What are the structural components of petroleum?
Hydrocarbon Compounds:
(1) Alkanes: Saturated hydrocarbons in which carbon atoms in the molecule are connected by single bonds, such as methane, ethane, propane, etc.
(2) Naphthenes: Saturated hydrocarbons in which carbon atoms form a cyclic structure, such as cyclohexane.
(3) Aromatic Hydrocarbons: Compounds containing at least one benzene ring structure, such as benzene, toluene, xylene, etc.
Compounds Containing Sulfur, Nitrogen, and Oxygen:
(1) Sulfur-containing Compounds: Such as mercaptans, thioethers, disulfides, and thiophenes. These compounds need to be removed during the refining process because they can affect the quality of fuels and cause environmental pollution.
(2) Oxygen-containing Compounds: Such as naphthenic acids and phenols (mainly phenol), they can also affect the stability and corrosiveness of products.
(3) Nitrogen-containing Compounds: Such as pyridine, pyrrole, quinoline, and amines. These substances need to be controlled during petroleum processing because they can affect the activity of catalysts.
Metal Elements: Petroleum also contains trace amounts of metals such as nickel, vanadium, iron, antimony, etc. These metals usually exist in the form of compounds. Although the content is very low, they have a potential toxic effect on the catalysts in the oil refining process.
The chemical formula of petroleum cannot be represented by a single molecular formula because it is a mixture composed of a variety of different molecules, and the proportion of its components varies greatly depending on the origin. However, alkanes roughly represented as CnH2n+2 can be used as a simplified model of typical components, where n represents the number of carbon atoms. But in fact, the compounds contained in petroleum are much more complex than this, covering a variety of types from low molecular weight gases to high molecular weight solid asphaltenes.
What are the constituent components of petroleum?
Hydrocarbon compounds are the main components of petroleum, including:
Alkanes: Straight-chain or branched-chain saturated hydrocarbons, such as methane, ethane, propane, butane, etc., are the main components of natural gas and liquefied petroleum gas.
Naphthenes: Hydrocarbons with a cyclic structure, present in a variety of petroleum products such as gasoline and diesel.
Aromatic Hydrocarbons: Compounds with one or more benzene ring structures, such as benzene, toluene, xylene, etc., are often used in the production of plastics, synthetic fibers, and solvents. Non-hydrocarbon compounds, although present in a smaller amount, also account for a certain proportion in petroleum, including:
Sulfur-containing Compounds: Such as mercaptans, thioethers, disulfides, and thiophenes, etc. These compounds need to be removed during the refining process because they may cause corrosion and affect the quality of petroleum products.
Nitrogen-containing Compounds: Such as pyridine, pyrrole, quinoline, and amines, which also have an impact on the refining process and product quality.
Oxygen-containing Compounds: Such as naphthenic acids and phenols (mainly phenol), and their presence will affect the processing and usage characteristics of petroleum.
Metal Impurities: Such as trace elements like iron, nickel, vanadium, etc. These may be present in relatively large amounts in some petroleum and have a potential corrosive effect on oil refining equipment.
The composition of petroleum varies according to the geological conditions of its source area, which also explains why petroleum from different regions differs in processing characteristics and product distribution. The complexity of petroleum requires it to be converted into various useful fuels and chemical raw materials through processes such as fractional distillation, refining, and chemical treatment during the refining process.
The Physical Properties of Petroleum
Color: The color of petroleum varies greatly, ranging from light yellow to dark brown. This mainly depends on the content of resins and asphaltenes inside. The higher the content, the darker the color. Sometimes, colorless and transparent condensate oil also exists.
Density: The density of petroleum is generally between 0.75-1.0 g/cm³. Under standard conditions (20℃, 0.101 mpa), the mass of crude oil per cubic meter is the density of crude oil, generally between 0.79-0.92 g/cm³.
Viscosity: The viscosity of petroleum ranges from a few millipascal-seconds to several thousand millipascal-seconds. The petroleum extracted from the underground before refining is called crude oil. The viscosity of crude oil measured under formation conditions is called formation viscosity.
Pour Point: The pour point of petroleum does not have a fixed value, but generally, the temperature at which crude oil loses its fluidity or starts to solidify is called the pour point. Crude oil with less wax content and lower content of heavy components has a lower pour point, which is beneficial for exploitation and gathering and transportation. Crude oil with a pour point above 40℃ is called gelled oil.
Solubility: Petroleum is insoluble in water but soluble in a variety of organic solvents and can also be miscible with natural gas.
Conductivity: Petroleum is a poor conductor and has a high resistivity.
Fluorescence: Petroleum can emit fluorescence under ultraviolet light irradiation.
Flammability: Petroleum is flammable.
