Liquefied petroleum gas-catalytic gasoline hydrogenation combined process

Abstract

The invention discloses a liquefied petroleum gas-catalytic gasoline hydrogenation combined process which comprises the following steps: (1) connecting a first fixed bed reactor and a second fixed bed reactor in series, and synchronously performing vulcanization treatment; after sulfuration is finished, keeping the concentration of CO2 in a reaction system not less than 3000mu g / g, introducing a catalytic gasoline raw material to react for a period of time, and switching to hydrogen; (2) the mixed material enters a first fixed bed reactor to react with a mercaptan transfer catalyst, and a first reactant flow is obtained; (3) carrying out gas-liquid separation on the first reactant flow to obtain a gas-phase product and a liquid-phase product, removing hydrogen sulfide from the gas-phase product to obtain a liquefied petroleum gas product, and fractionating the liquid-phase product to obtain light and heavy fractions; and (4) the heavy fraction and hydrogen enter a second fixed bed reactor to react with a selective hydrogenation catalyst to obtain a second reactant flow, and the second reactant flow is subjected to gas-liquid separation to obtain a heavy catalytic gasoline product. The process can efficiently and selectively hydrogenate liquefied gas and catalytic gasoline at the same time, reduces the investment cost of the device, reduces the hydrogen consumption, and improves the production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of clean oil refining, and in particular relates to a liquefied petroleum gas-catalytic gasoline hydrogenation combined process. Background Art

[0002] Liquefied petroleum gas mainly comes from catalytic cracking units and delayed coking units in refineries. It is a mixture of gaseous hydrocarbons. It can be used as a clean fuel or as a chemical raw material for producing high value-added products after separation and purification. However, liquefied petroleum gas contains a certain amount of sulfide impurities, especially methyl mercaptan and ethyl mercaptan, which will produce harmful SO during combustion. x It can also cause poisoning and deactivation of catalysts in downstream processing and promote oxidation of active hydrocarbons in liquefied petroleum gas to form colloids. Hydrodesulfurization technology can remove mercaptans from liquefied gas, but it can easily cause a large amount of olefin saturation, thereby reducing the utilization value of liquefied gas products.

[0003] Catalytic cracking gasoline has high sulfur and olefin contents. To achieve product quality upgrade of gasoline, traditional desulfurization technology saturates high-octane olefin components to produce low-octane alkanes, resulting in a significant decrease in octane number. In order to achieve the dual goals of deep desulfurization of FCC gasoline and minimize octane number loss, different processes and catalysts are used at home and abroad to achieve this goal.

[0004] IFP Prime-G + The technology consists of a selective hydrogenation unit (SHU), a fractionation tower (to separate LCN from MCN or HCN), and a dual catalyst hydrogenation unit for processing MCN and HCN. The process uses the full fraction of FCC gasoline as feedstock and performs hydrogenation pretreatment in the selective hydrogenation unit to hydrogenate and saturate the dienes and isomerize the double bonds; small molecular mercaptans and sulfides are converted into large molecular sulfides. Then, gasoline is separated into olefin-rich light gasoline and sulfur-rich heavy gasoline through fractionation; the sulfur-rich heavy gasoline is then subjected to selective deep hydrogenation and desulfurization using dual catalysts to minimize olefin saturation and obtain minimized octane number loss.

[0005] CN102311783B discloses a liquefied petroleum gas-coker gasoline hydrogenation combined process method: coker gasoline is subjected to hydrogenation reaction in a coker gasoline hydrogenation reaction section, the reaction effluent is mixed with a liquefied petroleum gas raw material and enters a liquefied petroleum gas hydrogenation reaction section, and then separated to obtain hydrogenated liquefied petroleum gas and hydrogenated coker gasoline. The method is conducive to the diffusion of reaction heat, reduces the reaction temperature, reduces the influence of temperature on the reaction equilibrium, and can simultaneously obtain high-quality hydrogenated coker gasoline and hydrogenated liquefied petroleum gas. CN109777506B discloses a combined processing method for hydrogenation of refinery gas, wherein the jet fuel feedstock oil and circulating oil are mixed with hydrogen in a hydrogenation device, and then enter the hydrogenation catalyst bed in the jet fuel hydrogenation reactor to react under liquid phase hydrogenation operation conditions; the obtained reactant stream is mixed with refinery gas and hydrogen in a gas dissolving device and then enters the hydrogenation catalyst bed in the supplementary hydrogenation reactor to react under liquid phase hydrogenation operation conditions; the hydrogenation reaction effluent is separated into a gas phase and a liquid phase, and the separated gas phase is further separated to obtain hydrogen, refinery gas, naphtha and jet fuel products after hydrogenation is removed. The above hydrogenation methods all firstly subject the liquid feedstock oil to hydrogenation reaction, and then mix it with liquefied gas for hydrogenation operation. Although the mercaptan in the liquefied gas can be removed, a large amount of olefin saturation is also produced, which reduces the utilization value of the liquefied gas product. CN103820149A discloses a method for reducing the sulfur content in liquefied gas, a mixing process of hydrogenated or unhydrogenated liquefied gas with other petroleum fractions with a higher boiling point than the liquefied gas; a hydrogenation reaction process including a thioetherification reaction of the liquefied gas or a mixed fraction containing liquefied gas in a fixed bed reactor; and a process of obtaining a low-sulfur liquefied gas fraction by fractionating the mixed fraction. The invention can greatly reduce the sulfur content in the liquefied gas, and the obtained low-sulfur liquefied gas fraction can be used to produce MTBE or alkylated gasoline (isooctane), but the process is limited to obtaining a low-sulfur liquefied gas fraction. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a liquefied petroleum gas-catalytic gasoline hydrogenation combined process, which can simultaneously perform efficient and selective hydrogenation on liquefied gas and catalytic gasoline, thereby achieving the simultaneous production of high-value liquefied gas products and gasoline products with low octane number loss, reducing equipment investment costs, lowering hydrogen consumption, improving production efficiency, and effectively solving the problem of large temperature rise during the liquefied gas hydrogenation process.

[0007] The liquefied petroleum gas-catalytic gasoline hydrogenation combined process of the present invention comprises the following contents: (1) A first fixed bed reactor and a second fixed bed reactor are connected in series, wherein the first fixed bed reactor is loaded with a mercaptan transfer catalyst, and the second fixed bed reactor is loaded with a selective hydrodesulfurization catalyst, and the two reactors are simultaneously subjected to sulfurization treatment; after the sulfurization is completed, CO2 is introduced into the two reactors to maintain the CO2 concentration in the reaction system ≮3000 μg / g, a catalytic gasoline raw material is introduced for reaction for a period of time, and then a hydrogen atmosphere is switched; (2) The catalytic gasoline raw material, liquefied petroleum gas and hydrogen are mixed in a first gas dissolving device, and the mixed material enters the first fixed bed reactor to react with the mercaptan transfer catalyst to obtain a first reaction stream; (3) The first reaction stream is subjected to gas-liquid separation to obtain a gas phase product and a liquid phase product, and the gas phase product is further desulfurized to obtain a liquefied petroleum gas product, and the liquid phase product is fractionated to obtain a light fraction and a heavy fraction; (4) The heavy fraction is mixed with hydrogen in a second gas dissolving device, and the mixed material enters the second fixed bed reactor to react with a selective hydrogenation catalyst to obtain a second reaction stream, and the second reaction stream is subjected to gas-liquid separation to obtain a heavy catalytic gasoline product.

[0008] In the process of the present invention, before the sulfurization treatment in step (1), the first and second fixed bed reactors have completed conventional operations before the sulfurization treatment, such as nitrogen gas-tightness, catalyst drying, hydrogen replacement, hydrogen gas-tightness and establishment of hydrogen circulation.

[0009] In the process of the present invention, the sulfurization treatment conditions in step (1) are as follows: the amount of the introduced sulfurizing agent is 90% to 150% of the theoretical sulfur requirement of the catalyst; the sulfurization process adopts programmed temperature rise, the temperature is raised to 200 to 230° C. and kept constant for 4 to 16 hours, and then kept constant at 260 to 290° C. for 4 to 16 hours; the sulfurizing agent is generally one or more of carbon disulfide, dimethyl disulfide, methyl sulfide, and n-butyl sulfide.

[0010] In the process of the present invention, the amount of CO2 introduced in step (1) is ≮3000 μg / g, preferably ≮6000 μg / g, based on its concentration in hydrogen.

[0011] In the process of the present invention, the amount of the catalytic gasoline raw material introduced in step (1) is 2 to 10 h / min. -1 , preferably a volume space velocity of 4 to 8 h -1 The reaction time is 48 to 600 hours, preferably 72 to 480 hours, the inlet temperature of the first fixed bed reactor is 180 to 220°C, preferably 190 to 210°C; the inlet temperature of the second fixed bed reactor is 280 to 320°C, preferably 290 to 310°C.

[0012] In the process of the present invention, after the sulfurization in step (2) is completed, the concentration of hydrogen sulfide in the hydrogen is generally replaced by hydrogen circulation ≯ 300 mg / m 3 , preferably ≯100mg / m 3 .

[0013] In the process of the present invention, the CO2 content in the hydrogen atmosphere of step (1) is generally ≯20 μg / g, preferably ≯10 μg / g.

[0014] In the process of the present invention, the catalytic gasoline feedstock described in step (2) includes fresh catalytic gasoline feedstock and circulating oil, wherein the properties of the fresh catalytic gasoline feedstock are as follows: sulfur content of 100-2000 μg / g, olefin content of 20v%-60v%.

[0015] In the process of the present invention, the liquefied petroleum gas described in step (2) comes from a catalytic cracking unit and a delayed coking unit of a refinery, and has a sulfur content of 10 to 300 μg / g and an olefin content of 20 v% to 80 v%.

[0016] In the process of the present invention, the first gas dissolving device described in step (2) is any mixing device that can achieve a premixing effect on the catalytic gasoline raw material, liquefied petroleum gas and hydrogen. The mixing device is one or more of a static mixer, a gas dissolving pump, a mechanical stirring device, a colloid mill, a microporous plate nano / micro hydrogen dispersion component, a micro bubble generator, a ceramic membrane nano / micro hydrogen dispersion component, a jet mixer and a microchannel mixer.

[0017] In the process of the present invention, the mercaptan transfer conditions in step (2) are as follows: the reaction pressure is 1.0-4.0 MPa, preferably 1.6-3.2 MPa, the reaction temperature is 90-200°C, preferably 110-180°C, the volume space velocity of the catalytic gasoline raw material and the liquefied petroleum gas raw material is 1.0-10.0 h -1 , preferably 2.0~8.0h -1 The volume ratio of hydrogen to the catalytic gasoline raw material and the liquefied petroleum gas raw material is 100: 1 to 1: 1, preferably 50: 1 to 1: 1, and the volume ratio of the catalytic gasoline raw material to the liquefied petroleum gas is 0.5: 1 to 20: 1, preferably 2: 1 to 10: 1.

[0018] In the process of the present invention, the mercaptan transfer catalyst described in step (2) can be a catalyst with mercaptan transfer function well known in the art, and can be selected from commercial products or prepared according to existing technologies, such as ExxonMobil's HR-845 catalyst. The mercaptan transfer catalyst generally includes a hydrogenation active component and a catalyst carrier, wherein the hydrogenation active component includes molybdenum and nickel, and the weight content of molybdenum and nickel as oxides is 3% to 40%, and the catalyst carrier is aluminum oxide, amorphous silicon aluminum, silicon oxide, titanium oxide, etc., and can also contain other additives, such as P, Si, B, Ti, Zr, Ca, etc.

[0019] In the process of the present invention, the gas phase product obtained in step (3) is passed through a gas separator to remove hydrogen sulfide, and then hydrogen is separated to obtain a liquefied petroleum gas product.

[0020] In the process of the present invention, the fractionation in step (3) is generally carried out in a fractionation device, such as a fractionation tower, wherein any liquid product in the gas separator directly enters the fractionation device and is fractionated into a light fraction and a heavy fraction together with the separated liquid product.

[0021] In the process of the present invention, the liquid product and / or part of the light fraction obtained in step (3) is returned to the first gas dissolving device as circulating oil; the volume ratio of the circulating oil to the fresh catalytic gasoline feedstock is 1:10-2:1, preferably 1:5-1:1.

[0022] In the process of the present invention, the second gas dissolving device in step (4) is any mixing device that can make the catalytic gasoline raw material and hydrogen have a premixing effect. The mixing device is one or more of a static mixer, a gas dissolving pump, a mechanical stirring device, a colloid mill, a microporous plate nano / micro hydrogen dispersion component, a micro bubble generator, a ceramic membrane nano / micro hydrogen dispersion component, a jet mixer, and a microchannel mixer.

[0023] In the process of the present invention, the selective hydrogenation reaction conditions in step (4) are as follows: the reaction pressure is 1.0-4.0 MPa, preferably 1.6-3.2 MPa, the reaction temperature is 230-320°C, preferably 250-300°C, the volume space velocity of heavy catalytic gasoline is 1.0-10.0 h -1 , preferably 2.0~6.0h -1 The mass ratio of hydrogen to heavy fraction is 200:1 to 10:1, preferably 100:1 to 50:1.

[0024] In the process of the present invention, the selective hydrogenation catalyst described in step (4) can be a catalyst with a selective hydrodesulfurization function well known in the art, and can be selected from commercial products or prepared according to existing technologies, such as RT-225 of Axens, HR-806 catalyst of ExxonMobil, FGH-21 and FGH-31 catalysts of Sinopec (Dalian) Petrochemical Co., Ltd., etc. The selective hydrogenation catalyst generally includes a hydrogenation active component and a catalyst carrier, wherein the hydrogenation active component is at least one VIB group metal molybdenum and at least one VIII group metal cobalt, and the weight content of molybdenum and cobalt in terms of oxide is 4% to 40%, and the catalyst carrier is generally alumina, amorphous silicon aluminum, silicon oxide, titanium oxide, etc., and can also contain other additives, such as P, Si, B, Ti, Zr, Ca, etc.

[0025] In the process of the present invention, part of the heavy catalytic gasoline product obtained in step (4) is returned to the second gas dissolving device as circulating oil, and the circulating mass ratio is 1:10-2:1, preferably 1:5-1:1.

[0026] In the process of the present invention, the uncirculated light fraction in step (3) is mixed with the heavy catalytic gasoline product obtained in step (4) to obtain the finished catalytic gasoline.

[0027] In the existing technology, although the hydrodesulfurization technology can be used to remove mercaptans from liquefied petroleum gas, it is easy to cause a large amount of olefin saturation, thereby reducing the utilization value of the liquefied gas product. Catalytic cracking gasoline has high sulfur and olefin content. To achieve the product quality upgrade of gasoline, the traditional desulfurization technology saturates the high-octane olefin components to generate low-octane alkanes, resulting in a significant decrease in octane number.

[0028] The present invention provides a liquefied petroleum gas-catalytic gasoline combined process, which can selectively hydrogenate liquefied gas and catalytic gasoline at the same time, and can realize the simultaneous production of high-value liquefied gas products and gasoline products with low octane number loss. The inventor compares the common points of liquefied petroleum gas and catalytic gasoline hydrogenation, and in view of the fact that both liquefied petroleum gas and catalytic gasoline have the requirements of desulfurization and less saturated olefins, adopts a hydrogen-dissolving method to meet the amount of hydrogen used for hydrodesulfurization as much as possible, and does not provide too much hydrogen to cause oversaturation of olefins, and adopts two catalysts with different functions to hydrogenate and saturate dienes and isomerize double bonds in a mercaptan transfer reactor through a mercaptan transfer catalyst; small molecular mercaptans and sulfides are converted into large molecular sulfides, and a product liquefied petroleum gas with low sulfur and low olefin loss is obtained through a separation system, and the separated liquid phase is fractionated into light catalytic gasoline and heavy catalytic gasoline, and the heavy catalytic gasoline enters a gasoline selective hydrogenation reactor, and reacts through a heavy catalytic gasoline selective hydrogenation catalyst, and the sulfur-rich heavy gasoline is selectively deeply hydrodesulfurized, and the minimized olefin saturation is obtained to obtain the minimized octane number loss. The inventors also adopted a special sulfurization start-up method. After the sulfurization is completed, a large amount of acidic CO2 molecules are adsorbed on the active sites of the catalyst hydrodesulfurization reaction, and catalytic gasoline raw materials are introduced at a relatively high reaction temperature to accelerate the formation of carbon deposits on the catalyst. The characteristics of the catalyst hydrodesulfurization reaction and the olefin hydrogenation saturation reaction on the catalyst have different active sites. The carbon deposits are more covered on the active sites of the olefin hydrogenation saturation reaction, thereby reducing the activity of the olefin hydrogenation saturation reaction. When the CO2 content in the hydrogen is restored to ≯20μg / g, the adsorption of CO2 molecules on the catalyst is recoverable, and the hydrodesulfurization reaction activity of the catalyst is restored again, but at this time, the olefin hydrogenation saturation reaction activity of the catalyst has been suppressed, thereby greatly improving the selectivity of liquefied gas and catalytic gasoline hydrodesulfurization. The integrated processing method of the two raw oils reduces the investment cost of the device, improves production efficiency, and effectively solves the problem of large temperature rise in the process of liquefied gas hydrogenation. Hydrogenation by dissolving hydrogen reduces hydrogen consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The present invention is a flow chart of the liquefied petroleum gas-catalytic gasoline hydrogenation combined process.

[0030] Wherein: 1-catalytic gasoline raw oil, 2-raw oil pump, 3-liquefied petroleum gas raw material, 4-hydrogen, 5-first gas dissolving equipment, 6-first fixed bed reactor, 7-pressure reducing valve, 8-first reaction flow gas-liquid separator, 9-part of the first reaction flow liquid phase product, 10-check valve, 11-gas phase product, 12-gas separator, 13-separated hydrogen, 14-liquefied petroleum gas product, 15-liquid phase product, 16-fractionation tower, 17-light catalytic gasoline product obtained by fractionation, 18-part of the light catalytic gasoline product obtained by fractionation, 19-check valve, 20-heavy catalytic gasoline obtained by fractionation, 21-heavy catalytic gasoline raw material pump, 22-second gas dissolving equipment, 23-second fixed bed reactor, 24-pressure reducing valve, 25-second reaction flow gas-liquid separator, 26-heavy catalytic gasoline product, 27-part of the second reaction flow separation to obtain liquid phase product, 28-check valve, 29-second reaction flow separation to obtain gas phase product. DETAILED DESCRIPTION

[0031] The following examples are used to specifically illustrate the process and effects of the combined process of liquefied petroleum gas-catalytic gasoline hydrogenation of the present invention, but they do not constitute a limitation to the method of the present invention.

[0032] The mercaptan transfer catalyst is a catalyst with aluminum oxide as a carrier, metal molybdenum and metal nickel as hydrogenation active components, and the total amount of molybdenum and nickel metals calculated as oxides is 20wt%. The heavy catalytic gasoline selective hydrogenation catalyst is a catalyst with aluminum oxide as a carrier, metal molybdenum and metal cobalt as hydrogenation active components, and the total amount of molybdenum and cobalt metals calculated as oxides is 16wt%. Table 1 shows the properties of liquefied petroleum gas raw materials, and Table 2 shows the properties of catalytic gasoline raw materials.

[0033] Table 1 Properties of liquefied petroleum gas raw materials composition content Sulfur content, μg / g 38 Ethane, % (V / V) 0.6 Ethylene, % (V / V) 0.1 Propane, % (V / V) 9.76 Propylene, % (V / V) 39.47 Butane, % (V / V) 20.91 Butene, % (V / V) 28.91 Butadiene, % (V / V) 0.07 <![CDATA[C5 + , % (V / V)]]> 0.27 Table 2 Properties of FCC gasoline feedstock project Catalytic gasoline Octane number, RON 94.1 Sulfur content, μg / g 417.1 Diene, % 1.14 Multidimensional chromatographic composition Olefins, % 36.9 Example 1

[0034] During the sulfidation process, the CO2 content in the hydrogen was controlled at 5μg / g. After the hydrogen circulation was established, the inlet temperature of the first and second fixed bed reactors was raised to 230℃, and the sulfidation was carried out at a constant temperature for 8 hours. Then the inlet temperature of the reactor was raised to 280℃, and the sulfidation was carried out at a constant temperature for 8 hours. The H2S concentration of the circulating hydrogen was 11000mg / m 3 ; After the sulfidation is completed, the concentration of hydrogen sulfide in the replaced hydrogen is 90mg / m 3 ,CO2 content 6900μg / g, catalytic gasoline raw material is introduced, and the volume space velocity is 6h -1, the inlet temperature of the first fixed bed reactor is controlled at 190°C, and the inlet temperature of the second fixed bed reactor is controlled at 300°C; after the catalytic gasoline raw material is introduced for 240 hours, the CO2 content in the hydrogen is restored to control 5μg / g, and the inlet temperature of the first and second fixed bed reactors drops to the actual reaction temperature for normal production. The catalytic gasoline raw material 1 is mixed with the liquefied petroleum gas raw material 3 and hydrogen 4 in the first gas dissolving device 5 through the raw material pump 2 and then enters the first fixed bed reactor 6 for reaction. The reaction pressure is 2.3MPa, the reaction temperature is 150°C, and the volume space velocity of the catalytic gasoline raw material and the liquefied petroleum gas raw material is 5h -1 The volume ratio of hydrogen to catalytic gasoline raw material and liquefied petroleum gas raw material is 150: 1, and the volume ratio of catalytic gasoline raw material to liquefied petroleum gas is 4: 1. The reaction effluent enters the first reactor logistics gas-liquid separator 9 through the pressure reducing valve 7, and part of the first reactor effluent logistics liquid phase product 15 is returned to the raw material oil pump 2 through the one-way valve 10. The volume ratio of circulating oil to fresh catalytic gasoline raw material is 1: 3. The gas phase product 11 enters the gas separator 12 and is separated to obtain separated hydrogen 13 and liquefied petroleum gas product 14. The liquid phase product 15 is fractionated by the fractionation tower 16 to obtain light catalytic gasoline product 17. The light catalytic gasoline product 18 obtained by partial distillation is returned to the raw material oil pump 2 through the one-way valve 19. The heavy catalytic gasoline 20 obtained by fractionation is mixed with the heavy catalytic gasoline raw material pump 21 and hydrogen 4 in the second gas dissolving device 22 and then enters the second fixed bed reactor 23. The reaction pressure is 1.6MPa, the reaction temperature is 260℃, and the volume space velocity of the heavy catalytic gasoline is 3.0h -1 The mass ratio of hydrogen to heavy fraction is 70:1. The product enters the second reaction stream gas-liquid separator 25 through the pressure reducing valve 24 to obtain the heavy catalytic gasoline product 26. The liquid product 27 obtained by separation of part of the second reaction stream is returned to the heavy catalytic gasoline feed pump 21 through the one-way valve 28. The gas product 29 obtained by separation of the effluent from the second reactor enters the gas separator 12. The light catalytic gasoline product 17 is mixed with the heavy catalytic gasoline product 26 to obtain the finished catalytic gasoline. Example 2

[0035] All implementation processes are the same as in Example 1, except that the CO2 content in the hydrogen is controlled at 10 μg / g during the sulfurization process, and 5000 μg / g after the sulfurization is completed. The inlet temperature of the first fixed bed reactor is controlled at 200°C, and the inlet temperature of the second fixed bed reactor is controlled at 290°C. After the catalytic gasoline feedstock is introduced for 360 hours, the CO2 content in the hydrogen is restored to 10 μg / g. The volumetric space velocity of the catalytic gasoline feedstock and the liquefied petroleum gas feedstock in the first fixed bed reactor is 0.5h -1The volume ratio of hydrogen to FCG feedstock and LPG feedstock is 12:1, and the volume ratio of FCG feedstock to LPG is 3:1. The mass ratio of circulating oil to fresh FCG feedstock is 1:15. The volumetric space velocity of the mixed material in the second fixed bed reactor is 2.5h -1 The mass ratio of hydrogen to heavy fraction is 90:1.

[0036] Comparative Example 1 All implementation processes are the same as in Example 1, except that the inlet temperature of the first fixed bed reactor is controlled at 160°C and the inlet temperature of the second fixed bed reactor is controlled at 260°C during the stabilization process; after the catalytic gasoline raw material is introduced for 36 hours, the volume space velocity of the catalytic gasoline raw material and the liquefied petroleum gas raw material in the first fixed bed reactor is 6h -1 The volume ratio of hydrogen to FCG feedstock and LPG feedstock is 12:1, and the volume ratio of FCG feedstock to LPG is 25:1. The mass ratio of circulating oil to fresh FCG feedstock is 1:4. The volumetric space velocity of the mixed material in the second fixed bed reactor is 12h -1 The mass ratio of hydrogen to heavy fraction is 500:1.

[0037] Comparative Example 2 All implementation processes are the same as in Example 1, except that the CO2 content after sulfurization is 5 μg / g.

[0038] Table 3 Comparison results of liquefied petroleum gas and catalytic gasoline project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Liquefied petroleum gas product properties Sulfur content, μg / g 1.6 1.8 2.8 1.5 Ethane, % (V / V) 0.7 0.6 0.9 0.8 Ethylene, % (V / V) 0 0 0 0 Propane, % (V / V) 10.22 10.18 14.23 12.26 Propylene, % (V / V) 39.07 39.19 35.06 37.07 Butane, % (V / V) 21.29 21.21 19.20 23.39 Butene, % (V / V) 28.59 28.63 26.57 26.50 Butadiene, % (V / V) 0.01 0.01 0.01 0.01 <![CDATA[C5 + , %(V / V)]]> 0.21 0.22 0.28 0.11 Catalytic gasoline product properties Octane number, RON 93.0 92.9 92.0 92.4 Sulfur content, μg / g 7.1 7.2 12.1 6.8 Diene, % 0.17 0.19 0.15 0.13 Multidimensional chromatographic composition Olefins, % (V / V) 34.8 34.7 32.6 33.6 It can be seen from the comparison results of the embodiments and the comparative examples in Table 3 that only by adopting the combined hydrogenation process of the present invention for liquefied petroleum gas and catalytic gasoline can a high-value liquefied gas product and a gasoline product with a small octane loss be produced simultaneously.

Claims

1. A liquefied petroleum gas-catalytic gasoline hydrogenation combined process, comprising the following contents: (1) a first fixed bed reactor and a second fixed bed reactor are connected in series, wherein the first fixed bed reactor is loaded with a mercaptan transfer catalyst, and the second fixed bed reactor is loaded with a selective hydrodesulfurization catalyst, and the two reactors are simultaneously subjected to sulfurization treatment; after the sulfurization is completed, CO2 is introduced into the two reactors to maintain the CO2 concentration in the reaction system ≮3000 μg / g, and catalytic gasoline raw materials are introduced for reaction for a period of time, and then switched to hydrogen atmosphere; (2) the catalytic gasoline raw materials, liquefied petroleum gas and hydrogen are mixed in a reaction system; The first reaction stream is subjected to gas-liquid separation to obtain a gas phase product and a liquid phase product, and the gas phase product is further subjected to hydrogen sulfide removal to obtain a liquefied petroleum gas product, and the liquid phase product is subjected to fractionation to obtain a light fraction and a heavy fraction; (4) the heavy fraction is mixed with hydrogen in a second gas dissolving device, and the mixed material is fed into a second fixed bed reactor to react with a selective hydrogenation catalyst to obtain a second reaction stream, and the second reaction stream is subjected to gas-liquid separation to obtain a heavy catalytic gasoline product.

2. The method according to claim 1, characterized in that: Before the sulfurization treatment in step (1), the first and second fixed bed reactors have completed nitrogen gas-tightness, catalyst drying, hydrogen replacement, hydrogen gas-tightness and establishment of hydrogen circulation.

3. The method according to claim 1, characterized in that: The sulfurization treatment conditions in step (1) are as follows: the amount of the introduced sulfurizing agent is 90wt%~150wt% of the theoretical sulfur requirement of the catalyst; the sulfurization process adopts programmed temperature rise, the temperature is raised to 200~230℃ and kept constant for 4~16h, and then kept constant at 260~290℃ for 4~16h; the sulfurizing agent is one or more of carbon disulfide, dimethyl disulfide, methyl sulfide, and n-butyl sulfide.

4. The method according to claim 1, characterized in that: The amount of CO2 introduced in step (1) is ≮3000 μg / g, preferably ≮6000 μg / g, based on its concentration in hydrogen.

5. The method according to claim 1, characterized in that: The amount of catalytic gasoline raw material introduced in step (1) is 2 to 10 h / min. -1 , preferably a volume space velocity of 4 to 8 h -1 The reaction time is 48 to 600 hours, preferably 72 to 480 hours, and the inlet temperature of the first fixed bed reactor is 180 to 220° C., preferably 190 to 210° C.; The inlet temperature of the second fixed bed reactor is 280-320°C, preferably 290-310°C.

6. The method according to claim 1, characterized in that: Step (2) After the sulfidation is completed, the hydrogen sulfide concentration in the hydrogen is generally replaced by hydrogen circulation ≯ 300 mg / m 3 , preferably ≯100mg / m 3 .

7. The method according to claim 1, characterized in that: In the hydrogen atmosphere of step (1), the CO2 content is ≯20 μg / g, preferably ≯10 μg / g.

8. The method according to claim 1, characterized in that: The catalytic gasoline raw material in step (2) comprises fresh catalytic gasoline raw material and circulating oil, wherein the properties of the fresh catalytic gasoline raw material are as follows: sulfur content of 100-2000 μg / g, olefin content of 20v%-60v%.

9. The method according to claim 1, characterized in that: The liquefied petroleum gas in step (2) has a sulfur content of 10-300 μg / g and an olefin content of 20 v%-80 v%.

10. The method according to claim 1, characterized in that: The first gas dissolving device described in step (2) is any mixing device that can premix the catalytic gasoline raw material, liquefied petroleum gas and hydrogen, preferably one or more of a static mixer, a gas dissolving pump, a mechanical stirring device, a colloid mill, a microporous plate nano / micro hydrogen dispersion component, a micro bubble generator, a ceramic membrane nano / micro hydrogen dispersion component, a jet mixer and a microchannel mixer.

11. The method according to claim 1, characterized in that: The mercaptan transfer conditions in step (2) are as follows: reaction pressure of 1.0-4.0 MPa, preferably 1.6-3.2 MPa, reaction temperature of 90-200°C, preferably 110-180°C, and mixed material volume space velocity of 1.0-10.0 h -1 , preferably 2.0~8.0h -1 The volume ratio of hydrogen to the catalytic gasoline raw material and the liquefied petroleum gas raw material is 100: 1 to 1: 1, preferably 50: 1 to 1: 1, and the volume ratio of the catalytic gasoline raw material to the liquefied petroleum gas is 0.5: 1 to 20: 1, preferably 2: 1 to 10:

1.

12. The method according to claim 1, characterized in that: The mercaptan transfer catalyst in step (2) is a catalyst with mercaptan transfer function well known in the art; the mercaptan transfer catalyst comprises a hydrogenation active component and a catalyst carrier, wherein the hydrogenation active component comprises molybdenum and nickel, and the weight content of molybdenum and nickel as oxides is 3% to 40%, and the catalyst carrier is one or more of aluminum oxide, amorphous silicon aluminum, silicon oxide, and titanium oxide; the mercaptan transfer catalyst may contain one or more additives selected from P, Si, B, Ti, Zr, and Ca.

13. The method according to claim 1, characterized in that: The gas phase product obtained in step (3) is passed through a gas separator to remove hydrogen sulfide and separate hydrogen to obtain a liquefied petroleum gas product.

14. The method according to claim 1, characterized in that: The fractionation in step (3) is carried out in a fractionation device, wherein any liquid product in the gas separator directly enters the fractionation device and is fractionated into a light fraction and a heavy fraction together with the separated liquid product.

15. The method according to claim 1, characterized in that: The liquid product and / or part of the light fraction obtained in step (3) is returned to the first gas dissolving device as circulating oil; the volume ratio of the circulating oil to the fresh catalytic gasoline feedstock is 1:10-2:1, preferably 1:5-1:

1.

16. The method according to claim 1, characterized in that: The second gas dissolving equipment described in step (4) adopts one or more of a static mixer, a gas dissolving pump, a mechanical stirring device, a colloid mill, a microporous plate nano / micro hydrogen dispersion component, a micro bubble generator, a ceramic membrane nano / micro hydrogen dispersion component, a jet mixer and a microchannel mixer.

17. The method according to claim 1, characterized in that: The selective hydrogenation reaction conditions in step (4) are as follows: reaction pressure of 1.0-4.0 MPa, preferably 1.6-3.2 MPa, reaction temperature of 230-320°C, preferably 250-300°C, and volume space velocity of heavy catalytic gasoline of 1.0-10.0 h -1 , preferably 2.0~6.0h -1 The mass ratio of hydrogen to heavy fraction is 200:1 to 10:1, preferably 100:1 to 50:

1.

18. The method according to claim 1, characterized in that: The selective hydrogenation catalyst in step (4) is a catalyst with a selective hydrogenation desulfurization function well known in the art; the selective hydrogenation catalyst comprises a hydrogenation active component and a catalyst carrier, wherein the hydrogenation active component is at least one VIB group metal molybdenum and at least one VIII group metal cobalt, the weight content of molybdenum and cobalt as oxides is 4% to 40%, and the catalyst carrier is one or more of aluminum oxide, amorphous silicon aluminum, silicon oxide, and titanium oxide; the selective hydrogenation catalyst may contain one or more additives selected from P, Si, B, Ti, Zr, and Ca.

19. The method according to claim 1, characterized in that: The heavy catalytic gasoline product obtained in step (4) is partially returned to the second gas dissolving device as circulating oil, and the circulating mass ratio is 1:10 to 2:1, preferably 1:5 to 1:

1.

20. The method according to claim 1, characterized in that: The uncirculated light fraction in step (3) is mixed with the heavy catalytic gasoline product obtained in step (4) to obtain the finished catalytic gasoline.

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