What are the uses of fractional derivatives

The composition of petroleum

Petroleum is mainly a mixture of many hydrocarbons. The most common hydrocarbons are linear or branched alkanes (paraffins), cycloalkanes (naphthenes) and aromatics. Every crude oil has a special chemical composition depending on where it was found, which also determines the physical properties such as color and viscosity.

The fractional distillation of petroleum

The increase in the boiling temperature in experiment 1 shows that crude oil is a mixture of many substances. The boiling temperatures of the individual crude oil components are between 30 and 350 ° C, a strong indication that it consists of many different chemical compounds. In the experiment, they were collected in glass vessels that were presented at different temperatures. Examination of the samples obtained shows that they are mixtures of compounds with boiling points that are close together. Several ingredients that have a similar boiling point are grouped together in what is known as a fraction. These individual fractions can be separated by distillation, which is called fractional distillation.

Petroleum - a mixture of many substances

Crude oils contain nearly 90% carbon, around 10% hydrogen, and small amounts of oxygen, sulfur, and nitrogen. So crude oils are a mixture of different hydrocarbons. Alkanes are the main constituent of crude oil. They are either chain-shaped (unbranched or branched paraffins) or ring-shaped, such as the cycloalkanes (cyclohexane, C.6H12). An important consideration is the presence of reef in crude oil, since the harmful sulfur dioxide is produced when sulfur-containing petroleum products are burned. An effective desulphurisation of gases and fuels is active environmental protection, because it greatly reduces the emission of air pollutants. Crude oil from the African continent has a sulfur content of 0.12 to 0.37% by weight, so it is quite low in sulfur. The oil from the Middle East has a relatively high sulfur content of 4.5% by weight.

The decomposition of petroleum in the refinery

In the oil refineries with their up to 50m high distillation or fractionation towers, the hydrocarbons contained are separated.

To do this, the crude oil is first heated to 350 - 400 ° C in a tube furnace and the resulting mixture of vapor and liquid is fed into the distillation tower. Such towers have numerous floors, which consist of so-called bell bottoms - plates with pipe sockets through which the steam rises to the top. Since the passages are covered with "bells", the steam has to pass through the distillate collected on the plates.

The vapor-liquid mixture from the tube furnace is fed into the fractionation tower from below. Higher-boiling, long-chain liquid hydrocarbons accumulate on the lower bubble-cap trays and lower-boiling, short-chain liquid hydrocarbons higher up on the bubble-cap trays. Hydrocarbons with a boiling point below + 30 ° C leave the fractionation tower as gases. Gaseous components have one to four carbon atoms, such as the alkanes methane (CH4) to butane (C.4H10). Most of them are already removed at the drilling site.

Hydrocarbons with five to eleven carbon atoms are called petrol. They are mostly used as fuel for cars. Around 40% of crude oil is processed into such fuels.

Hydrocarbons with eleven to fourteen carbon atoms are called kerosene. They are used as fuel for aircraft. The processing of crude oil produces more kerosene than is needed, so researchers developed a process to break down kerosene into gasoline. Kerosene boils in a range between 150 and 240 ° C.

The next higher boiling fraction is gas oil. Diesel oil, kerosene and, after cracking, heating oil are extracted from it. They have boiling points up to around 350 ° C. The heavy oils, the next fraction, have between 20 and 35 carbon atoms per chain. The distillation described so far takes place at atmospheric pressure, which is why it is called atmospheric distillation. Some of the heaviest constituents of the crude oil are further separated after the atmospheric distillation. However, since the large molecules would break open when heated, the residue is distilled under reduced pressure ("vacuum distillation"). Different lubricating oils are obtained. Chains with 36 or more carbon atoms are called bitumen. It is used as asphalt and tar in road construction and is a residue from vacuum distillation.