Method for hydrodesulfurization of liquefied petroleum gas

Abstract

The application discloses a liquefied petroleum gas hydrodesulfurization method, which comprises the following steps: (1) carrying out gas fractionation on a liquefied petroleum gas raw material to obtain a C3 fraction and a C4 fraction; (2) contacting the C3 fraction and the C4 fraction with a hydrodesulfurization catalyst in liquid form respectively to carry out a hydrodesulfurization reaction, and hydrogenating sulfides in each fraction into hydrogen sulfide; wherein the C3 fraction is subjected to a high-temperature hydrodesulfurization reaction, and the C4 fraction is subjected to a low-temperature hydrodesulfurization reaction; and (3) carrying out alcohol amine absorption on hydrodesulfurization reaction effluents of the C3 fraction and the C4 fraction to remove hydrogen sulfide, and obtaining a refined liquefied petroleum gas product. The method matches the reaction fraction composition with the reaction process, accurately controls the reaction, and avoids the loss of olefins of the liquefied petroleum gas during the hydrodesulfurization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of liquefied petroleum gas desulfurization, and particularly relates to a liquefied petroleum gas hydrodesulfurization method. BACKGROUND

[0002] The devices such as atmospheric-vacuum distillation, catalytic cracking, delayed coking, catalytic reforming and hydrocracking of oil refineries will produce a large amount of liquefied petroleum gas. Traditionally, liquefied petroleum gas is mainly used as fuel; with the development of chemical technology, liquefied petroleum gas, especially catalytic cracking liquefied petroleum gas containing a large amount of olefins, is more and more used in the chemical field, such as polypropylene production, MTBE production, alkylation process and the like. The main components of liquefied petroleum gas are propane, propylene, butane and butene, etc., and some sulfides are also contained in untreated liquefied petroleum gas. The molecular weight of the sulfides contained in liquefied petroleum gas is generally small and harmful, and the main components are hydrogen sulfide, carbonyl sulfide, mercaptan and sulfide, etc.

[0003] The traditional liquefied petroleum gas double desulfurization process is mainly Merox sweetening process, and one of the shortcomings of double desulfurization (H2S removal and mercaptan removal) is that mercaptan (RSH) is only oxidized to disulfide (RSSR), and the total sulfur content is not reduced or is limitedly reduced; the other shortcoming is that the regenerated organic waste gas and alkali residue generated by the desulfurization device are both environmental pollutants difficult to be treated, and there are hidden dangers in environmental protection or safety.

[0004] CN200910233505.1 introduces a high-efficiency desulfurizer for high-acid petroleum and natural gas. The main feature is to add a water-soluble nitrogen-containing organic solvent (alkaline nitrogen content ≥ 100 g / L) to the fiber membrane reactor for desulfurization. The advantage is that the desulfurization rate is higher than that of the traditional alkanolamine method (such as N-methyldiethanolamine, MDEA); the disadvantage is that the nitrogen-containing organic solvent needs to be regenerated repeatedly, and the heat exchange process is complex and the energy consumption is high.

[0005] CN104194833A introduces a deep desulfurization process for liquefied petroleum gas, which is characterized in that the liquefied petroleum gas is first extracted by amine liquid to remove H2S, and the amine liquid carried is removed by water washing; then the sulfides in the liquefied petroleum gas are converted into high-boiling sulfides on the sulfided Mo-Ni / γ-Al2O3 catalyst; the hydrogenation product enters the stabilizing tower, and the low-sulfur carbon five or above fraction is used for rectification separation to obtain an ultra-low-sulfur liquefied petroleum gas product, which can be used as a low-sulfur raw material for producing MTBE or alkylation.

[0006] CN103965984A introduces a liquefied petroleum gas catalytic desulfurization method, its characteristics are that the liquefied petroleum gas is mixed with hydrogen and then enters a fixed bed reactor, and sulfidation reaction is carried out with the Ni-Mo / γ-Al2O3 catalyst or Ni-W / γ-Al2O3 catalyst filled therein, low-boiling-point mercaptans are converted into high-boiling-point sulfide compounds, then the sulfidation reaction product is subjected to distillation treatment in a distillation column, and the liquefied petroleum gas product without mercaptans is obtained.The disadvantage is that only the liquefied petroleum gas treated by removing hydrogen sulfide and carbonyl sulfide can be treated, the distillation column needs a reboiler, and the energy consumption is high.The existing hydrogenation desulfurization method inevitably causes certain olefin loss while desulfurizing. SUMMARY

[0007] In view of the deficiencies in the prior art, the present application provides a liquefied petroleum gas hydrogenation desulfurization method, which matches the reaction fraction composition with the reaction process, accurately controls the reaction, and avoids olefin loss while liquefied petroleum gas hydrogenation desulfurization.

[0008] The liquefied petroleum gas hydrogenation desulfurization method of the present application comprises the following contents:

[0009] (1) gas fractionation is carried out on the liquefied petroleum gas raw material to obtain C3 fraction and C4 fraction;

[0010] (2) the C3 fraction and the C4 fraction are respectively contacted with a hydrogenation desulfurization catalyst in liquid form to carry out hydrogenation desulfurization reaction, and sulfides in each fraction are hydrogenated to generate hydrogen sulfide; wherein the C3 fraction is subjected to first hydrogenation desulfurization reaction, and the C4 fraction is subjected to second hydrogenation desulfurization reaction;

[0011] (3) alcohol amine absorption is carried out on the hydrogenation desulfurization reaction effluent of the C3 fraction and the C4 fraction to remove hydrogen sulfide, and a refined liquefied petroleum gas product is obtained.

[0012] In the method of the present application, the liquefied petroleum gas raw material in step (1) is catalytic cracking (FCC) liquefied petroleum gas, coking liquefied petroleum gas, natural liquefied petroleum gas, etc., preferably catalytic cracking (FCC) liquefied petroleum gas, and the typical composition is propylene content of 20.0v% to 40.0v%, butene content of 10.0v% to 30.0v%, total sulfur content of 100 to 5000 mg / m 3 , hydrogen sulfide content of 50 to 5000 mg / m 3 , carbonyl sulfide content of 10 to 50 mg / m 3 , methyl mercaptan sulfur content of 50 to 500 mg / m 3 , and ethyl mercaptan sulfur content of 50 to 500 mg / m 3 .

[0013] The gas fractionation operation in step (1) is well known to those skilled in the art and is generally carried out in a gas fractionation unit.

[0014] In the method of the present application, the C3 fraction in step (2) mainly comprises hydrogen sulfide, propane, propylene, carbonyl sulfur, wherein the propylene content is 50.0v% to 80.0v%, the hydrogen sulfide content is 50 to 5000 mg / m 3 , and the carbonyl sulfur content is 10 to 100 mg / m 3 .

[0015] In the method of the present application, the first hydrodesulfurization reaction conditions in step (2) are as follows: the reaction pressure is 0.5 to 1.6 MPa, the reaction temperature is 150 to 250℃, the liquid petroleum gas feed volume space velocity is 0.2 to 20.0 h -1 , and the hydrogen hydrocarbon (hydrogen and C3 fraction) volume ratio is 0.1 to 20:1; preferably, the operation conditions are as follows: the reaction pressure is 0.5 to 1.0 MPa, the reaction temperature is 150 to 200℃, the liquid petroleum gas feed volume space velocity is 0.2 to 10.0 h -1 , and the hydrogen hydrocarbon volume ratio is 0.1 to 10:1.

[0016] In the method of the present application, the first hydrodesulfurization catalyst used in the first hydrodesulfurization reaction in step (2) is a catalyst capable of hydrodesulfurizing carbonyl sulfur; for example, a Ni-Mo / γ-Al2O3 or Ni-W / γ-Al2O3 supported hydrodesulfurization catalyst is used, wherein the content of NiO is 5.0wt% to 20.0wt%, preferably 5.0wt% to 10.0wt%, based on the weight of the catalyst; and the content of MoO3 or WO3 is 3.0wt% to 14.0wt%, preferably 3.0wt% to 10.0wt%.

[0017] In the method of the present application, the first hydrodesulfurization catalyst in step (2) needs to be pre-sulfurized by using a conventional sulfurization method before use, so as to convert the metal oxide active precursor into a sulfide active phase with catalytic activity; the pre-sulfurization of the catalyst can be carried out by in-situ sulfurization and ex-situ sulfurization, and the sulfurizing agent can be selected from dimethyl disulfide, hydrogen sulfide, carbon disulfide and other sulfur compounds.

[0018] In the method of the present application, the C4 fraction in step (2) mainly comprises butane, butene, methyl mercaptan, ethyl mercaptan and the like, wherein the butene content is 40.0v% to 60.0v%, the methyl mercaptan content is 50 to 500 mg / m 3 , and the ethyl mercaptan content is 50 to 500 mg / m 3 .

[0019] The second hydrodesulfurization reaction condition in step (2) in the method of the present application is as follows: reaction pressure is 0.5-2.5 MPa, reaction temperature is 20-100℃, liquid gas feed volume space velocity is 0.1-20.0 h -1 -1, hydrogen hydrocarbon (hydrogen and C4 fraction) volume ratio is 0.1-20:1; preferred operating conditions are as follows: reaction pressure is 1.0-2.5 MPa, reaction temperature is 20-80℃, feed volume space velocity is 0.1-10.0 h -1 -1, hydrogen hydrocarbon (hydrogen and C4 fraction) volume ratio is 0.1-20:1; preferred operating conditions are as follows: reaction pressure is 1.0-2.5 MPa, reaction temperature is 20-80℃, feed volume space velocity is 0.1-10.0 h

[0020] The second hydrodesulfurization catalyst used in the second hydrodesulfurization reaction in step (2) in the method of the present application comprises a composite oxide carrier and an active metal component, the composite oxide carrier is graphene oxide-ZnO-Al2O3, wherein the graphene oxide is distributed on the surface of zinc oxide and aluminum oxide; the mass fraction of zinc oxide is 20.0%-90.0%, preferably 50.0%-70.0%, the content of graphene oxide is 0.1wt%-10.0wt%, preferably 0.5wt%-8.0wt%, and the balance is aluminum oxide; the active metal component is CuO and / or NiO; the content of CuO and / or NiO is 5.0wt%-20.0wt%, preferably 5.0wt%-10.0wt%, based on the weight of the catalyst, and the balance is the composite oxide carrier; the specific surface area of the catalyst is 200-300 m 2 / g, and the pore size is 6.5-7.5 nm.

[0021] The preparation method of the second hydrodesulfurization catalyst comprises the following contents:

[0022] (a) mixing zinc oxide and aluminum oxide, adding water and a shaping aid, kneading, extruding into strips, drying, and calcining to obtain a strip-shaped carrier;

[0023] (b) mixing graphene oxide and the strip-shaped carrier, performing first microwave treatment, adding an alkaline solution to perform second microwave treatment, filtering, and drying to obtain a ZnO-Al2O3 carrier with graphene oxide on the surface;

[0024] (c) spraying a Cu and / or Ni-containing impregnation solution on the ZnO-Al2O3 carrier with graphene oxide on the surface to prepare a liquefied petroleum gas desulfurization catalyst.

[0025] The shaping aid in step (a) comprises one or more of a peptizing agent and an extrusion aid. The peptizing agent is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, oxalic acid, etc., the extrusion aid refers to a substance that is conducive to extrusion molding, such as one or more of sesbania powder, carbon black, graphite powder, citric acid, etc., and the amount of the shaping aid is 1.0wt%-10.0wt% of the carrier.

[0026] The drying method and conditions are well known to those skilled in the art, for example, the drying method can be air drying, oven drying, or air flow drying. Preferably, the drying temperature can be room temperature to 400°C, preferably 100 to 350°C; the drying time is more than 0.5h, preferably 0.5 to 100h, more preferably 2 to 20h. The calcination conditions are as follows: the calcination temperature is 400 to 700°C, preferably 450 to 650°C, and the calcination time is 0.5 to 100h, more preferably 0.5 to 10h.

[0027] The first microwave treatment in step (b) is carried out under the following conditions: microwave power is 500 to 900W, and the treatment time is 0.5 to 3.0h. The second microwave treatment is carried out under the following conditions: microwave power is 500 to 800W, and the treatment time is 1.0 to 4.0h.

[0028] The alkaline solution in step (b) can be an aqueous solution of potassium hydroxide and / or sodium hydroxide, and the mass concentration of the alkaline solution is 5.0% to 40.0%. The volume ratio of the alkaline solution to the total volume of the graphene oxide and the strip-shaped carrier is 1.5:1 to 2.5:1.

[0029] The impregnation solution containing Cu and / or Ni is an aqueous solution prepared by dissolving a soluble copper salt and / or a soluble nickel salt. The soluble copper salt and / or the soluble nickel salt can be one or more of a chloride salt, a sulfate salt, an acetate salt, and a nitrate salt.

[0030] The second hydrodesulfurization catalyst needs to be reduced before use. The reduction conditions are to convert the active metal oxides into elemental metals under a hydrogen-containing atmosphere, while the metal oxides in the carrier are not converted. The reduction conditions are as follows: pressure is 0.5 to 2.0MPa, temperature is 100 to 550°C, liquid petroleum gas feed volume space velocity is 0.1 to 20.0h -1 and hydrogen agent volume ratio is 10:1 to 100:1; the preferred reduction conditions are as follows: pressure is 1.0 to 2.0MPa, temperature is 200 to 450°C, feed volume space velocity is 0.1 to 10.0h -1 and hydrogen agent volume ratio is 50:1 to 100:1.

[0031] In the method of the present application, the hydrodesulfurization reaction process in step (2) can be carried out in a fixed bed reactor, a fluidized bed reactor, or a boiling bed reactor, preferably a fixed bed reactor.

[0032] In the method of the present application, the alcohol amine absorption in step (3) uses a mature process commonly used in industry. The alcohol amine solution includes at least one of monoethanolamine, diethanolamine, and diisopropanolamine.

[0033] Compared with the prior art, the method of the present application has the following characteristics:

[0034] The present application matches the reaction fraction groups with the reaction process, and precisely controls the reaction; first, the liquefied petroleum gas is separated into C3 and C4 fractions, and then hydrogen desulfurization is carried out respectively; a large amount of carbonyl sulfur compounds and propylene are contained in the C3 fraction, according to the hydrogen desulfurization reaction characteristics of the carbonyl sulfur compounds and propylene, by controlling certain reaction temperature and pressure, and cooperating with the first hydrogen desulfurization catalyst, the content of the carbonyl sulfur is reduced, and the olefin saturation rate is controlled to be low; the C4 fraction mainly contains butene and mercaptan compounds. According to the hydrogen desulfurization reaction characteristics of the butene and mercaptan, by controlling the second hydrogen desulfurization reaction conditions, and cooperating with the second hydrogen desulfurization catalyst, the content of the mercaptan sulfur is reduced, and the olefin saturation rate is controlled to be low. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A flow diagram of the liquefied petroleum gas hydrogen desulfurization of the present application

[0036] Figure 2 A TEM diagram of the zinc oxide-alumina support coated with graphene oxide of Example 2.

[0037] Figure 3 An active metal distribution diagram of the catalyst of Example 2. DETAILED DESCRIPTION

[0038] The method and effects of the present application are further illustrated below in combination with the drawings and examples, but do not limit the protection scope of the present application.

[0039] The liquefied petroleum gas hydrogen desulfurization of the present application is carried out in the following manner: the liquefied petroleum gas raw material 1 enters the gas fraction column to separate out the C3 fraction 3 and the C4 fraction 4. The C3 fraction 3 is mixed with hydrogen 5 and enters the hydrogen desulfurization reactor 6 to carry out hydrogen desulfurization reaction under appropriate reaction conditions. The C4 fraction 4 is mixed with hydrogen 5 and enters the hydrogen desulfurization reactor 8 to carry out hydrogen desulfurization reaction under appropriate reaction conditions. The hydrogen desulfurization reaction product 7 of the C3 fraction 3 and the hydrogen desulfurization product 9 of the C4 fraction 4 are mixed, and together with the lean amine liquid 11 enter the alcohol amine absorption tower 10 to remove hydrogen sulfide in the liquefied petroleum gas. The refined liquefied petroleum gas product 12 is obtained from the upper end of the absorption tower 10, and the rich amine liquid 13 obtained from the lower end of the absorption tower 10 is regenerated.

[0040] In the present application, the specific surface area and pore volume of the catalyst are measured by low-temperature liquid nitrogen adsorption BET method.

[0041] Example 1

[0042] In this example, a C3 fraction hydrogen desulfurization catalyst is prepared.

[0043] Take 100.0 g of pseudo-boehmite powder (Al2O3 dry basis content of 70 wt%), add 5 wt% of the Al2O3 dry basis of the sesbania powder auxiliary 3.5 g, 80 g of 5 wt% nitric acid aqueous solution, mix and roll the mixture into a plastic powder, and use an extruder to prepare a cylindrical strip with a diameter of 1.5 mm. Dry at 120°C for 6 hours, and calcine at 500°C for 4 hours to prepare a γ-Al2O3 carrier.

[0044] Take 9.27 g of nickel nitrate, 0.88 g of ammonium molybdate, and add 13.27 g of deionized water to make a solution, then immerse the solution in 20 g of the above γ-Al2O3 carrier at 30°C for 8 hours. Dry at 120°C for 6 hours, and calcine at 500°C for 4 hours to prepare a catalyst, numbered C3-1. The physical properties of the C3-1 catalyst are listed in Table 1.

[0045] Example 2

[0046] This example prepares a C4 fraction hydrodesulfurization catalyst.

[0047] Take 50.0 g of zinc oxide powder, 71.4 g of aluminum oxide powder (dry basis content of 70%), 6.0 g of sesbania powder, and an appropriate amount of deionized water, knead, extrude, dry, and calcine to obtain a strip-shaped carrier.

[0048] Take 0.8 g of graphene oxide (GO) and 60 g of ZnO-Al2O3 carrier and add them to a beaker, place it in a microwave oven, and microwave at 700 W for 1.0 h. Then add 94 mL of 10 wt% potassium hydroxide solution and continue to microwave at 600 W for 2.0 h. Remove and filter, and dry at 120°C for 8.0 h to obtain a graphene oxide-coated graphene-ZnO-Al2O3 carrier. Figure 2 TEM image of the graphene oxide-coated alumina-based carrier. Figure 2 The reticular flocculus in the image is the graphene component.

[0049] Take 37.6 g of nickel nitrate and prepare 100 mL of an impregnation solution. Take 85 mL of the impregnation solution and spray it onto the catalyst carrier. After drying at room temperature, dry at 120°C for 6 hours and calcine at 470°C for 4 hours to prepare a catalyst, numbered C4-1 catalyst. The physical properties of the C4-1 catalyst are listed in Table 1.

[0050] Example 3

[0051] This example prepares a C3 fraction hydrodesulfurization catalyst.

[0052] This example prepares a γ-Al2O3 carrier according to the method of Example 1.

[0053] A solution was prepared by weighing 9.27 g of nickel nitrate, 0.78 g of ammonium tungstate and 13.27 g of deionized water, and then impregnating the 20 g of the above γ-Al2O3 carrier in an equal volume at 30°C for 8 h, drying at 120°C for 6 h, and calcining at 500°C for 4 h to obtain a catalyst, which was numbered C3-2. The physical properties of the C3-2 catalyst are listed in Table 1.

[0054] Example 4

[0055] In this example, a C4 fraction hydrodesulfurization catalyst was prepared.

[0056] A strip-shaped carrier was obtained by kneading, extruding, drying and calcining 60.0 g of zinc oxide powder, 57.0 g of aluminum oxide powder (70% content on a dry basis), 6.0 g of sesbania powder and an appropriate amount of deionized water.

[0057] A beaker was charged with 0.5 g of graphene oxide (GO) and 60 g of ZnO-Al2O3 carrier, and then placed in a microwave device for microwave treatment at 700 W for 1.0 h. Then, 94 mL of a 10 wt% potassium hydroxide solution was added, and microwave treatment was continued at 600 W for 2.0 h. The product was removed, filtered and dried at 120°C for 8.0 h to obtain a graphene-ZnO-Al2O3 carrier coated with graphene oxide on the surface.

[0058] An impregnation solution was prepared by weighing 18.9 g of copper nitrate in 100 mL of deionized water. Then, 85 mL of the impregnation solution was sprayed onto the catalyst carrier. After air-drying at room temperature, the product was dried at 120°C for 6 h and calcined at 470°C for 4 h to obtain a catalyst, which was numbered C4-2 catalyst. The physical properties of the C4-2 catalyst are listed in Table 1. Figure 3 The active metal distribution map of the catalyst of Example 2 is shown in Figure 1. Figure 3 It can be seen that the active metal of the catalyst of this example is mainly distributed on the outer surface of the catalyst.

[0059] Example 5

[0060] In this example, liquefied petroleum gas was treated according to the method of the present application.

[0061] First, the C3-1 catalyst of Example 1 was subjected to conventional ex-situ presulfurization treatment, i.e., a selected sulfiding agent was loaded onto the oxidized catalyst by impregnation, and then subjected to low-temperature drying treatment.

[0062] 10 mL of the presulfurized C3-1 catalyst was loaded into the hydrodesulfurization reactor 6 of the C3 fraction hydrodesulfurization unit. Figure 1 10 mL of the C4-1 catalyst of Example 2 was loaded into the hydrodesulfurization reactor 8 of the C4 fraction hydrodesulfurization unit. Figure 1 First, the liquefied petroleum gas raw material was separated into C3 and C4 fractions in the gas fraction column. The properties of the liquefied petroleum gas raw material and the C3 and C4 fraction raw materials are listed in Table 2.

[0063] The C3 fraction was mixed with hydrogen and introduced into the hydrodesulfurization reactor 6, and reacted under the conditions of a hydrogen pressure of 1.0 MPa, a temperature of 320°C, and a hydrogen to hydrocarbon volume ratio of 100:1 for 2 h, so that the C3-1 catalyst was completely changed into a sulfided state. Then, the reaction pressure was maintained at 1.0 MPa, the hydrogen to hydrocarbon volume ratio was maintained at 10:1, the temperature was lowered to 160°C, and the volume space velocity was maintained at 10.0 h -1 The hydrodesulfurization reaction was carried out under the conditions of a hydrogen pressure of 1.0 MPa, a temperature of 320°C, and a hydrogen to hydrocarbon volume ratio of 100:1 for 2 h. The properties of the hydrodesulfurized product of the C3 fraction are shown in Table 2.

[0064] The C4 fraction was mixed with hydrogen and introduced into the hydrodesulfurization reactor 8, and reacted under the conditions of a hydrogen pressure of 1.6 MPa, a temperature of 400°C, and a hydrogen to hydrocarbon volume ratio of 100:1 for 2 h, so that the NiO in the C4-1 catalyst was reduced to Ni. Then, the reaction pressure was maintained at 1.6 MPa, the hydrogen to hydrocarbon volume ratio was maintained at 10:1, the temperature was lowered to 80°C, and the volume space velocity was maintained at 10.0 h -1 The hydrodesulfurization reaction was carried out under the conditions of a hydrogen pressure of 1.6 MPa, a temperature of 400°C, and a hydrogen to hydrocarbon volume ratio of 100:1 for 2 h. The properties of the hydrodesulfurized product of the C4 fraction are shown in Table 2.

[0065] The hydrodesulfurized product of the C3 fraction and the hydrodesulfurized product of the C4 fraction were mixed, hydrogen was separated by a separator, and the mixture was introduced into an alcohol amine absorption tower together with lean amine liquid to remove hydrogen sulfide in the liquefied petroleum gas. The rich amine liquid obtained from the lower end of the absorption tower was regenerated, and the refined liquefied petroleum gas product was obtained from the upper end of the absorption tower. The properties of the product are shown in Table 2.

[0066] Example 6

[0067] In this example, a liquefied petroleum gas was treated according to the method of the present application.

[0068] First, the C3-2 catalyst of Example 3 was subjected to a conventional ex-situ presulfurization treatment, i.e., a selected sulfiding agent was loaded onto the oxidized catalyst by an impregnation method, and then a low-temperature drying treatment was performed.

[0069] 10 mL of the presulfurized C3-2 catalyst of Example 3 was loaded into the hydrodesulfurization reactor 6 of the C3 fraction, and 10 mL of the C4-2 catalyst of Example 4 was loaded into the hydrodesulfurization reactor 8 of the C4 fraction. Figure 1 Figure 1 First, the liquefied petroleum gas raw material was introduced into a gas fraction column to separate a C3 fraction and a C4 fraction. The properties of the liquefied petroleum gas raw material and the C3 fraction and C4 fraction raw materials are shown in Table 2.

[0070] The C3 fraction was mixed with hydrogen and introduced into the hydrodesulfurization reactor 6, and reacted under the conditions of a hydrogen pressure of 1.0 MPa, a temperature of 320°C, and a hydrogen to hydrocarbon volume ratio of 100:1 for 2 h, so that the C3-1 catalyst was completely changed into a sulfided state. Then, the reaction pressure was maintained at 1.0 MPa, the hydrogen to hydrocarbon volume ratio was maintained at 5:1, the temperature was lowered to 180°C, and the volume space velocity was maintained at 5.0 h​-1 The C3 fraction was subjected to hydrodesulfurization reaction. The properties of the hydrodesulfurization product of the C3 fraction are listed in Table 2.

[0071] The C4 fraction was mixed with hydrogen and subjected to hydrodesulfurization reaction in the hydrodesulfurization reactor 8 under the conditions of hydrogen pressure 1.0 MPa, temperature 220°C, hydrogen / hydrocarbon volume ratio 80:1 for 2 h, so as to reduce CuO in the C4-2 catalyst to Cu; then the reaction pressure was maintained at 1.0 MPa, the hydrogen / hydrocarbon volume ratio was maintained at 5:1, the temperature was lowered to 50°C, and the volume space velocity was maintained at 8.0 h -1 The C4 fraction was subjected to hydrodesulfurization reaction. The properties of the hydrodesulfurization product of the C4 fraction are listed in Table 2.

[0072] The hydrodesulfurization product of the C3 fraction and the hydrodesulfurization product of the C4 fraction were mixed, hydrogen was separated out by a separator, and then the mixture was introduced into an alcohol amine absorption tower together with lean amine liquid to remove hydrogen sulfide in the liquefied petroleum gas. The rich amine liquid obtained from the lower end of the absorption tower was regenerated, and the refined liquefied petroleum gas product was obtained from the upper end of the absorption tower, and the properties of the product are listed in Table 2.

[0073] Comparative Example 1

[0074] This comparative example investigated the hydrodesulfurization effect of the full fraction of liquefied petroleum gas using the catalyst of Example 1.

[0075] The catalyst of Example 1 was first subjected to conventional ex-situ presulfurization treatment, i.e. a selected sulfiding agent was loaded onto the catalyst in oxidized state by impregnation, and then low-temperature drying treatment was performed.

[0076] 10 mL of the presulfurized C3-1 catalyst was loaded into a hydrodesulfurization reaction device. First, hydrogen was introduced to increase the pressure, and the C3-1 catalyst was completely changed into sulfided state under the conditions of hydrogen pressure 1.0 MPa, temperature 320°C, hydrogen / hydrocarbon volume ratio 100:1 for 2 h; then the reaction pressure was maintained at 1.0 MPa,

[0077] hydrogen / hydrocarbon volume ratio 10:1, and the temperature was lowered to 160°C, and the volume space velocity was maintained at 10.0 h -1 The full fraction of liquefied petroleum gas was subjected to hydrodesulfurization reaction. The reaction product was separated from hydrogen by a separator, and then introduced into an alcohol amine absorption tower together with lean amine liquid to remove hydrogen sulfide in the liquefied petroleum gas. The rich amine liquid obtained from the lower end of the absorption tower was regenerated, and the refined liquefied petroleum gas product was obtained from the upper end of the absorption tower, and the properties of the product are listed in Table 3.

[0078] Comparative Example 2

[0079] This comparative example investigated the hydrodesulfurization effect of the full fraction of liquefied petroleum gas using the catalyst of Example 2.

[0080] A 10 mL of C4-1 catalyst of Example 2 was charged into a hydrodesulfurization reactor. First, hydrogen was introduced to increase the pressure, and the C4-1 catalyst was reduced at a hydrogen pressure of 1.6 MPa, a temperature of 400°C, and a hydrogen to hydrocarbon volume ratio of 100:1 for 2 h to reduce the NiO in the C4-1 catalyst to Ni; then the reaction pressure was maintained at 1.6 MPa, the hydrogen to hydrocarbon volume ratio was maintained at 10:1, the temperature was reduced to 80°C, and the volume space velocity was 10.0 h -1 The full-range LPG feedstock was subjected to a hydrodesulfurization reaction, and the reaction product was separated from hydrogen in a separator and then introduced into an alcohol amine absorption tower together with lean amine liquid to remove hydrogen sulfide in the LPG. The rich amine liquid obtained from the lower end of the absorption tower was regenerated, and the refined LPG product was obtained from the upper end of the absorption tower. The properties of the product are listed in Table 3.

[0081] Comparative Example 3

[0082] This comparative example investigated the hydrodesulfurization effect of the LPG after fractionation under conventional reaction conditions.

[0083] This comparative example fractionated the LPG into C3 and C4 fractions according to the catalyst loading method and process flow of Example 5. The properties of the LPG feedstock and the C3 and C4 fraction feedstocks are shown in Table 2.

[0084] The reaction conditions of the C3 fraction were consistent with those of Example 5, except that the reaction temperature was adjusted to 120°C. The properties of the hydrodesulfurization product of the C3 fraction are listed in Table 3.

[0085] The reaction conditions of the C4 fraction were consistent with those of Example 5. The properties of the hydrodesulfurization product are listed in Table 3.

[0086] The hydrodesulfurization reaction products of the C3 fraction and the hydrodesulfurization products of the C4 fraction were mixed, separated from hydrogen in a separator, and then introduced into an alcohol amine absorption tower together with lean amine liquid to remove hydrogen sulfide in the LPG. The rich amine liquid obtained from the lower end of the absorption tower was regenerated, and the refined LPG product was obtained from the upper end of the absorption tower. The properties of the product are listed in Table 3.

[0087] Comparative Example 4

[0088] This comparative example investigated the hydrodesulfurization effect of the LPG after fractionation under conventional reaction conditions.

[0089] This comparative example fractionated the LPG into C3 and C4 fractions according to the catalyst loading method and process flow of Example 6. The properties of the LPG feedstock and the C3 and C4 fraction feedstocks are shown in Table 2.

[0090] The reaction conditions of the C3 fraction were consistent with those of Example 6, except that the reaction pressure was adjusted to 2.0 MPa. The properties of the hydrodesulfurization product of the C3 fraction are listed in Table 3.

[0091] The reaction conditions for the C4 fraction were the same as in Example 6, and the product properties of the hydrodesulfurized product are shown in Table 3.

[0092] The hydrodesulfurized product of the C3 fraction and the hydrodesulfurized product of the C4 fraction were mixed, and after separation of hydrogen gas in a separator, were introduced into an alcohol amine absorption tower along with lean amine liquid to remove hydrogen sulfide in the liquefied petroleum gas. The rich amine liquid obtained from the lower end of the absorption tower was regenerated, and the refined liquefied petroleum gas product was obtained from the upper end of the absorption tower, and the product properties are shown in Table 3.

[0093] Table 1 Catalyst properties

[0094] Item Example 1 Example 2 Example 3 Example 4 Catalyst No. C3-1 C4-1 C3-2 C4-2 Specific surface area, m 2 ·g -1 ]]> 200.1 240.2 194.7 235.3 Pore size, nm 7.1 6.8 8.3 7.0 ZnO, wt% - 50 - 60 Graphene oxide, wt% - 1.32 - 0.83 NiO, wt% 10.0 5 10.0 - CuO, wt% - - - 5 MoO3, wt.% 3.0 - - - [WC, wt%] - - 3.0 -

[0095] Table 2 Liquefied petroleum gas feedstock and hydrodesulfurized product properties

[0096]

[0097] Table 3 Liquefied petroleum gas feedstock and hydrodesulfurized product properties

[0098]

[0099] As can be seen from Tables 2 and 3, by treating a liquefied petroleum gas using the method of the present application, by controlling certain reaction temperature and pressure, and by using a first hydrodesulfurization catalyst, a refined liquefied petroleum gas product having a total sulfur content of <2.0 mg / m 3 and an olefin saturation rate of <2.0% can be produced.

Claims

1. A method for hydrodesulfurization of liquefied petroleum gas, characterized by The method comprises the following steps: (1) performing gas fractionation on a liquefied petroleum gas raw material to obtain a C3 fraction and a C4 fraction; (2) contacting the C3 fraction and the C4 fraction in liquid form with a hydrodesulfurization catalyst respectively to perform a hydrodesulfurization reaction, and hydrogenating sulfides in each fraction into hydrogen sulfide; wherein the C3 fraction is subjected to a high-temperature hydrodesulfurization reaction and the C4 fraction is subjected to a low-temperature hydrodesulfurization reaction; (3) the effluent of the hydrodesulfurization reactions of the C3 fraction and the C4 fraction is subjected to alcohol amine absorption to remove hydrogen sulfide, thereby obtaining a refined liquefied petroleum gas product; the reaction pressure of the high-temperature hydrodesulfurization reaction in step (2) is 0.5-1.6 MPa, and the reaction temperature is 150-250℃; the reaction temperature of the low-temperature hydrodesulfurization reaction in step (2) is 20-100℃; the second hydrodesulfurization catalyst used in the low-temperature hydrodesulfurization reaction in step (2) comprises a composite oxide carrier and an active metal component; the composite oxide carrier is graphene oxide-ZnO-Al2O3, wherein the graphene oxide is distributed on the surface of the zinc oxide and the aluminum oxide, the content of the zinc oxide is 20.0wt%-90.0wt%, the content of the graphene oxide is 0.1wt%-10.0wt%, and the balance is aluminum oxide; the active metal component is CuO and / or NiO; the content of CuO and / or NiO is 5.0wt%-20.0wt% based on the weight of the catalyst, and the balance is the composite oxide carrier; the specific surface area of the catalyst is 200-300m 2 / g, and the pore size is 6.5-7.5nm; the second hydrodesulfurization catalyst needs to be reduced before use, and the reduction conditions are to convert the active metal oxides into elemental metals under a hydrogen-containing atmosphere, while the metal oxides in the carrier are not converted.

2. The method of claim 1, wherein: The liquefied petroleum gas raw material in step (1) is one or more of catalytically cracked liquefied petroleum gas, coked liquefied petroleum gas and natural liquefied petroleum gas.

3. The method of claim 1, wherein: The liquefied petroleum gas raw material in step (1) has a propylene content of 20.0 v% to 40.0 v%, a butene content of 10.0 v% to 30.0 v%, and a total sulfur content of 100 to 5000 mg / m 3 .

4. The method of claim 1, wherein: The liquefied petroleum gas raw material in step (1) has a hydrogen sulfide content of 50 to 5,000 mg / m 3 , a carbonyl sulfide content of 10 to 50 mg / m 3 , a methyl mercaptan sulfur content of 50 to 500 mg / m 3 , and an ethyl mercaptan sulfur content of 50 to 500 mg / m 3 .

5. The method of claim 1, wherein: The content of propylene in the C3 fraction in step (2) is 50.0 v% to 80.0 v%, the content of hydrogen sulfide is 50 to 5000 mg / m 3 , and the content of carbonyl sulfur is 10 to 100 mg / m 3 .

6. The method of claim 1, wherein: Step (2) high temperature hydrodesulfurization reaction conditions are: feed volume space velocity 0.2-20.0 h -1 and hydrogen hydrocarbon volume ratio 0.1-20:

1.

7. The method of claim 1, wherein: Step (2) high temperature hydrodesulfurization reaction conditions are: reaction pressure 0.5-1.0 MPa, reaction temperature 150-200°C, feed volume space velocity 0.2-10.0 h -1 and hydrogen hydrocarbon volume ratio 0.1-10:

1.

8. The method of claim 1, wherein: The first hydrodesulfurization catalyst used in the high-temperature hydrodesulfurization reaction in step (2) is a Ni-Mo / γ-Al2O3 or Ni-W / γ-Al2O3 supported hydrodesulfurization catalyst, and the content of NiO is 5.0wt%-20.0wt% and the content of MoO3 or WO3 is 3.0wt%-14.0wt% based on the weight of the catalyst.

9. The method of claim 8, wherein: The first hydrodesulfurization catalyst in step (2) is pre-sulfurized before use to convert the metal oxide active precursor into a sulfide active phase with catalytic activity.

10. The method of claim 1, wherein: The content of butene in the C4 fraction in step (2) is 40.0 v% to 60.0 v%, the content of methyl mercaptan is 50 to 500 mg / m 3 , and the content of ethyl mercaptan is 50 to 500 mg / m 3 .

11. The method of claim 1, wherein: The reaction conditions of step (2) are as follows: reaction pressure 0.5-2.5 MPa, feed volume space velocity 0.1-20.0 h -1 , hydrogen / hydrocarbon volume ratio 0.1-20:

1.

12. The method of claim 1, wherein: Step (2) low-temperature hydrodesulfurization reaction conditions are: reaction pressure 1.0-2.5 MPa, reaction temperature 20-80℃, feed volume space velocity 0.1-10.0 h -1 , hydrogen hydrocarbon volume ratio 0.1-10:

1.

13. The method of claim 1, wherein: The reduction conditions of the second hydrodesulfurization catalyst are as follows: pressure 0.5-2.0 MPa, temperature 100-550℃ and hydrogen agent volume ratio 10:1-100:

1.

14. The method of claim 1, wherein: The hydrodesulfurization reaction process in step (2) is performed in a fixed bed reactor, a fluidized bed reactor or a boiling bed reactor.

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