Petroleum bitumen is a solid or liquid organic material made from a mixture of hydrocarbons and their derivatives. The resulting products do not dissolve in water, but completely or partially dissolve in carbon disulfide, benzene and a number of organic solvents with a density of up to 1.50 g/cm3.
Elemental composition
Bitumen contains carbon, hydrogen, compounds and impurities of metals, including iron, nickel, vanadium, etc. The ratio of the elements is as follows (mass%):
Component composition
Petroleum bitumen is a dispersed system, i.e. it is formed from several phases that do not interact chemically with each other and practically do not mix. The dispersion medium is oils and resins, and the dispersed phase is asphaltenes.
The bulk of the substance is hybrid and therefore only groups with approximate uniformity of composition can be distinguished. The only compounds that can be isolated in almost pure form are paraffins.
So, the component composition of petroleum bitumen includes:
Asphaltenes
are high molecular weight petroleum compounds that are a product of polymerization, condensation and dehydrogenation of resins.
The substance is easily soluble in carbon disulfide and chloroform, but does not dissolve in acetone and alcohol. It heats up but does not dissolve in the sunlight.
The presence of asphaltenes in bitumen affects its softening temperature and hardness.
A partial transition to carbenes and carbides is possible when concentrated sulfuric acid is exposed to asphaltenes in a chloroform solution.
Carbenes
Carbenes are similar to asphaltenes both in composition and properties. The difference between carbenes is the increased carbon content in the composition and the high density.
The substance does not dissolve in carbon tetrachloride, while it dissolves in pyridine and carbon disulfide.
The content of carbenes in bitumen is extremely low and has a negative effect on some of its characteristics, which leads to an increase in viscosity and brittleness. Also, their increased content leads to a decrease in extensibility.
Carboids
are a specific group in the form of a solid substance similar to carbon black.
The substance is a cross-linked, three-dimensional polymer; it does not dissolve in any of the existing organic solvents. Carbides are irreversible particles with strong phase contacts, not capable of destruction to a molecular state under the influence of external factors, except for harsh methods of exposure to oil dispersed systems.
Carbides are practically absent in natural oils and asphalts, in factory asphalts can be observed in the form of traces. The presence of carbides in bitumen has a negative effect on performance, including reduced elasticity and increased brittleness.
Petroleum oils
are a product of processing of high-boiling petroleum fractions, which consist of a mixture of hydrocarbons: paraffin, naphthenic, etc. The presence of several groups of hydrocarbons with a heterogeneous composition leads to the fact that the effect on the properties of bitumen may differ.
In general, with an increased oil content, bitumen becomes more fluid and mobile. If we look at it in more detail, then the ratio of oils to asphaltenes has a significant role on the softening and the brittleness temperature. Maximum ductility is achieved at a ratio of 2:5.
Asphaltogenic acids
are a group of poly-naphthenic acids with a solid or highly viscous consistency. They look similar to neutral resins.
Asphaltogenic acids are easily soluble in chloroform and alcohol, and are difficult to dissolve in gasoline.
The presence of asphaltogenic acids protects the colloidal structure of bitumen. Since acids are the surfactant, they also have an effect on increasing the strength and enhancing the adhesion of bitumen to materials, for example, stone surfaces.
Resins
In bitumen are substances that are plastic at room temperature and occupy 20–40% by weight.
The substance is chemically unstable, therefore, with prolonged exposure to oxygen or other oxidizing mediums, the transition of resins to asphaltenes begins, and an irreversible change in the phase composition of bitumen can be observed — its aging.
Bitumen is dissoluble in benzene, chloroform, ether and petroleum oils.
The presence of resins in bitumen has a positive effect on its plasticity and bonding properties.
Elemental composition
Bitumen contains carbon, hydrogen, compounds and impurities of metals, including iron, nickel, vanadium, etc. The ratio of the elements is as follows (mass%):
- 80-85% carbon
- 8-11.5% hydrogen
- 0.5-7% sulfur
- 0.2-4% oxygen
- 0.2-0.5% nitrogen:
Component composition
Petroleum bitumen is a dispersed system, i.e. it is formed from several phases that do not interact chemically with each other and practically do not mix. The dispersion medium is oils and resins, and the dispersed phase is asphaltenes.
The bulk of the substance is hybrid and therefore only groups with approximate uniformity of composition can be distinguished. The only compounds that can be isolated in almost pure form are paraffins.
So, the component composition of petroleum bitumen includes:
- asphaltenes
- carbenes
- carbides
- petroleum oils
- asphaltogenic acids
- resins
Asphaltenes
are high molecular weight petroleum compounds that are a product of polymerization, condensation and dehydrogenation of resins.
The substance is easily soluble in carbon disulfide and chloroform, but does not dissolve in acetone and alcohol. It heats up but does not dissolve in the sunlight.
The presence of asphaltenes in bitumen affects its softening temperature and hardness.
A partial transition to carbenes and carbides is possible when concentrated sulfuric acid is exposed to asphaltenes in a chloroform solution.
Carbenes
Carbenes are similar to asphaltenes both in composition and properties. The difference between carbenes is the increased carbon content in the composition and the high density.
The substance does not dissolve in carbon tetrachloride, while it dissolves in pyridine and carbon disulfide.
The content of carbenes in bitumen is extremely low and has a negative effect on some of its characteristics, which leads to an increase in viscosity and brittleness. Also, their increased content leads to a decrease in extensibility.
Carboids
are a specific group in the form of a solid substance similar to carbon black.
The substance is a cross-linked, three-dimensional polymer; it does not dissolve in any of the existing organic solvents. Carbides are irreversible particles with strong phase contacts, not capable of destruction to a molecular state under the influence of external factors, except for harsh methods of exposure to oil dispersed systems.
Carbides are practically absent in natural oils and asphalts, in factory asphalts can be observed in the form of traces. The presence of carbides in bitumen has a negative effect on performance, including reduced elasticity and increased brittleness.
Petroleum oils
are a product of processing of high-boiling petroleum fractions, which consist of a mixture of hydrocarbons: paraffin, naphthenic, etc. The presence of several groups of hydrocarbons with a heterogeneous composition leads to the fact that the effect on the properties of bitumen may differ.
In general, with an increased oil content, bitumen becomes more fluid and mobile. If we look at it in more detail, then the ratio of oils to asphaltenes has a significant role on the softening and the brittleness temperature. Maximum ductility is achieved at a ratio of 2:5.
Asphaltogenic acids
are a group of poly-naphthenic acids with a solid or highly viscous consistency. They look similar to neutral resins.
Asphaltogenic acids are easily soluble in chloroform and alcohol, and are difficult to dissolve in gasoline.
The presence of asphaltogenic acids protects the colloidal structure of bitumen. Since acids are the surfactant, they also have an effect on increasing the strength and enhancing the adhesion of bitumen to materials, for example, stone surfaces.
Resins
In bitumen are substances that are plastic at room temperature and occupy 20–40% by weight.
The substance is chemically unstable, therefore, with prolonged exposure to oxygen or other oxidizing mediums, the transition of resins to asphaltenes begins, and an irreversible change in the phase composition of bitumen can be observed — its aging.
Bitumen is dissoluble in benzene, chloroform, ether and petroleum oils.
The presence of resins in bitumen has a positive effect on its plasticity and bonding properties.