Outline Introduction to petrochemicals

Chemical conversions for manufacture of petrochemicals

Petrochemicals from Methane, Ethylene, Propylene, Butylenes and BTX

Manufacture of Acetylene, Ethylene oxide, Acrylonitile, Dimethyl terephthalate

2. Main Petrochemicals

1

2.1. Introduction to petrochemicalsHydrocarbons obtained from the gaseous components on fractional distillation of crude oil are used further for production of other organic compounds called petrochemicals

Methyl alcohol, ethyl alcohol, ethylene, benzene, toluene, D.D.T etc are some of petrochemical

Many processes such as cracking, cyclization, oxidation, halogenations, etc. are used for the manufacture of petrochemicals

Also the petroleum oil is used for manufacture of many products. These products are synthetic fibers, synthetic rubber, perfumes, fertilizers, explosives, dyes, etc.

2

2.2 Chemical Conversions for Manufacture of PetrochemicalsThe petrochemical industry produces solvents and chemicals of various grades used to produce industrial organic chemicals, including benzene, butylenes, cresols, cresylic acids, ethylene, naphthalene, paraffins, propylene, toluene, and xylenes.

A chemical conversion processes converts a raw material into products, by-products, intermediate products, or waste streams areCrackingHydrogenation,IsomerizationDisproportionation

3

2.3 Petrochemicals from Methane, Ethylene, Propylene, Butylenes and BTX Diagram schematically depicts the major hydrocarbon sources used in producing petrochemicals

4

…Cont’d

5

Paraffinic hydrocarbons used for producing petrochemicals range from the simplest hydrocarbon, methane, to heavier hydrocarbon gases and liquid mixtures present in crude oil fractions and residues.

The C6–C9 paraffins and cycloparaffins are especially important for the production of aromatics through reforming.

Methane (CH4)It is the first member of alkane series and is the main component of natural gas

it is partially oxidized with a limited amount of oxygen to a carbon monoxide-hydrogen mixture at high temperatures in presence of a catalyst.

The mixture (synthesis gas) is an important building block for many chemicals.

…Cont’d

6

Olefinic hydrocarbons

7

The most important olefins used for the production of petrochemicals are ethylene, propylene & butylenes

Ethylene(CH2=CH2)The first member of the alkenes, is a colorless gas with a sweet odour.

It is a highly active compound that reacts easily by addition to many chemical reagents.

ethylene forms ethyl alcohol, Ethylene dichloride, vinyl chloride, ethyl benzene and so on.

Flow chart for manufacture of Petrochemicals from ethylene

…Cont’d

8

Propylene (CH3CH=CH2)

9

It is a reactive alkene that can be obtained from refinery gas streams, especially those from cracking processes.

Many important chemicals from propylene are isopropanol, allyl alcohol, glycerol, and acrylonitrile.

Flow chart for manufacture of Petrochemicals produced from propylene

Butylenes (C4H8)

10

Butylenes are by-products of refinery cracking processes and steam cracking units for ethylene production

Dehydrogenation of butanes is a second source of butenes.

isobutylene (a butane isomer) is currently highly demanded for the production of oxygenates as gasoline additives.

Butadiene (CH2=CH-CH=CH2)Main sources of butadiene are the catalytic dehydrogenation of butanes and butenes, and dehydration of 1,4-butanediol.

Butadiene is important monomer for synthetic rubber production.

important intermediate for the synthesis of many chemicals such as hexamethylenediamine and adipic acid.

Aromatic hydrocarbons

11

Benzene, toluene, xylenes (BTX), and ethyl benzene are the aromatic hydrocarbons with a widespread use as petrochemicals.

They are important precursors for many commercial chemicals and polymers such as phenol, trinitrotoluene (TNT), nylons, and plastics.

Flow chart for manufacture of Petrochemicals from BTX

…Cont’d

12

2.4. Manufacture of Acetylene, Ethylene oxide, Acrylonitile, Dimethyl terephthalate

13

Manufacture of AcetyleneAcetylene (CH≡CH, melting point –81.5°C, boiling point–84°C) is an extremely reactive hydrocarbon & moderately soluble in water / alcohol

There are two Methods of Manufacturing 1. From calcium carbide reaction with water Reaction: CaC2 + 2H2O → HC≡CH + Ca(OH)2 2. pyrolysis, or cracking, of natural gas or liquid hydrocarbon feeds. It can be produced by a submerged-flame process from

crude oil. The processes includes ,partial oxidation using oxygen

thermal cracking, supply both the high temperature & energy.

Reaction: 2CH4 → HC≡CH + 3H2

…Cont’d

14

The methane (combustion and splitting) with the oxygen & then the acetylene and gases are cooled rapidly.

Acetylene is removed in a column (packed) by a selective solvent such as dimethyl formamide. Carbon dioxide is flashed and stripped overhead out.

Flow chart of acetylene manufacture by partial oxidation of hydrocarbons

Manufacture of Ethylene oxide

15

It (freezing point: –111.7oC, boiling point: 10.4oC) is a colorless gas

It is miscible in all proportions with water/ alcohol &very soluble in ether.

It is manufactured by air epoxidation of ethylene in the presence of a silver catalyst

Reaction: Flow chart for manufacture of ethylene oxide.

Manufacture of Acrylonitile

16

Acrylonitrile (2-propenonitrile, propene nitrile, vinyl cyanide, CH2=CHCN; freezing point: –83.5oC, boiling point: 77.3oC)

It is manufactured from acetylene by reaction with hydrogen cyanide.

Reaction :HC≡CH + HCN → CH2=CHCNpresently the ammoxidation (ammonoxidation or oxyamination) of propylene that involves reaction of propylene, ammonia, and oxygen at 400 to 450oC & (48 to 200 kPa) in Bi2O3 ·nMnO3 catalyst

Reaction :2CH2=CHCH3 + 2NH3 + 3O2 → 2CH2=CHCN + 6H2O

Flow chart for manufacture of acrylonitrile by the ammoxidation of propylene.

17

Manufacture of DIMETHYL TEREPHTHALATE

18

Dimethyl terephthalate has melting point of 141oC

It is prepared by oxidation of p-xylene & subsequent esterification with methyl alcohol

Reaction: CH3C6H4CH3 + [O] → HOOCC6H4COOH

HOOCC6H4COOH + 2CH3OH → CH3OOCC6H4COOCH3

Flow chart for Manufacture of dimethyl terephthalate.

19