Flash pyrolysis of silicon-bound hydrocarbons

Abstract

Curie-point flash pyrolysis-gas chromatography/mass spectrometry of n-octadecane, n-propylbenzene and n-propylcyclohexane chemically linked to silica has been performed in order to gain a better understanding of the mechanism of flash pyrolysis by which hydrocarbons are generated from kerogens. The major products result via a 6-membered ring rearrangement involving the Si-O-C linkage and from cleavage of C-C bonds allylic to primary or secondary alkyl radicals.

Stable carbon isotopic characterisation of free and bound lipid constituents of archaeological ceramic vessels released by solvent extraction, alkaline hydrolysis and catalytic hydropyrolysis

“…This feature is not an artefact of the hydropyrolysis procedure since no alkyl chain lengths greater than n-C 18 were produced from hydropyrolysis of either stearic or oleic acid model compounds. These longer-chain n-alkanes (>C 18 ) have not been observed before in pyrolysates of archaeological potsherds or experimental chars and are more typical of molecular signals produced from pyrolysis of aliphatic biopolymers or immature geo-polymers [35]. Their origin is uncertain but the presence in the modern milk pot implies they can be formed rapidly during cooking (and charring) events, as previously suggested [17], as well from diagenetic reactions occurring in the geo-sphere after burial.…”

“…This product distribution was interpreted as resulting from fragmentation of an aliphatic network polymer formed by polymerisation of adsorbed lipids, most likely formed during the cooking process rather than post-depostional. Yet the degree of polymerisation that had occurred in these samples is not clear, as similar hydrocarbon distribution patterns may also be obtained by flash pyrolysis of simple model silicon-bound hydrocarbons [18]. Also, the presence of an insoluble organic fraction has been observed in storage amphorae [14], which would suggest that fatty acids could equally become ester bound to the ceramic matrix during post-deposition or by stronger covalent linkages, as it is unlikely that these particular sherds were exposed to excessive heat.…”