SU197459A1 - - Google Patents

Description

METHOD OF COLLATING NOBLE METALS, FLASHING FROM CATALYSTS

There is a known method for trapping noble metals, volatilized from catalysts containing platinum, platinum group metals or their alloys, in pathways flowing at high temperatures, for example during ammonia oxidation, using gas-permeable PI materials: devices, preferably meshes, from materials such as asbestos. fiber, glass and metal yarns. The known method is based on the filtration of particles of noble metals. In this case, the gases are cooled to a temperature of about 600 ° C.

According to the proposed method, grids of gold, palladium or their alloys with the addition of from 0.1 to 40% niobium, tantalum and thorium are used as absorbers, together either separately or with the addition of 0.1 to 8% chromium or nickel, or manganese and from 0.1 to 2% titanium or zirconium.

The capture of noble metals (platinum and metals of the platinum group or their alloys) takes place at the moment when they, evolving from catalysts containing these metals, are in vapor form. For this purpose, the scavengers are located directly behind the catalyst at a distance of no more than 10 mm, while the temperature of the scavenger is maintained for no more than

50 ° C below the temperature of the catalytic reaction.

An example. A certain amount of wire nz palladium alloy with gold (80: 20) is placed in a unit operating under a pressure of 7 MPa, at a distance of 4 mm (below) from the grid of a platinum alloy with a rhodium diameter of 1170 mm, which serves as a catalyst during the oxidation of ammonia only a large cellular net made of a flame-resistant non-precious metal alloy, as a result of which the NC wire of the palladium-gold alloy was practically at the same temperature as the catalyst, i.e., about 930 ° C. Palladium-gold alloy wire for 50 days of operation due to absorption of platinum and rodi gained 35.1% in weight as compared to its original weight.

In a parallel experiment, palladium-gold alloy wire is placed in a cooling zone at a maximum operating temperature of 800 ° C and known regeneration methods using filter cloths about 400 mm from the grid of a platinum-rhodium alloy catalyst. After 50 days of wire operation, its weight gain was only 5.1%.

platinum vapors were absorbed from the noble metals, while in the second case platinum particles had already formed, which could hardly be captured (absorbed) by individual wires, which had only a slight reflective effect.

Subject invention

The method of trapping noble metals volatilizing from catalysts containing platinum, platinum group metals or their alloys in processes proceeding at high temperatures, for example 900 ° C, in particular, in the oxidation of ammonia, using gas permeable absorbers, preferably nets, characterized by that, in order to carry out a more complete capture of metals, gold, palladium or their alloys with the addition of from 0.1 to 40% niobium, tantalum and thorium are used as absorbers, together or separately, or with iem from 0.1 to 8% chromium or nickel, or manganese, and 0.1 to 2% of titanium or zirconium, and said absorption grid is disposed in close proximity to a catalyst, preferably at a distance of about 10 mm.