In a distillation process such as vacuum distillation what forms at room temperatures is a unit contained of quantities of wax. The removal of this wax is necessary for the base stock to have desired low temperature properties. 1 Two processes to separate the wax from the waxy petroleum fraction is solvent dewaxing and catalytic dewaxing processes. These processes help to prevent corrosion, protect catalyst in subsequent processes and to improve finished products by removing unsaturated, aromatic hydrocarbons from lubricant and grease stocks.2 In solvent dewaxing a solvent such as toluene or methyl ethyl ketone are used.2 These agents dissolves little wax at low temperatures and acts as a wax predicating agent. When the solvents are mixed with the product stream, the waxy oil and solvent are chilled.2 A filter is then used which removes the predicated oil.2 This process is much different however to the additional dewaxing method of catalytic dewaxing. This process is completed by selectively hydrodewaxing paraffinic wax contained in liquid petroleum.3 This process starts with a first serial catalyst bed under adiabatic cracking temperatures conditions, while controlling exothermal heat of reation.3 This then produced lighter olefin components, recovering partially hydrodewaxed liquid petroleum from a bottom portion of the first serial catalyst bed.3 The partially hydrocracked liquid petroleum is then further reacted to effect endothermic hydrodewaxing concurrently with exothermic hydrogen transfer causing dewaxing, hydrogenation and cyclization in the presence of hydrogen under adiabatic temperature conditions.3 This finishing process then allows for uniform hydro-dewaxing conditions and the obtaining of a high quality petroleum lubricant product.3 These two processes use very different techniques to finish the product, however complete the same goal of dewaxing the product steam, allows for a more desirable product which can operate under colder temperatures, increasing it usability and range of operation. It also helps to improve a lubricant oil low pour point by decreasing the temperature at which wax forms in the products and by improving its oxidation stability.3
- http://www.bechtel.com/3868
- http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CFgQFjAF&url=http%3A%2F%2Fkvbchemicalengg.com%2Fpdf%2FSOLVENT%2520EXTRACTION%2520AND%2520DEWAXING.pdf&ei=SrSlU6e8FISeyATKpoCYCg&usg=AFQjCNHfYhHhEZBls3BktgCc3MynD88vmQ&sig2=d9yAHalTi0rRCLfM9fhFvw&bvm=bv.69411363,d.b2k
- http://www.google.com/patents/US5246568