| 2. |
- Van den Hark,, et al.
(författare)
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Hydrogenation of fatty acid methyl esters to fatty alcohols at supercritical conditions
- 1999
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 76:11, s. 1363-1370
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Tidskriftsartikel (refereegranskat)abstract
- Extremely rapid hydrogenation of fatty acid methyl esters (FAME) to fatty alcohols (FOH) occurs when the reaction is conducted in a substantially homogeneous supercritical phase, using propane as a solvent, over a solid catalyst. At these conditions, the limitations of hydrogen transport are eliminated. At temperatures above 240 °C, complete conversion of the starting material was reached at residence times of 2 to 3 s, which is several orders of magnitude shorter than reported in the literature. Furthermore, formation of by-products, i.e., hydrocarbons, could be prevented by choosing the right process settings. Hydrogen concentration turned out to be the key parameter for achieving the above two goals. As a result of the supercritical conditions, we could control the hydrogen concentration at the catalyst surface independently of the other process parameters. When methylated rapeseed oil was used as a substrate, the hydrogenation catalyst was deactivated rapidly. However, by using methylated sunflower oil, a catalyst life similar to that obtained in industrial processes was achieved. Our results showed that the hydrogenation of FAME to FOH at supercritical conditions is a much more efficient method than any other published process.
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| 3. |
- Van den Hark,, et al.
(författare)
-
Production of fatty alcohols by heterogeneous catalysis at supercritical single-phase conditions
- 2000
-
Ingår i: Studies in Surface Science and Catalysis. - 0167-2991. ; 130 A, s. 539-544
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Tidskriftsartikel (refereegranskat)abstract
- Fatty alcohols can be produced by catalytic hydrogenation of fatty acid methyl esters. This heterogeneous catalytic reaction, traditionally performed in a multi-phase system, is limited by the mass transport of hydrogen to the catalyst. To overcome this limitation we have used the unique properties of supercritical fluids, properties which are in between those of liquids and gases, making them a very suitable medium for reactions. By adding propane to the reaction mixture of hydrogen and fatty acid methyl esters we have created supercritical single-phase conditions. These single-phase conditions eliminate the transport resistance for hydrogen and create the possibility to control the concentration of all the reactants at the catalyst surface independently of the other process settings. In this way, extremely rapid hydrogenation can be combined with a high product selectivity. In our lab-scale experiments the catalyst activity was studied as a function of hydrogen pressure, substrate concentration and temperature. The catalyst activity was extremely high compared to the multi-phase hydrogenation. Complete conversion of the liquid substrate was reached in a few seconds. The high catalyst activity results in reaction rates which are comparable with similar gas-phase hydrogenation reactions of much smaller molecules (e.g. methylacetate). As long as single-phase conditions remain -in our experiments we have tested up to 15 wt.% substrate- the gas-phase-like activity can be maintained. Our results prove that performing hydrogenation at supercritical single-phase conditions is beneficial for this and other heterogeneous catalytic processes which are limited by mass transfer. © 2000 Elsevier Science B.V. All rights reserved.
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