Sitosterol hydrogenation

Palladium is known to be a metal that works catalytically in the system. Various supports can be used for Pd, such as active carbon, mesoporous materials, and polymers. All of them deactivate in the sitosterol hydrogenation, most probably because of sulfur and phosphorus impurities present in the raw material, which originates from the tall oil production, a side process of chemical pulping. 

The sitosterol hydrogenation and deactivation kinetics was determined in a shaking constant-pressure batch reactor by using the new type of synthetic support material (mesoporous carbon Sibunit) for palladium (4wt% Pd) [55]. 

Warna, J., Flores Geant, M., Salmi, T., Hamunen, A., Orte, J., Hartonen, R., and Murzin, D. (2006) Modelling and scale-up of sitosterol hydrogenation process from laboratory slurry reactor to plant scale. Ind. Eng. Chem. Res., 45, 7067-7076. 

Efficient analysis plays a cracial role in chemical process industry. It should provide timely, precise and accurate measurements of the process parameters. For fine chemicals synthesis it usually means that extent of reaction in a batch reactor should be effectively determined. Although gas chromatography is a very reliable tool for accurate determination in sitosterol hydrogenation, rather cumbersome analytical procedure calls for another more fast way to monitor progress of the reaction. 

It follows from Fig. 5, that UV spectroscopy proved to be an efficient analytical tool in P-sitosterol hydrogenation. 

The sitosterol-sitostanol mixture is cleaned via adsorption on active carbon before entering the hydrogenation reactor. 

Figure 8.10 Reaction scheme in the hydrogenation of sitosterol to sitostanol.

It should be emphasized that the approach proposed is by no means limited to the actual case, hydrogenation of sitosterol, but is a general one for the reaction scheme, which is very common in catalyst poisoning. The methodology with semianalytical solutions of the surface species turned out to be very robust in the... 

Figure 8.11 Example of data fitting results - concentrations of sitosterol, campesterol, and the products in the hydrogenation of sitosterol to sitostanol (increasing curve) on Pd/Sibunit. The lower curves represent campesterol and campestanol.

Martin Curvelo, G. (2008) Hydrogenation of sitosterol to sitostanol on Pd catalysts. M.Sc. Thesis, Abo Akademi, Turku/Abo Finland. 

Microwave-assisted catalytic hydrogenation of steroid compounds, e. g. cholesterol, campesterol, sitosterol, etc., in the presence of Pd/C catalyst and ammonium formate in glycol solvent was fast and afforded the corresponding products in high yield (80-95%) and purity [42]. 

Plant sterols such as sitosterol and camposterol, as by-products from vegetable oils at prices of about 15 kg-1, are also important starting materials for the production of steroid hormones. A new application is the cholesterol lowering property of these sterols esterified with fatty acids (with a production of about 10000 t a 1). They can be found in the margarine Becel pro-active of Unilever. A Finnish equivalent is Benecol, which contains stands such as sitostanol and campostanol, sterols having the 5,6-double bound hydrogenated, also esterified with fatty adds [33]. 

Ophiorrhiza japonica Blume 0. mungos L. Japan She Gen Cao She Gen Cao (whole plant) Resin, alkaloid, beta-sitosterol, 5 alpha-ergost-en-3 beta-ol, 5 alpha-ergost-8(-14)-en-3B-ol, tannates, hydrogen cyanide.50 For circulatory and pulmonary ailments. 

Unsaturated sterols such as cholesterol, campesterol, sitosterol and bile alcohols with unsaturated side chains can be transfer hydrogenated efficiently and with high yields under microwave irradiation, using ammonium formate and a Pd/C catalyst in methylene chloride/propylene glycol solvents (Scheme 4.3)17. 

Fig. 63. Dependences of the hydrogen peroxide oxidation current of a cholesterol oxidase sensor on the concentration of cholesterol and sitosterol.

Subsequently data from other insects support the biogenetic pathway show in Fig. 17. Goodwin s group found that the dealkylation of the synthetic [25- H, 26- C]clionasterol (C-24 epimer of sitosterol) to desmosterol by the insect, Tenebrio molitor, also involves migration of the C-25 hydrogen to the C-24 position [150-152]. The same mechanism was also proposed for the dealkylation of sitosterol in the locust Locusta migratoria L. [153]. 

Catalyst Deactivation in Selective Hydrogenation of P-Sitosterol to P-Sitostanol over Palladium... 

Sitostanol can be obtained by hydrogenation of the double bond in sitosterol over Pd catalysts [3,4] according to the following scheme ... 

The aim of this work was to investigate catalyst deactivation in selective hydrogenation of (J-sitosterol to (3-sitostanol over a Pd supported catalyst, as well as to find ways to regenerate the deactivated catalyst. 

Hydrogenation reactions of (3-sitosterol were performed in a 300 ml autoclave (Parr) using 1-propanol as a solvent. The stirring rate was 1000 rpm The hydrogen (AGA, 99.999% and AGA, 99.99%) pressure was 4 bar and temperature was 80°C. The fresh, deactivated and regenerated catalysts were characterized by BET and XPS techniques. 

Some of the experimental results are presented in Fig. 2. The catalysts used in the hydrogenation reaction were from the same batch and the raw material (sitosterol) used was also the same. The main product was sitostanol, while sitostanone (2 in Fig. 1) was obtained in inferior quantities (below 1%). 

Figure 8.39. Hydrogenation of sitosterol in a batch mode with different catalyst amounts. Comparison between experimental and calculated (eq. 8.186) data.

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