M. Villarroel

Adsorption of 4,6-Dimethyldibenzothiophene over Cu/ZrO2

The adsorption of refractory sulfur molecule 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over copper supported on zirconia, using different copper loadings (2-10% w/w) and a zirconia support with a high specific surface area, was studied. The results showed that the adsorption capacity of 4,6-DMDBT over Cu/ZrO2 increased with copper content, reaching a maximum at around 8% Cu (0.58 mmol 4,6-DMDBT per gram of adsorbent). The results of characterizations with H2-TPR, Electrophoretic Migration, and XRD demonstrated that this Cu loading (8%) also corresponds to a maximum copper dispersion capacity for ZrO2 support. Also, these absorbents showed considerable selectivity toward the adsorption of 4,6-DMDBT in a feed stream also containing Quinoline, decreasing adsorption capacity of 4,6-DMDBT by only 35%, despite both molecules being present in the same concentrations. The results of this work showed that desulfurization adsorption using Cu/ZrO2 adsorbents can be an effective method to remove this type of refractory sulfur molecules, and an excellent alternative as a complementary process for deep desulfurization in the fuel industry.

STUDY OF THE REMOVAL OF 4–NITROPHENOL FROM AQUEOUS MEDIA BY ADSORPTION ON DIFFERENT MATERIALS

The removal of 4–Nitrophenol (4–NP) from aqueous media by adsorption is studied in a batch system using different porous materials: activated carbon, zirconia, alumina, sepiolite, natural zeolite and 13X zeolite. Depending on their adsorption capacities, the best adsorbent was chosen to be impregnated with different levels of nickel (Ni) in order to study the adsorption by π-complexation in batch and continuous systems. The samples of Ni(x)/support (x= 2, 4, 6%) were prepared by wet impregnation and were characterised using the same method as with all the materials, by N2 adsorption-desorption using the BET method, surface acidity and Z potential measurements by electrophoretic migration. The samples were measured in a UV-Vis electrophotometer at a wavelength of 318 nm, while the adsorption capacity of the material in the batch system was determined by calculating the difference in concentration once the adsorbent became saturated after an initial concentration of ~20 ppm, and in the continuous system this was done by integrating the area under the adsorption curve. The results suggest that adsorption capacity depends on the specific BET area, apparent acid strength and the IEP of each support, and that it varies with the addition of Ni.

DEEP DESULFURIZATION BY ADSORPTION OF 4,6-DIMETHYLDIBENZOTHIOPHENE, STUDY OF ADSORPTION ON DIFFERENT TRANSITION METAL OXIDES AND SUPPORTS

ABSTRACT In this work the adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) on different supports (SiO 2 , Al 2 O 3 , zeolite 4A, zeolite 13X, natural zeolite, and activated carbon), incorporating on its surface different first series transition metal oxides at different content, was studied. The results indicate that the activated carbon presents a higher adsorption capacity than the other supports studied, which it is assumed to the large number of functional groups present on its surface. The incorporation of the first series transition metal oxides on support, induces in some cases the increase of the adsorption capacities of 4,6-DMDBT and these adsorptions capacities depend on metal content. Finally, the desulfurization by adsorption represents an alternative tool for the elimination of refractory sulfur compounds.Keywords: Adsorption, supports, transitions metals, 4,6-Dimethyldibenzothiophene.e-mail: patricio.baeza@ucv.cl 1. INTRODUCTION In recent decades, numerous studies have been reported that over time, the air quality has been getting worse which predicts a unfavorable future; this is the main reason why the recovery of the air quality is one of the prevailing challenges to possible increases in gas emission to the atmosphere.

EFFECT OF FLUORINE IN THE SYNERGISM Co-Mo VIA HYDROGEN SPILLOVER ON THE HYDRODESUL-PHURIZATION OF REFRACTORY MOLECULES

ABSTRACT The influence of fluorine concentration on the synergism between Co/γ-Al 2 O 3 and Mo/γ-Al 2 O 3 stacked beds separated by 3-mm of γ-Al 2 O 3 F x (x = 0 - 2.5%), in the hydrodesulphurization of refractory molecules contained in gasoil, under operating conditions similar to those of industry, was studied. The results shown, that the synergism increases with F content, reaching a maximum at 0.8% of fluorine, which it is related to changes in zero point of charge (ZPC) and acid strength, due to the incorporation of fluorine. The conversion of most refractory molecule reported is favoured by fluorine. Keywords: Hydrodesulphurization, Fluorine, Stacked Bed, Synergism. 1. INTRODUCTION At the present, environmental regulations are becoming more stringent in relation to maximum levels of sulphur allowed in diesel, increasing the inter-est in more efficient systems, in order to obtain fuels that meet the standards. This, coupled with the need to exploit petroleum fractions which have a greater amount of refractory sulphur compounds, and the use of products derived from petroleum that will remain the main energy source, have renewed efforts to develop new catalysts for hydrodesulphurization (HDS)

Synergism of Extruded and Monolithic Co–Mo/γ-AL2O3–Sepiolite Catalytic Systems in the Hydrodesulphurization Reaction

This study evaluates the synergism of γ-alumina supported cobalt-molybdenum samples prepared by impregnation in excess of solvent. These materials were then agglomerated with sepiolite in order to obtain samples of extruded cylinders and honeycomb monoliths shaped. The activity of the gas–oil hydrodesulphurization reaction was measured under reaction conditions similar to those used in industry, and the samples were characterised by using electron probe micro analysis and scanning electron microscopy. It was observed that catalytic activity and synergism are higher in both, the extruded and the monolithic samples, when both, the cobalt and molybdenum were impregnated on separate surfaces (Co//Mo), where it was also possible to observe synergism due to hydrogen spillover. The lowest level of activity observed in the extruded and monolithic bimetallic catalysts (CoMo) may be attributed to the cobalt covering the molybdenum active sites.

SUPPORT EFFECT ON CONVERSION OF QUINOLINE OVER ReS2 CATALYST

The conversion of quinoline over ReS2 supported on g-Al2O3, SiO2, ZrO2 and TiO2 catalysts in a batch reactor at 300◦C and 5 MPa of hydrogen pressure was studied. The catalysts were prepared by wet impregnation with a loading of 1.5 atoms of Re per nm2 of support. The catalysts were characterized by N2 adsorption, X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). The Re(x)/supports catalysts displayed high activities for the conversion of quinoline, although negligible formation of N-free compounds (hydrodenitrogenation) were observed. The intrinsic activities of ReS2 were modified by the support decreased in the order: Re/TiO2 > Re/ZrO2 > Re/SiO2 > Re/g-Al2O3. The highest activity displayed by the Re/TiO2 catalyst was correlated with the Re dispersion and formation of ReS2 species. Meanwhile, the lower conversion of quinoline over the Re/ZrO2, Re/SiO2 and Re/g-Al2O3 catalysts was related to the combined effect of the textural properties of catalysts and the formation of ReS(2-x) species on the supports.

DENITROGENATION BY ADSORPTION OF PYRIDINE ON NI/SUPPORT ADSORBENTS

In this work we have carried out the adsorption of pyridine using three different supports (activated carbon, SiO2 and γ-Al2O3). After choosing the best support, due to its higher adsorption capacity, we have impregnated the support with nickel at three different concentrations (2, 4 and 6% w/w) by wet impregnation to study the adsorption of pyridine by π-complexation. All the samples (supports and adsorbents) were characterized by N2 adsorption-desorption by the BET method and electrophoretic migration. The experimental results, for the three different supports, show that the adsorption capacity is better for γ-Al2O3, due to its higher isoelectric point. With the incorporation of nickel, no better adsorption capacities are observed, due that the nickel incorporation diminish the zero point charges of the adsorbents.

EFFECT OF LIQUID SPATIAL VELOCITY ON M D [M D = Mn, Fe, Co, Ni, Cu AND Zn]//Mo SYNERGISM IN THE HYDRODESULPHURIZATION REACTION

A study is made of Mn//Mo, Fe//Mo, Co//Mo, Ni//Mo, Cu//Mo or Zn//Mo stacked beds systems, separated by g-Al2O3, in the gas-oil hydrodesulphurization reaction, under experimental conditions similar to those industry. The synergism between these beds is clearly detected, and occurs in the absence of mixed phases. The results show that the promotion effect of the pairs in stacked beds, caused by the spillover hydrogen increases when the liquid spatial velocity decreases.