User:Khairi Ali Mohamed

The account of this former contributor was not re-activated after the server upgrade of March 2022.

I will research for refinery processes , and i need to know how produce different products ,petrol ,leaded and unleded petrol. Petroleum products, including petrol, are primarily a mixture of hydrocarbons (molecules containing hydrogen and carbon molecules) with small amounts of other substances. Crude oil is comprised of different lengths of hydrocarbon chains, with some short chains and some very long chains. Depending on how much the oil is broken down, or refined, it may become any number of products. In general, the smaller the molecule, the lower the boiling point. Therefore, gas, with very small chains of one to five carbons, boils at a very low temperature whilst petrol, with 6-10 carbons, boils at a slightly higher temperature. The heaviest oils may contain up to 25 carbon atoms and not reach their boiling point until 761°F (405°C). Petrol is a mixture of compounds of carbon and hydrogen called hydrocarbons; most of the hydrocarbons in petrol are alkenes. In modern car engines, the petrol vapour-air mixture is highly compressed before it is sparked, in order to get the maximum energy from the burning fuel. However, some hydrocarbons tend to ignite under pressure before they are sparked, so that the engine runs roughly; this is known as "knocking". Branched-chain alkenes tend to resist this pre-ignition better than alkenes with unbranched chains. Alkenes and fuel mixtures are given Octane ratings depending on their knocking tendency. 2,2,4-trimethylpentane (which contains 8 carbons and so is an isomer of octane) has an Octane rating of 100; heptanes has a rating of 0. The Octane number of a petrol is the % of 2,2,4-trimethylpentane in a mixture with heptanes that has the same knocking characteristics as the petrol under test as illustrated in figure 1. The petrol fraction from refining crude oil has an octane rating below 60, which is why you can't put it straight into a car (which needs 87 octane for 2-star and 93 octane for 4-star).

   Figure 1             Heptane                                            2,2,4-trimethylpentane

And the Lead added to petrol to improve the octane rating and helps the petrol to burn more slowly and smoothly, preventing knocking and giving higher Octane ratings, but due to environmental concerns this is no longer common. 11