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Catalytic Reforming Catalysts
Published in Soni O. Oyekan, Catalytic Naphtha Reforming Process, 2018
After the formation of the shaped alumina pellets or “extrudates,” platinum, promoter metals, and chloride impregnations are conducted so as to deposit the necessary calculated concentrations of platinum, promoter metals, and chloride on the alumina. Precursor metal compounds such as chloroplatinic acid, perrhenic acid, ammonium perrhenate, hydrochloric acid, and stannous chloride are used. Depending on the catalyst to be manufactured, the appropriate set of precursor metal compounds, hydrochloric acid, and impregnating agents are used. Hydrochloric acid and carbon dioxide have been used as impregnating agents to facilitate uniform distributions of platinum, promoter metals, and chloride. After the metal and chloride impregnation step, drying and calcination procedures are conducted at moderate temperatures to complete the catalyst production.
Kinetics of rhenium extraction with trioctyl ammonium hydrosulfate from sulfuric acid media
Published in Gülhan Özbayoğlu, Çetin Hoşten, M. Ümit Atalay, Cahit Hiçyılmaz, A. İhsan Arol, Mineral Processing on the Verge of the 21st Century, 2017
A.N. Zagorodnyaya, E.I. Ponomareva, Z.S. Abisheva, T.N. Bukurov, A.K. Tulekbaeva
Trioctyl ammonium hydrosulfate was used as an extractant, it was produced by contacting pure TOA with 0.25 mol/L sulfuric acid solution. Rheniumcontaining sulfuric acid solutions were prepared by using ammonium perrhenate of “AP-O” brand and sulfuric acid of chemical purity qualification. Rhenium quantity was determined by colorimetric and gravimetric methods (Borisova & Ermakov, 1974). The study of the kinetics of rhenium extraction was accomplished by using diffusion cell (Lewis cell) with the constant interface (S = 7.54×10−4 m2, v = 0.06 L, a = 0.125 cm−1) according to the method (Tarasov & Yagodin, 1984).
Hydrometallurgy
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
There are three main sources of rhenium that are generated in the processing of molybdenite concentrates. They are (1) the dusts obtained in the roasting of molybdenite, (2) the acid solutions of the wet-dust collecting system, and (3) the liquors remaining after the completion of hydrometallurgical processes involving alkali leaching of low-grade molybdenite cinders. The processing routes for recovering rhenium from the first two sources have been described in the section dealing with ion exchange. Recovery from the third one will be described here as an example of carbon adsorption. The flowsheet of the process is shown in Figure 40. The solution is acidified to pH 3 and heated to expel the carbon dioxide contained (the starting solution contains sodium carbonate). The cold filtered solution is then passed through an ion exchange column filled with an anion exchange resin, Espatite AN-1, in the sulfate form. In the weakly acidic solution molybdenum is present as the anion of isopolyacids (e.g., (Mo4O13)2− anions) which are adsorbed on the resin. Molybdenum is eluted with ammonium hydroxide solutions. The resin is then charged again with sulfate ions by passing sulfuric acid through the column. The ReO4− ions are not adsorbed on the anion exchange resins. The renium-bearing solution is then passed through activated carbon, which adsorbs rhenium and molybdenum quantitatively. The molybdenum may be desorbed first from the carbon with a cold 1% solution of sodium carbonate. This may be followed by rhenium desorption with a sodium carbonate solution heated to about 90°C. Concentrated solution of rhenium is obtained by repeating the sorption on the carbon. This concentrated solution is evaporated and potassium perrhenate is precipitated by heating and the addition of potassium chloride. On subsequent cooling, crystalline precipitates consisting of technical potassium perrhenate separate. Several successive recrystallization steps are carried out for the purification of the technical potassium perrhenate so obtained. While metallic rhenium can be produced by thermally reducing potassium perrhenate with hydrogen (KReO4 + 3.5H2 → Re + KOH + 3H2O), the most common method utilizes an ammonium perrhenate intermediate for the production of rhenium powder. The known processes for producing ammonium perrhenate from potassium perrhenate are shown in Figure 41.
Study on Extraction Behavior of Re(VII) with Bis-triamide Extractants
Published in Solvent Extraction and Ion Exchange, 2021
Xiaoyuan Zhou, Rulei Wu, Jinyang Kang, Yu Fan, Chao Huang, Yongdong Jin, Chuanqin Xia
In spent nuclear fuel and radioactive waste, 99Tc is one of the most-problematic radionuclides with 6.1% fission yield,[1,2] which mainly occurs in the form of pertechnetate anion (TcO4–) in the radioactive waste. In the PUREX process, Tc(VII) would be co-extracted with UO22+ or Pu4+ in the form of Mn+(NO3–)x(TcO4–)n-x, (Mn+ = UO22+, Pu4+).[3] The environmental mobility makes TcO4– migrate easily to the groundwater system.[4] In addition, TcO4– would transform into the volatilizable Tc2O7(g) under high temperature such as the process of vitrification.[5] Therefore, the separation of TcO4– from radioactive waste has always got high attention.[6] Perrhenate (ReO4–) is often used as a nonradioactive surrogate for pertechnetate (TcO4–) owing to their similar electronic configuration, stereochemistry and thermodynamic properties.[7]