A method for deep desulfurization of liquefied petroleum gas

Abstract

This invention discloses a method for deep desulfurization of liquefied petroleum gas (LPG), comprising the following: (1) LPG feedstock first enters an alcohol amine absorption tower to remove hydrogen sulfide; (2) LPG and hydrogen gas, after hydrogen sulfide removal, enter a hydrodesulfurization reactor from the top of the reactor and undergo hydrodesulfurization reaction under the action of LPG desulfurization catalyst; (3) After desulfurization, LPG enters a separator for gas-liquid separation, the separated hydrogen gas is recycled, and the liquid phase enters an alcohol amine absorption tower to absorb the sulfides produced by the reaction, and enters the upper end of the alcohol amine absorption tower to obtain refined LPG product; wherein, the LPG desulfurization catalyst comprises a carrier and an active metal component, the carrier being graphene oxide-ZnO-Al2O3, wherein graphene oxide is distributed on the surface of zinc oxide and aluminum oxide; the mass ratio of zinc oxide is 20.0%~90.0%, and the content of graphene oxide is 0.1wt%~10.0wt%; the active metal component is CuO and / or NiO. The method of this invention can achieve deep desulfurization of liquefied petroleum gas under low temperature and low olefin saturation conditions.

Description

Technical Field

[0001] This invention belongs to the field of petroleum refining, and specifically relates to a method for deep desulfurization of liquefied petroleum gas. Background Technology

[0002] According to statistics, in 2018, Sinopec's catalytic cracking liquefied petroleum gas (LPG) processing capacity reached 14.3 million tons / year. The average composition of LPG was propane (12.8 v%), butane (26.1 v%), propylene (38.0 v%), butene (21.0 v%), etc., with a concentration as high as 4264 mg / m³. 3 Sulfur-containing compounds, which mainly exist in the form of hydrogen sulfide and organic sulfides such as thiols.

[0003] Catalytic cracking liquefied petroleum gas (LPG) is a major source of propylene and isobutene. Propylene, used for downstream polymerization, and isobutene, used as feedstock for MTBE, require desulfurization (hydrogen sulfide and mercaptans), especially at 4264 mg / m³. 3 Sulfur-containing compounds must undergo dual desulfurization (H2S removal and mercaptan removal) to meet the requirement that the total sulfur content downstream is ≤10 mg / m³. 3 Requirements.

[0004] Traditional dual desulfurization processes for liquefied petroleum gas (LPG) are mostly based on the Merox deodorization (Sweeten) process, the main principles of which are as follows:

[0005] Alkali extraction Thiol removal: RSH + NaOH ⇄ NaSR + H2O

[0006] Hydrogen sulfide removal: H2S + 2NaOH → Na2S + 2H2O

[0007] Alkali regeneration Sodium thiolate oxidation: 4NaSR + O2 + 2H2O → 4NaOH + 2RSSR

[0008] Sodium sulfide oxidizes 2Na₂S + 2O₂ + H₂O → Na₂S₂O₃ + 2NaOH

[0009] Na2S2O3+ 2O2+ 2NaOH → 2Na2SO4+ H2O

[0010] It can be seen that one of the disadvantages of dual desulfurization (H2S removal and mercaptan removal) is that mercaptan (RSH) is only oxidized into disulfide (RSSR), without reducing the total sulfur content or reducing the total sulfur content to a limited extent; another disadvantage is that the regenerated organic waste gas and alkaline residue generated by the desulfurization unit are pollutants that are difficult to treat in the environment, posing potential environmental or safety hazards.

[0011] CN200910233505.1 introduces a highly efficient desulfurizing agent for highly acidic oil and natural gas. Its main feature is the addition of a water-soluble nitrogen-containing organic solvent (basic nitrogen content ≥100 g / L) to a fiber membrane reactor for desulfurization. Its advantages include a higher desulfurization rate than traditional alkanolamine methods (such as N-methyldiethanolamine, MDEA); however, the nitrogen-containing organic solvent requires repeated regeneration and heat exchange, resulting in a complex process and high energy consumption.

[0012] CN104194833A introduces a deep desulfurization process for liquefied petroleum gas (LPG). The process involves first removing H2S from the LPG through amine extraction and then washing with water to remove the carried amine. Next, hydrogenation is performed on a sulfidated Mo-Ni / γ-Al2O3 catalyst to convert the sulfides in the LPG into high-boiling-point sulfides. The hydrogenation product enters a stabilization tower and is then separated by distillation using a low-sulfur C5 or higher fraction to obtain ultra-low-sulfur LPG, which can be used as a feedstock for the production of MTBE or alkylation low-sulfur products.

[0013] CN103965984A describes a catalytic desulfurization method for liquefied petroleum gas (LPG). The method involves mixing LPG with hydrogen and then introducing the mixture into a fixed-bed reactor. There, a Ni-Mo / γ-Al₂O₃ or Ni-W / γ-Al₂O₃ catalyst is packed within the reactor to undergo a sulfideation reaction, converting low-boiling thiols into high-boiling sulfide compounds. The sulfideation product is then distilled in a distillation column to obtain a sulfide-free LPG product. However, this method has several drawbacks. First, the presence of 0.03% (v / v) to 0.04% (v / v) of 1,3-butadiene in the LPG can easily cause catalyst deactivation due to carbon buildup. Within approximately 100 hours, the thiol content exceeds 10 µg / g. Second, the distillation column requires a reboiler, resulting in high energy consumption.

[0014] US7270737B2 describes a desulfurization process for hydrocarbon feedstocks. Its key feature is the use of a catalyst containing Group VIII metals (trade name HR845 catalyst, sulfide state) for selective hydrodesulfurization. This process reacts low-boiling mercaptans in the gasoline with dienes to convert them into high-boiling sulfides. The resulting residue oil, with low sulfur content, is then extracted using an extraction tower. Compared to the feedstock, the desulfurization rate can reach 97.9%, while also reducing the diene content and olefin saturation. However, its disadvantages include the use of sulfolane as a solvent, which requires repeated regeneration and complicates the process. Furthermore, it poses a fire and explosion hazard; sulfolane is flammable, corrosive, can cause burns, and has a water hazard level of 1 (German regulations), easily polluting the surrounding environment.

[0015] Hydrodesulfurization technology has achieved good results in the desulfurization of catalytic cracking gasoline, but its industrial application in the desulfurization of liquefied petroleum gas (LPG) is relatively limited. Therefore, in order to make up for the shortcomings of the current LPG desulfurization process and improve the LPG refining process, the development of LPG hydrodesulfurization catalysts is of certain significance and prospect. Summary of the Invention

[0016] To address the shortcomings of existing technologies, this invention provides a method for deep desulfurization of liquefied petroleum gas (LPG). This method can achieve deep desulfurization of LPG under low temperature and low olefin saturation conditions.

[0017] The method for deep desulfurization of liquefied petroleum gas of the present invention includes the following: (1) the liquefied petroleum gas feedstock first enters the amine absorber to remove hydrogen sulfide; (2) the liquefied petroleum gas and hydrogen gas after hydrogen sulfide removal enter the hydrodesulfurization reactor from the top of the reactor and undergo hydrodesulfurization reaction under the action of the liquefied petroleum gas desulfurization catalyst; (3) the desulfurized liquefied petroleum gas enters the separator for gas-liquid separation, the separated hydrogen gas is recycled, the liquid phase enters the amine absorber to absorb the sulfides produced by the reaction, and enters the upper end of the amine absorber to obtain refined liquefied petroleum gas product; wherein, the liquefied petroleum gas desulfurization catalyst includes a carrier and an active metal component, the carrier being an oxide The catalyst is a graphene-ZnO-Al2O3 catalyst, wherein graphene oxide is distributed on the surface of zinc oxide and aluminum oxide; the zinc oxide accounts for 20.0%~90.0% by mass, preferably 50.0%~70.0%, and the graphene oxide content is 0.1wt%~10.0wt%, preferably 0.5wt%~8.0wt%; the active metal component is CuO and / or NiO, and based on the weight of the catalyst, the CuO and / or NiO content is 5.0wt%~20.0wt%, preferably 5.0wt%~10.0wt%; the specific surface area of ​​the catalyst is 200~300m². 2 / g, pore size 6.5~7.5nm.

[0018] In the method of this invention, the liquefied petroleum gas (LPG) feedstock in step (1) is catalytic cracking LPG, coking LPG, natural LPG, etc., preferably catalytic cracking LPG; the propylene content in the LPG feedstock is 20.0 v%~40.0 v%, the butene content is 10.0 v%~30 v%, and the total sulfur content is 100~5000 mg / m³. 3 The sulfur content of thiols is 50~200 mg / m³. 3 .

[0019] In the method of the present invention, the amine solution used in the amine absorption tower in steps (1) and (3) is at least one of monoethanolamine, diethanolamine, and diisopropanolamine.

[0020] In the method of the present invention, the hydrodesulfurization reactor in step (2) can be a fixed bed reactor, a fluidized bed reactor or a boiling bed reactor, preferably a fixed bed reactor; the liquefied gas in step (2) is in contact with the liquefied gas desulfurization catalyst in liquid form.

[0021] In the method of this invention, the hydrodesulfurization reaction conditions in step (2) are as follows: reaction pressure 0.1–2.0 MPa, reaction temperature 20–150 °C, and liquefied gas feed volume hourly space velocity 0.1–20.0 h⁻¹. -1 The volume ratio of hydrogen agent (hydrogen and catalyst) is 1:1 to 100:1; the preferred operating conditions are as follows: reaction pressure 0.1 to 1.0 MPa, reaction temperature 20 to 100 °C, and feed volume hourly space velocity 0.1 to 10.0 h⁻¹. -1 The volume ratio of hydrogen agent (hydrogen and catalyst) is 5:1 to 50:1.

[0022] In the method of the present invention, the separator in step (3) can be any device in the art capable of separating liquids and gases.

[0023] The method for preparing the liquefied petroleum gas desulfurization catalyst in this invention includes the following steps:

[0024] (a) Zinc oxide and aluminum oxide are mixed, water and molding aids are added, kneaded, extruded, dried and calcined to obtain a strip carrier;

[0025] (b) Mix graphene oxide and strip support, perform a first microwave treatment, add an alkaline solution for a second microwave treatment, filter and dry to obtain a ZnO-Al2O3 support with graphene oxide on the surface.

[0026] (c) A Cu and / or Ni impregnation solution was sprayed onto a ZnO-Al2O3 support coated with graphene oxide to prepare a liquefied gas desulfurization catalyst.

[0027] The molding aid mentioned in step (a) includes one or more of a binder and an extrusion aid. The binder is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, oxalic acid, etc., and the extrusion aid refers to a substance that is beneficial to extrusion molding, such as one or more of guar gum powder, carbon black, graphite powder, citric acid, etc. The amount of molding aid is 1.0 wt% to 10.0 wt% of the carrier.

[0028] The drying methods and conditions described are recognized by those skilled in the art. For example, the drying methods may include air drying, oven drying, or forced-air drying. Preferably, the drying temperature is room temperature to 400°C, more preferably 100 to 350°C; the drying time is 0.5 hours or more, preferably 0.5 to 100 hours, and more preferably 2 to 20 hours. The calcination conditions are: calcination temperature of 400 to 700°C, preferably 450 to 650°C, and calcination time of 0.5 to 100 hours, more preferably 0.5 to 10 hours.

[0029] The conditions for the first microwave treatment in step (b) are as follows: microwave power of 500~900W and processing time of 0.5~3.0h. The conditions for the second microwave treatment are as follows: microwave power of 500~800W and processing time of 1.0~4.0h.

[0030] The alkaline solution in step (b) can be an aqueous solution of potassium hydroxide and / or sodium hydroxide, with a mass concentration of 5.0% to 40.0%. The volume ratio of the alkaline solution to the total volume of graphene oxide and the strip support is 1.5:1 to 2.5:1.

[0031] The impregnation solution containing Cu and / or Ni is an aqueous solution prepared from soluble copper salts and / or nickel salts, which are one or more of chlorides, sulfates, acetates, and nitrates.

[0032] The liquefied petroleum gas (LPG) desulfurization catalyst requires reduction before use. The reduction conditions are as follows: under a hydrogen-containing atmosphere, the active metal oxide is converted into an elemental metal, while the metal oxide in the support remains unchanged. Preferably, the reduction conditions are: pressure 0.5 MPa–2.0 MPa, temperature 100°C–550°C, and LPG feed volume hourly space velocity (VHSV) of 0.1 h⁻¹. -1 ~20.0h -1 The volume ratio of hydrogen to hydrogen is 10:1 to 100:1; the preferred reduction conditions are as follows: pressure 0.5 to 1.0 MPa, temperature 200 to 450 °C, and feed volume hourly space velocity 0.1 to 10.0 h⁻¹. -1 The volume ratio of hydrogen to hydrogen is 20:1 to 50:1.

[0033] Compared with existing technologies, the method of this invention has the following characteristics: liquefied petroleum gas (LPG) contains a large amount of olefins, which readily undergo hydrogenation saturation reactions. This application achieves deep desulfurization of LPG under low temperature and low olefin saturation conditions through a clever matching of process conditions and catalyst. This invention employs a specific preparation method, using Cu and / or Ni as the active component, alumina and zinc oxide as the composite support, and a special graphene encapsulation method in step (b) to obtain a catalyst with low hydrogenation activity and strong low-temperature desulfurization capability. Simultaneously, the matched mild process conditions—low temperature, high space velocity, and less hydrogen—prevent olefins from undergoing hydrogenation saturation reactions. This also removes low-boiling-point sulfides such as methanethiol and ethanethiol from LPG, while high-boiling-point sulfides are separated and absorbed by alkanolamines, dissolved in an amine-rich solution, and separated from the LPG. Compared with traditional LPG desulfurization methods, the method of this invention has a simple process flow, mild reaction conditions, low investment, and is environmentally friendly. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the process of the present invention;

[0035] Figure 2 This is a distribution diagram of the active metals in the catalyst of Example 1;

[0036] Figure 3 This is a distribution diagram of the active metals in the catalyst of Comparative Example 1;

[0037] Figure 4 This is a comparison diagram of the pore size distribution of Example 1 and Comparative Example 1;

[0038] Figure 5 Comparison of NH3-TPD acid distribution between Example 1 and Comparative Example 1;

[0039] Figure 6 This is a TEM image of the graphene oxide-coated support prepared in Example 2. Detailed Implementation

[0040] The method and effects of the present invention will be further described below with reference to the accompanying drawings and embodiments, but this does not limit the scope of protection of the present invention.

[0041] Figure 1The lean amine solution 1 and liquefied petroleum gas (LPG) feedstock 2 enter the amine absorption tower 3 to remove hydrogen sulfide from the LPG. After hydrogen sulfide removal, the LPG 4 and hydrogen 6 enter the hydrodesulfurization reactor 7 from the top of the reactor, where a hydrodesulfurization reaction is carried out under the action of the LPG desulfurization catalyst. The desulfurized LPG 8 enters the separator 9 to separate hydrogen 10 for recycling. The separated liquid LPG 12 enters the amine absorption tower 13 to absorb the hydrogen sulfide and atmospheric pressure liquid-phase macromolecular sulfides produced in the reaction. The rich amine solution 14 is regenerated, and refined LPG product 15 is obtained at the top of the absorption tower 13.

[0042] In particular, the main substances produced in the hydrodesulfurization reactor, such as thiols, sulfides, disulfides, and carbonyl sulfides, undergo catalyst hydrodesulfurization, as follows:

[0043] RSH + H2 → RH3 + H2S (1)

[0044] R1SR2+H2→R1H3+ R2H3+H2S (2)

[0045] R1SSR2+H2→R1H3+ R2H3+H2S (3)

[0046] COS + H2 → CH4 + H2S (4)

[0047] In this invention, the BET specific surface area and pore volume were determined using the GB / T5816-1995 method; the total acid content was characterized using temperature-programmed desorption analysis (NH3-TPD); the sulfur content of the liquefied petroleum gas (LPG) feedstock and products was qualitatively and quantitatively analyzed using gas chromatography; and the hydrocarbon composition of the LPG feedstock and products was analyzed using gas chromatography-FID.

[0048] Example 1

[0049] Weigh 60.0g of zinc oxide powder, 57.0g of alumina powder (70% dry basis), 6.0g of guar gum powder and an appropriate amount of deionized water, mix and extrude, dry and calcine to obtain a strip carrier.

[0050] Weigh 0.5g of graphene oxide (GO) and 60g of ZnO-Al2O3 support and add them to a beaker. Microwave the beaker at 700W for 1.0h, then add 94mL of 10wt% potassium hydroxide solution and continue microwave treatment at 600W for 2.0h. Remove and filter, then dry at 120℃ for 8.0h to obtain graphene-ZnO-Al2O3 support with graphene oxide coating on the surface.

[0051] 18.9 g of copper nitrate was weighed and prepared into a 100 mL impregnation solution. 85 mL of the impregnation solution was sprayed onto the catalyst support. After drying at room temperature, it was dried at 120 °C for 6 hours and calcined at 470 °C for 4 hours to prepare the catalyst, designated as catalyst L-1. The physical properties of catalyst L-1 are listed in Table 1. Figure 2 This is a distribution map of the active metals in Example 1. From... Figure 2 It can be seen that the active metal of the catalyst in this embodiment is mainly distributed on the outer surface of the catalyst.

[0052] Comparative Example 1

[0053] This comparative example prepared a catalyst according to the method of Example 1, except that the support was not covered with graphene oxide. The catalyst is designated R-1, and its properties are listed in Table 1. Figure 3 This is a distribution map of active metals. From... Figure 3 It can be seen that the active metal in this comparative catalyst is distributed both inside and outside the catalyst. Figure 4 This is a comparison diagram of the pore size distribution between Comparative Example 1 and Example 1. From... Figure 4 It can be seen that the catalyst pore size is more concentrated. Figure 5 This is a comparison diagram of the NH3-TPD acid distribution between Comparative Example 1 and Example 1.

[0054] Example 2

[0055] Weigh 50.0g of zinc oxide powder, 71.4g of alumina powder (70% dry basis), 6.0g of guar gum powder and an appropriate amount of deionized water, mix and extrude, dry and calcine to obtain a strip carrier.

[0056] 0.8 g of graphene oxide (GO) and 60 g of ZnO-Al2O3 support were weighed and added to a beaker. The beaker was microwaved at 700 W for 1.0 h. Then, 94 mL of 10 wt% potassium hydroxide solution was added and microwaved at 600 W for another 2.0 h. The beaker was then filtered and dried at 120 °C for 8.0 h to obtain a graphene-ZnO-Al2O3 support with graphene oxide coating on its surface. Figure 5 This is a TEM image of an alumina-based support with graphene oxide coating on its surface. Figure 5 The network-like flocculent material in it is a graphene component.

[0057] 37.6 g of nickel nitrate was weighed and prepared into a 100 mL impregnation solution. 85 mL of this solution was sprayed onto the catalyst support. After drying at room temperature, the catalyst was dried at 120 °C for 6 hours and then calcined at 470 °C for 4 hours to obtain the catalyst, designated as catalyst L-2. The properties of this catalyst are listed in Table 1. Figure 6 This is a distribution map of active metals in Example 2. From... Figure 6 It can be seen that the active metal of the catalyst in this invention is mainly distributed on the outer surface of the catalyst.

[0058] Comparative Example 2

[0059] This comparative example prepared a catalyst according to the method of Example 2, except that the support was not covered with graphene oxide. The catalyst is designated R-2, and its properties are listed in Table 1.

[0060] Example 3

[0061] Weigh 70.0g of zinc oxide powder, 42.9g of alumina powder (70% dry basis), 6.0g of guar gum powder and an appropriate amount of deionized water, mix and extrude, dry and calcine to obtain a strip carrier.

[0062] 1.2 g of graphene oxide (GO) and 60 g of ZnO-Al2O3 support were weighed and added to a beaker. The beaker was microwaved at 700 W for 1.0 h, followed by the addition of 94 mL of 10 wt% potassium hydroxide solution and further microwaved at 600 W for 2.0 h. The beaker was then filtered and dried at 120 °C for 8.0 h to obtain a graphene-ZnO-Al2O3 support coated with graphene oxide. 11.3 g of copper nitrate and 22.6 g of nickel nitrate were weighed to prepare a 100 mL impregnation solution. 85 mL of this solution was sprayed onto the catalyst support. After drying at room temperature, the support was dried at 120 °C for 6 h and calcined at 470 °C for 4 h to obtain the catalyst, designated as catalyst L-3. The properties of catalyst L-3 are listed in Table 1.

[0063] Comparative Example 3

[0064] This comparative example is the same as Example 3, except that it lacks the second microwave treatment process after adding the alkali solution: "After adding 94 mL of 10 wt% potassium hydroxide solution, continue microwave treatment at 600 W for 2.0 h, then remove and filter." The catalyst is designated R-3, and its properties are listed in Table 1.

[0065] Example 4

[0066] This embodiment examines the performance of the catalyst from Example 1.

[0067] Load 10 mL of the new L-1 catalyst into Figure 1 Inside the hydrodesulfurization reactor, hydrogen was first introduced to increase the pressure. The new L-1 catalyst was reduced for 2 hours under the conditions of a hydrogen pressure of 1.0 MPa, a temperature of 220°C, and a hydrogen-to-catalyst volume ratio of 20:1, reducing CuO in the R-2 catalyst to Cu. Then, the reaction pressure was maintained at 1.0 MPa, the hydrogen-to-catalyst volume ratio at 20:1, the temperature was lowered to 70°C, and the volume hourly space velocity (VHSV) was 8.0 h⁻¹. -1The liquefied petroleum gas feedstock, after hydrogen sulfide removal, is fed into the gas to carry out a desulfurization reaction. The reaction products are separated into hydrogen by a separator and then enter an amine liquid absorption tower to absorb the hydrogen sulfide and atmospheric pressure liquid-phase macromolecular sulfides produced in the reaction (using diethanolamine as the absorption solvent, with a diethanolamine:reaction product volume ratio of 3:1). The final desulfurization product is obtained at the top of the absorption tower.

[0068] Table 2 lists the analysis results of liquefied petroleum gas feedstock and desulfurization products.

[0069] Comparative Example 4

[0070] The performance of the catalyst in Comparative Example 1 was examined according to the method in Example 4.

[0071] Example 5

[0072] This embodiment examines the performance of the catalyst from Example 2.

[0073] Load 10 mL of the new L-2 catalyst into Figure 1 Inside the hydrodesulfurization reactor, hydrogen was first introduced to increase the pressure. The new L-2 catalyst was reduced for 2 hours at a hydrogen pressure of 1.0 MPa, a temperature of 400°C, and a hydrogen-to-catalyst volume ratio of 50:1, reducing NiO in the R-2 catalyst to Ni. Then, the reaction pressure was maintained at 1.0 MPa, the hydrogen-to-catalyst volume ratio at 50:1, the temperature was lowered to 80°C, and the volume hourly space velocity (VHSV) was 10.0 h⁻¹. -1 The liquefied petroleum gas (LPG) feedstock, after hydrogen sulfide removal, undergoes a desulfurization reaction; the reaction products, after hydrogen is separated by a separator, enter... Amine liquid absorption tower The hydrogen sulfide and macromolecular sulfides produced by the absorption reaction are absorbed (using diethanolamine as the absorption solvent, with a diethanolamine:reaction product volume ratio of 3:1); the desulfurization product is finally obtained at the top of the absorption tower.

[0074] Table 2 lists the analysis results of liquefied petroleum gas feedstock and desulfurization products.

[0075] Comparative Example 5

[0076] The performance of the catalyst in Comparative Example 2 was examined according to the method in Example 5.

[0077] Example 6

[0078] This example examines the performance of the catalyst in Example 3.

[0079] Load 10 mL of the new L-3 catalyst into Figure 1Inside the hydrodesulfurization reactor, hydrogen was first introduced to increase the pressure. The new L-3 catalyst was reduced for 2 hours under the conditions of 1.0 MPa hydrogen pressure, 400°C temperature, and a hydrogen-to-catalyst volume ratio of 50:1, reducing CuO in the R-2 catalyst to Cu and NiO to Ni. Then, the reaction pressure was maintained at 1.0 MPa and the hydrogen-to-catalyst volume ratio at 50:1, the temperature was lowered to 90°C, and the volume hourly space velocity (VHSV) was 10.0 h⁻¹. -1 The liquefied petroleum gas feedstock, after hydrogen sulfide removal, is fed into the gas to carry out a desulfurization reaction. The reaction products are separated into hydrogen by a separator and then enter an amine liquid absorption tower to absorb the hydrogen sulfide and atmospheric pressure liquid-phase macromolecular sulfides produced in the reaction (using diethanolamine as the absorption solvent, with a diethanolamine:reaction product volume ratio of 3:1). The final desulfurization product is obtained at the top of the absorption tower.

[0080] Table 2 lists the analysis results of liquefied petroleum gas feedstock and desulfurization products.

[0081] Comparative Example 6

[0082] The performance of the catalyst in Comparative Example 2 was examined according to the method in Example 6.

[0083] As can be seen from Table 2, the reasonable matching of process conditions and catalyst in this invention enables deep desulfurization of liquefied petroleum gas under low temperature and low olefin saturation conditions.

[0084] Table 1 Catalyst Properties

[0085]

[0086] Table 2 Properties of Liquefied Petroleum Gas Feedstock and Desulfurization Products

[0087]

Claims

1. A method for deep desulfurization of liquefied petroleum gas, characterized in that... The process includes the following: (1) liquefied petroleum gas (LPG) feedstock first enters an alcohol amine absorption tower to remove hydrogen sulfide; (2) the LPG and hydrogen gas after hydrogen sulfide removal enter the hydrodesulfurization reactor from the top of the reactor, where hydrodesulfurization reaction is carried out under the action of the LPG desulfurization catalyst; (3) after desulfurization, the LPG enters a separator for gas-liquid separation, the separated hydrogen gas is recycled, and the liquid phase enters the alcohol amine absorption tower to absorb the sulfides produced by the reaction, and enters the upper end of the alcohol amine absorption tower to obtain refined LPG product; wherein, the LPG desulfurization catalyst includes a support and an active metal component, and the support is graphene oxide-ZnO. -Al2O3, wherein graphene oxide is distributed on the surface of zinc oxide and aluminum oxide; zinc oxide accounts for 20.0%~90.0% by mass, and the content of graphene oxide is 0.1wt%~10.0wt%; the active metal component is CuO and / or NiO, and the content of CuO and / or NiO is 5.0wt%~20.0wt% based on the weight of the catalyst; the hydrodesulfurization reaction conditions in step (2) are as follows: reaction pressure is 0.1~2.0MPa, reaction temperature is 20~100℃, and liquefied gas feed volume hourly space velocity is 0.1~20.0h. -1 The volume ratio of hydrogen to catalyst is 1:1 to 100:

1.

2. The method according to claim 1, characterized in that: The specific surface area of ​​the LPG desulfurization catalyst is 200~300 m². 2 / g, pore size 6.5~7.5nm.

3. The method according to claim 1, characterized in that: The liquefied petroleum gas (LPG) feedstock in step (1) is one or more of catalytic cracking LPG, coking LPG, and natural LPG; the propylene content in the LPG feedstock is 20.0 v%~40.0 v%, the butene content is 10.0 v%~30 v%, and the total sulfur content is 100~5000 mg / m³. 3 The sulfur content in thiols is 50~200 mg / m³. 3 .

4. The method according to claim 1, characterized in that: The amine solution used in the amine absorption tower in steps (1) and (3) is at least one of monoethanolamine, diethanolamine, and diisopropanolamine.

5. The method according to claim 1, characterized in that: The hydrodesulfurization reactor in step (2) is a fixed-bed reactor, a fluidized-bed reactor, or a boiling-bed reactor; the liquefied gas in step (2) is in contact with the liquefied gas desulfurization catalyst in liquid form.

6. The method according to claim 1, characterized in that: The hydrodesulfurization reaction conditions in step (2) are as follows: reaction pressure 0.1–1.0 MPa, reaction temperature 20–100 °C, and feed volume hourly space velocity 0.1–10.0 h⁻¹. -1 The volume ratio of hydrogen to catalyst is 5:1 to 50:

1.

7. The method according to claim 1, characterized in that: The preparation method of the liquefied gas desulfurization catalyst includes the following steps: (a) mixing zinc oxide and aluminum oxide, adding water and molding aids, kneading, extruding, drying, and calcining to obtain a strip-shaped support; (b) mixing graphene oxide and the strip-shaped support, subjecting it to a first microwave treatment, adding an alkaline solution for a second microwave treatment, filtering, and drying to obtain a ZnO-Al2O3 support with graphene oxide coating; (c) spraying an impregnation solution containing Cu and / or Ni onto the ZnO-Al2O3 support with graphene oxide coating to prepare the liquefied gas desulfurization catalyst.

8. The method according to claim 7, characterized in that: The molding aid mentioned in step (a) is one or more of a glue solvent and an extrusion aid; the glue solvent is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, and oxalic acid; the extrusion aid is one or more of guar gum powder, carbon black, graphite powder, and citric acid; the amount of molding aid is 1.0wt% to 10.0wt% of the carrier.

9. The method according to claim 7, characterized in that: The drying temperature is room temperature to 400℃, and the drying time is 0.5 to 100 hours; the calcination conditions are: calcination temperature to 400 to 700℃, and calcination time to 0.5 to 100 hours.

10. The method according to claim 7, characterized in that: The conditions for the first microwave treatment in step (b) are as follows: microwave power is 500~900W, and the treatment time is 0.5~3.0h; the conditions for the second microwave treatment are as follows: microwave power is 500~800W, and the treatment time is 1.0~4.0h.

11. The method according to claim 7, characterized in that: The alkaline solution in step (b) is an aqueous solution of potassium hydroxide and / or sodium hydroxide, with a mass concentration of 5.0% to 40.0%; the volume ratio of the alkaline solution to the total volume of graphene oxide and the strip carrier is 1.5:1 to 2.5:

1.

12. The method according to claim 7, characterized in that: The impregnation solution containing Cu and / or Ni is an aqueous solution prepared from soluble copper salts and / or nickel salts, which are one or more of chlorides, sulfates, acetates, and nitrates.

13. The method according to claim 1, characterized in that: The liquefied petroleum gas (LPG) desulfurization catalyst requires reduction before use. The reduction conditions are as follows: under a hydrogen-containing atmosphere, the active metal oxide is converted into an elemental metal, while the metal oxide in the support remains unchanged. The reduction conditions are: pressure 0.5 MPa–2.0 MPa, temperature 100°C–550°C, and feed volume hourly space velocity (VHSV) 0.1 h⁻¹. -1 ~20.0h -1 The volume ratio of hydrogen to catalyst is 10:1 to 100:1.

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