Bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at low temperature

Abstract

The present invention relates to a bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at a low temperature, which is prepared by using an Al.sub.2O.sub.3SiO.sub.2 composite oxide as a carrier to support bimetallic active components vanadium and nickel. The bimetallic mercaptan conversion catalyst has a proper specific surface area and more metal active center sites, and has advantages of simple preparation, an efficient mercaptan conversion ability even at a low temperature, and causing no saturation and polymerization of olefins. The bimetallic mercaptan conversion catalyst exhibits superior mercaptan conversion performance in LPG sweetening, has strong adaptability to starting materials, and can also nearly completely remove trace carbonyl sulfide contained in LPG.

Claims

1. A method for preparing a bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at a low temperature, comprising the following steps: (1) mixing 60-80 parts by mass of aluminum hydroxide xerogel and 20-40 parts by mass of silica xerogel uniformly, adding a pore-forming agent and an aqueous nitric acid solution thereto, followed by mixing and kneading, and then extruding the resultant to produce a formed article, wherein the pore-forming agent is in an amount of 3-5 wt % with respect to the total mass of the mixture of the aluminum hydroxide xerogel and the silica xerogel, wherein the aqueous nitric acid solution is in an amount of 70-80 wt % with respect to the total mass of the mixture of the aluminum hydroxide xerogel and the silica xerogel, and wherein the aqueous nitric acid solution has a concentration of 5-10 wt %, on a mass percentage basis; (2) air-drying the formed article by placing it at room temperature for 8-15 hours, drying it at 90-120 C. for 3-5 hours, then calcinating it for 3-8 hours by elevating the temperature to 450-620 C. at a heating rate of 2-4 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of 4-6 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier; and (3) loading bimetallic active components, vanadium and nickel, separately onto the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier by using an isometric impregnation method, and then drying and calcinating it to obtain the bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at a low temperature.

2. The method according to claim 1, wherein the Al.sub.2O.sub.3SiO.sub.2composite oxide carrier has a specific surface area of 150-330 m.sup.2/g and a pore size of 4-12 nm.

3. The method according to claim 1, wherein step (3) comprises: i) adding a solution containing a soluble salt of vanadium dropwise onto the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier, then placing it at room temperature for 6-12 hours, drying it at 90-120 C. for 3-5 hours, and calcinating it at 420-550 C. for 3-6 hours, to obtain a catalyst intermediate; and ii) adding a solution containing a soluble salt of nickel dropwise onto the catalyst intermediate, then placing it at room temperature for 6-12 hours, drying it at 90-120 C. for 3-5 hours, and calcinating it at 420-550 C. for 3-6 hours, to obtain the bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at a low temperature.

4. The method according to claim 3, wherein the soluble salt of vanadium includes one or more of ammonium metavanadate, sodium metavanadate, potassium metavanadate, vanadium acetylacetonate and sodium orthovanadate.

5. The method according to claim 3, wherein the soluble salt of nickel includes one or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, nickel oxalate and nickel acetylacetonate.

6. The method according to claim 1, wherein the total content of the bimetallic active components measured on the basis of the weight of oxides is 10-40 wt % of the bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at a low temperature.

7. The method according to claim 6, wherein the total content of the bimetallic active components measured on the basis of the weight of oxides is 12-30 wt % of the bimetallic mercaptan conversion catalyst for sweetening liquefied petroleum gas at a low temperature.

8. The method according to claim 1, wherein the molar ratio of vanadium to nickel is (0.1-0.8):1.

9. The method according to claim 1, wherein, in step (1), the extruded formed article is a clover-shaped long-rod-like formed article having a diameter of 1-3 mm or a cylindrical long-rod-like formed article having a diameter of 1-3 mm.

10. The method according to claim 1, wherein the pore forming agent is sesbania powder.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) The technical solutions of the present invention will now be further described in details in order to provide a clearer understanding of the technical features, purposes and advantageous effects of the present invention, while the description is not to be construed as limitations to the implementable scope of the present invention.

EXAMPLE 1

(2) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(3) (1) mixing 30 g of aluminum hydroxide xerogel and 20 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(4) (2) air-drying the cylindrical formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 6 hours by elevating the temperature to 480 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(5) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(6) weighing out 2.64 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 430 C. at a heating rate of 2 C./min, to obtain a catalyst intermediate;

(7) weighing out 13.98 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 430 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst A.

EXAMPLE 2

(8) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(9) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(10) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(11) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(12) weighing out 2.64 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min, to obtain a catalyst intermediate;

(13) weighing out 13.98 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst B.

EXAMPLE 3

(14) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(15) (1) mixing 40 g of aluminum hydroxide xerogel and 10 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(16) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 560 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(17) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(18) weighing out 2.64 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 520 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(19) weighing out 13.98 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 520 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst C.

EXAMPLE 4

(20) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(21) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(22) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(23) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(24) weighing out 1.17 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(25) weighing out 7.08 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst D.

EXAMPLE 5

(26) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(27) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(28) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(29) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(30) weighing out 3.96 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(31) weighing out 9.98 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst E.

EXAMPLE 6

(32) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(33) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(34) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(35) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(36) weighing out 3.47 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(37) weighing out 16.83 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst F.

EXAMPLE 7

(38) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(39) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder into the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(40) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(41) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(42) weighing out 2.75 g of sodium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(43) weighing out 11.42 g of nickel chloride hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel chloride, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst G.

EXAMPLE 8

(44) This Example provides a bimetallic mercaptan conversion catalyst which was prepared by steps of:

(45) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder into the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(46) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(47) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(48) weighing out 1.32 g of ammonium metavanadate and 1.56 g of potassium metavanadate and dissolving them in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(49) weighing out 5.71 g of nickel chloride hexahydrate and 5.98 g of nickel acetate tetrahydrate and dissolving them in 16.0 g of deionized water to formulate a solution containing nickel, adding the solution slowly onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the bimetallic mercaptan conversion catalyst H.

COMPARATIVE EXAMPLE 1

(50) This Example provides a catalyst which was prepared by steps of:

(51) (1) adding 2 g of sesbania powder to 50 g of aluminum hydroxide xerogel and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(52) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3 carrier;

(53) (3) separately loading bimetallic active components, vanadium and nickel, by using an isometric impregnation method, comprising:

(54) weighing out 2.64 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3 carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min to obtain a catalyst intermediate;

(55) weighing out 13.98 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the catalyst intermediate under continuous stirring to mix the impregnation solution and the intermediate uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the catalyst I.

COMPARATIVE EXAMPLE 2

(56) This Example provides a catalyst which was prepared by steps of:

(57) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(58) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(59) (3) loading the bimetallic active component vanadium by using an isometric impregnation method, comprising:

(60) weighing out 2.24 g of ammonium metavanadate and dissolving it in 16.0 g of an oxalic acid solution having a concentration of 20 wt % to formulate a solution containing the active metal vanadium, adding the solution slowly dropwise onto 20 g of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it for 4 hours in a muffle furnace by elevating the temperature to 480 C. at a heating rate of 2 C./min, to obtain the catalyst J.

COMPARATIVE EXAMPLE 3

(61) This Example provides a catalyst which was prepared by steps of:

(62) (1) mixing 35 g of aluminum hydroxide xerogel and 15 g of silica xerogel uniformly, then adding 2 g of sesbania powder to the resultant mixture and mixing them uniformly, further adding dropwise 37.5 g of an aqueous nitric acid solution having a concentration of 5 wt % and kneading it uniformly with the mixture, and forming a cylindrical formed article having a diameter of 3 mm by an extruder;

(63) (2) air-drying the extruded formed article produced in step (1) by placing it at room temperature for 14 hours, drying it at 100 C. for 5 hours, then calcinating it for 4 hours by elevating the temperature to 520 C. at a heating rate of 2 C./min, and subsequently crushing and screening the resultant to produce short-rod-like particles having a size of about 5 mm, thereby producing an Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier;

(64) (3) loading the bimetallic active component nickel by using an isometric impregnation method, comprising:

(65) weighing out 12.67 g of nickel nitrate hexahydrate and dissolving it in 16.0 g of deionized water to formulate a solution of nickel nitrate, adding the solution slowly dropwise onto the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier produced above under continuous stirring to mix the impregnation solution and the carrier uniformly, then placing it at room temperature for 12 hours, subsequently drying it at 120 C. for 4 hours, and finally calcinating it at 480 C. for 4 hours, to obtain the catalyst K.

(66) The catalysts A to K as produced by the above Examples and Comparative Examples were evaluated by using a micro fixed bed reactor, in which the loading amount of catalyst was 4.0 g, and both ends of the bed were filled with quartz sand when the catalyst was loaded.

(67) Prior to the reaction, the catalysts need pre-sulfidation, in which straight-run gasoline was used as the pre-sulfidation oil, CS.sub.2 was used as the sulfidation agent at a concentration of 2.0 wt % in the straight-run gasoline (on a mass percentage basis), the pre-sulfidation oil was run under a volume hourly space velocity of 1.5 h.sup.1, the pre-sulfidation pressure was 2.0 MPa, and the volume ratio of hydrogen to oil was 250. The pre-sulfidation process was as follows: performing sulfidation at 230 C. for 3 h, at 270 C. for 3 h, at 300 C. for 4 h, at 320 C. for 4 h, and at 340 C. for 2 h, with a heating rate of 1 C./min during the sulfidation.

(68) After the pre-sulfidation of the catalysts, LPG starting materials were fed when the temperature decreased to a reaction temperature, and under the condition of a temperature of 80 C., a pressure of 2.5 MPa, a volume hourly space velocity of 3.0 h.sup.1 and a hydrogen-to-oil volume ratio of 6, the reaction was carried out stably for 20 hours and was sampled every 5 hours for analysis.

(69) The content of sulfides in the sample was measured using a gas chromatography-sulfur chemiluminescence detector (GC-SCD), and the conversion of sulfides was calculated. The results are listed in Table 1 (A comparison of reaction performance of the catalysts between Examples and Comparative Examples). The starting material used was LPG which was measured to have a methyl mercaptan content of 164.39 g/g, an ethyl mercaptan content of 85.6 g/g and a carbonyl sulfide content of 28.95 g/g.

(70) As can be seen from the results given in Table 1, catalysts A to H each showed a strong ability to remove methyl mercaptan and ethyl mercaptan contained in the starting materials when the starting material LPG passed through the catalyst bed at 80 C. As for the two mercaptans contained in LPG catalysts A to H prepared in the Examples showed optimal conversion efficiency for methyl mercaptan, all at 98% or more, and showed a suboptimal conversion ability for ethyl mercaptan, yet the best mercaptan conversion among which was still greater than 98%. In particular, the catalysts prepared in the Examples also showed a remarkable removing effect on a trace amount of carbonyl sulfide contained in LPG with the highest removing rate being 99% or more. The composition of the Al.sub.2O.sub.3SiO.sub.2 composite oxide carrier and the calcination temperature thereof (catalysts A to C and I) had a certain effect on the mercaptan conversion performance of the catalyst products. The catalysts prepared with Al.sub.2O.sub.3SiO.sub.2 composite oxide as the carrier showed better mercaptan conversion performance than the catalyst prepared with Al.sub.2O.sub.3 alone as the carrier, because addition of SiO.sub.2 facilitates formation of SiAl bonds so that additional acidic sites are generated, which promote low-temperature activation of mercaptans. Different calcination temperatures affect the number and intensity of acidic sites on the composite oxide carrier to different degrees, which results in difference in mercaptan conversion performance of the catalyst products.

(71) TABLE-US-00001 TABLE 1 Comparison of reaction performance of the catalysts in Examples and Comparative Examples Concentration of sulfocompound in the product (g/g) Methyl Ethyl Carbonyl Examples Catalysts mercaptan mercaptan sulfide 1 A 0.45 2.94 0.71 2 B <0.1 1.12 0.13 3 C 0.24 2.13 0.46 4 D 2.38 6.22 1.52 5 E 1.64 5.84 1.24 6 F 0.13 1.69 0.17 7 G 0.30 2.72 0.61 8 H 0.17 1.97 0.20 Comparative I 0.72 3.16 0.74 Example 1 Comparative J 4.14 12.26 1.78 Example 2 Comparative K 48.68 37.5 6.96 Example 3

(72) In addition, as can be seen from Table 1, the loading amounts of V.sub.2O.sub.5 and NiO, the V/Ni molar ratio, and the types of the active metal-containing starting materials all have certain effects on the mercaptan conversion efficiency of the catalysts. A low total loading amount of active metal (catalyst D) and an improper V/Ni molar ratio (catalyst E) are both unfavorable to formation of active centers, thereby decreasing the mercaptan conversion ability of catalysts. Among the catalysts in the above Examples, catalyst B showed the best mercaptan conversion performance, with a methyl mercaptan conversion of >99.9%, an ethyl mercaptan conversion of 98.69%, and a carbonyl sulfide conversion of 94.75%.

(73) As can be seen from the evaluation results of the catalysts in the Comparative Examples, the catalyst supporting V.sub.2O.sub.5 alone and the catalyst supporting NiO alone both had reduced mercaptan conversion performance, in which the catalyst supporting V.sub.2O.sub.5 showed the worst sweetening performance with a methyl mercaptan conversion of only 70.39%, an ethyl mercaptan conversion of only 56.19% and a carbonyl sulfide conversion of only 75.96%. As such, the synergistic effect between the metals V and Ni is the key factor for a bimetallic mercaptan conversion catalyst to have superior mercaptan conversion performance.

(74) In summary, the bimetallic mercaptan conversion catalyst prepared according to the preparation method provided in accordance with the present invention has a proper specific surface area and number of active center sites, and has advantages of simple preparation, an efficient mercaptan conversion ability even at a low temperature, and causing no saturation and polymerization of olefins. Moreover, the bimetallic mercaptan conversion catalyst exhibits superior mercaptan conversion performance, has strong adaptability to starting materials, and can also nearly completely remove trace carbonyl sulfide contained in LPG. The catalyst provided in accordance with the present invention has prominent low-temperature catalytic activity and good catalytic stability, as compared to catalysts in the prior art.