SU325761A1 - METHOD FOR PREPARATION OF CATALYST FOR AMMONIA OXIDATION - Google Patents

Description

The invention relates to methods for the preparation of catalysts for the oxidation of ammonia, used, for example, in the production of nitric acid.

A known method of preparing a catalyst for the oxidation of ammonia is by calcining a mixture of iron and chromium salts, followed by grinding and tableting.

In order to obtain a highly active catalyst for the oxidation of ammonia, the described method is carried out by heating a mixture of iron and chromium nitrates, taken in a ratio from 10: 1 to 24: 1, to 210-315 ° C while stirring and grinding, keeping at this temperature to complete removal of nitrogen oxides, followed by tableting with the addition of graphite and calcining the molded catalyst mass at 560-650 ° C.

Manganese and / or zinc and / or potassium and / or calcium nitrates can be added to the mixture of nitrates of iron and chromium in an amount up to I weight. %

The catalyst prepared under these conditions has the necessary porosity and specific surface area, which ensures its high catalytic activity and mechanical strength during oxidation of residual ammonia contained in nitrous gases.

Example. 150 / cg of ferric nitrate, 11.2 kg of chromium nitrate and 0.8 kg of nitrate salts of manganese, zinc, potassium and calcium (each 0.2 kg) of reactive purity are loaded into the reactor, which is an electrically heated ball mill. Inside the reactor are stainless steel bowls with a diameter of 70 mm. After loading the reactor, the charging port is shut in and the reactor

driven into rotational motion.

As the reactor and the salts loaded into it are heated, evaporation of water vapor, acid, and removal of nitrogen oxides occurs, which are sucked out by the exhauster through traps, refrigerators and separators. The vacuum created by the exhauster is 2-15 mm of water column. In refrigerators, the vapor-gas mixture released in the reactor is condensed to form nitric acid, which is fed to an acid collector.

As the crystallization water evaporates, the solution in the reactor begins to thicken, the temperature rises to 170 ° C (

thermocouples) and the second stage of decomposition of anhydrous nitrate salts occurs. The mass to be dried in the reactor is crushed by balls to a powder. After 3 hours of soaking at 250 ° C, the reactor and powder are cooled off and the latter is fed for mixing with graphite. Mixing is performed in a drum mixer, after which the thoroughly mixed powder is fed to tableting.

The pre-packaged semi-finished product is sifted on a vibrating screen, after which it is fed to the calcination. The calcination of the catalyst is carried out in muffle furnaces at 600 ° C, then it is sieved on a vibrating screen and fed to the packaging.

The resulting catalyst contains Fe2Oz in the form of (a-Fe2Oz) 92%, CO2 6.9%, moisture not more than 0.3%, crushing force on the base of the tablet - 5 kg, bulk density - 1.6-1.85, loss at calcining to 0.5%.

Used as the second stage of a two-stage ammonia conversion catalyst, the prepared catalyst provides a high degree of ammonia conversion (97%).

Subject invention

Claims (2)

1. A method of preparing a catalyst for the oxidation of ammonia by heating a mixture of iron and chromium salts followed by grinding and tableting, characterized in that, in order to obtain a highly active catalyst, their nitrates taken from iron and chromium are used in an RH ratio of 10 : 1 to 24: 1, heating the mixture of salts is carried out up to 210-315 ° C with simultaneous stirring and grinding, followed by aging at this temperature until complete removal of nitrogen oxides and calcination of the molded catalyst is carried out at 560-650 ° C. 2. A method according to claim 1, characterized in that manganese and / or zinc and / or potassium and / or nitrates are introduced into the mixture of iron and chromium salts. calcium in an amount up to I weight. %