Understanding the impact of aluminum oxide binder on Ni/HZSM-5 for phenol hydrodeoxygenation

The properties of supported Ni particles on HZMS-5 and Al2O3-HZSM-5 were comparably investigated by diverse characteristic techniques. Ni/Al2O3-HZSM-5 had at least three times higher concentrations of accessible Ni atoms (average diameter Ni-0: 8.8 nm) compared to Ni/HZSM-5 (average diameter Ni-0 : 35 run), which are consistently evidenced by TEM and XRD as well as H-2 chemisorption and IR spectra of adsorbed CO. The Ni nanoparticles interacted strongly with the binder through the interaction between NiO and Al2O3, explored by the combined extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and H-2 temperature-programmed reduction (TPR) techniques. The Bronsted acid sites on two supports probed by IR of adsorbed pyridine were similar, but Lewis acid sites contributed by the gamma-Al2O3 were more abundant on Al2O3-HZSM-5. The acid sites of the two catalysts responded differently to metal incorporation and subsequent treatments, reflecting changes in Al environments illuminated by Al-27 MAS NMR. In situ IR spectra of adsorbed species demonstrates that Al2O3-HZSM-5 has higher adsorption capacity for phenol, cyclohexanone, and cyclohexanol due to stronger adsorption of these compounds on the gamma-Al2O3 binder. (c) 2012 Elsevier B.V. All rights reserved.