Infrared spectroscopy characterization of Ni-Cu /g-Al2O3 bimetallic catalysts: Understand and control the selectivity in the hydrogenolysis of glycerol
EMSL Project ID
48209
Abstract
The proposed project aims at the characterization of adsorbed of CO on Ni-Cu/g-Al2O3 catalysts by FT-IR spectroscopy. The total metal loading in the samples is 10 % wt. The interaction between Ni and Cu is likely related to either the formation of Ni-Cu alloy or isolated phases and it is the key parameter for the elucidation of the selectivity control in the glycerol transformation to value-added compounds. Analysis of the IR spectra will provide detailed information about the structure of the Ni-Cu bimetallic catalyst systems. Glycerol is an important molecular building block in the production of many high-value chemicals. During the production of biodiesel by transesterification of vegetable oils, around 10% of glycerol is generated as byproduct, leading to large surpluses of this material. Therefore, it is necessary to improve the conversion efficiency of glycerol into value-added products. Ni-Cu is a good example of a bimetallic catalyst system in which the variation of catalytic activity with composition depends markedly on the type of reaction, thus leading to substantial selectivity effects. Our previous work (Applied Catalysis B: Environmental 147 (2014) 464– 480) revealed that glycerol reaction pathways over 10%Ni//?-Al2O3 is based on dehydration, dehydrogenation and hydrogenolysis steps (Sheme 1). The main products identified were: hydroxyacetone, pyruvaldehyde, pyruvic acid, lactic acid, lactide, acetaldehyde and methane. The chemisorbed intermediate in hydrogenolysis is probably a hydrogen-deficient organic specie which forms a number of bonds with the surface of the Ni metal atoms of the catalyst. The probability of finding a suitable array, or multiplet of active metal atoms to accommodate such an intermediate greatly decreases when Cu is dispersed on the Ni catalyst surface. By contrast, the chemisorbed intermediate in the dehydrogenation presumably does not require a site consisting of a number of active metal atoms and is therefore relatively less sensitive to coverage of the surface with Cu. The preliminar measurements at EMSL of IR spectra of the representative bimetallic sample (10%Ni-Cu/?-Al2O3 (atomic ratio Ni/Cu=1)) revealed that with the addition of copper, bands at 1950-1910 cm-1 correspondent to the presence of bridged CO species (denoted B1 and B2, respectively) on reduced 10% Ni/?-Al2O3 disappear. In view of the low ability of copper relative to Ni to chemisorb a variety of organic compounds, it might reasonably be expected that the addition of copper to nickel would then inhibit the deep hydrogenolysis towards methane.
Project Details
Project type
Limited Scope
Start Date
2014-01-20
End Date
2014-03-22
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Chimentao RJ, BC Miranda, J Szanyi, C Sepulveda, JBO Santos, JV Correa, J Llorca, and F Medina. 2017. "Sources of deactivation during glycerol conversion on Ni/?-Al2O3." Molecular Catalysis 435:49-57. doi:10.1016/j.mcat.2017.03.023
Chimenton R.J., R.J. Chimentao, B.C. Miranda, J. Szanyi, C. Sepulveda, J.O. Santos, and J.V. Correa, et al. 2017. "Sources of deactivation during glycerol conversion on Ni/?-Al2O3." Molecular Catalysis 435. PNNL-SA-124806. doi:10.1016/j.mcat.2017.03.023
Miranda BC, RJ Chimentao, J Szanyi, AH Braga, JBO Santos, F Gispert-Guirado, J Llorca, and F Medina. 2015. "Influence of copper on nickel-based catalysts in the conversion of glycerol." Applied Catalysis. B, Environmental 166-167:166-180. doi:10.1016/j.apcatb.2014.11.019