The role of the active phase of Raney-type Ni catalysts in the selective hydrogenation of ?-glucose to ?-sorbitol
2003; Elsevier BV; Volume: 253; Issue: 2 Linguagem: Inglês
10.1016/s0926-860x(03)00553-2
ISSN1873-3875
AutoresB.W Hoffer, E. Crezee, François Devred, P.R.M Mooijman, W.G. Sloof, Patricia J. Kooyman, A.D. van Langeveld, Freek Kapteijn, Jacob A. Moulijn,
Tópico(s)Mesoporous Materials and Catalysis
ResumoBulk and surface properties of homemade Raney-type Ni catalysts and their Ni–Al alloy precursors have been studied and compared with commercial samples, both promoted and unpromoted. The two starting alloys had a different Ni2Al3 concentration, resulting in Raney-type Ni catalysts with different Ni–Al composition. All catalysts have been screened in the hydrogenation of an aqueous solution of d-glucose (10 wt.%) using a three-phase slurry reactor at 4.0 MPa and 393 K. The promoters are segregated at the surface of the catalysts and have a beneficial effect on the reaction rate, essentially due to an increased surface area and stability of the active phase while an enhanced interaction of d-glucose with Ni seems to play a secondary role. The Raney-type Ni catalysts lose Ni and Al at the applied reaction conditions. Mo does not leach at all. Fe leaches severely from the catalyst surface, but about 30% of the Fe at the surface is present as inactive, bulk iron. The major cause of deactivation of the Raney-type Ni catalysts is the presence of d-gluconic acid formed during the reaction. The effect of d-gluconic acid is two-fold: firstly it blocks the Ni sites making them inactive in d-glucose processing. The poisoned catalytic sites can be recovered again by a regeneration treatment in hydrogen at 393 K. Secondly, the formation of d-gluconic acid leads to a severe loss of Ni, which makes product purification necessary.
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