The sensitizing effects of NO2 and NO on methane low temperature oxidation in a jet stirred reactor

Y Song,E Assaf,F Battin-Leclerc,M.U Alzueta,A Stagni,O Herbinet,L Marrodán,C Fittschen,N Vin,T Faravelli

doi:10.1016/j.proci.2018.06.115

Abstract

Abstract The oxidation of neat methane (CH 4 ) and CH 4 doped with NO 2 or NO in argon has been investigated in a jet-stirred reactor at 107 kPa, temperatures between 650 and 1200 K, with a fixed residence time of 1.5 s, and for different equivalence ratios (Φ), ranging from fuel-lean to fuel-rich conditions. Four different diagnostics have been used: gas chromatography (GC), chemiluminescence NO x analyzer, continuous wave cavity ring-down spectroscopy (cw-CRDS) and Fourier transform infrared spectroscopy (FTIR). In the case of the oxidation of neat methane, the onset temperature for CH 4 oxidation was above 1025 K, while it is shifted to 825 K with the addition of NO 2 or NO, independently of equivalence ratio, indicating that the addition of NO 2 or NO highly promotes CH 4 oxidation. The consumption rate of CH 4 exhibits a similar trend with the presence of both NO 2 and NO. The amount of produced HCN has been quantified and a search for HONO and CH 3 NO 2 species has been attempted. A detailed kinetic mechanism, derived from POLIMI kinetic framework, has been used to interpret the experimental data with a good agreement between experimental data and model predictions. Reaction rate and sensitivity analysis have been conducted to illustrate the kinetic regimes. The fact that the addition of NO or NO 2 seems to have similar effects on promoting CH 4 oxidation can be explained by the fact that both species are involved in a reaction cycle interchanging them and whose result is 2CH 3 + O 2 = 2CH 2 O + 2H. Additionally, the direct participation of NO 2 in the NO 2 + CH 2 O = HONO + HCO reaction has a notable accelerating effect on methane oxidation.

Highlights

The limited fossil fuel resource and its harmful effects on the climate have increased the interest for environmentally friendly fuels
The oxidation of neat methane (CH4) and CH4 doped with NO2 or NO in argon has been investigated in a jet-stirred reactor at 107 kPa, temperatures between 650 and 1200 K, with a fixed residence time of 1.5 s, and for different equivalence ratios (φ), ranging from fuel-lean to fuel-rich conditions
In the case of the oxidation of neat methane, the onset temperature for CH4 oxidation was above 1025 K, while it is shifted to 825 K with the addition of NO2 or NO, independently of equivalence ratio, indicating that the addition of NO2 or NO highly promotes CH4 oxidation

Summary

Introduction

The limited fossil fuel resource and its harmful effects on the climate have increased the interest for environmentally friendly fuels. Biomass seems to be a promising fuel source due to its sustainability, secure supply and low threat to the environment. Produced from the biomass anaerobic digestion, the so-called “biogas”, consists mainly of methane (CH4) and carbon dioxide (CO2) with trace amounts of nitrogen and sulfur compounds. Biogas plays an important role as potential renewable gas-phase fuel. The main nitrogen compound present in biogas is ammonia, which could convert to NO in the presence of oxygen even at low temperatures. The mutual effects of CH4/NOx or CH4/NH3 have attracted considerable attention in the past decade

Objectives

Methods

Results

Discussion

Conclusion