Key points are not available for this paper at this time.
Abstract The selection of appropriate catalysts is critical for the efficient operation of hydrotreaters, due to the diverse types of reactions inherent to the process. In this study, various Type I and Type II sulfided NiMo/γ-Al 2 O 3 hydrotreating catalysts were prepared using chelating agents and support modification, and the apparent activity differences were evaluated using step response experiments. The experiments were conducted in a trickle bed reactor at 300 °C and 120 barg using phenanthrene and carbazole as model compounds while the apparent activities were elucidated using dynamic reactor modelling. It was found that the addition of citric acid to the impregnation solution to chelate the Ni leads to an average 30% increase in the active site density for hydrogenation (HDA) and hydrodenitrogenation (HDN), without significantly affecting the reaction rate coefficients suggesting similar activity per active site. Phosphorus modification of the support, however, results in larger reaction rate coefficients for both hydrogenation of phenanthrene as well as adsorption and reaction coefficients for carbazole, resulting in more active catalysts both for HDA and HDN. This enhanced activity is accompanied by increased selectivity to HDN suggesting that catalysts exhibiting higher activity for HDA reactions are more susceptible to inhibition by organonitrogen compounds. In addition, dynamic activity testing indicated that catalysts with superior HDN activity attain their new steady state in the shortest time. Thus, the selection of catalysts for efficient hydrotreater operation necessitates activity testing under dynamic conditions to account for competing and inhibitory reactions, rather than relying solely on steady-state activity. Such an approach, allows for the elucidation of the differences in HDA and HDN activity, providing valuable insights to support the catalyst selection process.
Björkman et al. (Tue,) studied this question.