Ultra-deep Hydrodesulfurization of Kerosene for Fuel Cell System (Part 1) Evaluations of Conventional Catalysts

摘要

Catalysts for conventional hydrodesulfurization (HDS) were evaluated fro use in effective ultra-deep HDS (UD-HDS) of JIS No.1 kerosene to attain sulfur content of 0.1 wt ppm maximum under below 1 MPaG. Analysis of the JIS No.1 kerosene showed a wide sulfur distribution consisting light to heavy sulfur compounds. Then, the original reaction order of kerosene, n=1.3 in the refinery, changed to n=2.0. A concentrated Ni-Mo/Al_2O_3 catalyst for petroleum middle distillates was selected as one of active parts of a combined catalyst for large phosphoric acid fuel cell (PAFC). A tailor-made Ni-Mo/Al_2O_3 catalyst that was improved to meet the HDS of the large sulfur compounds proved to clear the target. To keep the activity of Ni-Mo/Al_2O_3 catalysts, a recycling procedure of H_2S became necessary, which may be difficult in a small PAFC package. An adsorptive HDS using a conventional HDS catalyst without pre-sulfurization was more acive than the usual HDS using the presulfurized catalysts. The catalyst, however, could not realize the target. On the contrary, an adsorptive HDS using a reduced Ni catalyst was most active in this study. The life of the reduced Ni catalyst is short for a practical long operation. However, the catalyst showed a possibility to develop a new Ni catalyst, and seemed hopeful for a large PAFC combining with the conventional concentrated Ni-Mo/Al_2O_3 catalyst. Further, in the sensitive UD-HDS experiment, some poisonous compounds from the caulking of the metallic cans were found.