Introduction
- • In this lecture we study the process technology involved in the production of Vinyl Chloride from Ethylene.
- • We first present the process technology associated to Ethylene Chloride .
• Vinyl chloride is produced in a two step process from ethylene.
• Ethylene first reacts with Chlorine to produce Ethylene dichloride.
• The purified Ethylene dichloride undergoes selective cracking to form vinyl chloride.
16.1 Ethylene dichloride
16.1.1 Reactions
- • C2H4 + Cl2 → C2H4Cl2
• Undesired products: Propylene dichloride and Polychloroethanes.
• Reaction occurs in a liquid phase reactor with ethylene dichloride serving as the liquid medium and reactants reacting the liquid phase.
• Catalyst is FeCl3 or Ethylene dibromide.
16.1.2 Process Technology (Figure 16.1)
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Figure 16.1 Flow sheet of production of ethylene dichloride
- • C2H4 and Cl2 are mixed and sent to the liquid phase reactor.
• Here, the feed mixture bubbles through the ethylene dichloride product medium.
• Reactor operating conditions are 50°C and 1.5 – 2 atms.
• The reaction is exothermic. Therefore, energy is removed using either cooling jacket or external heat exchanger.
• To facilitate better conversion, circulating reactor designs are used.
• FeCl3 traces are also added to serve as catalyst.
• The vapour products are cooled to produce two products namely a vapour product and a liquid product. The liquid product is partially recycled back to the reactor to maintain the liquid medium concentration.
• The vapour product is sent to a refrigeration unit for further cooling which will further extract ethylene dichloride to liquid phase and makes the vapour phase bereft of the product.
• The liquid product is crude ethylene dichloride with traces of HCl. Therefore, acid wash is carried out first with dilute NaOH to obtain crude ethylene dichloride. A settling tank is allowed to separate the spent NaOH solution and crude C2H4Cl2 (as well liquid).
• The crude ethylene dichloride eventually enters a distillation column that separates the ethylene dichloride from the other heavy end products.
• The vapour phase stream is sent to a dilute NaOH solution to remove HCl and produce the spent NaOH solution. The off gases consist of H2, CH4, C2H4 and C2H6.