LONDON — What kinds of engine oils will be made when Gas-to-Liquid base oils appear? And can anything be done to widen the use of Group I base stocks, which for 10 years have been losing market share to Group II and Group III?
Last week here, the world’s largest base oil refiner sketched a two-pronged strategy for its base stock slate which addressed both of those questions. ExxonMobil has launched a Group I base stock with a viscosity index of 105 — dubbed “Group I+” — and also unveiled details of its forthcoming “Group III+” products made from waxy feedstocks like those expected someday from GTL technology.
Despite rapid growth in the use of Group II and Group III base oils, X B Cox, global basestock strategic planner for ExxonMobil in Fairfax, Va., pointed out that Group I remains the world’s predominant quality. Over two-thirds of the world’s base stock supply is Group I, and “Group I will have a role far out into the future, and its performance will be adequate for many lubricants,” he told the 7th ICIS-LOR World Base Oils Conference on Thursday. “But it will be under constant pressure, especially as low-sulfur engine oils enter the market.”
The biggest driver of base stock quality, he noted, is engine oil needs, such as fuel economy, longer drain intervals, property retention, soot-handling capabilities (for diesels), improved low-temperature performance and emissions reductions. In the forefront of these right now are tighter emission requirements, as Europe, Japan and the United States all have aggressive timetables for slashing sulfur, particulate and NOx emissions.
Having the right product at the right time is the trick, of course, and ExxonMobil saw its opportunity at the interface between base stock groups. The challenge, Cox said, “was to make one group suitable for the higher-value applications of the next group.” This has been done by using additives, but may not always be cost competitive.
Instead, ExxonMobil developed a new solvent extracted and solvent dewaxed Group I+, manufactured in France and Italy. Trademarked as CORE 145, the product targets markets in Asia-Pacific and Europe where 10W-40 engine oils have a large market share. By carefully choosing the feedstocks and tightly controlling the fractionation, extraction and dewaxing steps, the refiner can select for specific high viscosity index molecules. CORE 145’s specifications show a V.I. of 105; NOACK volatility of 15; and pour point of -15 degrees C.
At the high end of the scale, and made only in pilot plant quantities so far, are ExxonMobil’s new Visom branded Group III+ base stocks. This product aims to meet one of Europe’s most difficult engine oil specs, 0W-30. So far, marketers have needed to formulate with polyalphaolefins to meet the stringent cold-cranking, viscosity and volatility requirements of this grade.
Visom is created through wax isomerization, and has an impressive viscosity index of 140, thanks to its high paraffin content. (The name Visom was derived from combining “viscosity index” and “isomerization,” Cox explained.) The product became possible after the ExxonMobil merger, and combines Exxon reactor hardware with Mobil catalyst technology, with engineering and research support from both. Basically, it upgrades slack wax to base stocks with high V.I., low volatility, excellent cold-cranking properties and what Cox called “superior” blending performance. Visom is primarily iso-paraffins, he pointed out, while competing Group III base stocks made from hydrocracker bottoms have significant naphthene content.
He went on to show how Visom’s blending advantages and cold-cranking performance mean that 5W-40 engine oils can be made with 100 percent Visom base stock, without resorting to PAO, and at a lower additive treat rate. He also described how 0W-30 requirements can be met with Visom alone or with PAO alone (but not with competing Group III base stocks unless some PAO is included to achieve the cold-cranking limit).
“Wax is wax, and isomerized wax is essentially the same stuff,” Cox said. “It doesn’t matter where it comes from.” Made from waxy feedstocks and using the same catalyst systems as GTL will use, Visom will provide valuable experience in formulating with GTL-type base stocks, prior to their arrival later in the decade, he said.
ExxonMobil will begin manufacturing Visom 4 and Visom 6 base stocks by mid-year at its reopened base oil refinery in Fawley, U.K., Cox told Lube Report, and commercial quantities will be available in the second half of the year. “The unit size is less than a thousand barrels a day, or roughly 40,000 tons per year,” he added.
Most important, he told the London conference, is that ExxonMobil has demonstrated that Group I stocks can be made more selectively, creating molecules that can meet lubricant needs for many years to come. “We’re not sitting on our laurels,” he said, emphasizing that GTL oils will put creative pressure on everyone in the lubricants industry, because the manufacturing and blending economics will be so different than in the past.