Kinetics of liquid-phase diphenylacetylene hydrogenation on “single-atom alloy” Pd-Ag catalyst: Experimental study and kinetic analysis

Abstract

• Pd 1 Ag 3 SAA catalyst demonstrates extremely high selectivity in diphenylethene (ca. 98 %). • Selectivity of Pd 1 Ag 3 does not depend on P(H 2 ) and DPA concentration. • Proposed kinetic model is capable to describe the experimental dependencies. Catalytic performance of Pd 1 Ag 3 /Al 2 O 3 single-atom alloy (SAA) catalyst was studied in liquid-phase hydrogenation of diphenylacetylene (DPA) and compared with the performance of the reference monometallic Pd/Al 2 O 3 . Formation of SAA structure in Pd 1 Ag 3 /Al 2 O 3 was confirmed by FTIR CO technique. It was found that Pd 1 Ag 3 /Al 2 O 3 single-atom alloy catalyst exhibits excellent selectivity in diphenylethene (stilbene) (ca. 98 %), which remains constant over a wide range of DPA conversions (0–95%), while over Pd/Al 2 O 3 selectivity decreases steadily with the increase in DPA conversion. It is remarkable that the selectivity of Pd 1 Ag 3 /Al 2 O 3 depends neither on hydrogen pressure (5–15 bar), nor on DPA concentration (0.0262 – 0.159 mol/l). In contrast, over the reference Pd/Al 2 O 3 selectivity tends to decrease with increasing P(H 2 ) and decreasing DPA concentration. The proposed reaction network comprises hydrogenation of DPA in a parallel formation of cis and trans -stilbene with following hydrogenation to bibenzyl and direct formation of the latter from the initial DPA. The calculations clearly shows the capability of the kinetic model to describe the experimental dependencies for Pd 1 Ag 3 single-atom catalyst in an excellent way with the degree of explanation equal to ca. 99 %.