Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-16Results and discussionTypical kinetic curves over Pd/C (Aldrich) at 80°C and 4 bar are displayed in Fig. 2.0.10.08SitosterolSitostanolCampesterolCampestanol21,81,61,4c (mol/l)0.060.04Arbitrary units1,210,80,615 min20 min30 min40 min50 min80 min110 min0.020,40,200 20 40 60 80 100 120 140Time (min)Fig. 2. Hydrogenation of β-sitosterol over Pd/C (360mg) at 80°C and 4 bar overall pressure.0170 220 270 320 370Abs, nmFig. 3. UV-spectra of the reaction samples as afunction of time.Preliminary experiments demonstrated the crucial role of the catalyst. For instance, Fig 2shows that maximum conversion of only 80 % could be achieved with lower (360 mg)catalyst amounts. The reaction was, however, 100% selective, since neither sitostane nositostanone were found in GC-MS analysis.Due to high selectivity, a fast analytical tool, e.g. UV spectroscopy could be used tomeasure the amount of ethylenic double bonds. Fig 3 shows the UV-spectra for the reactionmixture demonstrating in a reliable way, how the concentration of β-sitosterol is decreasingwith time. The catalyst screening with the following Pd supported catalysts, Pd-SBA-15, Pd-MCM-41, Pd-CNF, Pd-C (Sibunit) as well as the kinetic experiments and the catalyst reusewith the most promising catalyst were performed and the results will be discussed in the finalpresentation.ConclusionsSeveral supported palladium catalysts were screened in β-sitosterol hydrogenation.Catalyst deactivation was found to be crucial using lower amounts of Pd/C. Very highselectivity towards the desired product, β-sitostanol was achieved. A fast analytical tool, i.e.UV-spectroscopy was applied to monitor the reaction products.References1. Miettinen, T., Puksa, P., Gylling, H., Vanhanen, H., Vartiainen, E., The New England Journal of Medicine,333 (1995) 1308.2. Lindroos, M., Mäki-Arvela, P., Kumar, N., Salmi, T., Murzin, D. Yu., Catalysis of Organic Reactions,Marcel Dekker Inc., New York, 2002, 587.57