ABSTRACT
The primary production pathway of β-unsaturated alcohols is through the sequential processes of hydroformylation followed by selective carbonyl reduction, yielding in excess of 5 million tons globally of aldehydes and aldehyde-derived chemicals (2). With this quantity of production, it is important to examine the hydrogenation/isomerization properties of this class of compounds as possible synthetic routes to other high commodity chemicals. For 3-buten-2-ol and 1,4-pentadien-3-ol in particular, a review of the literature reveals no prior studies of hydrogenation/isomerization on Pd-black, either for conventional or ultrasound-assisted heterogeneous catalysis approaches. This lack of research effort examining the effect of ultrasound on competing reaction processes serves as motivation for our investigation here. Ultrasound as a synthetic tool is well-known (3-6), thus our work here is an extension of prior investigations. Experimental Section The reagents selected as model β-unsaturated alcohol compounds for hydrogenation were 3-buten-2-ol and 1,4-pentadien-3-ol (Aldrich, 97% and 99% purity, respectively). Palladium-black catalyst was used (Alfa Aesar, 99.9% purity metals basis). The specific surface area of the catalyst was determined using the nitrogen adsorption BET and O2-H2 titration method. The effect of sonication was to increase specific surface area from 7.3 to 7.6 m2/g (BET) and 12.2 to 16.7 m2/g (titration). Deionized water (18 MΩ-cm) was used as the solvent. Hydrogenations were performed with hydrogen gas (A&L specialty gas, 99.99% purity) at a pressure of 6.8 atm (100 psia). All components used in the reaction apparatus are commercially available. The apparatus consisted of a Branson Ultrasonics model 450 Sonifier II unit (20 kHz, up to 400W deliverable) with a probe extending into a jacketed reaction cell (Branson model 101-021-006) (3). The cell was connected to a NesLab RTE-140 bath circulation unit to allow isothermal heterogeneous catalysis at 298±2 K. Analysis of samples collected during an experiment were performed on a Hewlett-Packard GC/MS (5890 GC and 5972 MS) with injections done by an Hewlett-Packard GC/SFC automated injector. Authentic standards were employed in the calibration of mass area counts.
