Method of preparing high activity hydrotreating catalysts
This disclosure relates to supported multi-metallic catalysts for use in the hydrotreating of hydrocarbon feeds, as well as a method for preparing such catalysts. The catalysts are prepared from a catalyst precursor comprised of at least one Group VIB metal, at least one Group VIII metal and an organic acid. The catalyst precursor is thermally treated to partially decompose the organic acid, then sulfided. The catalysts have a high carbon-as-carboxyl to total carbon ratio (C carboxy /C total ) as a result of a unique post-metal calcination method employed during the manufacture of the catalyst.
1. A method for preparing a catalyst precursor composition suitable for hydrotreating hydrocarbon feedstocks, the method comprising:
(a) impregnating an inorganic catalyst support, the support comprising a porous inorganic refractory selected from the group consisting of silica, alumina, alumina-silica, and crystalline silica-alumina with an aqueous solution containing (i) a salt of a Group VIB metal selected from Mo and W, (ii) a salt of a Group VIII metal selected from Co and Ni, and (iii) an organic acid wherein the organic acid is a hydroxycarboxylic acid selected from the group consisting of glycolic acid, lactic acid, glyceric acid, gluconic acid, malic acid, tartaric acid, mucic acid, and citric acid;
(b) drying the impregnated catalyst support, thereby resulting in a metal-organic component on a dried catalyst precursor;
(c) calcining the dried catalyst precursor in an oxygen-containing atmosphere for a time and temperature sufficient to oxidize some but not all of the organic portion of the metal-organic component, thereby resulting in a partially oxidized catalyst precursor having:
(i) a loss-on-ignition of greater than 1 wt. % and up to 10 wt %; and
(ii) a carbon-as-carboxy to total residual carbon ratio (C carboxy /C total ) of from 0.10 to 0.19 and determined by X-ray photoelectron spectroscopy; and
wherein: (1) loss-on-ignition is determined using a test conducted by heating a sample of the partially oxidized catalyst precursor in an oxygen-containing atmosphere for 1 hour @ 1020° F. (549° C.) and measuring weight loss alter such heating; and (2) calcining is carried out for a time of from 1 minute to 1 hour at a temperature of 350° C. to 500° C.
2. The method of claim 1 , wherein the inorganic catalyst support is selected from the group consisting of alumina, silica, and alumina-silica.
3. The method of claim 1 , wherein the aqueous solution further comprises at least one phosphorus-containing acidic component.
4. The method of claim 1 , wherein the calcining is carried out at a temperature of from 360° C. to 500° C.
5. The method of claim 1 , wherein the calcining is carried out at a time of from 5 minutes to 1 hour.
6. The method of claim 1 , wherein the partially oxidized catalyst precursor has a loss-on-ignition of greater than 1 wt. % and up to 8 wt. %.
7. The method of claim 1 comprising:
(d) sulfiding the partially oxidized catalyst precursor at sulfiding conditions in the presence of a sulfiding agent, thereby resulting in a sulfided catalyst composition.