Lucia R. Raddi de Araujo

Pt-Cr/ZSM-5 catalysts for propane and cyclohexane conversions

Abstract The effect of chromium on the structural and catalytic properties was investigated for Pt-Cr/ZSM-5 system. From TPR measurements it is seen that the reduction profiles were modified by the addition of Cr to the Pt/ZSM-5. Chemissorption data showed that Cr promoted the Pt dispersion. The propane and cyclohexane reactions showed higher activity and aromatic selectivity for the bimetallic samples when compared to the single Pt/ZSM-5 system. Unlike the Pt/ZSM-5 catalyst at higher cyclohexane conversions the hydrogenolysis did not occur on the bimetallic system, and this behavior increases the efficiency by eliminating undesirable parallel reactions. The Pt–Cr interaction seems to be favored and not only prevents the migration of Pt particles to the external zeolite surface but also weakens the Pt interaction with reactant intermediates, inhibiting hydrogenolysis

H3PO4/Al2O3 catalysts: characterization and catalytic evaluation of oleic acid conversion to biofuels and biolubricant

Al2O3 and H3PO4/Al2O3 catalysts were investigated in the conversion of oleic acid to biofuels and biolubricant at 1 atm and at 623 K. The catalytic tests were performed in a fixed bed and continuous flow reactor, using an oleic acid-catalyst ratio of 4 and N2 as the carrier gas. The reaction products were analyzed by gas chromatography and acidity measurements. N2 adsorption-desorption, X ray diffraction, 31P nuclear magnetic resonance and FT-IR spectroscopy were also employed to evaluate the textural, structural and acidic properties of the catalysts. The results showed that phosphoric acid impregnation improved the alumina decarboxylation activities, generating hydrocarbons in the range of gasoline, diesel oil and lubricant oil. The best catalytic performance was achieved with the highest surface area alumina impregnated with H3PO4, which was the solid that allied high total acidity with a large quantity of mesopores.

Decolorization and mineralization of reactive dyes by a photocatalytic process using ZnO and UV radiation

Reactive dyes are one of the major pollutants in textile wastewater and a concern because they are not easily degraded by conventional wastewater treatments. Heterogeneous photocatalysis has been considered an effective option for treating wastewater containing those dyes. This research work assesses the photocatalytic degradation of reactive dyes using UV irradiation and pure or impregnated ZnO. In addition to photocatalysis, separate photolysis and adsorption experiments were conducted but showed low efficiency. The dye degradation was monitored by UV-Vis spectroscopy and mineralization was determined by total organic carbon (TOC) analyses. Total color removal was achieved after 30 min of irradiation using pure ZnO. The Black 5 dye photocatalytic decolorization reaction followed first-order kinetics, while Yellow 145, Red 4 and Blue 21 dyes followed zero-order kinetics. TOC removals in the range of 70-80% were achieved after 240 min of individual photocatalytic treatment with ZnO. The performance of each photocatalyst was also compared when the four dyes were mixed together and the order of efficiency in the mineralization process was as follows: Fe/ZnO > ZnO > Co/ZnO. This result was explained by the crystal field theory.

The use of niobium based catalysts for liquid fuel production

The catalytic properties of niobium based catalysts were investigated in the conversion of oleic acid to liquid fuels at atmospheric pressure and at 623 K. The catalytic tests were performed in a fixed bed and continuous flow reactor using an acid to catalyst ratio equal to 4 and N2 as carrier gas. The reaction products were analyzed by gas chromatography and acidity measurements. NH3 temperature programmed desorption, N2 adsorption-desorption (BET method) and Xray diffraction were also performed in order to determine the structural and acidic properties of the catalysts. From the catalytic tests, it was detected the formation of compounds in the range of gasoline, diesel and lubricant oils. Higher catalytic activity and selectivity for diesel fuel were observed for the catalysts NbOPO4 and H3PO4/Nb2O5 that possesses higher acidities and surface areas.

Prediction of fatty methyl esters and physical properties of soybean oil/biodiesel blends from near and mid-infrared spectra using the data fusion strategy

The data fusion strategy was compared to the conventional sensor methodology to evaluate the refractive index, the relative density, and the total fatty acid methyl esters in soybean oil/biodiesel blend samples using near infrared and mid-infrared spectral data coupled with linear and non-linear regression methods. The refractive index and the relative density values were obtained using a refractometer and densimeter system. The fatty acid methyl ester values were acquired by gas chromatography using the standard method (EN-14103:2011). The data fusion approach was applied successfully and showed the lowest root standard error of prediction (RSEP), at least for the refractive index and fatty acid methyl esters in relation to other strategies.

Heterogeneous Photocatalytic Degradation of Acid Dyes in Aqueous TiO2 Suspensions: Kinetics and Toxicity

Abstract This work assesses the photocatalytic (TiO2/UV) degradation of a simulated acid dye bath (Yellow 3, Red 51, Blue 74, and auxiliary chemicals). Color and phytotoxicity removal were monitored by spectrophotometry and lettuce (Lactuca sativa) seeds as the test organism, respectively. Mineralization was determined by DOC analyses. Photocatalytic, photolytic, and adsorption experiments were performed, showing that adsorption was negligible. After 240 minutes of irradiation, it was achieved 96% and 78% of color removal with photocatalysis and photolysis, respectively. 37% of mineralization occurred with photocatalysis only. The dye bath was rendered completely non-toxic after 60 minutes of photocatalytic treatment; the same result was only achieved with photolysis after 90 minutes. A kinetic model composed of two first-order in series reactions was used. The first photocatalytic decolorization rate constant was k1 = 0.062 min-1 and the second k2 = 0.0043 min-1, approximately two times greater than the photolytic ones.