Aprimoramento da representação das forças de dispersão na equação de estado COSMO-SAC-Phi

Neste trabalho, a equação de estado COSMO-SAC-Phi foi refinada através da modificação da expressão que descreve a contribuição energética referente às forças de dispersão. A modificação sugerida é inspirada em funções α(T), utilizadas no termo atrativo de equações de estado cúbicas. Regras de consistência termodinâmica são normalmente aplicadas a funções α(T), e a nova expressão obedece a esses requisitos. Foram apresentadas correlações a dados experimentais de pressão de saturação e volume de líquido saturado de trinta e oito compostos representativos utilizando o modelo original (CSP (2019)) e o modificado (CSP (2021)). Os resultados mostraram que a modificação proposta é capaz de melhorar as correlações significativamente, em que os desvios médios obtidos em relação aos dados experimentais foram de 0,96% para a pressão e 0,73% para o volume. Esses valores representam, respectivamente, reduções de 20% e 64% em relação ao modelo original. As massas específicas de compostos puros sob condições supercríticas também foram adequadamente preditas, com desvios de 3,18%, 4,77% e 7,83%, respectivamente, para os modelos CSP (2021), CSP (2019) e SRK. O desempenho da equação CSP (2021) foi avaliado por meio de predições de equilíbrio líquido-vapor (ELV) de misturas binárias e, na maioria dos sistemas testados, CSP (2021) foi superior aos modelos CSP (2019), PSRK e SRK com a regra de mistura clássica de van der Waals (SRK+vdW). O modelo CSP (2021) também aprimorou a descrição de ELV em condições extrapoladas de temperatura. Predições de equilíbrio líquido-líquido (ELL) de misturas binárias mostraram que a equação CSP (2021) produz resultados similares ao modelo UNIFAC-LLE em temperaturas baixas, além de apresentar um desempenho superior à CSP (2019) em altas temperaturas e pressões. Concluiu-se que a equação de estado CSP (2021) é um modelo com caráter altamente preditivo. Para os sistemas testados, ela é capaz de representar propriedades em altas pressões e descrever forças dispersivas mais apropriadamente que a versão original.In this work, the COSMO-SAC-Phi equation of state was refined by the modification of the expression that describes the energetic contribution from dispersion effects. This modification was inspired by α(T)-functions used in the attractive term of cubic equations of state. Rules of thermodynamic consistency are commonly applied to α(T)-functions, and the new expression follows such requirements. For thirty-eight representative compounds, correlations of pure compound experimental data of saturation pressure and saturated liquid volume were shown, performed by both previous (CSP (2019)) and modified (CSP (2021)) models. The results reveal that the modification is able to improve the correlations significantly, as the average deviations were 0.96% in pressure and 0.73% in volume. These values represent reductions of 20% and 64% when compared to the previous model, respectively. The values of density of pure compounds under supercritical conditions were also predicted properly, with deviations of 3.18%, 4.77% and 7.83% for CSP (2021), CSP (2019) and SRK, respectively. The performance of CSP (2021) was evaluated by vapor-liquid equilibrium (VLE) predictions of binary mixtures. In general, CSP (2021) was better than CSP (2019), PSRK and SRK with the classical van der Waals mixing rule (SRK+vdW). The description of VLE under extrapolated temperature conditions was also improved by CSP (2021). Liquid-liquid equilibrium (LLE) predictions of binary mixtures showed that CSP (2021) gives similar results to UNIFAC-LLE at low temperatures and exhibits better performance than CSP (2019) at higher temperatures and pressures. It can be concluded that CSP (2021) equation of state has a highly predictive feature. For the systems tested, it represents properties at high pressures, besides being able to describe dispersion forces better than the previous version

Effect of concentrations of plasticizers on the sol-gel properties developed from alkoxides precursors

Coatings developed through sol-gel method is presented as an interesting replacement to chromium coating. Sol-gel method present advantages as high purity and excellent distribution of the components. The objective of this work is to synthesize and characterize a film obtained by sol-gel route. The film was prepared with 3-(trimethoxysilylpropyl) methacrylate (TMSPMA), tetraethoxysilane (TEOS) and cerium nitrate, using water and ethanol as solvents. Polyethyleneglycol (PEG) plasticizer was added at four different concentrations. The sol was characterized by techniques of viscosity, thermogravimetric analysis (TGA), X-ray diffraction (XRD) nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The results showed that tetrafunctional alkoxides condensation was retarded by the plasticizer, forming a compact film. The film with 20 g.L-1 of PEG showed the best electrochemical behavior

Effect of concentrations of plasticizers on the sol-gel properties developed from alkoxides precursors

Abstract Coatings developed through sol-gel method is presented as an interesting replacement to chromium coating. Sol-gel method present advantages as high purity and excellent distribution of the components. The objective of this work is to synthesize and characterize a film obtained by sol-gel route. The film was prepared with 3-(trimethoxysilylpropyl) methacrylate (TMSPMA), tetraethoxysilane (TEOS) and cerium nitrate, using water and ethanol as solvents. Polyethyleneglycol (PEG) plasticizer was added at four different concentrations. The sol was characterized by techniques of viscosity, thermogravimetric analysis (TGA), X-ray diffraction (XRD) nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The results showed that tetrafunctional alkoxides condensation was retarded by the plasticizer, forming a compact film. The film with 20 g.L-1 of PEG showed the best electrochemical behavior