Energy analysis of an electrolytic-based selective CO oxidation system for on-board pure hydrogen production

Carbon monoxide (CO) in the hydrogen (H₂) stream diminishes the performance of a low temperature polymer electrolyte membrane (PEM) fuel cell significantly. The existing technologies for on-board/site production of pure hydrogen with low CO concentrations operate at high temperatures and pressures and need on-board oxygen or air supply for CO oxidation. This study offers an alternative solution to on-board/site production of hydrogen suitable for low temperature PEM fuel cell applications. A thorough energy analysis and parametric study have been carried out to investigate the effect of different operating parameters on the performance of an electrolytic-based selective CO oxidation system operating at room temperature. Such a system electrochemically removes the CO molecules in a fuel stream where they are adsorbed onto the catalyst surface at the anode side of an electrolyzer, and produces additional hydrogen at the cathode side through an electrochemical water gas shift reaction. This additional hydrogen thus offsets the energy required to drive the electrolysis, making it an attractive solution for on-board/site applications. The breakthrough curves are measured for the adsorber (50 cm² area PEM reactor) fed with different CO concentrations (100, 300 and 500 ppm CO) present in the wet hydrogen stream at different flow rates (40, 80, 120, 160 and 200 ml min⁻¹), under the room temperature and atmospheric pressure. The electrolytic process (regeneration) parameters are optimized with an attempt of completely removing the adsorbed CO molecules. Furthermore, a thermodynamic-electrochemical model is developed to simulate the energy balance of the electrolyzer indicating that this process offsets the actual energy consumption as it produces extra hydrogen. Thermodynamically, removing CO by electricity is more efficient than by heat which leads to high energy efficiencies (>80%). The study has demonstrated that the electrolytic-based selective CO oxidation system is a promising system for on-board/site pure hydrogen production.     

Facile and clean electrochemical synthesis of new acetaminophen derivatives through electrochemical oxidation of acetaminophen in the presence of thiouracil derivatives

The electrochemical oxidation of acetaminophen (1a) is carried out in the presence of thiouracil derivatives (3a–c), as nucleophiles, in an acetate buffer solution (0.15?M, pH 5) mixed with Dimethylformamide (DMF) using cyclic voltammetry and coulometry under a constant potential. The results obtained indicate that N-acetyl-p-benzoquinone-imine derived from acetaminophen participates in a 1,4-Michael-type addition reaction with thiouracils to form the corresponding acetaminophen derivatives (4a–c) in good yields and with high purities using a facile, catalyst-free, and one-pot electrochemical method using three carbon electrodes in an undivided cell under mild conditions. The products obtained were characterized after purification by IR, ¹H NMR, and ¹³C NMR spectroscopies, and by the elemental analysis method.     

Performance of a biohydrogen solid oxide fuel cell

For solid oxide fuel cells (SOFCs), biohydrogen is an ideal fuel, which introduces a clean renewable energy source to a highly efficient energy conversion technology with minimum complications. The performance of a SOFC working with biohydrogen, and the effects of fuel composition, working temperature, load, and air utilization are less well understood. In this study a comprehensive numerical model was employed to investigate the biohydrogen fueled SOFC in different working conditions. Direct electrochemical oxidation of H₂ and CO and water gas shift reaction (WGSR) were considered in the model. An experimental set up was built to verify the simulation results. Results from the numerical model were validated against experimental polarization curves and cell temperature measurements. The results showed how different parameters affect the performance of a biohydrogen SOFC and how different working conditions can be selected to meet certain criteria.     

The fabrication of nanocomposites via calcium phosphate formation on gelatin–chitosan network and the gelatin influence on the properties of biphasic composites

A novel biodegradable polymer–ceramic nanocomposite which consisted of gelatin (Gel), chitosan (CS), and calcium phosphate (CaP) nanoparticles was prepared based on in situ preparation method. The fabricated biocomposites were characterized by FTIR, X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscope with X-ray elemental analysis (SEM-EDX). The characterization results confirmed that the crystalline calcium phosphate nanoparticles were mineralized in polymeric matrix and the interaction between Ca2+ in calcium phosphate and functional groups in polymers molecular chains was formed. XRD result showed that in addition to hydroxyapatite (HA), Brushite (BR) and tricalcium phosphate (β-TCP) particles also were formed due to lack of complete penetration of the basic solution into the polymeric matrix. However, SEM image indicated that the polymeric matrix has the controlling role in the particle size of calcium phosphate. The size of particles in three component composites was about 100 nm while in two component composites proved to be more in μm size. TEM observation supported SEM results and showed that the three component composites have calcium phosphate nanoparticles. The elastic modulus and compressive strength of the composites were also improved by the employment of gelatin and chitosan together, which can make them more beneficial for surgical applications.     

Leader election using loneliness detection

We consider the problem of leader election (LE) in single-hop radio networks with synchronized time slots for transmitting and receiving messages. We assume that the actual number n of processes is unknown, while the size u of the ID space is known, but is possibly much larger. We consider two types of collision detection: strong (SCD), whereby all processes detect collisions, and weak (WCD), whereby only non-transmitting processes detect collisions. We introduce loneliness detection (LD) as a key subproblem for solving LE in WCD systems. LD informs all processes whether the system contains exactly one process or more than one. We show that LD captures the difference in power between SCD and WCD, by providing an implementation of SCD over WCD and LD. We present two algorithms that solve deterministic and probabilistic LD in WCD systems with time costs of ${\mathcal{O}(\log \frac{u}{n})}$ and ${\mathcal{O}(\min( \log \frac{u}{n}, \frac{\log (1/\epsilon)}{n}))}$ , respectively, where ${\epsilon}$ is the error probability. We also provide matching lower bounds. Assuming LD is solved, we show that SCD systems can be emulated in WCD systems with factor-2 overhead in time. We present two algorithms that solve deterministic and probabilistic LE in SCD systems with time costs of ${\mathcal{O}(\log u)}$ and ${\mathcal{O}(\min ( \log u, \log \log n + \log (\frac{1}{\epsilon})))}$ , respectively, where ${\epsilon}$ is the error probability. We provide matching lower bounds.     

Total phenolic contents and antioxidant activity of corn tassel extracts

Ground corn tassels, a by-product of corn, were used as a source of phenolic compounds. Water, ethanol, methanol, acetone, hexane, chloroform, butanol, petroleum ether and methylene chloride were evaluated as different polarity solvents to extract these phenolic compounds. Ethanol exhibited the highest extraction ability for such phenolic compounds, followed by methanol and water, where the total phenols were 0.1575%, 0.1125% and 0.0737%, respectively. Antioxidant activity of corn tassels ranged from 83.0% to 85.2%, 69.9% to 83.7%, 69.8% to 80.4%, 22.2% to 49.1% and 14.8% to 19.3% radical scavenging activity (% RSA) for ethanol, methanol, acetone, butanol and water extracts, respectively. The ethanolic extract of the corn tassels was successfully utilised to retard the oxidation of sunflower oil and the obtained induction period values were comparable to those of tert-butylhydroquinone (TBHQ).     

Removal of oil from biodiesel wastewater by electrocoagulation method

An attempt has been made to remove oil and grease (O&G) from biodiesel wastewater as well as O&G and turbidity in the presence of H₂O₂ and polyaluminum chloride (PAC), as a coagulant-aid by an electrochemical method using iron as sacrificial electrodes. The effects of current density, amount of hydrogen peroxide using as an oxidizing agent and addition of coagulant-aid, on percent removal and energy consumption have been investigated. The removal efficiency of O&G was in the range of 62–86%, whereas O&G removal was 100% in the current density range of 10–12.5 mAcm^?2 depending on the concentrations of H₂O₂ and coagulant aid. It is obtained that electrocoagulation in the absence of coagulant aid and oxidant is not too efficient for the treatment of this type of wastewater.     

Convective‐radiative fins with simultaneous variation of thermal conductivity,heat transfer coefficient,and surface emissivity with temperature

This paper is a numerical study of thermal performance of a convective‐radiative fin with simultaneous variation of thermal conductivity, heat transfer coefficient, and surface emissivity with temperature. The convective heat transfer is assumed to be a power function of the local temperature between the fin and the ambient which allows simulation of different convection mechanisms such as natural convection (laminar and turbulent), boiling, etc. The thermal conductivity and the surface emissivity are treated as linear functions of the local temperature between the fin and the ambient which provide a satisfactory representation of the thermal property variations of most fin materials. The thermal performance is governed by seven parameters, namely, convection–conduction parameter Nc, radiation–conduction parameter Nr, thermal conductivity parameter A, emissivity parameter B, the exponent n associated with convective heat transfer coefficient, and the two temperature ratios, θ_a and θ_s, that characterize the temperatures of convection and radiation sinks. The effect of these parameters on the temperature distribution and fin heat transfer rate are illustrated and the results interpreted in physical terms. Compared with the constant properties model, the fin heat transfer rate can be underestimated or overestimated considerably depending on the values of the governing parameters. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20408