Alfredo Morales

Adsorption mechanism of phosphorus on alumina

Abstract The effect of phosphorus on the acidity and physical properties of a support of γ-alumina was studied, as a preliminary stage to understanding its role as an additive in hydrotreatment catalysts. The results showed that phosphorus was adsorbed on alumina following a Langmuir-type mechanism, in which a phosphate ion monolayer was formed at the surface. Equilibrium was strongly displaced towards adsorption. These results were verified using X-ray photoelectron spectroscopy. Phosphorus modified not only the acidity but also the physical properties of the alumina. From the experimental results obtained, an adsorption mechanism of phosphorus on alumina could be established.

Promoter role of octahedral Co (and Ni) in modified co(Ni) Mo−Al2O3 catalysts for hydrodesulfurization reactions

Abstract The influence of cobalt and nickel promoters on hydrodesulfurization (HDS) activity have been studied using different feeds. The CoMo-type catalyst used in this work were Co-Mo-Al2O3 catalysts modified by acid extraction and calcination. Infrared spectroscopy were used to determine the amount of Co2+ octahedrally coordinated (Co2+) by selective chemisorption of NO. A correlation between HDS activity and the amount of Co02+ has been found. A similar correlation has been obtained using Ni-Al2O3 catalysts modified by phosphorus addition. In this case, the amount of octahedrally coordinated nickel (Ni02+) has been measured by the 405 nm absorption band of the Diffuse Reflectance Spectra (DRS), which also was found to correlate with the surface concentration determined by X-ray Photoelectron Spectroscopy (XPS). These results seem to indicate that octahedrally coordinated nickel and/or cobalt at the surface of the oxide catalyst are possible precursors involved in the formation of the active phase responsible for HDS activity.

Adsorption mechanism of Boscan porphyrins on MoO3' Co3O4and CoMoAl2O3

The adsorption of Boscan porphyrins on Co-MoAl203 and molybdenum and cobalt oxides was studied with the aim of establishing the mechanism of vanadium elimination during the hydrodemetallization (HDM) of heavy oils. The results show a change in the e.p.r. signal of V02+ and in the u.v.-visible bands of the porphyrins adsorbed on the catalyst. This change is not observed on the support alone. Under the hydrotreating conditions used, only the Co-MoAl203 catalysts show a high demetallization activity. As the support alone does not show HDM activity, the cobalt and molybdenum species on the surface, are the demetallization agents.

Hydrotreatment of residuals using a special NiMo-Alumina catalyst

Abstract This article presents experimental results obtained at bench scale using a special NiMo-Alumina catalyst developed by Intevep, S.A. to hydrotreat and demetallize deasphalted oils, heavy crude oils and residuals. Using this catalyst to process residual, it is possible, to reach 92% demetallization under stable operating cycles of more than six months with a feedstock containing less 600 ppm of metals (V+Ni), 17% asphaltenes, 16% Conradson Carbon and API gravity increment higher than 4 degrees, under moderate operating conditions (1500 psi, 340°C, LSHV=1 h −1 ). The technical and economic feasibility of using this catalyst in a conventional refinery to process residuals, is discussed.

Hydroconversion of heavy crude oils using soluble metallic compounds in the presence of hydrogen or methane

Abstract The hydroconversion of heavy crude oil was studied under thermal and catalytic conditions using soluble organo-metallic compounds of Mo, Fe, Cr, V, Ni, and Co as a catalyst precursors. All catalysts are effective for the hydroconversion, however, molybdenum and nickel compounds are preferred. with 250 ppm of acetylacetonate of molybdenum, a reduction of 95% of the amount of coke produced, 22% of hydrodesulfurization and 83% of conversion of the 500°C + residue were obtained. Using methane as a source of hydrogen, 40% and 34% reductions of the amount of coke produced was observed using MoO 2 (AA) 2 and Fe 3 (CO) 12 as metal precursors, respectively, than that found in the control experiment. A relative order of reaction H 2 > CH 4 > N 2 was observed for the crude oil upgrading process. It was found by electron microscopy and XPS analyses of coke produced in the reaction that the metals are present as MoS 2 or FeS. A mechanism was proposed that involves activation of methane by the sulfided metal catalyst (MoS 2 or FeS) via oxidative addition generating hydrogen and a methyl group adsorbed on the surface. According to 1 H-NMR data, the adsorbed methyl group can be incorporated to the crude oil molecules generating methylated aromatic compounds.