What is the key chemical transformation in propane dehydrogenation (PDH)?

The key chemical transformation in propane dehydrogenation (PDH) is the removal of two hydrogen atoms (H2) from a propane molecule (C3H8) to form a propylene molecule (C3H6). Propylene, also known as propene, is an unsaturated hydrocarbon containing a carbon-carbon double bond. The reaction can be represented as: C3H8 → C3H6 + H2. This reaction is endothermic, meaning it requires heat to proceed. It is also equilibrium-limited, meaning the conversion of propane to propylene is thermodynamically limited at typical reaction conditions. To overcome these limitations, the reaction is typically carried out at high temperatures (550-650°C) and low pressures, and in the presence of a catalyst. Common catalysts include platinum (Pt) supported on alumina (Al2O3) or chromium oxide (Cr2O3). The catalyst facilitates the breaking of C-H bonds in propane and the formation of the carbon-carbon double bond in propylene, while also minimizing side reactions such as cracking and coke formation. The hydrogen produced as a byproduct can be recovered and used as a fuel gas or in other chemical processes. The dehydrogenation reaction converts a saturated alkane (propane) into an unsaturated alkene (propylene), which is a valuable building block for various petrochemical products.