Dewaxing is a separation process that takes advantage of deasphalted oil (DAO) and heavy vacuum gas oil (HVGO) from the vacuum distillation tower as feedstocks in producing lubricating oil base stock and, to some extent, distillate fuels such as gasoline. The goal of dewaxing is to remove hydrocarbons that would potentially increase the pour point of the lube oil base stock to a desirable range of -9^o – 14^o F. There is two different processes that result in this marketable lube oil: solvent dewaxing and catalytic dewaxing.

Solvent dewaxing is a physical process that uses refrigeration, scraping techniques, and methyl ethyl ketone (MEK) and propane solvents to separate the feedstocks and produce a valuable product. The MEK solvent and the deasphalted oil combine in the first phase and go through a series of refrigeration processes at different temperatures to form wax crystals, which are then transported to a rotary filter where a filter cloth separates the wax from the oil + solvent. The wax goes on to produce candle wax and petroleum jelly while the dewaxed oil purifies into the desirable lube oil base stock. Issues that arise from this process come from choosing which type of solvents to use. Most refineries use MEK even though propane can be used from multiple aspects of the process, save money, increase filtration rates.

Catalytic dewaxing is a chemical process that, by nature, is actually a conversion process. It uses catalytic cracking of n-paraffins, but since the purpose is to remove wax, it is classified as a separation process. There is not much detail to this process although it does use hydrogen addition to prevent coking. It is obviously the best way to dewax the feedstocks because it results in a product with lower pour points, high yield, and high stability. Catalytic dewaxing also allows for the production of light distillates such as gasoline since the n-paraffins are cracking.