Navegando por Autor "Treichel, Helen"

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Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method
(ABM, ABC, ABPol, 2013) Bieseki, Lindiane; Bertell, Francine; Treichel, Helen; Penha, Fabio G.; Pergher, Sibele Berenice Castellã
Montmorillonite clays are of great interest for industrial processes such as catalysis and adsorption. The textural properties of clays can be modified in an attempt to increase their uses. This paper describes the acid treatment of natural montmorillonite clay. The materials were characterized using X-ray diffraction (XRD), atomic absorption spectroscopy (AA) and BET surface area measurements. Three different acids (HCl, HNO3 and H2SO4) were tested, and HCl and H2SO4 were more efficient for removing Fe from the clay. The results indicate that HCl better preserves the material structure because less Al is removed. A central composite design (CCD) 22 was applied to evaluate the treatment using HCl. The temperature and concentration presented positive effects on the removal of Fe, Al and Mg. Combinations of the HCl acid solution concentration and temperature, such as 4 mol.L-1/50 °C and 1 mol.L-1/75 °C, assured that Fe was removed with less damage to the structure.
Assessment of two immobilized lipases activity and stability to low temperatures in organic solvents under ultrasound-assisted irradiation
(Springer, 2012-03) Batistella, Luciane; Ustra, Mara K.; Richetti, Aline; Pergher, Sibele Berenice Castellã; Treichel, Helen; Oliveira, J. V.; Lerin, Lindomar; Oliveira, Débora de
Both stability and catalytic activity of two commercial immobilized lipases were investigated in the presence of different organic solvents in ultrasound-assisted system. In a general way, for Novozym 435, the use of ethanol as solvent led to a loss of activity of 35% after 10 h of contact. The use of iso-octane conducted to a gradual increase in lipase activity in relation to the contact time, reaching a maximum value of relative activity of 126%. For Lipozyme RM IM, after 5 h of exposure, the enzyme presented no residual activity when ethanol was used as solvent. The solvents tert-butanol and iso-octane showed an enhancement of about 20 and 17% in the enzyme activity in 6 h of exposure, respectively. Novozym 435 and Lipozyme IM presented high stability to storage after treatment under ultrasound-assisted system using n-hexane and tert-butanol as solvents.
Liquefied petroleum gas as solvent medium for the treatment of immobilized inulinases
(Wiley, 2013-02) Silva, Marceli Fernandes; Golunski, Simone Maria; Rigo, Diane; Mossi, Vinícius; Luccio, Marco Di; Mazutti, Marcio A.; Pergher, Sibele Berenice Castellã; Oliveira, Débora; Oliveira, J. Vladimir; Treichel, Helen
BACKGROUND: The main goal of this work is to assess the influence of pressurized liquefied petroleum gas (LPG) treatment on the enzymatic activity of immobilized inulinases. The effects of process variables were evaluated through 23 experimental design. RESULTS: Inulinase from Klyveromyces marxianus NRRL Y‐7571 presented an increase of 163% in residual activity using LPG at 30 bar during 1 h exposure using a depressurization rate of 20 bar min−1. For Aspergillus niger commercial inulinase, an increment of 129% in residual activity was observed at 30 bar for 1 h treatment at the highest depressurization rate (20 bar min−1). Enzymatic activities changed significantly depending on the enzyme source and the experimental treatment conditions investigated, such as exposure time, depressurization rate and pressure. CONCLUSION: Hence, compressed LPG appears to be a promising technique with practical relevance as a preparation step to improve enzyme activity, thus helping the development of new biotransformation processes. © 2012 Society of Chemical Industry
Natural montmorillonite as support for the immobilization of inulinase from Kluyveromyces marxianus NRRL Y-7571
(Elsevier, 2012-10) Coghetto, Chaline C.; Scherer, Robison P.; Silva, Marceli F.; Golunski, Simone; Pergher, Sibele Berenice Castellã; Oliveira, Débora de; Oliveira, J. Vladimir; Treichel, Helen
The objective of this study was to investigate the process of immobilization of inulinases using natural montmorillonite as inorganic support. The enzyme to buffer ratio of 3:10 and 10 min of immobilization led to the highest specific activity, 375.07 U/mg protein. The immobilized inulinase kept its activity after 1968 h under storage at low temperatures and after 456–1826 h at high temperatures. The pH value of 3.5 led to the highest specific activity. Km values of 1.46 and 0.38 mM, and vmax of 0.2487 and 0.2396 mol/L min, were obtained, respectively, for sucrose and inulin.
Porous materials obtained by acid treatment processing followed by pillaring of montmorillonite clays
(Elsevier, 2013-11) Bieseki, Lindiane; Treichel, Helen; Araujo, Antonio S.; Pergher, Sibele Berenice Castellã
Montmorillonite clay was treated with hydrochloric acid and subsequently pillared with aluminum polyoxocations. The acid-treated samples were evaluated for the removal of structural elements (Al, Fe and Mg) and for conservation of the lamellar organization. The more severe the treatment, the greater the specific area obtained. Despite the loss of structural organization, all samples were pillared, with a displacement of peak (001) to 2θ lower angles. The pillaring of all acid-treated samples promoted an increase in the specific area of these materials. Pillared samples previously treated at 50 °C with HCl concentrations of 2 and 4 mol L− 1 underwent an increase in their specific areas of approximately 45%. Pillared samples treated with 4 mol L− 1 of HCl at 80 °C underwent the lowest percent increase in surface area, approximately 10%, compared to the untreated samples. All samples possessed greater uniformity in pore size. Acid treatment prior to pillaring promoted an increase in the number of acid sites of moderate strength compared to pillared natural clay.
Screening, optimization and kinetics of Jatropha curcas oil transesterification with heterogeneous catalysts
(Elsevier, 2011-02) Zanette, Andréia F.; Barella, Rodrigo Augusto; Pergher, Sibele Berenice Castellã; Treichel, Helen; Oliveira, Débora; Mazutti, Marcio A.; Silva, Edson Antonio; Oliveira, Jose Vladimir
This work investigates the production of fatty acid methyl esters (FAME) from Jatropha curcas oil using a variety of heterogeneous catalysts: resins, zeolites, clays, hydrotalcites, aluminas and niobium oxide. For this purpose, a catalyst screening was first conducted in a batch reactor at the following operating conditions: oil to methanol molar ratio of 1:9, 6 h of reaction, 5 wt% catalyst, at 333 and 393 K. From the screening step, KSF clay and Amberlyst 15 catalysts were selected to carry out a 23 full factorial central composite rotatable design so as to elucidate the effects of process variables on FAME yield. The optimum reaction conditions for both catalysts were found to be oil to methanol molar ratio of 1:12, 5 wt% of catalyst, 433 K and 6 h of reaction with a FAME yield of about 70 wt%. A kinetic study was then experimentally performed and a semi-empirical model was built to represent the experimental data. Finally, catalyst re-utilization in five successive batch experiments was evaluated at the optimized conditions.
Study on the NaOH/metakaolin Ratio and Crystallization Time for Zeolite a Synthesis from Kaolin Using Statistical Design
(ABM, ABC, ABPol, 2017-04-13) Pergher, Sibele Berenice Castellã; Silva Filho, Severino Higino da; Bieseki, Lindiane; Maia, Ana Aurea B.; Treichel, Helen; Angelica, Rômulo Simões
The NaOH/metakaolin ratio and crystallization time were studied for the synthesis of zeolite NaA from a sample of kaolin from a Capim mine. The tests were carried out by using statistical design with axial points and replication of the central point. The samples obtained were characterized by X-ray diffraction (DRX), scanning electron microscopy and chemical analysis using a microprobe EPMA. The results showed that there is a relationship between the amount of NaOH added and crystallization time. The tests carried out using the lowest NaOH/metakaolin ratio (0.5) and the shortest time (4 h) produced a non-crystalline material. On the other hand, increasing the NaOH/metakaolin ratio and the crystallization time led to the formation of a NaA phase with a high structural level, but with the presence of a sodalite phase as an impurity

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Navegando por Autor "Treichel, Helen"