What are the common by-products in the production of methyl methacrylate?

Common by-products in the production of methyl methacrylate and their treatment methods.

Methyl Methacrylate (MMA) is an important organic compound, which is widely used in plastics, coatings, adhesives and other fields. In the production process of MMA, some by-products are inevitably produced due to the influence of reaction conditions, process routes and raw materials. This article will analyze the common by-products in MMA production process in detail and discuss its treatment methods.

1. Acetone process by-products

The acetone method is one of the most commonly used processes in MMA production, and its main raw materials include acetone, methacrylic acid (MAA) and methanol. In the acetone process, a strongly acidic catalyst, such as sulfuric acid, is typically employed to promote the reaction. Due to inaccurate control of reaction conditions or incomplete conversion of raw materials, the following by-products will be produced:

• Unreacted monomer: During the reaction, acetone, acrylic acid or methanol may partially remain and not be completely converted to MMA. These unreacted monomers need to be separated and recovered by a method such as distillation or extraction.

• Catalyst residue: Although the strong acid catalyst plays a promoting role in the reaction process, due to its strong corrosiveness and high activity, it may have side reactions with the reactants to generate some acidic compounds or precipitates. These residual catalysts need to be treated by neutralization or filtration.

• Water and organic impurities: During the reaction, water and some organic impurities may be mixed into the product, affecting the purity of MMA. Therefore, it is usually necessary to perform dehydration and purification by distillation or ion exchange in the subsequent process.

2. Propylene oxide process by-products

The propylene oxide method is a relatively environmentally friendly process, and its main raw materials are propylene oxide, carbon dioxide and methanol. The process combines propylene oxide with carbon dioxide through a catalytic reaction to produce MMA. Due to the high activity of propylene oxide, side reactions are prone to occur during the reaction, generating some by-products:

• Ethylene glycol: Propylene oxide is prone to ring-opening reaction under hydrolysis or high temperature conditions to produce ethylene glycol. Ethylene glycol is a high value-added compound that can be used in the production of polyester resins or as a solvent. Therefore, some enterprises will choose to recycle ethylene glycol to improve resource utilization.

• Methyl acrylate: During the reaction, propylene oxide may partially react with carbon dioxide to produce methyl acrylate (MA). Although methyl acrylate is also used in some fields, its yield is low and usually needs to be separated and treated by distillation and other methods.

• Other by-products: In the propylene oxide process, some small organic compounds, such as allyl alcohol, formaldehyde, etc., may also be generated. These by-products are produced in a small amount, but they still need to be treated by catalytic oxidation or adsorption to avoid environmental pollution.

3. Production process of other by-products

In addition to the main by-products in the above two processes, some other by-products may also be produced during the MMA production process, such:

• Wastewater: A large amount of wastewater containing organic matter, acidic substances and catalysts will be produced during the production process. These wastewaters need to undergo biochemical treatment, neutralization treatment or membrane separation to ensure that they meet the discharge standards.

• Waste gas: Waste gas containing volatile organic compounds (VOCs) may be produced during the reaction, such as acetone and ethanol. These exhaust gases can be treated by catalytic oxidation, adsorption desorption or incineration to reduce air pollution.

• Solid waste: In the process of processing by-products, some solid waste may be produced, such as catalyst residue and filter residue. These solid wastes need to be sorted, recycled or treated harmlessly to ensure that their impact on the environment is minimized.

4. The importance of by-product management

Although the production process of MMA is efficient, the disposal cost of its by-products is high, and it may cause potential risks to the environment and human health. Therefore, scientific management and effective use of by-products are of great significance for improving production efficiency, reducing costs and achieving green environmental protection. Enterprises can reduce the generation of by-products by optimizing the production process, improving the selection of catalysts, and strengthening the control of reaction conditions; through recycling or harmless treatment technology, the by-products are converted into high value-added products or energy to realize the recycling of resources.

There are many kinds of common by-products in the production process of MMA, and it is difficult to deal with them. Only through technological innovation and fine management can we minimize the waste of the environment and resources and promote the sustainable development of the chemical industry while ensuring product quality.