Gas and soot products formed in the pyrolysis of acetylene–ethanol blends under flow reactor conditions

The present paper reports a laboratory study on the pyrolysis of different blends containing acetylene, known as an important soot precursor, and ethanol, regarded as an appropriate additive to conventional fuels aiming to diminish the emission of pollutants coming from combustion processes. Pyrolysis experiments of acetylene–ethanol blends, for a total initial concentration of reactants of 50,000 ppm, with variable volume percentages of ethanol between 0 and 40% with respect to the total concentration of reactants, have been carried out in a quartz flow reactor working in a temperature range of 975–1475 K. The influence of both pyrolysis temperature and ethanol concentration in the blend on the gas and solid products has been evaluated. As the reaction temperature is increased, the soot production is higher and yield to carbonaceous gas products decreases. It is noticed that the presence of ethanol inhibits the production of soot and the diminution of soot formation does not present a linear dependency with the ethanol concentration; the influence is comparatively stronger when adding small amounts of ethanol. The analysis of the gas products reveals that increasing the ethanol percentage in the blend causes an increase of the concentration of some intermediates such as ethylene, ethane, methane or benzene, pointing to a variation of the reacting species which could prevent soot formation. A literature detailed gas phase kinetic mechanism including reaction subsets for acetylene and ethanol conversion has been used to simulate the experimental results. This theoretical study has been carried out with the purpose of analyzing the trends of the evolution of gas products and getting a better understanding of the gas phase processes involved in the pyrolysis of the different blends, although soot formation is not included.