Dewaxing

Dewaxing (also called winterization) of sunflower oil is essential when the oil is to be used as salad oil. The presence of wax makes the oil appear cloudy at room temperature. The oil normally becomes cloudy in 5-6 h but with proper dewaxing the oil remains clear after 24 h of storage at 0°C. The following steps are used to dewax sunflower oil  

In this process the oil is reacted with hydrogen gas in the presence of a nickel catalyst. The majority of the oil is hydrogenated in batch reactors, commonly referred to as converters . Continuous reactors are used in rare cases. The reaction is started by heating the catalyst and the oil with hydrogen gas bubbling through with mechanical agitation. 

Traditional sunflower oil needs hydrogenation for industrial frying applications. The industry generally hydrogenates the oil to reduce the iodine value from 130 (nominal) to 108-110. The author s experience suggests that the iodine 

Iodine value Palmitic (%) Stearic (%) Oleic (%) Linoleic (%) 

The varieties, developed by USDA and seed companies, have already shown good yield and other agronomic traits. NuSun oil production was nearly 171,000 tonnes in the crop year of 2001. This volume was reached only four years after the first commercial crushing in 1998. The oil has all the appeal of traditional sunflower oil, while at the same time it is more stable, does not require hydrogenation for industrial frying application, and will be sold as commodity oil. A worldwide expansion of the NuSun variety could perhaps provide the boost that the sunflower oil industry needs today. 

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C4H8O, CH3COCH2CH3. Colourless liquid with a pleasant odour, b.p. 80°C. It occurs with propanone in the products of the destructive distillation of wood. Manufactured by the liquid or vapour phase dehydrogenation of 2-butanol over a catalyst. Used as a solvent, particularly for vinyl and acrylic resins, and for nitrocellulose and cellulose acetate, also for the dewaxing of lubricating oils. U.S. production 1978 300 000 tonnes. 

During the production of mineral oils from vacuum distillates, one of the process steps, dewaxing , removes the high melting point materials in order to improve the oil s pour point. Dewaixing produces paraffins and waxes, the first coming from light distillates, and the second from medium or heavy distillates. 

Although lubricant base stocks have been subjected to dewaxing processes, they still contain large amounts of paraffins that result in a high pour point for the oil. In the paragraph on the cold behavior of diesel fuels, additives were mentioned that modify the paraffin crystalline system and oppose the precipitation of solids. 

With regard to the unconverted residue, the VI after dewaxing is 120 to 135 and the BMCI is between 10 and 15, which makes it an excellent feed for steam cracking units. 

Catalytic dewaxing Catalytic hydrogenation Catalytic properties Catalytic pyrolysis Catalytic reduction Catalytic reforming... 

Centrifugal expanders Centrifugalpumps Centrifugal separation Centrifugal sucrose Centnfugation Centrifuge dewaxing... 

Dewaxing, catalytic Dewaxing process Dewaxing processes Dexamethasone... 

Urea has the remarkable property of forming crystalline complexes or adducts with straight-chain organic compounds. These crystalline complexes consist of a hoUow channel, formed by the crystallized urea molecules, in which the hydrocarbon is completely occluded. Such compounds are known as clathrates. The type of hydrocarbon occluded, on the basis of its chain length, is determined by the temperature at which the clathrate is formed. This property of urea clathrates is widely used in the petroleum-refining industry for the production of jet aviation fuels (see Aviation and other gas-TURBINE fuels) and for dewaxing of lubricant oils (see also Petroleum, refinery processes). The clathrates are broken down by simply dissolving urea in water or in alcohol. 

Lubricants. Petroleum lubricants continue to be the mainstay for automotive, industrial, and process lubricants. Synthetic oils are used extensively in industry and for jet engines they, of course, are made from hydrocarbons. Since the viscosity index (a measure of the viscosity behavior of a lubricant with change in temperature) of lube oil fractions from different cmdes may vary from +140 to as low as —300, additional refining steps are needed. To improve the viscosity index (VI), lube oil fractions are subjected to solvent extraction, solvent dewaxing, solvent deasphalting, and hydrogenation. Furthermore, automotive lube oils typically contain about 12—14% additives. These additives maybe oxidation inhibitors to prevent formation of gum and varnish, corrosion inhibitors, or detergent dispersants, and viscosity index improvers. The United States consumption of lubricants is shown in Table 7. 

MEK is also used iu solvent-based adhesives, iu printing ink formulations, as a solvent iu magnetic tape manufacture, and is the most common solvent used iu dewaxing lubricating oils. Of all these appHcations only an increasing consumption of magnetic tapes is likely to grow ia methyl ethyl ketone use. 

In shape-selective catalysis, the pore size of the zeoHte is important. For example, the ZSM-5 framework contains 10-membered rings with 0.6-nm pore size. This material is used in xylene isomerization, ethylbenzene synthesis, dewaxing of lubricatius oils and light fuel oil, ie, diesel and jet fuel, and the conversion of methanol to Hquid hydrocarbon fuels (21). 

Catalysis. As of mid-1995, zeoHte-based catalysts are employed in catalytic cracking, hydrocracking, isomerization of paraffins and substituted aromatics, disproportionation and alkylation of aromatics, dewaxing of distillate fuels and lube basestocks, and in a process for converting methanol to hydrocarbons (54). 

Solvent Treatment. Solvent processes can be divided into two main categories, solvent extraction and solvent dewaxing. The solvent used in the extraction processes include propane and cresyHc acid, 2,2 -dichlorodiethyl ether, phenol (qv), furfural, sulfur dioxide, benzene, and nitrobenzene. In the dewaxing process (28), the principal solvents are benzene, methyl ethyl ketone, methyl isobutyl ketone, propane, petroleum naphtha, ethylene dichloride, methylene chloride, sulfur dioxide, and iV-methylpyrroHdinone. 

Insofar as they are used to purify other products, several processes used in the refinery fall under the classification of dewaxing processes however, such processes must also be classified as wax production processes (2). Most commercial dewaxing processes utilize solvent dilution, chilling to crystallize the wax, and filtration (28). The MEK process (methyl ethyl ketone—toluene solvent) is widely used. Wax crystals are formed by chilling through the walls of scraped surface chillers, and wax is separated from the resultant wax—oil—solvent slurry by using fliUy enclosed rotary vacuum filters. 

Solvents used for dewaxing are naphtha, propane, sulfur dioxide, acetone—benzene, trichloroethylene, ethylenedichloride—benzene (Barisol), methyl ethyl ketone—benzene (benzol), methyl -butyl ketone, and methyl / -propyl ketone. Other solvents in commercial use for dewaxing include /V-methylpyrrolidinone, MEK—MIBK (methyl isobutyl ketone), dichloroethane—methylene dichloride, and propfyene—acetone. 

On the other hand, intermediate paraffin distillates contain paraffin waxes and waxes intermediate in properties between paraffin and microwaxes. Thus, the solvent dewaxing process produces three different slack waxes depending on whether light, intermediate, or heavy paraffin distillate is processed. The slack wax from heavy paraffin distillate may be sold as dark raw wax, the wax from intermediate paraffin distillate as pale raw wax. The latter is treated with lye and clay to remove odor and improve color. 

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). 

Another method of separating petrolatum from residua is by centrifuge dewaxing. In this process, the reduced cmde oil is dissolved in naphtha and chilled to —18° C or lower, which causes the wax to separate. The mixture is then fed to a battery of centrifuges where the wax is separated from the Hquid. However, the centrifuge method has been largely displaced by solvent dewaxing methods as well as more modem methods of wax removal. Similar use is... 

Sources. Methyl ethyl ketone (MEK) is used in some r neries as a solvent in lube oil dewaxing. Its extremely volatile characteristic makes fugitive emissions its primary source of releases to the environment. 

Lubricating Oil Manufacture This consists of solvent deasphalting, phenol treating, and solvent dewaxing. In dewaxing, waxy lube is diluted with a solvent such as propane or methyl ethyl ketone (MEK), and cooled to crystallize the wax which is then removed by filtration. 

Wax Manufacture A waxy distillate cut from crude or the wax byproduct from lube oil dewaxing is first deoiled. Resulting low oil content wax is hydrofmed for color improvement and fractionated into appropriate melting point grades. 

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