Petrochemistry

see also: Etymology of Petrochemistry

The petrochemistry is the science which is interested in the use of the chemical compounds basic resulting from the Pétrole to manufacture others synthetic compounds which can exist or not in nature; in the last case, these compounds are known as artificial. This manufacture, in general, is based on on because if not I do not include/understand this sentence--> of the chemical reactions adapted in presence or not of a Catalyst.

For example, (see the article Refining of oil), the cut Naphtha resulting from atmospheric distillation, can be used as load with a unit of vapocraquage (or cracking with the vapor). This Naphta can be cracked in a vapocraquor, and gives products unsaturated, fragile and likely to be transformed into Plastics and other cosmetic and medicinal products. Thus starting from oil one can manufacture Plastics of all kinds employed then like raw materials in the sectors of construction and industry electric, electronic, the textile, aeronautics and others.

A vapocraquor is a unit of petrochemistry being used to manufacture ethylene and Propylène two products essential in the manufacture of polyethylene and polypropylene, two well-known plastics.

Indeed, while making pass the intermediate products obtained either by distillation, or by minor units, in specific units of petrochemistry one obtains raw materials likely to be transformed into products which do not exist in nature.

The Natural gas can also provide raw materials, methane, ethane for petrochemistry. We will see the various diagrams of transformations of these products into others made up organics whose ultimate terms of transformations are:

of the Plastics,
of the Solvent S,
of the resins,
of synthetic fibers,
of the Detergent S,
of the Plasticizer S,
of the elastomer S,
of the adhesives,
of the Polyester,
of the Nylon,
of the drugs,
of the cosmetics.
of the Manure

Petrochemistry is based mainly on two types of processes:

by cracking with the vapor,
by processes of extraction.

but also, by reforming with the vapor of natural gas or the naphthas it leads to the production of hydrogen which is useful, beyond its use as energy Vecteur and petrochemical vector in the hydro-treatings, to the manufacture of ammonia then manures, methanol and alcohols oxo, inter alia.

With the first type of processes, one obtains olefin while with the second type, one extracts from the aromatic . The olefins and the aromatic ones are raw materials which one calls of the major intermediates being useful in industry of the plastics, pharmaceutical, cosmetic, electronic, aeronautical and of the textile.

Vapocraquor

This process is a process used in petrochemistry, but the refiner benefits from it to recover under products such as C3, C4, C5 and the raffinat to be used in the composition of the fuels.

Indeed, the objective of this process is to produce ethylene (C₂H₄) and propylene (C₃H₆) which are bases in the manufacture of the Polyéthylène and of the Polypropylène by Polymérisation. These two products belong to the major intermediates .

The load used is Naphta coming from the Raffinerie or bought outside.

In the oil industry one always seeks to maximize the production of the matters with high commercial value and the fact of breaking the long chains to obtain shorter chains is a useful and advantageous objective.

It should be noted that the ethylene and the Propylène exist only seldom in great quantities in nature because nature does not like the unstable states. Indeed, in term of Chimie one says that these products are Insaturé S i.e. some of the connections being used to connect the carbon atoms between them are double. These unsaturated compounds are less stable than the saturated compounds which have only simple connections. They thus tend to be saturated while collecting is other atoms of hydrogen or of the oxygen atoms.

The petrochemical operation consists in taking a cut heavy Naphta containing Hydrocarbure S saturated having long hydrocarbon chains with ten atoms of Carbone.

The unit functions with very high Température and low Pression. One introduces this cut naphtha into the vapocraquor who has a series of engines. Inside this unit reigns a very high temperature, about 500 °C with 600 °C and in the presence of the steam (about 50/50 in weight) which reduces the “time of residence” and avoids the formation of coke. Under these conditions, the hydrocarbon molecules of naphtha are divided into several pieces giving rise to liquid gases, ethylene, Propylène, Butadiène, Isobutène and other products Insaturé S as well as a cut called raffinat used like component of the fuels.

According to the quality of naphtha, one obtains outputs of more or less high ethylene and propylene. Indeed, to have good propylene and ethylene yields, it is recommended to have paraffinic loads well “” (see the article Pétrole) because the structure of these two products are paraffinic chains . An oil can be paraffinic (contain many paraffins, chains linear without cycle), naphtenic (cycles with simple connections), or aromatic (cycles with double connection combined).

To have an idea, at the exit of the unit, there is an output of about 25% to ethylene 30%, of propylene 15%, the remainder is consisted methane, gasoline rich in aromatic and molecules with 4 carbons sent towards the unit of extraction of the aromatic .

Naphtha is not the only load feeding a vapocraquor. Any molecule relatively long and likely to be divided into several fragments can be “cracked”. Thus one can also use gas oils and distillates like unquestionable aromatic Hydrocarbon like loads.

The ethylene resulting from the vapocraquage is used in the manufacture of Chlorure of vinyl (VC), of the ethylbenzene, the Oxyde of ethylene and the ethanol. Starting from vinyl chloride one manufactures, by polymerization, of the polyvinyl chloride (PVC), plastic with the multiple uses: plastic piping, the plastic building, furnishing, bottles, clothing etc

By vapocraquage, one obtains primarily olefinic products of which we will see the use hereafter.

Derived from olefins

At the exit of the vapocraquor, one obtains especially Oléfine S such as ethylene, propylene, butadiene, isobutylene, normal-butylene and isoprene. In fact intermediate products, by adapted treatments, chlorination, oxidation, polymerization, give rise to a whole product range new. The diagrams hereafter show all the possibilities of manufacture starting from these major intermediates:

Below, derivatives of ethylene:

The following diagram gives the transformations of propylene:

The diagram hereafter watch transformations of butadiene:

Lastly, the transformations of isobutylene, normal butylene and isoprene are indicated in the diagram hereafter: :

Processes of extraction

them aromatic, products during the reactions of vapocraquage are, after hydro-treating, extracts of the gasoline which contains them. In general, one makes call for the extraction, with a solvent, the Diméthylsulfoxyde ( DMSO ) added with a certain percentage of water. The backwash of aromatic of their association with this solvent is then obtained by the Butane, which is nonaromatic like the other components of the load of the vapocraquor, but who, contrary to the latter, separates easily from aromatic by distillation.

Extraction and backwash of aromatic are led in columns full with liquid, called extractors , provided with a rotary tree carrying of the turbines of agitation. Thus one isolates the Benzène, toluene and the Xylène S ( Ortho and Para ).

Derived from the aromatic ones

All the aromatic ones, once extracted and purified, are used as raw materials for other reactions of hydrogenation or oxidation in order to lead to plasticizers, solvents, fibers, insecticides and many other products. One can see hereafter the various diagrams of transformations of the Benzène, of the Cumène, the Toluène and the Xylène S ortho and para .

The transformations of the Benzène can lead to products according to the diagram below:

As for cumene, this one can lead to following products:

To finish, toluene, orthoxylene and paraxylene can generate the products hereafter:

See too

External bonds

educational Resource on petrochemistry

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