Selectivity of the Lindlar catalyst in alkyne semi-hydrogenation: a direct liquid-phase adsorption study

Abstract

We study the alkyne semi-hydrogenation selectivity over Pd and Lindlar catalyst with liquid-phase adsorption. The results indicate that there are strongly-adsorbing alkyne and alkene sites; alkenes react non-selectively over the...

Homogeneous catalyst modifier for alkyne semi-hydrogenation: systematic screening in an automated flow reactor and computational study on mechanisms

“…Table 2 lists the adsorption energy of the modifiers calculated in this study and that of MBE reported in the previous study. 8 The adsorption energy of MBE is reported to be similar to MBY on Pd(110) and Pd(210) indicating that adsorption of MBE is equally likely over these surfaces opening the possibility for MBE adsorption and subsequent reactions. Note that the adsorption structure of MBE (adsorbed via H atom, OH group, or CH 3 group) little changed the adsorption energy.…”

“…Oligomerization is a major side-reaction in the case reaction with neat alkyne 17 or reaction in gas-phase 23 but negligible with isopropanol solvent. 8 We have previously developed flow reactor systems equipped with in-line GC 24 and HPLC 29 that take aliquots from the reactor outlet and directly inject them into the chromatography columns (note that in a strict classification, 30 they are called at-line analysis). Such technic minimizes human operation and enables automated feedback to the design of experiment algorithms.…”

“…Therefore, it is worthwhile to examine the mechanism of the catalyst modification to reduce the scope of experimental work. Previous studies focusing on Lindlar catalyst 8,23 with quinoline proposed models to explain selectivity improvement. They feature the adsorption of quinoline on the catalyst surface to block undesired reactions.…”

“…Few examples on this topic involve a density functional theory (DFT) study on the role of quinoline to the acetylene semi-hydrogenation on the Lindlar catalyst 23 and our direct liquid-phase adsorption study featuring selective sites and unselective sites of Pd catalyst. 8 The former study revealed that quinoline isolates the adsorbed reactants to prevent oligomerization. The latter study proposed the model of two different types of active sites of selective sites and unselective sites.…”

Hybrid Pd-Nanoparticles within Polymeric Network in Selective Hydrogenation of Alkynols: Influence of Support Porosity

“…At present, palladium-catalyzed reactions can be considered as the most abundant in fine chemistry, which makes palladium catalysts extremely important [1][2][3][4][5][6][7]. Recently, there has been increased interest in environmentally benign Pd-catalyzed processes that are also economically viable.…”