Abstract Given the potential of acid-activated clays in adsorptive and catalytic processes, several studies focusing on acid matrices have grown over the years, making it possible to study vermiculite, a mineral composed of a type 2:1 unit cell with tetrahedral and octahedral sheets. Therefore, this work aimed to study vermiculite treated with acids for the production of matrices. In this work, the treatment of natural vermiculite-hydrobiotite, with nitric acid in concentrations of 0.25, 0.50, 0.75, and 1 mol.L-1, followed by the dealumination process with sulfuric acid 25% v/v, aiming the production of acid matrices for applications as support for biocatalysts, chemical adsorbents, among others. The produced materials were characterized using different techniques, including X-ray fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and isotherm adsorption using the BET method. The results showed that after acid leaching the vermiculite showed a high SiO2 content, high Brønsted and Lewis surface acidity, good adsorption/desorption performance, and significant growth of the specific surface area, qualifying the vermiculite as a promising material for future applications in catalytic and biocatalytic processes. The acid concentration had a considerable influence on the compositional and textural modification of vermiculite-hydrobiotite.

ABSTRACT A semi-batch bubble reactor has been developed to produce fatty acid ethyl ester (biodiesel) by acid-catalyzed esterification of oleic acid with superheated ethanol vapor. In this paper, the effects of reaction temperature (110, 130 and 150°C), ethanol volumetric flow rate (1.35, 2.50 and 3.65 mL/min) and vapor bubble size on the reactor performance were evaluated. The results demonstrated that temperature and volumetric flow rate have significant effects on the chemical reaction, gas phase solubility and mass transfer limitations. In addition, the free fatty acid conversion velocity was increased by approximately 56% when a microporous stainless-steel tube was employed to generate and distribute the vapor bubbles inside the reactor, which allowed the process to reach 95% conversion in approximately 40 minutes for the operating temperature of 150°C and volumetric flow rate of 2.5 mL/min.

Foram coletadas 200 folhas recem maduras de meia altura (H = 11 m) da copa das espécies E. graandis, E. microcorys, E. saligna de sete anos de idade, localizadas em solo latossolo, na região de Mogi Guaçu e Areia Branca, SP. As folhas foram analisadas para N, P, K, Ca, Mg, S, B, Cu, Fe, Mn e Zn com os objetivos de detectar exigências nutricionais distintas para as espécies, assim como correlacionar o teor dos nutrientes com o volume cilíndrico de madeira (m³/ha). Constatou-se diferenças significativas na composição química entre as espécies. A espécie E. granais apresenta um teor mais elevado em N, P, K e S. As concentrações mais baixas dos nutrientes são encontradas no E. microcorys. Foram constatadas diferenças significativas entre os locais nas espécies com exceção de Mg, B, Cu, Fe e Zn. Teores elevados em Mn foram constatados nas folhas de todas as espécies. O eucalipto de maior produção é o E. grandis, sendo o E. microcorys o de menor produção. Foi constatada correlação positiva entre N, P, K, S e Fe nas folhas e produção cilíndrica de madeira.

Two hundred recent mature leaves were collected, at april 1976, from each of the upper crown part of to years old plants (E. grandis, E. microcorys, E. resinifera, E.robusta, E. saligna), established on two Red Yellow Latossol site at Mogi Guaçu and Areia Branca, State of São Paulo, Brasil. Chemical analysis were run for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn in order to detect nutritional differences between the species. The highest concentration of N, P, K and S were founded in E. grandis; while E. microcorys exhibited the lowest concentrations in nutrients. High eleveis in Mn were observed in all species due the acid soils. The yields in (m³/ha.) of wood have varied considerably within the species. The higher production of wood was of the species E. grandis and the lower was due E. microcorys. A positive correlation were observed between nutrient concentration (x) and yield of wood (y) for the elements and is expressed by the following equations: Ny = 261.45 x - 158.51 r = 0.60** Py = 4.476.80 x - 126.24 r = 0.60** Ky = 715.27 x- 1.76 r = 0.58** Sy = 1.431.74 x - 2.13 r = 0.51** Fe y = 2.773.2 x+ 48.63 r = 0.34*