Wax content

Petroleum with a high wax content presents difficulties in handling and pumping as well as producing distillate and residual fuels of high pour point and lubricating oils that are costly to dewax. 

All the standard methods for the determination of wax involve precipitating the wax from solvents such as methylene chloride or acetone under specified conditions of solvent-to-oil ratio and temperature. Measurements such as these give comparative results that are often useful in characteriz- 

On the other hand, the wax appearance point (ASTM D-3117) may be determined by cooling of a sample under prescribed conditions with stirring. The temperature at which the wax first appears is the wax appearance point. 

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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). 

Wax Content. The Deutsche Industrie Normen (DIN) method utilizes destmctive distillation of the asphalt, foUowed by freezing out of the wax in the distillate fractions. 

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. ... 

Ebercon, A., Blum, A. Jordan, W.R. (1977). A rapid colorimetric method for epicuticular wax content of sorghum leaves. Crop Science, 17, 179-80. 

The above outline of the evolution of the plant kingdom during coal-forming eras has been presented largely in the language of botanical anatomy. However, the alert chemist will note that the anatomical differences imply considerable quantitative and spatial differences in the distribution of the principal plant constituents [cellulose, lignin, cutin, suberin and other waxes, contents of protoplasmic cells, pigments, resins, sporopollenin. 

Brunnock et al. [67] have also determined beach pollutants. They showed that weathered crude oil, crude oil sludge, and fuel oil can be differentiated by the n-paraffin profile as shown by gas chromatography, wax content, wax melting point, and asphaltene content. The effects of weathering at sea on crude oil were studied parameters unaffected by evaporation and exposure are the contents of vanadium, nickel, and n-paraffins. The scheme developed for the identification of certain weathered crude oils includes the determination of these constituents, together with the sulfur content of the sample. 

Figure 1. Plot of wax content vs. wash temperature. Laboratory washing conditions. Key O unwashed , washed.

Levels of extractables in the unwashed, washed with finish, and washed without finish stocks were determined. Finish level as determined by ethyl alcohol extraction was 0.7%. Washing did not reduce wax content but did significantly reduce ethyl-alcohol and boiling-water extractables (Table IV). Dust level generated in carding was reduced about 50% by the washing treatment and was about the same whether or not the finish has been applied. Fiber properties were not affected by the washing treatments. (Table V). 

The Mississippi cotton was much more difficult to wet out than either the California or Texas cottons. This is apparently related to the nature of noncelluloslc constituents on the fiber surfaces. The Mississippi cotton was a mature, low noncellulose content cotton, whereas, both the California and Texas cottons had high noncellulose contents. The ratio of wax content to total noncellulosics was much higher for the Mississippi cotton than for either the California or Texas cottons. The surface of the Mississippi cotton is thus more hydrophobic and resists wetting, Levels of extractables and dust levels are summarized in Table VIII. 

Finish levels were near the target value of 0.4% and were about one-half that of the cotton from the first rayon wash line experiment. The wax contents of the cottons were lowered only slightly by the washing treatment, whereas, ethyl-alcohol extractables were lowered considerably as was expected. The final level of alcohol-extractables is related to the original level—the higher the initial level, the higher the percentage reduction. 

Finish level was 0.25% on dry fiber weight. Results of extractions showed that levels of wax content and alcohol extract-ables of the cottons containing no finish were no different from those of the same cottons washed on the rayon line. Fiber length, length uniformity, and strength were not affected by the washing treatment and were also identical to those of the same cottons washed on the rayon line. 

Lowering the cloud point and pour point values of a distillate fuel can be accomplished by blending the fuel with a low-wax-content distillate stream such as a kerosene or jet fuel. Also, additives are frequently used in conjunction with kerosene blending or as a substitute for kerosene blending to reduce the pour point of diesel fuel. Additives are not as frequently used to reduce the cloud point of diesel 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... 

The source of paraffin wax is the lighter lubricating oil fractions after distillation from the crudes. The wax content of these is commonly 10 zfc 5% (103). These oils set to gels due to crystallization of the wax and therefore wax removal is a necessity for lubricating-oil manufacture. Wax is a true by-product, yet one of such great value that at times it is prepared as a primary product and the oils are cracked. 

Shock Sensitivity of RDX/Polyethylene Wax, pressed to 95.2% theoretical maximum density as a function of wax content... 

It is concluded from this work that the wax content remains fairly constant at about 0.7% of the mix. More recent (1955, Ref 57) test results on the analysis of Compn B loaded 90mm shell indicate that the quantity of wax found in the cast is closer to 1%, and that it is distributed relatively uniformly thruout the cast. These findings are in agreement with previous results reported in Ref 53. There appears to be no advantage from either the speed of uptake or ultimate wax content in incorporating the wax first with the RDX before combining with TNT, rather than adding it directly to the RDX/TNT melt. If the slurry contains water, the wax is taken in much more slowly... 

With the successful incorporation of about 5% wax in the HBX expl, trials were conducted in attempting to similarly desensitize other cast expl materials (TNT, Compn B, Tritonal) by increasing the wax content (Ref 35). It was found that as much as 20% wax (Wax No 10) could be emulsified in TNT by use of a NC emulsifier. The mix showed negligible separation at 100° in several hours. However, because of the questionable stability of the NC, the use of... 

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