Kinetic Parameters for the Selective Hydrogenation of Acetylene on GaPd₂ and GaPd

Abstract

Intermetallic GaPd is a highly selective and stable catalyst for the semi-hydrogenation of acetylene. Knowledge of the underlying reaction kinetics is essential to gain a deeper understanding of the selective hydrogenation on this catalytic material. To date, there has been no experimental kinetic data published for this reaction on a well-defined intermetallic catalyst possessing isolated active sites. Kinetic measurements are performed at 140-200 °C, revealing an apparent activation energy of 29(2) kJ mol . GaPd is shown to be the first binary catalyst material, which shows a positive reaction order (0.89) with respect to acetylene at 200 °C. The influences on the extent of acetylene conversion, specific activity and selectivity to ethylene, ethane, and higher hydrocarbons are determined by a 2 factorial experiment following a design of experiments approach. Temperature and pressure have the strongest impact on these values. The results allow optimal operation for achieving high ethylene yields. A comparison of the reaction kinetics on GaPd with experimental results obtained for GaPd reveals different orders of reaction of H and C H on the two compounds.

Revealing Electronic Influences in the Semihydrogenation of Acetylene

“…14,18 Among these, GaPd 2 shows the best catalytic properties, which is also displayed in its kinetic parameters. 19,20 Electronic influences in catalysis have been studied numerous times on elements or substitutional alloys. By using different elements in their elemental form, the smallest possible electronic change is by one electron per atom, i.e., rather coarse.…”

“…Due to the need of high product volume, the ideal catalyst for this process has to be very active and at the same time possess an excellent selectivity . The latter is beneficially influenced by isolated active sites, which are offered by well-ordered, largely covalently bound intermetallic compounds like Ga 7 Pd 3 , GaPd, and GaPd 2 . , Among these, GaPd 2 shows the best catalytic properties, which is also displayed in its kinetic parameters. , …”

Acetylene in Organic Synthesis: Recent Progress and New Uses

“…Strong adhesion of MgGaAl-LDH to Al 2 O 3 is a consequence of direct growth of the catalyst on the spherical Al 2 O 3 . Pure Pd/Ga alloys (GaPd 2 and GaPd) are also moderately active, but there was no rate limitation of acetylene concentration and occupation on the catalyst surface [ 270 ]. Inkjet printing allows to obtain Pd/Ga catalysts with thin, uniform and homogeneous wall coatings over the entire channel surface [ 271 ].…”

Supported Ni–Au Colloid Precursors for Active, Selective, and Stable Alkyne Partial Hydrogenation Catalysts

“…In addition, Ni is a particularly active oligomerization catalyst and generates oligomeric side products (“green oil”) that deactivate the catalyst. − Various groups improved alkene selectivity using low Pd loading or Pd single sites. , Pd is also incorporated into PdM bimetallic catalysts to control catalyst selectivity and improve stability. Recent studies using PdZn alloys showed weaker alkene binding contributed to improved selectivity. , Both alkene selectivity and catalyst stability were further improved by preparing highly dilute Pd sites in Ga, Cu, − Au, − and Ag. , Of these, PdAg/Al 2 O 3 is widely used for industrial partial alkyne hydrogenation. , …”

“…16,17 Both alkene selectivity and catalyst stability were further improved by preparing highly dilute Pd sites in Ga, 18 Cu, 19−24 Au, 25−32 Ag. 3,33 Of these, PdAg/Al 2 O 3 is widely used for industrial partial alkyne hydrogenation. 10,34 The rising cost of Pd has led to a renewed search for less expensive alkyne hydrogenation catalysts.…”