Effect of propylene in feedstock on the coking behavior of PtSnK/Al₂O₃ catalyst of propane dehydrogenation

The dehydrogenation of propane was carried out with propane containing different proportions of propylene, and the carbon deposition behavior of Pt-based catalyst under propene-rich condition was investigated. The results show that the presence of propylene in the raw material accelerates the rate of carbon deposition, shortening the time of dynamic equilibrium of carbon deposition on the support, and promoting the formation of carbon on the surface area of the active phase and the graphitization of carbon deposition. At the same time, the rich propylene in the raw material increases the amount of unsaturated aliphatic compounds, thus promoting the generation of aromatic carbon and graphitized carbon, but the catalyst structure is not destroyed. In the process of propane dehydrogenation, when the propylene content increases to 1.5%, the carbon “peak I” appears on the surface of the active phase, and the "peak II" moves to the high temperature region. When the alkene content increases by 3.0%, peak I and peak II merge together, and the area of the entire peak increases significantly. When the carbon deposition exceeds 10.26%, the degree of carbon deposition and graphitization of the catalyst becomes higher and higher. The increase of the propylene content accelerates the saturation process of the carbon holding capacity of the carrier. Under the same reaction time, the amount of carbon deposit increases.