Separation Process Principles (3rd Edition) Edit edition

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The process for the production of fluorocarbons from carbon tetrachloride and hydrogen fluoride comprises of a number of steps. The block-flow diagram for the process is given below:

Major reactions for the process are as follows:

In the reactor (block-1), carbon tetrachloride (CCl₄) reacts with hydrogen fluoride (HF) in the presence of catalyst antimony pentoxide (Sb₂O₅).

Main effluents from the reactor are hydrogen chloride (HCl), trichloro-fluoro-methane (CCl₃F), dichloro-difluoro-methane (CCl₂F₂), unreacted CCl4, and small amounts of water and chlorine. Water comes from HF, which contains water as an impurity.

Effluents from the reactor (block-1), are sent to the distillation column (block-2) where CCl4 is removed as the bottom product and is recycled to the reactor. Distillate of the distillation column (block-2) is sent to the first absorber (block 3) for absorption of HCl by water. Aqueous HCl is obtained as the by-product.

Gas coming out of the first absorber (block-3) contains residual HCl, and chlorine (Cl₂). Cl₂ is absorbed by aqueous NaOH in the second absorber (block-4). Gas leaving this second absorber contains moisture, which is removed by absorption with Sulfuric acid (H₂SO₄) in third absorber (block-5).

Gas from third absorber (block-5) is sent to second distillation column (block-6) where CCl₂F₂ is obtained as a distillate, which is dried to remove the moisture. Bottom product of the second distillation column (block-6) is again sent to a distillation column (block-7) and CCl₃F is obtained as distillate, which is also dried to get rid of the moisture.

Finally, the bottom product of the third distillation column (block-7) is recycled back to the reactor (block-1).