Open AccessPROCESSAMENTO DE CATALISADORES GASTOS DE UNIDADE DE HIDRODESSULFURIZAÇÃO PROFUNDA (ULTRA-DEEP HDS)
Author(s) -
Carolina Leão Quintanilha,
Júlio Carlos Afonso,
Rubens Alexandre da Silva,
Cláudio Vianna,
José Mantovano
Publication year - 2021
Publication title -
química nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.214
H-Index - 73
eISSN - 1678-7064
pISSN - 0100-4042
DOI - 10.21577/0100-4042.20170800
Subject(s) - hydrodesulfurization , chemistry , nuclear chemistry , vanadium , phosphoric acid , leaching (pedology) , raffinate , catalysis , molybdenum , extraction (chemistry) , inorganic chemistry , chromatography , organic chemistry , environmental science , soil science , soil water
PROCESSING OF SPENT ULTRA-DEEP HYDRODESULFURIZATION CATALYSTS. This work discusses the recycling of spent NiMo/Al2O3 catalysts from ultra-deep hydrodesulfurization (HDS) units. They contain a refractory coke and fouling elements from the processed feedstocks. Samples were preoxidized (600 ºC) for 12 h using a very slow heating rate to eliminate coke and volatiles. Experiments were performed in the presence of HF + H2O2 mixtures under stirring at 25-60 oC for 1-4 h. The amount of insoluble matter was the lowest (< 1 wt.% of the initial mass) after leaching for 2 h at 60 oC using an excess of 50 vol.% HF and 20 vol.% H2O2. Leached molybdenum and vanadium were extracted together with Alamine 304 (tri-dodecylamine) in n-heptane at pH below 2. Aluminum and iron were precipitated from the raffinate as Na3AℓF6 (+ Na3FeF6) by adjusting pH at ~4 using 6 mol L-1 NaOH. Nickel was either recovered by solvent extraction using D2EHPA (bis-(2-ethylhexyl)phosphoric acid) in n-heptane at pH 6 or precipitated at pH 8 using 6 mol L-1 NaOH. The first method proved better as less contaminants were present. After slow evaporation of the final aqueous solution, a mixture of Na2SiF6 and NaF was recovered. Fluoride losses were very low (~0.10 wt.%).