On the kinetics of methanol dehydration to dimethyl ether on Zr-loaded P-containing mesoporous activated carbon catalyst

Abstract

Selective methanol dehydration to DME has been investigated using activated carbon-based catalysts. An activated carbon was prepared by chemical activation of olive stones, a residue of the agri-food industry, with phosphoric acid followed by Zr loading (5% (w/w)). The activation process produced a considerable amount of chemically stable surface phosphorus complexes. The addition of Zr resulted in the formation of zirconium phosphate surface species, as revealed by XPS. TPD and catalytic reaction results determined that the presence of zirconium phosphate species bonded to the carbon surface were responsible for the high steady-state methanol conversion and DME selectivity achieved by this biomass-derived catalyst. A kinetic study for the selective methanol dehydration to DME was carried out on the Zr-loaded P-containing activated carbon catalyst and the corresponding kinetic and thermodynamic parameters were obtained. The reaction seems to proceed through a modified Langmuir-Hinshelwood mechanism (LH2), in which two methanol molecules are subsequently adsorbed on one active site. The competitive adsorption of water on the active sites was also addressed in the proposed mechanism. The activation energy for the DME production was calculated and a value of 70 kJ mol−1 was obtained.