The Chemo-enzymatic Epoxidation of Tall Oil Fatty Acids: A Solvent-Free Approach

In recent years, there has been a growing interest in developing sustainable and environmentally friendly methods for chemical synthesis. One area of focus is the utilization of renewable resources as starting materials. Tall oil, a byproduct of the pulp and paper industry, has emerged as a promising feedstock due to its high content of fatty acids. These fatty acids can be converted into valuable products through various chemical transformations.

One such transformation is the epoxidation of tall oil fatty acids, which involves the introduction of an epoxide group (-OCH2O-) into the fatty acid structure. Epoxides are versatile intermediates that can be used in the synthesis of a wide range of compounds, including polyols. Polyols, in turn, are essential building blocks for the production of polyurethanes, which find applications in numerous industries, including automotive, construction, and furniture.

Traditionally, the epoxidation of fatty acids has been achieved through chemical methods that often involve the use of hazardous organic solvents and harsh reaction conditions. However, these conventional approaches have several drawbacks, including environmental concerns and the formation of unwanted byproducts. Therefore, there is a growing interest in developing alternative methods that are more sustainable and efficient.

In this context, researchers have investigated the chemo-enzymatic epoxidation of tall oil fatty acids as a greener and more selective approach. The process involves the use of both chemical and enzymatic catalysts to facilitate the epoxidation reaction. Specifically, in-situ generated peroxy fatty acids act as the chemical oxidant, while Novozym® 435, a commercially available lipase catalyst, serves as the enzymatic component.

One notable feature of this approach is that it eliminates the need for derivatization of the carboxylic groups present in tall oil fatty acids. Derivatization typically involves the conversion of carboxylic acids into esters or other reactive intermediates before carrying out the epoxidation. By circumventing this step, the chemo-enzymatic epoxidation process becomes more streamlined and efficient.

Moreover, the use of Novozym® 435 catalyst allows the epoxidation to be performed without the presence of organic solvents. This is a significant advancement, as organic solvents are often associated with environmental and health risks. By eliminating the need for organic solvents, the process becomes more environmentally friendly and safer for the operators.

The researchers reported high degrees of epoxide oxygen content in the developed epoxidized tall oil fatty acids, ranging from 4.49% to 6.00%. This indicates a successful transformation of the fatty acid chains, with a significant portion being converted into epoxide groups. This high epoxide content makes the epoxidized tall oil fatty acids suitable for further synthesis via oxirane ring opening reactions with different alcohols and other compounds.

Polyol synthesis by oxirane ring opening is a well-established process that enables the production of a wide range of polyols with tailored properties. The epoxidized tall oil fatty acids obtained from the chemo-enzymatic epoxidation process can serve as a renewable and sustainable starting material for the production of polyols. By choosing different alcohols for the ring opening reaction, it is possible to obtain polyols with varying structures and functionalities, thereby expanding their potential applications.

In conclusion, the chemo-enzymatic epoxidation of tall oil fatty acids represents a significant advancement in the field of sustainable chemical synthesis. By combining chemical and enzymatic catalysts, this approach allows for the efficient and selective conversion of tall oil fatty acids into epoxidized derivatives. Moreover, the elimination of derivatization steps and the use of organic solvent-free conditions make the process more streamlined, environmentally friendly, and safer. The resulting epoxidized tall oil fatty acids can be further utilized in the synthesis of polyols, offering a renewable and sustainable alternative for the production of polyurethanes and other valuable compounds.