Vera L. P. Soares

TG characterization of organically modified montmorillonite

Montmorillonite was modified with octadecyltrimethylammonium chloride, under different reaction conditions, as evidenced by TG and XRD. TG curves presented two degradation peaks (295 and 395°C). At low salt concentrations, only the 395°C-degradation appeared, which increased with reaction time to the limit of 9 g of salt/100 g of clay. The second peak presented a limit at 17/100 m/m of salt/clay ratio. XRD analysis confirmed clay organic modification as the basal distance increased, showing greater reaction time effect than the salt mass effect, and with only one d-spacing. This suggested that an intercalation complex was formed but also that octadecyltrimethylammonium was adsorbed on the external surfaces of clay particles.

New Applications for Soybean Biodiesel Glycerol

Glycerol (Fig. 1.1) is a viscous and polar substance that has long been known for its useful properties. As long ago as 1779, the Swedish scientist Karl Wilhelm Scheelle obtained glycerol from olive oil. In 1813, Michael E. Chevreul showed that glycerol was involved in the triglyceride structure, and called it glycerin, from the greek word that means sweet. The elucidation of its structure as a trihydroxylated alcohol was due to Wurtz in 1855. The name glycerin was changed to glycerol to indicate its alcohol nature. It is now common to refer to the pure chemical product as glycerol and refer to the commercial grades with varying glycerol content as glycerin (or glycerine). The first example of a chemical industrial application of glycerol is nitroglycerin which was synthesized by Ascanio Sobrero. In 1860 it was transformed into a safer and more convenient form of use by Alfred Nobel [Jerome et al, 2008; Shreve & Brink, 1977; Kirk & Otmer, 1951].

Desenvolvimento de Surfatantes para Aplicação na Indústria de Explosivos

A comercializacao dos explosivos emulsionaveis, ai incluida a dinamite de ANFO, acarretou um aumento significativo no consumo mundial de explosivos entre 1960 e 1980, consequencia da maior seguranca no transporte e no preparo dos explosivos na forma de uma emulsao. Os surfatantes utilizados nestas emulsoes sao esteres, amidas ou imidas derivadas do poliisobutileno com terminacoes de anidrido succinico (PIBSA). Neste trabalho, surfatantes derivados da reacao do PIBSA com polioxietilenodiaminas foram sintetizados e caracterizados pelas tecnicas de espectrometria no infravermelho e de cromatografia de exclusao de tamanho. Os surfatantes sintetizados foram avaliados quanto ao efeito das suas estruturas na reducao da tensao interfacial do sistema agua em oleo e todos foram capazes de reduzir a tensao interfacial deste sistema.

Supercooling measurement in W, Ta, Nb and Re liquid metals by stereophotocalorimetric method

The technique of crystal growth coupled with a stereophotocalorimetric method has been used in a series of supercooling measurements on pure refractory metals. The cooling history of these metals is recorded on photographic films which are calibrated as a function of the temperature. High absolute amounts of supercooling has been observed in W, Ta, Nb and Re liquid droplets. It is noted that the brightness traces of the solidification process for highly supercooled Re droplets evidence of two successive phase transformations (Re cfc to Re hc) shows.