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Oxygen defects, surface acidity and catalytic activity of Keggin-type phosphotungstic acid dispersed on SBA-15 mesoporous catalyst were investigated. When the catalyst was calcined at different temperature, oxygen defects resulted from removal of terminal oxygen from W=O bond or cleavage of corner sharing W–Oc–W bond in the Keggin structure via dehydration or/and suface dehydroxylation. The catalyst contained both Lewis (L) and Bronsted (B) acid sites and their amount varied with the calcination temperature which could be correlated well with the conversion of 4,6-dibenzothiophene (4,6-DMDBT) in a model diesel using H2O2 as oxidant. L acid sites served as active sites for 4,6-DMDBT adsorption via electron donation-acception pathway and B acid sites helped oxygen transferring from peroxotungstate complex to sulfur atom in the adsorbed 4,6-DMDBT, benefiting the sulfone formation.

Two series of FeOx/SBA-15 and FeOx/Zr-SBA-15 mesoporous catalysts were synthesized with ultrasound-assisted method by varying Fe content from 10 wt% to 20 and 30 wt%. The crystalline structure, textural properties, surface morphologies, surface acidity, and phase composition of the catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), in situ Fourier transform infrared spectroscopy (FTIR). The XRD, Raman and Mossbauer spectroscopic characterizations showed that both γ-Fe2O3 and α-Fe2O3 nanoparticles were present in all the catalysts and Fe3+ ions were dispersed on the surface of SBA-15 with different coordination. In the oxidation desulfurization (ODS) of a model diesel, the reaction parameters (temperature, time, and catalyst mass), Fe content, zirconium doping, and surface acidity of the catalysts were all critical for the ODS in a biphasic reaction system. All catalysts chiefly contained Lewis acidity which was related to iron content and zirconium modification and could correlate well with catalytic activity. Zirconium incooperating into the SBA-15 solid increased surface acidity and promoted γ-Fe2O3 formation by inhibiting the amorphous iron oxide in the Fe/Zr-SBA-15 catalysts, thus improved the ODS efficiency. The reaction temperature 60 °C was the optimal for ODS reaction, temperature greater than 80 °C led to oxidant partial decomposition. Under the optimal reaction condition, 0.1 g of the best catalysts (30%Fe/SBA-15 and 30%Fe/Zr-SBA-15) could remove all dibenzothiophene (DBT) (300 ppm DBT in 100 ml n-hexadecane) at 60 °C within 30 min. Thus, the combination of catalysis, oxidation and extraction in our polar-nonpolar-solid reaction system was simultaneously realized in one unit, which will be promising for effectively removal of organosulfur compounds for production of ultralow sulfur fuels.

The study of the deactivation of HY zeolites in the dehydration reaction of glycerol to acrolein has represented a challenge for the design of new catalysts. HY zeolites with SiO2/Al2O3 molar ratios between 3.5 and 80 were studied. The solids were characterized by XRD, N2 physisorption, SEM-EDXS, Raman and UV-vis spectroscopies, infrared spectroscopy of pyridine (FTIR-Py) and catalytic activity tests from 250 °C to 325 °C. It was found that the total amount of acid sites per unit area of catalyst decreased as the SiO2/Al2O3 molar ratio increased from 3.5 to 80, resulting in the decrease in the initial glycerol conversion. The initial acrolein selectivity was promoted with the increase of the Brønsted/Lewis acid sites ratio at any reaction temperature. The deactivation tests showed that the catalyst lifetime depended on the pore structure, improving with the presence of large surface areas as evidenced by the deactivation rate constants. The characterization of the deactivated catalysts by XRD, N2 physisorption and thermogravimetric analysis indicated that the deposition of coke resulted in the total obstruction of micropores and the partial blockage of mesopores. Moreover, the presence of large mesopores and surface areas allowed the amount of coke deposited at the catalyst surface to be reduced.

The adsorption capacities of two synthesized zeolites (crystalline ZSM-5 and semi-crystalline faujasite Y) for a mixture of indole, quinoline and carbazole were studied. The different samples obtained show different crystalline degree, mesoporosity and Si/Al ratios. The synthesis procedure is based on the simultaneous depolymerization of a mixture of high surface area silica, such as rice hull ashes (RHA), and a crystalline zeolite, such as clinoptilolite or faujasite. The depolymerization step is followed by a partial reorganization induced by a structure-directing agent. A model mixture of nitrogenous compounds was prepared, then it was mixed with the zeolite samples and the amount adsorbed of nitrogenous compounds was determined by gas chromatography. Analysis of the adsorbed molecules reveals selectivity in favor of quinoline, followed by indole and then carbazole. The best adsorbent properties correspond to the solid with highest porous volume. The samples obtained were characterized by X-ray diffraction, 29Si and 27Al magic-angle spinning nuclear magnetic resonance, X-ray fluorescence and Fourier transform infrared spectroscopy. The Barrett-Joyner-Halenda (BJH) pore size distribution and the Brunauer-Emmet-Teller (BET) surface area values were obtained from N2 adsorption/desorption isotherms.

High levels of sulfur organic compounds (SOCs) and nitrogen organic compounds (NOCs), which are contaminants present in diesel fuel and straight run gas oil (SRGO), were removed using tungsten/zirconia catalysts and hydrogen peroxide by oxidative desulfurization and oxidative denitrogenation reactions. Two tungsten sources were used: tungstic acid and ammonium metatungstate. The catalysts obtained by anionic exchange at low pH with tungstic acid showed remarkable homogeneity and high W dispersion attributed to tetrahedral W species and full dibenzothiophene (DBT) oxidation was achieved in 5 min of reaction. On the other hand, the catalysts obtained by impregnation with ammonium metatungstate developed mainly octahedral species with less DBT oxidation. It was also found that tetrahedral species generate more acidity than octahedral species. A density functional theory computational study confirmed the observed DBT oxidation trend shown by tetrahedral and octahedral W species on the peroxide-activated catalysts. Diesel fuel and SRGO were desulfurized and denitrogenated to a high extent: 97% in diesel fuel and 70% in SRGO for sulfur compounds and 96% in diesel fuel and 89% in SRGO for nitrogen compounds, whereas C1–C3 dibenzothiophenes, 4-methyl dibenzothiophene, and 4,6-dimethyl dibenzothiophene were fully removed. The elimination of SOCs and NOCs present in fuels can be effectively carried out in a single process to obtain clean fuels.

For the first time, highly selective Pt/H 3 PW 12 O 40 /SBA–15 trifunctional catalysts were evaluated for n-heptane hydroisomerization. Both Lewis (L) and Bronsted (B) acid sites were present in these catalysts. Reduction treatment led to heteropolyacid dispersion better and Pt nanoparticles smaller. With the best 1wt%Pt/20wt%H 3 PW 12 O 40 /SBA–15 catalyst, 100% isomerization selectivity and 56.74% n-heptane conversion were obtained at 320 °C. Among the products, the dibranched isomers concentration faction was > 50% and 2,2-dimethylpentane was predominant. Pt/H 3 PW 12 O 40 /SBA–15 catalysts with Pt nanocrystals, proper acidity strength and a balanced ratio of B/L acid sites, and highly ordered large mesopores were chiefly responsible for the high isomerization selectivity.

Alumina-supported Mo-based hydrodesulfurization catalysts (14 wt% nominal Mo loading) were modified by thioglycolic acid (TGA, TGA/Mo = 1 mol ratio), as a chelating agent containing a thiol group. To that end, two series of catalyst were prepared: the first one by using ammonium heptamolybdate as a precursor and, in the second one, in situ obtained phosphomolybdates from MoO 3 digestion in diluted H 3 PO 4 . Oxidic phases were characterized by N 2 physisorption, Raman and UV–vis spectroscopies, electron microscopy and XPS. As well, the corresponding sulfided phases were studied by XPS, HR-TEM-STEM techniques, and chemical composition was determined by STEM-EDX. Formation of ligand-to-metal charge transfer (LMCT) complexes between the S-bearing TGA and Mo atoms, resulted in reduced Mo 5+ species, as indicated by XPS, and was correlated to electronic transitions bands in the UV–visible spectra. On the other hand, the catalysts prepared from phosphomolybdates impregnation and TGA addition resulted in two-fold amount of Mo 4+ sulfided species, as indicated by XPS. TGA impregnation redissolve and disperse the MoO 3 resulting in materials particles in materials with increased stacking of MoS 2 slabs on which slabs length remained essentially unaltered. Highly active (as tested in liquid-phase dibenzothiophene hydrodesulfurization) Type II sites were favored mainly in sulfided TGA-modified formulations.

In the present work, supported liquid membranes based on three ionic liquids (ILs) (1-(2-aminoethyl)-3-methylimidazolium trifluoromethanesulfonate ([AEMIm]Tf), 1-(2-aminoethyl)-3-methylimidazolium tetrafluoroborate ([AEMIm]BF4) and trioctylmethylammonium anthranilate ([TOMA])), used as mobile phases, were studied in the separation of carbon dioxide from nitrogen. The IL chemical structures and thermal properties were confirmed by spectroscopic techniques and thermogravimetric analysis (TGA), respectively. The IL homogeneous distribution of the impregnation on alumina tubular supports was determined by scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX). Permeation tests were carried out using pure gases at 30 °C and 1 bar. The amino-functionalized ILs, two of them in the cation, [AEMIm]BF4 and [AEMIm]Tf, and the other one in the anion, [TOMA]An, reacted with CO2, leading to the formation of carbamates. [TOMA]An, which has the amine group at the anionic part, showed the best permselectivity, reaching a selectivity of 70.

In this work, the acid and photocatalytic properties of titanate nanotubes (NTs) were surveyed. The surface acidity of the NTs was characterized by FTIR with lutidine and pyridine. The photocatalytic degradation of phenol in aqueous suspension was performed to test the photocatalytic properties of the NTs. The results were compared with those obtained from commercial TiO 2 . NTs were prepared by hydrothermal treatment of TiO 2 nanoparticles in a NaOH aqueous solution. During the washing step, three different acid agents (HCl, H 2 SO 4 , and HNO 3 ) were used. TiO 2 nanoparticles were synthesized previously by the sol-gel method. The photocatalytic materials were characterized by FTIR, XRD, XPS, S BET , UV–vis, and HRTEM. It was found that the used acid agent significantly affected the amount and type of acid sites. Bronsted acid sites were favored by the use of HNO 3 . Lewis acid sites were promoted when HCl was employed during the washing step, which is in contrast with the results obtained using the other acids chosen in this work. Besides, the use of HCl promoted the H 2 Ti 3 O 7 phase. The acid phase H 2 Ti 4 O 9 ·H 2 O was favored when HNO 3 was used and H 2 SO 4 formed the H 2 Ti 2 O 4 ·(OH) 2 acid phase. The presence of Cl, S, and N species on the NTs was not found. Furthermore, Na + ions were completely removed from the surface of the NTs, which were exchanged by H + ions. It was found, in general, that the three catalysts presented a relatively high photocatalytic activity to remove phenol. However, NTs washed with HNO 3 (NT-HNO 3 ) displayed the best photocatalytic activity compared to the other NTs. After 200 min, NT-HNO 3 reached a phenol degradation yield close to 100%. Commercial TiO 2 presented a phenol degradation yield close to 60%. It could be concluded that the acid phase (H 2 Ti 4 O 9 ·H 2 O) and concentration of Bronsted acid sites promoted the photocatalytic activity of NT-HNO 3 .

The aim of this work is to estimate some nitrogen (N)-adsorption properties and the N-adsorption capacity (q) required for commercial application in the ultra-low sulfur diesel production. Hydroxyl (OH) groups and interactions among the commercial adsorbent Selexsorb® CDX (CDX) and pyridine and indole were studied by means of Fourier transform infrared spectroscopy. The adsorption of N-compounds from three diesel fuels over CDX was estimated at CDX/fuel ratio: 0.01–0.09 g/g, Contact time: 1–60 m, 303 K, and 0.078 MPa in a batch setup. It was concluded that an appropriate N-adsorbent should have high densities of suface OH groups and Lewis and Bronsted strong-acid sites and a q ≥ 0.70 mmol/g.

V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %). Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined by the Mg/Al ratio. Vanadium interlayer doping modifies the oxidation state of vanadium and consequently catalytic properties. Surface properties were studied by X-ray photoelectron spectroscopic and diffuse reflectance, UV-visible spectroscopy, and temperature programmed reduction (TPR). The analyses provided information about the oxidation state, before and after the reaction. From these results, it is suggested that selectivity to propylene and catalytic activity depend mainly on vanadium oxidation state.

This work reports the results of the ultrasound-assisted hydrothermal synthesis of two sets of V2O5 dispersed on SBA-15 and Zr doped SBA-15 catalysts used for the oxidation of dibenzothiophene (DBT) in a model diesel via the combination of oxidation, catalysis, and extraction technical route. These catalysts contained Lewis acidity as major and Brønsted acidity as minor. The amount of acidity varied with the content of vanadia and zirconium doping. It was found that DBT conversion is very sensitive to the Lewis acidity. DBT conversion increased by increasing the vanadium content and correlated well with the amount of surface Lewis acidity. Under the optimal experimental condition (Reaction temperature: 60 °C, reaction time 40 min, catalyst concentration: 1 g/L oil, H2O2/DBT mole ratio = 10), the 30% V2O5/SBA-15 and 30% V2O5/Zr-SBA-15 catalysts could convert more than 99% of DBT. Two reaction pathways of DBT oxidation involving vanadia surface structure, Lewis acidity, and peroxometallic complexes were proposed. When the vanadia loading V2O5 ≤ 10 wt%, the oxidative desulfurization (ODS) went through the Pathway I, in the catalysts with moderate vanadia content (V2O5 = 20–30 wt%), ODS proceeded via the Pathways II or/and the Pathway I.

A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H 2 O 2 as oxidant. ODS activity was found to be proportional to the V 5+ /(V 4+ + V 5+ ) values of the catalysts, indicating that the surface vanadium pentoxide (V 2 O 5 ) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e. , 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Bronsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V 2 O 5 ) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V 2 O 5 /Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

TiO2 nanotubes, nanofibers and nanowires were prepared by the hydrothermal treatment of TiO2 nanoparticles with different NaOH concentrations (5, 10 and 12 N) at 120, 140 and 180 °C; afterwards, HCl was added until reaching pH 2. Both the crystalline phase and coordination of the TiO2 nanotubes, nanofibers and nanowires were composed principally of H2Ti3O7, H2Ti4O9·H2O and H2Ti5O11·H2O. Likewise, the surface area, pore volume and pore size of the TiO2 nanotubes, nanofibers and nanowires changed with the NaOH rinsing treatment. The photocatalytic activities for methylene blue and methyl orange degradation were strongly enhanced by the nanotubes and nanoparticles in the basic and acid media, respectively, showing a relationship between their structure and the medium.

Pt on alumina catalysts were studied when the texture of the alumina change by addition of a cationic surfactant cetyl-trimethyl ammonium bromide (CTAB). The mesoporous alumina was prepared using CTAB from 0.01 to 0.1 M. The surface area and pore volume increased as CTAB concentration increased passing through a maximum. After calcination at 300 °C, and 550 °C boehmite and γ-Al2O3 were found by XRD. After calcination at 800 °C, the transition between γ- and θ-Al2O3 was observed together with an increase of pore volume and pore diameter respect to the alumina without surfactant. The alumina prepared with the lowest concentration of CTAB showed the highest thermal stability. Bronsted and Lewis acidities were found on alumina samples having CTAB concentrations from 0 to 0.075 M. The sample of alumina with the highest CTAB concentration showed the highest population of pentahedral aluminum (AlV), Lewis acidity and a dense network of wormlike particles by SEM. After H2 reduction of these catalysts, sulfur that came from the alumina support weakened the function of Pt particles to hydrogenolysis reaction whereas the CTAB introduced Bronsted acid sites in the alumina increasing the isomerization reaction.

Glycerol dehydration to acrolein was studied with three catalysts using zeolite-Y. This zeolite in its protonic form (HY), with La (LaY) and Pd with La (Pd/LaY), was characterized by X-ray diffraction (XRD), Fourier-transform-infrared spectroscopy (FTIR) with pyridine, BET, Scanning Electron Microscope (SEM)–Energy-Dispersive Spectroscopy X-ray (EDS) and the catalytic activity tests were carried out under H2 atmosphere. It was found that La ions exchanged in the zeolite-Y resulted in the improvement of both glycerol conversion and yield to acrolein, also a relatively constant glycerol conversion was achieved up to three hours, due to the presence of Pd on the catalyst and H2 in the feed. The comparison of the calculated and experimental yields obtained from the catalytic tests of the Pd/LaY catalyst indicates a greater activity for the reaction to acrolein than for the reaction to acetol. The calculated equilibrium yields of the dehydration reaction from glycerol to acrolein, acetol, ethanal, methanol, and water and the experimental yields of a Pd/LaY catalyst were compared. Thermodynamically, a complete conversion of glycerol can be achieved since the general system remains exothermic and promotes the path to acetol below 480 K. Above this temperature the system consumes energy and favors the production of acrolein, reaching its maximum concentration at 600 K.

In this work, the sol–gel and hydrothermal methods were used to synthesize TiO{sub 2}-nanostructured supports. The palladium supported on sol–gel TiO{sub 2} and on hydrothermal-method-TiO{sub 2} nanotubes was obtained by incorporating it through photodeposition. The characterization was performed by X-ray diffraction, transmission electron microscopy, N{sub 2} physisorption, pulse chemisorption, ultraviolet–visible absorption spectroscopy and X-ray photoelectron spectroscopy. Both sol–gel-palladium–TiO{sub 2} and palladium-nanotube samples showed different palladium dispersion and physicochemical properties. In the palladium-nanotube sample, high surface area (243 m{sup 2}/g), H{sub 2}Ti{sub 3}O{sub 7} stable phase, and low band gap energy (2.35 eV) were obtained. Palladium-nanotubes and palladium-TiO{sub 2}, used as reference samples, were prepared by wet impregnation. - Highlights: • The precursors of TiO{sub 2} nanotubes were synthesized by the sol–gel method. • TiO{sub 2} nanostructures showed improved textural and morphological properties. • Pd nanoparticles around 1 nm were obtained by the photodeposition method. • TiO{sub 2}-nanotube-based catalysts can be a powerful tool for facing air pollution.

In the hydroprocessing of coker naphtha (hydrodesulfuration and hydrodenitrogenation), silica poisoning of hydrotreating catalysts represents a severe problem due to the deposition of Si species, which deactivate the catalyst and shorten its life time. The deactivation results of the sulfided NiMo/γ-Al 2 O 3 hydrotreating catalyst, obtained by running a long-term test, are presented. Refinery coker naphtha was processed in a continuous hydroprocessing unit in a mini-scale laboratory under industrial conditions. Catalyst samples from 15 to 90 days on stream were characterized. Si determination and the evolution of the structural characteristics of these samples were followed by 29 Si MAS NMR, FTIR, textural analysis and scanning electron microscopy (SEM) performing microanalysis by dispersion energies (EDS). 29 Si MAS NMR results confirmed the deposition and evolution of different Si species on the catalyst surface with the time on stream. The increasing content of Si species in the catalyst affected textural properties such as surface area and pore volume by decreasing them; as for the chemical properties, the Bronsted/Lewis (B/L) ratio was modified without increasing the coke formation and cracking activity. From the coker naphtha hydrotreating processes, only the hydrodenitrogenation activity was affected. The Si deposition profile shows that the concentrations were higher in the external than in the internal surface of the pellets. The shape of these profiles indicates that the deposition process becomes diffusion rate limited.

A series of MoO3-MoS2 catalysts supported on TiO2 or ZrO2 were synthesized and studied. The aim of this work is to understand the main aspects that influence the catalytic performance of Mo-based catalysts in bioenergy applications. We used two sulfidation temperatures for changing the Mo species in both supports. The catalysts were characterized by N2 physisorption, XRD, SEM, H2-TPR, Raman spectroscopy and XPS. We found important changes in the chemical species of Mo, S and O atoms present in the catalytic materials at 200 or 400 °C of sulfidation temperature. The materials were tested in the hydrodeoxygenation (HDO) of palmitic acid as a model compound of fatty acids. We found some structure-activity relationships of these materials. For instance, the promotion of mixtures of Mo6+, Mo5+ and Mo4+ species increased the catalytic activity for all the materials. MoO3/TiO2 catalyst exhibits higher activity than its counterpart supported on ZrO2. However, the sulfidation of these materials resulted in highly active catalysts, specially using ZrO2. Oxygen vacancies are formed for the catalysts supported on ZrO2 upon sulfidation. Molecular models were employed for a better understanding of the interaction between palmitic acid and the catalytic surfaces. We found that a combination of Mon+ species with S-containing compounds and oxygen vacancies in the catalytic materials is key to develop new highly active catalytic materials for HDO of fatty acids.

γ-Alumina-based HDT catalysts used as silicon traps adsorb more efficiently silicon compounds from naphtha till saturation, which occurs at a relatively low concentration (5–10 wt%). As the silicon content in the catalyst increases, the surface is progressively deactivated, mainly affecting the hydrodenitrogenation and hydrogenation activity. According to the aforementioned, the deactivation of HDT catalysts was investigated by means of a fraction of naphtha doped with silicone oil with different concentrations, which was used to contaminate the catalysts. The presence of silicon species was detected by 29Si NMR and FTIR spectroscopies. The Si O Al formation was evidenced by the B/L ratio measured for the doped HDT catalysts. The results obtained for the deactivation of HDT catalysts exposed to high silicon contents show that this factor plays a major role in the loss of activity.

In the present work, two supported liquid membranes, which used two new ionic liquids (ILs) as mobile phase, 1-(2-aminoethyl)-3-methylimidazolium trifluoromethanesulfonate ([AEMIm]Tf) and trioctylmethylammonium anthranilate ([TOMA])An, were studied characterizing their chemical structures by NMR and FTIR. Both the impregnation level and mass of the ILs in alumina tubular supports were determined by SEM-EDX mapping and gravimetric analysis. The permeation tests were carried out using pure gases at 25 °C and 1 bar. It was confirmed that in the ILs, [AEMIm]Tf and [TOMA]An, the amine groups reacted with CO2, leading to the formation of carbamates. The IL [TOMA]An, which has the amine group at the anionic part, showed the best ideal permselectivity, reaching a selectivity of 92.

The surface properties of Pd and Pd–Pt catalysts supported on binary ZrO 2 –WO x and ternary ZrO 2 –Al 2 O 3 –WO x oxides prepared by the sol–gel method were studied. Special attention was paid to the study of the texture of the catalysts as well as the chemical state of tungstated zirconia and tungstated zirconia promoted with alumina in the palladium catalysts. The catalysts were tested in the isomerization of n -hexane and were characterized by N 2 physisorption, XRD, TPR, Raman spectroscopy, XPS and FT-IR of adsorbed pyridine. The catalysts had bimodal pore size distributions with mesopores in the range 55–70 A and macropores of 1000 A in diameter. The catalysts had a surface WO x coverage (4.4–6.0 W nm −2 ) lower than that of the theoretical monolayer (7.0 W nm −2 ). A lower acidity of the ternary ZrO 2 –Al 2 O 3 –WO x oxide as compared to the binary ZrO 2 –WO x oxide was found. Higher activity in the isomerisation of n -hexane was obtained in the Pd–Pt catalysts supported on ternary ZrAlW oxides prepared by sol–gel that is correlated with the coexistence on the surface of W 4+ (WO 2 ) or W 0 and W 6+ (Al 2 (WO 4 ) 3 ) species, ZrO 2 in the tetragonal phase and a high amount of ZrO x suboxides species in a low oxidation state (Zr 3+ and Zr 2+ ).

Pt supported on tungstated zirconia catalysts (Pt/WZ) doped with different Fe contents were evaluated in the n-hexane hydroisomerization reaction. High-throughput experimentation (HTE) approaches were used to investigate the effect of the iron incorporation over the catalytic activity. It was found that the presence of iron at low concentrations (0.5–1 wt%) increases the conversion and the yield to the high octane 2,2-dimethyl-butane (2,2-DMB) isomer. The characterization results suggest that the presence of iron modifies the nanostructure of the WOx species on the zirconia surface which in turn produces the generation of active Bronsted acid sites thus optimizing the tungsten content toward the highest catalytic activity. It was also found that the surfactant incorporation further improves the performance of Pt/WZ catalysts, although, the activity was improved with the Fe addition at lower concentration.

Methane catalytic decomposition (MCD) over Ni/MCM-41 catalysts was tested in a microreactor to simultaneously produce hydrogen and carbon nanotubes (CNTs). The methane conversion reached 30% to 47% at a moderate temperature range from 400°C to 600°C and the catalytic activity of the catalysts remains stable during 500 min steam on time. CNTs were chiefly formed through tip-growth mode, due to the weak interaction between the metallic Ni and the support. Most of the Ni particles are located on the tip of the produced CNTs, which avoids rapid deactivation of the catalyst resulted from carbon encapsulation. Large Ni particles usually lead to the formation of CNTs with big diameter. During the reaction, the shape of Ni particles changed from pseudo-sphere to diamond-like. All the CNTs consist of multiple layer walls and are curved in certain degree.

A zirconium modified MCM-48 mesoporous material was synthesized by surfactant-templated method. Surface grafting Zr-MCM-48 with tungstophosphoric acid led to a great enhancement of both the number of the Br?nsted acid sites and acidity strength in comparison with the bare support. At 100°C, the 30 wt% H3PW12O40/Zr-MCM-48 contained 174 μmol/g Br?nsted acid sites which were 14.5 times greater than that of Zr-MCM-48. The Keggin structure of the grafted heteropolyacid was rather stable after calcination at 400°C for 2 h, approximately 93.3% of Keggin structure in the dispersed heteropolyacid were remained without destruction but slightly distorted in some degree, as evidenced by FTIR characterization and 31P NMR-MAS analysis. This H3PW12O40/Zr-MCM-48 solid with three dimensional mesoporous system, large surface area and very strong Br?nsted acidity will be a promising catalyst for acid catalytic reactions.

A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered.

The Rh and Rh–Sn supported catalyst on γ-Al2O3 and γ-Al2O3–CeO2 (loading 1, 5 and 20 Ce wt%) were characterized by means of electron microscopy (TEM), temperature programmed reduction (TPR), Fourier transformed infrared of CO adsorption (FTIR-CO) and X-ray photoelectron spectroscopy (XPS). The catalysts were tested in the catalytic wet air oxidation of an aqueous solution of 227 ppm of TAME and 1 g/L of catalyst (120 °C and 10 bar of oxygen partial pressure). The rhodium monometallic catalysts showed an increase in the activity with the load of cerium oxide in the catalyst. The coexistence of Rh°/Rhδ+ and Ce4+/Ce3+ redox couples facilitates the activation of TAME and hence the catalytic activity and selectivity to mineralization. The addition of Snδ+ enhances the activity and selectivity; this is explained by assuming that Snδ+ acts as Lewis acid sites trapping the TAME molecules for further oxidation on rhodium metal particles.

Photodynamic therapy (PDT) has emerged as an alternative and promising noninvasive treatment for cancer. It is a two-step procedure that uses a combination of molecular oxygen, visible light, and photosensitizer (PS) agents; phthalocyanine (Pc) was supported over titanium oxide but has not yet been used for cell inactivation. Zinc phthalocyanine (ZnPc) molecules were incorporated into the porous network of titanium dioxide (TiO2) using the sol-gel method. It was prepared from stock solutions of ZnPc and TiO2. ZnPc-TiO2 was tested with four cancer cell lines. The characterization of supported ZnPc showed that phthalocyanine is linked by the N-pyrrole to the support and is stable up to 250°C, leading to testing for PDT. The preferential localization in target organelles such as mitochondria or lysosomes could determine the cell death mechanism after PDT. The results suggest that nanoparticulated TiO2 sensitized with ZnPc is an excellent candidate as sensitizer in PDT against cancer and infectious diseases. From the Clinical Editor: Photodynamic therapy is a two-step procedure that uses a combination of molecular oxygen, visible light and photosensitizer agents as an alternative and promising non-invasive treatment for cancer. The results of this study suggest that nanoparticulated TiO2 sensitized with ZnPc is an excellent photosensitizer candidate against cancer and infectious diseases.

Anatase with nanotubular (NT) and nanofibrilar (NF) morphology was obtained by annealing treatment at 773 and 873 K of a hydrous titanate with nanotubular morphology synthesized by alkali hydrothermal method. The surface properties were compared with those of a commercial anatase made up of nanoparticles (NPs); materials with similar specific surface area were selected for this end. Low temperature CO adsorption FTIR showed only one adsorption site on the OH groups of nanotubes and nanofibers and almost no Lewis sites were detected suggesting the absence of coordinatively unsaturated Ti4+ sites in NT and NF samples. All the OH groups on anatase nanotubes are exposed on the surface, and they are not of Bronsted type. The OH groups in NT and NF adsorb 2.2 times pyridine or lutidine molecules than nanoparticles via H-bonding interaction. These weak interactions are very attractive in the elimination of N-compounds from oil fractions using regenerable adsorbents.

Catalytic wet-air oxidation of p-cresol was carried out on Ag/Al 2 O 3 ―ZrO 2 catalysts at 1, 5, 10, and 20wt%of ZrO 2 in a reactor-type batch and 160 °C and 15 bar of oxygen. Al 2 O 3 ―ZrO 2 supports were prepared by the simultaneous hydrolysis of the boehmite and zirconium alkoxide. Ag/Al 2 O 3 ―ZrO 2 catalysts prepared by deposition-precipitation showed higher surface area (202―216 m 2 /g) and lower Lewis acids sites than the Ag/Al 2 O 3 (161 m 2 /g) and Ag/ZrO 2 (25 m 2 /g) reference catalysts. FTIR-CO adsorption showed a shift to lower frequencies on Ag/Al 2 O 3 ―ZrO 2 catalyst indicating electron-rich metallic particles. The p-cresol conversion, TOC abatement, and CO 2 selectivity were improved when Ag was supported on Al 2 O 3 ―ZrO 2 mixed oxides. A modification of the surface properties of Ag on the Ag/ Al 2 O 3 ―ZrO 2 catalysts due to a metal-support interaction leading to a faster oxidation of the adsorbed reactant species is proposed.

The effect of the Bronsted/Lewis acid ratio on isomerization of n-heptane using Al 2 O 3 as a source of Lewis acidity and WOx/ZrO 2 as a source of Bronsted and Lewis acidity was studied and controlled using mechanical mixtures of these solids. These mixtures were characterized by surface area, infrared spectroscopy of pyridine, X-ray diffraction and Raman spectroscopy. It was found that the presence of W O stretching mode which was consistent with the presence of oxotungstate species which were the precursors of the acid sites. It was found out that as the oxotungstate structures increased, the selectivity to n-heptane isomers increased while the hydrocracking and dehydrocyclization selectivity decreased. The presence of Bronsted acidity of the WOx/ZrO 2 domains, the increase of Knudsen diffusivity and the loss of Pt metallic area by strong interaction of the Pt with the WOx/ZrO 2 explain this catalytic behavior.

The liquid phase alkylation of benzene with dec-1-ene was catalyzed by 12-tungstophosphoric acid (WP) supported on different solids (ZrO2, SiO2, activated carbon and boehmite-Al2O3). Catalysts prepared with 20 wt.% of WP were thermally treated at 300 °C and then the acidity was estimated by FT-IR pyridine adsorption spectroscopy. Additionally, the catalysts were characterized by X-ray diffraction, thermal gravimetric analysis, and N2 adsorption measurements. Thermal stability of supported WP and changes in textural properties of the catalysts were analyzed. Of all the catalysts, 20WP on SiO2 showed the highest acidity and was found to be the most active catalyst in alkylation of benzene with dec-1-ene at 80 °C, at dec-1-ene conversion of 70% and alkyl benzenes selectivity of nearly 40%.

The study presented here compares the performance of different zeolite catalysts (Beta, ZSM-5 and Beta:ZSM-5 composites) for benzene alkylation by propylene with a benzene enriched reformate heart-cut (13 wt% benzene). The experiments were carried out in a batch system with a 1/1 benzene:propylene mole ratio at 220 °C for 1 h. The results showed that an increase in conversion produced decreases in cumene selectivity and oligomers formation. These results were associated to Beta contained catalysts. Lower conversions related to a higher oligomers production and lower di-isorpropylbenzene isomers formation, were obtained with a ZSM-5 catalyst. Results were compared with pure benzene/propylene alkylation tests carried out at similar experimental conditions.

Mesostructured Al-MCM-41 materials (referred as CSA n , where n = Si/Al molar ratio = 50, 30 and 10, respectively) and 12-tungstophosphoric acid promoted Pt/Al-MCM-41 catalysts were investigated by a variety of spectroscopic techniques. Aluminum ions were distributed within the resultant solid having 4, 5 or 6-coordination, in different proportion, which correlate with the formation of Bronsted acidity. Grafting the H 3 PW 12 O 40 heteropolyacid (referred as HPW) on the Al-MCM-41 solids not only noticeably enhanced, by 2–3 times, the number of Bronsted acid sites, but also greatly improved the acidity strength, with respect to that of the bare host. The primary structure of the Keggin units of the supported heteropolyacid was largely preserved after calcination at 350 °C; however, small parts of the Keggin units were strongly distorted or deformed due to the strong interaction between the heteropolyanions and the hydroxyl groups of the support. Catalytic evaluation confirmed that 1 wt.%Pt/25 wt.%HPW/Al-MCM-41 (denoted as Pt/HPW/CSA n ) catalysts were very active for n-heptane isomerization in the presence of hydrogen under an atmospheric pressure condition. High yield of multibranched isoheptanes was produced, which was dependent on the pore diameter and the Bronsted acidity of the catalysts. The molar ratio of multibranched to monobranched isoheptanes is much higher than that reported in the literature under similar reaction conditions using zeolite-containing catalysts, showing the potential of producing high octane number fuel through the approach of n-heptane hydroisomerization by using our novel mesostructured catalysts.

Conventional and high-throughput experimentation (HTE) techniques were used for the synthesis, characterization, and catalytic testing of Pt/Mn–WO x –ZrO 2 materials. The catalysts were prepared by surfactant-assisted coprecipitation and screened for catalytic activity in a multi-channel fixed bed (MCFB) micro-reactor for the hydroisomerization of n -hexane. Conventional coprecipitation route leads mainly to the segregation of the WO 3 crystalline phase (XRD). On the other hand, the use of the automated HTE route allows the formation of catalysts with a highly dispersed WO x phase on the zirconia surface and a high surface area (60–100 m 2 /g) when calcined at 800 °C (N 2 physisorption, XRD, Raman, UV–vis, HRTEM). These polytungstates with different coordination symmetry are accessible to the reactants and they lead to an increase in the catalytic activity and selectivity to the bi-ramified products (2,2-DMB and 2,3-DMB) in the n -hexane isomerization. In addition, it was found that the incorporation of Mn modifies the nanostructural properties of the tungstated zirconia favoring the catalytic activity of these materials.

The influence of the Si/Zr molar ratio on the crystalline structure, textural properties, morphological features and surface acidity of Zr–MCM-41 mesoporous molecular sieves was investigated by X-ray diffraction (XRD), N 2 adsorption–desorption isotherms, 29 Si MAS NMR, TEM and FTIR spectroscopy of pyridine adsorption techniques. It is found that the structural ordering of Zr–MCM-41 materials varies with the Si/Zr ratio, highly ordered mesoporous molecular sieves could be obtained for a Si/Zr ratio larger than 4. Calcination may significantly improve the structural regularity. After impregnation with 25 wt% of H 3 PW 12 O 40 (denoted as HWP hereafter), the surface Bronsted acidity of the Pt/Zr–MCM-41 samples was greatly enhanced by 4–8 times. In the hydroisomerization reaction of n -heptane, the n -heptane conversion over all the Pt/HPW/Zr–MCM-41 catalysts linearly increases with increasing the reaction temperature, while, the selectivity to isoheptanes gradually decreases. The molar ratio of multibranched to monobranched isoheptanes ( R ) in the isomerization products varies within a very narrow range, between 0.8 and 1.2, which is several times greater than those reported in the literature at similar reaction conditions using zeolite-supported catalysts. The high R value obtained in this work is assumed to be related to the mesoporous geometry of the novel catalysts. In the products distribution, 2-methylhexane is predominant in the monobranched isoheptanes and 2,3-dimethylpentane is the prevailing compound being more than 50% of the multibranched isoheptane products. In the cracking products, butane (isobutane and n -butane) and propane are exclusively formed.

The catalytic oxidation of benzene on Pd (0.5 wt%)/γ-Al 2 O 3 –Ce catalysts with 1, 5 and 10 wt% Ce was investigated. The alumina–Ce supports were prepared by adding a Ce-nitrate precursor to an aluminum boehmite. The presence of Lewis acid sites was determined by FTIR-pyridine adsorption spectroscopy. By FTIR-CO adsorption, it was found that the presence of Ce leads to the stabilization of PdO on the supports. The presence of the PdO species on the Pd/γ-Al 2 O 3 –Ce catalysts was confirmed by X-ray photoelectron spectroscopy (XPS). The combustion of benzene (2600 ppm) in air was carried out at atmospheric pressure. Two behaviors were observed: for the catalysts with low Ce content (1%) and without Ce, the combustion occurs in a broad temperature range 100–280 °C, meanwhile, catalysts with high Ce contents (5, 10%), the benzene combustion occurs in the range 220–280 °C. An activation treatment on Pd/γ-Al 2 O 3 –Ce catalysts with a reactant mixture at 250 °C for 20 h reduces the temperature of the total combustion to 250 °C. A better stability on Pd/γ-Al 2 O 3 –Ce catalysts containing 5 and 10% Ce was observed. These results suggest that the oxidative catalytic properties of cerium oxide are shown at temperatures higher than 220 °C, and that an activation treatment is needed to obtain an optimal Pd°/PdO ratio for these species. The stability showed by the catalysts is explained by the effect of the CeO 2 , which inhibits the deposition of carbonaceous species on the Pd surface.

A series of Zr-modified MCM-41 mesoporous materials with a variety of Si/Zr molar ratios were synthesized by the surfactant-templated method. Textural properties, crystalline structure and surface acidity were characterized by X-ray diffraction (XRD), low-temperature N2 physisorption isotherms, solid-state nuclear magnetic resonance (MAS-NMR), UV–visible spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy of pyridine adsorption techniques. Both the as-made and the calcined materials show the typical MCM-41 structure with hexagonal mesochannels. The structural regularity varies with zirconium content in the materials. A proper amount of zirconium ions incorporated into the Si framework may noticeably improve the structural order, but high zirconium content leads to the reduction of the structural regularity. The mean pore diameter of the materials increases from 2.8 to 3.0, 3.8 and 4.5 nm as the Si/Zr molar ratio decreases from 25 to 15, 8 and 4, respectively. Meanwhile, the surface area and pore volume diminish with the increase of zirconium content. As H3PW12O40 (referred as HPW) is dispersed on the Zr-MCM-41 materials, the Bronsted acidity is greatly enhanced: from four to eight times. Three forms of heteropolyanions: (i) bulk-like HPW particles, (ii) highly dispersed HPW clusters with deformed Keggin structure and (iii) HPW species with partially fragmented Keggin structure, are adopted by the HPW deposited on the Zr-MCM-41 solids, due to the different interactions between the heteropolyacid species and the support. The 1 wt.%Pt/25 wt.%HPW/Zr-MCM-41 catalysts show high activity for the n-hexane hydroisomerization reaction, with 100% selectivity to isohexanes at temperatures below 260 °C. Increasing the zirconium content generally leads to a higher n-hexane conversion but it lowers the selectivity to hexane isomers that might be related to the different pore diameter distribution and surface density of the Bronsted acid sites.

γ-Al 2 O 3 –Ce catalysts were obtained by the impregnation of boehmite with cerium nitrate at different Ce contents (1, 5, 10, 20 wt%) and tested in the catalytic combustion of toluene. The catalysts annealed at 650 °C showed a diminution of the BET specific surface areas as a function of the cerium content. At low cerium content, the XRD spectra showed the γ-Al 2 O 3 phase, whereas at high cerium content, the γ-Al 2 O 3 phase and cerium oxide were observed. A diminution of the Lewis acidity was shown by the FTIR-pyridine absorption spectra. Both Ce 3+ and Ce 4+ in variable proportions were observed by XPS. It has been found that the activity for the toluene combustion can be related to the C 4+ /Ce 3+ ratio obtained in the various catalysts. The higher the C 4+ /Ce 3+ ratio is the higher the toluene combustion activity.

For the first time, modifications of the surface and framework of Si-MCM-41 by depositing a heteropolyacid on the surface and by introducing foreign Zr 4+ ions into the framework are investigated. The Zr-modified Si-MCM-41 mesoporous materials (hereafter referred as WSZ n , n =Si/Zr=25, 15, 8, 4) were synthesized through a surfactant-templated preparation approach, using low-cost fumed silica as the Si precursor. After impregnation with 25 wt% of H 3 PW 12 O 40 , the surface Bronsted acidity of the Pt/H 3 PW 12 O 40 /WSZ n catalysts was greatly enhanced by 2–10 times relative to the bare WSZ n support. Two kinds of supported heteropolyacids were formed: (i) bulk-like heteropolyacid crystals with unchanged Keggin structures, and (ii) highly dispersed heteropolyacid with distorted Keggin units. The formation of various kinds of heteropolyacid structures is closely related to the interaction between the heteropolyanions and the hydroxyl groups in the host support.

A WO 3 -ZrO 2 catalyst, prepared by a precipitation method, was annealed at 560, 700 and 800 °C with a view to examine the nature of WO x species using infrared and Raman spectroscopy, X-ray photoelectron spectroscopies (XPS), high resolution and energy filtered transmission electron microscopy (HRTEM and EFTEM). When calcining at 560 °C, a large amount of W atoms remain in W 5+ oxidation state, in strong interaction with the ZrO 2 , forming Zr O W bonds. Only a little fraction of the W atoms was expelled to the surface as isolated WO x species, which are responsible for the Bronsted acid sites. After calcining at 700 °C, all W atoms migrated to the surface, remaining in full W 6+ oxidation state, forming ca. 0.5 nm nanoclusters. In these nanoclusters, all W atoms are exposed on the surface and promote acid sites, mainly Bronsted acidity. When the sample was calcined at 800 °C, the tungsten nanoclusters grew to partially reduced ca. 3.0 nm WO x domains. These WO x domains showed very low acid sites density and strength, however, they showed the highest catalytic activity in n -hexane isomerization reaction; supporting the hypothesis that redox properties of WO x domains are responsible for this reaction.

The importance of aluminum alkoxides precursors (ethoxide, isopropoxide and sec-butoxide) in the tailoring of the structural and textural properties of γ-alumina was reported. It has been found that the specific surface areas (336–426 m2/g), as well as the mean pore size distribution are modified in function of the length and branching of the aluminium alkoxide used in the synthesis. A narrow pore size distribution was obtained with aluminum ethoxide (14.7 nm), meanwhile a broad pore size distribution was observed in samples prepared with aluminium sec-butoxide or aluminium isopropoxide precursors (18.2 and 19.4 nm). In fresh samples, Boehmite phase and AlVI octahedraly coordinated were identified by XRD and 27Al MAS-NMR spectroscopies. After annealing at 500°C, the samples showed the γ-alumina phase formation and a mixture of aluminium in tetrahedral AlIV and octahedral AlVI coordination in variable proportions. The acidity of the calcined samples, determined from the pyridine-FTIR spectra, showed Lewis and Bronsted type acidity. Activity in the 2-propanol dehydration reaction showed that the highest activity corresponds to the samples showing the highest Lewis acidity.

Two surfactant-templated synthetic routes are developed for the preparation of new types of mesoporous molecular sieves, Zr-MCM-41 and Zr-MCM-48, using different Si sources but keeping the same zirconium precursor (zirconium- n -propoxide). When fumed silica was used as Si precursor, a Zr-MCM-48 material of cubic structure was formed with a surface area of 654.8 m 2 /g and an unimodal pore diameter distribution. It shows low stability: after calcination at 600 °C, the ordered structure was transformed into a relatively disordered worm-like mesostructure with many defects and silanol groups. The use of tetraethyl orthosilicate as Si source led to the formation of a Zr-MCM-41 mesoporous solid, which had good thermal stability and a highly ordered hexagonal arrangement, with a surface area 677.9 m 2 /g and an uniform pore diameter distribution. Fourier transform infrared (FT-IR) characterization and 29 Si NMR analysis confirm that zirconium ions indeed incorporated into the framework of the solid. The in situ FT-IR spectroscopy of pyridine adsorption reveals that both, Lewis and Bronsted acid sites, were formed on the surface of these mesoporous materials. The strength and number of the Bronsted acid sites of the Zr-MCM-48 solid were greater than those of the Zr-MCM-41, due to a lower degree of condensation reaction during the synthesis that led to more structural defects in the framework and more silanol groups stretching from the solid surface.

This work reports the synthesis and surface characterization of a Zr-modified mesoporous MCM-41 solid with an ordered hexagonal arrangement, prepared through a templated synthesis route, using cetyltrimethylammonium chloride as the template. The surface features, crystalline structure, textural properties and surface acidity of the materials were characterized by in situ Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), N2 physisorption isotherms, 29Si MAS-NMR and in situ FT-IR of pyridine adsorption. It is evident that the surfactant cations inserted into the network of the solids during the preparation could be removed by calcination of the sample above 500 °C. The resultant material showed a large surface area of 680.6 m2 g−1 with a uniform pore diameter distribution in a very narrow range centered at approximately 2.5 nm. Zirconium incorporation into the Si-MCM-41 framework, confirmed by 29Si MAS-NMR analysis, increased not only the wall thickness of the mesopores but also the long-range order of the periodically hexagonal structure. Both, Lewis and Bronsted acid sites, were formed on the surface of the Zr-modified MCM-41 solid. Compared to Si-MCM-41 on which only very weak Lewis acid sites were formed, the densities of both Lewis and Bronsted acid sites and the strength of the acidity on the Zr-modified sample were significantly increased, indicating that the incorporation of zirconium greatly enhances the acidity of the material.

The evaluation of the catalytic oxidative desulfurization (OD) activity of alumina-supported polymolybdates (Mo/Al2O3) was carried out using organosulfur model compounds and diesel fuel. Hydrogen peroxide was the oxidizing reagent. Ultra-deep desulfurization, 97.8% removal of sulfur in diesel fuel, was achieved by reaction under mild conditions followed by solvent extraction. The catalyst was prepared by equilibrium adsorption and characterized by infrared, Raman, X-ray photoelectron, 31 P and 27 Al MAS NMR spectroscopies. Our results indicate that the phosphomolybdate used during synthesis of the catalysts decomposes and forms hydrated hepta- and octamolybdates as well as phosphate ions on the surface of alumina. # 2006 Published by Elsevier B.V.

Sol-gel titania was phosphated in two different ways: i) “in situ” phosphation using phosphoric acid as hydrolysis catalyst in the titanium butoxide gelling system, and ii) gelling with nitric acid and impregnation with ammonium phosphate solution. In calcined samples at 600°C a positive effect on the specific surface area for the “in situ” phosphated sample was found. X-ray diffraction patterns showed that the presence of phosphates ions stabilized the anatase phase. FTIR-pyridine adsorption identified only Lewis acid sites in phosphated samples. In the isopropanol decomposition for “in situ” phosphated titania, the activity was six times higher than that obtained for titania phosphated by impregnation, showing strong acidity for the in situ phosphated TiO2 catalyst.

Corrosion inhibition of steel in hydrochloric acid by decylamides of α-amino acids derivatives was studied using gravimetric and electrochemical techniques. Protection efficiencies of 90% were obtained with 100 ppm of tyrosine and glycine derivatives, while alanine and valine derivatives reached only 80%. The order of increasing inhibition efficiency was correlated with the modification of the molecular structure of inhibitors. Potentiodynamic polarization curves indicated that both the decylamide of tyrosine and glycine acted primarily as anodic type inhibitors, whereas the decylamide of alanine and valine were of the cathodic type. Thermodynamic parameters and Flory–Huggins adsorption isotherms described the experimental findings. The number of active sites, equilibrium constant, enthalpy and change of free energy were computed for all inhibitors studied. This information suggested that organic molecules were adsorbed and displaced water molecules from the steel surface. X-ray photoelectron spectroscopy confirmed that species of N, C and O interacted with steel to form a continuous protective film.

Al 2 O 3 materials were obtained by calcination of boehmite samples of varying crystallinity at 600 °C. Boehmites were obtained from Al 2 (SO 4 ) 3 ·18H 2 O or AlCl 3 under hydrothermal conditions and autogenous pressure at different synthesis temperatures ( T s = 40, 140 and 180 °C), and were studied by XRD, IR(Py), DTA and TGA. It was found that T s is closely related to the physicochemical properties of boehmites, and thus of γ-Al 2 O 3 . Increased amounts of sulfur were detected in γ-Al 2 O 3 for lower T s using aluminum sulfate. Less-crystalline boehmites were obtained when using aluminum sulfate compared to aluminum chloride. While only Lewis acidity was found in γ-Al 2 O 3 materials produced from aluminum chloride, aluminum sulfate produced both Lewis and Bronsted acidity, with the Bronsted/Lewis ratio depending on the crystallite size.