Deactivation of zirconium-phosphorus carbon catalyst on the dehydration of methanol todme reaction

Abstract

Dimethylether (DME) can be used for energy purpose instead of GLP and diesel, or as a feedstock for fuel cells. Moreover, DME is a platform and is an attractive alternative as a clean propellant. At the moment, DME is produced by methanol dehydration. This methanol could be obtained from syngas produced by biomass gasification, generating a sustainable source for DME synthesis. For this reason, DME is being deeply studied as a potential renewable substitute for petroleum derivative. Lots of papers search for the best operating conditions of many catalysts for the production of DME, however, addressing how the catalyst deactivates, mainly by coke deposition, is also an issue of great interest for this process. Our work focuses on this point, given that the knowledge of deactivation details will allow us optimizing the catalyst synthesis for the best DME production process conditions. Physical (CO2 gasification) and chemical (phosphoric acid) activation of an agroindustrial waste (olive stone) have been used to prepared activated carbons that have been studied as catalyst supports for the methanol to DME reaction. These porous carbons were impregnated with zirconium to obtain the final carbon catalysts. Thus, porous carbons containing different surface catalyst phases (C, C-P, C-Zr and C-P-Zr) were prepared. The methanol to DME reaction experiments were carried out in a laboratory fixed bed reactor at a partial pressure of 0.04 atm and at several residence times (from 0.05 to 0.1 g·s/μm) and temperatures (from 300 to 600ºC). The catalytic system containing surface C-P-Zr seems to present two kinds of active sites, which are deactivated at different rates. One of them loses their activity fast (even at the lowest temperature studied), while the other one does not lose activity at the studied temperatures, starting to deactivate only at temperatures above 400ºC.