RU2080176C1 - Catalyst for oxidizing sulphur dioxide - Google Patents

Abstract

FIELD: inorganic chemistry; may be used for sulfuric acid production from gaseous mixtures with normal or elevated sulphur dioxide content. SUBSTANCE: catalyst uses as carrier mixture of diatomite and powdery silica wastes resulting from silicon production, diatomite and silica taken, respectively, in ratio of (0.2-0.4):(0.6-0.8). Catalyst comprises the following components, mas.%: $$$, 6-10; $$$, 8-12; sulphur compounds (in terms of $$$, 8-20); carrier, the balance. Catalyst is active in oxidizing sulphur dioxide. Conversion degree of $$$ at V=4000 $$$ and at 485 C is equal to 86-88% using gaseous mixture with the following composition: 10% by volume $$$; air, the balance. Crushing strength of catalyst is 1.5-2.2 MPa. EFFECT: higher efficiency. 1 tbl

Description

 The invention relates to catalysts for the oxidation of sulfur dioxide and can be used in the production of sulfuric acid in the processing of gas mixtures with a normal and high content of sulfur dioxide.

A known catalyst for the oxidation of sulfur dioxide, consisting of vanadium pentoxide with the addition of alkaline promoters of compounds of sodium, potassium, rubidium and (or) cesium on a carrier diatomite containing SiO ₂ , CaO.

The mixture of alkaline promoters in terms of oxides contains, by weight. Na ₂ O 5-30; Rb ₂ O and / or Cs ₂ O 15-35; K ₂ O 8-35.

The activity of the catalyst at 485 ^o C 90.2-91% at 420 ^o C 57.8-59.7% when tested under the following conditions: V 4000 h ^-1 , the content of sulfur dioxide in the initial gas mixture of 7 vol. the rest is air. Mechanical crush strength 1-2 MPa [1]
Closest to the invention in technical essence is a vanadium-potassium catalyst supported on diatomite for the oxidation of sulfur dioxide containing, by weight.

V ₂ O ₅ 6-7
K ₂ O 9-11
Sulfates in terms of SO $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ 18-19
Diatomite Rest
The activity of the catalyst is 84-86% at 485 ^o C, 18-22% at 420 ^o C when tested under standard conditions: V 4000 h ^-1 , the content of sulfur dioxide in the initial gas mixture of 10 vol. the rest is air. Mechanical crush strength 1.0-1.4 MPa [2]
The disadvantage of this catalyst is the need to use diatomite as a carrier of scarce natural material and lower activity and strength.

 This development allows to replace scarce natural raw materials, increase the activity and strength of the catalyst.

 This is achieved through the use of a mixture of diatomite and pulverized silica waste as a carrier in the production of silicon in the ratio, respectively (0.2-0.4) (0.6-0.8) with the following components in the catalyst, wt.

V ₂ O ₅ 6-10
K ₂ O 8-12
Sulphates (in terms of SO $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ ) carrier Else
The essence of the invention lies in the fact that a mixture of diatomite and pulverized silicate waste, i.e. the deficient diatomite of the Kisatiba deposit (Georgia) is partially replaced. There is no similar material in Russia.

It is very important to observe a certain amount of diatomite introduced into the carrier. This is due to the fact that diatomite contains Al ₂ O ₃ , which is much more heat-resistant compared to SiO ₂ . Due to this, the process of transformation of the porous structure is “inhibited”. The latter occurs due to the fact that silicon and vanadium compounds at high temperatures (calcination) form a eutectic melt, which, by the mechanism of solid-liquid sintering, changes the globular structure of the support (catalyst) and, accordingly, porosity.

The presence of MgO, P ₂ O ₅ , K ₂ O and Na ₂ O microadditives in the silicate waste, which are the promoting components of sulfuric acid contact masses, contributes to an increase in the activity of the catalyst.

 Thus, due to the specific chemical composition of the silicate waste and the quantitative ratio between it and diatomite in the carrier, an increase in the activity and mechanical strength of the catalyst is provided.

The proposed catalyst is active in the process of oxidation of sulfur dioxide. The degree of conversion of SO ₂ at V 4000 h ^-1 the gas mixture composition: 10 vol. SO ₂ , the rest of the air, is at 485 ^o C 85-87%
The crushing strength of the catalyst is 1.5-2.2 MPa.

Thermostability of the catalyst (degree of deactivation) 16-18%
The catalyst is prepared as follows. Dry powdered silica waste containing impurities of aluminum oxides (about 0.004 wt.), Magnesium (about 0.0035 wt.), Calcium (about 0.006 wt.), Sodium (about 0.0035 wt.), Potassium (about 0 , 0015 wt.) And phosphorus (about 0.92 wt.), Mixed with diatomite and vanadium pentaxide powder. The resulting mixture is added to a pre-prepared mixture of potassium hydroxide and sulfuric acid based on the production of potassium bisulfite. The contact mass after the introduction of plasticizing additives into it is thoroughly mixed and formed into cylindrical particles with a diameter of 4-5 mm and a length of 10-15 mm. Then the contact mass is dried at 100-120 ^o C for 2-4 hours and calcined for 1-2 hours at 500-600 ^o C.

The catalyst can be synthesized according to a slightly modified scheme, namely: using a solution of potassium metavanadate with a concentration of 135-150 g / dm ³ V ₂ O ₅ , previously prepared by leaching of technical ore V ₂ O ₅ with a solution of caustic potassium with a concentration of 40-45% s the subsequent addition of a certain amount of potassium hydroxide and sulfuric acid to the potassium metavanadate solution based on the production of potassium bisulfate. In the mixture pour a mixture of pulverized silica waste and diatomite, taken in certain proportions. After the plasticizing additive is introduced into it, the contact mass is thoroughly mixed, molded, dried and calcined under the above conditions.

 Obtained in this way, the catalyst contains, based on oxides, wt.

V ₂ O ₅ 6-10
K ₂ O 8-12
Sulphates (in terms of SO $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ ) 8-20
Media 58-78
The crushing strength of the catalyst is 1.5-2.2 MPa. Thermostability of the catalyst (degree of deactivation) is 16-18%
The catalyst is tested for activity in the process of oxidizing sulfur dioxide in a flow-type installation according to the standard method at a gas flow rate of 4000 h ^-1 and with a sulfur dioxide content of 10 vol. In the feed gas mixture. the rest is air.

 The strength of the granules is determined in static conditions by crushing according to the generatrix according to the standard method (Mukhlenov I.P. Technology of catalysts. L. Chemistry, 1979, p. 324).

The thermal stability of the catalyst is assessed by the express method, which includes heat treatment of the catalyst for 10 hours with a gas-air mixture containing 15% sulfur dioxide and 15.75% oxygen at 700 ^o C, and measuring the activity of the sample by the standard method before and after heat treatment. Thermostability is estimated by the degree of deactivation.

 Example 1

To 70 g of pulverized silica waste and 30 g of diatomite add 12 g of vanadium pentaxide. The mixture is thoroughly mixed. 60.3 g of a 40% solution of H ₂ SO ₄ are mixed with 22.3 g of a solution of 45% KON. The resulting solution is stirred and a mixture of silica waste and diatomite with vanadium pentaxide is poured into it, 4.0 g of OP-7 grade surfactant plasticizer are introduced. The contact mass is thoroughly mixed, molded in the form of cylindrical granules with a diameter of 5 mm and a length of 10-15 mm. The granules are dried at 110 ^° C. for 3 hours and calcined at 550 ^° C. for 1.5 hours.

 Example 2

To 70 g of pulverized silica waste add 30 g of diatomaceous earth and mix the mixture thoroughly. In a 30 g solution of potassium metavanadate with a concentration of 150 g / dm ³ V ₂ O _5, 11.7 g of potassium hydroxide (100% of the target substance) are dissolved, then 20.3 g of 93% H ₂ SO ₄ are added. Stir the resulting mixture and pour into it a mixture of silica waste and diatomaceous earth, 4.0 g of OP-7 grade surfactant plasticizer are introduced. The contact mass is thoroughly mixed, molded in the form of cylindrical granules with a diameter of 5 mm and a length of 10-15 mm. The granules are dried at 110 ^° C. for 3 hours and calcined at 550 ^° C. for 1.5 hours.

 The synthesized catalyst contains, by weight.

V ₂ O ₅ 8
K ₂ O 10
Sulphates (in terms of SO $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ ) fourteen
Carrier (silica waste mixed with diatomite) 68
The oxidation state of sulfur dioxide on this catalyst under the above test conditions is 88% at 485 ^° C. The crushing strength of the granules is 2.2 MPa. Thermostability of the catalyst 16%
The summary table presents the characteristics of the chemical composition, activity, mechanical strength and thermal stability of the catalyst.

 As can be seen from the table, the proposed catalyst in activity and mechanical strength exceeds the known.

 The creation of a catalyst using a combined carrier significantly expands the raw material base of production.

Claims (1)

 A catalyst for the oxidation of sulfur dioxide containing vanadium pentoxide, potassium oxide, sulfur compounds and a silica support, characterized in that the catalyst contains a mixture of diatomite and silica fume from silicon production in a ratio of 0.2-0.4 0.6 0, respectively , 8 in the following ratio of components, wt. Vanadium Pentoxide 6 10
Potassium oxide 8 12
Sulfur compounds (in terms of SO $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ ) 8 20
Media Remaining

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