Oil Content of Petroleum Wax

Oil content, %, as described in ASTM Standard D721-65T, Oil Content of Petroleum Waxes ... 

ASTM D721, Standard Test Method for Oil Content of Petroleum Waxes, A STM Annual Book of Standards (WestConshohocken, PA American Society for Testing and Materials). 

D721. Oil content of petroleum waxes D850, Distillation of industrial aromatics X X X... 

Refers to the removal of oil from petroleum wax a refinery process usually involving filtering or pressing a chilled mixture of slack wax and a solvent that is miscible in the oil, to lower the oil content of the wax. 

Paraffin wax is macrocrystalline, britde, and is composed of 40—90 wt % normal alkanes, with the remainder C g—isoalkanes and cycloalkanes. Paraffin wax has Httle affinity for oil content fully refined paraffin has less than 1 wt % cmde scale, 1—2 wt %, and slack [64742-61-6] above 2 wt %. Within these classes, the melting point of the wax determines the actual grade, with a range of about 46—71°C. Typical properties of petroleum waxes are listed in Table 3. 

Oil Content. The production of petroleum waxes involves the removal of oil therefore, the oil content (actually the percentage of oil and low molecular weight fractions) is one indication of the quaUty of the wax. Oil content is deterrnined (ASTM D721) as that percentage of the wax soluble in methyl ethyl ketone at —31.7 C. 

Sheu, E. Y. Acevedo, S. (2006). A Dielectric Relaxation Study of Precipitation and Curing of Furrial Crude oil. Fuel, Vol.85, No.14-15,1953-1959 Speight, J.S. (2007). The Chemistry and Technology of Petroleum. Fourth Edition, CRC Press/Taylor Francis, Boca Raton, FL, USA, ISBN 978-084-9390-67-8 Strausz, O.P. Mojelsky, LT.W. Lown, E.M. (1992). The Molecular Structure of Asphaltene an Unfolding Story. Fuel, Vol.71, No.l2, pp. 1355-1363 UOP 46-85. (1985). Paraffin Wax Content of Petroleum Oils and Asfhalts. UOP Methods, UOP Inc, Des Plaines, IL, USA... 

The separation of waxes on packed columns has been carried out since the 1960s [2,3 ], and capillary column chromatography was used in 1970 to separate a microcrystalline wax up to carbon chain length (also known as carbon number) M Csg [4]. In the early 1980s, tire manufacturers requested ASTM D02.04 to produce a capillary column gas chromatography method to analyze rubber waxes (with oil content of less than 10%) from carbon number -C,7 to n-C44. ASTM D02.10, the Subcommittee on Petroleum Wax, was asked by D02.04 to carry out the development of the method. 

Petroleum Waxes. Waxes derived from petroleum are hydrocarbons of three types paraffin [64742-43-4] (clay-treated) sernimicrocrystaUine or intermediate and microcrystalHne [64742-42-3] (clay-treated). SernimicrocrystaUine waxes are not generally marketed as such (7). Others include acid-treated, chemically neutrali2ed, and hydrotreated and paraffin and hydrocarbon waxes, untreated. The quaHty and quantity of the wax separated from the cmde oil depends on the source of the cmde oil and the degree of refining to which it has been subjected prior to wax separation. Petroleum waxes are produced in massive quantities throughout the world. Subject to the wax content in the cmde, paraffin and, to a substantially lesser degree, microcrystalHne wax are produced in almost all countries of the world that refine cmde oil. Production capacity in the United States and imports for the years 1990 to 1995 are Hsted in Table 2. Canada suppHes over 50% of the petroleum wax imported into the United States (3). 

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. ... 

Petroleum crude oils, which are divided for the purposes of conventional classification into three main types—asphalt (or naphthenic)-base, paraffin-base, and mixed-base—contain varying amounts of hydrocarbons which readily solidify and are identified as wax. The asphalt-base crudes may contain only a trace of wax, while the wax content of the paraffin-base crudes and the mixed-base crudes may be as high as 15% or higher (73). Crude oils with a wax content as high as 35% are known. 

The wax content of crude petroleum in itself is of no immediate concern to the refiner, although it may be a major problem to the producer because of waxing up of well casing and sucker rods. It may cause difficulty in transportation of the raw crude oil, and wax settling out in tanks may also become troublesome. The refiner, however, is concerned with wax occurring in the oils to be processed and in the finished oils. The major portion of waxes present in crude petroleum boil in the same range as the lubricating oils produced from the crude oil, so that the wax and oil cannot be separated by distillation. Waxes are... 

Although the bulk of low oil content waxes, especially those having melting points below about 135° F., are produced today by sweating, solvent deoiling is fast becoming the more important method for the production of all waxes derived from petroleum. 

Petroleum wax is of two general types the paraffin waxes in petroleum distillates and the microcrystalline waxes in petroleum residua. The melting point of wax is not directly related to its boiling point, because waxes contain hydrocarbons of different chemical structure. Nevertheless, waxes are graded according to their melting point and oil content. 

Petroleum ceresins and petrolatum wax are isolated from residues. Paraffin wax, on the other hand, is almost invariably isolated from distillates by solvent extraction or precipitation followed by sweating or emulsion de-oiling. According to Sachanen (77), the wax content of lubricating oil fractions is commonly 10% =b 5%. 

A. Crookell and A. Barker, New Developments in the Measurements of Oil Content in Waxes Using Benchtop Pulsed NMR, Paper AM-98-49, presented at the Annual Meeting of the National Petroleum Refiners Association,, March... 

For example. Burger et al. (1981) characterized an oil sample composed of 14% wax, 58% of which included hydrocarbons in the range and Barker (1995) noted that microcrystalUne waxes in a refined petroleum sample was composed of 20-40% H-alkanes, 15-40% wo-alkanes and 35% cycloalkanes. The HMWHCs in the 40. region are of particular interest since they are thought to be the primary culprit in wax deposition problems. Case studies have demonstrated that a minimal microcrystalline wax content of 2% in an oil can result in wax deposition problems (Holder Winkler 1965 Tuttle 1983 Ajienka Ikoku 1990). 

The oils in wells 30/7a-8 and 30/7a-P7 also provide evidence that direct leakage into the Chalk from the Pre-Cretaceous in Joanne is an unlikely model. The 30/7a-8 and 30/7a-P7 Pre-Cretaceous petroleums have low wax contents and are believed to have been sourced from the kitchen to the west or southwest. It is therefore likely that the Pre-Cretaceous oil in 30/7a-3 would also have a low wax content. Although the wax contents of the Joanne Chalk oils are lower than those from 30/7a-4a and 30/7a-6, they are considerably higher than those in the 30/7a-8 and 30/7a-P7 petroleums (Fig. 8), making it unlikely that they leaked from the underlying Pre-Cretaceous reservoirs. 

The Palaeocene petroleums from the Judy/ Joanne Field are the least mature and have the lowest wax contents of any fluid samples analysed during this study. They are phase separated condensates resulting from physical segregation of a gas phase from a two-phase oil and gas accumulation. 

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