Nickel-Alumina Catalysts for the Transformation of Vegetable Oils into Green Diesel: The Role of Preparation Method, Activation Temperature, and Reaction Conditions.

Two nickel alumina catalysts containing 60 wt. % Ni were synthesized by wet impregnation and co-precipitation in order to study the effect of preparation methods on the catalytic efficiency concerning the transformation of sunflower oil into green diesel. The effect of activation temperature on the catalytic efficiency of the most active catalyst was also studied.

Mineral Montmorillonite Valorization by Developing Ni and Mo-Ni Catalysts for Third-Generation Green Diesel Production.

Four Ni catalysts and one Mo-Ni catalyst supported on montmorillonite were synthesized, characterized by various techniques and evaluated, under solvent-free conditions, for the production of green diesel from waste cooking oil. The optimum Ni content was found to be 20 wt.%.

Molybdena deposited on titania by equilibrium deposition filtration: structural evolution of oxo-molybdenum(vi) sites with temperature.

The equilibrium deposition filtration (EDF) method, an advanced catalyst synthesis route that is based on a molecular level approach, can be used for tailoring the oxometallic phase deposited on a porous oxide support. Here, the EDF method is used for synthesizing (MoOx)n/TiO2 catalysts. In situ Raman spectroscopy in the temperature range of 25-450 °C, low temperature (77 K) EPR spectroscopy and DR-UV spectroscopy are used for studying the evolution of the structural configuration of oxo-Mo(VI) species on TiO2 with increasing temperature as well as the influence of the supported (MoOx)n species on the photo-generation of electrons and holes of TiO2.

Nano-tubular cellulose for bioprocess technology development.

Delignified cellulosic material has shown a significant promotional effect on the alcoholic fermentation as yeast immobilization support. However, its potential for further biotechnological development is unexploited. This study reports the characterization of this tubular/porous cellulosic material, which was done by SEM, porosimetry and X-ray powder diffractometry.

Effect of pressure and temperature on alcoholic fermentation by Saccharomyces cerevisiae immobilized on γ-alumina pellets.

Saccharomyces cerevisiae was immobilized on γ-alumina pellets and used for repeated batch fermentations in glucose medium (16.5 g/100 mL) at various temperatures and pressures. An increase in pressure from 3 to 7 atm and a decrease in temperature from 30 to 20 °C reduced the ethanol productivity by about 50% and 70%, respectively.

Interfacial impregnation chemistry in the synthesis of nickel catalysts supported on titania.

The interfacial chemistry of the impregnation step involved in the preparation of nickel catalysts supported on titania is presented. Several methodologies based on deposition data, pH measurements, potentiometric mass titrations, and microelectrophoresis have been used in conjunction with diffuse reflectance UV/Vis/NIR spectroscopy, simulations, and semiempirical quantum chemical calculations. Three mononuclear inner-sphere complexes were formed at the compact layer of the "titania/electrolyte solution" interface: A monosubstituted, dihydrolyzed complex above a terminal oxo group, a disubstituted, dihydrolyzed complex above two terminal adjacent oxo groups, and a disubstituted, nonhydrolyzed complex above one terminal and one bridging adjacent oxo groups.

Interfacial impregnation chemistry in the synthesis of cobalt catalysts supported on titania.

The interfacial chemistry of the impregnation step involved in the synthesis of cobalt catalysts supported on titania was investigated with regard to the mode of interfacial deposition of the aqua complex [Co(H(2)O)(6)](2+) on the "titania/electrolyte solution" interface, the structure of the inner-sphere complexes formed, and their relative interfacial concentrations. Several methodologies based on the application of deposition experiments and electrochemical techniques were used in conjunction with diffuse-reflectance spectroscopy and EPR spectroscopy. These suggested the formation of mononuclear/oligonuclear inner-sphere complexes on deposition of the [Co(H(2)O)(6)](2+) ions at the "titania/electrolyte solution" interface.

Mapping the surface (hydr)oxo-groups of titanium oxide and its interface with an aqueous solution: the state of the art and a new approach.

In this article the "titanium oxide/electrolyte solution" interface is studied by taking in advantage the recent developments in the field of Surface and Interface Chemistry relevant to this oxide. Ab-initio calculations were performed in the frame of the DFT theory for estimating the charge of the titanium and oxygen atoms exposed on the anatase (1 0 1), (1 0 0), (0 0 1), (1 0 3)(f) and rutile (1 1 0) crystal faces. These orientations have smaller surface energy with respect to other ones and thus it is more probable to be the real terminations of the anatase and rutile nanocrystallites in the titania polycrystalline powders.

The mechanism of the protonation of metal (hydr)oxides in aqueous solutions studied for various interfacial/surface ionization models and physicochemical parameters: a critical review and a novel approach.

The mechanism of the protonation of solid metal (hydr)oxides in aqueous media was investigated using simulation and experimental work. It was found that the apparent acidity/basicity of each kind of surface sites of metal (hydr)oxides in aqueous suspensions is strongly influenced by the overall surface charge of the (hydr)oxide and thus by the electrical potential smeared out at the interfacial region. Depending on its sign this increases or decreases the hydrogen ion concentration on the surface, thus promoting or hindering protonation.

Kinetics of adsorption of the cobalt ions on the "electrolytic solution/gamma-alumina" interface.

In the present work we studied, for the first time, the kinetics of adsorption of the Co(H(2)O)(6)(2+) species on the "electrolytic solution/gamma-Al(2)O(3)" interface at pH = 7 and 25 degrees C for a very broad range of Co(II) surface concentrations ranged from 0.03 to 6 theoretical Co(H(2)O)(6)(2+) surface layers. Moreover, we studied the surface dissolution of gamma-alumina in the presence of the Co(H(2)O)(6)(2+) ions in the impregnating solution, the contribution of the Co(II) desorption on the whole deposition process and the deposition isotherm.

How metal (hydr)oxides are protonated in aqueous media: the (n+1) rule and the role of the interfacial potential.

The mechanism of the protonation of solid metal (hydr)oxides in aqueous media, which is closely interrelated to many processes of great technological and environmental importance, has been elucidated using simulation and experimental work. The electrical potential, smeared out at the interfacial region, changes the concentration of the H+ ions on the surface of the (hydr)oxide, thus promoting or hindering protonation. This is manifested by the shifts of the protonation peaks of the various kinds of surface sites and the appearance of an extra peak in the differential potentiometric titration curve.

The influence of the preparation method and the Co loading on the structure and activity of cobalt oxide/gamma-alumina catalysts for NO reduction by propene.

In the present work we studied the influence of the preparation method and the Co loading on the physicochemical properties and the catalytic activity of the cobalt oxide/gamma-alumina catalysts for the reduction of NO by propene under net oxidizing conditions. Two series of catalysts containing 1 and 5% w/w Co, respectively, were prepared using three preparation methods, namely, the equilibrium deposition filtration (EDF), the conventional incipient wetness impregnation (IWI) and the IWI adding nitrilotriacetic acid (nta) in the impregnating solution (IWInta). The catalysts were tested at various temperatures in the range 300-550 degrees C using a fixed-bed microreactor for the NO reduction by propene under lean burn conditions.

Differential potentiometric titration: development of a methodology for determining the point of zero charge of metal (hydr)oxides by one titration curve.

A new methodology is presented, called differential potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one potentiometric curve. By performing extensive simulations of potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+(cons,surf) versus pH potentiometric curve (H+(cons,surf): hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+(cons,surf)/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength.

Monolayer binary active phase (Mo-V) and (Cr-V) supported on titania catalysts for the selective catalytic reduction (SCR) of NO by NH3.

Monolayer catalysts containing binary active phases (VOx-CrOx, VOx-MoOx) were prepared by simultaneous deposition of the corresponding transition metal-oxo species on the TiO2 (anatase) surface using the equilibrium deposition filtration technique. The prepared samples contained various amounts of each transition metal but almost the same total metal loading. They were characterized by atomic absorption spectroscopy, N2 adsorption, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and tested for the selective catalytic reduction of NO by NH3 in the temperature range 250-450 degrees C.

Adsorption of cobalt ions on the "electrolytic solution/gamma-alumina" interface studied by diffuse reflectance spectroscopy (DRS).

Diffuse reflectance spectroscopy was used for the first time to investigate the adsorption of the [Co(H2O)6]2+ ions on the interface developed between the surface of the gamma-alumina particles and the electrolytic aqueous solutions used for the preparation of cobalt-supported gamma-alumina catalysts by equilibrium deposition filtration. The formation of inner-sphere Co(II) surface complexes in which Co(II) is in octahedral symmetry was confirmed. A deconvolution peak centered at approximately 585 nm was attributed to the exchange of one aqua ligand with one AlxOHy (x = 1, 2, or 3; y = 0 or 1) negatively charged surface group resulting in the formation of mononuclear monosubstituted inner-sphere Co(II) complexes at a Co(II) surface concentration equal to 0.

Adsorption of cobalt species on the interface, which is developed between aqueous solution and metal oxides used for the preparation of supported catalysts: a critical review.

In the present review article, we present the efforts done so far for elucidating the mechanism of adsorption of the Co(II) species, mainly Co(H(2)O)(6)(2+), on the interfacial region developed between metal oxide particles, used as catalytic supports, and aqueous electrolytic solutions. Specifically, we present: (i) the principal modes of deposition of the transition metal ionic species (TMIS) on the surface of oxidic supports related with the various methodologies used for the preparation of the supported catalysts; (ii) the state of the art concerning the general aspects of the adsorption mechanisms of the TMIS on the aforementioned interfacial region; and (iii) the works reported so far dealing with the adsorption of the Co(II) species on the surface of gamma-Al(2)O(3) (gamma-alumina), alpha-Al(2)O(3) (alpha-alumina), TiO(2) (rutile), and SiO(2) (silica). It was concluded that the mechanism of adsorption depends on two main factors: on the Co(II) surface concentration and on the nature of the support surface.

Potentiometric mass titrations: a quick scan for determining the point of zero charge.

A novel technique for determining the point of zero charge (pzc), called 'potentiometric mass titrations technique', has been developed and used for determining the pzc of several industrially used catalytic supports (SiO2, TiO2, gamma-Al2O3 and MgO).