As Revenue (Engl. Conversion) refers to the percentage of the starting material - so-called substrates - that is converted or "converted" into products. In chemical process engineering, conversion is a crucial parameter because it reflects the efficiency of a process.

The conversion is strongly temperature-dependent and generally increases with increasing temperature. An example of an almost complete conversion, as is aimed for in industry, is the combustion of volatile organic compounds (VOCs) at temperatures above 750 °C. In practice, however, a complete conversion is often not possible because the activation energy of many chemical reactions is too high. In addition, the increase in temperature leads on the one hand to increased energy consumption and on the other hand to an increased formation of undesirable by-products, which increases the selectivity sinks.

To achieve this goal, approximately 70–80% of all industrial processes Catalysts Catalysts reduce the activation energy, increase selectivity and enable chemical reactions to be carried out under milder conditions. This not only increases energy efficiency thanks to lower process temperatures, but also reduces the formation of undesirable by-products.