The chemical industry focuses on the conversion of raw materials into products for other industries and consumers. For chemical engineers and chemist, understanding the various processes involved in the chemical industry is an essential part of their training. This course aims to bring that understanding by giving a detailed description of the most important conversion processes. From the wealth of chemical processes, a selection had to be made. Knowledge of key processes is essential for the understanding of the culture of the chemical engineering discipline. The first chapters deal with processes related to the conversion of fossil fuels. Examples are the major processes in an oil refinery, the production of light alkenes, and the production of base chemicals from synthesis gas. Analogously to the oil refinery, the {future) CO2 and bio-based refineries are discussed. Biomass conversion processes nicely show the benefit of having insight into the chemistry, being so different from that for processes based on the conversion of the conventional feedstocks. On the other hand, the use of CO2 as raw material using clean energy will highlight the potential of the circular carbon economy.