Space Velocity and Converter Size

The catalytic converter monolith volume is typically 0.5 to 1 times of the engine swept volume.  Space velocity characterizes the residence time available to gases to undergo chemical reactions in the reactor bed. The space velocity is inversely proportional to the residence time and is defied as,

(5.2)

In the catalytic converters for SI engines, the space velocity typically reaches up to 50 s-1. Higher the space velocity that can be used to achieve required conversion rates, smaller is the volume of the converter required.  Higher usable space velocities have been achieved through improvements in the design of substrate, wash coat and catalyst dispersion technologies.