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Guerrero-Perez M.O.,CSIC - Institute of Catalysis | Rojas E.,CSIC - Institute of Catalysis | Gutierrez-Alejandre A.,UNICAT | Ramirez J.,UNICAT | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2011

Ni-containing catalysts are investigated under reaction conditions for two different cases, during sulfidation, with Ni-Mo based catalysts, and during ammoxidation reaction, with the Ni-Nb catalysts. It is shown how Raman spectroscopy can follow some of the transformations of these catalysts upon different treatments. For the NiMo/Al2O3-SiO2 system it was possible to identify some of the sulfided Mo species formed during the sulfidation of the oxide precursors, while for the bulk Ni-Nb oxide catalysts the simultaneous reaction-Raman results strongly suggest that the incipient interaction between niobium and nickel oxides at low Nb/Ni atomic ratios is directly related to catalytic activity, and that a larger size well-defined NiNb2O6 mixed oxide phase is not active for this reaction. Moreover, the promotion by niobium doping appears to be limited to a moderate niobium loading. It was found that in situ and operando Raman are valuable techniques that allowed the identification of active Mo-S and Ni-Nb species under reaction conditions, and that are not stable under air atmospheres. © 2011 the Owner Societies.

Leyva C.,Mexican Institute of Petroleum | Ancheyta J.,Mexican Institute of Petroleum | Travert A.,University of Caen Lower Normandy | Mauge F.,University of Caen Lower Normandy | And 3 more authors.
Applied Catalysis A: General | Year: 2012

NiMo/SiO 2-Al 2O 3 mixed oxide supported catalysts were investigated for hydroprocessing of heavy crude oil at moderate reaction conditions. Hydrodesulfurization (HDS), hydrodemetalization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions were studied as function of time-on-stream (TOS). The results indicated that HDS of crude oil corresponds to the number of active metal sites (sulfide phases) present in the catalyst, HDN is enhanced when the catalyst presents a combination of well dispersed sulfide phases and weak to moderate acidity. HDM presented a complex behavior indicating that it is affected significantly not only by the dispersion of the sulfide phase but also by the porosity and acidity of the catalyst. As expected, for HDAs both acidity and textural properties are important. The stability of the catalyst with time-on-stream was affected by coke and metals deposition. The supports and fresh catalysts were characterized by nitrogen physisorption, SEM-EDX, and FT-IR of CO and pyridine adsorption. The results confirm that NiMo/SiO 2-Al 2O 3 catalysts are a good option for the hydrotreatment of heavy oils and that the method used here for support preparation can tune the formation of meso- or macro-porosity and the type and strength of the catalyst acid sites. © 2012 Elsevier B.V.

Infrared spectroscopy of adsorbed CO and HDS activity for thiophene, dibenzothiophene, and 4,6-dimethyl dibenzothiophene were performed using Mo/Al 2O 3, CoMo/Al 2O 3, and CoMo-EDTA/Al 2O 3 catalysts. The results show differences between the FT-IR absorption coefficients of CO adsorbed on Co-Mo-S sites for CoMo/Al 2O 3, and CoMo-EDTA/Al 2O 3, despite that the vibration frequency of the CO - Co-Mo-S peak in both cases is observed at ∼2071 cm -1. The absorption coefficient is bigger when the level of promotion increases. We propose that the increased absorption coefficient is associated with the change in the local structure of the surface Co sites from tetrahedral/pseudo-tetrahedral, in partially promoted crystallites, to square planar structure in totally promoted zones of MoS 2 crystallites. For simple molecules like thiophene, the HDS activity does not change if Co is in either tetrahedral/pseudo-tetrahedral or square planar structures. In contrast, an open structure like square planar Co favors the accessibility of 4,6-DMDBT to the Co-Mo-S sites, increasing its HDS activity. © 2012 Elsevier Inc. All rights reserved.

Ortiz-Moreno H.,UNICAT | Ramirez J.,UNICAT | Cuevas R.,UNICAT | Marroquin G.,Mexican Institute of Petroleum | Ancheyta J.,Mexican Institute of Petroleum
Fuel | Year: 2012

A study of the influence of reaction parameters (reaction temperature, pressure and catalytic precursor) on the upgrading of Maya heavy oil under low pressure and moderate temperature under slurry conditions is presented. The behavior of the purely thermal hydrotreating system was first characterized to have a basis for distinguishing the effect of incorporating a catalyst in further hydrotreatings. The distillation curves of liquid product were obtained by thermo gravimetric analysis (TGA), ASTM standards were used for evaluation of API gravity and content of asphaltenes and carbenes-carboids. The separated asphaltenes were analyzed by XRD and C 13 NMR techniques. The effect of temperature, catalytic precursor and pressure (800 and 960 psi) of process were studied. The study of thermal hydrotreating showed that 390°C and 400°C were promising temperatures for catalytic hydroprocessing and increasing pressure approximately 100 psi promoted the improvement of light liquid fractions at the expense of the heavy and residua fractions. The use of catalytic precursors at 400°C in concentrations of 330 ppm of Mo increased gasoline production without producing more solids but did not result in the improvement of the liquid yield in comparison to the homologous thermal hydrotreatment. The liquid yield was improved either hydrotreating at 390°C or at 400°C with 1000 ppm Mo as catalyst. © 2012 Elsevier Ltd. All rights reserved.

Rayo P.,Mexican Institute of Petroleum | Ramirez J.,Mexican Institute of Petroleum | Torres-Mancera P.,UNICAT | Marroquin G.,Mexican Institute of Petroleum | And 2 more authors.
Fuel | Year: 2012

In the present work we analyze the changes in hydrocracking, hydrodesulfurization, hydrodeasphaltenization, and hydrodesmetallization, during the hydrotreating of Maya crude, when 3.4 wt.% of P 2O 5 is incorporated by two different routes to a NiMo/Al 2O 3 catalyst. The catalysts were characterized by nitrogen physisorption, XRD, HRTEM, SEM, and CO adsorption analyzed by FTIR. Additionally, to obtain deeper knowledge on the reaction system, the catalysts were also tested in the HDS of 4,6-DMDBT, and hydrocracking of cumene. NiMo/PAl 2O 3 shows the highest HDS activity for 4,6-DMDBT, the better hydrogenating properties, and the best performance in all the reactions during hydrotreating of Maya crude. The acidity and porosity of the catalyst are determinant factor for the conversion of atmospheric residue. At similar acidity, the porosity defines the best catalyst and conversely, at similar porosity, acidity will define the activity of the catalyst. However, an excess of acidity in the catalyst can lead to rapid deactivation. NiMo/PAl 2O 3 displays superior performance compared to NiMo/Al 2O 3 and NiMoP/Al 2O 3 because it presents the best combination of acidity, porosity and distribution of the sulfided Ni and Mo phases, which provide the hydrodesulfurization and hydrogenating functions. © 2012 Elsevier Ltd. All rights reserved.

Gonzalez H.,Universidad Michoacana de San Nicolás de Hidalgo | Castillo O.S.,Universidad Michoacana de San Nicolás de Hidalgo | Rico J.L.,Universidad Michoacana de San Nicolás de Hidalgo | Gutierrez-Alejandre A.,UNICAT | Ramirez J.,UNICAT
Industrial and Engineering Chemistry Research | Year: 2013

In this study, the effect of the metal/acid balance of Pt/mordenite catalysts on the activity, product distribution, and main reaction pathways during the hydroconversion of 2-methylnaphthalene (2-MN) was analyzed. The hydroconversion study was performed on Pt/mordenite catalysts having different metal/acid ratios in a batch reactor at 4.13 MPa (cold charge) and 523-573 K. The catalysts were characterized by XRD, 27Al NMR spectroscopy, FTIR spectroscopy of adsorbed pyridine, and TEM. The results indicate that, by using a bifunctional catalyst consisting of a well-crystallized mordenite whose acid function consists mainly of Brönsted acidity and with a strong hydrogenating function such as dispersed platinum, it is possible to promote the hydroconversion of 2-MN through a complex reaction scheme consisting of isomerization, hydrogenation, ring contraction, ring opening, and cracking. These reactions produce high-value hydrocarbons such as alkyl cycloparaffins, paraffins, and isoparaffins, which decrease the aromatic character of the feed and open a potential route to improve the quality of the polyaromatic-rich fractions. © 2013 American Chemical Society.

Ortiz-Moreno H.,UNICAT | Ramirez J.,UNICAT | Sanchez-Minero F.,National Polytechnic Institute of Mexico | Cuevas R.,UNICAT | Ancheyta J.,Mexican Institute of Petroleum
Fuel | Year: 2014

The effect of the catalyst load in slurry hydrocracking of heavy Maya crude oil was investigated at mild conditions (390 °C and 1400 H2 psi).The catalyst load and operating time were varied in the intervals 0-1000 ppm Mo and 0-11 h respectively. The results allowed to establish the transformation routes of the different fractions under thermal or catalytic conditions. Under thermal conditions, the contributors to gas formation were found to be: Asphaltenes.

Romero-Galarza A.,UNICAT | Gutierrez-Alejandre A.,UNICAT | Ramirez J.,UNICAT
Journal of Catalysis | Year: 2011

HDS activity of 4,6-DMDBT for calcined and non-calcined CoMoP/Al 2O3 catalysts prepared with Co7/2PMo 12O40 was compared with that of a catalyst prepared conventionally by coimpregnation with a solution containing ammonium heptamolybdate, cobalt nitrate, and phosphoric acid. The extent of promotion for each method of preparation was quantitatively determined by CO adsorption, and the intrinsic activity of the different coordinatively unsaturated Mo sites in the catalyst was evaluated. The use of Co7/2PMo12O 40 as catalyst precursor leads to higher HDS activity than the catalyst prepared by coimpregnation. The high activity of the former catalyst was related to a higher number of Co-promoted molybdenum sites. The number of Co-promoted sites depends on the pretreatment before sulfidation, particularly calcination. Highest activity is obtained by avoiding calcination, and the activity decreases with the calcination temperature. Two different types of promoted CoMoS sites with different HDS intrinsic activities seem to coexist in the sulfided catalyst. © 2011 Elsevier Inc. All rights reserved.

Cedeno-Caero L.,UNICAT | Ramos-Luna M.,UNICAT | Mendez-Cruz M.,UNICAT | Ramirez-Solis J.,UNICAT
Catalysis Today | Year: 2011

Titanium oxide nanotubes (TiN) and a titanium-substituted mesoporous SBA-15 molecular sieve were synthesized, characterized and tested in oxidative desulfurization (ODS) of dibenzothiophene compounds prevailing in diesel fuel. Two commercial titanias were used as references. The structural and textural properties of the titania based catalysts were characterized by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM-EDX), and nitrogen adsorption-desorption measurements. The ODS tests were carried out in three-phase (L-L-S) system but also in a two-phase (L-S) system to evaluate the oxidation taking place in the liquid phase only. The reaction results indicate that the best catalytic performance is achieved with TiN and that for the most active catalysts the removal of sulfur could be limited by the mass transfer between the two liquid phases (solvent extraction and oil). © 2011 Elsevier B.V. All rights reserved.

Ramirez J.,UNICAT | Gutierrez-Alejandre A.,UNICAT | Sanchez-Minero F.,National Polytechnic Institute of Mexico | MacIas-Alcantara V.,UNICAT | And 4 more authors.
Energy and Fuels | Year: 2012

HDS of 4,6-DMDBT over NiMoP/SBA-15 and NiMoP/(x)TiSBA-15 catalysts prepared using an heteropolyacid (H 3PMo 12O 40) and nickel citrate (C 12H 10Ni 3O 14) as Mo and Ni precursors was studied. To analyze the effect of calcination temperature on HDS activity, catalysts noncalcined and calcined at 773 K were prepared. The performance of the different catalysts during the hydrodesulfurization of 4,6-dimethyldibenzothiophene was compared with that of a reference catalyst prepared by impregnation with a solution containing ammonium heptamolybdate and nickel nitrate. Kinetic parameters for the HDS of 4,6-DMDBT were estimated using a simplified kinetic model. The catalysts were characterized by N 2 physisorption, X-ray diffraction, Raman, and IR of adsorbed CO at ∼100 K. The results show that for catalysts supported on pure SBA-15 the noncalcined catalyst prepared with H 3PMo 12O 40 (NiMoP(H-nc)/SBA-15) presents the highest number of active sites, the higher apparent reaction rate constant for the hydrogenation route, and therefore the best 4,6-DMDBT HDS activity. In contrast, for Ti-modified catalysts, NiMoP/(x)Ti-SBA-15, the highest HDS activity was found when 15% of TiO 2 was incorporated to SBA-15 and the catalyst was calcined at 773 K. This catalyst presented the highest TOF. © 2011 American Chemical Society.

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