Fuel components, either from straight-run streams or from conversion units, are unstable for many reasons. The presence of unsaturated hydrocarbons and the absence of the natural anti-oxidant species are the main causes of fuel instability.
Unsaturated hydrocarbons are susceptible to forming free radicals in the presence of oxygen or air. Sometimes, heat can also initiate the free radical reaction. Once free radicals are formed, the reaction will propagate until the supply of unsaturated compounds runs out. This will cause high molecular weight, gummy compounds formed in solution. Gasoline with high olefins levels will fail the induction period test.
Refineries commonly use hydrogen to stabilize components by saturating the unsaturated hydrocarbons. This option may be more expensive due to the cost of hydrogen production. Building hydrogen production facilities is also very capital intensive.
Contrary to conventional wisdom, hydrogenation processes can also destabilize fuel components. Ultra-Low Sulfur Diesel (ULSD) is a good example. As sulfur-containing compounds are natural anti-oxidants, removal of sulfur by severe hydrofining depletes these compounds and the resulting ULSD becomes unstable due to the ease of forming peroxides.
Use of antioxidants is often more cost-effective. Cestoil Chemical offers a variety of antioxidants for use as free radical scavengers in fuels. We can also tailor products for specific applications.