What is required for a catalytic removal system to function effectively?

For a catalytic removal system to function effectively, the injection of ammonia in the presence of a catalyst is essential. This process is commonly associated with catalytic reduction systems, particularly in applications like selective catalytic reduction (SCR), which is used for reducing nitrogen oxides (NOx) emissions in exhaust gases.

In this system, ammonia acts as a reducing agent. When it is introduced into the exhaust stream, it reacts with the nitrogen oxides over the catalyst to form harmless nitrogen and water vapor. The catalyst facilitates this reaction, lowering the activation energy required and allowing it to occur at lower temperatures. Efficient operation requires the correct amount of ammonia and a suitable catalyst material, such as vanadium oxide, titanium dioxide, or zeolites, which enhance the reaction rate and reduce the amount of unreacted ammonia that might otherwise escape into the environment.

The other options do not directly relate to the functioning of a catalytic removal system as efficiently or are less relevant in this context. For optimal operation of catalytic removal processes, the proper conditions including the presence of a reducing agent like ammonia are crucial, emphasizing why this option is the key to effective system functioning.