Propane is one of a group of liquefied petroleum gases (LP gases). It is generally transported as a liquefied compressed gas. Before transport, natural gas is liquefied by pressurization. In addition, exports of liquefied natural gas increased. Qatar is the leading exporter of liquefied natural gas. An LNG carrier is a tank ship designed for transporting liquefied natural gas (LNG). Qatar is a global leader in liquefied natural gas production. Many taxi companies run their fleets on liquefied natural gas. It is industrially produced by cryogenic fractional distillation of liquefied air. Hydrogen densities similar to liquefied hydrogen can be achieved with appropriate adsorbent materials. Natural gas is usually liquefied to LNG at the end of the pipeline, before shipping. CNOOC has become China's dominant producer of liquefied natural gas. To achieve a dense state, gases can be liquefied at low temperatures or compressed. Kennedy mounted a national effort against the construction of liquefied natural gas facilities. Thus, above the critical temperature a gas cannot be liquefied by pressure.