Semi‐volatile and volatile compounds formed by degradation of triglycerides in a pressurized reactor

Abstract

The products formed during precombustion reactions of several saturated and nnsaturated triglyeerides upon their injection into a reactor, simulating conditions that exist in a diesel engine, were collected. Two traps were employed in order to distinguish between volatile and semi-vulatile components. The resulting samples were analyzed with gas chromatography-mass spectrometry techniques. Various aliphatic and aromatic hydrocarbons were detected as major degradation products. Oxygenated degradation products were found in smaller numbers. Differences observed in the samples compared to previous work are attributed to the higher temperature used in the present study (450°C vs. 400°C). The environment (air or nitrogen) had considerable influence on product formation. The number of components was less for samples of tripalmitin, tristearin and triolein reacted under nitrogen than under air; but more components were formed from trilinolein and trilinolenin under nitrogen atmosphere than under air.

Precombustion of fatty acids and esters of biodiesel. A possible explanation for differing cetane numbers

“…Other possible reactions include decarboxylation (liberation of CO 2 ), oxidation, ring closure, cyclization, aromatization, and dehydrogenation. These reactions had also been observed previously in studies on the precombustion of triglycerides (9)(10)(11). Evidence for these reactions is presented here.…”

“…These classes of compounds include aliphatic hydrocarbons (saturated and unsaturated) as well as straightchain and branched and likely cyclic species, aldehydes, ketones, aromatic hydrocarbons with aliphatic side chains, and shorter-chain esters. Interestingly, substituted furans were observed as well; these compounds had not been observed in the prior precombustion experiments on triglycerides (9)(10)(11). On the other hand, furans have been shown to arise during other combustion experiments with fossil fuels and biomass (15).…”

“…Full quantitation of the individual species was not conducted, as was true also for the previous precombustion experiments on triglycerides, where compounds were reported in quantitation ranges (9)(10)(11). Quantitation ranges are reported here again.…”

“…In previous work, we analyzed pure triglycerides, such as tripalmitin, tristearin, triolein, trilinolein, and trilinolenin (9)(10)(11). In an initial study (9), at 400°C in air or nitrogen, mainly fatty acids, various aliphatic hydrocarbons, and other compounds, such as aldehydes, were detected.…”

“…Component patterns were largely independent of reaction conditions and starting materials. In a second study (10), where the precombustion products were separated as volatiles or semivolatiles, and the conditions were 450°C in air or nitrogen, unsaturated aliphatic hydrocarbons, unsaturated aldehydes, various aromatics, and polyaromatics were detected. Here the atmosphere had considerable influence on product formation.…”