The preparation method of catalyst for the oxidation of sulfur dioxide

 

(57) Abstract:

The invention relates to the field of chemistry inorganic substances and the production of mineral fertilizers, in particular can be used in the synthesis of sulfuric acid. The described method of preparation of the catalyst the conversion of SO2in SO3including the deposition of SiO2of liquid glass with sulfuric acid under constant deposition conditions of pH 5 to 7, t = 20 5oC, the deposition rate of 60 - 90 g/LCH , mixing the components of the catalyst, drying the catalyst slurry, forming and heat treatment, characterized in that the use of precipitated SiO2washed out from the sodium salt content of not more than 3 wt.% sodium salts in PA2O, and at the stage of mixing the active components in the catalyst slurry is injected 5 to 10 wt.% liquid sodium glass of dry substances, which improves the porous structure of the catalyst. The technical result is improved performance of the catalyst, in particular strength and activity at low (420oC) temperatures. table 1.

The invention relates to the field of chemistry inorganic substances and the production of mineral fertilizers and can be used in the synthesis of sulfuric acid.

images sulfuric acid by introducing into the resulting suspension, additional silica carrier, impregnation with solutions of active ingredients, drying the slurry, forming and heat treatment. In this case, the deposition of hydrocephalia lead in the transient mode by prilipanie sulfuric acid to the slurry containing dissolved silica, changing the pH of the medium from 13.5 to 5.5 [Patent RU N 2135282 C1 "Method of preparation of the catalyst the conversion of SO2in SO3, CL 01 J 37/02, 23/22, bull. N 24, 1999].

In the transient mode of deposition of all the main characteristics of the process (pH, temperature, concentration) are variable, so the porous structure of the gel varies in a wide range. To reproduce the process is virtually impossible, since the process parameters AC, and hence the quality of the product is non-stationary. Hydrocerol is not reproducible raznorodnosti patterns. This causes the irreproducibility of the quality of the catalyst as strength and catalytic activity, which is a significant disadvantage of this method.

Closest to the invention to the technical essence is "a Method of preparation of the catalyst for oxidation of sulfur dioxide" [A. S. SU 1785733 CL 01 J 37/04, 23/22, bull. N 1, 1993]. The method includes mixing the suspension SiO2with Vanadate natrional water glass and sulfuric acid at constant pH, the temperature and concentration of silica in suspension. While maintaining the basic technological parameters of deposition constant formed a relatively homogeneous globular structure. Usually you can get the specified size by changing the deposition conditions. The media has a defined pore size with a good reproducibility.

However, because the catalyst for the conversion of SO2in SO3works in a diffuse field, when the process speed is determined by the rate of supply of reactants to the inner surface of the catalyst and removal of the products of the reaction, the catalyst should be as thin and large pores, i.e., biporous structure. The formation of large pores is provided by adding powdered silica in suspension svezheosazhdennoi silica gel. However, this produces polydisperse porous structure and decreases the strength of the catalyst.

The technical problem to obtain a catalyst biporous structure, providing a high catalytic activity and durability at a good reproducibility of the quality of the catalyst, is solved by following a number of technological methods, namely the method of preparation of the catalyst for akislenkov, synthetic silica obtained by precipitation from a liquid glass sulfuric acid solution at constant pH, temperature and concentration of the suspension, followed by drying the catalyst slurry, forming and heat treatment. At the stage of mixing the components in the catalyst slurry type liquid glass in an amount to provide a molar ratio in terms of oxide - oxide potassium oxide sodium: pentoxide vanadium is 2.7 to 3.5: 09-1,3: 1 and the sulfur trioxide: (potassium oxide + sodium oxide) is equal to 1,7-2,0.

The introduction of liquid glass in catalyst slurry leads to gelation and drying the formed product biporous structure. The size of the fine pores 100-300 and large pores around 2000 . The amount of small pores increases with increasing content of active components, whereas the size of large pores remains approximately constant.

The quantity of liquid introduced into the catalyst slurry is 5-10% of dry substances and depends on the degree of washing of precipitated SiO2the content of Na2O which should not exceed 3%. The limits of the quantity of injected liquid glass mixing of the components is based on the following regularities. With the introduction of less than 5% liquid steam with the requirement on the content of Na2O in the catalyst and, even with a high degree of washing of precipitated SiO2that 10% of the added liquid glass to provide the required number of Na2O in the catalyst.

In the proposed solution, suspension SiO2obtained by continuous precipitation at constant pH 5-7, the temperature of 15-25oC and deposition rate 60-90 g/l h for SiO2is approximately equal to the size of the globules, and hence the size of the fine pores in the aggregates. After washing the SiO2from the sodium salt content of not more than 3% Na2O the precipitate SiO2is used for preparing catalyst slurry at the stage of mixing the components, namely added potassium Vanadate, water glass and sulfuric acid. Gelation catalyst slurry is caused by coagulation of the polymer molecules of silicic acid formed during the neutralization of liquid glass with sulfuric acid. At the stage of drying the catalyst slurry character shrinkage due to gel-like structure of the pulp, provides education biporous structure of the product, which is a significant difference method from the known. Due to the presence of fine and coarse pores, the catalyst has high performance and good playback is Ivanyi solution of liquid sodium glass with a density of about 1.1 g/cm3and sulfuric acid with a flow rate of providing maintenance of the pH within 5-7 and deposition rate 60-90 g/l h for SiO2, washed with water from the sodium salt to the content of 2.8% Na2O. the Washed precipitate SiO2with humidity 77% in the amount of 1 kg mixed with 200 ml of a solution of potassium Vanadate concentration of 30 g/l of KOH and 160 g/l for V2O5and with stirring, add 43 ml of liquid sodium glass with the content of SiO2- 31%; Na2O - 11% and a density of 1.4 g/cm3that corresponds to 5.4% on a dry and 85 ml of a sulfuric acid concentration of 92%. After mixing, the slurry is dried, molded by extrusion, the pellets are dried and calcined. The catalyst has a composition, wt.%: V2O5- 7,1; K2O - 11,1; Na2O - 2,8; SO3- 27; media - the rest. The molar ratio of K2O : Na2O: V2O5= 3:1,2:1 and SO3: (K2O + Na2O) = 1,9. Properties of the catalyst are presented in the table.

Example 2. Sediment SiO2prepared generally in accordance with example 1 except for washing degree, which has provided the content of 1.2% Na2O SiO2. When mixing the components added 75 ml of liquid sodium glass, which corresponds to 9.5% on the dry, and 90 ml of sulfuric acid. The catalyst is from the group of K2O : Na2O : V2O5= 3 : 1,25 : 1, and SO3:(K2O + Na2O) = 1,7.

Example 3. Sediment SiO2prepared in accordance with example 2. When mixing the components add 250 ml of potassium Vanadate and 100 ml of sulfuric acid, the rest is similar to example 2. The catalyst has a composition, wt.%: V2O5- 7,8; K2O - 12,3; Na2O - 2,7; SO3- 27,2; media - the rest. The molar ratio of K2O : Na2O : V2O5= 3:1:1 and SO3:(K2O + Na2O) = 1,9.

The preparation method of catalyst for the oxidation of sulfur dioxide, comprising the mixing of solutions of active ingredients containing oxides of vanadium and alkali metal with a synthetic silica obtained by precipitation from a liquid sodium glass with sulfuric acid under constant deposition conditions: pH = 5 - 7, t = 20 5oC, the deposition rate of 60 - 90 g/LCH on Si02followed by drying the catalyst slurry, forming and heat treatment, characterized in that use synthetic silica containing not more than 3 wt. % of sodium salts in Na2O and by mixing components add liquid sodium glass, in an amount of 5 to 10 wt.% in terms of dry substances.

 

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FIELD: oxidation catalysts.

SUBSTANCE: SO2-into-SO3 conversion catalyst contains following active components: vanadium oxide, alkali metal (K, Na, Rb, Contains) oxides, sulfur oxides, and silica framework formed from natural and/or synthetic silica and having pores with radii up to 65000 , among which fraction of pores with radii larger 10000 does not exceed 50%, while content of sulfuric acid-insoluble vanadium compounds (on conversion to V2O5) does not exceed 4.0% by weight. Fraction of pores with radii 1000-10000 does not exceed 35% and that less than 75 at most 9%.

EFFECT: improved performance characteristics of catalyst operated in reactor zones at medium and maximum temperature due to under conditions activity at 420-530оС.

3 cl, 1 tbl, 8 ex

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