Ultrasound‐ and Microwave‐Assisted Preparation of Lead‐Free Palladium Catalysts: Effects on the Kinetics of Diphenylacetylene Semi‐Hydrogenation

Abstract

The effect of environmentally benign enabling technologies such as ultrasound and microwaves on the preparation of the lead‐free Pd catalyst has been studied. A one‐pot method of the catalyst preparation using ultrasound‐assisted dispersion of palladium acetate in the presence of the surfactant/capping agent and boehmite support produced the catalyst containing Pd nanoparticles and reduced the number of pores larger than 4 nm in the boehmite support. This catalyst demonstrated higher activity and selectivity. The comparison of kinetic parameters for diphenylacetylene hydrogenation showed that the catalyst obtained by using the one‐pot method was seven times as active as a commercial Lindlar catalyst and selectivity towards Z‐stilbene was high. Our work also illustrated that highly selective Pd/boehmite catalysts can be prepared through ultrasound‐assisted dispersion and microwave‐assisted reduction in water under hydrogen pressure without any surfactant.

Scale up study of capillary microreactors in solvent-free semihydrogenation of 2‐methyl‐3‐butyn‐2‐ol

“…This result is in line with the data reported for Pd and Pd-Bi catalysts [55,56,58]. The KMBE/KMBY and KMBA/KMBY ratios are below 0.1.…”

“…The conditions were selected to ensure that the conversion of MBY was below 80 %, which allowed for determination of apparent reaction rates directly from MBY conversion as the reaction rate follows a pseudo-zero order kinetics [55,56]. The alkene selectivity above 97.5 % was observed for all the reactors studied except for the r1.6-1.8 reactor.…”

“…% Pd/ZnO catalyst in the batch reactor are shown in Figure 9. The concentration profiles were modelled using the Langmuir-Hinshelwood kinetics with competitive adsorption of organic species and dissociated hydrogen on the catalyst surface with the rate equation 3-5 [55,56].…”

Ultrasonically improved semi-hydrogenation of alkynes to (Z-)alkenes over novel lead-free Pd/Boehmite catalysts

“…These catalysts (Pd loading 0.78-0.88 wt%) were screened using DPA hydrogenation (Scheme 1) at RT and AHP in the stirring system. The catalysts textural properties and performance in DPA hydrogenation were reported in our previous study [44].…”

“…The Pd US-MW /Boehmite catalyst was prepared using US-assisted dispersion and the MW-assisted reduction of Pd(OAc) 2 in water at 1 MPa H 2 . The details of catalyst preparation methods and characterization are described elsewhere [44]. Alkynes (Alfa Aesar, 98%) were hydrogenated over the prepared Pd-catalysts at room temperature (RT, 25 ± 1°C) and under atmospheric hydrogen pressure (AHP, H 2 balloon).…”