Terpene speciation: Analytical insights into the oxidation and pyrolysis of limonene and 1,8-cineole via molecular-beam mass spectrometry

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2024-11-23 DOI:10.1016/j.combustflame.2024.113854

Thomas Bierkandt, Nina Gaiser, Jasmin Bachmann, Patrick Oßwald, Markus Köhler

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引用次数: 0

Abstract

Comprehensive speciation datasets for the stoichiometric oxidation and pyrolysis of the two monoterpenes limonene (C₁₀H₁₆) and 1,8-cineole (C₁₀H₁₈O) are measured in an atmospheric laminar flow reactor using electron-ionization molecular-beam mass spectrometry. This setup allows direct sampling from the reactive flow and preserves the actual gas composition. Furthermore, clear determination of the exact elemental composition of the formed species is possible with the used time-of-flight mass spectrometer. Limonene is a monocyclic terpene and 1,8-cineole is a saturated bicyclic terpene ether and both terpenes might be potential biofuel candidates. Focus in this study is the intermediate temperature region between 673 and 1173 K to obtain insights into the first fuel decomposition steps and the formation of typical soot precursors. The obtained mole fraction profiles for over 40 species in each of the investigated terpenes are a first step for future development and validation of chemical kinetic combustion mechanisms. While the overall species pool is similar, significant concentration differences can be observed for certain combustion intermediates. For limonene, larger quantities of C₈–C₁₀ hydrocarbons are detected and most of them are probably substituted benzenes or cyclohexadienes formed from hydrogen abstraction. Some reaction steps in the decomposition of limonene may also involve initial isomerization of the fuel molecule. In contrast, direct formation of C₇H₁₁ radicals and acetone (C₃H₆O) is identified as an important decomposition step of 1,8-cineole. C₇H₁₁ is then a source of toluene (C₇H₈) and cyclohexadienes (C₆H₈). Generally, a higher sooting propensity of limonene compared to 1,8-cineole can be expected due to the higher concentrations of polycyclic aromatic hydrocarbons (PAHs) in the investigated temperature range. During limonene oxidation, formation of oxygenated species larger than the fuel molecule are observed and might represent carbonyls or cyclic ethers from the first oxygen addition due to low-temperature chemistry.

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萜烯分类：通过分子束质谱分析深入了解柠檬烯和 1,8-蒎烯的氧化和热解过程

在大气层流反应器中使用电子电离分子束质谱法测量了柠檬烯（C10H16）和 1,8-蒎烯（C10H18O）这两种单萜烯按化学计量氧化和热解的综合标样数据集。这种装置可以直接从反应流中取样，并保留实际的气体成分。此外，利用所使用的飞行时间质谱仪还可以清楚地确定所形成物种的确切元素组成。柠檬烯是一种单环萜烯，1,8-蒎烯是一种饱和双环萜烯醚，这两种萜烯都可能成为潜在的生物燃料候选物质。本研究的重点是 673 至 1173 K 之间的中间温度区域，以深入了解燃料的最初分解步骤和典型烟尘前体的形成。所获得的每种萜类化合物中 40 多种物质的分子分数剖面图是未来开发和验证化学动力学燃烧机制的第一步。虽然总体物种库相似，但可以观察到某些燃烧中间产物的浓度存在显著差异。就柠檬烯而言，检测到了较多的 C8-C10 碳氢化合物，其中大部分可能是由氢抽取形成的取代苯或环己二烯。分解柠檬烯的某些反应步骤也可能涉及燃料分子的初始异构化。相反，直接形成 C7H11 自由基和丙酮（C3H6O）被认为是 1,8-蒎烯的一个重要分解步骤。然后，C7H11 成为甲苯（C7H8）和环己二烯（C6H8）的来源。一般来说，由于多环芳烃（PAHs）在所研究的温度范围内浓度较高，因此与 1,8-蒎烯相比，预计柠檬烯会有更高的发烟倾向。在柠檬烯氧化过程中，可以观察到比燃料分子更大的含氧物质的形成，由于低温化学作用，这些物质可能是第一次加氧产生的羰基或环醚。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.