Relative activity of Niobia-supported CoMo hydrodesulphurization catalyst prepared with NTA: A kinetic approach

Abstract

A sulphide CoMo/Nb2O5 HDS catalyst was prepared for the first time using nitrilotriacetic acid (NTA) as complexing agent, where the impregnation solution consisted of NTA, cobalt carbonate and ammonium heptamolybdate. It contained neither NH4OH nor NO3− ions. The hydrodesulphurization activity of the catalyst was tested using as model sulphur compound that of thiophene at 1.0MPa and 400°C. The ratio of activities (based on pseudo-first order kinetics) expressed in terms of the rate constant k, where the latter was estimated from specific reaction rate data per mass of catalyst, for the NTA-CoMo/Nb2O5 and CoMo/Nb2O5 catalysts was found to be 6.6. Thus, using NTA shifted CoMo/Nb2O5 system from a low activity catalyst (as observed in the literature) to a high activity catalyst worthwhile for further investigations (present results). The NTA-CoMo/Nb2O5 (SBET=40m2g−1) was more active than commercial CoMo/Al2O3 (SBET=194m2g−1) not only in terms of specific activity normalized per total surface area (mols m−2s−1, 5.7 times larger) but also in terms of specific activity normalized per mass of catalyst sample (mols g−1s−1, 1.2 times larger).