As well as its constituents, bitumen is the residue of crude oil. The only difference is the percentage of the components in comparison to crude oil. This is because the crude oil is refining process is only a physical separation process because of difference in boiling point of the components of crude oil. As the high temperatures can cause damage and converts the structure of crude oil, the second step of crude oil distillation carried out at low pressure and temperature. In this process, the probability of chemical reactions is very low.
1. Paraffin: linear or branched saturated hydrocarbons without ring structure.
2. Naphthenic: one or more branches of saturated hydrocarbons with one or more subsidiary branches of paraffin which are called alicylic hydrocarbons.
3. Aromatics: hydrocarbons with one or more aromatic ring of benzene, naphthalene, and phenanthrene which are connected to each other by naphthenic rings or paraffinic branches.
Typically found in nature, hydrocarbons mostly are made from paraffin compounds. If they have some aromatics, they classified as conventional crude oil. If the mixture is the same for all three categories, they are called heavy oil. If extracted hydrocarbon is mainly composed of naphthalene compounds, it is called tar.
About crude oil, the materials consist of four components: Saturated compounds, Aromatics, Resins, Asphaltene (SARA). As from the name of these materials is expected, saturates include saturated hydrocarbons and aromatics have simple rings. The resin s and asphaltene situation is somewhat different. These two materials have similar chemical structures which resins can convert to asphaltene. In fact, depending on percentage of materials in crude oil, it is defined and indisputably, it affects the type of bitumen. The composition is important because it affects bitumen material adhesion to aggregates and features of final asphalt. Bitumen is a hydrocarbon material derived from crude oil which consists of 82-88% carbon, 8-11% hydrogen, 0-6% sulfur, 0-1/5% oxygen and 0-1% nitrogen. The following methods can be used to separate components of bitumen:
1. Extraction by solvents
2. Absorption on small solid particles and smoothen the non-absorbed parts
4. Molecular distillation with one of the foregoing methods