Ultra-deep hydrodesulfurization of kerosene for fuel cell system (part 2) regeneration of sulfur-poisoned nickel catalyst in hydrogen and finding of auto-regenerative nickel catalyst

An idea to regenerate sulfur-poisoned Ni catalyst in flowing H-2 was tried. That is, sulfur-poisoned Ni catalyst particles are mixed with ZnO fine particles in a H-2 atmosphere at 600 K, then the each poisoned catalyst particle would releases a few ppb of H2S through the H-2 atmosphere and the released H2S would be accepted on neighboring ZnO particles. Then, a million-fold effective improvement in the regeneration of sulfur-poisoned Ni catalyst in a flow of H-2 would be realized. After only a 90 h of trial operation, sulfur-poisoned 60% Ni/Al2O3 catalyst was regenerated. Applying this idea, 12.3% Ni/ZnO was prepared and tested as a model catalyst for adsorptive ultra-deep hydrodesulfurization (UD-HDS) of kerosene in a stream of H-2 containing 25% CO2 at 600 K. Residual sulfur in the treated kerosene was not detectable (< 0.06 wt ppm) by the ready-made sensitive sulfur analyzer even after 800 h of operation. Comparing with the conventional Ni/Al2O3 catalyst, the Ni/ZnO catalyst did not produce any CHI. The ZnO support is regarded to serve as a kind of SMSI and to regenerate Ni catalyst automatically in the HDS. To the best of our knowledge, this is the first time that the regeneration of the sulfur-poisoned Ni catalyst in a H-2 stream was realized and the automatic regenerative Ni catalyst fur adsorptive HDS was demonstrated. Other materials for the catalyst of adsorptive UD-HDS were investigated. Al2O3 and Fe2O3 were useful as sub-materials, however, Cu, Co, Mo, Pd, and Pt were not comparable to Ni and ZnO.