Ultrasound-assisted hydrogenation of cinnamaldehyde

Abstract

The hydrogenation, employing hydrogen gas, of cinnamaldehyde was performed using Pd-black and Raney Ni catalysts at 298+/-3 K in a water-cooled (jacketed) reaction vessel. Sampling at pre-determined time intervals and GC/MS analysis yielded time-dependent product state distribution information. A kinetic modeling of the data revealed that cinnamaldehyde was both hydrogenated directly to the final product benzenepropanol, as well as a fraction being converted to the intermediate benzenepropanal, where the latter was subsequently hydrogenated to benzenepropanol. Comparing the ultrasound-assisted and blank (stirred) experiments revealed that a higher maximum relative concentration of the intermediate benzenepropanal was formed in the ultrasound experiments compared to the stirred experiment. The activity of the ultrasound experiments compared to blank were 9-fold and 20-fold greater for the Pd-black and Raney Ni catalysts, respectively. Finally, an application of the Bell-Evans-Polanyi principle to yield an estimate of the ratio of rate coefficients for benzenepropanal and benzenepropanol formation was performed by considering chemical group energy differences and surface adsorption energy differences in the first mechanistic step of hydrogenation.

The effect of cavitating ultrasound on the aqueous phase hydrogenation of cis-2-buten-1-ol and cis-2-penten-1-ol on Pd-black

“…Conversely, without the dopant no cavitation occurred even when employing full sonifier power (100% amplitude and $400 W in 50 mL solution volume). This www.elsevier.com/locate/apcata Applied Catalysis A: General 288 (2005) 62-66 study can be compared to other work, where substantially smaller changes in selectivity (<50%) are observed when high power non-cavitating ultrasound is employed as the processing method compared to a silent control experiment [2][3][4][5]. As an extension of this work and to attempt to find an application of this ultrasound processing methodology, we study here the hydrogenation of simple model cis-olefins and characterize their conversion to the trans form versus the saturated alcohol species.…”

“…Hydrogenations were performed with hydrogen gas (A&L specialty gas, 99.99% purity) at a pressure of 6.5 atm (80 psig). All components used for the reaction apparatus are commercially available and have been described in detail previously [1,2]. Samples collected during an experiment were analyzed on a Hewlett-Packard GC/MS (5890 GC and 5972 MSD).…”

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

“…US has been used to overcome this problem and is usually reported to greatly accelerate the catalytic hydrogenation of olefins [29,54], cinnamaldehyde [55,56], 3-buten-2-ol [57,58], while selectivity to target products is either unchanged or increased under mild RT and AHP conditions. This effect has been attributed to sonication's dispersion effect on the catalyst and the effect of cavitation on the hydrogenation process.…”

Synthesis and Biological Evaluation of New Substituted Hantzsch Thiazole Derivatives from Environmentally Benign One-Pot Synthesis Using Silica Supported Tungstosilisic Acid as Reusable Catalyst

“…Despite its unusual activation mode, ultrasonic irradiation ( US ) has been increasingly used in organic synthesis in the last three decades [ 40 , 41 ]. A large number of organic reactions can be carried out in higher yields, shorter reaction time and milder conditions under ultrasound irradiation [ 42 , 43 ]. In comparison to conventional methods, the US method is more convenient and easily controlled [ 44 , 45 , 46 ].…”