Effect of process variables on product yield distribution in thermal catalytic cracking of naphtha to light olefins over Fe/HZSM-5

The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the production of light olefins has been studied. The response surface defined by three most significant parameters is obtained from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature, while propylene shows an optimum at 650 °C. Moderate WHSV is favorable for maximum production of light olefins. Addition of Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene) at 670 °C, 44 hr⁻¹ and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%.     

Thermodynamic and Kinetic Behavior of B and Na Through the Contact of B-Doped Silicon with Na2O-SiO2 Slags

Boron (B) is the most problematic impurity to be removed in the processes applied for the production of solar grade silicon. Boron removal from liquid silicon by sodium-silicate slags is experimentally studied and it is indicated that B can be rapidly removed within short reaction times. The B removal rate is higher at higher temperatures and higher Na₂O concentrations in the slag. Based on the experimental results and thermodynamic calculations, it is proposed that B removal from silicon phase takes place through its oxidation at the slag/Si interfacial area by Na₂O and that the oxidized B is further gasified from the slag through the formation of sodium metaborate (Na₂B₂O₄) at the slag/gas interfacial area. The overall rate of B removal is mainly controlled by these two chemical reactions. However, it is further proposed that the B removal rate from silicon depends on the mass transport of Na in the system. Sodium is transferred from slag to the molten silicon through the silicothermic reduction of Na₂O at the slag/Si interface and it simultaneously evaporates at the Si/gas interfacial area. This causes a Na concentration rise in silicon and its further decline after reaching a maximum. A major part of the Na loss from the slag is due to its carbothermic reduction and formation of Na gas.     

High-voltage portable pulsed power supply fed by low voltage source

This article proposes a new structure of voltage multiplier for portable pulsed power applications. In this configuration, which is based on capacitor-diode voltage multiplier, the capacitors are charged by low AC input voltage and discharge through the load in series during pulse generation mode. The proposed topology is achieved by integrating of solid-state switches with conventional voltage multiplier, which can increase the low input voltage step by step and generate high-voltage high-frequency pulsed power across the load. After some discussion, simulations and experimental results are provided to verify the effectiveness of the proposed topology.     

Antioxidant Capacity and Phenolic Content of the Aqueous Extract of Commonly Consumed Cucurbits

The antioxidant capacity of commonly consumed cucurbits vegetable was determined by the DPPH, FRAP, Fe³⁺ reducing power, and hydrogen peroxide scavenging assay. The aqueous extract of Luffa cylindrica showed the highest value of phenolic content and antioxidant capacity based on FRAP, Fe³⁺ reducing power, and hydrogen peroxide scavenging assay. However, Laginaria siceraria extract showed the highest flavonoid and DPPH scavenging activities among all three cucurbits used in this study. Phenolic content in aqueous extracts of Luffa cylindrica and Laginaria siceraria was almost equal. Cucurbita maxima exhibited the lowest phenolic, flavonoid content, and exhibited the lowest power of antioxidant scavenging. The antioxidant capacity of cucurbits was significantly correlated (P < 0.05) with the phenolic content of their extracts. The antioxidant capacity of Luffa cylindrica and Laginaria siceraria have also shown a significant correlation (P < 0.05).     

In vitro studies on calf thymus DNA interaction and 2-tert-butyl-4-methylphenol food additive

The interaction of native calf thymus DNA (CT-DNA) with 2-tert-butyl-4-methylphenol (TBMP) at physiological pH has been investigated by spectrofluorometric and viscosimetric techniques. TBMP molecules were found to intercalate between base pairs of DNA, demonstrated by an increase in the specific viscosity of DNA and decrease in the fluorescence of TBMP solutions in the presence of increasing amounts of DNA and the calculated binding constants (K _f) at different temperatures. Furthermore, the enthalpy and entropy of the reaction between TBMP and CT-DNA showed that the reaction is exothermic and enthalpy favored (ΔH = −19.18 kJ mol⁻¹; ΔS = −26.98 J mol⁻¹ K⁻¹) which are other evidences to indicate that TBMP is able to be intercalated in the DNA base pairs.     

Reconfiguration and DG Sizing and Placement Using Improved Shuffled Frog Leaping Algorithm

Abstract

In this paper is proposed a reconfiguration methodology with the presence of Distributed Generation (DG), aimed at achieving the minimum power loss, minimum number of switching operation and minimum deviation of bus voltage while satisfying all constraints using improved shuffled frog leaping algorithm (ISFLA).The performance of the proposed method is examined on 33 and 69 bus IEEE test distribution systems. The ISFLA performance is evaluated with the well-known algorithm including of harmony search algorithm (HSA), refined genetic algorithm (GRA), particle swarm optimization (PSO), differential evolutionary (DE) and conventional SFLA. Simulation results showed that the total power loss and voltage bus minimum in primary distribution network can be reduced significantly. Also the results in different scenarios are showed that the simultaneous reconfiguration and DG placement method is better in less losses and also in more minimum voltage. Moreover, the ISFLA superiority is proved in comparison with the HAS, GRA, PSO, DE, and SFLA in view of more convergence speed and accuracy and also converges in less number iteration. Also, the performance of the proposed method is favorable compared to previous studies.     

Functional egg white–pectin conjugates prepared by controlled Maillard reaction

Changes in the functional properties of egg white (EW) protein/pectin mixtures and their chemical conjugation via the Maillard reaction were investigated. Pectin with high degrees of esterification was conjugated to EW protein at 60 °C and 79% relative humidity for 0, 6, 12, 24 and 48 h. The conjugates were compared with a physical mixture of the two components. There was a significant decrease in the available lysine (free amino groups) of the conjugated protein during incubation with the polysaccharides, negatively correlated to the emulsification properties. Oil–water emulsions prepared using the EW–pectin conjugates showed good stability, with oil droplet mean volume diameters of 0.29–1.2 μm. The conjugates showed higher emulsion viscosity and stability than the raw materials at ambient temperature. Addition of pectin (0.05–0.5% w/v) to EW at concentrations of 1% and 5% w/v had a significant effect on foam volume and stability.