Reactive distillation

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Benefits

Increased speed and improved efficiency

Lower costs reduced equipment use, energy use and handling jvc gz mg505

Less waste and fewer byproducts drum dryer

Improved product quality reducing opportunity for degradation because of less heat dehumidifier industrial

Difficulties

The conditions in the reactive column are suboptimal both as a chemical reactor and as a distillation column, since the reactive column combines these.

The introduction of an in situ separation process in the reaction zone or vice versa leads to complex interactions between vapor-liquid equilibrium, mass transfer rates, diffusion and chemical kinetics, which poses a great challenge for design and synthesis of these systems.

Side reactors, where a separate column feeds a reactor and vice versa, are better for some reactions, if the optimal conditions of distillation and reaction differ too much.

Setup

Typically, reactive distillation equipment comprises a reactive column, with the feed input, with directly attached stripping and enriching columns with the outputs.

Applicable Processes

Reactive distillation can be used with a wide variety of chemistries, including the following:

Acetylation

Aldol condensation

Alkylation

Amination

Dehydration

Esterification

Etherification

Hydrolysis

Isomerization

Oligomerization

Transesterification

Hydrodesulfurization of light oil fractions

Example

The esterification of acetic acid with alcohols like n-butanol, ethanol, isobutanol and amyl alcohol fall in a typical class of reacting systems.

n-Butyl acetate is an industrially important chemical with wide applications as a versatile solvent. It is manufactured by the esterification of acetic acid with n-butanol in the presence of suitable acid catalyst. The alcohol is sparingly soluble in water and the ester is almost insoluble.

Another interesting feature of this system is that it is associated with the formation of a minimum boiling ternary azeotrope of ester, alcohol and water, which is heterogeneous in nature. Hence, in a typical reactive distillation column that consists of both reactive and non-reactive zones, the heterogeneous azeotrope or a composition close to the azeotrope can be obtained as the distillate product. Moreover, the aqueous phase that forms after the condensation of the vapor is almost pure water.

Depending on the requirement either of the phases can be withdrawn as a product and the other phase can be recycled back as reflux. The pure ester i.e. butyl acetate, being the least volatile component in the system, is realized as a bottom product.

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Distillation

Principles

Raoult's law  Dalton's law  Reflux  Fenske equation  McCabe-Thiele method  Theoretical plate  Partial pressure  Vapor-liquid equilibrium

Industrial processes

Batch distillation  Continuous distillation  Fractionating column  Spinning cone

Laboratory methods

Alembic  Kugelrohr  Rotary evaporator  Spinning band distillation  Still

Techniques

Azeotropic  Destructive  Dry  Extractive  Fractional  Reactive  Salt-effect  Steam-based  Vacuum-based

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