Kaoline-based catalyst for a high stability desulfurization of sour heavy naphtha in a three-phase oscillatory baffled reactor

Abstract

To meet the rapidly increasing demand for energy and the dramatic depletion of conventional crude oil, it is imperative to utilize sour naphtha. With no coke being produced, oxidative desulfurization (ODS) of naphtha lowers its sulfur content and average molecular weight. In this article, we outline a method for heavy naphtha non-extractive ODS using a very stable catalyst. The technique involves the use of a solid catalyst with oxygen gas as the oxidant. This necessitated relatively high mixing intensities; hence a three-phase Oscillatory Baffled Reactor (OBR) was used. The catalyst was based on the zeolite ZSM-5, prepared from natural kaolin by a series of delamination and activation steps and impregnated with Fe. A TiO2 nanolayer was applied, using the sol-gel method, to prevent rapid deactivation. The reactor performance was evaluated to minimize the sulfur content in the naphtha fuel. Due to the protective coating, the sulfur conversion stabilized at 90%. The results of this work establish the use of natural clay-based catalysts in a continuous, three-phase ODS, particularly with regard to proving long-term stability. It also showed that modest ODS can be achieved using an environmentally friendly oxidant, at mild operating conditions, whilst maintaining stability.