No abstract

Improvement of the selectivity of hydrodesulfurization (HDS) to hydrogenation (HYD) of olefins is crucial to produce sulfur-free gasoline (S < 10 ppm) from fluid catalytic-cracked (FCC) gasoline. CoMo/SiO 2 catalyst, which was less acidic than CoMo/Al 2 O 3 catalyst, showed higher HDS/HYD selectivity than CoMo/Al 2 O 3 catalyst under mild reaction conditions, although both HDS and HYD activities were lower for the former catalyst. However, under more severe reaction conditions, HDS/HYD selectivity over CoMo/SiO 2 catalyst decreased to a significantly greater extent than that over CoMo/Al 2 O 3 catalyst. NO adsorption measurements indicated that the formation of coordinatively unsaturated sites (CUS) over CoMo sulfides was more dependent on the reaction severity over the SiO 2 supports. FT-IR data of adsorbed pyridine clearly showed that the strength of Lewis acidity over CUS, in particular, mainly formed under high-temperature conditions, was greater for CoMo/SiO 2 catalyst than for CoMo/Al 2 O 3 catalyst. These results suggest that strong Lewis acid sites over CUS promote a hydrocracking reaction in olefins: however, it is not more disadvantageous than HYD reactions in terms of octane loss. Controlling the Lewis acid properties over CoMo sulfides is effective in selective HDS of FCC gasoline, even when using nonacidic supports.

Electric Arc Furnace (EAF) dust, defined as special industrial waste in Japan, is treated through pyrometallurgical processes in which crude ZnO powder is recovered. An on-site type process, however, is desired to reduce treatment cost and cost of transportation of the dust. A hydrometallurgical process is considered to be suitable for such an on-site treatment. Although many EAF dust treatment processes by hydrometallurgical method have been proposed, most of them have not been commercialized in Japan. A short review of hydrometallurgical processes for EAF dust was done and a new hydrometallurgical process for EAF dust was proposed in this study. Nitric acid solution is used for the extraction of ZnO from the dust. Some characteristics of the process are as follows:(1) Recovery of Zn from zinc ferrite in EAF dust is the target, while the dissolution of Fe is limited by controlling the pH of the solution. (2) Zn is recovered as metallic Zn by electrowinning from the solution and nitric acid is regenerated in the anode.

The present study investigated the effects of Co addition on the surface structure and activity of Mo/Al2O3 for the hydrogenation of C6-C10 olefins. CoMo/Al2O3 (Co/Mo atomic ratio: 0.56) had lower activity for the hydrogenation of 1-hexene, 1-octene and 1-decene than Mo/Al2O3, whereas CoMo/Al2O3 had higher activity for the hydrogenation of 2-octene, 2,4,4-trimethyl-2-pentene and cyclohexene. Co/Al2O3 showed no activity for the hydrogenation of 1-octene and 2,4,4-trimethyl-2-pentene. NO uptake measurements over Mo/Al2O3 suggested that the coordinatively unsaturated sites of Mo atoms located at the edges of MoS2 clusters were active for the hydrogenation of both 1-octene and 2,4,4-trimethyl-2-pentene. Diffuse reflectance FTIR measurements of NO adsorbed on CoMo/Al2O3 (Co/Mo atomic ratio: 0.56) indicated that Co atoms blocked Mo atoms located at the edges of MoS2 clusters almost completely, i.e. formation of the Co _ Mo _ S structure. Therefore, formation of the Co _ Mo _ S structure depressed the activity for hydrogenation of 1-octene. The addition of Co promoter also increased the stacking number of MoS2 clusters. Presumably the increase in the stacking number of MoS2 clusters facilitated the adsorption of bulky olefins and promoted the hydrogenation. This may be the main reason for the promoting effect of Co for the hydrogenation of 2,4,4-trimethyl-2-pentene.

No abstract