DSpace Collection:

Uso de espectrometria no infravermelho médio, calibração multivariada e seleção de variáveis por intervalos na quantificação de biodieseis em misturas com diesel

Fri, 18 Mar 2016 00:00:00 GMT

Title: Uso de espectrometria no infravermelho médio, calibração multivariada e seleção de variáveis por intervalos na quantificação de biodieseis em misturas com diesel Abstract: In Brazil, since November 2014, it is required by law an addition of 7% (v/v) of biodiesel to diesel, and this mixture is called B7. According to the report issued by National Brazilian Agency of Petroleum, Natural Gas and Biofuels in 2015, 33.6% of commercial diesel samples examined presented biodiesel content outside quality specifications. Therefore, this work aims to develop and validate methodologies to quantify methyl and ethyl biodiesel from soybeans, used frying oil, cottonseed and jatropha into binary mixtures with diesel, using Mid Infrared Spectroscopy (680 to 3100 cm-1) and multivariate calibration by Partial Least Squares (PLS). Furthermore, we present a study of application of variable selection methods for intervals as Interval Partial Least Squares (iPLS), Backward Interval Partial Least Squares (biPLS) and Synergy Interval Partial Least Squares (siPLS). Thus, the models built from spectral intervals, which provided, statistically, lower Root Mean Square Error of Prediction (RMSEP) and fewer variables compared to the model of full spectrum, were validated to determine the respective type of biodiesel mixed with diesel. The results of the global PLS models, to all kinds of biodiesels, demonstrated excellent correlation between actual and predicted values of the prediction set (R > 0.99), in the range of concentration of 1.00 to 30.00% (v/v), values of RSMEP between 0.0473 and 0.1020% (v/v) and did not show systematic errors according to ASTM E1655 norm. The proposed global PLS models met the requirements of accuracy demanded by ABNT NBR15568 (RMSEP < 0.1%) besides using only one calibration model against two of the respective norm. In relation to Variable Selection methods by intervals, were efficient in the elimination of non-informative variables significantly improving the prediction of validation samples if compared to multivariate calibration by PLS models, with the exception of the models containing biodiesels from used frying oil and jatropha methyl biodiesel. Therefore, the developed methodologies are presented as a viable alternative to the usual analysis for determining the biodiesel content in mixtures as diesel.

Desenvolvimento de procedimentos de digestão de biodiesel assistidos por radiação ultrassônica visando à determinação de metais por técnicas eletroquímicas

Wed, 16 Dec 2015 00:00:00 GMT

Title: Desenvolvimento de procedimentos de digestão de biodiesel assistidos por radiação ultrassônica visando à determinação de metais por técnicas eletroquímicas Abstract: This thesis presents the use of ultrasonic radiation for the digestion of biodiesel samples (B100) for the determination of metal ions by electrochemical stripping techniques (potentiometric and voltammetric) using a glassy-carbon electrode modified with a mercury film. Biodiesel samples (50 mg) were subjected to digestion in glass tubes with a mixture of 3.0 mL of concentrated HCl and 4.4 ml H2O2 (30%), placed in an ultrasonic bath (40 kHz and 120 W) exactly on the higher intensity region (piezoelectric) of the ultrasound and sonicated for 40 min at room temperature (~ 20°C). These parameters were optimized using the chemometric technique of factorial design for the analysis of biodiesel samples spiked with ethanolic standard solutions of zinc, cadmium, lead and copper. Recovery values between 97 and 107% were observed in the optimal conditions found to zinc, cadmium, lead and copper. Residual carbon content (RCC) values after digestions were in the range of 3.05 to 3.75%. The simultaneous determination of zinc, cadmium, lead and copper using anodic stripping voltammetry revealed limit of detection (LD) values of 44 ng kg -1; 30 ng kg -1; 145 ng kg -1; 96 ng kg -1, respectively. Additionally, biodiesel samples (100 mg) were also treated in glass tubes with a mixture of 1.59 mL concentrated HCl and 3.0 ml H2O2 (30%) under sonication of an ultrasonic probe (sonication time 12.5 min, 25% amplitude, pulse of 5.0 s and time interval of 2.0 s). The parameters were also optimized employing the chemometric technique of factorial design for the analysis of spiked samples. Recovery values between 95 and 104% were observed in the satisfactory condition for zinc, cadmium, lead and copper. RCC values after digestions comprised values between 0.43 to 0.54%. For the simultaneous determination of zinc, cadmium, lead and copper using anodic stripping voltammetry obtained in the digestates employing the ultrasonic probe, the LD values found respectively for zinc, cadmium and copper were 25 ng kg -1 and for lead 56 ng kg -1. All results obtained using assisted digestion by ultrasonic bath and / or ultrasonic probe indicate that the proposed methods for the biodiesel sample preparation presents a comparable performance to traditional methods of digestion using acid blends, or yet digestions assisted by microwave radiation.

Estudo das propriedades físico-químicas de membranas de acetato de celulose/glicerol incorporadas com aditivos de lignina extraída do endocarpo da Macaúba (Acrocomia aculeata) e seus derivados modificados quimicamente

Fri, 11 Dec 2015 00:00:00 GMT

Title: Estudo das propriedades físico-químicas de membranas de acetato de celulose/glicerol incorporadas com aditivos de lignina extraída do endocarpo da Macaúba (Acrocomia aculeata) e seus derivados modificados quimicamente Abstract: Eight membranes of commercial cellulose acetate were prepared incorporating various additives, which changed their physicochemical properties. The membranes were divided into two groups (I and II) and their properties were evaluated. The four membranes of group they were prepared by adding, at a concentration of 0.1% (m / m) of the lignins extracted from the macaúba endocarp (Acrocomia aculeata) after purification and chemical modification. These four membranes were classified as to their composition as: (A) no additives (pure acetate); (B) with the purified lignin; (C) with the carboxymethylated lignin and complexed with Na+ (CML-Na) and (D) with carboxymethylated lignin and complexed with Al3+ (CML-Al). The other four membranes of group II has the same composition of Group I, but with added glycerol at a concentration of 10% (m / m). All eight membranes were prepared using a standard technique of spreading (casting method), after the dissolution in acetone. The percentage of 10% glycerol in membrane composition was determined in a previous study where the membranes prepared by the same technique, with a variable composition glycerol were studied and characterized. In this preliminary study membranes at concentrations of 0, 2.5, 5.0, 10.0, 15.0 and 20.0% (w / w) glycerol with acetate were dissolved in two solvents: acetone and a mixture acetone / water (80/20, v / v). The membranes with 10% glycerol shown in both solvents an increase of mechanical properties. The glycerol, as well as having plasticizer properties, is produced in large scale by first generation biodiesel industry, which uses the reaction transestrificação oils and fats. Concurrent with these studies, composition of the macaúba wendocarp was determined as the content of lignin, cellulose and hemicellulose. The large amount of lignin present in the endocarp (40.5%) and after purification (59.8%) showed that this residue has great potential for use of lignin. The macaúba after extraction of oils used in pharmaceutical industries and biodiesel discards lot of this waste without proper use. The characterization of the materials were made for determining the properties: morphology, by Scanning Electron Microscopy, SEM, structural: X-Ray Diffraction-XDR, hydrophobicity and barrier properties (contact angle and permeability to water vapor), thermal and thermomechanical properties: Differential Scanning Calorimetry - DSC, Thermo Gravimetric Analysis - TGA and Dynamical Mechanical Analysis - DMTA.

Produção de biodieseis etílico e metílico de pinhão manso por diferentes rotas catalíticas

Fri, 27 Nov 2015 00:00:00 GMT

Title: Produção de biodieseis etílico e metílico de pinhão manso por diferentes rotas catalíticas Abstract: The Jatropha curcas is an oilseed with large potential for production of vegetable oil and adjust very well to Brazilian`s climate and soil, including the region of the Caatinga. This study evaluates different forms of oil production and extraction of biodiesel from crude Jatropha curcas oil (OPMB). Extraction tests were carried out with different solvents, showing that the use of ethanol increases the process efficiency process from 36% to 39% in mass. Furthermore, the use of acid catalysis during the solvent extraction reduces the oil`s acidity from 25.93 mg KOH/g to 0.52 mg KOH/g . Using the OPMB as start material in a fractional factorial design and central composite design (CCD) to optimize the reaction conditions for production of biodiesel from Jatropha curcas (BMPM) optimized through the two-step catalysis, optimizing each step separately. In esterification (1st Step) the following variables were evaluated: Temperature (TP), Time reaction (TR), % H2SO4, Molar ratio (alcohol:oil) (RM), Alcohol type (TA) and Rotation speed (VR). The study obtained a maximum point at the central composite design (CCD), determining the best conditions to esterify the OPMB in: TP of 57.3 oC, TR of 173 minutes, 0.5% H2SO4 (w/w), RM (alcohol: oil) of 11.4: 1, methanol as TA and VR 400 rpm, producing a treaty Jatropha curcas oil (OPMT) with acidity at 0.49 mg KOH/g. Then was also optimized the transesterification reaction (2nd step) of OPMT evaluating the variables: TA, TP, RM, TA and % de KOH, obtaining a maximum yield of 97.3% under the following conditions: methanol as TA, TP 35 oC, RM of 10,0: 1, TR 49.8 minutes and 1.26% of KOH. Also are produced, heterogeneous catalysts from recyclable material, expanded polystyrene sulfonated (PSES) and sulfonated polyvinyl chloride (PVCS) that showed 0.43 and 0.32 mmol of acid groups/g, respectively. Using the heterogeneous catalysts in optimized conditions to esterify the OPMB a percentage of esterification (% E) of 93.33% for the PSES and 91.45% for PVCS. The biodiesels were prepared from OPM treated with: H2SO4, PSES and PVCS in optimized conditions, determining your physicochemical properties. The quality of the biodiesels obtained in this study was assessed by parameters established by ANP, observing that Jatropha curcas is a viable option for use as a raw material to product this biofuel.