Catalysis of Organic..

218 Cavitating Ultrasound HydrogenationResults for this system are given in Figure 1 as the [saturated alcohol/trans]molar ratio versus extent of reaction (e.g., conversion). We have observed thatcavitating ultrasound results in a [(saturated alcohol/trans olefin) ultrasound /(saturatedalcohol/trans olefin) silent ] ratio quantity greater than 2.0 at the reaction mid-point forboth the C4 and C5 olefin systems. This indicates that ultrasound reduces transolefinproduction compared to the silent control experiment. Furthermore, there isan added 30% reduction for the C5 versus C4 olefin compounds again at reactionmid-point. We attribute differences in the ratio quantity as a moment of inertiaeffect. In principle, C5 olefins have a ~52% increase in moment of inertia aboutC2=C3 double bond relative to C4 olefins, thereby slowing isomerization. Sinceseed oils are C18 multiple cis olefins and have a moment of inertia even greater thanour C5 olefin here, our study suggests that even a greater reduction in trans-olefincontent may occur for partial hydrogenation of C18 seed oils.Saturated alcohol/Trans-olefin ratio2.01.51.00.52-butene-1-ol (Ultrasound)2-butene-1-ol (Silent)2-penten-1-ol (Ultrasound)2-penten-1-ol (Silent)0.2 0.4 0.6 0.8ξ (Extent of reaction)Figure 1. The saturated alcohol/trans-olefin ratio for the 2-buten-1-ol and 2-penten-1-ol systems are shown versus extent of reaction (ξ).The following question can be asked in light of our study here: Can partialhydrogenation of edible seed oils as an industrial process ever be viable usingcavitating ultrasound processing? Despite this study that suggests that cavitatingultrasound hydrogenation may have advantages over traditional processing methods,we can only make broad predictions extrapolating this work to the partialhydrogenation of actual C18 seed oils. For example, based on the cavitatingultrasound C5-olefin result here that ~50% hydrogenation occurred at ~80 seconds, itcan be computed that it cost ~$0.35USD/lb for 50% hydrogenation (assumingelectricity cost is $0.05USD/ kW-h and power usage was 280 W during treatment).Therefore, assuming similar costs for C18 seed oils, from an economic perspectivethe cost is likely not prohibitive. A second issue is the catalytic selectivity towardshydrogenation relative to isomerization (to the trans-olefin). Here, as an example, ifwe consider isomerization about the C9 position in linoleic acid there would be aroughly ~6.1-fold increase in moment of inertia for this particular double bondversus our C5-olefin [6-8], which from our result comparing our C4 and C5 olefinshere suggests there would be an approximate 3.5-fold decrease in trans-olefinproduction in linoleic acid using cavitating ultrasound. For comparable amounts of