Characterization of Activated Carbon for Oxidative Desulfurization

Removal of sulfur compounds from petroleum streams is one of the most energy-intensive and expensive refinery processes.  Historically, sulfur removal has been achieved using by catalytic reduction of sulfur into hydrogen sulfide, a process termed hydrodesulfurization.  Increasingly, hydrodesulfurization is facing energy and economic challenges due to the difficulty in reducing thiophenic sulfur compounds prevalent in many petroleum feedstocks.  Oxidation of sulfur compounds into highly polar sulfones, a process termed oxidative desulfurization, is a potential alternative or compliment to hydrodesulfurization.  A key to the economic success of oxidative desulfurization is the catalyst.  Here, we describe recent work to characterize activated carbon as a cost-effective oxidative desulfurization catalyst.  Preliminary work showed that wood-based carbons outperformed other carbon types as a catalyst.  Using a suite of techniques, including IR spectroscopy, titration, nitrogen sorption, Raman microscopy, C-XANES, and NH₃-TPD, we found that the most active catalysts 1) had high surface areas, 2) had a high proportion of surface acid and surface oxygen sites, and 3) had a high level of disorganization.  This work will be useful for optimizing and modifying activated carbon for maximum desulfurization activity.