Coke formation on the surface of α-Al2O3 in the catalytic pyrolysis of naphtha

The catalytic pyrolysis of naphtha has been carried out in a quartz reactor loaded with 5 mm alpha -Al2O3 spheres, The yields of ethylene and propylene exhibit about 10% and 5% higher values compared to the thermal pyrolysis in the absence of alpha -Al2O3 spheres at the same reaction conditions. The coke formation on alpha -Al2O3 spheres increased continuously along with the axial length of the reactor as well as with reaction time. Results suggest that the concentration of the coke precursors in the gas phase may increase along with the axial length of the reactor. Coke filled up completely the internal pore of the sphere near the exit of the reactor after reaction for 4 hr. The coke film on the external surface of the sphere grew continuously thicker. The coke formation was influenced strongly by the physical properties of the alpha -Al2O3 spheres. Coke deposition was the least on the alpha -Al2O3 sphere with the lowest surface area and pore volume among the tested alpha -Al2O3 spheres.