Tesis doct.--Facultade de Xeografía e Historia--Universidade de Santiago de Compostela, 1995.
Bibliogr. p. 680-703. Index. Résumés en espagnol et en anglais.
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•Sugarcane bagasse was subjected to acid wash to improve levoglucosan production.•Alkalines were drastically removed after acid wash using HNO3/H2SO4 (0.2wt.%).•High levels of ...levoglucosan from volatile pyrolytic compounds were attained.
The aim of this work was to improve sugarcane bagasse thermochemical conversion to pyrolytic sugars production, particularly to levoglucosan. The experiments were carried out evaluating the effect of acid washing with HNO3 (0.1wt.%) followed by H2SO4 addition (0.1, 0.2 and 0.3wt.%) at pyrolysis temperatures of 350, 400, 450, 500, 550 and 600°C was studied by Py-GC/MS. The experimental results showed that HNO3 washing, followed by H2SO4 concentration of 0.2wt.% at 350°C resulted in an increase in levoglucosan yield between 5 and 7 times the yield obtained when the raw bagasse was processed. Thus, these results are very attractive to improve pyrolytic sugars production in sugarcane bagasse by previously acid treatment to pyrolysis technology.
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•Acetic acid washing improved the selectivity of sugarcane bagasse pyrolysis towards levoglucosan formation.•Acetic acid washing reduced biomass alkaline content.•The yield of some ...lignin derived compounds decreases in acid washed samples.
The aim of this paper is to improve the conversion of sugarcane bagasse to pyrolytic sugar levoglucosan through its pretreatment with acetic acid (10 wt.%) at 90 °C for 10 min under 200 rpm. Then, acid treated biomass was rinsed with deionized water to a neutral pH and dried in a vacuum oven at 70 °C up to constant weight. After acid treatment, the samples were subjected to fast pyrolysis in a Py-GC/MS. Thus, the impact of the acetic acid on the levoglucosan yield as well as other pyrolytic compounds released during pyrolysis process at different temperatures (from 350 to 600 °C) is reported. The best results respect to levoglucosan yield were attained when pyrolysis was performed at 400 °C resulting in around nine folds levoglucosan production from sugarcane bagasse after biomass treatment with acid compared to the control (untreated biomass samples) while the yield of some undesirable lignin derived compounds decreases in acid washed samples. The effect observed is due to the removal of the catalytic activity of alkali and alkaline earth metals. The attained results are very attractive because this pyrolytic sugar exhibits great potential as renewable feedstock for biofuels production and other bioproducts.
•The effect of pyrolysis temperature on the yield of levoglucosan depends on the nature of the feedstock studied.•The effect of pyrolysis temperature on most of the pyrolytic products can be ...explained if the compounds are grouped in five families (C1, C2, H, L1 and L2).•Most of the products of cellulose fragmentation reactions (C1 family) (glycoaldehyde, acetol, 2-oxo-propanoic acid) increase in yield as temperature increases.•Most of the phenolic compounds show a response to temperature changes that is independent of the feedstock processed.•The maximum yield of the products derived from lignin was found between 400 and 450°C.
This paper investigates the effect of pyrolysis temperature between 350 and 600°C on the distribution of pyrolytic products derived from Avicel, α-cellulose, Douglas Fir wood (softwood) and Hybrid Poplar wood (hardwood) by Py-GC/MS as a way to identify the best conditions for bio-oil production. The products were grouped in five families depending on their origin. The C1 family is formed by products of cellulose fragmentation reactions (glycoaldehyde, acetol, 1,2-ethanediol, monoacetate, butanedial). The products grouped in the C2 family (levoglucosan, levoglucosenone, 1,4:3,6-dianhydro-α-d-glucopyranose) are derived from cellulose depolymerization reactions. The molecules derived from hemicellulose (acetic acid, furfural, 2-furanmethanol) were grouped in the H family. The products derived from lignin were grouped in two families L1 (derived from p-hydroxyl phenol (H) and guaiacyl (G) structures) and L2 (derived from syringyl (S) structures). Principal components analysis was used to identify the main factors controlling the distribution of products. Our results show that the yield of most of the pyrolytic products can be explained in the five groups or families described above. Most of the C1 products derived from Avicel, α-cellulose and Douglas Fir fragmentation reactions increase in yield as the temperature increases. In the case of Hybrid Poplar these products reach a maximum at 400°C. CO2, 2-oxo methyl ester propanoic acid, 1,2-cyclopentanedione, 3-methyl, levoglucosenone, 1,4:3,6-dianhydro-α-d-glucopyranose, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, and most of the phenolic compounds show a response to temperature changes that is independent of the feedstock processed. As the temperature increased the yield of levoglucosenone (product of dehydration reactions) decreased for all the samples studied. Levoglucosan yield is however highly dependent on the feedstock used and, as such, its behavior with temperature changes is more difficult to predict. The maximum yield of the products derived from lignin (L1 and L2) was found between 400 and 450°C.
Ozonation on the phenols present in pyrolytic aqueous phases attained from biomass thermochemical conversion was evaluated. During ozonation, the dark color of original samples was found to decrease ...as a function of ozonation time. The oxidation kinetics of phenols was quantified by a method based on the color changes of samples. The oxidation profiles showed different behaviors and in some cases the phenols presented a positive correlation with the relative R color parameter, except eugenol, syringol, and vanillin which were markedly different. Finally, the color changes observed seem to be associated with the changes in the overall content of phenols and with the change in the molecular weight of the heavy fractions that include lignin oligomers.
The pyrolytic aqueous phase attained from biomass fast pyrolysis used as substrate to generate bioproducts by microorganisms contains phenol inhibitors which must be removed. Ozonation turned out to be an efficient method for their reduction during which the dark color of samples diminished as a function of ozonation time. Thus, color changes were associated with the reduction of phenols.
El trabajo se centra en mostrar los resultados de un estudio, que con la aplicación de los métodos histórico-lógico y empíricos, refleja la necesidad del perfeccionamiento y la implementación ...adecuada de la formación humanista, en particular en el nivel superior y dentro de él atendiendo a las carreras de ciencias médicas, teniendo como momento constitutivo, condición y base, el pensamiento filosófico educativo y socio educativo y su correcta interpretación para una formación ética, como garantía para la comprensión de la misma desde la perspectiva de la propia cultura humanista, que apunta al conocimiento del pensamiento filosófico y socio educativo asociado a una tradición cultural autóctona que aporta la herramienta de lo identitario, como recurso esencial, sobre estos presupuestos, se cumple con el objetivo de ofrecer una fundamentación sobre la conexión esencial y biunívoca existente entre en el papel insustituible que la filosofía de la educación y la sociología de la educación deben desempeñar en el sistema y la formación humanista del individuo en tanto componente de una formación integral y como resultado se aportan las bases conceptuales acerca de cómo entender a la propia formación humanista, qué aporta ella a la formación de este futuro profesional, es novedoso en tanto permite entender cómo abordar desde estos referentes, el vínculo de manera natural a las problemáticas profesionales, sociales e individuales de quienes se forman en el referido contexto.
This paper addresses the most important features of health economics, especially its scope and applications within the sphere of health. Health economics is a field of study which allows countries to ...gear their health policies toward making more rational use of their resources and expanding and improving their health care services. Such policies should, on the other hand, aim to generate strategies for adequately managing human, technical, economic, and financial resources so as to reap the finest health benefits possible. A knowledge of how economics can be applied to health will enable health professionals to introduce an economics culture into their daily work. In other words, it will allow them to keep in mind the scope of their various working tools--health planning, national health accounts and accounting, and economic assessment methods, which include health and pharmaceutical technology assessment and pharmacoeconomics--as well as the place that economics has in health research. Hopefully, a knowledge of these aspects of economic analysis will provide decision-makers with one more tool they can apply in selecting more efficient options and attaining the highest health benefits at the lowest possible cost for the national health system.
El trabajo se centra en mostrar los resultados de un estudio, que con la aplicación de los métodos histórico-lógico y empíricos, refleja la necesidad del perfeccionamiento y la implementación ...adecuada de la formación humanista, en particular en el nivel superior y dentro de él atendiendo a las carreras de ciencias médicas, teniendo como momento constitutivo, condición y base, el pensamiento filosófico educativo y socio educativo y su correcta interpretación para una formación ética, como garantía para la comprensión de la misma desde la perspectiva de la propia cultura humanista, que apunta al conocimiento del pensamiento filosófico y socio educativo asociado a una tradición cultural autóctona que aporta la herramienta de lo identitario, como recurso esencial, sobre estos presupuestos, se cumple con el objetivo de ofrecer una fundamentación sobre la conexión esencial y biunívoca existente entre en el papel insustituible que la filosofía de la educación y la sociología de la educación deben desempeñar en el sistema y la formación humanista del individuo en tanto componente de una formación integral y como resultado se aportan las bases conceptuales acerca de cómo entender a la propia formación humanista, qué aporta ella a la formación de este futuro profesional, es novedoso en tanto permite entender cómo abordar desde estos referentes, el vínculo de manera natural a las problemáticas profesionales, sociales e individuales de quienes se forman en el referido contexto.This research paper shows the results of a study carried out with the application of the historical-logical and empiric methods where the need of improving and implementing an adequate humanistic training in higher education was reflected; mainly for medical science students which formation is supported on a philosophical-educational and social-educational thinking. The humanistic training is an essential concept to the comprehensive formation of the individual and how to understand the proper humanistic formation of the future health professionals establishing conceptual bases. This novel conceptualization allowed tackling these referents, linking it naturally in order to approach professional, social and individual problems to the context where the professional training takes part.
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