Petroleum mixtures refining

Alkanes occur in nature in deposits of natural gas and oil. Natural gas is primarily methane, containing progressively smaller amounts of ethane, propane, and butanes. Petroleum is a complex mixture of alkanes and other hydrocarbons. Petroleum is refined by distillation. The various distillation cuts, based on boiling point, are shown in Table 5.2. 

Before fractional distillation, petroleum is refined by a pre-distillation method so that undesired oomponents are driven out of the petroleum mixture. After that, the petroleum is pumped through heated pipes at 350-400° C. Here, the petroleum becomes vapor and this is sent to the fractional distillation unit The petroleum vapor starts rising to the upper parts of the fractional distillation unit. The vapor of petroleum cools down at lower temperatures the uppermost part of the distillation unit is the place for gases (methane, ethane, propane and butane), which have boiling points lower than 2QPC C Hg and C H.jq are separated from each other at high pressures and stored in canisters for home use. crude oil... 

Alkanes, the simplest hydrocarbons, are found in ail shapes and sizes and occur widely in nature. They are the major constituents of petroleum, a complex mixture of compounds that includes hydrocarbons such as hexane and decane. Petroleum is refined to produce gasoline, diesel fuel, home heating oil, and a myriad of other useful compounds. In Chapter 4, we learn about the properties of alkanes, how to name them (nomenclature), and oxidation—one of their important reactions. 

Bunker fuel— A relatively viscous, liquid hydrocarbon mixture, also known as bunker-C fuel oil, that remains after lighter hydrocarbons are distilled from petroleum during refining. Bunker C is used as a fuel by oil-fired generating stations, heating plants, and ships. 

Petroleum, vital to world economy as a source of fuels and lubricants is a complex mixture of hydrocarbons and minor impurities. In the early days of the petroleum industry, petroleum products were separated by simple distillation and were simply mixtures of the original constituents, differing in composition from one fraction to another in accordance with the boiling points of the individual compounds. Later, with the advent of cracking, reforming, solvent extraction, and other methods of conversion and separation, the number of differently constituted fractions produced from petroleum by refiners began to swell logarithmically. 

The two most important natural sources of alkanes are petroleum and natural gas. Petroleum is a complex liquid mixture of organic compounds, many of which are alkanes or cycloalkanes. For more details about how petroleum is refined to obtain gasoline, fuel oil, and other useful substances, read A Word about Petroleum, Gasoline, and Octane Number on pages 102-103. 

American Petroleum Institute, Bibliographies on Hydrocarbons, Vols. 1-4, "Vapor-Liquid Equilibrium Data for Hydrocarbon Systems" (1963), "Vapor Pressure Data for Hydrocarbons" (1964), "Volumetric and Thermodynamic Data for Pure Hydrocarbons and Their Mixtures" (1964), "Vapor-Liquid Equilibrium Data for Hydrocarbon-Nonhydrocarbon Gas Systems" (1964), API, Division of Refining, Washington. 

In the petroleum refining and natural gas treatment industries, mixtures of hydrocarbons are more often separated into their components or into narrower mixtures by chemical engineering operations that make use of phase equilibria between liquid and gas phases such as those mentioned below ... 

From complex cuts characterized in an overall manner, there is a transition towards mixtures containing only a limited number of hydrocarbon families or even compounds. This development has only just begun. It affects for the moment only certain products and certain geographical zones. It is leading gradually to a different view of both refining and the characterization of petroleum products. 

Liquefied Petroleum Gas (LPG). Certain specific hydrocarbons, such as propane, butane, pentane, and their mixtures, exist in the gaseous state under atmospheric ambient conditions but can be converted to the Hquid state under conditions of moderate pressure at ambient temperature. This is termed Hquefied petroleum gas (LPG). Liquefied petroleum gas (qv) is a refinery product and the individual constituents, or light ends (Table 4), are produced during a variety of refining operations. 

Because phenols are weak acids, they can be freed from neutral impurities by dissolution in aqueous N sodium hydroxide and extraction with a solvent such as diethyl ether, or by steam distillation to remove the non-acidic material. The phenol is recovered by acidification of the aqueous phase with 2N sulfuric acid, and either extracted with ether or steam distilled. In the second case the phenol is extracted from the steam distillate after saturating it with sodium chloride (salting out). A solvent is necessary when large quantities of liquid phenols are purified. The phenol is fractionated by distillation under reduced pressure, preferably in an atmosphere of nitrogen to minimise oxidation. Solid phenols can be crystallised from toluene, petroleum ether or a mixture of these solvents, and can be sublimed under vacuum. Purification can also be effected by fractional crystallisation or zone refining. For further purification of phenols via their acetyl or benzoyl derivatives (vide supra). 

Crude oil is a mixture of many different hydrocarbons and small amounts of impurities. The composition of crude oil can vary significantly depending on its source. Petroleum refineries are a complex system of multiple operations and the operations used at a given refinery depend upon the properties of the crude oil to be refined and the desired products. For these reasons, no two refineries are alike. Portions of the outputs from some processes are re-fed back into the same process, fed to new processes, fed back to a previous process, or blended with other outputs to form finished products. The major unit operations typically involved at petroleum refineries are described briefly below. In addition to those listed below, there are also many special purpose processes that cannot be... 

Storage tanks are used throughout the refining process to store crude oil and intermediate process feeds for cooling and further processing. Finished petroleum products are also kept in storage tanks before transport off site. Storage tank bottoms are mixtures of iron rust from corrosion, sand, water, and... 

Raw petroleum (crude oil) is extracted from underground around the globe in a variety of ways and refined for tens of thousands of applications in our everyday lives. Crude oil is refined into usable petroleum products through several unique processes. Fractional distillation is the process used to efficiently extract or "distill" products that are a mixture of chemicals such as gasoline, diesel fuel, and kerosene or may selectively extract pure chemical compounds or petrochemicals such as... 

Distillation may be defined as the separation of the constituents of a liquid mixture by partial vaporization of the mixture, followed by separate recovery of the vapor and liquid residue. Since crude petroleum is the most complex mixture of liquids found in nature, it is not surprising that distillation is one of the most important processes in modem petroleum refining. 

British Foreign Minister Ernest Bevin once said that "The Kingdom of Heaven runs on righteousness, but the Kingdom of Earth tuns on alkanes." Well, actually he said "tuns on oil" not "runs on alkanes," but they re essentially the same. By far, the major sources of alkanes are the world s natural gas and petroleum deposits. Laid down eons ago, these deposits are thought to be derived from the decomposition of plant and animal matter, primarily of marine origin. Natural gas consists chiefly of methane but also contains ethane, propane, and butane. Petroleum is a complex mixture of hydrocarbons that must be separated into fractions and then further refined before it can be used. 

FIGURE 6.9 Flexicoking is a commercial process for refining petroleum that has been applied to heavy oil and tar sand fractions. The process employs circulating fluidized beds and operates at moderate temperatures and pressures. The reactor produces liquid fuels and excess coke. The latter is allowed to react with a gas-air mixture in the gasifier fluidized bed to provide a low-value heating gas that can be desulfurized and used as a plant fuel. Courtesy, Exxon Research and Engineering Company. 

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