.

Optionally, the cut points of the light gasoline fraction and the medium gasoline fraction are 60-80 ℃, and the cut points of the medium gasoline fraction and the heavy gasoline fraction are 120-130 ℃.

Optionally, the medium gasoline fraction with the distillation range within 90-130 ℃ is injected into the riser reactor to carry out the catalytic cracking reaction.

Optionally, the method further includes: and sending part of the light gasoline fraction, part of the medium gasoline fraction and all of the heavy gasoline fraction to a subsequent absorption stabilizing device.

Optionally, 2-90 wt% of a medium gasoline fraction is injected into the riser reactor.

Optionally, a mixed fraction obtained by mixing 2-90 wt% of the light gasoline fraction with 10-100 wt% of hydrogenated diesel oil is injected into the riser reactor.

Optionally, the hydrotreating conditions include: the reaction temperature is 330-450 ℃, the hydrogen partial pressure is 6-25 MPa, and the volume space velocity is 0.1-2 hours^-1The volume ratio of hydrogen to oil is 1000-2000Nm³/m³。

Optionally, the hydrotreating catalyst includes a carrier and an active component loaded on the carrier, where the active component is at least one selected from a group VIB metal and a group VIII non-noble metal, and the carrier is at least one selected from alumina, silica, and amorphous silica-alumina.

Optionally, the content of bicyclic aromatic hydrocarbons in the hydrogenated diesel oil is not more than 10 wt%, and the initial boiling point of the hydrogenated diesel oil is more than 165 ℃.

Optionally, the riser reactor is an equal-diameter riser reactor with or without a bed reactor, or a reducing riser reactor with or without a bed reactor.

Optionally, the first nozzle, the second nozzle and the third nozzle are arranged at intervals from top to bottom.

Optionally, the oil gas residence time of the riser reaction section between the third nozzle and the second nozzle is 0.01 to 2 seconds, and the oil gas residence time of the riser reaction section between the second nozzle and the first nozzle is 0.01 to 3 seconds.

Optionally, the oil gas residence time of the riser reaction section between the third nozzle and the second nozzle is 0.05 to 1 second, and the oil gas residence time of the riser reaction section between the second nozzle and the first nozzle is 0.05 to 2 seconds.

Optionally, the conditions of the catalytic cracking reaction include: the reaction temperature is 480-650 ℃, the weight ratio of the catalytic cracking catalyst to the heavy raw oil is 2-100, the oil gas retention time of the heavy raw oil is 1-10 seconds, the reaction pressure is 0.15-0.4 MPa, the weight ratio of the atomized water vapor to the heavy raw oil is 0.01-0.5, the micro-reaction activity of the catalytic cracking catalyst is not lower than 55, and the micro-reaction activity is determined by a micro-reaction activity test method of an industrial equilibrium catalyst of RIPP92-90 catalytic cracking.

Optionally, the catalytic cracking catalyst comprises, on a dry basis and based on the weight of the catalytic cracking catalyst, from 10 to 50 wt% zeolite, from 5 to 90 wt% inorganic oxide, and from 0 to 70 wt% clay; the zeolite is at least one zeolite selected from the group consisting of rare earth-containing or non-rare earth-containing Y, rare earth-containing or non-rare earth-containing HY, rare earth-containing or non-rare earth-containing USY, and rare earth-containing or non-rare earth-containing Beta.

The method has the advantages that:

1. the invention cuts the catalytic cracking gasoline, returns part of the cut catalytic cracking gasoline to the riser reactor, and continues catalytic cracking reaction together with the hydrogenated diesel oil, thereby greatly reducing the diesel-gasoline ratio and increasing the yield of the clean catalytic cracking gasoline with low olefin and high octane number.

2. The invention returns the middle gasoline fraction to be injected from the lower layer of the third nozzle at the bottom of the riser, and the short contact time reaction is carried out under the harsh condition, which is beneficial to greatly improving the octane number of the fraction.

3. The light gasoline fraction rich in olefin and the hydrogenated diesel oil are mixed and returned to the riser reactor and enter from the second nozzle in the single middle layer, and the mixture is subjected to short contact time reaction under the harsh condition at the bottom of the riser, so that the hydrogen transfer reaction of the hydrogen donor and the olefin in the light gasoline fraction can be properly strengthened by utilizing the action of the hydrogenated aromatic hydrocarbon hydrogen donor in the hydrogenated diesel oil, the gasoline olefin is greatly reduced, the ring-opening cracking reaction of the hydrogenated aromatic hydrocarbon in the hydrogenated diesel oil can be strengthened, and the conversion and the gasoline selectivity of the hydrogenated diesel oil are improved.

4. By optimally controlling the residence time of oil gas between the third nozzle at the lower layer of the lifting pipe and the second nozzle at the middle layer and the outlet temperature of the lifting pipe, the conversion of heavy raw oil sprayed by the first nozzle at the upper layer of the lifting pipe is not influenced, and the heavy oil conversion capability is enhanced by improving the agent-oil ratio.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow diagram of one embodiment of the process of the present invention.

Description of the reference numerals

1 riser reactor 2 settler 3 regenerator

4 main fractionating tower 5 hydrotreating reactor 6 gasoline fractionating tower

7 line 8 spool valve 9 line

10 slide valve 11 first nozzle 12 line

13 line 14 line 15 line

16 line 17 line 18 line

19 line 20 line 21 line

22 second nozzle 23 third nozzle 24 line

25 pipeline

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The invention provides a catalytic cracking method for increasing the yield of low-olefin and high-octane gasoline, which comprises the following steps: spraying heavy raw oil into a riser reactor from a first nozzle, contacting with a catalytic cracking catalyst from below, and carrying out catalytic cracking reaction from bottom to top to obtain a catalytic cracking reaction product and a spent catalyst; separating the catalytic cracking reaction products to obtain at least catalytic cracking gasoline and catalytic cracking light cycle oil, feeding the spent catalyst into a regenerator for coke burning regeneration, and feeding the obtained regenerated catalyst serving as the catalytic cracking catalyst into the riser reactor; cutting the obtained catalytic cracking gasoline to obtain light gasoline fraction, medium gasoline fraction and heavy gasoline fraction; contacting the obtained catalytic cracking light cycle oil with a hydrotreating catalyst in a hydrotreating reactor and carrying out hydrotreating to obtain hydrogenated diesel oil; mixing part of the light gasoline fraction with at least part of hydrogenated diesel oil to obtain a mixed fraction; and respectively injecting the mixed fraction and part of the medium gasoline fraction into the riser reactor from a second nozzle and a third nozzle to perform the catalytic cracking reaction. The method of the invention can increase the yield of the gasoline to the maximum extent, reduce the yield of light cycle oil, reduce the olefin content in the gasoline and improve the octane number of the gasoline.

According to the invention, the method may further comprise: taking gasoline produced by an external catalytic cracking unit as the catalytic cracking gasoline for cutting; and/or the light cycle oil produced by an external catalytic cracking device is used as the catalytic cracking light cycle oil for carrying out the hydrotreatment, so that the utilization rate of the light cycle oil and the catalytic cracking gasoline can be further improved.

The cutting of the gasoline according to the invention is well known to the person skilled in the art and can be carried out in a fractionation column, from the top, side and bottom of which fractions are obtained, for example the cut points of the light and medium gasoline fractions can be in the range of 60-80 ℃ and the cut points of the medium and heavy gasoline fractions can be in the range of 120-130 ℃.

According to the invention, the method may further comprise: and sending part of the light gasoline fraction, part of the medium gasoline fraction and all of the heavy gasoline fraction to a subsequent absorption stabilizing device. In the invention, part of the gasoline fraction is circulated back to the riser reactor for catalytic cracking reaction, and the rest gasoline fraction is sent to the gasoline pool as a gasoline component, so that the properties of gasoline in the gasoline pool, such as octane number, olefin content and the like, can be adjusted. Specifically, the present invention preferably injects 2 to 90 wt%, more preferably 10 to 80 wt% of medium gasoline fraction into the riser reactor, preferably injects a mixed fraction obtained by mixing 2 to 90 wt%, more preferably 10 to 70 wt% of light gasoline fraction with 10 to 100 wt%, more preferably 30 to 100 wt% of hydrogenated diesel oil into the riser reactor, and feeds the rest gasoline fraction to a subsequent absorption stabilizer, more preferably injects medium gasoline fraction with a distillation range of 90 to 130 ℃ into the riser reactor to perform the catalytic cracking reaction.

Hydrotreating is a process well known to those skilled in the art according to the present invention, and conditions may include: the reaction temperature is 330-450 ℃, preferably 340-380 ℃, the hydrogen partial pressure is 6-25 MPa, preferably 10-22 MPa, and the volume space velocity is 0.1-2 hours^-1The volume ratio of hydrogen to oil is 1000-2000Nm³/m³. The hydrotreating catalyst can comprise a carrier and an active component loaded on the carrier, wherein the active component can be at least one selected from group VIB metals and group VIII non-noble metals, the group VIB metals can be molybdenum or/and tungsten, the group VIII non-noble metals can be nickel or/and cobalt, the active component is preferably a combination of nickel-tungsten, nickel-tungsten-cobalt, nickel-molybdenum or cobalt-molybdenum, and the carrier can be at least one selected from alumina, silicon oxide and amorphous silicon-aluminum. In the hydrogenation product of the catalytic cracking light cycle oil, part of gas and gasoline fractions are generated, so that the products need to be separated to obtain hydrogenated diesel oil with the initial boiling point of more than 165 ℃, and the content of bicyclic aromatics in the hydrogenated diesel oil is generally not more than 10 wt%, preferably not more than 8 wt%.

Riser reactors according to the present invention are well known to those skilled in the art, for example, they may be constant diameter riser reactors with or without bed reactors or may be variable diameter riser reactors with or without bed reactors.

According to the present invention, the first nozzle, the second nozzle and the third nozzle are preferably spaced from top to bottom. More preferably, the oil and gas residence time of the riser reaction section between the third nozzle and the second nozzle may be in the range of from 0.01 to 2 seconds, preferably from 0.05 to 1 second, and the oil and gas residence time of the riser reaction section between the second nozzle and the first nozzle may be in the range of from 0.01 to 3 seconds, preferably from 0.05 to 2 seconds.

Catalytic cracking is a well known process to those skilled in the art according to the present invention, and the present invention is not described in detail, and conditions may include: the reaction temperature is 480-650 ℃, preferably 490-550 ℃, the weight ratio of the catalytic cracking catalyst to the heavy raw oil is 2-100, preferably 4-50, the oil-gas retention time of the heavy raw oil is 1-10 seconds, preferably 2-8 seconds, the reaction pressure (absolute pressure) is 0.15-0.4 MPa, the weight ratio of the atomized water vapor to the heavy raw oil is 0.01-0.5, preferably 0.02-0.2, the micro-reaction activity (MAT) of the catalytic cracking catalyst is not less than 55, preferably not less than 60, and the micro-reaction activity is determined by the micro-reaction activity test method of the RIPP92-90 catalytic cracking industrial equilibrium catalyst (petrochemical analysis method (RIPP test method), Cuiyan edition, 1990 edition and the like). The catalytic cracking catalyst may comprise, on a dry basis and based on the weight of the catalytic cracking catalyst, 10 to 50 wt% of a zeolite, at least one zeolite selected from the group consisting of rare earth-containing or non-containing Y, rare earth-containing or non-containing HY, rare earth-containing or non-containing USY, and rare earth-containing or non-containing Beta, 5 to 90 wt% of an inorganic oxide, and 0 to 70 wt% of a clay.

The following further illustrates embodiments of the invention by way of the accompanying drawings, but the invention is not limited thereto.

As shown in fig. 1, heavy raw oil is injected into a riser reactor 1 from a first nozzle 11 at the lower part of the riser reactor 1 to perform catalytic cracking reaction, so as to obtain a catalytic cracking product and a spent catalyst, the catalytic cracking product is settled and separated by a settler 2, and the catalytic cracking product is sent into a main fractionating tower 4 through a pipeline 24 to be fractionated, so as to obtain catalytic cracking gasoline and catalytic cracking light cycle oil. The spent catalyst is sent into the regenerator 3 through a pipeline 7 and a slide valve 8 for coke burning regeneration, and the regenerated catalyst is obtained. The catalytically cracked gasoline from the main fractionating tower 4 is fed into the gasoline fractionating tower 6 via pipeline 13, and cut by the fractionating tower to obtain light gasoline fraction, which is led out via pipeline 15, medium gasoline fraction, which is led out via pipeline 16, and heavy gasoline fraction, which is led out via pipeline 17 and sent to the subsequent absorption stabilizer (not shown). Other gasoline fractions not comprised in the light, medium and heavy gasoline fractions are also taken from line 25 to the subsequent absorption stabilization unit. A portion of the light gasoline fraction exiting line 15 is withdrawn from line 18 to a subsequent absorption stabilizer, while another portion of the light gasoline fraction is returned to riser reactor 1 via line 19; the portion of the gasoline fraction exiting line 16 is withdrawn from line 20 to a subsequent absorption stabilizer, while another portion of the gasoline fraction is injected from line 21 back into riser reactor 1 via third nozzle 23 of riser reactor 1. The catalytic cracking light cycle oil from the main fractionation column 4 is led out from a line 14 to a hydrotreating reactor 5, the obtained hydrogenated diesel oil is led out from a line 12, and is mixed with the light gasoline fraction from a line 19 and then is injected into the riser reactor 1 through a second nozzle 22 of the riser reactor 1, and the first nozzle, the second nozzle and the third nozzle are arranged from top to bottom in the height direction. In the riser reactor, gasoline fraction, light gasoline fraction, hydrogenated diesel oil and heavy raw oil are contacted with regenerated catalyst from a regenerator through a slide valve 10 and a pipeline 9, reacted and go upward for catalytic cracking reaction, and the obtained catalytic cracking product and spent catalyst are sent into a settler for settling separation.

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

In the examples and comparative examples, the hydrotreating catalyst filled in the hydrotreating reactor was designated by commercial designation RN-32V, the protectant was designated by commercial designation RG-1, and the loading volume ratio of the hydrotreating catalyst to the protectant was 95: 5, all produced by the China petrochemical catalyst division.

The physicochemical properties of the catalysts used in the riser reactors of the examples and comparative examples are shown in Table 1, having a commercial designation CC20-DV, manufactured by the Chinese petrochemical catalyst division.

The properties of the heavy feed oil used in the examples and comparative examples are shown in Table 2.

In Table 3, the light cycle oil recycle ratio is the weight of light cycle oil hydrocracked/the weight of heavy feed oil,

the gasoline octane number determination (RON) was carried out by the GB/T5487-2015 method, and the gasoline octane number determination (motor method, MON) was carried out by the GB/T503-2016 method.

Example 1

This example illustrates the reaction carried out using the process of the invention as shown in FIG. 1.

Spraying heavy raw oil into the riser reactor from a first nozzle on the upper layer of the riser reactor to perform catalytic cracking reaction to obtain catalytic cracking gasoline and catalytic cracking light cycle oil, wherein the catalytic cracking reaction conditions are as follows: the reaction temperature is 515 ℃, the agent-oil weight ratio of the heavy raw oil is 6, the oil-gas retention time of the heavy raw oil is 3.2 seconds, the reaction pressure (absolute pressure) is 0.32 MPa, and the weight ratio of the atomized water vapor to the heavy raw oil is 0.06. The Microreactivity (MAT) of the equilibrator was 62.

The catalytic cracking gasoline is cut in a gasoline fractionating tower through distillation ranges to obtain light gasoline fractions, medium gasoline fractions and heavy gasoline fractions, and the distillation ranges of the fractions are as follows: the distillation range of the light gasoline fraction is less than or equal to 60 ℃, the distillation range of the medium gasoline fraction is less than or equal to 120 ℃ at 90 ℃, and the distillation range of the heavy gasoline fraction is more than or equal to 120 ℃. In this example, 30 wt% of the light gasoline fraction and 50 wt% of the medium gasoline fraction were recycled back to the riser reaction. The other gasoline fraction is sent to the subsequent absorption and stabilization device.

And (3) feeding the catalytic cracking light cycle oil into a hydrogenation device to obtain hydrogenated diesel oil, wherein the content of the bicyclic aromatic hydrocarbon in the hydrogenated diesel oil is 15 wt%, and the initial boiling point of the hydrogenated diesel oil is 180 ℃. The conditions of the hydrotreatment are as follows: hydrogen partial pressure 10.0 mpa; the average bed reaction temperature is 354 ℃, and the volume space velocity is 0.5 hour^-1Hydrogen to oil volume ratio of 1400Nm³/m³。

The middle gasoline fraction is fed into the lower third nozzle of the riser reactor of the catalytic cracking device, the light gasoline fraction and all the hydrogenated diesel oil are fed into the middle second nozzle of the catalytic cracking riser reactor, and the heavy raw oil is fed into the upper first nozzle of the riser reactor. The oil gas residence time of the riser reaction section between the third nozzle and the second nozzle is 0.2 seconds, the oil gas residence time of the riser reaction section between the second nozzle and the first nozzle is 0.3 seconds, and the specific reaction results are shown in table 3.

Comparative example 1

This comparative example is essentially the same as example 1, except that: and (3) spraying the heavy raw oil into the riser reactor from a first nozzle positioned on the upper layer, and sending the catalytically cracked gasoline and the catalytically cracked light cycle oil out of the catalytic cracking device, wherein the specific reaction results are shown in table 3.

Comparative example 2

This comparative example is essentially the same as example 1, except that: directly circulating 30 wt% of catalytic gasoline to a third nozzle at the lower layer of the riser reactor without cutting by a gasoline fractionating tower, spraying other gasoline to a subsequent absorption stabilizing device, spraying heavy raw oil into the riser reactor from a first nozzle at the upper layer, hydrogenating the catalytic cracking light cycle oil, and spraying hydrogenated diesel oil into the riser reactor from a second nozzle at the middle layer, wherein the specific reaction result is shown in table 3.

Comparative example 3

This comparative example is essentially the same as example 1, except that: hydrogenating the catalytic cracking light cycle oil to obtain hydrogenated diesel oil; 50 wt% of light gasoline fraction and all hydrogenated diesel oil are mixed and then enter the riser reactor from a second nozzle at the middle layer of the riser reactor, heavy raw oil is sprayed into the riser reactor from a first nozzle at the upper layer, and the rest gasoline fraction is sent to a subsequent absorption stabilizing device, wherein the specific reaction result is shown in table 3.

Comparative example 1 is a conventional catalytic cracking process with a gasoline yield of 42.95 wt%, a gasoline olefin content of 26.2 body%, a sulfur content of 537.4ppm, and a RON of 91.6 for the heavy feed oil in table 2.

In order to reduce the yield of the catalytic cracking light cycle oil, the light cycle oil is hydrogenated and then recycled (the recycle ratio is 0.43) in a comparative example 2, and meanwhile, part of the catalytic cracking gasoline is directly recycled, wherein the yield of the gasoline is 55.32 wt%, the olefin content of the gasoline is 19.4% by body, the sulfur content is 349.6ppm, and the RON is 91.9.

The light cycle oil recycle ratio of comparative example 3 was 0.4, the gasoline yield was 56.58 wt%, the gasoline olefin content was 14.8 vol%, the sulfur content was 350.2ppm, and the RON was 90.2. in comparison with comparative example 1, comparative example 3 increased gasoline and significantly decreased gasoline octane number while significantly decreased gasoline olefin content.

The light cycle oil recycle ratio of example 1 was 0.37, the gasoline yield was 58.83 wt%, the gasoline olefin content was 14.6% by volume, the sulfur content was 342ppm, and the RON was 93.2; compared with the comparative example 1, the example 1 not only converts the light cycle oil, but also greatly increases the yield of the gasoline, and the gasoline has low olefin content and high octane number; compared with the comparative example 2, the light cycle oil remill ratio and the hydrogen consumption are reduced, the gasoline yield is high, the olefin content of the gasoline is low, and the octane number is high; compared with the comparative example 3, on the premise of equivalent olefin content of the gasoline, the light cycle oil remixing ratio and the hydrogen consumption are lower, the gasoline yield is high, and the octane number is high.

TABLE 1 CC20-DV catalyst Properties

TABLE 2 Properties of the feed oils

Raw oil name	Heavy oil
		Density (20 deg.C), kg/m³	927.8
Refractive index (70 ℃ C.)	1.5015
		Freezing point, DEG C	26
Carbon residue, by weight%	3.63
		Viscosity (80 ℃ C.)/(mm)²Second)	26.23
Viscosity (100 ℃ C.)/(mm)²Second)	14.26
		Freezing point/. degree.C	26
Basic nitrogen weight fraction/(microgram/gram)	595
		Hydrocarbon family weight composition/weight%
Saturated hydrocarbons	58.6
		Aromatic hydrocarbons	32.0
Glue	8.8
		Asphaltenes	0.6
Sulfur weight fraction/(microgram/gram)	11 200
		Carbon weight fraction/weight%	86.26
Hydrogen weight fraction/weight%	12.28
		Nitrogen weight fraction/weight%	0.19
Ni weight fraction/(microgram/gram)	7.1
		V weight fraction/(microgram/gram)	7.5
Fe weight fraction/(microgram/gram)	3.2

TABLE 3

Claims

1. A catalytic cracking method for increasing the yield of low-olefin and high-octane gasoline comprises the following steps:

spraying heavy raw oil into a riser reactor from a first nozzle, contacting with a catalytic cracking catalyst from below, and carrying out catalytic cracking reaction from bottom to top to obtain a catalytic cracking reaction product and a spent catalyst;

separating the catalytic cracking reaction products to obtain at least catalytic cracking gasoline and catalytic cracking light cycle oil, feeding the spent catalyst into a regenerator for coke burning regeneration, and feeding the obtained regenerated catalyst serving as the catalytic cracking catalyst into the riser reactor;

cutting the obtained catalytic cracking gasoline to obtain light gasoline fraction, medium gasoline fraction and heavy gasoline fraction; the cutting points of the light gasoline fraction and the middle gasoline fraction are 60-80 ℃, and the cutting points of the middle gasoline fraction and the heavy gasoline fraction are 120-130 ℃;

contacting the obtained catalytic cracking light cycle oil with a hydrotreating catalyst in a hydrotreating reactor and carrying out hydrotreating to obtain hydrogenated diesel oil;

mixing part of the light gasoline fraction with at least part of hydrogenated diesel oil to obtain a mixed fraction;

and respectively injecting the mixed fraction and part of the medium gasoline fraction into the riser reactor from a second nozzle and a third nozzle to perform the catalytic cracking reaction.

2. The method of claim 1, further comprising: taking gasoline produced by an external catalytic cracking unit as the catalytic cracking gasoline for cutting; and/or

And taking the light cycle oil produced by the external catalytic cracking unit as the catalytic cracking light cycle oil for the hydrotreatment.

3. The process according to claim 1, wherein a medium gasoline fraction having a distillation range in the range of 90-130 ℃ is injected into the riser reactor to perform the catalytic cracking reaction.

4. The method of claim 1, further comprising: and sending part of the light gasoline fraction, part of the medium gasoline fraction and all of the heavy gasoline fraction to a subsequent absorption stabilizing device.

5. The process of claim 1 wherein from 2 to 90 weight percent of a medium gasoline fraction is injected into said riser reactor.

6. The process of claim 1 wherein a mixed fraction obtained by mixing 2 to 90 wt.% of the light gasoline fraction with 10 to 100 wt.% of the hydrogenated diesel oil is injected into the riser reactor.

7. The method of claim 1, wherein the hydrotreating conditions comprise: the reaction temperature is 330-450 ℃, the hydrogen partial pressure is 6-25 MPa, and the volume space velocity is 0.1-2 hours^-1The volume ratio of hydrogen to oil is 1000-2000Nm³/m³。

8. The method of claim 1, wherein the hydrotreating catalyst comprises a support and an active component supported on the support, the active component being at least one selected from group VIB metals and group VIII non-noble metals, and the support being at least one selected from alumina, silica, and amorphous silica-alumina.

9. The process of claim 1, wherein the hydrogenated diesel oil has a bicyclic aromatic content of no greater than 10 wt.% and a first boiling point of greater than 165 ℃.

10. The process of claim 1 wherein the riser reactor is a constant diameter riser reactor with or without a bed reactor or a variable diameter riser reactor with or without a bed reactor.

11. The method of claim 1, wherein the first, second and third nozzles are spaced from top to bottom.

12. The method of claim 11, wherein the hydrocarbon residence time of the riser reaction zone between the third nozzle and the second nozzle is between 0.01 and 2 seconds and the hydrocarbon residence time of the riser reaction zone between the second nozzle and the first nozzle is between 0.01 and 3 seconds.

13. The method of claim 11, wherein the hydrocarbon residence time of the riser reaction zone between the third nozzle and the second nozzle is between 0.05 and 1 second and the hydrocarbon residence time of the riser reaction zone between the second nozzle and the first nozzle is between 0.05 and 2 seconds.

14. The process of claim 1, wherein the conditions of the catalytic cracking reaction comprise: the reaction temperature is 480-650 ℃, the weight ratio of the catalytic cracking catalyst to the heavy raw oil is 2-100, the oil gas retention time of the heavy raw oil is 1-10 seconds, the reaction pressure is 0.15-0.4 MPa, the weight ratio of the atomized steam to the heavy raw oil is 0.01-0.5, the micro-reaction activity of the catalytic cracking catalyst is not lower than 55, and the micro-reaction activity is determined by a micro-reaction activity test method of an RIPP92-90 catalytic cracking industrial equilibrium catalyst.