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Acetaldehyde Plant

Manufacture of Acetaldehyde From Ethanol
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Manufacture of Acetaldehyde from Ethanol

The manufacturing process of acetaldehyde from ethanol (ethyl alcohol) involves vapor- phase oxidation in the presence of a silver catalyst. Here is a detailed breakdown of the
process:

Chemical Reaction

  • Reaction:
  • Conditions:
  • Temperature: 450 to 600°C
  • Catalyst: Silver wire netting
  • Catalyst: Silver wire netting

Process Flow Description

  • Preheating of Reactor:
  • The reactor is initially preheated to 250-300°C by passing hot gases from a pilot reactor. This prepares the reactor for the main oxidation process
  • Air Supply and Carburettor:
  • Air is introduced into the carburettor, where its temperature is maintained using a heating coil. The air flow is controlled by adjusting a vent valve. Once the reactor reaches the desired temperature, indicated by a glow, the air flow is increased.
  • Steam Application:
  • Steam is applied to the alcohol column and the acetaldehyde distillation column to prepare them for the process. The aldehyde column is pressurized to around 2-2.5 kg/cm²g.
  • Alcohol Vapour Generation:
  • Due to the steam in the alcohol column, alcohol vapours begin to form and are fed to the carburettor. The alcohol feed and carburettor levels are carefully maintained to ensure a continuous supply of an alcohol-water-air vapor mixture to the reactor.
  • Oxidation Reaction:
  • The reactor produces a stream containing acetaldehyde, nitrogen, unreacted alcohol, and other byproducts at 200-250°C. This mixture then passes through a gas cooler.
  • Condensation and Absorption:
  • In the gas cooler, water vapor, unreacted alcohol, and acetaldehyde are condensed. The uncondensed gases enter the bottom of the absorption column, where they interact with an alcohol-water mixture. The heat of absorption is removed using intermediate coolers.
  • Distillation:
  • The mixture, rich in acetaldehyde, is sent to the aldehyde distillation column via heat recovery exchangers. Acetaldehyde, being more volatile, is separated at the top, while the alcohol-water mixture remains at the bottom. Reflux is used to maintain the acetaldehyde quality.
  • Storage:
  • The purified acetaldehyde is then sub-cooled and stored in a tank under nitrogen pressure to prevent oxidation.
  • Alcohol Recovery:
  • The bottom liquid from the distillation column is cooled and sent to an absorber. A portion of this liquid is passed back to the alcohol column to recover any unconverted alcohol. Open steam is applied to the alcohol column, while closed steam is used for the acetaldehyde column.
  • Tail Gas Handling:
  • The tail gases from the absorption column are washed with process water to recover any residual alcohol. The washings are sent to the alcohol column for alcohol recovery.
  • Heat Recovery:
  • Part of the heat required for the aldehyde column is supplied by vaporizing the column bottoms in the heat transfer tubes within the reactor.

This process is highly energy-efficient, leveraging the exothermic nature of the reaction and careful recycling of unreacted alcohol and heat.

Uses

Acetaldehyde is a versatile chemical with numerous industrial applications across various sectors. Some of the primary uses include:

  • Chemical Intermediate:
  • Acetic Acid Production: Acetaldehyde is a key intermediate in the production of acetic acid, which is used in the manufacture of synthetic fibers, plastics, and food additives.
  • Pyridines and Pyridine Derivatives: It is used to synthesize pyridines, which are important in the production of agrochemicals, pharmaceuticals, and vitamins.
  • Peracetic Acid: Acetaldehyde is involved in producing peracetic acid, a powerful disinfectant and bleaching agent.
  • Resins and Plastics:
  • Pentaerythritol: Acetaldehyde is used to produce pentaerythritol, a key ingredient in alkyd resins, which are used in paints, coatings, and varnishes.
  • Butyraldehyde and Butanol: It is also used to produce butyraldehyde, which can be further processed into butanol, a solvent and intermediate in plasticizers.
  • Perfumes and Flavors:
  • Fragrances: Acetaldehyde is used as a precursor in the synthesis of various aroma compounds used in perfumes and flavourings for food and beverages
  • Pharmaceuticals:
  • Active Pharmaceutical Ingredients (APIs): It is used in the synthesis of certain pharmaceuticals, including sedatives, hypnotics, and tranquilizers.
  • Vitamins Production: Acetaldehyde plays a role in the synthesis of vitamins like B5 (pantothenic acid).
  • Textiles and Tanning:
  • Dyes and Leather Tanning: Acetaldehyde is used in the synthesis of various dyes and is also involved in the tanning process of leather.
  • Fuel Additives:
  • Ethanol Production: Acetaldehyde can be used in the hydration of ethylene to produce ethanol, which is then used as a fuel additive to increase octane levels and reduce emissions.
  • Rubber and Paper Industries:
  • Rubber and Paper Industries:
  • Paper Industry: Acetaldehyde is used in the production of cellulose esters, which are used in lacquers and coatings in the paper industry.
  • Agriculture:
  • Pesticides: It is a precursor in the production of pesticides and herbicides that protect crops from pests and diseases.

Consumption Coefficients Basis 1000 kg acetaldehyde

Ethyl Alcohol 100% 1150 Kgs.
Dry Saturated Steam at 8 kg/cm2 2500 Kgs.
Cooling Water (Circulation) 18.5 M3/Hr at 30°C
 Electric Power (Battery Limits) 100 KWH
 Process Water 2 M3
Catalyst (Silver)
(Including melting & handling losses)		  1.0 gms

Applications for the manufacture of the following chemicals. 1150 kgs.

  • Acetic acid
  • Acetic Anhydride
  • Crotonaldehyde 100 KWH.
  • Butanol
  • Pentaerythritol
  • Acrylic Nitrile
  • Glyoxal
  • Pharmaceuticals & Drugs
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