Esters used in lubricants are classed as API Group V base oils. Biobased esters can contain between 70 and 100 percent renewable elements. While many synthetic esters are produced by combining carboxylic acids and alcohols, which are typically based on petroleum, according to Jens Kubitschke of Oxea, all esters are biodegradable.

Producers of modern synthetic esters tout the performance of such products, highlighting characteristics such as oxidation stability, low volatility, high temperature stability, low temperature fluidity and additive solubility, in addition to biodegradability.

History

With the advent of the industrial age, particularly at the beginning of the 20th century, mineral oils became a standard resource for lubricating machinery. As the demands placed on modern industrial equipment exceeded the capabilities of traditional oils, the lubricants industry turned to synthetic products.

Finding that natural oils are unable to deliver long-term performance on their own, the industry designed alternatives that combine the benefits of both biobased and mineral oils, along with additives, to deliver the required performance. As base stocks, synthetic esters provide virtually limitless combinations of performance characteristics suitable for any application.

Performance

Thanks to the vast array of alcohols and acids to choose from when making synthetic esters, formulators can create a lubrication product for nearly any specific environmental or application challenge. Such products provide a balanced solution to the puzzle of producing environmentally sound lubricants that are also effective in demanding environments.

Since the introduction of synthetic esters more than 50 years ago, they have been incorporated into virtually every industrial application. They now provide thermal stability, long service life, and are effective boundary lubrication. Applications in which synthetic esters have been adopted include grease, hydraulic fluids, aviation and compressor oils, and industrial, automotive, gear and chain lubricants.

Cost

Many ester products have been significantly more expensive than mineral oils, but new technologies are becoming available and production capacity is increasing–factors that can reduce price points.

Further, synthetic ester producers point out that the cost savings to be gained in using their lubricants outweigh the higher material prices. Better performance, long-term stability and low maintenance lead to an overall advantage for end users.

Environmental Advantages

Biodegradability is a critical attribute for many lubricants. Until recently, however, biodegradable products exhibited significant deterioration in performance with time and stress.

New developments in the manufacture of esters are bridging the gap between environmentally conscious products and high-performance products that meet the needs of mission-critical applications, both industrial and consumer.

Growth

Global demand for all lubricant base stocks was 36 million tons in 2015, according to Kline and Co., with 8 percent used to blend synthetic and semi-synthetic lubricants. Biosynthetic Technologies also cites Kline in its prediction of 3 to 4 percent compound annual volume growth for synthetic base oils from 2015 to 2020. Synthetic esters are predicted to be at the high end of that estimate, at 4.1 percent growth. Producers of biobased esters can also hope to capture some of the projected 5 to 12 percent growth for biobased lubricants.

Synthetic esters are increasingly becoming the preferred alternative to mineral oils for a wide range of applications, thanks to their biodegradability and performance characteristics.

In this Spotlight, Oxea GmbH and Biosynthetic Technologies explain their own approaches to esters and ester based lubricants.

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Biosynthetic Technologies

Biobased Performance

Biosynthetic Technologies is a California-based company that is leading the development of a biosynthetic estolide technology platform. Biosynthetic Technologies is developing chemical technologies that are sustainable and reduce dependence on legacy petroleum based products. The adoption of these new high-performance products has the potential to diminish pollution and create new jobs in many industry sectors.

These highly functional biosynthetic products are produced from oils found in plants (fatty acids) and can be used in an array of applications including motor oils, marine lubricants, small-engine oils, hydraulic fluids, refrigeration/compressor oils, greases, dielectric fluids, gear oils, general-purpose lubricants, and other commercial and industrial lubricant products.

In addition to providing performance that is competitive and often superior to petroleum counterparts, these products are biodegradable. The ability to reduce the environmental impact of petroleum products is a huge improvement over current projects. Used motor oil alone is responsible for 40 percent of water pollution in the United States. This real-world impact on health, environmental and economic costs is remediated by biodegradable products.

Several major manufacturers of automotive, industrial and marine lubricants are already formulating and certifying finished products using these new biosynthetic base oils.

Offering alternatives to petroleum based oils in lubricants with high-performing synthetic oils that are renewable, biodegradable and nontoxic is Biosynthetic Technologies mission.

Biosynthetic Technologies, partnering with other major specialty chemical manufacturers, has a continuous-flow demonstration plant in Baton Rouge, Louisiana, that incorporates all of the elements of a commercial manufacturing facility currently in the final engineering phase. This is a fully functional, proof-of-concept manufacturing demonstration. The full-scale implementation will offer an energy efficient, continuous-flow design that limits byproducts to glycerin and a small amount of water, significantly reducing production costs. The resulting product is highly competitive in both price and performance.

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Tailor-made Fluids

Oxea is an industry leader in the manufacture of oxo chemicals. With an annual production capacity of more than 1.3 million tons per annum, they are one of the largest producers of oxo chemicals and downstream derivatives worldwide. Synthetic fatty acids are a key segment in their product portfolio and enable the development of the most exciting new ester products.

Synthetic esters are typically classified into monoesters, diesters, polyolesters, aromatic esters and complex esters. However, even this classification is an oversimplification
regarding the broad range of properties that can be obtained using different alcohols/polyols and carboxylic acids to prepare the ester. Because of the many combinations of alcohols and carboxylic acids that are possible, the properties of the ester can be tailored for each application, allowing them to fulfill nearly any requirement. Physical and chemical product properties are strongly impacted by the chain length of the carboxylic acid, as well as the degree of branching and saturation. For example, the viscosity of the ester increases using a longer or a more branched carboxylic acid. Even the hydrolytic stability can reach excellent values when the reaction of the ester group with water is sufficiently hindered, for example, by using branched carboxylic acids.

Oxea produces numerous synthetic carboxylic acids that allow ester producers to tailor their fluids to the requirements of their customers. Oxea guides other ester producers as they select acids and, with their internal technology team, develop products that will meet the future needs for acids in the lubricant market. Oxea is committed to supply these acids with utmost care for both quality and availability. Their continued investments in this technology ensure they remain a global leader in the production of synthetic acids.

Oxea also promotes the use of synthetic acids by offering selected esters direct. One example is their recently introduced OXLUBE L9-TMP. This product leverages the viability of pelargonic acid as an alternative to C8/C10 acids derived from coconut or palm kernel oil.Because of the similar average chain length of the linear C9 and C8/C10 acids, the corresponding TMP esters show similar properties. In fact, slight advantages of the L9-TMP in terms of volatility, oxidation stability, and biodegradability were observed. As the dedicated production of L9-TMP is based on synthetic feedstocks, supply and pricing are reliable. Further examples of the Oxea portfolio used in lubricant applications comprise trimellitates, such as L9TM, polyols such as NPG and TMP, and a broad range of synthetic alcohols.

Anticipating robust growth, Oxea has invested adequately into the resources needed to maintain their
leadership position and meet future growth. Oxea offers more than 70 products that ensure reliable supply to
customers over a wide range of industries and covering many varied end market applications, including construction, paints & coatings, inks & printing, automotive, consumer goods, feed additives, cosmetics, healthcare, fine chemicals and agrochemicals industries. Their products are also valued components in specialized applications within the chemical industry such as coatings, plasticizers and lubricants.