Crystallization of wax

The crystallization of wax from lubricating oil fractions makes better oil. This is done by adding a solvent (often a mixture of benzene and methyl ethyl ketone) to the oil at a temperature of about -5 F. The benzene keeps the oil in solution and maintains fluidity at low temperature the methyl ethyl ketone acts to precipitate the wax. Rotary filters deposit the wax crystals on a sp woven cloth stretched over a perforated cylindrical drum. A vacuum in the drum draws the oil through the perforations. The wax crystals are removed from the cloth by metal scrapers and ol vent-washed to remove oil followed by solvent distillation to remove oil for reuse. 

The crystallization of waxes at lower temperatures causes reduced liquidity of waxy crude oils, which considerably hampers the transportation of crude oils through long distance pipelines. Taking into consideration all of the economic aspects, additive treatment, which depresses the pour point and improves the... 

The temperature at which the base stock freezes due to crystallization of wax must be lowered by wax removal so that equipment can operate at winter temperatures. 

As with scale formation the precipitation of organic compounds will depend on the temperature distribution. Bott and Gudmundsson [1977] proposed a qualitative model of organic precipitation. If a waxy hydrocarbon flowing across a cold surface and the metal/liquid interface is at the cloud point temperature, crystals of wax will form on the surface. If the surface temperature is below the cloud point temperature the cloud point temperature will be located away from the surface towards the bulk liquid. The precise location will depend on the thermal resistance of the laminar sub-layer combined with the resistance of any deposit already on the surface. High thermal resistance between the solid surface and the... 

Neutral Degras. [Fanning] Fatty esters of wool grease lubricant, dasticizer for tvire drawing compds., slushing and cutting oils, rust preventative, adhesives textite inhibits crystallization of wax components. 

Cloud point of a lubricant to be applied by a capillary feed system or wicking arrangement imisl be low so that the oil How does not stop due to deposition of crystals of wax in the capillary or wick interstice. -. Cloud point is hcli)ful in identifying the temperatures at which wax separation may clog the filter screens in the fuel intake system of diesel engines. Oils of naphthenic type, which are almost wax-free, show o ry low cloud iKiinfs and this fact may l-rc useful in identifying the source of the oil. 

For oils containing wax, pour point is the temperature at which crystallization of wax has gone to such an extent that the oil will stop flowing if cooled furllier. This temperature is known as Wax pour point . For oils free from wax, xnir point is Ihe temperature at which the viscosity is so iiigh dial the. oil will slop (lowing, if cooled further, due to further iiKicase in viscosity. This temperature is known as Viscosity pour point . 

Sulfuric acid also removes or dissolves resinous or asphaltic substances that may be present because of poor fractionation, entrainment, or cracking. These materials tend to inhibit the crystallization of wax, and hence acid treatment often raises the pour point. Oxygen compounds, such as naphthenic acids and ketones, and substances such as alcohols mid aldehydes that are formed by high-temperature oxidation are dissolved by sulfuric acid, but when diluted with oil their removal is never complete. Nitrogen bases similar to quinoline or pyridine, which are produced in small quantities during distillation, are easily dissolved in dilute add. 

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