Impact of gamma-irradiation on some mass transfer driven operations in food processing

The effect of gamma-irradiation pretreatment on some mass transfer driven operations such as dehydration, osmotic dehydration and rehydration, commonly used in food processing, was studied. Applied irradiation up to 12.0 kGy resulted in decrease in hardness of the samples, as indicated by texture analysis. The effective diffusion coefficients of water and solute determined for dehydration, osmotic dehydration as well as for rehydration using a Fickian diffusion model. The effective diffusion coefficients for water (in case of osmotic dehydration and dehydration) and solid diffusion (in case of osmotic dehydration) were found to increase exponentially with doses of gamma-irradiation (G) according to an equation of the form D=A exp(−B/G), where A and B are constants. Microstructures of irradiated-carrot samples revealed that the exposure of carrot to gamma irradiation resulted in the breakage of cell wall structure, thereby causing softening of irradiated samples and facilitating mass transfer during dehydration and osmotic dehydration. The rehydration characteristics showed that gamma-irradiated sample did not absorb as much water as control, probably due to loss of cell integrity.     

Thermal decomposition of potassium tetraborate tetrahydrate to anhydrous potassium tetraborate in a fluidized bed

Production of anhydrous potassium tetraborate from potassium tetraborate tetrahydrate (PTT) was investigated in a controlled fluidized bed calcinatory (FBC). Single step calcination gives a puffed product with very low bulk density and the calcination of potassium tetraborate tetrahydrate is incomplete since agglomeration starts at temperature higher than 250 °C. Effect of the temperature on the bulk density of the product obtained at the end of single step is given and compared with theoretical calculation. In order to obtain anhydrous potassium tetraborate, dehydration should be carried out at least two stages. The most important step dominating the final bulk density is the first step. Dehydration of potassium tetraborate tetrahydrate up to 85% K₂B₄O₇ content and temperature lower than 150 °C in the first step gives commercial available product at final stage. As a result, both puffed and denser anhydrous potassium tetraborate of 99.5% purity with bulk density around 0.4 and 0.7 g cm⁻³ has been produced by two and three stage calcinations.     

The role of V4+ ions in vanadium oxide catalysts I. Decomposition of 2-propanol

Decomposition of 2-propanol has been studied on vanadium pentoxide with MoO₃ and WO₃ additives. It has been observed that a small amount of the additives increases the dehydration activity of the catalysts, but at 5% or higher concentration, dehydration of 2-propanol decreases. The initial increase followed by a decrease in the dehydration activity with increased amount of additives is due to the change in the rate-determining step. Addition of MoO₃, WO₃, and alkali metal oxides to vanadium pentoxide has similar effects on the V⁴⁺ concentration and catalytic activity. Based on the results of the kinetic and ESR spectral studies, a scheme for the reaction has been proposed. It is concluded that the concentration of V⁴⁺ ion plays the crucial role in these catalysts. Deceased October 1979     

不同形貌ZrWMoO8粉体的制备、表征及其负热膨胀特性

采用水合前驱物分解的方法, 以钨酸铵、钼酸铵及硝酸氧锆为原料制备了不同形貌的ZrWMoO8粉体. 对其前驱体进行了热重-差热分析(TG-DSC), 并以X射线粉末衍射(XRD)、扫描电子显微镜(SEM)及X射线荧光光谱仪(XRF)等手段考察了不同胶凝剂(HCl, HClO4, HNO3, H2SO4及H3PO4)对产物结构和形貌的影响. 结果表明, 胶凝剂的选择对ZrWMoO8粉体的形貌有较大影响. 在100—700 ℃范围内, 以HCl为胶凝剂制备出来的立方相ZrWMoO8粉体的热膨胀系数为-3.84×10-6 K-1.     

Characterization of dehydration behavior of untreated and pulverized creatine monohydrate powders

Creatine, which is well known as an important substance for muscular activity, is synthesized from amino acids such as glycine, arginine and ornithine in liver and kidney. It then accumulates in skeletal muscle as creatine phosphoric acid. The aim of this study was to understand the dehydration behavior of untreated and pulverized creatine monohydrate at various temperatures. The removal of crystal water was investigated by using differential scanning calorimetry (DSC), X-ray powder diffraction and scanning electron microscopy (SEM). The X-ray diffraction pattern of untreated and pulverized creatine monohydrate agreed with reported data for creatine monohydrate. However, the diffraction peaks of the (1 0 0), (2 0 0) and (3 0 0) planes of pulverized creatine monohydrate were much stronger than those of untreated creatine monohydrate. On the other hand, the diffraction peaks of the (0 1 2) and (0 1 3) planes of untreated creatine monohydrate were much stronger than those of pulverized creatine monohydrate. The dehydration of untreated and pulverized creatine monohydrate was investigated at various storage temperatures, and the results indicated that untreated and pulverized creatine monohydrate were transformed into the anhydrate at more than 30 °C. After dehydration, the particles of untreated and pulverized creatine anhydrate had many cracks. The dehydration kinetics of untreated and pulverized creatine monohydrate were analyzed by the Hancock–Sharp equation on the basis of the isothermal DSC data. The dehydrations of untreated and pulverized creatine monohydrate both followed a zero-order mechanism (Polany–Winger equation). However, the transition rate constant, calculated from the slope of the straight line, was about 2.2–7.7 times higher for pulverized creatine monohydrate than for untreated creatine monohydrate. The Arrhenius plots (natural logarithm of the dehydration rate constant versus the reciprocal of absolute temperature) of the isothermal DSC data for untreated and pulverized creatine monohydrate were linear. The activation energies of dehydration in the 40–60 °C range for untreated and pulverized creatine monohydrate were 15.02 and 10.1 kJ/mol, respectively. Dehydration of untreated creatine monohydrate had a pronounced effect on the particle size of the powder. Compared with pulverized creatine monohydrate, the particle size of untreated creatine monohydrate was significantly decreased by dehydration.     

Low-temperature Heat Capacities and Thermodynamic Properties of Hydrated Sodium Cupric Arsenate [NaCuAsO4·1.5H2O（s）]

Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O(s)were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurred in the temperature range of T=368-374 K.The peak temperature of the dehydration was observed to be TD=(371.828±0.146)K by means of the heat-capacity measurement.The molar enthalpy and entropy of the dehydration were ΔDHm=(18.571±0.142)kJ/mol and ΔDSm=(49.946±0.415)J/(K·mol),respectively.The experimental values of heat capacities for the solid(Ⅰ)and the solid-liquid mixture(Ⅱ)were respectively fitted to two polynomial equations by the least square method.The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.     

Sulfated Alumina Catalysts: Consequences of Sulfate Content and Source

Summary. Consequences of the loading level of sulfate ions (3, 6, and 10-wt%) as well as the source of sulfate (H₂SO₄ or (NH₄)₂SO₄) on the structural, textural, and surface acid–base properties as well as the impacts on catalytic activity towards 2-propanol conversions on γ-Al₂O₃ and on aluminum hydroxide gel is described. Structural investigations of the catalysts by XRD revealed that the sulfation processes do not remarkably affect the γ-phase of alumina irrespective of the sulfate content or source. N₂-adsorption at 77 K indicated that sulfated gel catalysts exhibit the highest S_BET areas and, in general, S_BET for all catalysts were found to decrease with the increase of sulfate content, such a decrease is more pronounced for the 10% loaded catalysts. Pyridine adsorption as followed by FTIR indicated that sulfation of alumina increases the strength of its Lewis acid sites and creates Br?nsted acidity in the case of highly loaded catalysts. The catalytic decomposition of 2-propanol in the gas phase indicated that, amongst all the catalysts investigated, the 6% loaded ones exhibited 100% activity (2-propanol conversion) and the highest propene (dehydration product) selectivity.     

Preparation and pervaporation properties of crosslinked hyperbranched poly(amine-ester) membranes

Crosslinked hyperbranched poly(amine-ester) (HPAE) membranes were prepared by crosslinking its terminal hydroxyl groups with glutaraldehyde (GA). The crosslinked HPAE membranes showed high reactivity and good hydrophilicity. The crosslinking degree was investigated by Fourier transformation infrared spectra (FT-IR). Atom force microscope (AFM) and scanning electron microscope (SEM) reveals that the crosslinked HPAE films have smooth surfaces, dense and homogenous matrices. The swelling degree of the membrane was higher in water than that in isopropanol. From the permeation of pure water through the HPAE membrane, the effect of hydroxyl/aldehyde group ratio on the permeation flux and separation factor was investigated. The results indicated that the permeation flux increase was accompanied with the separation factor decrease if the water concentration increased in the feed solution.     

Nonisothermal Kinetice of Dehydration Process of [Sm(m-CIBA)3phen]2·2H2O and[Sm(p-CIBA)3phen]2·2H2O

Compounds[Sm(m-CIBA)3phen]2·2H2O and[Sm(p-ClBA)3phen]2·2H2O(m-ClBA=m-chlorobenzoate,PClBA=p-chlorobenzoate,phen=1,10-phenanthroline)were prepared.The dehydration processes and kinetics of these compounds were studied from the analysis of the DSC curves using a method of processing the data of thermal analysis kinetics.The Arrhenius equation for the dehydration process can be expressed as lnk=38.65-243.90x103|RT for and△S≠ of dehydration reaction for the title compounds are determined,respectively.     

DBSA mediated chemoselective synthesis of 2-substituted benzimidazoles in aqueous media

An efficient synthetic method has been developed for the facile synthesis of 2-substituted benzimidazoles in organized aqueous media in the presence of a surfactant (viz. DBSA) as catalyst and I₂ as co-catalyst. The method described has the advantages of operational simplicity, excellent yields, high chemoselectivity, and clean and green reaction profile.