Kinetics of Combustion. Relation to Emission Flame Spectroscopy

A study of adulteration in gasoline samples using flame emission spectroscopy and chemometrics tools

“…Low signal intensity is observed at 400 nm characteristic of the presence of radical CH*. 35,36 The main difference observed between samples doped with rubber solvent and those doped with kerosene and turpentine is due to the chemical composition since the former is characterized as a light aliphatic solvent while the latter are considered heavy aliphatic solvents. The separation between these classes of samples is strongly influenced by the presence of C 2 * radicals in the flame.…”

Differentiation of Gasoline Samples Using Flame Emission Spectroscopy and Partial Least Squares Discriminate Analysis

“…The combustion of these samples led to the formation of chemiluminescent radicals and soot, which are easily detected through FES, with the majority of these radicals being due to intermediated radicals, generally diatomic molecules, aforementioned and the most intense emissions being due to C 2 *, CH*, and OH* species. 34 From the PLS-DA model, it was possible to produce a loadings graph presented in Figure 3, where it shows the interval correspondent to a larger contribution for the separation of groups in the second LV, which occurs in the range between 500 and 600 nm.…”

“…With the development of molecular spectroscopy, currently, it is possible to characterize the flame through the formation of excited radicals (indicated by *), highlighting the species C 2 *, CH*, and OH* with concentrated emissions predominantly in the internal cone of the flame when the samples are analyzed through this technique . Therefore, the distribution of energy of the species present in the flame can be carried out through band systems frequently described in the literature; − however, usually the spectrum obtained through the burning of gasoline is quite difficult to study once it is not possible to differentiate the bands, because they are usually overlapped. Thus, the employment of an appropriate statistical treatment combined with conventional methods is commonly presented as a proposal for data treatment.…”

“…Recently, several studies have been described in the literature using FES with different applications. The information obtained from spectral data of intermediary species, which are formed during the burning process, have allowed for the use of FES in studies of kinetic mechanisms applied to processes that involve combustion. − …”

“…The mapping of radicals, such as CH*, have been used to determine the temperature of the flame as a result of the intense emission band in the region of the visible ultraviolet because of the 2 ∑ – → 2 Π and 2 Δ → 2 Π transitions . The Swan band system for the C 2 * radical is frequently used as a thermometer to estimate the temperature of the gas in the corresponding emission region. ,− …”