Pour point depression

The problem is similar to the case of lubricating oils polyalkylnaphthalenes or alkyl polymethacrylates called pour point depressants have been commercialized to lower the pour point. 

Examples of pour point depressants for lubricating oils. 

Pourpoint additives Pour-point depressants Pour un Homme... 

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

Practically all lubricating oils contain at least one additive some oils contain several. The amount of additive that is used varies from < 0.01 to 30% or more. Additives can have detrimental side effects, especially if the dosage is excessive or if interactions with other additives occur. Some additives are multifimctional, eg, certain VI improvers also function as pour-point depressants or dispersants. The additives most commonly used in hydrautic fluids include pour-point depressants, viscosity index improvers, defoamers, oxidation inhibitors, mst and corrosion inhibitors, and antiwear compounds. 

R, mst inhibitor O, oxidation inhibitor D, detergent—dispersant VI, viscosity-index improver P, pour-point depressant W, antiwear EP, extreme pressure F, antifoam and M, friction modifier. 

Pour-Point Depressants. The pour point of alow viscosity paraffinic oil may be lowered by as much as 30—40°C by adding 1.0% or less of polymethacrylates, polymers formed by Eriedel-Crafts condensation of wax with alkylnaphthalene or phenols, or styrene esters (22). As wax crystallizes out of solution from the Hquid oil as it cools below its normal pour point, the additive molecules appear to adsorb on crystal faces so as to prevent growth of an interlocking wax network which would otherwise immobilize the oil. Pour-point depressants become less effective with nonparaffinic and higher viscosity petroleum oils where high viscosity plays a dominant role in immobilizing the oil in a pour-point test. 

Viscosity (Viscosity-Index) Improvers. Oils of high viscosity index (VI) can be attained by adding a few percent of ahnear polymer similar to those used for pour-point depressants. The most common are polyisobutylenes, polymethacrylates, and polyalkylstyrenes they are used in the molecular weight range of about 10,000 to 100,000 (18). A convenient measure for the viscosity-increasing efficiency of various polymers is the intrinsic viscosity Tj, as given by the function... 

Branched-chain acids have a wide variety of industrial uses as paint driers (7), vinyl stabilizers (8), and cosmetic products (9). Cobalt and manganese salts of 2-ethyIhexanoic acid and neodecanoic acid are used as driers for paint, varnishes, and enamels litbium, magnesium, calcium, and aluminum salts of 2-ethyIhexanoic acid are used in the formation of greases and lubricants (see Driers and metallic soaps). Derivatives of isostearic acid have been used as pour point depressants in two-cycle engine oils, as textile lubricants, and in cosmetic formulations. Further industrial appHcations can be found (10). 

A number of higher n-alkyl methacrylate polymers have found commercial usage. The poly-(n-butyl-), poly-(n-octyl-) and poly-(n-nonyl methacrylate)s have found use as leathering finishes whilst polyflauryl methacrylate) has become useful as a pour-point depressant and improver of viscosity temperature characteristics of lubricating oils. 

The pour point of a crude oil or product is the lowest temperature at which an oil is observed to flow under the conditions of the test. Pour point data indicates the amount of long-chain paraffins (petroleum wax) found in a crude oil. Paraffinic crudes usually have higher wax content than other crude types. Handling and transporting crude oils and heavy fuels is difficult at temperatures helow their pour points Often, chemical additives known as pour point depressants are used to improve the flow properties of the fuel. Long-chain n-paraffins ranging from 16-60 carhon atoms in particular, are responsible for near-ambient temperature precipitation. In middle distillates, less than 1% wax can be sufficient to cause solidification of the fuel. ... 

Paraffin crystalline waxes Apart from asphaltenes, a number of differing molecular weight paraffinic waxes are also present. These progressively crystallize at lowering temperatures (their respective pour points). These waxes increase friction and resistance to flow, so that the viscosity of the fuel is raised. This type of problem is controlled by the use of pour-point depressants (viscosity improvers), which limit the growth of the crystals at their nucleation sites within the fuel. They also have a dispersing effect. 

Cold flow improvers (pour point depressants) These viscosity improvers are often specified in cold climates for unheated gas oil or where existing residual oil heaters are inadequate. The use of these paraffin crystal modifiers permits fuel to continue to flow at temperatures of 30 to 40 °F lower than the point at which wax crystallization would normally occur. 

If primary alcohols with a straight chain of 10-20 carbon atoms are initially alkoxylated by a mixture of ethylene and propylene oxides followed by phosphorylation, a pour point depression to 8°C will occur, whereas phosphate esters derived from nonylphenol are liquid at temperatures as low as 2°C. Phosphoric acid esters on the base of linear primary alcohols (Cn-Cl5) generally solidify below 24°C [50] (Table 2). 

Pour-point depressants Reduce pour points of waxy cmdes... 

Ordinary dicarboxylic acids or dimeric fatty acids are condensed with fatty amines to give emulsion breakers [822,823,1029,1030]. Oxalkylated fatty amines and fatty amine derivatives have properties other than emulsion braking in particular, they can act as corrosion inhibitors and pour-point depressants. 

J. Balzer, M. Feustel, M. Krull, and W. Reimann. Graft polymers, their preparation and use as pour point depressants and flow improvers for crude oils, residual oils and middle distillates. Patent US 5439981, 1995. 

G. S. Fung, P. E. Depalm, and P. Sharma. Pour point depression unit using mild thermal cracker. Patent US 6337011,2(X)2. 

G. Meyer, D. Kessel, and I. Rahimian. The effect of pour point depressants of the polyacrylate-type on crude oil (Wirkung von Stockpunk-temiedrigem des Polyacrylat-Typs auf Rohole). Erdol Kohle-Erdgas-Petrochem, 48(3) 135-137, March 1995. 

M. N. Sunil Kumar. Review on polymeric and copolymeric pour point depressants for waxy crude oils and studies on bombay high crude oil. Quart J Tech Pap (Inst Petrol), pages 47-71, October-December 1989. 

In addition to refining techniques, compounds identified as wax crystal modifiers are available for use in contending with the effects of wax in fuels. Wax crystal modifiers, also called pour point depressants or cold flow improvers, are typically polymeric compounds which have the ability to crystallize with fuel wax as it forms. By co-crystallizing with wax, the modifiers typically effect a change in the size, shape, and conformation of wax crystals. Other wax crystal modifiers function by dispersing or inhibiting the nucleation or growth of wax crystals within a fuel or oil. 

Nalco Chemical Company. 1984. Procedures for evaluation of pour point depressants. TF-98. Sugar Land, Tex. 

POUR POINT DEPRESSANT. An additive for lubricating and automotive oils that lowers the pour point (or increases the flow point) by 11.0°C. The agents now generally used are polymerized higher esters of acrylic add derivatives. They are most effective with low-viscosity oils. See also Petroleum. 

The oil yields calculated from the analyses of the denormal products in Table III are plotted versus denormal product pour point in Figure 12. It is seen that 60% of the ii-paraffins must be removed before the pour point begins to decrease. Further extraction of the ti-paraffins to 88% of the theoretical (maximum) yield of 16.7 wt % n-paraffins then reduces the pour point from 294 K to 266 K. It appears that extraction of the remaining n-paraffins may lower the pour point to the desirable range of 261-255 K. It would be interesting to determine the effect of pour point depressants on the denormal oil product. 

Pour point depressants The crystallization of paraffin wax in the base oil can lead to a gelation of the lubricant at low temperature. Pour point depressants cannot prevent crystallization but change the shape of the crystals from a needle-like to a densely packed, rounded one. This leads to a much better flow behavior. 

---