Effect of MgAl2O4 catalyst support synthesis method on the catalytic activity of nickel Nano catalyst in reverse water gas shift reaction

In this research effect of synthesis method of magnesium aluminate as support of Ni catalysts at the reverse water gas shift (RWGS) reaction was evaluated. The RWGS reaction is applied in Carbon Dioxide Hydrogenation to Form Methanol via a Reverse Water-Gas Shift Reaction (CAMERE) process for the transformation of CO2 into methanol. The MgAl2O4 supports were prepared by sol-gel (M1), surfactant-assisted co-precipitation (M2) and ultrasonic-assisted co-precipitation (M3) techniques. 1.5wt.% Ni/M1 showed highest CO2 conversion (42.1%) and lowest CO selectivity, while 1.5wt.% Ni/M2 showed the lowest CO2 conversion and the highest CO selectivity (>92.5 %). The 1.5wt.% Ni/M3 showed similar catalytic activity as 1.5 wt.%Ni/M2, but with lower CO selectivity. The high CO selectivity of 1.5 wt.% Ni/M2 with a BET surface area of 121.7 m2g-1 was accredited to a higher dispersion of Ni particles resulted by higher total pore volume of this catalyst. High specific surface area along with large total pore volume, is effective in increasing the nickel dispersity. The following pore size distribution and total pore volume order was obtained for catalysts: 1.5wt.% Ni/M2> 1.5wt.% Ni/M3> 1.5wt.% Ni/M1. Among the prepared supports, M1 with BET of 174.5 m2.g-1 showed the highest specific surface area. All prepared supports and catalysts possessed mesoporous structure. Well dispersed NiO species with high interaction with the support were detected by TPR analysis. The SEM images detected particles with less than 80 nm for M2 and 1.5wt.%Ni/M2 samples. The long term stability test performed on 1.5wt.%Ni/M2 showed great catalytic activity after 15h on stream.