Effect of the calcination temperature on Ni/MgAl2O4 catalyst structure and catalytic properties for partial oxidation of methane

Abstract

Effect of calcination temperature on Ni/MgAl2O4 catalyst was investigated in order to evaluate changes on structural and catalytic properties for catalytic partial oxidation of methane. The catalysts were calcined at different temperatures after impregnation of nickel salt solution on MgAl2O1 support. The prepared catalysts showed nearly 89% CH4 conversion and 99% H-2 selectivity under the flow of 157,000 (l kg(-1) h(-1)) with the ratio of CH4/air = 0.44 at 1 atm and 800 degrees C. However, turnover frequency values of the catalysts were between 8.2 and 42.3 s(-1) and increased according to Ni particle size. Lewis basicity/acidity ratio increased from 2.14 to 4.46 with increasing calcination temperature. It was found that coking rate on the catalysts depends on Ni particle size and surface basicity/acidity. The experimental results showed that calcination temperature and time have a significant influence on both structural and catalytic properties of the catalysts that show strong metal oxide support interaction. It could be claimed that high calcination temperatures could be beneficial to obtain highly active, selective and stable Ni/MgAl2O4 catalysts, which possess strong metal oxide support interaction, by maintaining Ni dispersion high after reduction, increasing surface basicity and enhancing the stability of Ni particles against sintering. (C) 2013 Elsevier Ltd. All rights reserved.