Dodecane decomposition in a radio-frequency (RF) plasma reactor

The research outlined here includes a study of the production of carbon black (CB) in an inductive plasma reactor using dodecane (C12H 26) as starting material. The objective of this work is to further investigate the production of carbon black and valuable gaseous by-products using radio frequency (RF) inductively coupled plasma technology. The method used in this research is based on the evaporation and reaction of a long-chain hydrocarbon molecule using a RF plasma torch working with inert or reductive plasma gases. The source of raw material was dodecane (C12H26) and plasma gas combinations involving argon-helium (inert plasma gas) and argon-hydrogen (reductive plasma gas) were used in the experimental work.; A series of theoretical thermodynamic studies of the Ar-C-H and Ar-C-H-He systems were conducted to predict the dominant species prevailing at equilibrium under several operating conditions. Additionally, a kinetic approach involving 159 reactions and 42 chemical species was employed in an effort to understand the pyrolysis process and carbon black production at the associated time scales.; Also, a hydrodynamic characterization of the liquid atomizer was conducted in order to determine the region in the plasma torch in which the optimal atomization conditions are found. The advantages of this experimental process based on the results of a laser particle size analyzer are: (1) it facilitates the evaluation of the effect of the operating conditions on the atomization process, and (2) it assists in determining the properties of the liquid influencing the quality of the atomization. Finally, a study of the vaporization process of the drops in the plasma conditions was performed.; A thorough statistical experimental design was undertaken to investigate the influence of the different operational conditions in the reactor following the experimental tests. Parameters, such as the feed rate of dodecane, the reactor pressure, the plate power applied to the plasma torch, and the composition of the plasma gas on the production of carbon black and gaseous acetylene-like compounds were investigated, and the effects of these conditions are discussed. In this study, the relationships between the plasma operating conditions and the structure of the carbon black obtained during the plasma process are presented. Morphological analysis of the solid product using Transmission Electron Microscopy (TEM) indicates that a high plasma temperature is the most important factor affecting the final morphology of the carbon black formed during the reaction. Carbon black with average particle size of 10--30 nm and specific surface of 130 m2/g was obtained. Morphological analyses demonstrate the presence of new structures ranging from carbon black to fullerenes and including certain "graphitized" carbon molecule. American Standard Testing Methods (ASTM) were carried out to characterize the carbon black produced.; From the technological standpoint, the findings of this research show that thermal plasma processing is an efficient and safe procedure (average energy efficiency of the torch estimated as 78%) that enables not only the production of special carbon black products but also facilitates the decomposition of dodecane with reduced emission of contaminants. The environmentally friendly and minimal contaminant effects of this reaction allow us to predict that this technology will become one of the most promising new processes to produce carbon black with particular and desirable characteristics using an efficient and improved method.