Asphaltenes properties and chemical composition.
Asphaltenes – amorphous hard brittle substance of a dark brown or black in color. Represent hydrocarbon compounds. Are components of oil and bitumen.
The chemical composition of asphaltenes
The physical properties of asphaltenes
Chemical properties of asphaltenes
Asphaltenes:
Asphaltenes – amorphous hard brittle substance of a dark brown or black in color.
Represent hydrocarbon compounds.
When heated do not melt, and pass into the plastic state (~ 300 ° C), at higher temperatures (over 300 ° C) decomposes with the formation of gas, liquids and solid residue – coke.
Asphaltenes tend to associate with the formation of supramolecular structures, which is a stack of flat molecules with distance between them almost 0.40 nm, so their molecular weight can vary significantly from 1000 to 5000 g/mol.
Asphaltenes are components of crude oils and bitumen. The asphaltene content in crude oils ranges from 1% to 20%. Petroleum resin, along with asphaltenes, are also components of crude oil. From the resins and asphaltenes are more – 2-3 times a molecular weight.
The chemical composition of asphaltenes:
The composition of the asphaltene molecules consists of fragments heterocyclic, alicyclic, condensed hydrocarbons, consisting of 5-8 cycles. Large fragments of the molecules are linked by bridges containing methylene groups and heteroatoms. The most typical alternate in cycles – alkyl with a small number of carbon atoms and functional groups such as carbonyl, carboxyl, mercaptopropyl.
Asphaltenes and resins contain the main part of the trace elements of oil, including almost all metals.
The following table shows the elemental composition of asphaltenes:
| The name of a chemical element: | %% content |
| Carbon, With | 80-86 |
| Hydrogen, N | 7-9 |
| Sulfur, S | 0,5-9 |
| Nitrogen, N | to 2 |
| Oxygen, O | 2-10 |
| Vanadium and Nickel, V + Ni | Of 0.01-0.2 |
| and other (including iron Fe, calcium Ca, magnesium Mg, copper Cu) |
The physical properties of asphaltenes:
| Parameter name: | Value: |
| Density, g/cm3 | 1,1 |
| Density, kg/m3 | 1100 |
| Aggregate state | hard brittle substance |
| Color | dark brown or black |
| Molecular weight, g/mol | 1000-5000 |
| Softening temperature, °C | about 300 |
Chemical properties of asphaltenes:
Unlike resins have a lower solubility.
Soluble in aromatic hydrocarbons, benzene, toluene, CS2, CHCl3, CCl4, insoluble in paraffin hydrocarbons, alcohol, ether, acetone.
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