Before history, people have discovered and used oil. Archaeologists found traces of petroleum asphalt mortar more than 5,000 years ago in ancient buildings on both sides of the Euphrates River in Iraq today.
"It is the ancient word" burn ". That is to say, as early as 1 century ago, China had discovered that there was oil on the water surface, which could be burned.
But for a long time, oil has only been directly used as fuel and lighting, which will emit thick black smoke and produce a strong pungent smell.
19 in the 1950s, Benjamin Silliman Jr., a chemistry professor at Yale University in the United States, in the early 1960s. , 18 16- 1855) studied and analyzed the composition of petroleum, and determined that petroleum is a mixture of various hydrocarbons.
The hydrocarbon sound tοng is the syncopation of carbon (tàn) and hydrogen (qοng), which indicates that it is a compound of carbon and hydrogen. This is a chemical term with China characteristics created by a chemist in China.
Methane (CH4), ethylene (C2H4) and acetylene (C2H2) are the three simplest hydrocarbons, and they are all chain-like hydrocarbons because they have chain-like structures to distinguish them from cyclic hydrocarbons with cyclic structures. Their names also have the characteristics of China.
A, B, C, D, E, Ji, G, Xin, Ren and Gui are called heavenly stems, also called ten stems. Heavenly stems and earthly branches (Zi, Chou, Yin ...) has been used repeatedly since ancient times to indicate the order of year, month, day and time. Chinese chemists use it to indicate the number of carbon atoms in chain hydrocarbons. "Alkane" means "complete", carbon is tetravalent, 1 carbon atom is combined with 4 hydrogen atoms; "alkene" means "scarcity" and "alkyne" means "lack", all of which are combustible with "fire".
Chain hydrocarbons can be divided into straight chain hydrocarbons and branched chain hydrocarbons. For example, n-heptane represents an alkane with 7 carbon atoms, which is a straight chain hydrocarbon with the molecular structure:
Isooctane is an isomer of octane, and octane refers to an alkane containing 8 carbon atoms. Their molecular formulas are C8H 18, but their structural formulas are different. Isooctane is a branched hydrocarbon, also known as 2,2,4-trimethylpentane, which means that it is an alkane containing five carbon atoms, which are numbered 1, 2,3,4,5 respectively from left to right, and three methyl groups containing 1 carbon atoms and three hydrogen atoms are connected at positions 2, 2 and 4.
Carbon atoms in molecular structures such as benzene (C6H6) and toluene (C6H5CH3) are connected to form rings, so they are also called cyclic hydrocarbons:
Organic compounds are divided into chain compounds and cyclic compounds according to their molecular structures. Chain compounds are also called aliphatic compounds. Cyclic compounds can be divided into three categories: the first category is aromatic compounds (27), the second category is heterocyclic compounds (27), and the third category is alicyclic compounds. For example, cyclohexane (C6H 12) is a saturated compound with no double bond or triple bond in its molecular structure. Therefore, cyclic hydrocarbons can be divided into aromatic (aromatic) cyclic hydrocarbons and aliphatic (aliphatic) cyclic hydrocarbons.
Hydrocarbons can be divided into saturated hydrocarbons and unsaturated hydrocarbons. Alkanes are saturated hydrocarbons with the general formula CnH2n+2. Olefins and alkynes are unsaturated hydrocarbons, and their general formulas are CnH2n and CnHn respectively.
Petroleum is a mixture of various hydrocarbons, that is, petroleum contains both chain hydrocarbons and cyclic hydrocarbons; It contains straight chain hydrocarbons and branched chain hydrocarbons; It contains both alicyclic hydrocarbons and aromatic hydrocarbons; It contains saturated hydrocarbon and unsaturated hydrocarbon.
1859, Edwin L.Drake, an American, drilled oil for the first time in Titusville, Pennsylvania, USA, and fractionated the produced oil. He called the fraction of hydrocarbons with distillation temperature of 40~60℃ and containing 5~6 carbon atoms naphtha and used it as a solvent. The distillation temperature is 55~200℃, and the fraction of hydrocarbons containing 6~ 12 carbon atoms is called gasoline, which has not been used yet. The distillation temperature is 195~300℃, and the fraction of hydrocarbons containing 12~ 16 carbon atoms is called kerosene for lighting. The distillation temperature is 285~350℃, and the fraction of hydrocarbons containing 15~ 18 carbon atoms is called diesel oil, which is used as engine fuel. When the distillation temperature is above 350℃, the fraction containing more than 18 carbon atoms is called heavy oil and used as lubricant. The remaining asphalt is used to cover the roof to prevent water.
Department of Chemistry, Nanjing University. Organic chemistry (I). Beijing: People's Education Press, 1978.
Lighting with petroleum fractions will still produce strong pungent odor, because sulfur contained in petroleum will produce sulfur dioxide (SO2) gas when it is burned. About 1887, standard oil company) Chemist Flasch (1851-kloc-0/914) used metal oxides such as copper, lead and iron to convert sulfur in oil into sulfide precipitate, and then recovered and converted into oxide. Later, he used concentrated sulfuric acid as oxidant to oxidize some smelly sulfides contained in petroleum into sulfonic acid (R-SO3H) to form acid residue, which was separated by centrifugal separation or static method. This can be considered as the first round of petrochemical processing.
But until the end of 19, gasoline was not fully utilized because of its low ignition point and easy volatilization. It not only caught fire, but also burned to pieces and even exploded. It was regarded as a dangerous "waste" and I didn't know how to deal with it.
By the end of 19, internal combustion engines and automobiles came out one after another. Compared with the internal combustion engine, the steam engine boils the water in the boiler to generate steam, and then introduces the steam into the cylinder to push the piston to do work, so it can be called an "external combustion engine". The internal combustion engine burns the fuel in the cylinder, so that the gas produced by combustion pushes the piston to do work. Internal combustion engines need liquid fuel that is easy to burn, and gasoline just meets the requirements. When the internal combustion engine is put into the car, the price of gasoline will go up immediately.
However, the problem has arisen again. When the mixture of gasoline vapor and air burns in the cylinder, part of gasoline often explodes before ignition, resulting in knocking. Knocking not only wastes energy, but also damages the cylinder of internal combustion engine. Through various tests, it is obvious that the deflagration degree is related to the composition of gasoline used. Generally speaking, straight-chain alkanes produce the greatest degree of knocking when burning, followed by olefins and alicyclic hydrocarbons, and aromatic hydrocarbons and branched alkanes produce the least degree of knocking. Among gasoline components containing 7~8 carbon atoms, n-heptane has the greatest knock degree, while isooctane (2,2,4-trimethylpentane) basically does not produce knock.
The octane number of gasoline is an index to measure the knock degree of gasoline. The octane number is based on n-heptane and isooctane, with n-heptane having an octane number of 0 and isooctane having an octane number of 100. In the mixture of n-heptane and isooctane, the volume fraction of isooctane is called the octane number of this mixture, which is also commonly known as gasoline brand.
The octane number or gasoline brand of various gasoline is obtained by comparing them with the degree of knocking phenomenon when burning the above mixture. For example, the octane number of a gasoline is 80 or 80 # gasoline, which means that the knocking phenomenon produced when this gasoline is burned in a standard single-cylinder internal combustion engine is the same as that produced when a mixture of 20% (volume fraction) n-heptane and 80% isooctane is burned in the same cylinder. Ordinary gasoline is not a simple mixture of n-heptane and isooctane, so octane number can only indicate its knock degree, but not its isooctane content.
Gasoline obtained by petroleum fractionation is different from crude oil, and its octane number is about 20~70, which can not meet the requirements of automobile and aircraft fuel.
Shortly after the First World War, the laboratory of General Gasoline Company of the United States screened many substances, trying to find a substance and add it to gasoline to reduce the knock degree of gasoline combustion. American industrial chemists Midgley (1889- 1944) and Boyd (T.A.) found that tetraethyl lead (Pb(C2H5)4) was put into use on 192 1, which can reduce the knock of gasoline combustion and is called an antiknock agent. However, it was later found that tetraethyl lead would generate lead oxide after burning in the cylinder, which accumulated in the cylinder and caused obstacles. Then dibromoethane ((CH2)2Br2) and dichloroethane ((CH2)2Cl2) are added, which can react with tetraethyl lead during combustion and discharge the generated substances together.
The exhaust gas contains lead bromide (PbBr2), which will decompose under sunlight, producing lead and bromine, polluting the air and environment, which makes people who manufacture and use tetraethyl lead very confused. The United States banned leaded gasoline from 1995. China and Beijing also banned the use of leaded gasoline from 1998 to 1, and then banned it nationwide.
Adding antiknock agent to gasoline can be considered as the second round of petrochemical processing.
The third round is the cracking and cracking of oil.
The cracking and cracking of petroleum is to decompose hydrocarbons containing more carbon atoms, such as diesel oil or other high-boiling fractions higher than gasoline, into hydrocarbons containing less carbon atoms by heating. During the heating process, these molecules with more carbon atoms not only produce molecules with less carbon atoms by carbon chain breakage, but also undergo dehydrogenation, polymerization, cyclization, isomerization and other reactions, so that the products contain a considerable number of olefins, aromatic hydrocarbons and branched alkanes. These components have high octane number, so the thermal decomposition of petroleum not only increases the output of gasoline, but also can obtain better quality gasoline and produce it on demand. Generally speaking, gasoline obtained from petroleum fractionation is called straight-run gasoline. Straight-run gasoline can not meet the requirements of modern industrial development in quality and quantity, because the yield of straight-run gasoline is only 16% of the quality of crude oil, and its octane number is generally between 20 and 70. Cracking petroleum products can not only increase gasoline production by more than 3 times for crude oil with the same quality, but also enhance the antiknock performance, so the cracking processing of petroleum products has developed rapidly since the beginning of the 20th century.
The difference between petroleum cracking and cracking lies in the reaction temperature. The cracking temperature generally does not exceed 500℃, and the hydrocarbons obtained are mainly liquid, and some gases are also produced. The cracking temperature is generally above 700℃ to 1000℃ or higher, and a large number of gas products and some liquid products are obtained.
This was developed by many scientific and technological personnel.
American chemist William meriam Burton (1865- 1954) began to study petroleum cracking from 1909. At first, it was carried out in gas phase under normal pressure, and the output was very low. He tried catalysts such as aluminum chloride, and the effect was also poor. Two years later, the research was carried out in liquid phase at 350~450℃ and 5 atmospheres. 19 15 gasoline prices fell. This method contributed to the gasoline supply in the United States during World War I, and won the Parkin Medal of American Chemical Industry Association at 192 1.
Charles Mosley. Chemistry and the First Great Gasoline Shortage. Journal of Chemical Education,1986,57 (4).
Russian chemist Zarinski (иклймитиивичзлиннн)
Houdry (1892- 1962), an American French mechanical engineer, used silica-lead oxide as a catalyst to crack oil. He found that the carbon particles produced in the cracking process covered the surface of the catalyst, which reduced the activity of the catalyst, so he introduced air into the reactor to make the carbon particles burn, which not only removed the carbon particles, but also became the heat source needed for the reaction process.
Catalytic Cracking and World War II Aviation Gasoline, Journal of Chemical Education,1984,61(8).
193 1 year Russian-American chemist Ipatiyev was the first to use the high-temperature catalytic cracking of petroleum.
With the development of petroleum cracking and cracking, petroleum processing technologies such as reforming and alkylation have emerged.
Reforming is the rearrangement of linear hydrocarbons into branched hydrocarbons and cyclic hydrocarbons, which requires platinum or rhenium catalyst, also known as platinum reforming, to improve the octane number of products.
Alkylation is the addition of alkyl groups to hydrocarbon molecules to increase the octane number.