TWI546375B - A method for producing olefins and low benzene content gasoline from naphtha - Google Patents

Description

Method for producing olefin and low benzene content gasoline from naphtha

The present invention is a combination process, and more particularly, a process for producing light olefins and low benzene gasoline components using naphtha as a raw material.

Catalytic reforming and steam cracking are mature industrial technologies in the petrochemical industry. The main purpose of catalytic reforming is to produce aromatic hydrocarbons, high-octane gasoline and hydrogen. During the catalytic reforming process, several competitive reactions can occur simultaneously. These reactions include dehydrogenation of alkylcyclohexane to aromatic hydrocarbons, dehydroisomerization of alkylcyclopentane to aromatic hydrocarbons, dehydrocyclization of paraffins to aromatic hydrocarbons, paraffins. Hydrocracking is converted to light hydrocarbon products other than gasoline boiling range, isomerization of alkylbenzene dealkylation and paraffins. In order to obtain a high-octane gasoline blending component or an aromatic hydrocarbon, it is not only desirable to dehydrogenate the cycloalkane to an aromatic hydrocarbon, but also to maximize the conversion of the paraffin and increase the yield of the aromatic hydrocarbon.

Since benzene in automobile exhaust is one of the important factors of air pollution, the new gasoline specifications proposed and implemented by various countries are required to reduce the benzene content in gasoline. By analyzing the contribution of various gasoline blending components in the gasoline pool to the gasoline benzene content, it is found that 70%~85% of the benzene in the gasoline pool is derived from the reformed gasoline of the catalytic reforming unit. Therefore, the catalytic reforming unit reforms to form oil. in Benzene is the main source of benzene in gasoline. The key to reducing the benzene content in gasoline is to reduce the benzene content in the reformed oil.

The main purpose of steam cracking is to produce ethylene, propylene and butadiene. As the chemical market's demand for propylene and butadiene increases, how to increase propylene and butadiene from limited naphtha resources is a matter of great concern.

The raw material for catalytic reforming is naphtha, which in turn is a major component in the composition of the steam cracker. As crude oil becomes heavier, naphtha yields decrease, and global demand for ethylene and aromatics continues to increase, the problems of catalytic reforming and steam cracking units vying for raw materials are becoming more prominent.

Naphtha is a mixture of various hydrocarbons such as normal paraffins, isoparaffins, cycloalkanes and aromatics. Compared with isoparaffins and naphthenes, normal paraffins have higher yields for cracking ethylene production, and relatively high propylene and butadiene yields for cracking of naphthenes. The aromatic benzene rings are relatively difficult to crack under typical cracking conditions. It has little contribution to the formation of ethylene, and naphthenes are easily converted into aromatic hydrocarbons under catalytic reforming conditions, and are excellent catalytic reforming raw materials. Therefore, how to optimize the raw materials of catalytic reforming and steam cracking equipment is a problem that people are extremely concerned about and urgently need to solve.

CN1277907C discloses a naphtha recombination treatment method, comprising the following steps: (1) first extracting and separating naphtha, separating raffinate oil and extracting oil; (2) drawing residual oil into ethylene steam cracking device; (3) The oil is withdrawn into the reformer for reforming. The extraction separation used in the invention is actually liquid-liquid extraction. In the given examples, the solvent ratio of cyclobutanin as the extraction solvent is 11, the operating temperature is 95-128 ° C, and the operating pressure is 0.6-1.0 MPa. The operating parameters given can only separate alkane and aromatics. The main component in the raffinate oil is an alkane.

The above method extracts and separates naphtha, and obtains an alkane-based raffinate oil and an aromatic hydrocarbon and naphthene-based extracting oil, although the separated alkane-based raffinate oil can be used as a steam cracking raw material to increase ethylene. yield, but not effectively utilized cycloalkane, resulting in decreased yield of propylene, and butadiene; C ₆ cycloalkane most withdrawn into the oil, resulting in higher gasoline reformate benzene content. And when the paraffin content in naphtha is low, the same demand for natriene will increase the demand for naphtha.

It is an object of the present invention to provide a process for producing olefins and low benzene content gasoline from naphtha which improves the utilization of naphtha while producing more ethylene, propylene and butadiene from naphtha. It is also possible to produce gasoline components with low benzene content.

The invention provides a method for producing olefin and low benzene content gasoline from naphtha, comprising the following steps: (1) extractive distillation of naphtha to obtain extracted oil containing naphthenes and aromatic hydrocarbons, and alkanes and C ₆ naphthenes. The raffinate oil, the mass ratio of C ₆ naphthenes in the raffinate oil to the C ₆ naphthenes in the naphtha is 80-95%, and (2) the oil is extracted at 0.01-3.0 MPa, 300-600 ° C, Hydrogen / hydrocarbon molar ratio of 0.5-20, volumetric space velocity of 0.1-50h ^-1 under conditions of contact with the reforming catalyst for catalytic reforming reaction, to obtain a low benzene content reforming oil, (3) will be the residual oil It is sent to a steam cracking unit for cracking reaction to produce light olefins.

The method of the invention extracts and distills naphtha, cuts most of the C ₆ naphthene into the raffinate oil, and extracts the main component of the oil as C ₇ ⁺ cycloalkane and aromatic hydrocarbon, and catalytically reforming the extracted oil to obtain low benzene. The content of gasoline, cracking the raffinate oil, can increase the yield of light olefins (ethylene, propylene and butadiene).

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30‧‧‧Restruction product distillation column

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Fig. 1 is a schematic view showing the process of producing olefin and low benzene gasoline by using hydrorefined naphtha as raw material in the method of the present invention.

2 is a schematic view showing the process of producing olefin and low benzene gasoline using naphtha as a raw material in the method of the present invention.

The process of the present invention extracts and distills naphtha to obtain a raffinate oil containing alkanes and C ₆ naphthenes and an extract oil containing naphthenes and aromatics. By reducing the proportion of C ₆ naphthenes in the extracted oil, not only is the benzene content in the reformed gasoline component reduced, but the yield of the gasoline component is also increased. The cycloalkane contained in the raffinate oil increases the yield of propylene and butadiene. The process of the invention converts naphtha to more light olefins and low benzene reformate gasoline components.

In the step (1) of the present invention, the alkane and the aromatic hydrocarbon in the naphtha are separated by extractive distillation, and most of the C ₆ naphthenes are cut into the raffinate oil, so that the main components in the raffinate oil are alkanes and C ₆ naphthenes. . The mass ratio of the C ₆ naphthenes in the raffinate oil to the C ₆ naphthenes in the naphtha is preferably 88 to 95%.

The extractive distillation described in the step (1) is carried out in an extractive distillation column. The process of extractive distillation separation is: feeding naphtha into an extractive distillation column and contacting the extraction solvent under gas phase conditions. C ₆ alkanes and cycloalkanes most directly discharged overhead from the extractive distillation, rich in aromatics and naphthenes is discharged into the rich solvent by the solvent separating column bottoms. The aromatic hydrocarbon and the cycloalkane are separated from the solvent, and the obtained lean solvent is returned to the extractive distillation column for use in the loop.

The operating conditions of the extractive distillation column are: solvent ratio, that is, the mass ratio of the solvent to the extractive distillation feed is 1-10:1, the mass ratio is preferably 3-8:1, and the temperature at the top of the column is 70-190 ° C, preferably 75- 180 ° C is more preferably 75 to 100 ° C, and the pressure is 0.1 to 0.3 MPa, and the pressure is preferably 0.1 to 0.2 MPa.

In the present invention, the pressure of the extractive distillation column is expressed by absolute pressure, and the other pressures are gauge pressure.

(1) The extraction solvent used in the extractive distillation is selected from the group consisting of cyclobutyl hydrazine, dimethyl hydrazine, dimethylformamide, N-methylpyrrolidone, N-methylmorpholine, triethylene glycol, tetraethylene glycol, Pentaethylene glycol, methanol or acetonitrile.

Since the impurities such as olefin, sulfur, nitrogen, arsenic, oxygen, chlorine and the like contained in the reforming reaction raw material adversely affect the catalytic reforming device and the reforming catalyst, the reforming feed is preferably carried out before the reforming reaction is carried out. Hydrorefining, the olefins therein are hydrosaturated, and impurities such as sulfur, nitrogen, arsenic, oxygen, chlorine and the like are removed to obtain a hydrorefining reforming raw material.

In the method of the present invention, both the naphtha in the step (1) and the oil extracted in the step (2) are preferably subjected to hydrotreating. Specifically, the naphtha according to the step (1) is preferably subjected to hydrotreating before extraction separation, or the hydrolyzed oil described in the step (2) is subjected to hydrorefining before the reforming reaction to obtain an olefin therein. Saturate and remove impurities from it. Extract refined naphtha or refined The sulfur content in the oil is less than 0.5 ug/g, the nitrogen content is less than 0.5 ug/g, the arsenic content is less than 1.0 ng/g, and the lead content is less than 10 ng/g.

The hydrotreating reaction temperature is 260-460 ° C, preferably 280-400 ° C, the pressure is 1.0-8.0 MPa, preferably 1.6-4.0 MPa, and the feed volumetric space velocity is 1-20 h ^-1 , preferably 2-8 h ^{- 1. The} hydrogen/hydrocarbon volume ratio during the reaction is 10 to 1000:1, preferably 50 to 600:1.

The hydrofinishing catalyst should have a hydrogenated saturated olefin with the ability to hydrodesulfurize, denitrify and deoxidize. The hydrotreating catalyst comprises 5 to 49% by mass of a hydrogenation active component, 0.1 to 1.0% by mass of a halogen, and 50.0 to 94.9% by mass of an inorganic oxide carrier. The hydrogenation active component is selected from the group consisting of oxides of one or more of Co, Ni, Fe, W, Mo, Cr, Bi, Sb, Zn, Cd, Cu, In, and rare earth metals. The inorganic oxide support is preferably alumina.

The process (2) of the present invention is a process for catalytic reforming of an oil containing aromatic hydrocarbons and naphthenes. The pressure of the catalytic reforming reaction is preferably 0.2 to 2.0 MPa. The temperature is preferably from 350 to 520 ° C, more preferably from 400 to 520 ° C. The naphtha volume space velocity is preferably 1.0 to 30 h ^-1 , more preferably 2.0 to 25.0 h ^-1 .

(2) The hydrogen/hydrocarbon molar ratio of the catalytic reforming reaction in the step is preferably from 1 to 8:1.

The catalytic reforming of the present invention may employ a continuous (moving bed) reforming technique, a semi-regenerative (fixed bed) reforming technique or a loop regeneration reforming technique.

The catalyst used in the catalytic reforming according to the method (2) of the present invention comprises 0.01 to 5.0% by mass of a Group VIII metal, 0.01 to 5.0% by mass of a halogen, and 90.0 to 99.97% by mass of an inorganic oxide carrier.

When the reforming reaction is continuously reformed in a moving bed, the catalyst preferably comprises 0.01 to 3.0% by mass of a Group VIII metal, 0.01 to 5.0% by mass of a halogen, 0.01 to 5.0% by mass of Sn, and 87.0 to 99.97% by mass of an inorganic substance. Oxide carrier. In the case of fixed bed semi-regeneration reforming, the catalyst preferably comprises 0.01 to 3.0% by mass of a Group VIII metal, 0.01 to 5.0% by mass of a halogen, 0.01 to 5.0% by mass of Re, and 87.0 to 99.97% by mass of an inorganic oxide carrier. The Sn or Re is a second metal component.

The above continuous reforming or semi-regeneration reforming catalyst may further comprise one or more selected from the group consisting of alkali metals, alkaline earth metals, rare earth elements, In, Co, Ni, Fe, W, Mo, Cr, Bi, Sb, Zn, Cd. Or the third metal component of Cu.

The Group VIII metal described in the above catalyst is preferably platinum. The inorganic oxide support is preferably alumina.

The reforming catalyst is prepared by a conventional method. The shaped carrier is first prepared and may be in the form of a sphere or a strip. The metal component and the halogen are then impregnated. If the catalyst contains the second and third metal components, it is preferred to introduce the second and third metal components in the carrier, and finally to introduce the Group VIII metal and the halogen. The carrier after the introduction of the metal component is dried, and calcined at 450 to 650 ° C to obtain an oxidation state reforming catalyst. The oxidation state reforming catalyst needs to be reduced in a hydrogen atmosphere at 315 to 650 ° C before use to obtain a reduced reforming catalyst. Pre-vulcanization is also required for the platinum-ruthenium reforming catalyst.

After the reforming reaction, catalytic reforming reaction liquid product following removal of C ₄ hydrocarbon fractionation column fractionation, to obtain a low benzene reformate, i.e., low benzene gasoline.

The naphtha of the present invention has an initial boiling point of ASTM D-86 A hydrocarbon mixture at 40 to 80 ° C and a final boiling point of 160 to 220 ° C.

The naphtha is selected from the group consisting of straight run naphtha, hydrocracked naphtha, coker naphtha, catalytic cracked naphtha or oil field condensate.

The naphtha contains 30 to 85% by mass of an alkane, 10 to 50% by mass of a cycloalkane, and 5 to 30% by mass of an aromatic hydrocarbon. The naphtha content of C ₆ cycloalkane is 1 to 10 mass%.

The invention will now be further described with reference to the accompanying drawings.

In Figure 1, naphtha from line 1 is mixed with make-up hydrogen from line 2 and then with the loop hydrogen from line 9 into hydrofinishing reactor 3. The hydrofinished product enters the gas-liquid separation tank 5 from line 4. The hydrogen-rich gas separated in the upper portion of the gas-liquid separation tank 5 is returned to the loop compressor 8 from the line 6 to be looped, and the stream flowing out from the bottom of the gas-liquid separation tank 5 enters the rectification column 10 via the line 7. After rectification, the liquefied gas is discharged from the line 11 at the upper portion of the rectification column 10, and the purified naphtha is discharged from the bottom of the rectification column 10, and enters the extractive distillation column 13 via the line 12. By extractive distillation to separate aromatics and paraffins, while most of the C ₆ paraffins naphthenes separated into components, at least partially separated into the aromatic component. The components containing alkanes and C ₆ naphthenes after extractive distillation are passed from line 17 to steam cracking zone 22 for steam cracking. The rich solvent containing naphthenic hydrocarbons and aromatic hydrocarbons discharged from the bottom of the extractive distillation column 13 is passed from the line 15 to the solvent recovery column 19 to separate the solvent. The lean solvent obtained at the bottom of the solvent recovery column 19 is discharged from the line 21 and can be returned to the extractive distillation column 13 for use in a loop. The aromatic-containing and naphthenic-containing stream obtained in the upper portion of the solvent recovery column 19 is mixed with the reforming loop hydrogen from the line 29 via line 20 and then passed to the reforming reactor 23 for catalytic reforming. The reforming reaction product enters the reformate gas-liquid separation tank 25 from the line 24, and the hydrogen-rich gas separated from the upper portion is recycled by the line 26 through the loop compressor 28, and the liquid component flowing out from the bottom enters the heavy portion by the line 27. The entire product rectification column 30. The liquefied gas obtained by the rectification is discharged from the upper line 31, and the reformed produced oil is discharged from the bottom line 32 into the aromatic hydrocarbon separation zone (not shown).

Fig. 2 shows a scheme in which the naphtha is subjected to extractive distillation, and the oil is extracted and hydrotreated, followed by catalytic reforming. Naphtha enters the extraction separation zone 13 from line 1. The alkane and the aromatic hydrocarbon are separated by extraction separation while separating most of the C ₆ naphthenes into the alkane component and a small portion of the aromatic component. After separation of enriched fractions C ₆ paraffins and naphthenes by line 17 to a steam cracking zone 22 for the steam cracker. The rich solvent containing naphthenic hydrocarbons and aromatic hydrocarbons discharged from the bottom of the extractive distillation column 13 is passed from the line 15 to the solvent recovery column 19 to separate the solvent. The lean solvent obtained at the bottom of the solvent recovery column 19 is discharged from the line 21 and can be returned to the extractive distillation column 13 for use in a loop. The naphthenic-containing and aromatic-containing stream obtained in the upper portion of the solvent recovery column 19, that is, the extracted oil is mixed with the supplementary hydrogen from the line 2 via the line 20, and then enters the hydrotreating reactor 3 together with the looped hydrogen from the line 9. The hydrofinished product enters the gas-liquid separation tank 5 from line 4. The hydrogen-rich gas separated in the upper portion of the gas-liquid separation tank 5 is returned to the loop compressor 8 from the line 6 to be looped, and the stream flowing out from the bottom of the gas-liquid separation tank 5 enters the rectification column 10 via the line 7. After rectification, the liquefied gas is discharged from the line 11 in the upper portion of the rectification column 10, and the refined extracted oil flows out from the bottom of the rectification column 10, and is mixed with the reforming loop hydrogen from the line 29 through the line 12 to enter the reforming reactor 23 Catalytic reforming is carried out. The reforming reaction product enters the reformate gas-liquid separation tank 25 from the line 24, and the hydrogen-rich gas separated from the upper portion is recycled by the line 26 through the loop compressor 28, and the liquid component flowing out from the bottom enters the heavy portion by the line 27. The entire product rectification column 30. The liquefied gas obtained by the rectification is discharged from the upper line 31, and the reformed produced oil is discharged from the bottom line 32 into the aromatic hydrocarbon separation zone (not shown).

The invention will be further illustrated in detail by way of examples, but the invention is not limited thereto.

Example 1

This example hydrotreats naphtha.

In a 20 ml fixed bed continuous flow reactor, 20 ml of hydrotreating catalyst A was charged, which contained 0.03 mass% of CoO, 2.0 mass% of NiO, 19.0 mass% of WO ₃ , 0.7 mass% of F, and 78.27 mass%. Al ₂ O ₃ .

The naphtha of the composition and properties listed in Table 1 was passed through the above filling at 290 ° C, a hydrogen partial pressure of 1.6 MPa, a hydrogen/hydrocarbon volume ratio of 200:1, and a feed volume space velocity of 8.0 h-1. Hydrotreating is carried out in the reactor of Catalyst A. The reaction product enters a water cooler and is separated into gas-liquid two phases, which are separately metered and analyzed for composition.

It can be seen from the results of Table 2 that the content of olefin, sulfur, nitrogen, arsenic and lead in the naphtha after hydrorefining reaches the feed requirement of the catalytic reforming reaction.

Example 2

The purified naphtha is subjected to extraction and separation according to the method of the present invention.

The naphtha as a solvent for extractive distillation separation was used, and the naphtha listed in Table 2 was contacted with cyclopentanone in an extractive distillation column at a flow rate of 100 kg/h. The top pressure of the extractive distillation column was 0.145 MPa (absolute pressure). The reflux ratio was 0.25. The temperature of the top of the extractive distillation column was 80 ° C, and the temperature at the bottom of the column was 160 ° C. A solvent rich in aromatic hydrocarbons and naphthenes is obtained from the bottom of the extractive distillation column, and a raffinate oil containing alkanes and C ₆ naphthenes is obtained at the top of the column. The solvent rich in aromatic hydrocarbons and naphthenes is separated from the extraction solvent by distillation to obtain an oil. The yields of extracted oil and raffinate oil (relative to naphtha), group composition and distribution ratio of various hydrocarbons in extracted oil and raffinate oil are shown in Table 3.

Example 3

Using N-formylmorpholine as an extractive distillation solvent, the naphtha listed in Table 2 was contacted with N-methylmorphomorpholine in an extractive distillation column at a flow rate of 100 kg/h. The solvent/feedstock mass ratio was 7.0. The top pressure of the extractive distillation column was 0.145 MPa (absolute pressure). The reflux ratio was 0.25. The temperature of the top of the extractive distillation column was 76 ° C, and the temperature at the bottom of the column was 170 ° C. A solvent rich in aromatic hydrocarbons and naphthenes is obtained from the bottom of the extractive distillation column, and a raffinate oil containing alkanes and C ₆ naphthenes is obtained at the top of the column. The solvent rich in aromatic hydrocarbons and naphthenes is separated from the extraction solvent by distillation to obtain an oil. The yields of extracted oil and raffinate oil (relative to naphtha), group composition and distribution ratio of various hydrocarbons in extracted oil and raffinate oil are shown in Table 3.

Example 4

Using pentaethylene glycol as an extractive distillation solvent, the naphtha listed in Table 2 was contacted with pentaethylene glycol in an extractive distillation column at a flow rate of 100 kg/h. The solvent/feedstock mass ratio was 3.0. The top pressure of the extractive distillation column was 0.145 MPa (absolute pressure). The reflux ratio was 0.20. The temperature of the top of the extractive distillation column was 86 ° C, and the temperature at the bottom of the column was 163 ° C. A solvent rich in aromatic hydrocarbons and naphthenes is obtained from the bottom of the extractive distillation column, and a raffinate oil containing alkanes and C ₆ naphthenes is obtained at the top of the column. The solvent rich in aromatic hydrocarbons and naphthenes is separated from the extraction solvent by distillation to obtain an oil. The yields of extracted oil and raffinate oil (relative to naphtha), group composition and distribution ratio of various hydrocarbons in extracted oil and raffinate oil are shown in Table 3.

Comparative example 1

The naphtha listed in Table 2 was subjected to liquid-liquid extraction for separation of aromatic hydrocarbons and alkanes at a feed flow rate of 100 kg/hr according to the method of CN1277907C Example 3 (using cyclohexane as a solvent). An alkane-rich raffinate oil and an aromatic-rich extractable oil are obtained. The yields of extracted oil and raffinate oil (relative to naphtha), group composition and distribution ratio of various hydrocarbons in extracted oil and raffinate oil are shown in Table 3.

Comparative example 2

100 kg of naphtha listed in Table 2 was passed through a fixed bed containing 5A molecular sieve for adsorption separation. The adsorption temperature was 200 °C. The feed mass space velocity is 0.3 hours ^-1 . The 5A molecular sieve bed has an aspect ratio of 8:1. The adsorption time is 30 minutes. The gas not adsorbed by the 5A molecular sieve is condensed to obtain a raffinate oil, which is rich in naphthenes and aromatic hydrocarbons. Desorption was carried out with nitrogen, the desorption temperature was 400 ° C, and the desorbent feed airspeed was 200 h-1. After desorption, 29.60 kg of depolymerized oil rich in normal paraffins was obtained. The yield and composition of the obtained raffinate oil and desorbed oil are shown in Table 3.

As can be seen from Table 3, Comparative Example 1 separates aromatic hydrocarbons and alkanes by liquid-liquid extraction, and the raffinate oil is mainly an alkane, and the extracted oil is mainly a cycloalkane and an aromatic hydrocarbon. In the naphtha, 3.62% by mass of the naphthenes enter the raffinate oil, and 96.16% by mass of the naphthenes enter the extracted oil. 1.98 mass% of naphtha C ₆ cycloalkane into the raffinate, 98.02% by mass of C ₆ cycloalkane drawn into the oil.

Comparative Example 2 The residual oil contained alkanes, cycloalkanes and aromatics, and the desorbed oil was mainly an alkane. In the naphtha, 8.26 mass% of the naphthenes entered the desorbed oil, and 91.74 mass% of the naphthenes entered the raffinate oil. 4.74% by mass of C ₆ naphthenes in the naphtha enter the desorbed oil, and 95.26 mass% of the C ₆ naphthenes enter the raffinate oil.

After the method 2 of the present invention was separated by extractive distillation, 19.38 mass% of the naphthenes in the naphtha entered the raffinate oil, and 80.62 mass% of the naphthenes entered the extracted oil. In Naphtha 94.08% by mass of C ₆ cycloalkane into the raffinate, 5.92 mass% of C ₆ cycloalkane drawn into the oil.

After the example 3 was separated by extractive distillation, 15.0% by mass of naphthenes in the naphtha were introduced into the raffinate oil, and 85% by mass of the naphthenes entered the extracted oil. In Naphtha 93.45% by mass of C ₆ cycloalkane into the raffinate, 6.55 mass% of C ₆ cycloalkane drawn into the oil.

After the example 4 was separated by extractive distillation, 40.0% by mass of naphthenes in the naphtha were introduced into the raffinate oil, and 60.0% by mass of the naphthenes entered the extracted oil. In the naphtha, 95.0% by mass of C ₆ naphthenes enter the raffinate oil, and 5.0% by mass of naphthenes enter the extracted oil.

Thus, the method of the present invention is that most C ₆ cycloalkane into the raffinate, the raffinate while there is a greater proportion of cycloalkanes, C ₆ cycloalkane only small amounts of oil into the extraction. Therefore, the extraction of oil as a reforming material can significantly reduce the benzene content in the reformed oil.

Example 5

This example illustrates the steam cracking effect of the resulting raffinate oil after extractive distillation separation in accordance with the process of the present invention.

100 kg of naphtha listed in Table 2 was taken, and extractive distillation was carried out in the same manner as in Example 2, and the obtained raffin oil rich in alkanes and naphthenes was used as a steam cracking raw material. The steam cracking reaction conditions were as follows: cracking furnace outlet pressure 0.185 MPa, residence time 0.20 seconds, water/oil mass ratio 0.55, cracking furnace outlet temperature 840 ° C, and light olefin yield (relative to raffinate oil) are shown in Table 4.

Comparative example 3

Take 100 kg of naphtha listed in Table 2, and separate the aromatic hydrocarbons and alkanes by liquid-liquid extraction according to the method of CN1277907C Example 3 (using cyclohexane as solvent). The resulting alkane-rich raffinate is used as a steam cracking feedstock. The steam cracking reaction conditions were as follows: cracking furnace outlet pressure 0.185 MPa, residence time 0.20 seconds, water/oil mass ratio 0.55, cracking furnace outlet temperature 840 ° C, and light olefin yield (relative to raffinate oil) are shown in Table 4.

It can be seen from Table 4 that the raffinate oil obtained by the extractive distillation according to the method of the present invention is used as a steam cracking raw material, and the triene yield is 61.58 mass%, and the triene yield is increased by 2.22% compared with the comparative example 3, wherein the propylene is recovered. The rate increased by 9.07% and the yield of butadiene increased by 14.54%. It is indicated that the raffinate oil obtained by the method of the invention is subjected to steam cracking, which is more advantageous for increasing the production of propylene and butadiene.

Example 6

This example illustrates the catalytic reforming effect of the resulting oil after extractive distillation in accordance with the process of the present invention.

100 kg of naphtha listed in Table 2 was taken and subjected to extractive distillation according to the method of Example 2. The resulting oil is extracted as a catalytic reformer feed using PtSn / γ-Al ₂ O ₃ Catalyst B, where containing 0.35 mass% Pt, Sn 0.30 mass%, Cl 1.0% by mass, the balance is γ-Al ₂ O ₃ .

In a 100 ml fixed bed continuous flow reactor, 50 ml of catalyst B was charged. The reforming reaction was carried out under the conditions of a reaction material inlet temperature of 520 ° C, a reaction pressure of 0.34 MPa, a hydrogen/hydrocarbon molar ratio of 2.5, and a feed volume space velocity of 2.0 h-1. The reforming reaction product was rectified to obtain a C ₅ ⁺ reforming oil, and the reaction results are shown in Table 5.

Comparative example 4

100 kg of naphtha listed in Table 2 was taken, and aromatic hydrocarbons and alkanes were separated according to the method of Example 3 of CN1277907C. The resulting oil was subjected to catalytic reforming in the same manner as in Example 6, except that the reaction material inlet temperature was 514 °C. The reforming reaction product was rectified to obtain a C ₅ ⁺ reforming oil, and the reaction results are shown in Table 5.

It can be seen from Table 5 that the benzene content in the catalytic reforming C ₅ ⁺ produced oil is less than 1.0% by volume, and the comparative ratio is reduced by 49.43%.

Example 7

This example illustrates the production of light olefins and low benzene content gasoline from naphtha in accordance with the process of the present invention.

100 kg of naphtha listed in Table 2 was taken and subjected to extractive distillation according to the method of Example 2. The obtained raffinate oil was used as a steam cracking raw material, and steam cracking reaction was carried out in the same manner as in Example 5. The obtained oil was taken as a catalytic reforming feed, and catalytic reforming was carried out in the same manner as in Example 6. The results are shown in Table 6.

Example 8

100 kg of naphtha listed in Table 2 was taken and subjected to extractive distillation according to the method of Example 3. The obtained raffinate oil was used as a steam cracking raw material, and steam cracking reaction was carried out in the same manner as in Example 5. The obtained oil was taken as a catalytic reforming feed, and catalytic reforming was carried out in the same manner as in Example 6. The results are shown in Table 6.

Comparative example 5

The naphtha listed in Table 2 was divided into 55.55 kg and 44.45 kg at 100 kg, and 44.45 kg of naphtha was subjected to liquid-liquid extraction to separate aromatic hydrocarbons and alkanes according to the method of CN1277907C Example 3. The obtained 29.34 kg of raffinate oil was used as a steam cracking raw material, and the steam cracking reaction was carried out in the same manner as in Example 5. 15.11 kg of extracted oil and 55.55 kg of naphtha were used as catalytic reforming feeds, and catalytic reforming was carried out in the same manner as in Example 6. The results are shown in Table 6.

It can be seen from Table 6 that, compared with Comparative Example 5, the present invention uses naphtha as a raw material to produce a light olefin and a low benzene content gasoline. When the triene yield is substantially equivalent, the propylene production and butadiene production increase. C ₅ ⁺ gasoline production increased.

Example 9

100 kg of naphtha listed in Table 2 was taken and subjected to extractive distillation according to the method of Example 4. The obtained raffinate oil is used as a steam cracking raw material, as in Example 5. The method is carried out by a steam cracking reaction. The obtained oil was taken as a catalytic reforming feed, and catalytic reforming was carried out in the same manner as in Example 6. The results are shown in Table 7.

Comparative example 6

The naphtha listed in Table 2 was divided into 32.58 kg and 67.42 kg at 100 kg, and 67.42 kg of naphtha was subjected to liquid-liquid extraction to separate aromatic hydrocarbons and alkanes according to the method of CN1277907C Example 3. The obtained 44.50 kg of raffinate oil was used as a steam cracking raw material, and the steam cracking reaction was carried out in the same manner as in Example 5. 22.92 kg of extracted oil and 32.58 kg of naphtha were used as catalytic reforming feeds, and catalytic reforming was carried out in the same manner as in Example 6. The results are shown in Table 7.

As can be seen from Table 7, compared with Comparative Example 6, the present invention uses naphtha as a raw material to produce a light olefin and a low benzene content gasoline. When the triene yield is substantially equivalent, the propylene production and butadiene production increase. C ₅ ⁺ gasoline production increased.

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3‧‧‧Hydrogenation reactor

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5‧‧‧ gas-liquid separation tank

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8‧‧‧Circle compressor

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13‧‧‧Extractive distillation tower

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30‧‧‧Restruction product distillation column

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Claims (14)

A method for producing olefin and low benzene content gasoline from naphtha comprises the following steps: (1) extractive distillation of naphtha to obtain extracted oil containing naphthenes and aromatics and a remnant containing alkanes and C ₆ naphthenes oil raffinate of naphtha and C ₆ cycloalkane ring of C ₆ paraffins mass ratio of 80 to 95%, (2) the extracted oil 0.01-3.0MPa, 300-600 ℃, a hydrogen / hydrocarbon The molar ratio is 0.5-20, the volumetric space velocity is 0.1-50 h-1, and the reforming catalyst is contacted to carry out the catalytic reforming reaction to obtain the reforming oil with low benzene content, and (3) the residual oil is sent. The steam cracker performs a cracking reaction to produce light olefins. The method of claim 1, wherein the mass ratio of the C ₆ naphthenes in the raffinate oil to the C ₆ naphthenes in the naphtha is 88 to 95%. The method of claim 1, wherein the extractive distillation described in the step (1) is carried out in an extractive distillation column, and the operating conditions of the extractive distillation column are: a solvent ratio of 1-10:1 and a column top temperature of 70 -190 ° C, pressure is 0.1-0.3 MPa. The method of claim 3, wherein the extractive distillation column has operating conditions of a solvent ratio of 3-8 and a column top temperature of 75-180 °C. The method of claim 1, wherein the extraction solvent used in the extractive distillation in (1) is selected from the group consisting of cyclobutyl hydrazine, dimethyl hydrazine, dimethylformamide, N-methylpyrrolidone, N-A. Porphyrin, triethylene glycol, tetragan Alcohol, pentaethylene glycol, methanol or acetonitrile. The method of claim 1, wherein in the step (1), the naphtha is subjected to hydrorefining prior to extractive distillation to saturate the olefin and remove impurities. The method of claim 1, wherein the extracted oil described in the step (2) is subjected to hydrotreating before the reforming reaction to saturate the olefin and remove impurities. The method of claim 6 or 7, wherein the sulfur content in the refined naphtha or the refined oil is less than 0.5 μg/g, the nitrogen content is less than 0.5 μg/g, the arsenic content is less than 1.0 ng/g, and the lead content is Less than 10 ng/g. For example, in the method of claim 1, wherein the catalytic reforming reaction pressure described in the step (2) is 0.2-2.0 MPa, the temperature is 350-520 ° C, and the volumetric space velocity is 1.0-30 h-1, hydrogen/hydrocarbon The molar ratio is 1-8:1. The method of claim 1, wherein the low benzene reforming oil produced in the step (2) is obtained by fractionating the catalytic reforming liquid product by a fractionation column. The method of claim 1, wherein the conditions of the cracking reaction in the step (3) are 0.05-0.30 MPa, the residence time of the reactant is 0.01-0.6 seconds, the water/oil mass ratio is 0.3-1.0, and the cracking furnace outlet temperature is 760. -900 ° C. The method of claim 1, wherein the naphtha is a hydrocarbon mixture having an initial boiling point of ASTM D-86 of 40-80 ° C and a final boiling point of 160-220 ° C. For example, the method of claim 1 of the patent scope, wherein the naphtha is selected From straight run naphtha, hydrocracked naphtha, coker naphtha, catalytic cracked naphtha or oil field condensate. The method of claim 1, wherein the naphtha contains 30 to 85% by mass of an alkane, 10 to 50% by mass of a cycloalkane, and 5 to 30% by mass of an aromatic hydrocarbon.