Alternative Properties in Liquid Fuels and Blends

This work summarises the results of the research program at the Renewable Energy Group (GER) of the University of Buenos Aires on alternative properties for the characterization of liquid fuels. The study included fossil fuels: diesel fuel, gasoline, and methanol, and biofuels: biodiesel from different feedstocks and bioethanol. Blends of diesel fuel/biodiesel, gasoline/bioethanol, gasoline/methanol, biodiesel/butanol, and diesel fuel/biodiesel/butanol were also studied. The electrical, acoustical, and optical properties of fuels and blends were determined as a function of temperature and composition. From these results, the composition of blends was accurately estimated from measurements of permittivity and temperature. The research program included the study of correlations of the alternative properties with those indicated in the international quality standards for liquid fuels (kinematic viscosity, methanol content, flash point). These correlations make possible to verify the quality of liquid fuels with simpler and more convenient measurements in industrial settings, and also in the laboratory.Fil: Romano, Silvia Daniela. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles; ArgentinaFil: Sorichetti, P. A.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentin

Using Terahertz Time-Domain Spectroscopy to Discriminate Among Water Contamination Levels in Diesel Engine Oil

Terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 2.0 THz was evaluated for discriminating among water contamination levels (0%, 0.1%, and 0.2%) in diesel engine oil (SAE 15W-40). The absorption coefficient demonstrated potential to discriminate among the three water contamination levels with significant differences among all three levels across the 1.111 to 1.332 THz and 1.669 to 1.934 THz ranges. At each of these frequency ranges, each water contamination level was significantly different from the other two. The 0% water contamination level had the lowest absorption coefficient, while 0.2% water had the highest absorption coefficient. The refractive index demonstrated greater potential to discriminate among water contamination levels with significant differences among all three water levels across the 0.5 to 1.5 THz range. The refractive index of 0% water was the lowest and 0.2% water was the highest across the THz range. Linear regression analysis of the refractive index as a predictor of water contamination level yielded a highly significant equation (p \u3c 0.0001, R2 = 0.99, RMSE = 0.01) when using the refractive indices at 0.5 THz. The refractive indices of these oil samples were promising for discrimination of water contamination. THz spectroscopy should be evaluated for discriminating other engine oil contaminants

Discriminating gasoline fuel contamination in engine oil by terahertz time-domain spectroscopy

Gasoline engine oil (SAE 5W20) was contaminated with four levels (0%, 4%, 8% and 12%) of gasoline fuel and submitted to terahertz time-domain spectroscopy (THz-TDS). Three sampling methods were used to compare measurement variations. For all sampling methods, refractive index decreased with increased fuel contamination and absorption coefficient increased with increased fuel contamination. Absorption coefficients were significantly different for each fuel contamination level for each sampling method across the entire 0.5–2.5 THz range. The frequency of 0.5 THz produced the best model of absorption coefficient predicting fuel contamination with a rootmean- square error of 0.21% points. THz-TDS demonstrated high potential for estimating gasoline fuel contamination in gasoline engine oil

A Simple Capacitive Method To Evaluate Ethanol Fuel Samples

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Ethanol is a biofuel used worldwide. However, the presence of excessive water either during the distillation process or by fraudulent adulteration is a major concern in the use of ethanol fuel. High water levels may cause engine malfunction, in addition to being considered illegal. Here, we describe the development of a simple, fast and accurate platform based on nanostructured sensors to evaluate ethanol samples. The device fabrication is facile, based on standard microfabrication and thin-film deposition methods. The sensor operation relies on capacitance measurements employing a parallel plate capacitor containing a conformational aluminum oxide (Al2O3) thin layer (15 nm). The sensor operates over the full range water concentration, i. e., from approximately 0% to 100% vol. of water in ethanol, with water traces being detectable down to 0.5% vol. These characteristics make the proposed device unique with respect to other platforms. Finally, the good agreement between the sensor response and analyses performed by gas chromatography of ethanol biofuel endorses the accuracy of the proposed method. Due to the full operation range, the reported sensor has the technological potential for use as a point-of-care analytical tool at gas stations or in the chemical, pharmaceutical, and beverage industries, to mention a few.7CAPESCNPq [483550/2013-2]FAPESP [2013/22127-2, 2014/25979-2]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Experimental and numerical investigation of pilot scale microwave assisted transesterification process for biodiesel production

The goal of this study was to design and test a pilot scale process for biodiesel production using advanced microwave technology and develop a numerical model for investigating various parameters affecting this process. Dielectric properties of materials play a major role in microwave design of a process. The dielectric properties (dielectric constant ε’ and dielectric loss ε”) of biodiesel precursors: soybean oil, alcohols and catalyst and their different mixtures were measured at four different temperatures (30°C, 45°C, 60°C and 75°C) and in the frequency range of 154 MHz to 4.5 GHz. Results indicate that the microwave dielectric properties of almost all components depend on both temperature and frequency. Addition of catalyst changed the properties of solvent due to the strong ionic nature. A scaled up version of a continuous microwave transesterification process was designed, built and tested. Experimental parameters were set based on previous laboratory scale results. Experiments were performed in a well controlled continuous pilot scale microwave reactor at temperatures of 60°C and 75°C and processing times of 5 to 15 minutes. Microwave power required to achieve the temperature of 60°C was 4000W and for 75°C was 4700W. Ethanol was used as a solvent with NaOH as a catalyst (\u3c 0.2% by weight of oil). The conversion obtained was \u3e99% for all experimental conditions. The final objective was to develop a basic numerical model of continuous electromagnetic heating of biodiesel precursors. A finite element model was built using COMSOL Multiphysics 4.2 software. High frequency electromagnetic problem was coupled with the non-isothermal flow problem. The model was tested for the two different power levels. The electric field, electromagnetic power flow and temperature profiles were studied. Resulting temperature profiles were verified by comparing to the experimental data. The presented study assists in understanding microwave heating application for biodiesel production. The dielectric property analysis gives a clear picture of interaction of biodiesel components with microwave irradiation, numerical model aids in understanding temperature distribution while experiments validate the results. This study can be applied to optimize the microwave assisted continuous biodiesel production process

DEVELOPMENT OF BIOPOLYMERS AND THEIR MODIFIED FORMS AS SUSTAINABLE SORBENT MATERIALS

The production of ethanol in the biofuels industry requires methods to remove water from mixtures to improve biofuel quality. To address the large energy footprint of conventional distillative separation of biofuels and water, new materials and methods are required to reduce GHG emissions and to develop more sustainable industrial processing. The overall goal of this research focuses on the sorption properties of biopolymers and their modified forms as adsorbents for fractionation of chemical mixtures such as water/ethanol in binary systems. The short term goals of this thesis are related to the synthesis, characterization, and evaluation of the sorption properties of biopolymers and their modified forms. Moreover, a long term goal relates to the development of biopolymer materials with tunable adsorptive properties for the fractionation of binary water-ethanol (W-E) mixtures. Biopolymers such as starch (linear and branched) and cellulose were modified with variable amounts of epichlorohydrin (EPI) as a cross-linker for the enhancement of physicochemical properties related to sorption processes. The characterization of materials included Thermogravimetry Analysis (TGA), Infrared spectroscopy (FT-IR) and NMR spectroscopy. These methods provided support that incorporation of incremental levels of cross-linker with the biopolymers resulted in variable structure and physicochemical properties related to sorption. This thesis describes four leading edge contributions related to the objectives of this study: i) The development of biopolymers and their modified forms for the controlled uptake of ethanol in binary W-E systems, ii) Evaluation of the adsorption properties using dye probes, nitrogen adsorption, and the use of quantitative NMR (qNMR) spectroscopy as a convenient and rapid analytical tool to quantify uptake of both water and ethanol content in binary solvent systems, iii) Evaluation of biomass and its biopolymer components for the fractionation of W-E mixtures, and iv) Evaluation of the role of solvent effects on the adsorption properties of biopolymers. Based on the results herein, the biopolymer adsorbents displayed preferential uptake of water over ethanol in binary W-E solutions. The adsorptive solvent uptake selectivity (Rselectivity; Qm(W)/Qm(E)) of water over ethanol for a given sorbent material requires an understanding of hydration phenomena, biopolymer structure, and textural properties of adsorbent materials. This thesis contributes to a molecular-level understanding of the solvent fractionation properties of biopolymers and their modified forms, along with the development of green strategies for biofuel separation. The isotherm modeling results show that the monolayer adsorption capacity (Qm) of ethanol and water by cellulose biopolymer materials along with its cross-linked forms cover a range (Qm= 1.13−2.44 g/g) of values. The parameters indicate heterogeneous adsorption behaviour, in agreement with the Sips exponential fitting parameter (ns ≠ 1). The Rselectivity values ((Qm(W)/Qm(E)) obtained at saturative conditions are variable (1.10 to 2.03) and further illustrate that cellulose materials display molecular selective solvent fractionation in binary W−E solutions. By comparison, the Qm values for starch and its cross-linked forms varied from 0.01 to 2.70 g·g−1 for water and ethanol in binary mixtures according to the Sips isotherm model. The Rselectivity (Qm (W)/Qm(E)) values of starch-EPI adsorbents for water (W) and ethanol (E) in the binary mixtures range from 3.8 to 80. As well, the isotherm results show that the monolayer adsorption capacity (Qm; g.g−1) of biomass such as miscanthus with water Qm (W) and ethanol Qm (E) fractions were determined by the best-fit Sips model isotherm parameters for raw Miscanthus (Qm (W) =8.93 and Qm (E) =4.15 g.g-1) and pretreated Miscanthus (Qm (W) =4.73 and Qm (E) =3.22, g.g-1). The fractionation properties of Miscanthus revealed variable Rselectivity (Qm(W)/ Qm(E)) values: raw Miscanthus (Rselectivity=3:1); pretreated Miscanthus (Rselectivity = 1.5:1), and lignin isolates (Rselectivity = 1: 5.4). The solvent interactions of biopolymers impact their biodegradability, recyclability and tunable physicochemical properties for various applications that employ composite materials, pharmaceutical delivery systems, paper production, fibers and biofuel production. Studies of the hydration properties of these materials were carried out that include dielectric absorption, Raman spectroscopy and Differential Scanning Calorimetry (DSC) to determine the structural and thermodynamic properties that reveal differences in biopolymer-solvent interactions that depend on the nature of the system

Strategies to overcome interferences during biomass monitoring with dielectric spectroscopy

Dielectric spectroscopy is extensively used to measure the level of viable biomass during fermentations but can suffer from interference by a variety of factors including the presence of dead cells, bubbles, electric and magnetic fields, changes in the medium composition, conductivity changes and the presence of non-cellular particles. Three different approaches were used to overcome these problems. The first involved the separate measurement of the spectra of the interferent and the cells. If the spectra were significantly different then spectra containing the signals of both cells and the interferent could be deconvoluted to separately determine the relative contribution of the cells and the interferent to the spectra. This deconvolution approach was successfully used to estimate the biomass levels of yeast in the presence of spent grains of barley and hardwood in the medium. A similar approach allowed the interference of electrode polarisation on spectra of yeast and microalgae to be compensated for. An attempt to determine the concentration of non-viable cells in a mixture of dead and live cells was less successful because the signal of the non-viable cells was quite small compared to that of viable cells. A second approach involved the use of a filter to keep the interferent away from the probe surface. This was used successfully in the measurement of the yeast concentration in the presence of spent barley grains. A third approach involved the use of a second sensor in addition to the biomass sensor. This allows the signal of the biomass sensor to be compensated for the interferent. In one set of experiments microelectrodes were developed which were able to confine the electric field to a small volume near the electrode surface. Covering the electrode surface with a gel or a membrane stopped cells from entering this volume whilst allowing medium to diffuse through. This allowed the measurement of changes in the electrical properties of the medium without a contribution by the cells. Whilst this approach worked, the response time was too long for practical use. More successful was the simultaneous measurement of the biomass with an infrared optical probe and a dielectric probe. It was found that the signal of the optical probe was independent of the cell viability, whilst the dielectric probe was quite insensitive to non-viable cells. The combined use of the dielectric probe and the optical probe allowed the culture viability to be determined in a straightforward manner