Experimental determination and prediction of solid-liquid phase equilibria for binary (N-(2-acetoxyethyl)-p-nitroaniline (1) + N-ethyle-4-nitroaniline (2)) mixture

The nitrocellulose based materials are degraded in a natural way during their storage; the processes of degradation are accelerated when the temperature or the humidity increases. To prevent this decomposition, these materials include in their composition stabilising agents which retain the nitro groups and avoid the auto-catalytic degradation of nitrocellulose. The aim of the present work is to improve our understanding of the basic mechanisms of the degradation of the nitrocellulose based materials and the way in which their stabilization evolves. Solid–liquid phase equilibrium for the binary system of (N-(2-acetoxyethyl)-p-nitroaniline (1) + N-ethyle-4-nitrooaniline (2)) is determined using DSC technique. The experimental results were correlated using Wilson and UNIQUAC models. As results, the system studied presents a simple eutectic, where the components are not miscible in the solid phase. Important deviations between experimental and predicted values are observed in the case of ideal model. These deviations can be attributed to the complexity of our system and principally to the presence of intermolecular effects. The best description of SLE was given by the two parameters UNIQUAC

Experimental determination and prediction of solid-liquid phase equilibria for binary (N-(2-acetoxyethyl)-p-nitroaniline (1) + N-ethyle-4-nitroaniline (2)) mixture

The nitrocellulose based materials are degraded in a natural way during their storage; the processes of degradation are accelerated when the temperature or the humidity increases. To prevent this decomposition, these materials include in their composition stabilising agents which retain the nitro groups and avoid the auto-catalytic degradation of nitrocellulose. The aim of the present work is to improve our understanding of the basic mechanisms of the degradation of the nitrocellulose based materials and the way in which their stabilization evolves. Solid–liquid phase equilibrium for the binary system of (N-(2-acetoxyethyl)-p-nitroaniline (1) + N-ethyle-4-nitrooaniline (2)) is determined using DSC technique. The experimental results were correlated using Wilson and UNIQUAC models. As results, the system studied presents a simple eutectic, where the components are not miscible in the solid phase. Important deviations between experimental and predicted values are observed in the case of ideal model. These deviations can be attributed to the complexity of our system and principally to the presence of intermolecular effects. The best description of SLE was given by the two parameters UNIQUAC

FTIR spectroscopy and X-ray powder diffraction characterization of microcrystalline cellulose obtained from alfa fibers

Many cereal straws have been used as raw materials for the preparation of microcrystalline cellulose (MCC). These raw materials were gradually replaced with wood products; nevertheless about 10% of the world overall pulp production is obtained from non-wood raw material. The main interest in pulp made from straw is that it provides excellent fibres for different industries with special properties, and that it is the major available source of fibrous raw material in some geographical areas. The aim of the present work was to characterize microcrystalline cellulose prepared from alfa fibers using the hydrolysis process. The products obtained are characterized with FTIR spectroscopy and X-ray powder diffraction. As a result, FTIR spectroscopy is an appropriate technique for studying changes occurred by any chemical treatment. The spectrum of alfa grass stems shows the presence of lignin and hemicelluloses. However, the cellulose spectrum indicates that the extraction of lignin and hemicellulose was effective. The X-ray analysis indicates that the microcrystalline cellulose is more crystalline than the source material

FTIR spectroscopy and X-ray powder diffraction characterization of microcrystalline cellulose obtained from alfa fibers

Many cereal straws have been used as raw materials for the preparation of microcrystalline cellulose (MCC). These raw materials were gradually replaced with wood products; nevertheless about 10% of the world overall pulp production is obtained from non-wood raw material. The main interest in pulp made from straw is that it provides excellent fibres for different industries with special properties, and that it is the major available source of fibrous raw material in some geographical areas. The aim of the present work was to characterize microcrystalline cellulose prepared from alfa fibers using the hydrolysis process. The products obtained are characterized with FTIR spectroscopy and X-ray powder diffraction. As a result, FTIR spectroscopy is an appropriate technique for studying changes occurred by any chemical treatment. The spectrum of alfa grass stems shows the presence of lignin and hemicelluloses. However, the cellulose spectrum indicates that the extraction of lignin and hemicellulose was effective. The X-ray analysis indicates that the microcrystalline cellulose is more crystalline than the source material

Optimisation des cycles combinés gaz/vapeur avec un ou deux niveaux de pression et chaudière à surface d'échange imposée

Cet article présente l'optimisation des cycles combinés gaz/vapeur avec des chaudières récupératrices ayant un ou deux niveaux de pression pour la production de vapeur sans resurchauffe. L'objectif est de maximiser la puissance électrique produite, avec limitation de la surface totale de transfert de chaleur de la chaudière de récupération. La solution proposée est d'abord thermodynamique, mais elle tient aussi compte des aspects économiques par la diminution indirecte du coût. Les turbines à gaz étant choisies parmi les modèles extraits des catalogues industriels, l'objectif devient celui de maximiser la puissance électrique générée par la turbine à vapeur. Le modèle mathématique présenté couvre l'ensemble des installations du cycle combiné dans leurs couplages et met en évidence la présence d'une pression ou d'une paire de pressions pour lesquelles on obtient l'optimum thermoéconomique. Le travail contient, aussi, une analyse et une optimisation économique de la chaudière de récupération à un niveau de pression, dans les mêmes hypothèses