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71.
72.
Carlos Eduardo Barão Leandro Daniel de Paris João Henrique Dantas Matheus Mendonça Pereira Lucio Cardozo Filho Heizir Ferreira de Castro Gisella Maria Zanin Flavio Faria de Moraes Cleide Mara Faria Soares 《Applied biochemistry and biotechnology》2014,172(1):263-274
The use of lipases in industrial processes can result in products with high levels of purity and at the same time reduce pollutant generation and improve both selectivity and yields. In this work, lipase from Thermomyces lanuginosus was immobilized using two different techniques. The first involves the hydrolysis/polycondensation of a silica precursor (tetramethoxysilane (TMOS)) at neutral pH and ambient temperature, and the second one uses tetraethoxysilane (TEOS) as the silica precursor, involving the hydrolysis and polycondensation of the alkoxide in appropriate solvents. After immobilization, the enzymatic preparations were dried using the aerogel and xerogel techniques and then characterized in terms of their hydrolytic activities using a titrimetric method with olive oil and by the formation of 2-phenylethyl acetate in a transesterification reaction. The morphological properties of the materials were characterized using scanning electron microscopy, measurements of the surface area and pore size and volume, thermogravimetric analysis, and exploratory differential calorimetry. The results of the work indicate that the use of different silica precursors (TEOS or TMOS) and different drying techniques (aerogel or xerogel) can significantly affect the properties of the resulting biocatalyst. Drying with supercritical CO2 provided higher enzymatic activities and pore sizes and was therefore preferable to drying, using the xerogel technique. Thermogravimetric analysis and differential scanning calorimetry analyses revealed differences in behavior between the two biocatalyst preparations due to the compounds present. 相似文献
73.
Siqueira Iolanda Scheibe de Dweck Jo Toledo Filho Romildo Dias 《Journal of Thermal Analysis and Calorimetry》2020,142(4):1413-1428
Journal of Thermal Analysis and Calorimetry - The interest in the use of cellulose fibers of increasingly smaller sizes in cementitious materials has increased in recent years. This paper brings... 相似文献
74.
Manoel Raimundo dos Santos Junior Elinia Castro Costa Caio Campos Ferreira Lucas Pinto Bernar Marcilene Paiva da Silva Andria de Andrade Mncio Marcelo Costa Santos Sílvio Alex Pereira da Mota Douglas Alberto Rocha de Castro Sergio Duvoisin Junior Luiz Eduardo Pizarro Borges Marilena Emmi Araújo Nlio Teixeira Machado 《Molecules (Basel, Switzerland)》2022,27(7)
In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na2CO3 as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO2) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO2, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO2 was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17. 相似文献
75.
76.
E. C. da Silva Filho Oberto G. da Silva Maria G. da Fonseca Luiza N. H. Arakaki C. Airoldi 《Journal of Thermal Analysis and Calorimetry》2007,87(3):775-778
A series of compounds with
composition of Ca1–xCuxHPO4,
where x varied from 0.05 to 0.5 were synthesized
by precipitation method. The compounds were characterized by elemental analysis,
X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and
thermogravimetry. The chemical stabilities of solids were investigated at
several pH. Elemental analysis of copper, calcium and phosphorus are in agreement
with the proposed composition. The formation of lamellar phosphates was evidenced.
The stability of the set of compounds was better for samples with high copper
content. 相似文献
77.
Evaluation of tocopherol recovery through simulation of molecular distillation process 总被引:7,自引:0,他引:7
E. B. Moraes C. B. Batistella M. E. Torres Alvarez Rubens Maciel Filho M. R. Wolf Maciel 《Applied biochemistry and biotechnology》2004,114(1-3):689-711
DISMOL simulator was used to determine the best possible operating conditions to guide, in future studies, experimental works.
This simulator needs several physical-chemical properties and often it is very difficult to determine them because of the
complexity of the involved components. Their determinations must be made through correlations and/or predictions, in order
to characterize the system and calculate it. The first try is to have simulation results of a system that later can be validated
with experimental data. To implement, in the simulator, the necessary parameters of complex systems is a difficult task. In
this work, we aimed to determe these properties in order to evaluate the tocopherol (vitamin E) recovery using a DISMOL simulator.
The raw material used was the crude deodorizer distillate of soya oil. With this procedure, it is possible to determine the
best operating conditions for experimental works and to evaluated the process in the separation of new systems, analyzing
the profiles obtained from these simulations for the falling film molecular distillator. 相似文献
78.
C.H.O. Costa P.H.R. Barbosa F.F. Barbosa Filho M.S. Vasconcelos E.L. Albuquerque 《Solid State Communications》2010,150(47-48):2325-2328
In this work we investigate magnonic band gaps, in the terahertz (THz) frequency range, in periodic and quasiperiodic (Fibonacci sequence) magnonic crystals formed by layers of Cobalt (Co) and Permalloy (Py). Our theoretical model is based on a magnetic Heisenberg Hamiltonian in the exchange regime, together with a transfer-matrix treatment within the random-phase approximation (RPA). For periodic arrangements the bulk band structure is analogous to those found in photonic crystals, while for quasiperiodic multilayers it presents additional pass bands similar to those found in doped electronic materials. 相似文献
79.
Annals of Global Analysis and Geometry - This paper studies timelike minimal surfaces in the De Sitter space $$\mathbb S^3_1(1) \subset \mathbb R^4_1$$ via a complex variable. Using complex... 相似文献
80.