Base Stocks

Is Bright Stock Irreplaceable?


Is Bright Stock Irreplaceable?

The price for bright stock increased dramatically in early 2021, incentivizing lubricant formulators to seek immediate alternatives and consider those longer-term options that have been on the shelf—or in the back of the mind—over the past decade. But what viable options are there to replace this mercurial fluid?

A Fluctuating Market

The gradual decline of API Group I base stock production has been well documented in Lubes’n’Greases over the years. The changes to marine fuel specifications because of IMO 2020 followed by plummeting fuel demand due to COVID-19 lockdowns has accelerated the trend of Group I plant closures in Europe and placed some others on significantly reduced run rates. However, according to Lubes’n’Greases base oil editor Gabriela Wheeler, demand and supply remained roughly balanced in 2020. (Check out Gabriela’s monthly column, Base Oil Report: Pricing, on Page 8.) 

Then a perfect storm hit. “In the first quarter of 2021, unplanned production outages, mainly due to Winter Storm Uri in February, extended turnarounds, reduced refinery runs and healthy demand in the U.S. led to extremely tight conditions for all Group I base stocks,” Wheeler said.

The effects were felt globally. In the U.S., “producers’ bright stock posted prices steadily rose from a range of 5.54 to 5.96 cents per gallon on February 10, 2021, to historic highs of 7.49 to 7.76 cents per gallon on September 8, 2021,” Wheeler said. Meanwhile in Europe, Ray Masson, director of London-based Pumacrown Ltd., reported that the price for BS150 rose from around U.S. $700 per metric ton in early 2020 to $2,250 in mid-2021.

Prices have since fallen but are still about double those of February 2020. However, behind that headline price, the premium of bright stock over heavy neutral grades has also remained high, said Gerard Heaton of Elementalle Ltd., a United Kingdom-based consultancy. The resulting headaches for many lubricant blenders are now plentiful: Do they pass on the costs to customers? Or if they decide to reformulate, which of the myriad “bright stock replacements” do they consider?

Still Plenty Out There

Mark Twain’s oft-misquoted statement “the report of my death was an exaggeration” captures the essence of the situation with respect to bright stock. While Group I and bright stock availability has been declining for decades, demand has fallen roughly in parallel. “All my 30-year lubricants career I’ve worked in an industry focused on delivering ‘more from less’ through higher quality to achieve consumption efficiency,” Heaton told Lubes’n’Greases. “This is manifested by longer oil drain intervals, smaller sumps, fill-for-life and other initiatives, for example. The move toward lower overall viscosities has depressed demand significantly.”

Despite a declining market, some of the major players have invested in their existing assets to grow into the gaps left in the market. Ergon in 2016 and Luberef in 2018 both expanded their bright stock capabilities. 

“When Luberef invested in Group II capacity at Yanbu, the existing relatively young Group I plant provided an ideal opportunity to upgrade the incremental volume of heavy ends associated with the expanded Group II base oil plant,” Heaton said. “Several existing units were redeployed or upgraded to expand bright stock production at relatively low capital cost.” 

For those lube blenders who make the decision to move away from bright stock in their formulations, the dominant technical question is, “Why have we been using bright stock up to now?” High viscosity is particularly important, but the other factor most mentioned about bright stock is its polarity or, consequently, its solvency.

“When Luberef invested in Group II capacity at Yanbu, the existing rel­atively young Group I plant provided an ideal opportunity to upgrade the incremental volume of heavy ends associated with the expanded Group II base oil plant.”

— Gerard Heaton, Elementalle Ltd.

Sometimes it can seem like every high-viscosity fluid has been promoted as a bright stock replacement. Some are base oils, while others are intended to be used at lower treat rates as an additive. The seasoned campaigners have been written about many times. These include low-molecular-weight polybutenes and high-viscosity esters, but there are many more options.

New Base Oils?

Just before the pandemic took hold of the world, both Shell and ExxonMobil made presentations of new heavy base oils that could be potential bright stock replacements. While Shell’s offering was an R&D product at the business case development phase, ExxonMobil had embarked on their expansion in Singapore, due in 2023, according to the company’s website. This would bring a heavy API Group II to market. A spokesperson for ExxonMobil told Lubes’n’Greases that the company is committed to completing the Singapore expansion project, which will help meet growing demand for high-performance lubricants and cleaner fuels.

High-viscosity naphthenic base oils are also an alternative. Thomas Norrby, senior specialist technical manager for lubricants at Swedish specialty oils manufacturer Nynas told Lubes’n’Greases, “Our offering is viscosity, solvency and availability.”  

As naphthenic base oils are derived from specific crudes in refineries that produce no or little fuel, Nynas always has availability of product. “The crudes we refine are dual-purpose bitumen and naphthenic. For this reason, Nynas was not dramatically impacted by effects of the transportation fuel crisis caused by the pandemic,” Norrby said. 

In the longer term, this configuration gives naphthenics another significant positive. “As long as bitumen is required for roads and roofs, it is possible to produce naphthenic bright stock,” Norrby said. “We have excellent security of supply around multiple crudes and a stable demand for our products.” 

Naphthenic base stocks have a low viscosity index, so they are not a true drop-in for bright stock. Because of this, Nynas has been building a body of work supporting blends of naphthenics with API Group II or Group III base oils, including rerefined base oils, and other high-viscosity base oils and viscosity index improvers. These allow the customer to find fluids with similar solvency to the traditional bright stocks, as well as similar viscometrics. 

“V.I. isn’t a big issue for most of our customers, who are replacing bright stock in industrial applications,” said Gaia Franzolin, marketing director for Nynas. “As the temperature range of operations is narrower than crankcase lubricants, we can match viscosity across that performance window. We have seen a lot of customers moving to our naphthenic Group II blends and increasing the use of some of our high-viscosity naphthenic grades. We think this was customers taking a longer-term view on bright stock decline, mainly in Europe.”   

Another perceived weakness of naphthenics is their susceptibility to oxidation. However, “naphthenics in blends have excellent antioxidant response,” Norrby said. “Indeed, we have just concluded a successful study of thermal and oxidative stability of naphthenic blends and will publish a paper shortly.”

Just Add Additives

Recently, several high-viscosity ingredients have come to market or been promoted that could replace bright stock at treat rates closer to those of additives. Croda, for example, brought a complex ester called Priolube 3997 to market a few years ago. The ester is marketed as a bright stock alternative. Other new products promoted as bright stock alternatives are in the bio-sourced and biodegradable field, including Biosynthetic Technologies’ estolides and Green Frix’s plasma cross-linked vegetable oils. (Read more about these products in “Sustainability Strikes Again” in the May 2021 issue and “Food-grade Formulators Draw from a More Colorful Palette” in the July 2021 issue.)  

“We have two commercially available products with similar viscometrics to bright stock,” Green Frix’s Frederic Danneaux told Lubes’n’Greases. “Due to their higher V.I., they are not identical to bright stock, but formulators can choose to match viscosities at the relevant temperature.” 

The Belgian startup’s co-founder and technology and development manager continued, “There is a broad range of possibilities using sustainable feedstocks” as the raw material source. Relative to current vegetable-derived fluids, Green Frix’s products have a carbon distribution closer to that of bright stock. They also present better oxidation stability than the vegetable oils from which they are derived without compromising “the excellent lubricity and biodegradability of the vegetable oils,” Danneaux said. 

Nuspec Oil, based in York, U.K., produces high-viscosity materials using ultrasonic technology deployed on the vegetable oil itself, with no prior processing to separate glycerol from fatty acids or fatty acids from one another. One of the co-founders, Boris Zhmud, has a long resume of senior positions at various lubricants and base oils companies. “To the best of my knowledge, Nuspec BS32IBD is the only product that can be used at similar treat rates to paraffinic bright stock in finished product formulations, eliminating the need for further reformulation and re-approvals,” he told Lubes’n’Greases

Nuspec Oil announced in September that they could reach commercial production of 3,000-5,000 tons per year within six months and scale production to 150,000 t/y in the next five to 10 years. They have made samples available of three possible grades of bright stock alternative.

Rather than be daunted by the absence of a trusted formulating component, lubricant formulators who wish to migrate away from bright stock are likely to be overwhelmed by the options. With established base oils and additives options, there is already scope for a significant paper exercise to define preferred alternatives. But the newer entries to the market offer bio-sourcing or biodegradability—or both—which could aid marketing claims around environmental friendliness. 

However, for those who wish to stay with their trusted component, Heaton offered some reassurance. “While Group I plant closures will continue, I’m confident that many companies with bright stock assets will sweat them hard,” he said. “So if there is demand at an economic price, bright stock will be available.”  

Trevor Gauntlett has more than 25 years’ experience in blue chip chemicals and oil companies, including 18 years as the technical expert on Shell’s Lubricants Additives procurement team. He can be contacted at