Phosphate-passivated mordenite for tandem-catalytic conversion ofsyngas to ethanol or acetic acid

Selective and stable production of C₂ oxygenates from syngas is enabled by a phosphate-passivated mordenite catalyst used in tandem with a commercial Cu/ZnO/AlMgO_x catalyst. Unmodified mordenite used in this arrangement is accompanied by substantial hydrocarbon formation and carbon deposition. Therefore, phosphate groups are used to remove or significantly reduce Brønsted acidity in mordenite by capping aluminum sites. Such groups are stable to calcination and catalyst regeneration. Trimethylphosphite is used as a phosphate precursor because it is able to enter the 12 membered-ring pores of mordenite where hydrocarbon formation occurs, but not enter the 8 membered-ring side-pockets, where methanol carbonylation occurs selectively. The catalyst was characterized using X-ray fluorescence, X-ray diffraction, and thermal gravimetric analysis. Optionally, a third bed of Cu/ZnO/AlMgO_x catalyst is able to hydrodeoxygenate acetic acid to ethanol. The C₂ oxygenate selectivity is over 96% and among the best reported in a single reactor with a syngas feed.