Ultra-deep hydrodesulfurization of kerosene for fule cell system (part 3) development and evaluation of Ni/ZnO catalyst

摘要

Adequate regeneration of NiS in simple Ni/ZnO model catalysts was certified by highly accelerated long runs of theadsorptive ultra-deep hydrode sulfurization (UD-HDS)reaction of kerosene in the laboratory.Then,model Ni/ZnO catalysts containing 5 wt% and 12 wt% Ni were developed and evaluated in bench plant long life tests.From the results,a practical Ni/ZnO catalyst estimated to have a one-year life was selected.Preparations of catalysts were carried out checking the surface ratio of Ni by chemisorption of NO on a reduced Ni form.In kinetic studies,the apparent reaction order,activation energy,reaction order of H_2 and reaction order of CO_2 were 1.9-2.2,31 kJ/mol,0.18,and -2.0,respectively.200 l of 12wt% Ni/ZnO catalyst was certified by long life evaluations as an auto-regenerative adsorptive UD-HDS catalyst for the 200kW kerosene-fed phosphoric acid fuel cell (PAFC) system,whichwas estiamted to produce kerosene containing 0.025-0.040 wtppm sulfur for at least 5900 h or operation.Becasue fo the small influence of H_2 partial pressure,thelong run was attained under near atmospheric pressure of 25% CO_2 containig H_2.By the end of the catalyst life,36mol% of ZnO was consumed as the acceptor of H_2S.The activity of Ni/ZnO catalyst is controlled by the balance of pisoning rate and regeneration rate of surface Ni.The life of the Ni/ZnO catalyst was theoretically interpreted as functions of the regeneration rate of NiS,the rate of sulfur charge,tecontent of ZnO,and thediffusion resistnace of H_2S.