Green synthesis of trimethylolpropane triisostearate and triisooleate for usage as bio-lubricants

Authors: Sarker, Majher; Ngo, Helen; Sharma, Brajendra - Bk; Wagner, Karen; Jones, Kerby; Powell, Michael

Submitted to: Tribology International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2023
Publication Date: 5/26/2023
Citation: Sarker, M.I., Lew, H.N., Sharma, B.K., Wagner, K., Jones, K.C., Powell, M.J. 2023. Green synthesis of trimethylolpropane triisostearate and triisooleate for usage as bio-lubricants. Tribology International. https://doi.org/10.1016/j.triboint.2023.108649.
DOI: https://doi.org/10.1016/j.triboint.2023.108649

Interpretive Summary: In this study, renewable resources have been used to produce potential bioproducts to replace fossil-based products. Fossil-based products raise concerns regarding biodegradability and toxicity being harmful to the environment. Under the current investigation, two triesters called TMP-ISA and TMP-IOA have been synthesized in a green process from naturally derived free fatty acid, i.e., oleic acid. This synthesis process can use reusable catalyst and generates very little/no waste and thus becomes very cost-effective and eco-friendly. TMP-ISA and TMP-IOA have been characterized with different analytical methods such as NMR, FTIR, GC-MS, and LC-MS. Physicochemical and tribological properties such as density, viscosity, oxidative stability, and cold temperature properties of TMP-ISA and TMP-IOA reveal that these compounds can be potentially used as bio-lubricants.

Technical Abstract: Two methyl-branched triesters, trimethylolpropane-triisostearate (TMP-ISA) and trimethylolpropane-triisooleate (TMP-IOA) have been synthesized via esterification of trimethylolpropane with isostearic-acid and isooleic-acid, respectively. Isostearic-acid and isooleic-acid have been previously produced through the skeletal-isomerization reaction of naturally derived oleic acid using a reusable zeolite catalyst. TMP-ISA and TMP-IOA are characterized by FTIR, NMR, GC-MS, and LC-MS. Physicochemical and tribological analysis reveal that TMP-ISA and TMP-IOA exhibit higher oxidative stability, viscosity index, anti-wear property, and better cold flow properties when compared to high-oleic sunflower oil or polyalphaolefin, a common lubricant base oil. Lubricant property analysis of blends of TMP-ISA or TMP-IOA with high-oleic sunflower oil or polyalphaolefin demonstrates their miscibility and potential applications as biolubricants.