Thermal transitions and fat droplet stability in ice-cream mixmodel systems

We studied thermal transitions and physical stability of oil-in-water emulsions containing different milk fat compositions, arising from anhydrous milk fat alone (AMF) or in mixture (2:1 mass ratio) with a high melting temperature (AMF–HMT) or a low melting temperature (AMF–LMT) fraction. Changes in thermal transitions in bulk fat and emulsion samples were monitored by differential scanning calorimetry (DSC) under controlled cooling and reheating cycles performed between 50 and –45°C (5°C min^–1). Comparison between bulk fat samples and emulsions indicated similar values of melting completion temperature, whereas initial temperature of fat crystallization (T_onset) seemed to be differently affected by storage temperature depending on triacylglycerols (TAG) composition. After storage at 4°C, T_onset values were very similar for emulsified and non-emulsified AMF–HMT blend, whereas they were lower (by approx. 6°C) for emulsions containing AMF or mixture of AMF–LMT fraction. After storage at –30°C, T_onset values of re-crystallization were higher in emulsion samples than in bulk fat blends, whatever the TAG fat composition. Light scattering measurements and fluorescence microscopic observations indicated differences in fat droplet aggregation-coalescence under freeze-thaw procedure, depending on emulsion fat composition. It appeared that under quiescent freezing, emulsion containing AMF–LMT fraction was much less resistant to fat droplet aggregation-coalescence than emulsions containing AMF or AMF–HMT fraction. Our results indicated the role of fat droplet liquid-solid content on emulsion stability.     

Flow Maldistribution in Dense- and Sock-Loaded Trilobe Catalyst Trickle-Bed Reactors: Experimental Data and Modeling Using Neural Network

In order to experimentally study the catalyst loading method (dense and sock) influence on liquid distribution, a trickle-bed reactor (TBR) packed with extrudate trilobe catalysts was used. Furthermore, an artificial neural network (ANN) algorithm has been applied; the results show acceptable agreement between the ANN model prediction and experimental data. Due to the isotropic distribution of porosity in sock-loaded bed with trilobe catalysts, the results illustrate that with the same operating conditions the sock-packed beds spread liquid better than dense ones. The effects of bed height and variations of gas/liquid flow rate on liquid distribution in sock- and dense-loaded TBRs have been investigated.     

Nitrogen-doped carbon nanotubes for heat transfer applications

In this research, it is aimed to enhance the heat transfer properties of the carbon nanotubes through nitrogen doping. To this end, nitrogen-doped multiwall carbon nanotubes (N-CNTs) were synthesized via chemical vapor deposition method. For supplying carbon and nitrogen during the synthesis of N-CNTs, camphor and urea were used, respectively, at 1000 °C over Co–Mo/MgO nanocatalyst in a hydrogen atmosphere. N-CNTs with three different nitrogen loadings of 0.56, 0.98, and 1.38 mass% were synthesized, after which, water/N-CNT nanofluids of these three samples with concentrations of 0.1, 0.2, and 0.5 mass% were prepared. To obtain a stable nanofluid, N-CNTs were functionalized by nitric acid followed by stabilizing in water by employing the ultrasonic bath. Investigation on the stability of the samples showed a high stability level for the prepared water/N-CNT nanofluids in which the zeta potential of ??43.5 mV was obtained for the best sample. Also for studying the heat transfer properties, the thermal conductivity in the range of 0.1–0.5 mass% and convection heat transfer coefficients of nanofluids in the range of 0.1–0.5 mass%, and Reynolds number in the range of 4000–9000 were evaluated. The results showed 32.7% enhancement of the convection heat transfer coefficients at Reynolds number of 8676 and 27% increase in the thermal conductivity at 0.5 mass% and 30 °C.

     

A New Practical Route to ZSM‐5 Nanoparticles and Optimization of Synthetic Parameters through D‐optimal Design of Experiments

A D‐optimal experimental design with three levels of SiO₂/Al₂O₃, template/SiO₂, H₂O/SiO₂, Na₂O/SiO₂ and TPABr/TPAOH ratio parameters has been used to optimize the experimental parameters by an analysis of variances (ANOVA). The effects of these ratios in the initial synthetic mixture on the size of the ZSM‐5 zeolite nanoparticles have been studied. XRD and FE‐SEM analyses were used to characterize synthetic samples. Fischer test results showed that H₂O/SiO₂ and TPABr/TPAOH ratios are the most and least effective parameters, respectively, in the range studied. The most important two‐way interaction variables were the interaction of template/SiO₂ and TPABr/TPAOH molar ratios. The average particle size was in the 34–79 nm range. Furthermore, a mathematical model for the synthesis of ZSM‐5 zeolite nanoparticles was derived using experimental results. The optimized gel composition is as follows: SiO₂/Al₂O₃₌91.20, template/SiO₂₌0.16, H₂O/SiO₂₌40.42, Na₂O/SiO₂₌0.0147 and TPABr/TPAOH=0.     

Extrudate Trilobe Catalysts and Loading Effects on Pressure Drop and Dynamic Liquid Holdup in Porous Media of Trickle Bed Reactors

The hydrodynamics of concurrent gas-liquid downflow through a porous media of fixed bed reactor has been studied experimentally in a range of trickling flow rates. A pilot bed is packed with industrial spherical and extrudate trilobe catalysts. The industrial trilobe catalysts are packed in a bed using two different methods: random close or dense packing and random sock packing. The experiments are performed for single phase in the cases of wet and dry packed beds and for two-phase flow conditions. The comparisons of pressure drops as well as liquid holdup are carried out for the above three different porous media, random close, dense packing and random sock packing. It is shown that the pressure drop of the dense loaded bed is higher than that of spherical particles which have approximately the same porosity. The results also revealed that the bed porosity, shape and contact points of the loaded catalyst have significant effects on the dynamic liquid holdup of the TBRs. Finally, a new correlation was developed for dynamic liquid holdup and pressure drop calculation for trilobe dense and sock catalyst beds and beds which are loaded with spherical particles.     

Self-assembled nanoporphyrins in the presence of gold bio-nanoparticles as heterogeneous nano-biocatalyst for green production of aldehydes and ketones

We report a simple and facile self-assembly method for the successful fabrication of a biological macromolecule, MnTPPCl (manganese(III) chloride 5,10,15,20-tetraphenylporphyrin), intercalated into gold nanoparticles using the cooperative effects of Sesbania sesban plant. This biohybrid was characterized using various techniques for further investigation. The catalytic activity of this biological hybrid was considered in the production of aldehydes and ketones from primary and secondary alcohols, respectively. Excellent conversions and selectivties were obtained applying Au@MnTPPCl colloidal nanocomposite and NaIO₄ as an oxygen donor in ethanol.     

Application of D‐optimal experimental design in nano‐sized ZSM‐5 synthesis for obtaining higher crystallinity

D‐optimal experimental design with three levels of SiO₂/Al₂O₃, template/SiO₂, H₂O/SiO₂, SiO₂/Na₂O and TPABr/TPAOH ratio parameters was used to optimize the experimental parameters by the analysis of variance (ANOVA). The effects of above mentioned ratios in the initial synthetic mixture on the crystallinity of the ZSM‐5 zeolite were studied. The synthesized samples were characterized by XRD, FE‐SEM, and TEM analysis. Fischer test results showed that SiO₂/Al₂O₃ and H₂O/SiO₂ molar ratios are the most and least effective parameters, respectively, in the range studied. The most important two‐way interaction variable was that of template/SiO₂ and Na₂O/SiO₂ molar ratios. The optimum composition of the gel compound to achieve relative maximum crystallinity is SiO₂/Al₂O₃ = 99.96, template/SiO₂ = 0.16, H₂O/SiO₂ = 34.68, Na₂O/SiO₂ = 0.02 and TPABr/TPAOH = 1.44.