Butane fraction or C4 Raffinate II is a mixture of C4 hydrocarbon compounds, which is classified as a liquefied gas group. These gases are liquid under a certain pressure and temperature (e.g., in production conditions in the MTBE unit), they turn into steam at the normal environment temperature and pressure. These gases are heavier than air and their vapors are combustible. This substance is a combination of four carbon gases including butene (cis, trans 2-butene, and 1-butene) and butane (isobutane and normal butane). It is used in the production of olefinic units besides the raw materials. It is also used in the production of MEK and as fuel. The ignition temperature is -80°C to -60°C (according to DIN 51755 standard). The ignition temperature is 324°C to 465°C (according to DIN 51755). Density at 25°C is 580 kg/m3, and vapor pressure is 1.918 bar at 20°C