Space Time and Velocity

The extent of contact between the reactant(s) and the catalyst is often believed to be very important in the reactor performance but is difficult to determine. This problem is complicated by several factors. In gas/vapor reactions, the volumetric flow rate may change as the reaction proceeds. Furthermore, the true void volume of the catalyst bed or membrane pores (and therefore, the void fraction of the reactor) is not easy to measure. 

Space time and space velocity. In practice, a superficial contact time called space time is generally used. Its reciprocal is the space velocity. 

The space time can be defined in two ways. It is often calculated as 

The side reactions continue even as the main reaction slows down as the equilibrium is approached. 

Effects of space time under nonisothermal conditions. The above discussions around the effects of space time on a membrane reactor performance are limited to isothermal conditions. The behavior of the reaction conversion in response to space time can be further complicated under nonisothermal conditions. 

---