Hexane – liquid hydrocarbon (C6H14), ingredient of petrol.
Hydrates - solid, crystal, icy features produced from natural gas and free water under specific pressure and temperature; temperature of the environment can be 10–30 oC above 0 oC during the process.
Hydrocarbons – organic compounds that contain carbon (C) and hydrogen (H).
Hydro-cracking – cracking of hydrocarbon molecules using hydrogen and a catalyst.
Hydro-desulphurisation – removal of sulphur components from petroleum products using hydrogen and a catalyst.
Hydro-processing – removal of undesired compounds (sulphur, hydrogen) from hydrocarbons using hydrogen and a catalyst.
Hydro-skimming refinery – the simplest type of refinery which has no process for refining atmospheric or vacuum residues as a component.