Selective removal of sulphur in liquid fuels for fuel cell applications

Fuels like diesel and gasoil must be desulphurised to extremely low levels before being used as hydrogen source for modern fuel cell applications and to avoid sulphur poisoning of therein used catalysts. A commercial Ni/NiO-sorbent has been identified as being able to remove even refractory sulphur species like 4,6-dimethyldibenzothiophene and the total sulphur concentration is lowered to below 0.2 ppm. The influence of temperature, residence time and level of the sulphur content in the untreated fuel has been investigated in parametric studies. Gas chromatography with mass spectrometric detection (GC–MS) of treated gasoils and diesels reveal which sulphur species are selectively removed and which are left in the fuel. The selectivity and activity of the sorbent can be influenced by the operating temperature. Moreover, GC–MS chromatograms of the breakthrough curves reveal that the sorbent capacity is related to specific sulphur species. Their molecular structure and the alkyl groups at the 4- and 6-positions of dibenzothiophene as well as the C3-benzothiophenes influence the adsorption and the sorbent capacity significantly.