The pollution control example

Control of pollutants by oxidation is another exothermic process in which high conversion is the most important performance criterion. Interest in efficiency is limited to minimize byproduct formation the byproducts can be more damaging and more refractory than the original pollutants were. Commercially, most adiabatic reactors used for pollution control are of the least expensive construction. 

Complete or very high conversion requires the study of catalyst at very low concentrations. At such conditions, close to equilibrium (Boudart 1968), all reactions behave according to first order kinetics. Study at very low concentrations is also helped by the very small heat generation, so these studies can be executed in small tubular reactors, placed in simple muffle furnaces. Such studies were made by Kline et al (1996) at Lafayette College and were evaluated by Berty (1997). 

Evaluation of catalyst for oxidation of pollutants usually involves an Ignition Curve determination. This is a slightly overused expression, because only heat generation is evaluated, not heat removal. For a true ignition curve representation, heat removal evaluation would also be required. 

Reprinted with permission from Berty, 1997 American Chemical Society 

From the heat generation alone the maximum tolerable temperature difference between catalyst and gas can be evaluated, as will be shown in a later chapter. This is never done in pollution control catalyst testing. Due to the simple conditions at very low concentration, the Ignition Curve can be evaluated for first order kinetics. 

---