The charge for preparation of a catalyst for the oxidation of sulfur dioxide to sulfur trioxide and its preparation

 

The invention relates to the production of vanadium catalysts for oxidation of sulfur dioxide to sulfur trioxide in the production of sulfuric acid by the contact method, in particular to the mixture to obtain a catalyst. Described mixture for the preparation of vanadium catalysts for oxidation of sulfur dioxide to trioxide in sulfuric acid production and the way of its reception. The mixture comprises, by wt.%: 6,0-11,0 pentoxide vanadium; of 7.3 20.0 potassium oxide; 0.3 to 6.3 sodium oxide; 22,0-36.5 sulfur trioxide; 0.2 to 5.0 polyethylene oxide; else - silica carrier, and as the carrier contains a silica-containing material, comprising the oxide of alkaline metal such as potassium or sodium, or a mixture thereof, in the amount of 0.3-20.0 wt.% in terms of dry product. Silica carrier is hydrocephaly or a mixture of hydrocephaly with powdered carrier imposed in an amount up to 85 wt.%, both used silica-containing material must include in the initial state, the oxides of potassium, or sodium, or a mixture in quantities that provide the claimed interval 0.3-20.0 wt.%. Effect: getting a charge for preparation of the catalyst of the oxidation of sulfur dioxide to trioxide having a high activity in the region is nl.

The invention relates to the production of vanadium catalysts for oxidation of sulfur dioxide to sulfur trioxide in the production of sulfuric acid by the contact method, in particular to the mixture to obtain a catalyst.

The oxidation of sulfur dioxide to sulfur trioxide in the sulfuric acid production in domestic and international practice carried out in the vanadium catalysts, representing vanadium compounds promoted sulfates of alkali metals deposited on a highly dispersed amorphous silica carrier. Modern sulfuric acid catalyst should have high activity and stability in a wide range of conditions to be implemented in industrial contact devices, where temperatures from 400 to 700oWith, and the ratio of SO3/SO2varies from 0 at the beginning of the first layer to 0.998 output from the contact apparatus in accordance with an increase in the conversion of sulfur dioxide by passing the gas mixture through the reactor. One of the most important areas of improvement sulfuric acid vanadium catalysts is increased activity and stability at low temperatures 380-420oWith that it is important to reduce the temperature at the inlet of the machine, the optimization process is covremennogo cooling layer in the reaction medium, for example, during shutdowns for preventive maintenance. It is known that for high activity and stability at low temperatures it is necessary that the active compounds (accountpayday V5+alkali metals) under the reaction conditions were in the form of a melt evenly distributed on the surface of the carrier in the form of a homogeneous film with a thickness of <2000 A. Recovery V5+to V4+and the selection of the melt more refractory and inactive compounds V4+should be minimized.

Known methods of improving the low-temperature activity vanadium catalysts by optimizing the composition of the active component, and above all nature and content of the used alkali promoters. So (U.S. Pat. USA 4193894, B 01 J 27/02, 01 17/68, 1979), known vanadium catalyst for oxidation of sulfur dioxide to trioxide at temperatures above 300oS, which use two types of promoters. The first promoter is an alkali metal selected from the group of: sodium, potassium, rubidium. The second promoter is a metal ion selected from the group of: aluminum, magnesium, yttrium, lanthanum, which slows the formation of active particles V4+. The disadvantages of the catalyst are nevysoko increases the cost of the catalyst.

In industrial catalysts as promoters, it is advisable to use a cheaper potassium and sodium promoters. To increase the activity and stability is important (a) to find the optimal ratio between the main active substances of K2O/Na2O/SO3/V2O5ensuring the formation of the melt in the reaction conditions; b) to ensure the homogeneity of the melt and evenly distribute it to the media.

To increase the activity and stability at low temperatures suggests methods for improving the uniformity of the melt of the active component on the carrier. So (U.S. Pat. RF 1043869, B 01 J 23/22, 01 17/69, 27.09.99), the proposed charge for the preparation of dopromotions potassium-sodium-vanadium catalyst, which comprises, by weight. %: 7.5-11.0 vanadium pentoxide, 7.26-20 potassium oxide, 0.27-6.26 sodium oxide, 25.53-36.6 sulfur trioxide, 0.2-5.0 polyethylene oxide and the rest is silicon dioxide. The disadvantages of the catalyst prepared from this mixture are not sufficiently high activity and stability at low temperature oxidation and low ratios of SO3/SO2.

Known methods of increasing the activity and stability at low temperature is at. RF 2186620, B 01 J 23/22, 01 17/69, 10.08.2002), there is a method of preparation of the catalyst of oxidation of SO2in SO3in order to improve the low-temperature activity and stability of catalyst in the short-term cooling layer in the reaction medium use medium with an optimal set of properties that reach at the stage of deposition of hydrocephaly when claimed in the patent temperatures, pH, concentrations of solutions and additional heat treatment svezheosazhdennoi of hydrocephaly at temperatures above 30oC. the Disadvantage of this method is not sufficiently high activity at low ratios of SO3/SO2.

The closest technical solution to the claimed is the invention (U.S. Pat. RF 1466056, B 01 J 23/22, 01 17/69, 27.01.2001), which offers a mixture of catalyst for the oxidation of sulfur dioxide to trioxide containing, by weight. %: vanadium pentoxide 6-11, potassium oxide 6.2-20, sodium oxide 0.1-6.3, sulfur trioxide 25.5-36, polyethylene oxide 1.0-5.0 and the rest of silicon dioxide as a carrier. With the purpose of obtaining a catalyst with increased activity at a temperature of 420oAnd low ratio in the gas mixture SO3/SO2=0.3 as silicon dioxide is used p-90 And pore volume of 0.6-1.2 cm3/g) and grain size (particle size in the range of 0.02-0.08 mm). The combination of optimal chemical composition and the optimum properties of the silica gel provides improved low-temperature activity and stability of catalysts prepared from this mixture. Disadvantages are poor rheological properties, causing difficulty in forming pellets of the catalyst, and insufficient activity of the catalyst at low temperature and low ratio SO3/SO2. In some cases, observed irreproducibility of the properties of the catalyst on the basis of the proposed charge.

The reason for these shortcomings is the heterogeneous distribution of active components in the structure of the media. Thus, according to [the Study of the distribution of vanadium and potassium vanadium catalyst for the oxidation of sulfur dioxide by electron probe." A. C. Shkarin, I. F. Ovsyannikova, N. G. Tatarnikov, A. A. Somehow, M. C. Goats. Kinetics and catalysis. So 17, vol.1, page 250, 1976; "the influence of the texture of the silica gel on the distribution of the active component vanadium in the catalysts of the oxidation of sulfur dioxide". L., Simon, V. A., Disco, K. Richter, G. Seplat. Kinetics and catalysis. So 24, the venue in silica carrier vanadium and alkali promoters. Moreover: (a) distribution of vanadium in the media more uniform than alkali metals; b) the irregularity is laid in the initial stages of the synthesis mixture and drying and is not completely eliminated at the subsequent stages of preparation; C) the non-uniformity depends on the properties of the medium and increases with increasing packing density and strength of the silica particles of the medium. Inhomogeneous distribution of the active substances can lead to local deviations of the chemical composition (for example, the ratios of M/V) from the optimal. This not only affects the reproducibility of the quality of individual samples of the catalyst, but can significantly reduce the low-temperature activity, especially at low temperatures and low ratios of SO3/SO2since the formation of inactive compounds V4+largely depends on the ratio between the alkaline promoter and vanadium. Because in accordance with literature data distribution of alkali metals in silica carrier is less uniform than the distribution of vanadium to improve need to improve the distribution of the alkaline promoter.

Object of the present invention is obtained the region of the low temperature reaction and low ratios of SO3/SO2in the reaction mixture.

The task is solved in that for the preparation of the charge, including a 6.0-11.0 wt. % of vanadium pentoxide, 7.3-20.0 wt.% of potassium oxide, 0.3-6.3 wt.% sodium oxide, 22.0-36.5 wt.% sulfur trioxide, 0.2-5.0 wt.% the polyethylene oxide, the rest - silica carrier, use a silica-containing material, comprising the oxides of an alkali metal such as potassium or sodium, or a mixture thereof, in the amount of 0.3-20.0 wt.% in terms of dry product.

Used silica-containing material, the content of the oxide of alkaline metal such as potassium or sodium, or a mixture thereof, is 0.3-20.0 wt. %. When smaller quantities are not provided with sufficient concentration of alkali promoter on one surface of the original silica carrier. A greater amount of alkali promoter in the original silica media already does not increase activity.

The mixture obtained by mixing the catalytically active substances, including pentoxide vanadium, oxides of alkali metals (sodium and/or potassium), sulfur trioxide and polyethylene oxide with a silica carrier, which is injected or hydrocephaly, containing not less than 0.3 wt.% oxide of potassium, or sodium, or mixtures thereof, calculated on the dry product, or the sodium, or their mixture, the mass fraction of powdered silica of not more than 85 wt.%, and the content in the silica carrier oxide potassium, or sodium, or a mixture thereof is 0.3-20.0 wt.% in terms of dry product.

Upon receipt of the charge portion of the oxides of alkali metals is introduced into the mixture in the composition of the silica carrier, and the rest needed to ensure the selected composition of the charge injected adding to the silica carrier is a mixture of the active compounds of vanadium, alkali metal and SO3. This method of getting the charge provides greater homogeneity of the active component and a more uniform distribution media, which reduces the possibility of local deviations of the chemical composition, in particular the ratio of M/V, in various places catalytic mass at the subsequent stages of preparation of the catalyst. This provides a high activity at low temperatures and ratios of SO3/SO2.

A distinctive feature is that the silica carrier is injected or hydrocephaly, or in the form of a mixture of hydrocephaly with powdered silica, and, hydrocephaly, and powdered silica containing oxides of alkali metals such as potassium, noamnesia and the content of oxides of alkali metals must ensure that the total content of potassium oxide, or sodium, or mixtures thereof in the silica carrier in the present interval 0.3-20.0 wt.%.

Hydrocephaly used to obtain the claimed mixture has a pH 5.5-9.0 and humidity 40-95%. The claimed interval of pH of hydrocephaly due to the relatively high content of alkali metals is not less than 0.3 wt.%. The claimed interval humidity hydrocephaly comprising 40-95%, optimal for fast smooth mixing of hydrocephaly with powdered silica and/or active compounds of vanadium and alkali metals.

Hydrocephaly used to prepare the claimed charge, get in the interaction of solutions of silicates of sodium and/or potassium, and solutions of acids such as sulphuric, nitric, hydrochloric, carbonic, or solutions of ammonium salts of these acids (NH4)2SO4, NH4NO3, NH4Cl, (NH4)2CO3, NH4The HCO3when the final pH 5.5 and 9.0, followed by filtration and washing of the hydrogel, silicic acid to a residual content of sodium oxide or potassium, or mixtures thereof in a quantity which provides the desired concentration of alkali metal oxide to silica carrier, but not less than 0.3 wt.% in pereschiwajut optimal properties of the silica carrier, such as particle size and density of their packing required to obtain highly active catalysts. Claimed in the invention a method of regulating the content of alkali metals on stage filtration and washing different technological simplicity, provides a relatively uniform distribution of the alkali metals in the media and the homogeneity of the phases by mixing such a carrier with the active compounds of vanadium and the rest of alkali promoters.

The hallmark of the invention is that used powdered silica contains an oxide of potassium, or sodium, or a mixture thereof in an amount necessary to achieve the specified content of alkali metal oxide to silica carrier, but not less than 0.3 wt.%. Powdered silica has a specific surface area of 20-500 m2/g, a bulk density of not more than 0.6 g/cm3the particle size of the powder 4-100 μm. The claimed interval values of the specific surface provides the distribution of the melt of the active component on the carrier surface as a relatively thin layer. Claimed in the invention, the bulk density of less than 0.6 g/cm3shows a relatively loose packing of the particles used in plemennoe distribution of the active compounds in the media vanadium catalysts, obtained by the method of mixing. The claimed interval size of the powder particles 4-100 μm provides a satisfactory molding properties of the catalyst pastes on the basis of the proposed charge, since it is known that the presence of large and solid particles in the catalyst paste affects the rheological properties of the moldable paste and reduces the strength of the finished products.

The invention is illustrated by the following examples.

Example 1 Illustrates the charge, which as silica carrier comprises silica-containing material, comprising the sodium oxide in the amount of 7.0 wt.% Na2O, calculated on the dry product.

The mixture is prepared as follows.

Hydrocephaly receive simultaneous draining 0.393 l of a solution of liquid sodium glass with a concentration of 100 g SiO2/l and 34 g of Na2O/l and 0.330 l solution of H2SO4with a concentration of 10 wt.% at a temperature of 255oC, pH 5.5, which provide for regulation of the speed of draining liquid glass and acid in the range of 20-50 ml/min Svezheosazhdennoi hydrocephaly subjected to aging in the mother solution at a temperature of 255oC for 1 hour, then washed the g H2Oh, which corresponds to 80% humidity hydrocephaly and the content of sodium oxide 7 wt.% Na2O, calculated on the dry product.

To 211 g hydrocephaly add a suspension of the active compounds, which is obtained by the addition of 48 ml of sulfuric acid solution with a concentration of 61.5 wt. % to 44 ml3VO4with a concentration of 170 g V2O5/l and 274 g2O/L. the resulting mixture is homogenized, dried at 150-200oWith the spray dryer, add 1.6 g of polyethylene oxide with a molecular weight 3x106. Get the charge, including 7.5 wt.% V2O5, 12.1 wt.% To2O, 3.0 wt.% Na2O, 36.5 wt.% SO3, 1.6 wt.% of polyethylene oxide and 39.3 wt.% SiO2.

To obtain a catalyst to the mixture add water to a moisture content of 40%, formed into granules which are then dried at 110-180oC and calcined in air at 500oC.

Example 2 Illustrates the charge, which consists of the silica-containing material such as a mixture of hydrocephaly and powdered silica, and the mixture contains potassium oxide in the amount of 18 wt.% To2Oh, This is achieved by: - contents2O hydrocephaly is 33 wt.% To2O, calculated on the dry product; - the share of hydroc the K2About; - the proportion of powdered silica is 63.1 wt.%.

The mixture is prepared as follows.

Hydrocephaly receive simultaneous draining 0.204 l of liquid potassium glass with a concentration of 100 g SiO2/l and 47.5 g2O/l and 0,300 l solution of H2SO4with a concentration of 10 wt.% at a temperature of 255oC, pH 9.0, which provide a speed control draining of liquid glass and acid in the range of 20-50 ml/min after deposition of hydrocephaly subjected to aging in the mother solution for 1 hour. Get 0.504 g hydrocephaly with humidity 94%, containing 20.4 g of SiO2and 9.7 g2About (i.e., in this silica material concentration To2O is 32 wt.% To2O).

To 0.504 l received hydrocephaly without washing or filtration, add powdered silica with a concentration of 0.86 wt.% To2About the number of 34.9, Get mixed media, in which the proportion of powdered silica is 63.1 wt.%, the total content of potassium oxide 18 wt.% To2About in terms of dry product.

To mixed media add a suspension of the active compounds, which are produced by adding 31.4 m/l and 50 g PA2O/L. the resulting mixture is homogenized and dried at 150-180oWith and add 1.5 wt. % of polyethylene oxide and receive a mixture containing 6.5 wt.% V2O5, 10.0 wt. %2Oh, 2.7 wt.% Na2O, 24 wt.% SO3, 1.5 wt.% of polyethylene oxide and 55.3 wt.% SiO2.

To obtain a catalyst to the mixture add water to a moisture content of 40%, formed into granules which are then dried at 110-180oC and calcined in air at 500oC.

Example 3 Same as example 1. Differs in that the use of silica media containing sodium oxide in the amount of 0.3 wt.% Na2O. the precipitated Hydrogel with a solution of nitric acid at pH 7.0.

Since the content of sodium oxide in the silica carrier is different from that in example 1, to ensure they remain on the composition of the charge change of the concentration of substances in the suspensions of the active compounds.

Example 4 Same as example 2. Different composition of the charge and the fact that the use of silica carrier containing the oxide of potassium in an amount of 20 wt.% To2Oh, the share of powdery silica is 85 wt.%, the content of potassium oxide is 0.3 wt.% To2O, the value of specific surface area 300 m2/g, a bulk density of 0.3 g/s is ammonium sulfate at pH 7.5.

Example 5 Same as example 1, characterized in that hydrographer produced by interaction of liquid glass and hydrochloric acid.

Example 6
Similar to example 1, characterized in that hydrographer produced by interaction of liquid ammonium acid carbonate and after filtering and washing hydrographer has a humidity of 40%.

Example 7
Similar to example 2, characterized in that the mixed silica carrier contains a mixture of oxides of alkali metals: potassium oxide in the amount of 17.8 wt.% and sodium oxide in the amount of 0.2 wt.%. Powdered silica has a specific surface area of 500 m2/g, a bulk density of 0.2 g/cm3particle size 4-30 μm.

Catalysts prepared on the basis of the charge obtained in examples 1-7, experience in the oxidation of sulfur dioxide to trioxide at a flow-circulation installation at a temperature of 420oWith, the composition of the initial gas mixture 7.5% vol. SO2, 11% vol. About2, 81.5% vol. N2, degree of conversion of SO2in SO3X= 30%, the ratio of SO3/SO2= 0.3/0.7, the granules of 0.5-1.0 mm Activity estimate for the reaction rate constant K[cm3/GAW], calculated by the equation (BIC-Ivanov.

Properties used flint who are in tables 1,2. For catalysts prepared according to the invention (examples 1-7), the rate constant of the oxidation reaction SO2is 2.1-2.4 cm3/GAW, higher than the rate constant of the catalyst corresponding to prototype 1.7 cm3/GAW.

Increased activity of the catalysts based on the proposed mixture at low temperature 420oC and X=30% suggests that the use of the present invention will improve the low-temperature activity and stability of catalysts. This will reduce the temperature at the entrance to the industrial contact device, will improve working conditions for subsequent layers and the total conversion of industrial sulfuric acid systems. In addition, high activity at low temperatures and ratios of SO3/SO2will reduce or prevent deactivation of the catalyst in the short-term cooling layer in a reaction medium, in case of emergency or stops for turnarounds, when the reactor is temperature reduction ratio SO3/SO2.


Claims

1. The charge for preparation of a catalyst for the oxidation of sulfur dioxide to sulfur trioxide, with the media, characterized in that as the silica-containing media it contains silica carrier, comprising the oxide of alkaline metal such as potassium or sodium, or a mixture thereof, in the amount of 0.3-20.0 wt. %. calculated on the dry product, and the content of components in the mixture of wt. %:
The vanadium pentoxide - 6,0-11,0
The potassium oxide - 7,3-20,0
Sodium oxide is 0.3 to 6.3
The sulfur trioxide - 22,0-36,5
The polyethylene oxide - 0,2-5,0
Silica carrier - Rest
2. A method of obtaining a mixture of catalyst for the oxidation of sulfur dioxide to sulfur trioxide, which consists in mixing the catalytically active substances containing vanadium pentoxide, oxides of alkali metals such as sodium and/or potassium, sulfur trioxide and polyethylene oxide, silica carrier, characterized in that as the silica-containing media using silica carrier, comprising the oxide of alkaline metal such as potassium or sodium, or a mixture thereof, in the amount of 0.3-20.0 wt. %, and the silica carrier is injected or hydrocephaly humidity 40-95 wt. % containing the oxide of potassium, or sodium, or a mixture thereof, in an amount not less than 0.3 wt. percent, or enter it in the form of a mixture of hydrocephaly with powdered silica, sod the CSOs silica is not more than 85 wt. % calculated on the dry product, and the total silica content in the media of the oxide of potassium, or sodium, or a mixture thereof is 0.3-20 wt. % calculated on the dry product.

3. The method according to p. 2, which used hydrocephaly get in the interaction of solutions of silicates of sodium and/or potassium, and solutions of acids, such as sulphuric, nitric, hydrochloric, coal or solutions of ammonium salts of these acids at the final pH of 5.5 to 9.0.

4. The method according to p. 2, which used powdered silica contains an oxide of potassium, or sodium, or a mixture of at least 0.3 wt. % has a specific surface area of 20-500 m2/g, a bulk density of not more than 0.6 g/cm3the particle size of the powder 4-100 μm.

 

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