Investigation on the sufficiency and uniformity of channel-porous layer flow in PEM fuel cells

Acting as the reactant distributor, the gas channel (GC)-gas diffusion layer (GDL) assembly is of significance to the PEM fuel cell performance and durability. In this work, an analytical flow model has been developed for the GC-GDL system. Based on the explicit expressions of the channel-porous layer flow structure, the effects of geometrical parameters are clarified and the flow effects including reactant conversion and uniformity are further derived and clarified. Results reveal that with thinner GDL or longer GC, the nonlinear decrease of axial velocity becomes faster and the decrease of transverse velocity turns from linear to nonlinear. Furthermore, the reactant conversion and uniformity are in an opposite relationship and the criterion of flow homogenization in the fuel cells is proposed to make a trade-off. Moreover, the flow non-uniformity is positively correlated with GC length, which gains insights into the fuel cell scale-up.

Investigation on Synthesis of Trimethylolpropane (TMP) Ester from Non-edible Oil

Trimethylolpropane (TMP) ester is an eco-friendly lubricant that fully biodegradable and known as bio lubricant. In this study, TMP ester was produced from waste cooking oil and rubber seed oil through a two-step synthesis approach. The reaction is two stages transesterifications, in which the waste cooking oil and the rubber seed oil were first transesterified with methanol to produce methyl ester, followed by transesterification with TMP using para-Toluenesulfonic acid (p-TSA) as catalyst. Various effects of operating conditions were observed, such as reaction time, temperature and molar ratio of reactants. The TMP ester formation was determined based on the quantity of reactant conversion. The synthesized TMP ester was compared and characterized according to their properties. The results showed that the TMP ester from waste cooking oil (WCO) has shown better conversion compare to TMP ester from rubber seed oil (RSO), within a similar operating condition. The highest TMP ester conversion from WCO is 71%, at temperature of 150 ºC with molar ratio of FAME to TMP of 3:1 and catalyst amount of 2% (wt/wt). In addition, these polyol based esters from WCO and RSO exhibit appropriate basic properties for viscosity when compare with requirement standard of lubricant ISO VG46. Copyright © 2020 BCREC Group. All rights reserved

Novel Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity as Both Solvents and Catalysts for Friedel–Crafts Alkylation

Unique tunable aryl-imidazolium magnetic ionic liquids with dual functions as a solvent–catalyst and dual Brønsted–Lewis acidity (B-L MILs) are applied for Friedel–Crafts alkylation without additional solvents. The catalytic properties of these B-L MILs in the Friedel–Crafts alkylation of p-xylene with benzyl chloride are investigated. The various reaction parameters, including the catalyst dosage, reaction time, reaction temperature, molar ratio of reactants, and reusability, are discussed. The results show that the B-L MIL 5c has more excellent product selectivity (>99%) and reactant conversion (>99%) under the following optimum conditions (reaction temperature = 80 °C, reaction time = 0.5 h, molar ratio of p-xylene to benzyl chloride = 6:1, and catalyst 5c dosage = 1.0 mole %) than traditional catalysts reported in the previous literature. Specifically, due to the mesomeric effect between the FeCl4 anion and hydrogen atom at cationic moiety, the catalyst B-L MILs with the molar fraction of FeCl3 equal to 0.5 can be easily recovered and provide satisfactory catalytic activity after being re-used six times.

Investigation of Reactant Conversion in the Vanadium Redox Flow Battery Using Spatially Resolved State of Charge Mapping

Segmented cells enable real time visualization of the flow distribution in vanadium redox flow batteries by local current or voltage mapping. The lateral flow of current within thick porous electrodes, however, impairs the local resolution of the detected signals. In this study, the open circuit voltage immediately after the cessation of charge/discharge is used for the mapping of reactant conversion. This quantity is not hampered by lateral flow of current and can be conveniently transformed to the corresponding state of charge. The difference between theoretically calculated and experimentally determined conversion (change in the state of charge) across the electrode is used to determine local variations in conversion efficiency. The method is validated by systematic experiments using electrodes with different modifications, varying current densities and flow configurations. The procedure and the interpretation are simple and scalable to any size of flow cell.

Facile Route for Bio-Phenol Siloxane Synthesis via Heterogeneous Catalytic Method and its Autonomic Antibacterial Property

Eugenol, used as bio-phenol, was designed to replace the hydrogen atom of hydrogenterminated siloxane by hydrosilylation reaction under the presence of alumina-supported platinum catalyst (Pt-Al2O3), silica-supported platinum catalyst (Pt-SiO2) and carbon nanotube-supported platinum catalyst (Pt-CNT), respectively. The catalytic activities of these three platinum catalysts were measured by nuclear magnetic resonance hydrogen spectrometer (1H NMR). The properties of bio-phenol siloxane were characterized by Fourier transform infrared spectrometer (FT–IR), UV-visible spectrophotometer (UV) and thermogravimeter (TGA), and its antibacterial property against Escherichia coli was also studied. The results showed that the catalytic activity of the catalyst Pt-CNT was preferable. When the catalyst concentration was 100 ppm, the reaction temperature was 80 °C and reaction time was 6 h, the reactant conversion rate reached 97%. After modification with bio-phenol, the thermal stability of the obtained bio-phenol siloxane was improved. For bio-phenol siloxane, when the ratio of weight loss reached 98%, the pyrolysis temperature was raised to 663 °C which was 60 °C higher than hydrogenterminated siloxane. Meanwhile, its autonomic antibacterial property against Escherichia coli was improved significantly.