Abstract

In Part I of this series, it was seen that the favorable thermodynamic and kinetic coupling in the LPDMEtm process--of methanol dehydration reaction (very rapid and at/near thermodynamic equilibrium) with the methanol synthesis reaction (slower kinetics and highly thermodynamic) --leads the beneficial “chemical synergy”. This synergy helps to overcome the limitation on thermodynamic equilibrium conversion and increases the per-pass syngas conversion and reactor productivity. This increase in the per-pass syngas conversion can be as high as 50-100% and depends primarily on the feed H2: CO ratio.

In this part II of Series, we briefly discern the intrinsic kinetics of the LPMeOHtm and LPDMEtm systems, and also shed light of the catalyst deactivation phenomena in these processes. Among the many reports on intrinsic kinetics of the one-step LPMeOHtm and LPDMEtm processes, two illustrative kinetic studies, from the groups of University of Akron and Air Products and Chemicals, Inc. are highlighted and discussed further. These are mainly based on the independent, component kinetic models of methanol synthesis (Vanden Bussche and Froment) and methanol dehydration (Bercic & Levec). From an overarching analysis of the deactivation of supported copper catalysts for methanol synthesis and other reactions (methanol decomposition and methanol steam reforming), we propose that thermal sintering, i.e., increase in Cu particle site and loss of metal surface area, is the only cause of catalyst deactivation in methanol synthesis reactions over Cu/ZnO/Al2O3 industrial-type methanol catalysts. In closing, we outline the reactor design/scale-up and plant operational experience of the 3 commercial technologies, as currently practiced by JFE holdings, BP-AMOCO, and Halder-Topsoe.

Keywords: Natural gas; Steam reforming; Coal; Syngas; Methanol; DME; Bi-functional catalysts; Cu/ZnO/Al2O3; γ-Al2O3; Slurry reactors; Bubble column reactors; Chemical synergy; Methyl equivalent productivity (MEP); Intrinsic kinetics; Phase equilibrium; Chemical reaction equilibrium; Catalyst deactivation