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The trans-esterification and esterification of waste vegetable oil mainly under sub-critical temperature of methanol in the presence of sulfonated char were achieved. The carbonaceous materials were analyzed by means of various physical and chemical techniques such as Raman spectroscopy, X-ray diffractometry, temperature programmed desorption and X-ray photoelectrons spectroscopy. The carbon-based large-acidity catalyst showed good chemical and thermal properties and a high performance in the production of methyl esters from waste vegetable oil, which was easily separated from the liquid mixture. A temperature of 210°C, reaction time of 20 min and a catalyst amount of 0.03 g were the optimal experimental conditions for the trans-esterification of the vegetable oil with methanol giving a conversion to triglycerides of 96.5% according to the response surface methodology. The design of experiments type Box-Behnken was successfully applied to study effects of the parameters in the production of biodiesel and it presented optimal conditions for maximum performance with values near to those experimentally found. The catalyst was recovered from the final mixture by filtration and reused without regeneration showing a catalytic activity stable up to 4 or more reaction cycles. [ABSTRACT FROM AUTHOR]

Abstract: Anatase (TiO2) thin films were obtained by immersion of glass plates into a titanium sol–gel precursor followed by calcination at 450°C for 3h. The Raman results for the CO2 laser irradiated TiO2 films show that laser radiation is able to promote favorable changes of anatase phase in anatase/rutile mixtures. Nevertheless, the transformation process level depends on laser characteristics and scan speed of the radiation treatment. [Copyright &y& Elsevier]

Abstract: Thin films of paramelaconite, tenorite and their mixtures were deposited on fiberglass substrate by chemical vapor deposition and catalytically evaluated by isopropanol oxidation at low temperatures between 150 and 275°C. Copper oxides were deposited using bis(2,4-pentanedionato)copper(II) as a precursor and oxygen as carrier-reactant gas. Original crystalline phases deposited on fiberglass at different temperatures or formed subsequently were characterized by several analytical techniques. Films gave crystallite sizes from 6.5 to 8.4nm and a thickness around 230nm. The fiberglass with a paramelaconite film showed a relatively high catalytic activity, more than 40%, at 250°C. Nevertheless, the fiberglass with a tenorite film exhibited a catalytic activity of only 10% at the same temperature. Above 250°C the paramelaconite experienced a notable deactivation after which the catalytic activity decreased to 6.7% at 350°C and after this, the catalyst could not be reused. This activity loss was probably due to changes in the chemical phases on fiberglass by effect of temperatures above 250°C. [Copyright &y& Elsevier]

Abstract: Sol–gel derived rough anatase films without controlled particle sizes were prepared by surfactant templating. The coating sol–gel was obtained by hydrolysis of Ti(OC3H7)4 in ethanol/HNO3 solution. The gel films, prepared by dipping glass substrates in surfactant solutions, were dried after immersion under an atmospheric pressure. The rough films of TiO2 anatase were obtained after calcining at 500°C. The resultant films were transparent, semitransparent or opaque and 136–402nm thick. It was found that the TiO2 films prepared from the sol–gel with surfactant showed a granular nanostructure, and they were composed of regular particles, for example; between 50 and 70nm. The roughness of the films was found to depend on the surfactant concentration in the sol–gel solution and can show a roughness between 0.82 and near of 17nm. The photocatalytic activity of the films for the degradation and mineralization of phenol, an industrial pollutant, in water and under 365nm irradiation was improved by the surfactant modification. Kinetic analysis of degradation and mineralization of phenol in water were employed to evaluate the different TiO2 films under the same experimental conditions. The global photonic efficiency for degradation and mineralization of phenol ξ g, was calculated to facilitate comparison with a TiO2 standard photocatalyst named Degussa P-25. [Copyright &y& Elsevier]

Abstract: Substrate dipping in a composite sol–gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO2) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol–gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV–vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO2 film was obtained with a short immersion of fiberglass into the sol–gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 °C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO2 films prepared from the sol–gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 μm. Smooth TiO2 films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO2 films can enhance the inherent photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Anatase thin films (<200nm in thickness) embedding Degussa P25 TiO2 were prepared by sol–gel method. TiO2-anatase thin films were deposited on a fiberglass substrate and then ground to obtain glass microrods containing the composite films. The film structure was characterized using Raman spectroscopy, atomic absorption and UV–vis spectrophotometry, and atomic force microscopy. The photocatalytic activity of the composite films, calcined at 450°C, and the regeneration of the activity under the same experimental conditions, were assessed using gas chromatography to study the photodegradation of phenol, an industrial pollutant, in water under 365nm irradiation. The film with 15.0wt.% of P25 TiO2 was found to be more photoactive (54ppm of degraded phenol at 6h of illumination) than the other ones. [Copyright &y& Elsevier]

Abstract: Simple kinetic model is proposed for fitting experimental data of degradation and total organic carbon (mineralization) of phenol. Reaction rates analysis of phenol in water are employed to compare different photocatalysts under the same experimental conditions. The global photonic efficiency for degradation and mineralization of phenol ξ g, is calculated to facilitate comparison with other photocatalysts or experimental systems. Under identical conditions of catalyst loading, pH and phenol concentration the most of photocatalysts presented a global efficiency much lower than that for a TiO2 standard photocatalyst named Degussa P-25. However, two photocatalysts prepared by different methods showed approximately the same global efficiency than the commercial material. [Copyright &y& Elsevier]

The potential of Raman spectroscopy in the quantitative analysis of dilute organic contaminants on aluminum substrates is evidenced in this work. Methyl-parathion microdroplets, an organophosphorus pesticide, has been used as a probe for this purpose. The samples were analyzed on an aluminum foil, which is very easy to acquire and to adapt. Moreover, aluminum foil does not need a previous treatment. Linear and no-linear curves as a function of the concentration of methyl-parathion versus the Raman intensity of the 1345 and 1110 cm-1 peaks were established by means of a simple mathematical expression. A comparison with calibration curves fits very well, allowing quantification at concentration levels as low as parts per million. [Copyright &y& Elsevier]

The capability to obtain quantitative information of a simple way from Raman spectra is a subject of considerable interest. In this work, this is demonstrated for mixtures of ethanol with water and rhodamine-6G (R-6G) with methanol, which were analyzed directly in glass vessel. The Raman intensities and a simple mathematical model have been used and applied for the analysis of liquid samples. It is starting point to generate a general expression, from the experimental spectra, as the sum of the particular expression for each pure compound allow us to obtain an expression for the mixtures which can be used for determining concentrations, from the Raman spectrum, of the mixture. [Copyright &y& Elsevier]

We have used chemical deposition of copper complex solution to prepare CuO thin films on commercial fiberglass. The deposition of copper oxides was done in a beaker using a solution of thiosulfatocuprate (I) as precursor and NaOH as a film conditioner. In order to establish a correlation between experimental conditions and the produced copper species, as well as the film quality, the as deposited and annealed samples were characterized using X-ray diffraction, visible spectrophotometry and atomic force microscopy. The most important result is that a Cu2O 80-nm film can be obtained directly with a short immersion of fiberglass into the copper solution. The film growth of this copper phase occurred in [111] and [200] directions. Moreover, this phase is converted to CuO by annealing at 375 °C. [Copyright &y& Elsevier]

Cu2O–CuO and CuO thin films on a fiberglass substrate were prepared by chemical vapor deposition (CVD) and then catalytically evaluated by cyclohexane oxidation. The fiber with a Cu2O–CuO film showed a high catalytic activity at low temperatures, for example 43% at 350 °C, and a good selectivity to cyclohexanol production (37% at 300 °C). The fiber with a CuO film exhibited a higher catalytic activity, for example 48% at 350 °C, with a high yield of cyclohexanone (37% at 250 °C). A CuO/SiO2 catalyst with the same CuO content gave a result similar to the CuO/fiberglass system under the same conditions examined but, on the other hand cyclohexane was cleaved giving a higher selectivity to hexenes, 30% at 250 °C. The effect of reaction temperature on the catalytic activity and selectivity of cyclohexane oxidation were investigated. At 300 °C the steady-state catalytic performance of the CuO/fiberglass experienced a slight deactivation after 4 h time-on stream from 40% to 38% of conversion, after which, the catalyst could be reused apparently without any activity loss. [Copyright &y& Elsevier]

To coat fiberglass with copper oxides, in particular with the paramelaconite structure 6CuO·Cu2O, we have used the chemical vapor deposition (CVD) procedure of a copper precursor. The deposition of copper oxides was done using a horizontal-flow reactor, 2,4-pentanedionate copper(II) as precursor and O2 as carrier-reactant gas at several deposition temperatures. In order to establish a correlation between experimental parameters and the resulting copper species, as well as film quality, the samples that were produced, were evaluated using techniques such as X-ray diffraction (XRD), visible spectrophotometry, scanning electronic microscopy (SEM) and atomic force microscopy (AFM). The most important result is that 6CuO·Cu2O thin films are obtained over a short range of deposition temperatures. The film growth of this copper phase occurred in the [202] and [004] directions. [Copyright &y& Elsevier]

To contribute to the search for an oxygen-free biodiesel from vegetable oil, a process based in the oleic acid hydrodeoxygenation over Ni/γ-Al2O3 catalysts was performed. In this work different wt % of Ni nanoparticles were prepared by wetness impregnation and tested as catalytic phases. Oleic acid was used as a model molecule for biodiesel production due to its high proportion in vegetable oils used in food and agro-industrial processes. A theoretical model to optimize yield of n-C17 was developed using size, distribution, and wt % of Ni nanoparticles (NPs) as additional factors besides operational conditions such as temperature and reaction time. These mathematical models related to response surfaces plots predict a higher yield of n-C17 when physical parameters of Ni NPs are suitable. It can be of particular interest that the model components have a high interaction with operation conditions for the n-C17 yields, with the size, distribution, and wt % of Ni NPs being the most significant. A combination of these factors statistically pointed out those conditions that create a maximum yield of alkanes; these proved to be affordable for producing biodiesel from this catalytic environmental process. [ABSTRACT FROM AUTHOR]