The influence of nickel loading on reducibility of NiO/Al 2 O 3 catalysts synthesized by sol-gel method

Abstract

The sol-gel method was used to synthesize nickel-alumina catalysts with various nickel loadings. Chemical and physical properties of support and supported nickel were characterized by TGA, DTA, EDX, SEM, BET, XRD and TPR techniques. Calcination temperature (500°C) was determined by performing thermogravimetric and differential thermal analysis on the samples. Energy dispersive X-ray (EDX) was used to determine the actual content of nickel on alumina. N 2 adsorption test revealed that the specific surface area varied between 550 and 223 m 2 /g for pure alumina and 30%Ni/Al, respectively. X-ray diffraction patterns showed no peaks due to NiO species and NiO species were well dispersed on the support by formation of NiAl 2 O 4 phase. Temperature-programmed reduction (TPR) indicated that the nickel species mainly presented in NiAl 2 O 4 phase and small amount of NiO. In the 20 percent nickel loading, the surface NiAl 2 O 4 phase, which is between NiO and bulk NiAl 2 O 4 phases in terms reducibility, was formed considering as a successful result. Keywords: Nickel-alumina catalysts; sol-gel method; thermogravimetric analysis; dispersion of NiO; reducibility DOI = 10.3329/cerb.v14i2.5052 Chemical Engineering Research Bulletin 14 (2010) 97-102