Background

Radical trapping antioxidants (RTAs), which slow the oxidative degradation of hydrocarbon-based products, are widely used as additives in oils, lubricants, plastics, and fine chemicals and make up a large segment of the $15B global lubricants additives market. Recent work by a Queen’s University researcher has resulted in the development of novel heterocyclic-containing diarylamine RTAs that have superior reactivity over industry standard diphenylamines, such as 4,4′-dialkyldiphenylamine.

Technology Overview

Previously, the researcher has described the development of phenolic-like antioxidants, 3-pyridinols and 5-pyrimidinols, that have rate constants for reactions with peroxyl radicals that are up to 88-fold higher than that of α-tocopherol, making them the most effective peroxyl-radical-trapping antioxidants described to date. In this earlier work, the antioxidant design strategy centered on the incorporation of nitrogen atoms in the phenolic ring, which raised the oxidation potential of the phenols, allowing them to be substituted with stronger electron-donating groups (i.e., N,N-dialkylamino), further weakening the O−H bond but not at the expense of their one-electron oxidation by O₂.

Figure 1: Hydroperoxide formation in the autoxidation of n-hexadecane

Using this same strategy, the researcher has developed analogues of diphenylamine (bearing either ring carbons or nitrogens) that are characterized by oxidation potentials that increase systematically with the number of N atoms from less than 1 V to >1.5 V (vs NHE), while their reactivity to peroxyl radicals decreases only 6-fold at most (from 1.8 × 105 M⁻¹ s⁻¹ for 2 to 3.0 × 104 M⁻¹ s⁻¹ in chlorobenzene at 37 °C).

This permitted the design of pyridyl and pyrimidyl analogues of the very electron-rich diphenylamine (4,4′-(N,N-dimethylamino)-diphenylamine) that are stable in air and that react with peroxyl radicals with temperature-independent rate constants up to 200-fold greater than those measured for α-tocopherol under the same conditions.

Benefits

These novel heterocyclic-containing diarylamine RTAs offer unprecedented inhibition of the autoxidation process and, therefore, will enable the development of longer lasting oils, lubricants, etc.

Applications

Potential applications include additives for automotive and industrial oils, lubricants, etc. and in plastics and other products that are susceptible to oxidative damage.

Opportunity

The university are looking to out license the technology to industrial partners who are interested in developing and commercializing the technology.

Novel Diarylamine-Based Antioxidants with Superior Reactivity

Patents

IP Status

Seeking