Influence of hydrogen and oxygen on the initial steps of soot formation

• Applicant: Professor Dr. Christof Schulz
• Subject Area: Energy Process Engineering
• Term: from 2015 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 275255277

Carbon nanoparticles play an important role as combustion-generated pollutants as well as important industrial products. The understanding and modeling of their formation pathways, therefore, is of high interest. In particular, hydrogen and oxygen play an important role inthe underlying reactions. Systematic studies on the mechanistic details, however, are scarce. Therefore, the influence of molecular and bonded hydrogen as well as the influence of molecular Oxygen was as well as oxygenate additives on particle induction times, particle formation rates, particle volume fractions, particle morphology, as well as on reaction channels leading to soot will be studied using a close interaction of experiments under a wide range of reactionsconditions and modeling. The proposed project systematically extends thematically and methodically the work carried out in the first project period and builds on the experimental capabilities developed and demonstrated in the first period. As precursor systems, ethylene,acetylene, and benzene (with and without the addition of the oxygenates methanol, n-butanol and furans) will be studied as representative hydrocarbon classes with variable C/H ratios underpyrolytic and mildly oxidative conditions. Studies have shown that oxygenated fuels and the admixture of oxygenated fuel components leads to a reduction of the soot volume fraction and an increase in the production of smaller particles. At flame conditions, molecular andbonded oxygen can influence soot formation by increasing radical concentrations and initial heat release or by oxidation reactions of soot precursors and soot particles compared to pyrolysis conditions. Therefore, soot formation with and without additives will be studied byusing complementary techniques such as shock tubes (pyrolytic and oxidative), a burnt-gas flow reactor (pyrolytic) and a McKenna burner (oxidative) that cover studies under a wide range of reaction conditions. Through these combined approaches, all stages of soot formation can be investigated: shock tubes coupled with in situ, online, and offline techniques provide well-defined reaction conditions where the gas-phase composition and soot volume fractions andparticle sizes can be determined with ultra-high time resolution. The burnt-gas flow and McKenna reactors enable the investigation of processes on longer reaction times and provide good sampling possibilities throughout the different steps of the soot formation. Allmeasurements will be related to theoretical studies and modeling. This project is based on a close collaboration between a German and a Russian research group. The latter will apply for additional funding from the Russian side.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research, until 3/2022
• Co-Investigator: Dr. Mustapha Fikri
• Cooperation Partner: Professor Dr. Alexander V. Eremin, until 3/2022