Pyrolysis and coking behavior of CxHy with different structures in microchannel continuous flow reactor

Abstract

Coking with carbon deposition in hydrocarbon fuel (CxHy) pyrolysis at high temperature is a serious problem to be considered. In this work, single component CxHy with different structures was used as the probe of the carbon deposition. Thirteen simple and representative of alkanes, cycloalkanes, aromatics and O-containing CxHy were selected as the model compounds to decompose and coking in microchannel continuous flow reactor under the same conditions. The distributions of gas, liquid and solid phase products formed by CxHy pyrolysis were characterized by GC, GC-MS, SEM and TPO-IR respectively. The results demonstrate that the molecular structure of CxHy has a great influence on pyrolysis and coking behavior. For all alkanes, CH4, C2H4, C3H6 and C4H8 are the most abundant in gaseous products, and their total content exceeds 70 %. For cycloalkanes, monocyclic cyclohexane pyrolysis tends to produce C2H4, C4H8 and 1,3-C4H6, while bicyclic decahydronaphthalene pyrolysis tends to produce CH4, C2H4 and C3H6. For aromatics, CH4 and C2H4 are the main products in the pyrolysis gas phase of benzene, toluene and ethylbenzene. Interestingly, in the liquid phase of the pyrolysis of O-containing CxHy (ethanol, acetone and tetrahydrofuran), most of the products are oxygenated compounds and no aromatics. SEM and TPO-IR revealed that at least three carbon species were formed by cracking of CxHy molecules with different structures, including amorphous, filamentous and granular carbon. However, due to the great and complex influence of CxHy molecular structure on the micro morphology of carbon deposition, it is difficult to classify all carbon species at present, which needs further experiments and researches.