Catalysis of Organic..

238Deactivation of Catalyst in Sugar Hydrog.Moreover, in consecutive lactose hydrogenation batches, recycled sponge nickelcatalyst was able to adsorb substantially less hydrogen compared to a fresh catalystaccording to our hydrogen temperature programmed desorption (TPD) measurements.Also, this indicates poisoning of active sites. Regeneration of catalysts poisoned bystrongly adsorbed acidic species may be achieved by catalyst washing in a basicmedium, such as caustic solution. In case of sponge nickel catalyst deactivated bylactobionic acid, we were able to desorb by alkali wash 2 wt-% lactobionic acid of thetotal catalyst amount, thus returning the catalyst activity almost to the original level.However, too high pH during alkali wash of sponge nickel catalyst should be avoided,since at higher alkali concentrations, aluminium and molybdenum leaching increases.An integrated ultrasound treatment of the sponge nickel catalyst during thehydrogenation of sugar species has shown to retard catalyst deactivation by removingstrongly adsorbed organic impurities that occupy active sites (12,13). Furthermore,hydrogen solubility in the reaction mixture may be improved by adding an organicsolvent into the aqueous sugar solution and thus suppressing the formation of aldonicacids and retarding catalyst deactivation. For instance, xylose hydrogenation oversponge nickel catalyst proceeded much faster in ethanol-water solutions and catalystdeactivation was retarded compared to hydrogenations in pure water (14). However,various sugar species have very limited solubilities in organic solvents, which limitsthe use of this method.AcknowledgementsThis work is part of the activities at the Åbo Akademi Process Chemistry Centrewithin the Finnish Centre of Excellence Programme (2000-2011) by the Academy ofFinland. Financial support from the National Technology Agency (Tekes), DaniscoSweeteners and Swedish Academy of Engineering Sciences in Finland is gratefullyacknowledged.References1. D. Yu. Murzin, E. Toukoniitty and J. Hájek, React. Kinet. Catal. Lett., 83, 205 (2004).2. P. Forzatti and L. Lietti, Catalysis Today, 52, 165 (1999).3. D. Yu. Murzin and T. Salmi, Trends in Chemical Engineering, 8, 137 (2003).4. M. Besson and P. Gallezot, Catal. Tod., 81, 547 (2003).5. B. Kusserow, S. Schimpf and P. Claus, Adv. Synth. Catal., 345, 289 (2003).6. K. van Gorp, E. Boerman, C.V. Cavenaghi and P.H. Berben, Catal. Tod., 52, 349(1999).7. P. Gallezot, P.J. Cerino, B. Blanc, G. Flèche and P. Fuertes, J. Catal., 146, 93 (1994).8. J.-P. Mikkola, T. Salmi and R. Sjöholm, J. Chem. Technol. Biotechnol., 74, 655(1999).