[ DEFINITION: CHEMICAL SYNTHESIS; the process of constructing complex chemical compounds from selected, simpler ones; it is applied to all types of chemical compounds, but most syntheses are of organic molecules; chemical synthesis involves the combination of two or more selected atoms (or molecules) to make a finished and predictable product].

[ DEFINITION: SYNTHETIC LUBRICANT; a lubricant made by the process of chemical synthesis in contrast to the successive refinement or extraction of mineral oils].

Since many chemical substances do not occur naturally, or in enough quantity or purity for commercialization, we resort to chemical synthesis to make new products.

For example aspirin is made by synthesis using an Esterification reaction. Salicylic Acid is treated with Acetic Anhydride, an acid derivative, causing a chemical reaction that turns salicylic acid’s Hydroxyl group into an Ester group (R-OH → R-OCOCH3). This process yields aspirin and Acetic Acid, which is considered a Byproduct of this reaction. Small amounts of a specific acid are always used as a Catalyst. (D. R. Palleros, Experimental Organic Chemistry. New York: John Wiley & Sons. (2000)).

During a chemical synthesis, we refer to the starting materials as the reactants. Think of the reactants as your basic building blocks; they are your atoms (or molecules) that are absolutely required to complete any chemical synthesis reaction. The type of product made varies and is dependent on the reactants.

When the atoms (or molecules) combine, they will form a product. What drives this ability to make a product, using reactants, is a chemical reaction, a process that is driving the formation of a product using different starting materials, or reactants. With chemical syntheses, these processes generally only go in one direction.

A synthetic chemical is then made from the ground up in the laboratory or the chemical processing plant by the process of synthesis, as differentiated from refinement or extraction.

A synthetic base oil is produced from well-defined, carefully chosen chemical compounds, and by a specific chain of chemical reactions. A molecularly engineered base stock is optimized for viscosity index, pour point, volatility, oxidative stability, flash point, shear stability, and other desirable properties. Classified as API Group IV and Group V base oils.

The use of the word “synthetic” in the lubricants industry has historically been synonymous with polymerized base oils such as poly-alpha olefins (PAOs), Esters, and other synthesized base oils, such as alkylated naphthalenes (AN), which are made from selected starting atoms or molecules.

Some authors have stated that the term “synthetic” was given a special meaning by the lubricants industry because these types of oils were the only components available for high-performance lubricants at that time. This is purely an attempt to obfuscate the issue.

Since PAO (Group IV) and Ester base oils (Group IV) are synthesized base oils, what better phrase to use than, “Synthetic Lubricant?”

Other authors and marketing media have attempted to further obfuscate the issue by using the word, “Performance,” in advertising media, as if ‘performance” somehow equaled “synthetic.” While Group III base oils approach the characteristics of Group IV base oils, “performance” is not a chemistry term, but rather an ambiguous term used by marketing.

In an attempt to further clarify the issue, finished engine oils (base oils plus additives) are NOT to be placed into any base group, as has been attempted by our beloved and uneducated marketing folks.

In academia and in the chemical industry, the term “synthetic” never meant anything different than the definition given above.

The first commercially viable process for making Group IV PAO was pioneered by Gulf Oil in 1951 using an AlCl3 catalyst. Mobil patented an improved process using a BF3/AlCl3 catalyst in the 1960s. [ DEFINITION: Polymerization; the process of forming a repeating chain molecule].

[ DEFINITION: Monomer; A monomer is a molecule that forms the basic unit for polymers; Monomers may bind to other monomers as well. Monomers may be either natural or synthetic in origin and form a repeating chain molecule via a process called polymerization].

[ DEFINITION: Oligomers; Oligomers are polymers consisting of a small number (typically under one hundred) of monomer subunits].

[ DEFINITION:Oligimerization; a chemical process that converts monomers to macromolecular complexes through a finite degree of polymerization].

[ DEFINITION:Olefin; an alkene, or unsaturated hydrocarbon with the general formula CnH2n. The simplest olefin is ethylene (ethene) gas, H2C=CH2 or simply, C2H4].

PAO’s are the workhorses of synthetic and Blend lubricating oils, comprising greater than 45% of the synthetic base oil market.

For PAO synthesis, the starting olefins (see above definition) can be is 1-Decene, (C10H20), or 1-Dodecene, or 1-Tetradecene.

1-Decene, or 1-Dodecene, or 1-Tetradecene liquids are produced by the Oligomerization of the simpler ethylene gas molecule. It is one of the many Linear Alpha-Olefins (LAOs) used in the growth process to finally yield LAOs.

[ NOTE: 1-Decene liquid has a kinematic viscosity of 1.013 cSt@20C, the 1-Dodecene liquid has a kinematic viscosity of 1.6 cSt@20C, and the 1-Tetradecene liquid has a kinematic viscosity of 5.9 cSt@20C! Compare to the viscosity of water which has a kinematic viscosity of 1.0034 cSt@20C].

The 1-Decene, or 1-Dodecene, or 1-Tetradecene liquids becomes a PAO liquid by polymerization (the linking together of monomers) using the Friedel-Crafts process. This process uses a catalyst, specific temperature conditions, and specific pressures to give rise to the higher olefin oligomers, such as the C20 through C70 olefins. The degree of polymerization is dependent upon the type of catalyst used. For example, a Boron Triflouride (BF3) catalyst gives low viscosity base stocks from about 2.4 to 8.0 cSt. An Aluminum Trichloride (AlCl3) catalyst will produce higher viscosity PAOs from 10 cSt on up.

The final process in the PAO synthesis is to introduce hydrogen at specific temperatures and pressures to create a fully saturated hydrocarbon. This hydrogenation process enhances the oxidation stability of the PAO.

So the PAO development process is essentially: ethylene gas >> 1-Decene, or 1-Dodecene, or 1-Tetradecene liquid monomer >> Oligimerization into liquid polymers >> Hydrogenation of polymer >> Finished PAO.

PAO’s offer improved viscosimetrics’ (higher Viscosity Indices), lower volativities (decreased oil consumption), higher heat conduction (approximately 10% greater thermal energy transfer), and improved oxidation stability (longer drain intervals) over Group I to III mineral oils.

ESTERS are a class of synthesized products derived from the chemical reactions of selected alcohols and acids.

[ DEFINITION: HYDROLYSIS; a chemical reaction that causes a substance, in the presence of water, to split into two parts. In such reactions, one fragment of the target molecule (or parent molecule) gains a hydrogen ion].

Esters occur naturally in many plant and animal species. However, unprocessed plant and animal oils also contain other products that tend to increase oxidation and lead to degradation, and therefore are not suitable for lubricants in their unmodified states.

Many plant and animal oils are processed such that after pressing and or chemical extraction, the acids are separated from the other products. The resulting acids are then reacted with selected alcohols to produce an ester with characteristics and qualities far superior to unmodified plant and animal oils.

Ester starting materials are also made from chemicals derived from petroleum refining processes.

(See also, Esters General

and,

This Forum Post for a review of Esters in synthetic lubricants).

For example, a very useful ester in additive chemistry is the ZDDP molecule, whose function is as an Anti-Wear (AW) and Oxidation Inhibitor (OI). Members of the zinc dialkyldithiophosphate category are substances prepared by reacting phosphorous pentasulfide (P2S5) with one or more primary or secondary C3-C10 branched or linear alcohols to form the phosphorodithioic acid ester. The only exception is the alkaryl dithiophosphate where the alcohol moiety is tetrapropenylphenol. The dithiophosphoric acid ester is further diluted with 10-15 wt-% highly refined lubricating base oil (typical CAS #s 64742-54-7 and 64741-88-4) before it is neutralized with zinc oxide. The oil acts as a solvent in the neutralization reaction, manages the viscosity of the final product and improves consistency. The zinc complex that is formed upon neutralization is not a salt in the traditional sense, since the Zn-S bond is more coordinate covalent in character than ionic. (American Chemistry Council Publication 210-144870). There are about 15 versions of ZDDP chemistry.

In fact, many other additive chemistries are esters or in an esterified form.

Synthetic Group V base oils include (but not limited to), esters (dibasic and polyol), alkylated benzenes (ABs), alkylated napthalenes (ANs), Polyisobutylenes (PIBs), phosphate esters, silicones, PAG’s (especially oil soluble PEGs or OSPs), and other similar synthesized lubricants not including Group IV.  Note: Not all oils in the Group V category are synthesized oils. We are limiting our discussion to those Group V oils that are made by the synthesis process.

Ester’s and PAO’s are often used in blending stocks to improve the characteristics of Group I through III base oils.

Esters offer advantages to base oil mixes such as improved solvency of additives, improved sludge dispersancy, lower friction coefficient, improved bio-degradeability, and improved thermal stability.

One of the first companies to successfully market a majority, ester-based finished oil was the Amsoil Corporation. (Remember, I said, “successfully”). This was a di-ester based finished oil that was formulated and packaged by the Hatco Corporation, a pioneer in the production of a wide range of various ester base oils.

As the price of esters increased, and reached a certain Return-on-Investment (ROI) point, Amsoil and other companies began formulating finished products containing PAO’s with esters and other Group V base oils such as AN’s.

Due to the possibility of hydrolysis in some esters, Group V alykylated naphthalenes (AN’s) are often used alone or in combination with esters in majority Synthetic formulations.

SUMMARY OF SECTION II: While Group III base oils have many positive characteristics that approach Group IV and V oils, Groups IV and V are truly synthesized oils using selected starting atoms or molecules, with specific and predictable outcomes. So hopefully, we have at least clarified the issue somewhat regardless of which side of the issue you may tilt.