Pyrolysis of Ethanol: Gas and Soot Products Formed

Abstract

Ethanol may be used in diesel−ethanol mixtures in order to decrease soot emissions. Therefore, it is important to evaluate the contribution of ethanol to soot formation. The influence of the temperature on the pyrolysis of ethanol under sooting conditions has been studied. Pyrolysis experiments were carried out in a quartz reactor in the 700−1200 °C temperature range, for an inlet C2H5OH concentration of 50 000 ppm and a gas residence time in seconds of 1706/(T/K) . The concentrations of the gases analyzed in the experiments are shown in this work together with simulations carried out with a literature kinetic model. Theoretical and experimental results present, generally, a good agreement in spite of the model not taking into account the soot formation. Under the studied conditions, soot formation has been observed above 1050 °C. With the soot samples obtained, a study of their reactivity toward O2 and NO has been carried out, and several characterization techniques, such as elemental analysis, Brunauer−Emmett−Teller (BET) surface area, transmission electron microscopy, and X-ray diffraction have been used to study the structural properties of the collected soot samples and relate them to their reactivity. It has been observed that the soot samples formed at higher temperatures exhibit a lower reactivity toward O2 and NO, and the characterization analyses support these results.

Sooting propensity of dimethyl carbonate, soot reactivity and characterization

“…The rise of temperature causes both an increase in soot yield and a decrease in gas yield for the two inlet DMC concentrations evaluated. This is consistent with previous findings [8,9]. An increase in the DMC concentration only affects slightly the soot yield, without notable influence on the gas yield.…”

“…The total time for each experiment was fixed in 3 h, not exceeding an overpressure limit of 1.3 bar inside the reactor in order to avoid perturbations in the experimental set-up. Reactivity experiments were carried out using the facility and following the steps described in previous works [8,9]. Briefly, the reaction takes place within a quartz tubular reactor which has a bottleneck in the middle in which a quartz wool plug is introduced to locate the soot/silica sand mixture (i.e., 10 mg of soot mixed with 300 mg of silica sand (150-300 lm) to prevent soot particle agglomeration and to be able to consider isolated particles), resulting in a thin layer.…”

“…Once the reaction temperature desired is reached, part of the N 2 flow is replaced by the flow of the reactant gas, O 2 or NO, to attain a concentration of 500 ppm of O 2 or 2000 ppm of NO in the total flow rate of 1000 mL (STP)/min. These O 2 and NO concentrations were selected to be consistent with previous experiments [8,9]. The gas products are air-cooled down to room temperature and measured by continuous CO/CO 2 and NO ABB infrared analyzers, which provide uncertainty measurements below 5%.…”

“…1 presents the soot and gas yields (in percentage), as a function of temperature, obtained during the pyrolysis of different inlet DMC concentrations. Both soot and gas yields are defined as the carbon amount in soot and gases, respectively, related to the total carbon amount at the reactor inlet [9]. It is worth to clarify that the gas yield includes the DMC amount that did not react and was found at the reactor outlet.…”

Quantification of polycyclic aromatic hydrocarbons (PAHs) found in gas and particle phases from pyrolytic processes using gas chromatography–mass spectrometry (GC–MS)

“…The analytical method has been optimized for the analysis of PAH formed under pyrolysis processes of gaseous hydrocarbons, such as acetylene and ethylene, using a wide range of well-controlled laboratory conditions. In this respect, it represents an useful complement to the outcomes of experimental works developed in the last years in our research group [27][28][29][30].…”