Platinum coated filaments of platinum and rhodium; method of preparation and use in ammonia oxidation

Claim 2

A catalytic element comprising filaments consisting essentially of platinum, rhodium, and optionally palladium said filament having a high surface area coating consisting essentially of platinum formed thereon, the surface area of said catalytic element exceeding 50cm²/g.

Claim 3

The catalytic element of claim l wherein the surface area of said catalytic element exceeds 250cm²/g.

Claim 4

The catalytic element of claim l wherein the surface area of said catalytic element exceeds 350cm²/g.

Claim 5

The catalytic element of claim l wherein the surface area of said catalytic element exceeds 500cm²/g.

Claim 6

The catalytic element of any of claims l to 4 wherein the weight of said platinum coating is at least about 0.5 grams per square meter of bulk gauze area.

Claim 7

The catalytic element of any of claims l to 4 wherein the weight of said platinum coating is at least about 3.0 grams per square meter of bulk gauze area.

Claim 8

The catalytic element of any of claims l to 4 wherein the weight of said platinum coating is at least about 4.0 grams per square meter of bulk gauze area.

Claim 9

A catalytic element according to any preceding claim, said element being for oxidation of ammonia.

Claim 12

l0. A method according to claim 9 wherein the thermally decomposable platinum compound dispersed in a volatile liquid is deposited on the mesh by spraying droplets of said liquid onto the mesh.

Claim 16

An improved method of oxidizing ammonia over a platinum containing catalytic element while recovering platinum lost from the catalytic element to the process stream on a palladium containing recovery element placed downstream of and closely adjacent to the catalyst gauze, wherein the improvement comprises using an improved platinum containing catalytic element having a high surface area coating of platinum thereupon characterized in that the ignition temperature for the ammonia of the fresh platinum containing catalytic elements is no more than the ignition temperature for ammonia of the palladium containing recovery element.

Claim 17

An improved method of oxidizing ammonia over a platinum containing catalytic element while recovering platinum lost from the catalytic element to the process stream on a palladium containing recovery element placed downstream of and closely adjacent to the catalyst gauze, wherein the improvement comprises using an improved platinum containing catalytic element having a high surface area coating of platinum thereupon characterized in that the ignition temperature for the ammonia of the fresh platinum containing catalytic elements is no more than the ignition temperature for ammonia of the palladium containing recovery element.

Claim 18

An improved method of oxidizing ammonia of the type wherein a mixture of ammonia in air is passed over a platinum containing catalytic element characterized in that the improvement comprises the catalytic element having a high surface area coating of platinum thereupon such that the ignition temperature of the catalytic element for ammonia in air under the operating conditions prevailing in said plant is not more that about 275°C at a throughput rate of 8500 lb/ft²-hr.

Claim 19

An improved method of oxidizing ammonia of the type wherein a mixture of ammonia in air is passed over a platinum containing catalytic element characterized in that the improvement comprises the catalytic element having a high surface area coating of platinum thereupon such that the ignition temperature of the catalytic element for ammonia in air under the operating conditions prevailing in said plant is not more that about 275°C at a throughput rate of 8500 lb/ft²-hr.

Claim 22

An improved process for initiating oxidation of ammonia in a plant of the type in which a mixture of ammonia in air is passed over a platinum containing catalyst and oxidized thereupon wherein the improvement comprises providing an improved catalyst gauze having a high surface area coating of platinum disposed thereupon said improved catalyst gauze being capable of oxidizing hydrogen at a temperature of less than 75°C at a throughout rate of 8500 lb/ft²-hr and heating the improved catalyst gauze from said temperature below 75°C by passing a mixture of hydrogen in air thereover and thereafter increasing the concentration of hydrogen in said mixture and thereby raising the temperature of said catalyst gauze to the temperature at which it is capable of oxidizing ammonia in air.

Claim 23

An improved process for initiating oxidation of ammonia in a plant of the type in which a mixture of ammonia in air is passed over a platinum containing catalyst and oxidized thereupon wherein the improvement comprises providing an improved catalyst gauze having a high surface area coating of platinum disposed thereupon said improved catalyst gauze being capable of oxidizing hydrogen at a temperature of less than 75°C at a throughout rate of 8500 lb/ft²-hr and heating the improved catalyst gauze from said temperature below 75°C by passing a mixture of hydrogen in air thereover and thereafter increasing the concentration of hydrogen in said mixture and thereby raising the temperature of said catalyst gauze to the temperature at which it is capable of oxidizing ammonia in air.