Ethylene Derivatives (Part - 2) | Chemical Technology - Chemical Engineering PDF Download

Mono- , Di- Tri- Ethylene Glycols (Meg, Deg, Teg)

A major petrochemicals and find application in manufacture of polyester and as antifreeze accounts for 70% of Ethylene oxide production. Ethylene oxide preheated to 195^oC. EO:H₂O ratio 10:1 to maximize MEG production By Products DEG, TEG. Figure M- VII 5.3 gives detail manufacturing of MEG, DEG and TEG from Ethylene Oxide

Figure M- VII 5.3: MEG, DEG and TEG from Ethylene Oxide

Vinyl Chloride
 

Vinyl chloride is one of the important petrochemical feedstocks and find use in manufacture of poly vinyl chloride the second largest tonnage commercial polymer after polyethylene. About 95percent of the present vinyl chloride production worldwide is used in polymer production or copolymer application. Another important use of vinyl chloride is in the production of vinylidiene chloride. According to SRI consulting global production and consumption of Ethylene dichloride (EDC) in 2009 (which accounts for 95 percent consumption in vinyl chloride manufacture), was about 33.7 million tones with global capacity of about 73 percent in 2009.

Process Technology 

The original process of manufacture of vinyl chloride was by reaction of acetylene derived from calcium carbide with hydrochloric acid in gaseous phase in presence of mercuric chloride catalyst at temperature around 100- 180 ^oC. However with the availability of ethylene from cracker plant now vinyl chloride is made from ethylene obtain from cracker plant

Direct Chlorination

• The process of vinyl chloride manufacture takes place in two stages.
• First stage: Ethylene is reacted with chlorine in either liquid or vapor phase in presence of ferric chloride. However, the liquid phase process is more common and the reaction takes place at around 50- 90 ^oC and 3- 5 atm pressure.
• Second stage: Vinyl chloride is produced by pyrolysis of vaporised ethylene dichloride in a set of tubular furnaces at temperature of about 400- 500 ^oC.
• Direct chlorination:

Process Technology

The process of vinyl chloride manufacture takes place in two stages.

First Stage: Ethylene is reacted with chlorine in either liquid or vapor phase in presence of ferric chloride. However, the liquid phase process is more common and the reaction takes place at around 50- 90 ^oC and 3- 5 atm pressure.

Second Stage: Vinyl chloride is produced by pyrolysis of vaporised ethylene dichloride in a set of tubular furnaces at temperature of about 400- 500^oC.
Ethylene chloride by direct Chlorination of Ethylene:

• The original process of manufacture of vinyl chloride by ethylene chlorination and cracking of ethylene dichloride had been replaced by oxychlorination process in which no hydrochloric acid is formed as byproduct. Process diagram of vinyl chloride from oxychlorination process is shown in Figure M- VII 5.4.
• The process involves production of ethylene dichloride by exothermic reaction of ethylene, hydrochloric acid and oxygen
• Liquid phase: Fixed or fluidized bed reactor is used at 170- 180^oC and 15- 20 atm pressure in presence of copper chloride.
• Vapor phase reaction: The temperature and pressure are 200- 220^oC and 20- 50 atm pressure.

Reactions

Vinyl Chloride by Chlorination

Propagation:

Termination:

The first stage is typical electrophilic addition of a halogen to an alkene. The second stage is a free radical chain reaction.

Oxychlorination

The original process of manufacture of vinyl chloride by ethylene chlorination and cracking of ethylene dichloride had been replaced by oxychlorination process in which no hydrochloric acid is formed as byproduct. The process involves production of ethylene dichloride by exothermic reaction of ethylene, hydrochloric acid and oxygen. Liquid phase: at about 170- 180 oC in at 15-20 atm pressure in presence of copper chloride in either fixed or fluidised bed reactor.Vapor phase reaction: the temperature and pressure are 200- 220 oC and 20- 50 atm pressure

Figure M-VII 5.4: Vinyl Chloride from Oxychlorination Process

Vinyl Acetate

Vinyl acetate is one of the important derivatives of ethylene which is used as intermediate for manufacture of polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, etc.
Global end use pattern of vinyl acetate is:- Adhesives (23%), paints and coating (29%), textiles (21%), plastics (17%), paper and board (10%). Consumption pattern of vinyl acetate in India is polyvinyl acetate emulsions & resins (50%), polyvinyl alcohol (25%), ethylene vinyl acetate (10%), others (15%).

End use pattern of vinyl acetate in India is :- Adhesives (35- 40%), textiles (30- 35%), paints and coating (15-20%), others (10-15%)

Process Technology: 

• The ethylene route has replaced the traditional process of manufacture of vinyl acetate. The production of vinyl acetate through acetylene route, which was developed by Wacker in 1930, involves reaction of acetylene and acetic acid in liquid phase at 60- 80 oC and 1- 2 atm pressure in presence of mercury salt catalyst.

Vinyl acetate from Ethylene route 

• Vinyl acetate is made by reaction of ethylene with acetic acid by liquid phase process or by vapor phase process in presence of palladium and cupric chloride catalyst. In the vapor phase process, following reactions take place:

Use of Vinyl Acetate

• Fermentation of molasses
• Catalytic hydration of ethylene
• Ethylene esterification and hydrolysis

Fermentation of Molasses:

Ethyl alcohol is prepared from molasses by fermentation process utilising yeast enzymes.Separation of 8-10% alcohol is achieved in a series of distillation columns, as alcohol and water at 95% concentration form azeotropic mixture.

Ethanol by Esterification and Hydrolysis 

• Ethylene and sulphuric acid are reacted at 80 ^oC and 1.5 MPa to form a mixture of ethyl sulphates, which are then hydrolysed to ethyl alcohol.
• Ethylene and sulphuric acid are reacted in absorber from which the mixture of ethylene sulphates thus formed is fed to hydrolyser from which the crude alcohol and sulphuric acid are fed to stripping section and caustic scrubbing section and finally to a series of two distillation columns for separation of ether and alcohol.

Ethanol by Vapor Phase Hydration of Ethylene

• An ethylene rich gas is mixed with water and heated to about 300 ^oC and passed on to fixed bed catalytic reactor where catalytic hydration of ethylene takes place

• The catalyst used is phosphoric acid deposited on silica gel. The reactor effluents are sent to separator for separation of vapor and liquid. The gases from the separator are cooled and scrubbed with water to recover traces of alcohol. The alcohol water mixture is sent to a series of distillation columns where ether is separated in the light end column and finally 95% by volume ethanol water azeotrope is separated.

Figure M- VII 5.5: Ethanol from Catalytic Recycle Hydration of Ethylene

Acetaldehyde

Table M-VII 5.8: Product Profile of Acetaldehyde