The nature of modifying effect of gallium on Pd-Ga/Al2O3 catalyst for liquid-phase selective acetylene hydrogenation

• Pd-Ga/Al 2 O 3 catalysts are promising in liquid-phase acetylene hydrogenation process. • Co-deposition of Pd(NO 3 ) 2 and Ga(NO 3 ) 3 prevents the γ-Ga 2 O 3 -Al 2 O 3 phase formation. • Ga changes the electronic state of Pd at Pd:Ga = 1:0.5 and C 2 H 4 selectivity is 66%. • Selectivity of C 2 H 4 increases to 70% at Pd:Ga = 1:2 due to the Pd 2 Ga phase formation. • The catalyst treated in H 2 at 500 °C has the highest ethylene selectivity of 75%. The structural properties of Pd-Ga/γ-Al 2 O 3 samples prepared from joint Pd(NO 3 ) 2 and Ga(NO 3 ) 3 solution and their catalytic properties in liquid-phase acetylene hydrogenation have been studied. Using temperature programmed reduction (TPR-H 2 ), transmission electron microscopy (TEM), diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (CO-DRIFTS) and X-ray photoelectron spectroscopy (XPS) it was found that an increase in the ethylene selectivity to ∼ 66–70% is explained by the modification of the electronic properties of palladium by gallium at a Ga:Pd molar ratio of 0.5 and by the formation of bimetallic Pd 2 Ga particles in the case of Ga:Pd = 2.