熱分解顕微FTIRによるケロジェンの研究

概要

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It is generally accepted that most petroleum hydrocarbons are generated from kerogen by cracking of alkyl chains. Infrared spectroscopy can analyze the hydrocarbon generation by decreasing absorbance bands of alkyl CH_2 stretching vibration (2930cm^<-1>) during heating experiments of kerogen samples. The objective of this paper is to study hydrocarbon generation characteristics of each maceral of immature kerogen using micro-FTIR equipped with a heating unit, and to describe kinetics of kerogen decomposition. As a result of heating from 30 to 550℃ at several different heating rates, the temperature of the maximum point in decreasing rate of the alkyl CH_2 absorbance is defined as "IR2930Tmax". IR2930Tmax values appear about 300℃ (10℃/min). This evidence means that maximum hydrocarbon generation occurs around 300℃ by decomposition of alkyl chains. Activation energy distribution at the cracking of alkyl CH_2 chains falls between 35 and 60kcal/mol (maximum values between 45 and 50kcal/mol) at the frequency factor A=10^<16>(1/s). This activation energy value seems to be too low for the direct cracking of alkyl chains, and is possible related with free radical reaction mechanism.
日本有機地球化学会の論文
1998-12-25