Vanadium-based catalyst and preparation method therefor

Abstract

A vanadium-based catalyst comprises an active phase carried on a carrier. The active phase comprises vanadium oxide, potassium sulfate, sodium sulfate, and assistants. The carrier comprises ultra-large-pore silicon dioxide and diatomite, the average pore size of the ultra-large-pore silicon dioxide ranges from 100 nm to 500 nm, and the diatomite is a refined diatomite having a silicon dioxide content of higher than 85% after refinement. The preparation method for the vanadium-based catalyst comprises: 1) mixing potassium vanadium and potassium hydroxide, and allowing a prepared mixed solution and sulfuric acid to carry out a neutralization reaction; and 2) mixing a neutralization reaction product in step 1) with the carrier and sodium sulfate, and carrying out rolling, band extrusion, drying and roasting to prepare the vanadium-based catalyst, assistant compounds being added in step 1) and/or step 2).

Claims

1. A vanadium-based catalyst, comprising: an active phase loaded on a carrier, wherein the active phase comprises vanadium oxide, potassium sulfate, sodium sulfate, and an auxiliary agent, and the carrier comprises an ultra-large-pore silica and a diatomite, wherein the ultra-large-pore silica has an average pore diameter ranging from 100 to 500 nm, and the diatomite is a purified diatomite having a silica content of more than 85%.

2. The vanadium-based catalyst according to claim 1, wherein the ultra-large-pore silica has an average pore diameter ranging from 150 to 400 nm.

3. The vanadium-based catalyst according to claim 1, wherein the active phase is present in an amount ranging from 30% to 40% by weight, and the carrier is present in an amount ranging from 60% to 70% by weight.

4. The vanadium-based catalyst according to claim 1, wherein based on a total weight of the vanadium-based catalyst, vanadium oxide is present in an amount ranging from 6.5% to 8.5% by weight; a molar ratio of potassium element to vanadium element is (2.5-4.0):1; the auxiliary agent is present in an amount ranging from 0.5% to 2.0% by weight; and sodium sulfate is present in an amount ranging from 3.0% to 6.0% by weight.

5. The vanadium-based catalyst according to claim 1, wherein based on a total weight of the vanadium-based catalyst, the ultra-large-pore silica is present in an amount ranging from 8.0% to 20.0% by weight.

6. A method for preparing a vanadium-based catalyst according to claim 1, comprising steps of: 1) mixing potassium vanadate and potassium hydroxide to form a mixed solution, and subjecting the mixed solution and sulfuric acid to a neutralization reaction; and 2) mixing a product of the neutralization reaction in step 1) with a carrier and sodium sulfate to form a mixture, and subjecting the mixture to grinding, pressing, extruding, drying, and roasting to prepare a vanadium-based catalyst, the carrier comprising an ultra-large-pore silica and a diatomite, wherein the ultra-large-pore silica has an average pore diameter ranging from 100 to 500 nm, and the diatomite is purified diatomite having a silica content of more than 85%; and wherein an auxiliary compound is added in step 1) and/or step 2).

7. The method according to claim 6, wherein in step 1), potassium sulfite is added in preparing the mixed solution.

8. The method according to claim 7, wherein the molar ratio of potassium sulfite to potassium vanadate is in a range of 1:(0.9-1).

9. The method according to claim 6, wherein in the carrier, the weight ratio of the ultra-large-pore silica to the diatomite is in a range of (6-20):(40-55).

10. The method according to claim 9, wherein in the carrier, the weight ratio of the ultra-large-pore silica to the diatomite is in a range of (8-18):(40-52).

11. The method according to claim 6, wherein preparation of the ultra-large-pore silica comprises a step of using colloidal microspheres of polystyrene having a particle diameter ranging from 120 to 550 nm in a silica sol.

12. The method according to any claim 6, wherein the auxiliary compound is at least one selected from a group consisting of a phosphorus-containing compound and a cesium-containing compound.

13. The method according to claim 12, wherein the auxiliary compound is at least one selected from a group consisting of phosphoric acid, cesium hydroxide, and cesium sulfate.

14. A method for preparing SO.sub.3 by oxidizing SO.sub.2, comprising: contacting a gas stream containing SO.sub.2 with a catalyst according to claim 1, to obtain a gaseous product containing SO.sub.3.

15. A method for preparing SO.sub.3 by oxidizing SO.sub.2, comprising: contacting a gas stream containing SO.sub.2 with a catalyst prepared according to the method of claim 6, to obtain a gaseous product containing SO.sub.3.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The embodiments of the present invention will be described in detail below with reference to examples, by way of which one can fully understand the implementing process as to how the present invention uses technical means to solve technical problems and achieve technical effects and can thus implement the process based on such understandings. It should be noted that, as long as there is no conflict, examples of the present invention and features of the examples may be combined with one another, and technical solutions formed are all within the protection scope of the present invention.

(2) In the following examples, test materials used include:

(3) Northeast China diatomite: CB05 produced by Jilin Changbai Diatomite Co., Ltd.;

(4) Yunnan diatomite: YX04 produced by Yunnan Diatomite Products Factory; and

(5) Zhejiang diatomite: CD02 produced by Shengzhou Huali Diatomite Products Co., Ltd.

(6) In order to meet requirements for the diatomite as a carrier, natural diatomite must be processed to reduce the contents of clay minerals and detrital minerals to increase the proportion of diatom shells. Purified diatomite is usually prepared by subjecting raw diatomite to beating and cyclonic separation, and then treating the resulted diatomite with sulfuric acid.

(7) Other test materials not listed are all commercially available products.

(8) According to the present invention, the average pore diameter is average pore diameter measured and calculated according to a mercury intrusion method (GBT 21650.1 mercury intrusion method and gas adsorption method for measuring pore diameter distribution and porosity of a solid material, Part 1: mercury intrusion method).

PREPARATION EXAMPLE 1

(9) 75 g of tetramethoxysilane (TMOS) and 65 g of methanol were added to a 250-mL three-necked flask equipped with a stirrer and a reflux condenser, and stirred well. Hydrochloric acid having a certain concentration was added to the reaction flask, followed by introduction of N.sub.2. The resultant mixture was heated to a reflux temperature to react for 2 hours, and finally cooled naturally to room temperature, to obtain a colorless transparent SiO.sub.2 sol.

(10) Colloidal microspheres of polystyrene having particle diameters ranging from 260 to 280 nm were immersed in the SiO.sub.2 sol for 10 minutes, and subjected to suction filtration. After the suction filtration, the filtered solid was dried at 70 C. for 60 minutes. The above immersion, suction filtration, and drying processes were repeated 3 times. The dried product after treatment was placed in a tube furnace, heated to 300 C. at a rate of 3 C./min under a condition of introducing air and kept at 300 C. for 4 hours, then heated to 600 C. and kept at 600 C. for 3 hours, and finally cooled naturally to obtain an ultra-large-pore silica having an average pore diameter of 240 nm.

PREPARATION EXAMPLE 2

(11) An ultra-large-pore silica was prepared in the same manner as in Preparation Example 1, except that the colloidal microspheres of polystyrene had particle diameters ranging from 170 to 180 nm, and the prepared ultra-large-pore silica had an average pore diameter of 150 nm.

PREPARATION EXAMPLE 3

(12) A transparent SiO.sub.2 sol was prepared in a ratio of n(Si(OEt).sub.4):n(EtOH):n(HCl):n(H.sub.2O)=1:3.9:0.3:1.8 and with tetraethyl orthosilicate as a silicon source. The SiO.sub.2 sol was added dropwise to colloidal microspheres of polystyrene having particle diameters ranging from 320 to 340 nm, and subjected to suction filtration. After the suction filtration, the filtered solid was dried at 60 to 70 C. for 60 minutes, which was repeated several times. The solid, under programmed temperature rise control and under a condition of introducing air, was slowly heated (<5 C./min) to 300 C. and kept at 300 C. for 5 hours, then heated to 570 C. and kept at 570 C. for 5 hours, and finally cooled to obtain an ultra-large-pore silica having an average pore diameter of 300 nm.

PREPARATION EXAMPLE 4

(13) An ultra-large-pore silica was prepared in the same manner as in Preparation Example 3, except that the colloidal microspheres of polystyrene had particle diameters ranging from 420 to 445 nm, and the prepared ultra-large-pore silica had an average pore diameter of 400 nm.

EXAMPLE 1

(14) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. The prepared vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.7. Then, 30.1 ml of the vanadium water was neutralized with 17.9 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio of being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate, 3.7 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 8.0 g of the ultra-large-pore silica prepared in Preparation Example 1, and 59.8 g of purified Northeast China diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(15) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.0 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.7 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 3.7 wt %; P.sub.2O.sub.5 was present in an amount of 1%; the ultra-large-pore silica was present in an amount of 8.0 wt %; and the rest was purified Northeast China diatomite.

EXAMPLE 2

(16) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. The prepared vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 4.0. Then, 28.2 ml of the vanadium water was neutralized with 18.2 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate, 4.1 g of Na.sub.2SO.sub.4, 0.9 g of cesium sulfate, 13.0 g of the ultra-large-pore silica prepared in Preparation Example 2, and 52.7 g of purified Yunnan diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(17) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.5%; K.sub.2O/V.sub.2O.sub.5 was 4.0 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 4.1%; cesium sulfate was present in an amount of 0.9%; the ultra-large-pore silica was present in an amount of 13.0%; and the rest was purified Yunnan diatomite.

EXAMPLE 3

(18) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. The prepared vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.5. Then, 30.8 ml of the vanadium water was neutralized with 17.4 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate, 5.5 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 18.0 g of the ultra-large-pore silica prepared in Preparation Example 3, and 47.0 g of purified Zhejiang diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(19) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.2 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.5 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 5.5 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; the ultra-large-pore silica was present in an amount of 18.0%; and the rest was purified Zhejiang diatomite.

EXAMPLE 4

(20) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. The prepared vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.8. Then, 29.3 ml of the vanadium water was mixed uniformly with 1.5 g of cesium hydroxide. The resultant mixture was neutralized with 19.1 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate, 3.1 g of Na.sub.2SO.sub.4, 10.6 g of the ultra-large-pore silica prepared in Preparation Example 4, and 55.5 g of purified Northeast China diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(21) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.8 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.8 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 3.1 wt %; cesium sulfate was present in an amount of 1.8 wt %; the ultra-large-pore silica was present in an amount of 10.6 wt %; and the rest was purified Northeast China diatomite.

EXAMPLE 5

(22) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 71.2 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.5. Then, 30.8 ml of the vanadium water was neutralized with 22.4 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 5.5 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 18.0 g of the ultra-large-pore silica prepared in Preparation Example 1, and 47.0 g of purified Zhejiang diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(23) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.2 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.5 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 5.5 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; the ultra-large-pore silica was present in an amount of 18.0 wt %; and the rest was purified Zhejiang diatomite.

EXAMPLE 6

(24) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 67.7 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.2. Then, 29.3 ml of the vanadium water was neutralized with 19.9 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 6.0 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 11.2 g of the ultra-large-pore silica prepared in Preparation Example 2, and 58.8 g of purified Northeast China diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(25) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.8 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.2 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 6.0 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; the ultra-large-pore silica was present in an amount of 11.2 wt %; and the rest was purified Northeast China diatomite.

EXAMPLE 7

(26) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 69.5 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.7. Then, 30.1 ml of the vanadium water was neutralized with 22.8 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 3.7 g of Na.sub.2SO.sub.4, 1.6 g of cesium sulfate, 8.0 g of the ultra-large-pore silica prepared in Preparation Example 1, and 57.9 g of purified Northeast China diatomite were added to a mill, uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(27) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.0 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.7 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 3.7 wt %; cesium sulfate was present in an amount of 1.6 wt %; the ultra-large-pore silica was present in an amount of 8.0 wt %; and the rest was purified Northeast China diatomite.

COMPARATIVE EXAMPLE 1

(28) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. The prepared vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 2.7. Then, 30.1 ml of the vanadium water was neutralized with 13.1 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate and 82.0 g of purified Northeast China diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(29) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.0 wt %; K.sub.2O/V.sub.2O.sub.5 was 2.7 (molar ratio); and the rest was purified Northeast China diatomite.

COMPARATIVE EXAMPLE 2

(30) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 69.5 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 2.7. Then, 30.1 ml of the vanadium water was neutralized with 18.0 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution and 82.0 g of purified Northeast China diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying, and roasting to produce 100 g of a vanadium-based catalyst.

(31) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.0 wt %; K.sub.2O/V.sub.2O.sub.5 was 2.7 (molar ratio); and the rest was purified Northeast China diatomite.

COMPARATIVE EXAMPLE 3

(32) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 65.1 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.5. Then, 28.2 ml of the vanadium water was neutralized with 20.5 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 3.5 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, and 73.5 g of purified Yunnan diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying and roasting to produce 100 g of a vanadium-based catalyst.

(33) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.5 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.5 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 3.5 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; and the rest was purified Yunnan diatomite.

COMPARATIVE EXAMPLE 4

(34) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. After dissolution, the resultant vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 2.7. Then, 30.1 ml of the vanadium water was neutralized with 13.1 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 1.5 g of Na.sub.2SO.sub.4, and 80.3 g of purified Zhejiang diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying and roasting to produce 100 g of a vanadium-based catalyst.

(35) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.0 wt %; K.sub.2O/V.sub.2O.sub.5 was 2.7 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 1.5 wt %; and the rest was purified Zhejiang diatomite.

COMPARATIVE EXAMPLE 5

(36) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 67.7 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.2. Then, 29.3 ml of the vanadium water was neutralized with 19.9 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 6.0 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 5.0 g of the ultra-large-pore silica prepared in Preparation Example 1, and 65.9 g of purified Northeast China diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying and roasting to produce 100 g of a vanadium-based catalyst.

(37) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.8 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.2 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 6.0 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; the ultra-large-pore silica was present in an amount of 5.0 wt %; and the rest was purified Northeast China diatomite.

COMPARATIVE EXAMPLE 6

(38) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. 67.7 g of potassium sulfite was added to the vanadium water and dissolved to obtain vanadium water having a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.2. Then, 29.3 ml of the vanadium water was neutralized with 19.9 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a mixed solution of VOSO.sub.4 and K.sub.2SO.sub.4. After that, the mixed solution, 6.0 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 11.2 g of large-pore silica (Type: Type IV; pore diameter: 40 to 50 nm), and 58.8 g of purified Northeast China diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying and roasting to produce 100 g of a vanadium-based catalyst.

(39) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.8 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.2 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 6.0 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; the large-pore silica was present in an amount of 11.2 wt %; and the rest was purified Northeast China diatomite.

COMPARATIVE EXAMPLE 7

(40) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. After dissolution, the resultant vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.2. Then, 30.1 ml of the vanadium water was neutralized with 15.5 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate, 1 ml of phosphoric acid, and 67.5 g of the ultra-large-pore silica prepared in Preparation Example 1 were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying and roasting to produce 100 g of a vanadium-based catalyst.

(41) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 8.0 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.2 (molar ratio); P.sub.2O.sub.5 was present in an amount of 1 wt %; and the rest was the ultra-large-pore silica.

COMPARATIVE EXAMPLE 8

(42) A mixed solution (referred to as vanadium water) of KVO.sub.3 and KOH was prepared by dissolving KOH with steam, and subjecting the dissolved KOH and V.sub.2O.sub.5 to a hot boiling condition. After dissolution, the resultant vanadium water had a concentration of V.sub.2O.sub.5 being 266 g/L, and a molar ratio of K.sub.2O/V.sub.2O.sub.5 being 3.2. Then, 28.2 ml of the vanadium water was neutralized with 14.6 ml of a sulfuric acid solution (the sulfuric acid solution was prepared by mixing concentrated sulfuric acid and water in a volume ratio being 1:1) to prepare a colloidal precipitate of V.sub.2O.sub.5 and K.sub.2SO.sub.4. After that, the colloidal precipitate, 6.0 g of Na.sub.2SO.sub.4, 1 ml of phosphoric acid, 30.0 g of the ultra-large-pore silica prepared in Preparation Example 1, and 38.6 g of purified Yunnan diatomite were added to a mill and uniformly mixed, followed by addition of water. The mixture was ground and pressed to form a malleable material, which was then subjected to extruding, drying and roasting to produce 100 g of a vanadium-based catalyst.

(43) In the vanadium-based catalyst, V.sub.2O.sub.5 was present in an amount of 7.5 wt %; K.sub.2O/V.sub.2O.sub.5 was 3.2 (molar ratio); Na.sub.2SO.sub.4 was present in an amount of 6.0 wt %; P.sub.2O.sub.5 was present in an amount of 1 wt %; the ultra-large-pore silica was present in an amount of 30.0 wt %; and the rest was the purified Yunnan diatomite.

TEST EXAMPLE 1

(44) The catalysts prepared in the above examples and comparative examples were prepared into catalyst samples having a particle diameter of 55 to 8 mm, and subjected to activity tests under the following conditions. The activity was expressed by the conversion rate of SO.sub.2. Results of the tests are shown in Table 3.

(45) The value of the conversion rate E of SO.sub.2 was expressed in %, and was calculated according to the following formula:

(46) $E=\frac{{}_1-{}_2}{{}_1\left(1-0.015{}_2\right)}100$

(47) In the formula, 1 is the value of the volume fraction of sulfur dioxide in the gas at the inlet of the reactor, and is expressed in %; 2 is the value of the volume fraction of sulfur dioxide in the gas at the outlet of the reactor, and is expressed in %.

(48) Converter: The converter used was a jacketed single-tube reactor having a tube diameter of 362 mm. A temperature thermocouple shell was located at a center of the converter. The temperature thermocouple shell had a diameter of 81.5 mm.

(49) Amount of catalyst loaded: 30 ml;

(50) Space velocity: 3600 h;

(51) Volume percentage of intake SO.sub.2: 10%; and the rest was air;

(52) System pressure: atmospheric pressure;

(53) Temperature of activity test: 440 C.

TEST EXAMPLE 2

(54) The strength was measured in accordance with HG/T 2782 Measurement of Crush Resistance of Fertilizer Catalyst Particles.

(55) TABLE-US-00003 TABLE 3 Results of Activity Tests Activity (Conversion Strength Samples rate of SO.sub.2) % (N/cm) Example 1 67.8 75 Example 2 64.2 70 Example 3 63.6 68 Example 4 64.5 66 Example 5 65.0 69 Example 6 65.5 71 Example 7 67.5 72 Comparative 55.0 52 Example 1 Comparative 58.8 57 Example 2 Comparative 60.4 60 Example 3 Comparative 56.4 54 Example 4 Comparative 60.6 64 Example 5 Comparative 59.8 61 Example 6 Comparative 51.2 35 Example 7 Comparative 56.1 48 Example 8

(56) As can be seen from Table 3, the vanadium catalysts prepared by the method of the present invention have a distinctly higher activity than the traditional vanadium-based catalysts, and can improve the conversion rate of SO.sub.2 when used in a converter of a sulfuric acid producing unit, thus satisfying the requirement for total conversion rate of SO.sub.2 in sulfuric acid production.

(57) While the embodiments of the present invention have been described as above, the described embodiments are merely for the purpose of understanding the present invention and are not intended to limit the present invention. Various modifications and variations in the form and details of the embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention. The protection scope of the present invention however is still subject to the scope defined by the appended claims.