Selective hydrogenation of ethyl phenylacetate to 2-phenylethanol over Zr-modified Cu/ZnO/Al2O3 catalysts

Zr-modified Cu/ZnO/Al 2 O 3 catalysts were prepared by coprecipitation and evaluated for the selective hydrogenation of ethyl phenylacetate to 2-phenylethanol. The effects of the nominal Al/Zr molar ratio, calcination temperature, and zirconium precursor were investigated to establish relationships between catalyst preparation, structure, and hydrogenation performance. Increasing the nominal Zr/(Al + Zr) molar ratio within the investigated composition range was accompanied by a decrease in CuO crystallite size from 26.4 to 17.2 nm and an increase in BET surface area from 53.93 to 68.06 m 2 ·g −1 . The catalyst with a nominal Cu 2+ :Zn 2+ :Al 3+ :Zr 4+ molar ratio of 2:1:0.1:0.9, calcined at 450 °C and prepared from Zr(NO 3 ) 4 ·5H 2 O, exhibited the highest activity and selectivity. Following Box–Behnken response-surface optimization, an ethyl phenylacetate conversion of 91.7% and a 2-phenylethanol selectivity of 90.1% were obtained at 185 °C, 11 MPa H 2 , and 10 h. Structural and surface analyses indicated that tuning the Al/Zr composition in the Zr-modified catalyst was associated with smaller CuO crystallites, improved Cu dispersion, modified reduction behavior of Cu species, and a surface containing coexisting Cu 0 , Cu + , and residual Cu 2+ species. The coexistence of Cu 0 and Cu + species may contribute to H 2 activation and ester carbonyl adsorption and polarization, respectively. The catalytic activity gradually decreased during five reuse cycles, which may be associated with possible Cu crystallite growth or aggregation, textural deterioration, and the accumulation of adsorbed organic species and carbon-containing residues.