Dry reforming of methane on promoted (LA, MG, and RH) NI based catalyst supported on commercial silica

Abstract

Dry reforming of methane is the consumption of two greenhouse gases, methane and carbon dioxide in order to produce hydrogen gas and syngas. Syngas produced is used in a ratio (1:1) that allow the production of hydrocarbon through Fischer-Tropsch synthesis. Hence, this subject is being more interesting due to environmental, economic and energetic point of views. However, dry reforming of methane requires a catalyst that is active and stable under sever conditions such as high temperatures and rapid coke deposition. A nickel based catalyst is used to reduce the economical aspect, and promoters were exploited to increase the properties of that catalyst. In this report, three promoters La, Mg and Rh were studied using different percentages. The support utilized is silica nano-powder (Sigma-Aldrich 637246) which is stable and has a high surface area (590-690 m2 /g). The catalysts obtained are Nix/SiO2 (x =5, 10 and 15 wt %), Ni10La10/SiO2 and Ni10Mg10/SiO2. Whereas for rhodium, Ni10Rhx/SiO2 (x=0.1, 0.225 and 0.5 wt%) were used. The catalysts are then characterized by N2 sorption XRD, TEM and TPR. The catalytic activity tests were conducted at atmospheric pressure where the temperature increased from 200 oC to 800 oC. The stability tests were conducted at a constant temperature of 500 oC for 12 hours. BET surface area decreased as the percentage of Ni and the promoters increased. Upon the addition of promoters, TEM images show that the size particles increased and the dispersion of particles increased upon addition of La and decreased upon addition of Mg. The catalytic activity increased when adding La and Rh. Moreover, Mg showed the highest amount of carbon deposition, which leads to a sudden decrease in CH4 and CO2 conversion. Rhodium was found to increase the activity of the catalyst. Lanthanum had a smaller effect than rhodium where as magnesium did not improve the catalytic activity compared to the Ni10/SiO2. In terms of stability, all the catalysts show no deactivation during the 12 hour; however, the addition of 0.5% Rh induced the activity while being stable significantly.