Luiz E.P. Borges

Role of Oxophilic Supports in the Selective Hydrodeoxygenation of m-Cresol on Pd Catalysts

The hydrodeoxygenation of m-cresol has been studied on SiO2- and ZrO2-supported Pd catalysts. Regardless of metal dispersion, the latter exhibit greatly enhanced selectivity to toluene. This remarkable support effect can be explained in terms of a mechanism that involves a keto-intermediate tautomer favored by oxophilic sites on the support.Graphical Abstract.

Tuning Surface Basic Properties of Nanocrystalline MgO by Controlling the Preparation Conditions

Different nanocrystalline magnesias were synthesized by precipitation and hydrothermal treatments of aqueous salt solutions in an attempt to tune their surface basicity. CO(2) was chosen as an acidic molecule to probe the basic sites by both temperature-programmed desorption and infrared spectroscopy. All samples were shown to be crystalline, and except that obtained by nitrate decomposition, they all possessed high surface areas. The oxides presented different basic site distributions, evidencing the significant role of the preparation conditions on tuning the surface basicity: while medium-strength basic centers are dominant in the samples prepared by precipitation aging or hydrothermal treatment, the one obtained by precipitation features a roughly equal concentration of medium-strength and strong centers. Infrared spectra revealed that hydrogen carbonate and monodentate and bidentate carbonates were formed in distinct proportion on all oxides. However, the bidentate complexes were shown to have different thermal stabilities; the more stable species are thought to be formed on acid-base pair centers associated with an anionic vacancy. Distinct morphological and structural characteristics were also observed by high-resolution transmission electron microscopy. It was consistently found that the high-surface area samples are formed by aggregates of nanoparticles (2-5 nm) randomly oriented and with a high concentration of structural defects. These findings allowed us to conclude that the surface heterogeneity promoted during synthesis increases the concentration of basic sites and plays an important role in tuning the basicity of the solids.

Evaluation of standardisation methods of near infrared calibration models

The standardisation of eight partial least squares calibration models for the prediction of diesel oil properties was studied. The models were developed using spectra acquired on a laboratory accousto-optic tunable filter (AOTF) near infrared (NIR) spectrophotometer (with a quartz cuvette) and transferred to another AOTF-NIR spectrophotometer (with a fibre-optic probe) and to an Fourier transform NIR spectrometer, both designed for on-line application. Thirteen standardisation methods, using different approaches, were studied: standardisation by the pretreatment of spectra, (piecewise) direct standardisation and (piecewise) reverse standardisation. The reverse approach proved to be the best strategy to transfer the models.

Cracking and hydrocracking of triglycerides for renewable liquid fuels: alternative processes to transesterification

Os processos industriais mais utilizados na producao de combustiveis liquidos semelhantes ao diesel usam catalisadores homogeneos basicos atraves das metanolise e etanolise de oleos tais como os de soja, canola, palma entre outros. Desse modo, se obtem o biodiesel. Por sua vez, transformacoes termo-cataliticas usando as facilidades existentes nas refinarias de petroleo sao alternativas que merecem atencao devido a sua viabilidade economica. De fato, tres processos industriais ja estao em funcionamento e novos projetos estao em fase final para comercializacao. O presente trabalho analisa os experimentos ja realizados por pesquisadores brasileiros nas areas do craqueamento, do craqueamento catalitico e do hidrocraqueamento catalitico dos oleos vegetais puros ou modificados. A partir dos resultados descritos, sao sugeridas novas direcoes destas pesquisas para os proximos anos. The most used industrial processes for the production of liquid fuels like diesel type are based on the methanolysis and ethanolysis of various oil reactants, such as palm, soybean and rapeseed oils, in the presence of homogeneous base catalysts. However, thermal and catalytic transformations of vegetable oils using available reactors and industrial processes are possible alternatives and deserve attention. In fact, three industrial processes are operating and new projects are announced. The present work analyses the experimental studies performed up to now by Brazilian researchers in the field of cracking, catalytic cracking and hydrocracking of pure or modified vegetable oils. From the published results, some research areas for the near future are suggested.

Determination of the carcinogenic potential of lubricant base oil using near infrared spectroscopy and chemometrics

Abstract In the present study, near-infrared (NIR) spectroscopy and chemometrics techniques have been combined to predict the carcinogenic potential of lubricant base oils. Principal component analysis was used to select the relevant wavelengths of the NIR spectra and principal component regression was employed to develop linear models to predict the total polyaromatic assay (IP 346) and the mutagenicity index (ASTM E1687/95) of lubricant oil samples. The good correlation between NIR normalised spectra (r=0.995; RMSEP=0.4%) and the total polyaromatic assay is discussed. It was concluded that the combination of both techniques could be used for the on-line determination of the carcinogenic potential of lubricant oils.

Lactic acid production from hydroxyacetone on dual metal/base heterogeneous catalytic systems

Oxidative aqueous-phase catalytic conversion of hydroxyacetone to lactic acid was investigated under mild and green reaction conditions. Dual metal/base catalyst systems were applied to replace the alkali hydroxide and address the separation requirements and corrosiveness issues usually involved in similar processes. Pt/Al2O3 was taken as the supported metal catalyst while Mg–Al layered double hydroxides (LDH) and their derived 3D mixed oxides were exploited as basic solid catalysts. The anion embedded within the LDH interlamellar domain (nitrate or hydroxyl) and the LDH topology (lamellar or exfoliated 2D nanosheets) were also examined. Activity and chemoselectivity of the dual system were shown to be tailored by the morphology, topology and basicity of the base catalyst. Catalytic activity was up to five times higher by adding a heterogeneous base solid to the metal catalyst. Surface site distribution was also shown to be quite decisive to the catalyst performance; the proximity of metal and basic centres on the same surface rendered highly selective bifunctional catalysts. A remarkable 100% selectivity to lactic acid was reached and the undesired cascade oxidation of lactic to pyruvic acid was hindered.

Predictive QSPR analysis of corrosion inhibitors for super 13% Cr steel in hydrochloric acid

An experimental and theoretical study on the inhibition corrosion efficiencies of twenty three compounds in hydrochloric acid (15% w/v) on 13% Cr modified stainless steel (martensitic) has been carried out. This inhibitor set includes amines, thiourea derivatives and acetylenic alcohols. Experimental weight losses at 60oC were correlated with group and quantum AM1 descriptors obtained from QSPR analysis. Such data, for a large set of molecules, offer a unique opportunity for searching for correlations between inhibition corrosion efficiency and molecular properties. Calculations based on three different statistical methodologies were carried out. The first method, using calibration procedures, employs an ordinary least squares (OLS) methodology with a simple descriptor selection based on R2 values. From this procedure, we obtained a model, Y15, having a R2 value of 0,979 and a Q2 value of 0.786. The second method employs a descriptor selection based on the second-order cross-validation OLS procedure (SOCV-OLS). In this process, the variables are chosen according to their ability to predict molecular inhibition efficiencies. The best model obtained using this methodology, Q5, had R2 and Q2 values of 0.859 and 0.785, respectively. The third method, based on regular partial least squares (PLS), resulted in R2 and Q2 values of 0.859 and 0.754, respectively. All calculations were carried out for the weight isoesteric Langmuir adsorption function (WILA function), ln(qM/(1-q )) or ln Kads. A careful comparison between the calibration and the cross-validation descriptor selection indicated that they had very few descriptors in common. This article presents some key equations and the most relevant descriptors. We are unaware of any similar QSPR study on super 13% Cr stainless steel in the literature.

Synthesis of Ethyl Acetate by Coupling a Heterogeneous Catalytic System with a Pervaporation Unit

Abstract The synthesis of ethyl acetate was investigated using a heterogeneous catalyst and a pervaporation unit. Shifting the reaction equilibrium by selective water removal increased the ethyl acetate productivity. Commercial acid resin, Amberlyst 15 (Rohm and Haas), and commercial hydrophilic composite membrane, PERVAP 1000 and 1001 (Le Carbone Lorraine), were used. The effects of catalyst mass, reaction temperature, and initial reactants ratio were studied. The kinetic parameters, such as activation energy and apparent reaction order, were determined. The water production and removal rates obtained in reaction and pervaporation experiments, respectively, were used in a computational code to simulate the behavior of the coupled system. The highest conversion was observed when an initial ethanol/acetic acid molar ratio of 9:1 was used. At this condition, the water production was reduced turning the water removal process more selective, increasing the acetic acid conversion from 51.0% to 63.9%.

Determination of Lubricant Base Oil Properties by near Infrared Spectroscopy Using Different Sample and Variable Selection Methods

The use of near infrared (NIR) spectroscopy and chemometrics for the prediction of seven lubricant base oil properties was studied. The partial least-squares calibration models were developed using spectra acquired on an acousto-optic tunable filter (AOTF)-NIR spectrophotometer equipped with a fibre-optic probe in the 1100–1700 nm region. In this work, 88 samples obtained from three Brazilian refineries over a period of two years were employed. Different variable selection and sample selection methods were also investigated. The partial least squares regression (PLSR) models thus obtained showed good correlation coefficients for the properties studied and the calculated root mean square errors of prediction (relative density = 0.0005 g cm−3; molecular weight = 12 g mol−1; flash point = 7°C; temperature 50% recovered = 6.5°C; aromatic carbon assay = 0.5%; naftenic carbon assay = 1.0% and parafinic carbon assay = 1.4%) were lower than half the reproducibility values defined by the ASTM methods, except for the relative density. These results indicate, therefore, the potential of the NIR spectroscopy and chemometric techniques for on-line lubricant oil production process control.

QSPR prediction analysis of corrosion inhibitors in hydrochloric acid on 22%-Cr stainless steel

Corrosion inhibitors have been widely used to prevent corrosion on stimulation operations on petroleum wells. Detailed experimental and theoretical investigation of twenty three different compounds including amines, thiourea derivatives, and acetylenic alcohols were carried out to estimate their inhibition corrosion efficiency on 22% Cr stainless steel (austenitic-ferritic, duplex) in hydrochloric acid (15% m/v) solutions. The obtained data were theoretically interpreted with respect to prediction, regression analysis (OLS), principal analysis component (PCA) and partial regression analysis (PLS) employing quantum and group contribution descriptors. In our study we found advantage in the use of the weight isoesteric Langmuir adsorption function (WILA), ln(qM/(1-q)) or lnKads. Excellent correlations were obtained for most models and few equations, results, calibration and validation plots were discussed in the text. The content of the present work represents a first step toward an efficient estimation of the inhibition corrosion efficiency (ICE) of arbitrary inhibitors towards several metals, alloys and steel types.