One of the most unique blending components available to lubricant formulators is bright stock. This heavyweight material is generally produced in an API Group I refinery where solvent extraction and solvent dewaxing processes are available.

At room temperature, bright stock would pour like honey. It has a kinematic viscosity at 100 degrees C of approximately 32 centiStoke and is commonly referred to as a 2500 SUS base stock (i.e. SUS at 100 degrees F). For comparison, a heavy 600 SUS base stock is only about 12 cSt at 100 C.

The feedstock for bright stock is typically sourced off the bottoms of the vacuum distillation unit where normal gas oil or vacuum gas oil fractions are produced. These vacuum tower bottoms are referred to as vacuum residuum and usually contain very heavy asphaltene materials that need to be removed before further processing can occur; that step typically occurs in a separate processing unit called a propane de-asphalter. The de-asphalted oil can then be processed through the same solvent extraction and solvent dewaxing steps as regular Group I base stocks.

Globally there are around 105 Group I refineries, with capacity totalling approximately 485,000 barrels per day. Of these, roughly 75 produce bright stock and/or heavy base stocks with kinematic viscosities that are significantly higher than 650N.

IHS Inc., a global research and consulting firm, reports that current bright stock capacity is approximately 92,000 b/d worldwide (or 4.5 million metric tons/year). This is down 9 percent from 2010, when capacity was 101,000 b/d. On the other hand, IHS puts current bright stock demand at 80,000 b/d, only slightly below 2010s level of 83,000 b/d.

With the continuing shift to the use of more highly refined and lower viscosity base stocks in automotive applications, traditional solvent-processed Group I base stocks have been consistently replaced with hydropro­cessed Group II and Group III. The role of bright stock in automotive engine oil applications has been eroded significantly, too.

The base oil industry is now in an oversupply situation because of ongoing investments in new hydroprocessing facilities without an offsetting rationalization of older Group I plants in many regions of the world. North America has successfully made this transition; however, regions like Europe now are feeling the impact of Group I shutdowns. Recent announcements included Group I units at Shell in Pernis, Netherlands, Colas in Dunkerque, France, and Total in Gonfreville, France. These three closures will reduce Group I capacity in Western Europe by slightly over 17 percent, and will cut regional bright stock availability by 20 percent.

Figure 1 shows a profile of global bright stock supply and demand as provided by IHS. It is apparent that the reduced bright stock production associated with Group I plants that are scheduled to close over the next one or two years, combined with the additional Group I plants that are likely to close due to the pressures of oversupply and poor margins, have the potential to reduce global bright stock capacity by as much as 40 percent, or 1.8 million t/y by 2020.

Conversely, demand for bright stock will remain constant, as declining automotive uses are offset by increasing industrial use. This will create a supply deficit in the global bright stock market of approximately 800,000 t/y by 2020.

As the supply of bright stock shrinks, one would first anticipate an impact of market pricing. This is happening, as observed when comparing the posted price of bright stock against the price of lower-viscosity Group I base stocks that are in oversupply. In fact, over the past 12 months bright stock prices maintained 70 percent to 84 percent of their February 2014 value – whereas grades like 150N and 650N have only retained 60 percent to 65 percent of their February 2014 value. This confirms the high value placed on bright stock, and its more balanced supply-demand position.

Regardless, if supply declines and if demand holds steady, bright stock prices should begin to increase and further separate themselves from other Group I. In fact bright, stock pricing is already at par with Group III pricing in many regions of the world.

Given the projected deficit in bright stock availability, the first task should be to look for alternative blending stocks. These have been suggested in the past and include higher-cost options like polyisobutylene, polyalphaolefin, polyalkylene glycol and alkylated naphthalenes, to mention a few. However, before seeking alternatives we should look at where bright stock goes, and assess what adjustments and efficiencies can be made in its current utilization.

Today, the primary use of bright stock on a global basis is in the formulation of gear oils (Figure 2). Automotive engine oil applications represent the next-largest segment, but this area has been in a long decline with the conversion of both passenger car motor oils and heavy-duty diesel oils from monogrades to multigrades. This transition is nearly complete in North America; however, other regions like the Middle East still have substantial demand for monograde engine oils due to their hot climate and high level of competition in the markets lower tiers.

Minimum performance standards for PCMO and HDDO are under discussion in the Middle East, and when implemented will lessen the need for bright stock in this region. To put it in a wider perspective, approximately 20 percent of global bright stock is used in automotive engine oils. Eliminating, or at least limiting this use of bright stock would free up approximately 700,000 to 800,000 tons of supply. This matches the deficit projected in supply by 2020, and it suggests that a balanced position is possible without seeking bright stock alternatives.

Another efficient use of bright stock is industrial lubricants that require heavy ISO viscosity grades. Bright stock equates roughly to an ISO 460 grade, whereas 650N is closer to an ISO 100. Hence with judicious blending, bright stock allows one to bridge the ISO viscosity range between these two bench points, including ISO 150, ISO 220 and ISO 320.

However, bright stock sometimes is used as a blending stock where it is not required. This is particularly true with companies that produce bright stock and also have their own finished lubricants business. In such instances, company formulators must have several options for blending their industrial products; this allows them to utilize all of their refinerys production effectively and to be flexible when different viscosity grades are either short or in oversupply.

An example is shown in Figure 3, where an ISO 68 industrial oil is formulated using several base stock combinations consistent with what a refinery would produce. Bright stock can be used with some of these combinations, and companies will sometimes favor this when it lowers their formulation costs or when bright stock supply is long. Although this makes good sense for the internal management of bright stock, better utilization of this valuable blend stock, based on sound raw material management principles, could ease overall demand.

Also, rationalization of Group I plants is not simply a dead-end street. In fact, some companies are actually utilizing the transition from Group I to Group II production as a means to not only preserve bright stock output but also to increase supply to the marketplace. An example is Luberef in Saudi Arabia, with its upcoming introduction of Group II production at its Yanbu refinery.

Under normal circumstances, the conversion from Group I to Group II would mean that the Group I plant would discontinue operations. At Yanbu however, Luberef will debottleneck the Group I plant and use it to produce only bright stock. With a gain in bright stock production of approximately 110 percent, Yanbu will provide additional barrels to a region that is still highly dependent on bright stock, for monograde automotive and marine oil applications, for example.

Over the next several years, change is expected within the Group I segment and many discussions are focused on the drivers for rationalization. However, some companies will look at their Group I facilities as an opportunity to convert to Group II, in much the same way that ExxonMobil converted its Baytown, Texas, refinery in 1999. The introduction of the proprietary Raffinate Hydro­conversion process demonstrated that an existing Group I solvent processing facility could be effectively transformed into a flexible facility – capable of producing Group I, Group II and Group II+ quality base stocks, along with solvent-refined bright stock. There may be other opportunities where Group I rationalization comes as part of a Group II upgrade, while maintaining bright stock production.

If proper management occurs along with the gradual decline of monograde engine oils, the projected bright stock deficit should be manageable. Regardless, there remain several options to substitute for bright stock, depending on individual product needs and market opportunities.

One option available today is to combine viscosity modifiers or thickeners with a lower-viscosity base stock, to simulate the viscometric properties of bright stock. In an automotive gear oil, for example, thickeners can be used with a heavy 650N Group I base stock or corresponding 600N Group II to formulate an SAE 80W-90 product, the major viscosity grade. The substitution will maintain performance and be achievable at a similar cost to the bright stock alternative.

Some industrial oils require only viscosity as a performance characteristic. In these instances, naphthenic bright stocks can be a cost-effective alternative. Despite their lower viscosity index, naphthenics have been shown to provide equivalent solubility characteristics when blended with either a Group II or Group III base stock. This is an important feature to remember.

Polyisobutylene is another option that has been used in recent times. PIBs represent the backbone for many fuel and lubricant dispersants and are used in small-engine applications to provide clean burn, low smoke and good lubricity. They also have good V.I. characteristics, although solvency is compromised relative to bright stock. PIBs have been commercially marketed as a bright stock alternative when blended with a Group II 600N; this tactic was used by some companies during the short supply period in 2011 when almost every type of base stock was affected.

Availability of PIB for this use may be limited, and economics would also have to be considered, as this heavy Group II/PIB blend may be a higher-cost option. Never­theless, there could be opportunity to position this as a premium product with demonstrably better performance and hence value differentiation.

High-viscosity synthetics, including polyalphaolefins, polyalkylene glycols and alkylated naphthalenes, offer unique performance features that will elevate the performance of a heavy industrial oil previously formulated with bright stock. These synthetics can provide improved thermal and oxidative stability, energy efficiency, longer life and wider operating range, and their benefits should be incorporated into the value of the end product.

It is important to understand the value of bright stock when assessing each of its end-use applications. Bright stock has long been a cost-effective and versatile tool for formulators. It offers excellent solvency and its polarity helps to disperse soap thickeners into oils for grease manufacture. Demand is not expected to change significantly over the next five years as tapering use in the automotive arena is offset by growth in the industrial and gear oil areas.

With the decline in Group I production, one could project a potential short supply and doom and gloom scenario for products that presently use bright stock. However, by focusing on using bright stock in those applications where there is a must versus want need, the future decline in availability can be managed. When shortages exist, there are cost-effective options – plus the opportunity to elevate performance and offer premium products.

When performance cannot be justified or value achieved in the marketplace, it may be wise to review your product and formulation strategy and exit those areas where a suitable return cannot be achieved. The use of bright stock in low-cost and low-margin products may not stand up to this scrutiny.

In the end, the forecast for bright stock should be promising as there are many applications where its value and performance benefits can be captured. Shortages can be managed through proper base stock and formulation choices, leaving the opportunity to match the various alternatives to those applications that deliver the strongest value and performance.

H. Ernest Henderson, Ph.D., is president of K&E Petroleum Consulting LLC and an international expert and instructor in base stocks, from solvent-refined Group I through Group IV, GTL and rerefined. Kathleen Henderson is the firms chief financial officer, and holds multiple degrees including education. Along with industry knowledge, KEPC also provides customized training in base stock manufacturing, application and value to supply chain. Phone: (405) 242-3215. E-mail: kepetroleumconsult@yahoo.com