Amides in Bio-oil by Hydrothermal Liquefaction of Organic Wastes: A Mass Spectrometric Study of the Thermochemical Reaction Products of Binary Mixtures of Amino Acids and Fatty Acids

Abstract

Among biofuels, the bio-oil produced by hydrothermal liquefaction of waste biomass can be considered an alternative to fossil fuels in industry as well as transport and heating compartments. The bio-oil complex composition is directly dependent upon the specific biomass used as feedstock and the process used for the chemical conversion. The coexistence of proteins and lipids can explain, in principle, the high percentage of fatty acid amides found in the produced bio-oil. In the present study, the amides in a sample of bio-oil have been separated by gas chromatography and identified at first on the basis of their electron impact (EI) mass spectra. To distinguish between N-alkyl isomers, standard amides have been synthesized and analyzed. Because the most reasonable origin of fatty acid amides in hydrothermal bio-oils is the condensation reaction between fatty acids and the decarboxylation products of amino acids, a series of model experiments have been carried out by reacting hexadecanoic acid, at high temperature and pressure, with each of the 20 amino acids constitutive of proteins, looking for the formation of fatty acid amides. Remarkably, by such experiments, all of the amides present in the bio-oil have been recognized as hydrothermal coupling compounds of the decomposition products of amino acids with fatty acids, thus allowing for their structural elucidation and, also important, confirming their (bio)chemical origin.

Hydrothermal liquefaction of blackcurrant pomace and model molecules: understanding of reaction mechanisms

“…This result is surprising in view of previous studies from the literature, in which the formation of fatty acid amides by condensation reactions has been observed. 64,65 In our experiments, amides seem to be actually hidden by the peak of linoleic acid. In fact, the extraction of the signal corresponding to the fragment C 2 H 5 NO + (m/z 59), characteristic of long-chain amides (Fig.…”

A Model Study to Unravel the Complexity of Bio‐Oil from Organic Wastes

“…This issue was addressed in our previous studies, in which ad etailed characterisation of an HTL bio-oil from am unicipal organic waste biomass [18,19] was compared with specific studies on the HTL behaviour of representative compoundso ft he main biomass components,n amely,abinary mixture of amino acids and fatty acid [20] and carbohydrates with different degrees of polymerisation. This issue was addressed in our previous studies, in which ad etailed characterisation of an HTL bio-oil from am unicipal organic waste biomass [18,19] was compared with specific studies on the HTL behaviour of representative compoundso ft he main biomass components,n amely,abinary mixture of amino acids and fatty acid [20] and carbohydrates with different degrees of polymerisation.…”

Hydrous pyrolysis of Scenedesmus algae and algaenan-like residue

“…Alkylamides maximize at n-C 16 AA for both the algae and algaenan oil. As mentioned above, we believe that alkylamides are incorporated into the algae from amidation reactions of ammonia with triglycerides (McKee and Hatcher, 2010;Chiaberge et al, 2013). The algae oil, in addition, contains small amounts of C 1 -C 2 quinolines (various isomers) and C 2 -quinoxaline.…”

“…This is an indication that the majority of these derive from the non-algaenan component of whole algae, probably the proteins which contain aromatic amino acids. Likewise, the alkylamides found only in the whole algae oil are derived from non-algaenan components (GC Â GC-TOFMS analysis, Section 3.4.2, shows some are also detected in the algaenan oil), probably alkylamides incorporated into the algae from amidation reactions, e.g., reactions of ammonia with triglycerides (McKee and Hatcher, 2010;Chiaberge et al, 2013). Also notable is the distribution of methyl ketones observed in the algaenan isolate and present in only trace amounts in the whole algae.…”