Sugar Hydrogenation

Evonik is a world leader in sugar hydrogenation catalysts due to its molecular approach to this chemistry. As seen below for the mutarotation and hydrogenation of glucose, sugars exist as two main types of alpha- and beta-anomeric forms in solution. The alpha- and beta-pyranose rings are favored by C6 aldoses where the terminal hydroxyl group is on the fifth carbon from the reducible anomeric carbon (e.g., glucose, maltose and lactose). They are very stable, strongly adsorbed and more difficult to reduce than the furanose ones. The alpha- and beta-furanose rings have higher concentrations in the solutions of sugars where the terminal hydroxyl group is on the fourth carbon from the reducible anomeric carbon (e.g., xylose) and ketoses (e.g., fructose and isomaltulose). The furanose rings are readily reduced and their hydrogenation rate is slower than mutarotation, hence a small furanose concentration can accelerate the hydrogenation more than its equilibrium concentration would suggest. Moreover, the presence of Mo on the catalyst lowers the activation energy, increases selectivity and increases hydrogenation activity via the polarization of the anomeric carbon5. Therefore the type of sugar will determine the optimal catalyst for its hydrogenation.

Example: The mutarotation and hydrogenation of glucose.

The Activated Nickel Catalysts for Sugar Hydrogenation:

• BK 111 W
• BK113 W
• MC 805
• and variations thereof.

Please see your local Evonik representative for further details.