A little information about crude oil

Every month thousands of barrels of crude oil make the long voyage from far flung extraction wells to the api refinery at Falconara Marittima on Italy’s east coast. 
Upon arrival at the refinery the crude oil undergoes a series of treatments which are collectively known as “refining” and form the basis for obtaining the many products which leave the gates and pier of the refinery. To name just a handful: LPG, petrol, diesel and bitumen.
The first and most important step in the refining process is primary distillation, a type of boiling, which is carried out in the largest column of the refinery and is known as topping.
What happens
Once inside the column, the lightest parts of the oil rush upwards in the form of steam. They are then followed by the heavier elements which can’t make their way up the entire column, so only reach certain heights. Then there is a part of the oil, maybe 50%, that is so heavy that it simply falls directly to the bottom of the topping unit. And so, at the top of the column gases and lighter composites gather, and these are used both as combustibles in the refinery itself and sold as LPG.
Lower down the column petrols, kerosene and diesels accumulate. Then, the bottom products of the topping unit are sent to another column, called a Vacuum. These then leave the Vacuum via a series of different plants (Visbreaking and Thermal Cracking) where they are transformed (or converted), breaking up the long carbon atom chains into lighter, more sought-after petrol and diesel products.
What is not converted is used for the production of bitumen. The petrol and diesel products which have come from the topping and conversion plants undergo final further treatments to improve their composition and ensure they are suitable to be offered to the market. Examples of areas where they are optimised include sulphur content, benzene and octane number. 
Petroleum derives from the Latin petra oleum which literally translates as stone oil and is a sort of dense, oily soup with a distinctive smell and a colour ranging from yellow-brown to blackish. It can be described as a kind of hodge podge of composites, or, as chemists might say in order to emphasise that it is made up of hydrogen and carbon, hydrocarbons. These composites are of widely varying weights and dimensions and are the result of carbon’s tendency to form long linear chains of linked atoms in closed-ring or forked formations.
Those found on this page are composites, with complex, peculiar forms, which can be found in a barrel. Depending on the form and how the atoms link together, the hydrocarbon composites are then set upon different, but similarly long and complicated paths inside the refinery. 
A barrel is, together with tonnes, the most commonly used measure found in the oil sector. A single barrel is equivalent to approximately 160 litres, based on the wooden barrels used in Pennsylvania to collect crude at the dawn of the oil industry.
A refinery can consist of a simple structure or an extremely complex and sophisticated facility. The more complex it is, the greater the capacity to obtain greater amounts of quality products such as petrol and diesel from every barrel rather than those with a lower market value such as combustible oil.
The octane number measures the Anti Knock of a fuel, particularly petrol. Knocking can compromise the engine life so to increase the octane number, which in creases the fuel’s resistance to knocking, petrols obtained from reforming and isomerisation processes are mixed and then anti-knocking compounds such as MTBE are added.