Pour point depressants are used to allow the use of

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

based

mineral oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...

s at lower temperatures. The lowest temperature at which a

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) and lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

will pour is called a

pour point The pour point of a liquid is the temperature below which the liquid loses its flow characteristics. It is defined as the minimum temperature in which the oil has the ability to pour down from a beaker. In crude oil a high pour point is generally ...

Wax Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give lo ...

crystals, which form at lower temperatures, may interfere with

lubrication Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubrication mechanisms such as fluid-lubr ...

of mechanical equipment. High-quality pour point depressants can lower a pour point of an

oil additive Oil additives are chemical compounds that improve the lubricant performance of base oil (or oil "base stock"). The manufacturer of many oils can use the same base stock for each formulation and can choose different additives for each use. Additives ...

by as much as 40°C.

Methods

Pour point depressants do not lower the temperature at which wax crystals begin to form, called the

cloud point In liquids, the cloud point is the temperature below which a transparent solution undergoes either a liquid-liquid phase separation to form an emulsion or a liquid-solid phase transition to form either a stable sol or a suspension that settles as ...

, or the amount of wax that is formed—pour point depressants work by altering the crystal shape and size, which inhibits

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

crystal growth Crystal growth is a major stage of a crystallization, crystallization process, and consists of the addition of new atoms, ions, or polymer strings into the characteristic arrangement of the crystalline lattice. The growth typically follows an ini ...

. There are two known methods by which this may be achieved: surface

adsorption Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...

and co-crystallization.

Types

Any reduction in an oil's pour point depends on both the composition and properties of the oil, as well as the type of pour point depressant used. Other factors are the substance's relative

molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

, its

chemical composition A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds. Chemical formulas can be used to describe the relative amounts of elements present in a com ...

, and the substance's concentration in the oil. If the concentration of pour point depressant is too high, there may be a visible effect on viscosity at higher temperatures. Pour point depressants are only effective on refined oils. Non-refined oils contain

polyaromatic hydrocarbons A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, inciner ...

and

resins A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Comm ...

which act as

antagonists An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.engine oils with a

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

above SAE 30. Generally they are most effective on thinner oils like SAE 10, SAE 20 or SAE 30 grade oils. Alkylaromatics and aliphatic polymers are two types of pour point depressants that are commercially available. Most commercially available pour point depressants are

organic polymers A polymer () is a substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeating subunits derived from one or more species of monomers. Due to their broad spectrum of properties, both ...

, but nonpolymeric substances such as phenyltristearyloxysilane and pentaerythritol tetrastearate may also be effective.

Winter 1980-1981

In 1981 there was a problem with lubricating oil pumpability. The same thing happened the following winter, along with reports that oil would not flow out of containers. The issue seemed to be caused by olefin copolymers which caused the oil to gel in cold temperatures.

References

{{reflist Petrochemicals