Baehr Clarissa, Smith Gavin J, Sleeman Daniel, Zevaco Thomas A, Raffelt Klaus, Dahmen Nicolaus
Institute of Catalysis Research and Technology (IKFT) Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen Germany
RSC Adv. 2022 Mar 4;12(12):7374-7382. doi: 10.1039/d1ra08899h. eCollection 2022 Mar 1.
Aldehydes and ketones are known to play a role in the aging process of pyrolysis oil and generally, aldehydes are known for their high reactivity. In order to discern in pyrolysis oil the total aldehyde concentration from that of the ketones, a procedure for the quantification of aldehydes by H-NMR was developed. Its capability is demonstrated with a hardwood pyrolysis oil at different stages of the aging process. It was treated by the Accelerated Aging Test at 80 °C for durations of up to 48 h. The aldehyde concentration was complemented by the total concentration of carbonyls, quantified by carbonyl titration. The measurements show, that the examined hardwood pyrolysis oil contained 0.31-0.40 mmol g aldehydes and 4.36-4.45 mmol g ketones. During the first 24 h, the aldehyde concentration declined by 23-39% and the ketone concentration by 9%. The rate of decline of aldehyde concentration slows down within 24 h but is still measureable. In contrast, the total carbonyl content does not change significantly after an initial decline within the first 4 h. Changes for vinylic, acetalic, phenolic and hydroxyl protons and for protons in the -position to hydroxy, ether, acetalic and ester groups were detected, by H-NMR. In the context of characterizing pyrolysis oil and monitoring the aging process, H-NMR is a reliable tool to assess the total concentration of aldehydes. It confirms the reactivity of aldehydes and ketones and indicates their contribution to the instability of pyrolysis oil.
已知醛类和酮类在热解油的老化过程中起作用，一般来说，醛类因其高反应活性而闻名。为了区分热解油中醛类的总浓度和酮类的总浓度，开发了一种通过氢核磁共振（H-NMR）定量醛类的方法。在老化过程的不同阶段，用一种硬木热解油展示了该方法的能力。将其在80℃下进行加速老化试验，持续时间长达48小时。通过羰基滴定法定量的羰基总浓度补充了醛类浓度。测量结果表明，所检测的硬木热解油含有0.31 - 0.40 mmol/g的醛类和4.36 - 4.45 mmol/g的酮类。在最初的24小时内，醛类浓度下降了23 - 39%，酮类浓度下降了9%。醛类浓度的下降速率在24小时内减缓，但仍可测量。相比之下，在最初的4小时内羰基总含量有所下降，之后变化并不显著。通过氢核磁共振检测到了乙烯基、缩醛、酚羟基和羟基质子以及与羟基、醚、缩醛和酯基团相邻位置质子的变化。在表征热解油和监测老化过程的背景下，氢核磁共振是评估醛类总浓度的可靠工具。它证实了醛类和酮类的反应活性，并表明了它们对热解油不稳定性的影响。
