Improved deep desulphurisation of middle distillates by a two-phase reactor with pre-saturator

Abstract

Hydrodesulphurisation (HDS) of middle distillates is up to now performed in trickle bed reactors equipped with an expensive H 2-recycle. To meet future low S-limits, hydrotreating of already pre-desulphurised oils is needed. The H 2-supply is then far beyond what is chemically consumed. In addition, conventional three-phase HDS-reactors are generally problematic with respect to mass transfer, hydrodynamics, and therefore, scale-up. In this paper, an improved HDS-concept based on a two-phase reactor is discussed. The oil is thereby externally saturated with H 2 and only the liquid is passed over the fixed bed. This concept was proven by experiments with light fuel oils (582 and 2252 ppm S, CoMo-catalyst, 1–6 MPa, 330–400 °C, up to 100 days continuous operation). In addition, kinetic studies were done with model oil consisting of a mixture of n-dodecane and selected S-species such as di-, tri- and tetra-methyl-dibenzothiophenes. In case of the presented two-phase concept, the H 2-recycle is redundant, the intrinsic reaction rate can be utilised (and accurately measured), and scale-up problems do not occur.