methods of preparation of ethyl acrylate

Ethyl acrylate is an important organic compound used in the production of polymers and copolymers, widely applied in paints, adhesives, textiles, and coatings. Given its industrial significance, understanding the methods of preparation of ethyl acrylate is crucial for chemical engineers and professionals in the chemical industry. In this article, we will explore the main methods for preparing ethyl acrylate, including detailed steps, reactions involved, and the pros and cons of each method.

1. Esterification of Acrylic Acid

The most common method of preparing ethyl acrylate is through the esterification of acrylic acid with ethanol. This process is a classic example of Fischer esterification, where a carboxylic acid reacts with an alcohol in the presence of an acid catalyst, usually sulfuric acid or p-toluenesulfonic acid.

Reaction Process:

The reaction mechanism involves the protonation of acrylic acid, followed by nucleophilic attack from ethanol. The result is the formation of ethyl acrylate and water:

CH₂=CHCOOH C₂H₅OH → CH₂=CHCOOC₂H₅ H₂O

Key Considerations:

• Catalyst Choice: Sulfuric acid is typically used, but the use of a solid acid catalyst or ion-exchange resins can minimize environmental concerns.
• Reaction Conditions: High temperatures (70-100°C) and continuous removal of water by distillation are critical for driving the equilibrium towards ethyl acrylate formation.

Advantages and Disadvantages:

• Advantages: This method is relatively simple, and the raw materials (acrylic acid and ethanol) are readily available.
• Disadvantages: It is an equilibrium reaction, and removal of water is necessary to achieve higher yields. Corrosion issues due to the acidic environment may also occur, necessitating specialized equipment.

2. Catalytic Oxidation of Propylene

Another method for the preparation of ethyl acrylate involves the catalytic oxidation of propylene to acrylic acid, followed by esterification with ethanol. This process can be integrated into larger industrial systems producing various acrylate esters.

Reaction Overview:

This process begins with the oxidation of propylene (C₃H₆) to acrylic acid using catalysts such as molybdenum or vanadium-based compounds. Once the acrylic acid is formed, it undergoes the same esterification reaction with ethanol to produce ethyl acrylate.

C₃H₆ O₂ → CH₂=CHCOOH
CH₂=CHCOOH C₂H₅OH → CH₂=CHCOOC₂H₅ H₂O

Industrial Application:

• Multi-step Process: This method involves two main stages—oxidation and esterification. The oxidation process requires precise control of temperature, oxygen levels, and catalyst activity to maximize acrylic acid yields.
• Catalysts: The oxidation process uses specific metal oxide catalysts (molybdenum or vanadium oxides) which are effective for the selective oxidation of propylene to acrylic acid without significant byproduct formation.

Pros and Cons:

• Advantages: This method can be integrated into existing acrylic acid production units, making it cost-effective in large-scale manufacturing.
• Disadvantages: The oxidation step is energy-intensive and requires careful management to prevent the formation of byproducts or the loss of valuable reactants.

3. Transesterification of Methyl Acrylate

An alternative method for producing ethyl acrylate is transesterification of methyl acrylate with ethanol. This process involves exchanging the alcohol group of methyl acrylate with ethanol, which leads to the formation of ethyl acrylate and methanol.

Reaction Mechanism:

The reaction occurs in the presence of a basic or acidic catalyst, which promotes the exchange of the methoxy group (-OCH₃) with an ethoxy group (-OC₂H₅).

CH₂=CHCOOCH₃ C₂H₅OH → CH₂=CHCOOC₂H₅ CH₃OH

Conditions:

• Catalysts: Commonly used catalysts include sodium hydroxide or strong acid catalysts like sulfuric acid.
• Temperature: The reaction typically proceeds at mild temperatures (60-80°C), and methanol is continuously removed to drive the equilibrium towards ethyl acrylate.

Benefits and Drawbacks:

• Advantages: This process can be useful if methyl acrylate is readily available as a byproduct in other chemical processes. It allows for mild reaction conditions and relatively high yields.
• Disadvantages: This method is generally less preferred in industries where methyl acrylate is not an easily accessible raw material, limiting its broader application.

Conclusion

There are multiple methods of preparation of ethyl acrylate, each with its advantages and industrial relevance. The esterification of acrylic acid remains the most straightforward and widely used method, but the catalytic oxidation of propylene and transesterification of methyl acrylate are viable alternatives depending on the availability of raw materials and specific industrial setups. For manufacturers, the choice of method will depend on factors like the cost of raw materials, environmental considerations, and equipment availability.