Biodiesel production via ethylic transesterification with basic zeolites

Neste trabalho, teve-se como objetivo a preparação de zeólitas básicas através da modifcação de zeólitas USY com bário e estrôncio e sua aplicação na reação de transesterifcação de óleo de soja com etanol, para produção de ésteres de etila (biodiesel). Além disso, foram estudados os efeitos da geração de sítios básicos na superfície dos catalisadores, bem como suas respectivas atividades por três ciclos catalíticos. O biodiesel obtido nos ciclos foi analisado por HPLC, CG-FID e espectroscopia Raman. Já os catalisadores foram caracterizados por FTIR, análises térmicas e adsorção gasosa de piridina e CO2.Soybean oil transesterifcation with ethanol was carried out in a batch reactor using USY zeolites modifed with barium and strontium (15 wt.%) as catalysts. A series of three catalytic cycles were performed for each zeolite without any loss of activity. The biodiesel product was analyzed by HPLC and FT-Raman, and the catalysts by pyridine and CO2 adsorption. Ba/USY provided higher conversions (> 97%) than Sr/USY (< 75%). The increased catalytic activity of Ba/USY was attributed to two different effects: a larger number of basic sites; and a lower interaction between barium species and HUSY Brønsted sites

Polymers based on PLA from synthesis using D,L Lactic acid (or racemic lactide) and some biomedical applications : a short review

Poly(lactic acid) (PLA) is an important polymer that is based on renewable biomass resources. Because of environmental issues, more renewable sources for polymers synthesis have been sought for industrial purposes. In this sense, cheaper monomers should be used to facilitate better utilization of less valuable chemicals and therefore granting more sustainable processes. Some points are raised about the need to study the total degradability of any PLA, which may require specific composting conditions (e.g., temperature, type of microorganism, adequate humidity and aerobic environment). Polymerization processes to produce PLA are presented with an emphasis on D,L-lactic acid (or rac-lactide) as the reactant monomer. The syntheses involving homogeneous and heterogeneous catalytic processes to produce poly(D,L-Lactic acid) (PDLLA) are also addressed. Additionally, the production of blends, copolymers, and composites with PDLLA are also presented exemplifying different preparation methods. Some general applications of these materials mostly dedicated to the biomedical area over the last 10–15 years will be pointed out

The choice of the spectral region in the use of spectroscopic and chemometric methods

A method is presented for the choice of spectral regions when absorption measurements are coupled to chemometric tools to perform quantitative analyses. The method is based on the spectral distribution of the relative standard deviation of concentration (s c/c). It has been applied to the development of PLS-FTNIR calibration models for the determination of density and MON of gasoline, and ethanol content and density of ethanol fuel. The new method was also compared with the correlation (R²) method and has proved to generate PLS calibration models that present better accuracy and precision than those based on R²

Acidity and characterization of 12-Tungstophosphoric acid supported on Silica-alumina

This work deals with preparation and characterization of H3PW12O40 (H3PW) supported on silica-alumina. Impregnation of H3PW (15, 20, 30 and 40 wt.%) on commercial silica-alumina support in acidic aqueous solution is effective for preparing this catalyst keeping its Keggin structure, according to different methods of characterization. The catalysts were tested in a model reaction of acetic acid with ethanol and 30 wt.% H3PW/SiO2-Al2O3 had the highest activity under the conditions: catalyst calcination at 300 ºC, temperature of 100 ºC, acetic acid:ethanol molar ratio of 2:1 and catalyst:acetic acid mass ratio of 10 wt.%. The reaction yield was 79 and 100% selectivity for ethyl acetate over three reutilizations, for reaction time of 2 h. The calculated total acid site distribution was 0.299 mmol g-1 (97% of the theoretical probed by pyridine), and most of these (0.236 mmol g-1) were Brønsted weak-medium strength (pyridine desorption between 300 and 500 ºC)

Synthesis, characterization, and application of phosphotungstic acid supported on iron-based magnetic nanoparticles coated with silica

Magnetic nanoparticles based on magnetite (MNP) are important materials for different research applications, particularly when they are coated with inert phases. For instance, coating them with silica forms MNP@SiO2, which has various uses, including as a support for catalysts because it has surface functional groups that form bonds to a coating layer; the material presents itself with high magnetic susceptibility, turning it easily separable from the reaction in a heterogeneous medium. Herein, magnetite was synthesized and coated with tetraethy lorthosilicate (TEOS) and then used to support phosphotungstic acid (H3PW12O40, HPW). The X%HPW/ MNP@SiO2 materials were characterized by several techniques, such as EDXRF, XRD, SEM, FT-IR, low tem perature N2 physisorption, and pyridine gas adsorption/desorption (Py-TPD) and then applied to the esterifi cation reaction of oleic acid with ethanol. The results successfully indicated the synthesis of the catalysts, keeping the structural and magnetic characteristics of the MNP@SiO2 and providing a good dispersion and integrity of HPW on its surface. In the model reaction, high activity, selectivity (100%), and stability were observed, with yields of 98%, 66% and 54% of ethyl oleate when using 30%, 20% and 10%HPW/MPN@SiO2, respectively, for a reaction time of one hour and an acid to ethanol molar ratio of 1:6. No leaching of the active phase was detected up to four recycles of the best catalyst (30%HPW/MPN@SiO2).Instituto de Química (IQ

Liquid Phase Calorimetric Method as a Tool for Acid Strength Measurements and Application to a Variety of Sustainable Catalysts

It has been about 36 years since the first published paper about the calorimetry and adsorption (Cal-Ad) method by Prof. Drago. These separated methods are very old and important characterization tools for different molecules and materials, as recognized in chemistry. The idea of coupling these two techniques arose from the need to have more information about the thermodynamic parameters of a catalyst. The Cal-Ad method provides a measure of the magnitude (Ki), strength (−∆Hi), and quantity (ni) of sites present in a catalyst. The original idea is based on the application of the donor-acceptor concept using the Electrostatic Covalent Model, ECW in the areas of catalysis and material chemistry. Particularly, enthalpy measurements of acidity are directly related to the activity of various catalysts in a variety of reactions. Currently, more than twenty-five catalysts have been carefully characterized by this method in addition to spectroscopic and other thermal methods. Thus, this review seeks to present the fundamentals of the method and show different applications of the characterized catalysts for a variety of reactions in order to use these data as an alternative to choose a catalyst for an acid-dependent type reaction