The present invention relates to an integrated membrane/absorbent/adsorbent process and system for removal of mercury and sulfur compounds from natural gas on a ship that houses natural gas purification equipment. First mercury and most of the sulfur compounds are removed by an adsorbent bed and then the natural gas stream passes through a membrane unit to produce a partially purified natural gas residue stream to be dried and then liquefied and a carbon dioxide permeate stream that can be used as a fuel gas.