Abstract Radio frequency heating (RFH) provides higher efficiency and more uniform heating zone compared with conventional method. The aim of present work is to evaluate the effect of RFH (at 90 °C for 5 or 10 min) on the changes in composition (protein oxidation and fat distribution), microstructure, flow characteristic and rehydration property of infant milk powder. The results indicate that the concentration of protein dityrosine was slightly enhanced, more free fat appeared on powder surfaces (> 50% increase), and porosity in powder matrix as tested by SEM was increased after RFH treatment. For powder flowability, raw sample had low cohesiveness (specific energy = 4.39 mJ/g), and RFH provided better flowability and decreased compressibility. Moreover, RFH had some negative impacts on wettability and solubility of powder particles with contact angle increase at least 5% and solubility decrease of 2%~4%, indicating worse rehydration abilities. Guggenheim-Anderson-de Boer (GAB) model was applied to fit moisture vapor sorption isotherms, and longer RFH duration leading to higher c values (about 63% increase at 10 min). In addition, the RFH initiated browning reaction as CIE a* values increased from -1.8 to -1.3.

Abstract Shape-selective methylation of naphthalene over SAPO-11, SAPO-5 and mordenite molecular sieves were carried out in a fixed-bed flow reactor under atmospheric pressure. Methanol and mesitylene were used as methylation and solvent agents. The experiment results showed that SAPO-11 exhibited higher stability, higher selectivity of 2,6-dimethylnaphthalene (2,6-DMN) and higher 2,6-/2,7-DMN ratio than SAPO-5 and mordenite molecular sieves. The catalytic performances for the methylation of naphthalene were mainly related to the pore structure of the catalysts. The comparison of the spent SAPO- 11 with fresh SAPO-11 suggested that structure collapse of the SAPO-11 by dealumination was occurred during the methylation of naphthalene with methanol, which may have been caused by high temperature steam from water produced in the reaction or by high temperature methanol vapor.

Uma série de catalisadores sólidos básicos de KF/γ-Al2O3foi preparada pelo método deimpregnação úmida e aplicada à síntese de carbonato de glicerina (GC) a partir de glicerol e carbonato de dimetila. As influências do teor de KF e da temperatura de calcinação do catalisador na síntese foram investigadas. Os resultados mostraram que os catalisadores de KF/γ-Al2O3conseguem promover uma conversão eficiente de glicerol emGC. A estrutura e as propriedades dos catalisadores foram estudadas por difratometria de raios X (XRD), espectroscopia no infravermelho por transformada de Fourier (FTIR), adsorção de N2, dessorção térmica programada (TPD) de CO2, espectroscopia fotoeletrônica por raios X (XPS) e pelo método dos indicadores de Hammett. Observou-se que os catalisadores possuem vários tipos de centros básicos, como KF, KAlO2, KOH e possivelmente o íon F-coordenativamenteinsaturado. Os centros fortemente básicos não somente poderiam acelerar a conversão do glicerol, como também aumentar a formação do glicidol a partir da decomposição de GC. A reutilização de KF/γ-Al2O3 mostrou que a decomposição do catalisador, que é causada principalmente pela lixiviação parcial das espécies ativas de potássio, aumenta com o número de usos. Temperaturas altas de calcinação favorecem a transformação de KF emKAlO2e amenizam a desativação do catalisador. Com base na distribuição dos produtos e nos resultados obtidos, foi proposto um mecanismo possível para a reação do glicerol com carbonato de dimetila.

A series of KF/γ-Al2O3 solid base catalysts were prepared by a wet impregnation method and applied to the synthesis of glycerol carbonate (GC) from glycerol and dimethyl carbonate. The influences of KF loading and calcination temperature of catalyst on the synthesis were investigated. The results showed that KF/γ-Al2O3 catalysts could promote glycerol conversion to GC efficiently. The structure and properties of the catalysts were studied by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N2-adsorption, CO2-temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and Hammett indicator method. It was found that several types of basic centers such as KF, KAlO2, KOH and possibly coordinately unsaturated F- ion existed on the catalysts. The strong basic centers could not only accelerate the conversion of glycerol, but also enhance the formation of glycidol from the decomposition of GC. The recycling of KF/γ-Al2O3 revealed that deactivation of catalyst was strengthened with the reuse times, which was mainly caused by the partial leaching of active potassium species. High calcination temperature favored the transformation of KF to KAlO2 and alleviated the deactivation of the catalyst. Based on the product distribution and obtained results, a possible reaction mechanism on reaction of glycerol with dimethyl carbonate was proposed.