Pyrolysis gasoline hydrogenation in the second-stage reactor: Reaction kinetics and reactor simulation

The second-stage rector is the last unit in the purification of pyrolysis gasoline for production of aromatics. The feedstock contains a small amount of olefin and organic sulfur but a large amount of benzene as high as 51 wt %. It is therefore a difficulty to remove sulfur and olefin thoroughly while keeping the aromatics unconverted, since the reaction is normally conducted at 280-330 degrees C and 2.5-3.0 MPa in the presence of excessive hydrogen. To evaluate the property of a commercial catalyst LY-9802 with Co-Mo-Ni supported over gamma-Al2O3, hydrogenation kinetics of thiophene, olefin, and benzene were measured, and the results show the catalyst is very active for the hydrogenation of thiophene and olefin but is inactive for the saturation of benzene. To simulate the operating behavior of the reactor, one-dimensional heterogeneous model was applied, and it was found that the gas-solid interfacial difference in temperature and concentration is negligible. From the variation of the operating variables, such as the inlet temperature, operation pressure, hydrogen flow rate, and feedstock flow rate. It shows the reactor is operated in a safe and reliable region and could be optimized with some of these variables.