O2酸化によるスギ炭からの仮導管炭素の分離

Abstract

組織成分すなわち木炭の仮導管壁や細胞間層の酸化反応性の差異を利用して、炭素質の仮導管の針葉樹を炭から分離してきたが、650?800度Cで熱処理されたスギ炭を、針葉樹炭の酸化機構を明らかにするために、10%O2?90%N2混合ガスを流しながら300?360度Cの温度域で酸化した。結果は以下の通りである。SEM(走査型電子顕微鏡)観察により、炭の酸化は炭素化されたリグニン主成分の炭から成る細胞間層の部分で、選択的に起こることが分かった。炭化された細胞間層の酸化は、仮導管の壁孔の周辺域から著しく進行した。酸素ガスを用いたスギ炭の燃焼は、消失量が30%以降は、1次反応に従う。巨視的には非選択的な酸化により、スギ炭燃焼の消失量が50%を越えても、仮導管の形状が保たれていた。消失量が50%近くまで進んだ酸化炭を、水酸化ナトリウム水溶液に浸漬すると、仮導管炭素単位で分散した。

Carbonaceous tracheids were separated from charcoal of needle-leaf trees by taking advantage of difference in oxidative reactivity of the constituents i.e., walls in tracheid and intercellular layers of the charcoal. Cryptomeria charcoal heat treated at 650 - 800 C was oxidized at temperatures ranging from 300 to 360 C in a stream of ten percent O2 - 90 percent N2 gas to clarify the oxidation mechanism of charcoal from needle-leaf trees. The results are as follows: it was found by SEM (Scanning Electron Microscope) observation that oxidation of the charcoal occurs selectively at the portion of intercellular layers of carbon derived from lignin rich component carbonized. The oxidation of the carbonaceous intercellular layers proceeded predominantly from circumferences of pits of tracheid walls. The burn-off of the charcoal with O2 gas obeyed first order kinetics after 30 percent of burn-off. The shape of the tracheids was maintained more than 50 percent burn-off of the charcoal because of non-selective oxidation on the macroscopic scale. When the charcoal oxidized to 50 percent of burn-off was immersed in a aqueous solution of sodium hydroxide, it was dispersed into small hollow fibers of the tracheid carbon.