Bimetallic Pd/Sn‐based Nanoparticles and their Catalytic Properties in the Semihydrogenation of Diphenylacetylene

Abstract

Multimetallic nanoparticles often enhance the catalytic performance of their monometallic counterparts by increasing reaction rates, catalyst selectivity, and/or stability. A prerequisite for understanding structure‐ and composition‐associated properties, however, is the careful design of multimetallic nanoparticles with various structures and compositions. Here, bimetallic Pd/Sn‐based nanoparticles are prepared with a tunable composition and structure exploiting ionic liquids (ILs) as reaction medium (i. e., methyltrioctylammonium bis(trifluoromethylsulfonyl)imide). The nanoparticles are obtained in a one‐pot synthetic procedure by reducing the metal salt precursors with triethylborohydride in the IL. The results show that the reaction parameters, in particular the nature and ratio of the Pd 2+ /Sn 2+ precursors as well as the reaction temperature, influence NP formation and composition. X‐ray diffraction with Rietveld analysis and transmission electron microscopy are employed to determine NP size and phase composition. Under optimized reaction conditions Pd 2 Sn or PdSn nanocrystals are formed as single‐phase products after introducing an additional annealing step at 200 °C. Nanocrystals with intermetallic composition reveal enhanced catalytic properties in the semihydrogenation of diphenylacetylene which was used as a model reaction.

Pd/Ag Nanoparticles Prepared in Ionic Liquids as Model Catalysts for the Hydrogenation of Diphenylacetylene

“…Intermetallic Pd 2 Sn and PdSn NP catalysts prepared by us using a similar approach in ILs were less active than the bimetallic Pd/Ag NP‐derived catalyst but showed comparable CST selectivities in DPA semi‐hydrogenation. However, CST was not over‐hydrogenated to DPE and CST selectivity did not decrease with reaction time 30. Both the Sn content and the intermetallic phase seemed to be important in this case.…”

“…Due to their unique, tailor-made properties (e.g., low vapor pressure, high polarity, and wide electrochemical stability window), room-temperature ILs represent interesting reaction media for NP synthesis [53,54]. In ILs, NP nucleation and growth processes may be controlled by weakly coordinating anions and cations, which also act as (electro)steric stabilizers against NP agglomeration [30,[55][56][57][58].…”

“…Economic aspects associated with the high Pd loading and the toxicity of lead together with stricter environmental regulations have driven the search for new alternatives [15,19]. The selectivity to alkenes is also significantly improved for binary bimetallic Pd-M particles (e.g., with M = Cu [20], Ag [21][22][23], Au [24], Zn [6], Ga [25,26], In [27][28][29], Sn [30], or Bi [31]) or even ternary Pd-based phases (such as Pd-Bi-Se [32] or Pd-Ga-Sn [33,34]). In addition, non-precious, binary alloys (Ni-Fe or Ni-Ga) [35,36], intermetallic compounds (Al 13 Fe 4 ) [37], transition metal-free Zintl phases (BaGa 2 ), or non-precious, ternary phases (Cu-Ni-Fe) [38] have been reported as catalysts for semi-hydrogenation of alkynes in the gas or liquid phase.…”

Pd–In intermetallic nanoparticles with high catalytic selectivity for liquid-phase semi-hydrogenation of diphenylacetylene

“…[11][12][13] Many efforts have been devoted to synthesize and optimize Pd catalysts by bimetallic Pd-M alloys (e.g. with M = Cu, 14 Ag, [15][16][17] Au, 18,19 Zn, 20 Ga, 21 In, [22][23][24] Sn, 25,26 or Bi) 27 or even ternary Pd-based phases (such as Pd-Bi-Se 28 or Pd-Ga-Sn), 29,30 improving catalytic selectivity for the selective hydrogenation of alkynes. In addition, non-precious, binary alloys (Ni/Fe), 31 intermetallic compounds (Al 13 Fe 4 ), 32 transition metal-free Zintl phases (BaGa 2 ), or non-precious, ternary phases (Cu-Ni-Fe) 33 have been reported as interesting catalytic materials for alkyne semi-hydrogenation in the gas or liquid phase.…”

“…2 Sn, PdSn, Pt 3 Sn and PtSn IMNPs in [OMA][NTf 2 ] at 200 °C 25,52. By weakly coordinating anions and cations, ILs are capable to control both particle nucleation and growth processes during NP synthesis.…”