Blog 5

Write a post comparing the solvent dewaxing and catalytic dewaxing processes.

Dewaxing is a process used to remove waxes from oil refinery feed stocks. Once the wax is removed it can be sold as a bi-product for things such as candles and other forms of waxes. The feedstock after being dewaxed can be used as various lubricating oils and other distillate fuels such as gasoline. Dewaxing is performed on a feedstock through two different processes. One is a physical process that uses a solvent and is known as solvent dewaxing. The other is a chemical process and uses catalytic cracking and is known as catalytic dewaxing.

In solvent dewaxing a solvent is added to the feedstock and the mixture is then chilled to a desirable temperature and then proceeds through a rotary filter which separates the solid wax from the feedstock. This is because of the components varying freezing temperatures which allows for seperation to occur. Solvent dewaxing primarily uses two types of solvents being propane and methyl ethyl ketone, also known as MEK. MEK is more commonly used as a solvent due to its minor variance in filtration and pour point temperatures along with its chilling rate characteristics.

Catalytic dewaxing involves the breaking and creation of bonds. It is known as a conversion process of n-paraffins.  This form of dewaxing is able to break apart and actually remove long chain n-paraffins. Catalytic dewaxing uses sieve catalysts to filter with a pore opening size very small so that i-paraffins can be captured and filtered out and only n-paraffins shall be able to pass through. This can also help to lower the feedstock’s pour point value.  Catalytic dewaxing will produce a lube base stock with a lower pour point and a higher yield than that of a feedstock that underwent solvent dewaxing. Catalytic dewaxing is a less expensive form of dewaxing, but both processes have their pros and cons.