Green Chemistry for Sustainable Materials: The Role of Triglycerides

The term triglyceride is a big word with a simple meaning: three fatty acids on a glycerin backbone.   When triglycerides are mentioned, many people think of blood test values or cholesterol. However, in the industrial chemical market, triglycerides are valuable commodities, serving as complex building blocks with diverse applications that contribute to biobased chemistry for sustainable materials.

Triglycerides are fats and oils, known as lipids, which are insoluble in water but soluble in organic solvents. Fats are solid at room temperature, while oils are liquid. Historically, fats and oils were used for fuel and lubrication, with Rudolf Diesel designing his engine to run on peanut oil. They were also used in oil lamps, heating devices, and soap making. The saponification process of fats and oils with sodium hydroxide not only produced soap but also glycerin, which had multiple uses and benefits. However, the discovery of petroleum dramatically shifted the chemical industry due to economic reasons and availability.

Triglycerides can be broken down into fatty acids and glycerin, with the blend of fatty acids giving each triglyceride its unique properties. Triglycerides contain saturated and unsaturated fatty acids.  Fatty acids vary in carbon number and double bond presence, with the C18 oleic acid being one of the most valuable.  The double bonds in these acids provide reactive sites for adding functional groups, such as epoxide groups, which leads to the production of epoxidized vegetable oil and numerous industrial applications.

Today, biodiesel and renewable diesel are significant consumers of triglycerides. Biodiesel is a trans-esterified fat or oil with methanol.  Another name for biodiesel is methyl soyate (biodiesel produced from soybean oil.)  The by-product of this process is glycerin.  Biodiesel offers many advantages over petroleum diesel in that it has greater lubricity than petroleum diesel.  Petroleum diesel requires sulfur to be added to give the needed lubricity.  A 5% addition of biodiesel to petroleum diesel allows for the elimination of sulfur and a cleaner burning diesel engine.  Biodiesel also reduces particulate matter, carbon monoxide emissions and decreased hydrocarbon emissions.   Up to 20% biodiesel can be added to petroleum diesel without engine modification.  Higher biodiesel concentrations can lead to significant emission reductions. Another point worth mentioning is that the dramatic rise in biodiesel production since the early 2000s has led to the mothballing of all synthetic glycerin plants using petroleum. This is due to the large volume of glycerin produced as a byproduct of biodiesel. However, it’s important to note that, given current economic conditions, biodiesel is a more expensive fuel than petroleum diesel.

Renewable diesel and sustainable aviation fuel (SAF) are newer developments. While renewable diesel can replace 100% of regular diesel, SAF can only replace up to 50% of aviation fuel without engine changes. Unlike biodiesel, the renewable diesel process does not produce glycerin, impacting several applications economically and in supply. However, it does produce bio-naphtha, which can replace petroleum-based naphtha, contributing to renewable content of naptha-derived products (such as gasoline) based on mass balance.

Overall, triglycerides from renewable sources present endless opportunities for innovation in green chemistry for biobased materials. By exploring these sustainable alternatives, we can reduce our reliance on petroleum, lower our carbon footprint, and create a more sustainable future. The versatility of triglycerides as a building block is only limited by our imagination, paving the way for a greener and more sustainable chemical industry.