In order to obtain a sufficient high conversion rate in flue gas cleaning processes, catalysts are used in nearly all cases. The activation of these classical contacts is done by heat. On the other side it is known that semiconductor material can become catalytically active under irradiation with UV-light to accelerate combustion processes. Since in that case the oxidation process proceeds at room temperature, the use of a photocatalyst can yield some advantages in comparison to the application of thermal activated catalysts, especially, for small combustion units. The problem, however, is that no useful information about the kinetics of photocatalytic combustion processes or about the possibilities of the practical use of photocatalysts exists in the open literature. Using the combustion of propene as example, these problems are discussed in detail. Some practically useful solutions to the main problems are proposed.