Naghi Saadatjou
Semnan University, Iran
Title: The effect of hydrogen and chemical treatments of activated carbon in the synthesis of Ammonia on the promoted Ruthenium catalyst
Biography
Biography: Naghi Saadatjou
Abstract
In this work, the activated carbon without any treatment (AC), AC with hydrogen treatment at 900 °C for 24 h (ACH) and ACH with HNO3 treatment at 90 °C for 5h in the reflux system (ACHN) were used as a support for ruthenium catalyst. They were impregnated by RuCl3, Ba(NO3)2 and KOH solutions, then were reduced by H2 at 400°C for 4 h. They were used as ammonia synthesis catalyst. The physical and chemical properties of catalyst samples were characterized by applying nitrogen adsorption/desorption, TEM, SEM, EDS and XRD methods. The ammonia synthesis activity was evaluated in the fixed-bed reactor set-up under near-commercial operating conditions (that is, T: 400-450°C, P: 30 bar, H2/N2:3/1). It was found that the treatment of activated carbon support with hydrogen (ACH) and hydrogen/HNO3 (ACHN) significantly enhanced both activity and stability of catalysts although the textural properties little influenced. According to the support type, the order for both activity and stability was ACHN>ACH>AC. The best performance was obtained for K-Ba-Ru/ACHN sample due to the removal of chlorine and sulfur impurities and formation of oxygen-containing surface functional groups after hydrogen and HNO3 treatment of AC support that resulted to good dispersion of Ru and promoters. The reaction was found not to be intra-particle diffusion limited. A second order rate expression was proposed for deactivation kinetics of the catalysts and numerical values of 0.016 and 0.0018 h-1 were obtained for rate constant of deactivation of K-Ba-Ru/ACH and K-Ba-Ru/AC catalysts, respectively.