Bio-based hydraulic oil from plant residues

Environmentally friendly lubricants are increasingly in demand, especially in the hydraulics sector. This is due to the higher risk of lubricants contaminating soil or water. Companies in this sector are therefore increasingly turning to bio-based, biodegradable hydraulic oils.

Vegetable oils are an obvious alternative to conventional mineral oil-based lubricants. However, their use quickly reaches its limits in practice. Vegetable oils are also in high demand from the food and fuel industries, which means they are associated with higher costs. In addition, they have insufficient technical properties and are only suitable for high-performance applications to a limited extent.

Ester oils as a high-performance alternative

Ester oils based on branched polyols such as neopentyl glycol, pentaerythritol, or trimethylpropane (TMP) offer a significantly better property profile. They combine high thermal stability with excellent flow behavior at low temperatures. Another advantage is their outstanding tribological properties and good biodegradability. TMP esters – especially TMP trioleate – play a special role here. They combine technical performance with environmental compatibility and are therefore also suitable for demanding high-performance applications, for example in hydraulics.

However, the production of TMP esters is currently still very complex, energy-intensive, and costly. The conventional process for producing ester oils consists of several process stages at temperatures of up to 250 °C and long reaction times. Chemical catalysts and additives are also used to prevent unwanted by-products. This complex manufacturing process currently still poses a challenge to the use of TMP esters as a basis for sustainable lubricants.

Enzymatic processes for the production of hydraulic oils

This is precisely where the "EnTE" project comes in. The aim is to develop an alternative, bio-based, and resource-efficient manufacturing process for high-performance TMP esters. The focus is on enzymatic esterification: free fatty acids and TMP form a high-quality ester oil with the help of lipases.

Soapstock, a by-product of oil refining, is a suitable raw material for this purpose. It is rich in free and saponified fatty acids, making it ideal for enzymatic esterification. Its use therefore also enables the sensible recycling of a residual material.

By specifically adjusting the molecular profile – for example, through the use of different fatty acids – the ester oils are to be adapted to various technical requirements. This makes them suitable for high-performance applications in the hydraulic sector. The project team is investigating both batch and continuous processes. At the same time, the experts are optimizing the enzyme catalyst used and developing regeneration strategies to make the process economically viable.

Fraunhofer IVV: Process understanding up to industrial implementation

Fraunhofer IVV contributes its comprehensive expertise in the development of enzyme-catalyzed processes to the project. The technology experts characterize the underlying mass transport processes in detail and determine the relevant reaction kinetics. This is supplemented by a comprehensive chemical and physical evaluation of the bio-based lubricants produced. Finally, the process for manufacturing TMP esters is transferred to an industrial scale and validated under practical operating conditions.

With the "EnTE" project, Fraunhofer IVV is pursuing the goal of establishing a highly innovative and economically attractive manufacturing process that combines resource-saving raw materials with the highest performance requirements. The project is thus making a decisive contribution to the industrial bioeconomy and setting new standards for the biotechnological production of lubricants.