Hydrogenation of Lactose over Sponge Nickel Catalysts-Kinetics and Modeling
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- 作者：Jyrki Kuusisto ; Jyri-Pekka Mikkola ; Mona Sparv ; Johan Wä ; rnå ; Heikki Heikkilä ; Riitta Perä ; lä ; Juhani Vä ; yrynen ; Tapio Salmi
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2006
- 出版时间：August 16, 2006
- 年：2006
- 卷：45
- 期：17
- 页码：5900 - 5910
- 全文大小：483K
- 年卷期：v.45,no.17(August 16, 2006)
- ISSN：1520-5045
文摘
Kinetics of lactose hydrogenation to lactitol, an alternative sweetener, over Mo-promoted sponge nickel slurrycatalyst in aqueous solutions was studied. Hydrogenation experiments were carried out batchwise in a three-phase laboratory-scale reactor (300 mL, Parr Co.), operating at 20-70 bar and between 110 and 130 
C. Themain hydrogenation product was lactitol, while small amounts of lactobionic acid, lactulose, lactulitol, sorbitol,and galactitol were detected as byproducts. The lactitol selectivity within the experimental range varied from90 to 99%. The selectivity values improved as the hydrogen pressure increased and the reaction temperaturedecreased. The effect of catalyst loading and catalyst deactivation during consecutive hydrogenation batcheswas also studied. Fresh and recycled catalysts were characterized by nitrogen adsorption, X-ray photoelectronspectroscopy (XPS), scanning electron microscopy (SEM), hydrogen temperature-programmed desorption(TPD), and particle-size analysis. Recycled sponge nickel catalyst was able to adsorb less hydrogen comparedto fresh one, indicating active site poisoning. Of all byproducts, only lactobionic acid had an inhibiting effecton lactose conversion rate and deactivated the catalyst. By lactobionic acid, deactivated catalyst can beregenerated by controlled alkali wash. The kinetic data were modeled by Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics, assuming surface reaction steps are rate determining. Noncompetitive adsorptionof molecular hydrogen and lactose was assumed. The fitting of the experimental data to the kinetic modelwas carried out by a combined Simplex-Levenberg-Marquardt method. The model predicted the experimentalconcentrations of lactose and lactitol very well. A reasonably good description of the byproducts was obtained.
C. Themain hydrogenation product was lactitol, while small amounts of lactobionic acid, lactulose, lactulitol, sorbitol,and galactitol were detected as byproducts. The lactitol selectivity within the experimental range varied from90 to 99%. The selectivity values improved as the hydrogen pressure increased and the reaction temperaturedecreased. The effect of catalyst loading and catalyst deactivation during consecutive hydrogenation batcheswas also studied. Fresh and recycled catalysts were characterized by nitrogen adsorption, X-ray photoelectronspectroscopy (XPS), scanning electron microscopy (SEM), hydrogen temperature-programmed desorption(TPD), and particle-size analysis. Recycled sponge nickel catalyst was able to adsorb less hydrogen comparedto fresh one, indicating active site poisoning. Of all byproducts, only lactobionic acid had an inhibiting effecton lactose conversion rate and deactivated the catalyst. By lactobionic acid, deactivated catalyst can beregenerated by controlled alkali wash. The kinetic data were modeled by Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics, assuming surface reaction steps are rate determining. Noncompetitive adsorptionof molecular hydrogen and lactose was assumed. The fitting of the experimental data to the kinetic modelwas carried out by a combined Simplex-Levenberg-Marquardt method. The model predicted the experimentalconcentrations of lactose and lactitol very well. A reasonably good description of the byproducts was obtained.