• Energy Research

AbstractReview: 198 refs.

AbstractMeasurements on the diffusion coefficient of the neutral molecule N,N,N′,N′‐tetramethyl‐para‐phenylenediamine and the radical cation and dication generated by its one‐ and two‐electron oxidation, respectively, are reported over the range 298–348 K in both acetonitrile and four room temperature ionic liquids (RTILs). Data were collected using single and double potential step chronoamperometry at a gold disk electrode of micrometer dimension, and analysed via fitting to the appropriate analytical expression or, where necessary, to simulation. The variation of diffusion coefficient with temperature was found to occur in an Arrhenius‐type manner for all combinations of solute and solvent. For a given ionic liquid, the diffusional activation energies of each species were not only closely equivalent to each other, but also to the RTIL's activation energy of viscous flow. In acetonitrile supported with 0.1 M tetrabutylammonium perchlorate, the ratio in diffusion coefficients of the radical cation and dication to the neutral molecule were calculated as 0.89±0.05 and 0.51±0.03, respectively. In contrast, amongst the ionic liquids the same ratios were determined to be on average 0.53±0.04 and 0.33±0.03. The consequences of this dissimilarity are considered in terms of the modelling of voltammetric data gathered within ionic liquid solvents.

Electrochemical oxidation of four different alcohol molecules (methanol, ethanol, n-butanol and 2-butanol) at electrodeposited Pt film and carbon-supported Pt catalyst film electrodes, as well as the effect of mass transport on the oxidation reaction, has been studied systematically using the rotating disk electrode (RDE) technique. It was shown that oxidation current decreased with an increase in the rotation rate (ω) for all alcohols studied over electrodeposited Pt film electrodes. In contrast, the oxidation current was found to increase with an increase in the ω for Pt/C in ethanol and n-butanol-containing solutions. The decrease was found to be nearly reversible for ethanol and n-butanol at the electrodeposited Pt film electrode ruling out the possibility of intermediate COads poisoning being the sole cause of the decrease and was attributed to the formation of soluble intermediate species which diffuse away from the electrode at higher ω. In contrast, an increase in the current with an increase in ω for the carbon supported catalyst may suggest that the increase in residence time of the soluble species within the catalyst layer, results in further oxidation of these species. Furthermore, the reversibility of the peak current on decreasing the ω could indicate that the surface state has not significantly changed due to the sluggish reaction kinetics of ethanol and n-butanol.

AbstractA systematic study of Ni supported on metal–organic frameworks (MOFs) catalyst (i.e., 15Ni/UiO‐66) for catalytic CO2 hydrogenation under nonthermal plasma (NTP) conditions was presented. The catalyst outperformed other catalysts based on conventional supports such as ZrO2, representing highest CO2 conversion and CH4 selectivity at about 85 and 99%, respectively. We found that the turnover frequency of the NTP catalysis system (1.8 ± 0.02 s−1) has a nearly two‐fold improvement compared with the thermal catalysis (1.0 ± 0.06 s−1). After 20 hr test, XPS and HRTEM characterizations confirmed the stability of the 15Ni/UiO‐66 catalyst in the NTP‐activated catalysis. The activation barrier for the NTP‐activated catalysis was calculated as ~32 kJ mol−1, being lower than the activation energy of the thermal catalysis (~70 kJ mol−1). In situ DRIFTS characterization confirmed the formation of multiple carbonates and formates on catalyst surface activated by NTP, surpassing the control catalysts (e.g., 15Ni/α‐Al2O3 and 15Ni/ZrO2).

Natural dolomitic rock has been investigated in the transesterification of C4 and C8 triglycerides and olive oil with a view to determining its viability as a solid base catalyst for use in biodiesel synthesis. XRD reveals that the dolomitic rock comprised 77% dolomite and 23% magnesian calcite. The generation of basic sites requires calcination at 900 ◦C, which increases the surface area and transforms the mineral intoMgO nanocrystallites dispersed over CaO particles. Calcined dolomitic rock exhibits high activity towards the liquid phase transesterification of glyceryl tributyrate and trioctanoate, and even olive oil, with methanol for biodiesel production.

In this work, a variation in heat treatment atmosphere approach is taken to provide a series of related PtSn catalysts with the same nominal composition of Pt3Sn, but with different surface compositions.