Reaction Kinetic Model of Naphtha–Methanol Catalytic Conversion for Light Olefins over HZSM‑5 Based on Structure-Oriented Lumping

To achieve the efficient conversion of naphtha to light olefins at low energy consumption, the naphtha–methanol coupling conversion catalyzed by HZSM-5 was studied at temperatures of 550–700 °C and weight hourly space velocity (WHSV) of 4.6–11.6 h^–1. In comparison to the individual naphtha catalytic cracking system, an improved total conversion was achieved from 80.8 to 88.7 wt % with the increase of the light olefin yield from 39.3 to 50.5 wt % in the naphtha–methanol combined system at the WHSV of 4.6 h^–1 and 650 °C. The kinetic model of naphtha–methanol coupling conversion was constructed using the structure-oriented lumping (SOL) method, which made up for the deficiencies of traditional lumped models in the study of transformation routes at the molecular level. A total of 41 kinds of molecules were chosen to depict the feedstock, and 64 reaction rules were formulated to establish reaction networks in this model. The proposed SOL kinetic model illustrated that the maximum propylene yield is 28.5 wt % at 650 °C and WHSV of 4.0 h^–1, and the maximum ethylene yield is 35.2 wt % at 700 °C and WHSV of 4.0 h^–1. The model can predict the product distribution of the naphtha–methanol coupling reaction over HZSM-5 investigated in the fixed-bed reactor reasonably well, with a deviation of less than 1.0%.