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Search Results: 1 - 10 of 474006 matches for " Marco A Cremasco "
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Pérdida de Ozono en Líneas de Flujo Poliméricas: PVC y Silicona Ozone Loss in Polymer Flow Lines: PVC and Silicone
Marco A Cremasco,Edson Tomaz,Vanessa T Mochi,Carlos F Vergel
Información Tecnológica , 2013,
Abstract: El objetivo del presente estudio fue evaluar la interacción entre el ozono y el material de la tubería usada para su transporte, usualmente polimérica, a fin de determinar las pérdidas de ozono durante el proceso. Para este propósito, una mezcla gaseosa de ozono-oxígeno se hizo fluir a través de dos tipos de tubería, PVC y silicona, desde el generador de ozono hasta el punto de recolección. La concentración de ozono en la mezcla gaseosa y el flujo volumétrico de la corriente gaseosa fueron variadas para cada experimento. El flujo másico de ozono fue medido en el punto de recolección, aplicando el método yodométrico por titulación indirecta. La pérdida de ozono fue observada en ambas tuberías. Estas pérdidas están asociadas a la reacción química entre el ozono y el material de la tubería, como también a la auto descomposición del ozono. The aim of this present study was to evaluate the interaction between the ozone and the pipe material used for transporting it, usually of polymeric material, to then determine ozone loss during the process. For this purpose, a mixture of ozone-oxygen was transported through two types of pipes, PVC and silicone, from the ozone generator to the point of collection. The ozone concentration in the gas mixture and volumetric flow of the gas stream were varied for each experiment. The ozone mass flow was measured at the point of collection, applying the iodometric method by indirect titration. Ozone loss was observed in both pipes. These losses are associated with the chemical reaction between ozone and the pipe material, as well as to the ozone self-decomposition.
Isomeriza??o do óleo essencial de pimenta-longa (Piper hispidinervium C. DC) para a obten??o de isosafrol
Cremasco, Marco Aurelio;Braga, Nazareno de Pina;
Acta Amazonica , 2010, DOI: 10.1590/S0044-59672010000400014
Abstract: the brazilian peppers present proprieties that can be used in fragrance and pharmaceutical industries, for example. one these pepper is long pepper (piper hispidinervium c. dc.), who its essential oil is rich in safrole. safrole is an important compound with application in several industries, such as pharmaceutics, cosmetics. after its chemical conversion, for example, it is possible to obtain heliotropin, a fixative agent for fragrances. the sequence to obtain the heliotropin is by safrole isomerization, that, initially, produce isosafrole. in this work, however, presents the synthesis of isosafrole directly from essential oil of piper hispidinervium c. dc. in this case, the isomerization of essential oil was done getting 79,4 % of cis, trans-isosafrole mixture. the essential oil presented 86,4 % of safrole, resulting in 97,1 % yield to cis, trans-isosafrole.
Análise termogravimétrica do óleo essencial de pimenta longa (Piper hispidinervium C. DC)
Cremasco, Marco Aurelio;Nazareno, Braga Pina;
Acta Amazonica , 2011, DOI: 10.1590/S0044-59672011000200012
Abstract: long pepper (piper hispidinervium c. dc.) is a shrub found in the amazon region, which supplies an essential oil rich in safrole. normally, long pepper essential oil is commercialized in natura, which makes its processing a fundamental step in scientific and technological investigation. an important step of safrole commercialization is the separation of essential oil by, for example, a distillation process. in such a case it is important to know some thermodynamics parameters, such as energy of activation and enthalpy of vaporization. the present study was aimed at applying the kinetic of zero order evaporation process for the essential oil of p. hispidinervum by thermogravimetric analysis. the thermal analysis data were utilized to determine the energy of activation and enthalpy of vaporization, which resulted in the values 41.11 kj.mol-1 and 43.73 kj.mol-1, respectively.
Modeling for Taxol? Separation in a simulated moving bed
Cremasco, Marco Aurelio;Starqui, Axel Nicolas;
Brazilian Archives of Biology and Technology , 2010, DOI: 10.1590/S1516-89132010000600020
Abstract: this work presents an alternative numerical resolution strategy for a model to describe the dynamic of linear adsorption processes involving multicomponent mixture of taxanes with taxol? (paclitaxel), a powerful anti-cancer agent, and non-identified impurities, in a simulated moving bed (smb) system. to solve the model, a hybrid method were used. the liquid concentration inside the particles was found analytically and was related with the liquid bed concentration using duhamel's theorem. the results from simulation were compared with experimental ones from the literature, showing a good agreement, which demonstrated the applicability of the model and of the hybrid resolution proposed.
Hybrid method of solution applied to simulation of pulse chromatography
Cremasco, M. A.;Starquit, A. N.;
Brazilian Journal of Chemical Engineering , 2009, DOI: 10.1590/S0104-66322009000200017
Abstract: in this communication, the method proposed by cremasco et al. (2003) is applied to predict single and low concentration pulse chromatography. in previous work, a general rate model was presented to describe the breakthrough curve, where a hybrid solution was proposed for the linear adsorption. the liquid phase concentration inside the particle was found analytically and related with the bed liquid phase through duhamel's theorem, while the bulk-phase equation was solved by a numerical method. in this paper, this method is applied to describe pulse chromatography of solutes that present linear adsorption isotherms. the simulated results of pulse chromatography are compared with experimental ones for aromatic amino acid experiments from literature.
Síntese do piperonal a partir do óleo essencial de pimenta longa (Piper hispidinervium C. DC.)
Cremasco, Marco Aurélio;Braga, Nazareno de Pina;
Acta Amazonica , 2012, DOI: 10.1590/S0044-59672012000200014
Abstract: the essential oil of long-pepper (piper hispidinervum c. dc) is rich in safrole, then susceptible to isomerization reaction to obtain cis, trans-isosafrole. in this paper it is presented the eletroxidation of cis, trans-isosafrole from direct isomerization of essential oil of long-pepper, with 99,7% of convertion to isosafrole glicol, that it is react by oxidation to convert 99% into piperonal with 84,9% purity.
Performance of mechanically shaken indirect contact atmospheric dryer in drying pastelike materials
Melo, K. P.;Cremasco, M. A.;
Brazilian Journal of Chemical Engineering , 2004, DOI: 10.1590/S0104-66322004000300013
Abstract: pastelike materials are encountered in many technological processes in chemical, pharmaceutical, foodstuff and natural product industries. the most important factor in the drying of this type of materials is the nature of the moisture bonding that occurs. because of the different characteristics of pastes, it is impossible to recommend a universal type of dryer for all of these materials. some of the dryers available provide only indirect contact with the drying agent (heat) and also maintain constant moisture with a system of rotating paddles. we evaluated the performance of this type by studying the dryer kinetics curves for ground coffee under a variety of operational conditions of moisture load of material, temperature of the heating plate, intensity of the mechanical mixing of the moisture material, and initial moisture. the effects of these parameters (except for moisture) were studied using a 23 factorial design. according the analyses of the kinetics drying curves, was observed that the increase in the temperature of the plate and rotation as well as the decrease in the load facilitates more effective removal of moisture. in statistical analysis was determined that the load of the material and the heating plate temperature influence the final moisture content of the material and plate temperature modifies the final temperature of the solid. also, was suggested linear models from the factorial design to describe the process of drying coffee grounds satisfactorily.
Performance of mechanically shaken indirect contact atmospheric dryer in drying pastelike materials
Melo K. P.,Cremasco M. A.
Brazilian Journal of Chemical Engineering , 2004,
Abstract: Pastelike materials are encountered in many technological processes in chemical, pharmaceutical, foodstuff and natural product industries. The most important factor in the drying of this type of materials is the nature of the moisture bonding that occurs. Because of the different characteristics of pastes, it is impossible to recommend a universal type of dryer for all of these materials. Some of the dryers available provide only indirect contact with the drying agent (heat) and also maintain constant moisture with a system of rotating paddles. We evaluated the performance of this type by studying the dryer kinetics curves for ground coffee under a variety of operational conditions of moisture load of material, temperature of the heating plate, intensity of the mechanical mixing of the moisture material, and initial moisture. The effects of these parameters (except for moisture) were studied using a 23 factorial design. According the analyses of the kinetics drying curves, was observed that the increase in the temperature of the plate and rotation as well as the decrease in the load facilitates more effective removal of moisture. In statistical analysis was determined that the load of the material and the heating plate temperature influence the final moisture content of the material and plate temperature modifies the final temperature of the solid. Also, was suggested linear models from the factorial design to describe the process of drying coffee grounds satisfactorily.
Separation of l-tryptophan present in an aromatic amino acids mixture in a four-column simulated moving bed: experimental and simulation studies
Cremasco, M. A.;Starquit, A.;Wang, N.-H. L.;
Brazilian Journal of Chemical Engineering , 2009, DOI: 10.1590/S0104-66322009000300016
Abstract: an experimental and theoretical study is presented for the fractionation of l-tryptophan (trp) from l-phenylalanine (phe) and l-tyrosine (tyr). a simulated-moving bed (smb) with four-column system was tested, and the results are presented as effluent histories of the raffinate and extract ports. l-phenylalanine and l-tyrosine were recovered as major products in the raffinate, while l-tryptophan was recovered at the extract. to simulate the l-tryptophan separation, a general rate model was used to represent the mass transfer phenomena that occur in each individual column of the smb, for each solute present in the multicomponent system. a hybrid method was used to solve the model. an analytic solution was used for the intra-particle concentration, and was correlated to the liquid bed concentration by duhamel's theorem. the results from simulation are compared with the experimental data presented in this work.
A design and study of the effects of selectivity on binary separation in a four-zone simulated moving bed for systems with linear isotherms
Cremasco, M.A.;Wang, N.-H. Linda;
Brazilian Journal of Chemical Engineering , 2003, DOI: 10.1590/S0104-66322003000200012
Abstract: the simulated moving bed (smb) is potentially an economical method for the separation and purification of natural products because it is a continuous processes and can achieve higher productivity, higher product recovery, and higher purity than batch chromatographic processes. despite the advantages of smb, one of the challenges is to specify its zone flow rates and switching time. in this case it is possible to use the standing wave analysis. in this method, in a binary system, when certain concentration waves are confined to specific zones, high product purity and yield can be assured. appropriate zone flow rates, zone lengths and step time are chosen to achieve standing waves. in this study the effects of selectivity on yield, throughput, solvent consumption, port switching time, and product purity for a binary system are analyzed. the results show that for a given selectivity the maximum throughput decreases with increasing yield, while solvent consumption and port switching time increase with increasing yield. to achieve the same purity and yield, a system with higher selectivity has a higher throughput and lower solvent consumption.
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