Gas to Liquids - The Next Generation of Base Oils

摘要

Shell was the first oil marketer to commercialize Gas to Liquids (GTL) technology for base oils production. This was occasioned by the commissioning of the Bintulu multi-purpose GTL facility in 1993, which uses the Shell Middle Distillate Synthesis process to produce detergent feedstocks, a range of Fisher-Tropsch commercial wax grades and a feedstock for base oils production. This base oils’ feedstock, a so-called waxy raffinate, requires only a de-waxing step to produce a finished base oil which is essentially an iso-paraffinic base stock. The feedstock was shipped to Shell facilities in both Japan and France from 1994 onwards where it was solvent de-waxed to produce the first commercially available GTL base oil in the market place. This was a 5 cSt grade marketed as Shell XHVI. It was used to develop passenger car motor oils meeting ILSAC GF-2 and GF-3 specifications. Shell has announced in 2003 its intention to build a two train world scale GTL facility in Qatar and this will include substantial base oils facilities producing a full grade structure from 2 cSt to > 9 cSt (Vk 100°C) base oils grades. The lower viscosity grades will fall into the current API Gp II category and grades > 4 cSt will fall within the current API Gp III classification. These grades will show the superior additive responses expected of 100% saturates catalytically de-waxed base oils. The characteristics of the base oils will make them ideally suited to a range of automotive and industrial fluid applications by virtue of the combination of both high VI and high Vk 100oC, where the upper limiting carbon number is not set by the intersection of cracking severity and limiting crude oil carbon number – as is the case in severely hydro-cracked Gp II and Gp III base oils. Data are presented which support this extension to the blending window.