Hydrogenation is a chemical reaction between a compound and hydrogen. In the fine chemicals industry, hydrogenation is commonly performed in a fixed-bed catalytic reactor. An unsaturated hydrocarbon, such as an alkene or alkyne, is reduced in the presence of hydrogen to form a saturated (or more saturated) hydrocarbon. These reactions are often performed at elevated temperature and pressure to increase the density of the hydrogen and increase the rate of reaction. Reactor pressure control is critical and can be difficult due to aggressive chemicals, high temperature and pressure, and the presence of mixed phase reactants.