Deactivation of Cu-Mg-Al mixed oxide catalysts for liquid transportation fuel synthesis from biomass-derived resources

P.J. LUGGREN; J.I. DI COSIMO

Molecular Catalysis

Elsevier B.V.

Lugar: Ámsterdam; Año: 2020 vol. 481 p. 1 - 11

2468-8231

A "platform molecule" (2-hexanol) obtained from the primary conversion of sugars was upgraded to liquid transportation fuel precursors under gas phase conditions at 573K and 101.3 kPa. Reaction was promoted by Cu-Mg-Al mixed oxides with different copper loading (0.3-61.2%) and a Mg/Al=1.5 (molar ratio). Products were mainly low oxygen content C9-C24 oxygenates and hydrocarbons. The product pool average molecular weight and the oxygenates/hydrocarbons ratio increase with the catalyst copper loading, but the latter might be diminished by augmenting the contact time. A slow catalyst deactivation process occurs in the first 2h of reaction. Temperature-programmed oxidation, BET surface are measurements and X-ray photoelectron and Auger electron spectroscopies of the spent catalysts indicated that the main reasons for the activity decay during reaction are carbon deposition on the active sites and, to a lesser degree, partial oxidation of the surface copper particles. Oxygenates (reactant or products) are the chemical species responsible for deactivation. The initial deactivation rate (r_d0) depends on the copper content and contact time. On catalysts with low Cu content, r_d0 is higher at short contact times, which is consistent with coke formed directly from the reactant. Contrarily, at high Cu loadings r_d0 increases with contact time and parallels formation of heavy unsaturated oxygenates. Oxidation/reduction/catalytic test cycles of spent Cu-Mg-Al mixed oxides were implemented to explore catalyst reusability.