SU1759446A1 - Catalyst for oxidizing ammonia to nitrogen oxide - Google Patents

Abstract

The essence of the invention is the product - KI composition,% yttria oxide 21-27, beryllium oxide 5-8, barium peroxide 8-11, copper oxide (I) 27-33, copper oxide (It); the rest QD is obtained by mixing the indicated oxides in ethyl alcohol, molded and tempered, raising the temperature at a rate of 300 ° C / h, kept at this temperature, cooled at a rate of 50-70 ° C / h to 300 ° C and then to room temperature. Characteristic: increased selectivity and heat resistance. 1 tab

Description

This invention relates to non-platinum ammonia oxidation catalysts in the production of nitric acid.

A number of non-platinum catalysts for the oxidation of ammonia to nitrogen (II) are known. The most selective of non-platinum catalysts contain SoSoz as a main component. For example, a catalyst is known that contains SoSO / i and oxides Nl, Fe, Sr. The yield of nitric oxide (II) on it reaches 96-98% at 750-810 ° C. However, such a high yield of nitric oxide (II) is ensured only with a low catalyst productivity of 20–25 kg mH3 / g cat day, which makes the whole process unproductive 1.

Higher performance up to 30 kg / MNZ / g cat-day has a catalyst containing CosSm and modifying additive REE oxide or a mixture of them in an amount of 5-15 wt.%. The output of nitric oxide (11) 86-95% at 800 ° C, but with an increase in the productivity of the process of raw materials (NHa)

up to 35 kg, the degree of oxidation drops to 80%, and this catalyst is effective only at low loads 2.

A catalyst for the oxidation of ammonia based on iron (III) oxide with the addition of barium zirconate 0.1-1% by weight of magnesium oxide, zinc oxide or nickel oxide, 3.5-6.5% by weight, has been developed. The output of nitric oxide is about 96-97%. The catalyst is distinguished by the relative availability and cheapness of the starting components.

The disadvantages of the catalyst are low selectivity and, in connection with this, increased consumption of ammonia-air and mixtures, as well as losses due to high volatility of nickel oxide. Therefore, this catalyst has not found practical application 3.

The closest to the proposed is a catalyst containing iron oxide (78-88%) with the addition of chromo oxide 70% and beryllium oxide 5-15%. 4 The catalyst works stably only when

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at a temperature of 750 ° C and a contact time of g- -0.55410 2, the yield of nitric oxide on this catalyst is 96-97%. The main disadvantage of this catalyst is a sharp decrease in its activity with increasing process temperature, which leads to a decrease in the yield N0 (II) with a deviation from the temperature of 750 ° C, i.e. extremely narrow temperature range of its stable operation. The specified temperature is technologically difficult to control and maintain. So, for example, the deviation of temperature to 800-850 ° C leads to a decrease in yield) MO (P) to 90%, and an increase in temperature to 900-950 ° C leads to a decrease in output ° 10 (II) to 85%.

The purpose of the invention is to increase the selectivity and heat resistance of the catalyst.

The goal is achieved by the fact that the catalyst for the oxidation of ammonia to nitric oxide (11) contains copper (I) oxide, copper (II) oxide, yttria, beryllium oxide and barium peroxide at the following content, wt.%:

Yttri Oxide 21-27

Beryllium Oxide 5-8

Barium peroxide 8-11

Copper oxide (I) 27-33

Copper (II) Oxide Else

and is a solid solution of the said oxides.

Distinctive features of the proposed catalyst are the content as a variable-valence metal oxide of copper (I) oxide and copper (II) oxide, as an oxide of a modifying lactic oxide lithium oxide, and an additional content of barium peroxide at the specified content of components, and more which is a solid solution.

The presence of yttria oxide provides the heat resistance of the catalyst as a result of the formation of a solid solution with the main component (copper oxide). By reducing the mass of yttria oxide in the catalyst below 21 wt.%, The thermal stability of the catalyst decreases sharply, and an increase in the content of U-O3 over 27% will be accompanied by the transfer of solid solution into a saturated solid solution and the precipitation of U-O 3 in a separate phase that does not have sufficient catalytic activity.

The addition of barium peroxide in the proposed ratio is due to the fact that barium peroxide, when forming a solid solution, is an additional source of activated oxygen, which has an oxidizing ability

Reducing the mass of BaO2 less than 8% leads to a drop in the yield of the target product - nitric oxide (II).

An increase in the Ba02 content of more than 11% is impractical, since it can lead to a decrease in the selectivity of the catalyst.

Beryllium oxide, having a high characteristic temperature of 1553 K. 0 performs the functions of a promoter as a result of an increase in the active centers. The use of BeO leads to an increase in the yield of nitric oxide (II).

Reducing the amount of BeO less than 5% 5 leads to a decrease in catalyst productivity.

Increasing the amount of BeO by more than 8% is impractical due to the limited solubility of beryllium oxide and precipitation into the form of the free phase.

The use of copper oxides Cu (I) and Cu (II) is due to the following factors:

the ability of these oxides to form solid solutions;

5 minimum band gap:

Cu (1.4 eV), Cu 20 (1.9 eV):

the ability of copper oxide at thermal dissociation to emit atomic oxygen 2 CuO-Cu20-0; The ability of copper to disproportionate C - C + + C.

To increase the selectivity of the catalyst, a mixture of copper oxides CuO and Cu20 is used, since Cu (I) is a diamagnetic atom and Cu (II) is in a paramagnetic state.

A decrease in the content of a mixture of CuO and CU20 of less than 54% leads to a disruption in the structure of the catalyst, which has a peroxide structure that is deficient in oxygen. A change in the structure causes a drop in the catalytic activity and a decrease in the yield of nitric oxide (II).

An increase in the content of the mixture of Cu v 5 CuaO by more than 66% is also unacceptable because of the possibility of precipitation of these components in the form of a free phase, which does not possess sufficiently high catalytic activity.

The invention is illustrated in trace / ush by examples.

Example 1. To the mixture of the initial components, in the ratio indicated in the table (Y203, BeO, BaO2, CuO, Cu20). 250 ml of ethyl alcohol are added. After thorough mixing for 60 minutes, the paste is passed through a spinneret of aaamegrome 3-5 mm, then immersed in alounds / o i, the set is placed in the oven. Raise / - .nn

RETUR at a speed of 300nC / lJ DC PFO g,;

At this temperature, solid phase synthesis is carried out for 5 hours. Then the product is cooled in a furnace at a rate of 50-70 ° C / h to 300 ° C, after which the alundum tank with the product is removed from the furnace and cooled to room temperature. After that, the obtained product is subjected to high-temperature annealing at 900 ° C in an oxygen atmosphere for 1 hour. The catalyst thus prepared is a solid solution containing 21% E203; Yu% BaCte; 8% BeO; 30.5% CuO; 30.5% Si20. The yield of nitric oxide (II) at a linear velocity of 2.2 m / s is 92.5%. The prepared catalyst in the form of granules with a size of 2-3 mm is loaded into a quartz contact apparatus and tested for catalytic activity.

The remaining catalyst compositions are prepared in a similar manner.

The test results are presented in the table.

Thus, as can be seen from the above results, the catalyst according to the invention

five

0

five

in comparison with the catalyst, according to the pro- gram, it has advantages in the output of nitric oxide (P) at elevated temperatures.

Claims (1)

Claims of the Invention A catalyst for the oxidation of ammonia to nitric oxide (), containing a variable metal oxide, a beryllium oxide and a modifying metaplate oxide, is in that. In order to increase the selectivity and heat resistance, as a variable-valence metal oxide, the catalyst contains copper oxide (} and copper oxide (li), as the modifying metal oxide is yttria oxide and additionally barium peroxide with the following content of components, wt.% Yttria oxide 21- 27 Beryllium Oxide 5-8: Barium peroxide 8-11 Copper oxide (I) 27-33 Copper Oxide (I) Else wherein the catalyst is a solid solution of said oxides. The dependence of the technological parameters of the catalyst on its composition one 2 3 4 5 6 7 8 9 10 11 Table continuation