Viscosity paraffins

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. 

High viscosity paraffinic oils are the preferred petroleum plasticisers for HR, due to their compatibility and high viscosity index. 

Visbreaking severity is monitored to help minimize cracking and alteration of the nature of asphaltenes within the visbreaker feed. Paraffinic side chain cracking or destruction of the asphaltene-resin complex may occur during visbreaking operations and may result in precipitation of asphaltenes from solution. Asphaltene precipitation has been seen especially when visbroken material is blended with lighter-viscosity paraffinic fuels. 

Applications in the chemical field, include extrusion of an oil phase containing a photographic hydrophobic material through a microporous membrane into water [89] and emulsification of low-viscosity paraffin wax in water [90],... 

Fig. 7.1. Schematic view of the light-scattering apparatus 1, stainless steel vessel 2, inlet for thennostatting fluid 3, windows to illuminate the film 4, film 5, ground glass frame 6, glass vessel with soap solution 7, mechanism to move vessel up and down 8, tumable part of the cover 9, tube 10, photomultiplier 11, prism 12, concentric grooves filled with high-viscosity paraffinic oil 13, concentric rims. (From Ref. 138, courtesy of American Institute of Physics.)...

The pour point is the lowest temperature at which an oil can still pour while it is cooled, without agitation, under standardized conditions. The pour point of paraffinic bases is linked to the crystallization of n-paraffins. The pour point of naphthenic bases is related to a significant viscosity increase at low temperatures. This property can be improved by additives. 

The viscosity of a paraffinic crude increases rapidly with decreasing temperature on the other hand, for the naphthenic crudes, the increase in viscosity is more gradual. 

A refinery lubricant base stock is obtained having an viscosity index around 100, certain hydrotreatments result in Vi s of 130, and paraffin hydroisomerization provides oils with a VI close to 150. 

In a single stage, without liquid recycle, the conversion can be optimized between 60 and 90%. The very paraffinic residue is used to make lubricant oil bases of high viscosity index in the range of 150 N to 350 N the residue can also be used as feedstock to steam cracking plants providing ethylene and propylene yields equal to those from paraffinic naphthas, or as additional feedstock to catalytic cracking units. 

The products manufactured are predominantiy paraffinic, free from sulfur, nitrogen, and other impurities, and have excellent combustion properties. The very high cetane number and smoke point indicate clean-burning hydrocarbon Hquids having reduced harmful exhaust emissions. SMDS has also been proposed to produce chemical intermediates, paraffinic solvents, and extra high viscosity index (XHVI) lubeoils (see Lubrication and lubricants) (44). 

Low temperature filtration (qv) is a common final refining step to remove paraffin wax in order to lower the pour point of the oil (14). As an alternative to traditional filtration aided by a propane or methyl ethyl ketone solvent, catalytic hydrodewaxing cracks the wax molecules which are then removed as lower boiling products. Finished lubricating oils are then made by blending these refined stocks to the desired viscosity, followed by introducing additives needed to provide the required performance. Table 3 Usts properties of typical commercial petroleum oils. Methods for measuring these properties are available from the ASTM (10). 

Fig. 10. Viscosity—pressure curve for typical petroleum oils (—) paraffinic (-) aUcycHc and ( ) soHd. To convert MPa to atm, divide by 0.101.

In the propane process, part of the propane diluent is allowed to evaporate by reducing pressure so as to chill the slurry to the desired filtration temperature, and rotary pressure filters are employed. Complex dewaxing requires no refrigeration, but depends on the formation of a soHd urea—/ -paraffin complex which is separated by filtration and then decomposed. This process is used to make low viscosity lubricants which must remain fluid at low temperatures (refrigeration, transformer, and hydraulic oils) (28). 

The majority of secondary plasticizers ia use are chlotinated paraffins, which are hydrocarbons chlotinated to a level of 30—70%. Eor a given hydrocarbon chain, viscosity iacreases with chlorine content, as does the fire retardancy imparted to the formulation. These materials aid fire retardancy due to thein chlorine content. Chlotinated paraffins of the same chlorine content may, however, have different volatiHties and viscosities if they are based on different hydrocarbon chaias (see Cm OROCARBONS and cm OROHYDROCARBONS, cm.ORiNATDD paraffins). 

The physical and chemical properties of chlorinated paraffins are deteanined by the carbon chain length of the paraffin and the chlorine content. This is most readily seen with respect to viscosity (Fig. 1) and volatiUty (Fig. 2) increasing carbon chain length and increasing chlorine content lead to an increase in viscosity but a reduction in volatiUty. 

Paraffin carbon chain length Nominal chlorine contents, %w / w Color hazen (APHA) Viscosity, mPa-s (=cP) Density, g/mL Thermal stability, %w/wHCl Volatihty, %w/w Refractive index... 

By selection of those chlorinated paraffins specifically developed for the PVC industry to match the properties of primary plasticizers, reductions in costs can be achieved without significant change in properties. However, certain aspects can be improved by the inclusion of chlorinated paraffin such as flame resistance, chemical and water resistance, low temperature performance, and the viscosity aging stabiUty in plastisols. 

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

Scraped-surface exchangers are particularly suitable for heat transfer with crystalhzation, heat transfer with severe folding of surfaces, heat transfer with solvent extraction, and heat transfer of high-viscosity fluids. They are extensively used in paraffin-wax plants and in petrochemical plants for ciystallization. 

It has been shown" that branched polymers have lower melting points and viscosities than linear polymers of the same molecular weight. The viscosity of the silicone fluids is much less affected by temperature than with the corresponding paraffins (see Figure 29.2). 

Figure 29.2. Viscosity-temperature curves for four commercial dimethylpolysiloxane fluids and for liquid paraffin. The numbers 1000, 300, 100 and 40 indicate the viscosities in centistokes at 38°C.

Fig. 9. Oil absorption vs. oil MW. 1x1x0.050 inch coupons of SBS (Stereon 841A) were immersed in paraffinic process oils of varying molecular weight (kinematic viscosity) for 300 days.

Paraffinic white oils from the same source but varying in molecular weight as indicated by their viscosity differences. 

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