The catalytic etherification of glycerol with tert-butyl alcohol over a strong acid ion-exchange commercial resin (Amberlyst 15) has been studied. The etherification reactions were carried out in a glass laboratory autoclave reactor with magnetic stirring without solvent at autogenous pressure. Experimental results were obtained at different temperatures (50−80 °C) and using an 8.5 wt % catalyst loading referred to the starting amount of glycerol. Four ethers (two monoethers and two diethers) and isobutylene were identified as the main products of glycerol etherification and tert-butyl alcohol dehydration (secondary reaction), respectively. Two simplified heterogeneus kinetic models are proposed to describe the process performance. The first model lumps the monoethers and diethers into the species M and D, respectively, and includes three reactions and the corresponding kinetic equations. The second model includes all of the species detected and six stoichiometric equations. Kinetic parameters for each kinetic model were estimated by data fitting. Irreversible dehydration of tert-butyl alcohol can be assumed at the operating conditions employed in the present study. Both kinetic models proposed describe the evolution of the system properly, in terms of both the reactant and product distributions with reaction time in the temperature range studied.

Background A study of the effect of different ion exchange resins, Amberlyst 15, Amberlite 200 and Amberlite IRC‐50, on glycerol etherification with tert‐butyl alcohol was performed. The best catalyst was selected based on the activity and selectivity values. The capability of reusing this catalyst after different pre‐treatments was analysed. A kinetic model was developed including the effect of catalyst concentration and temperature. Results Amberlyst 15 led to the highest glycerol conversion, the highest product yield, and it could be reused following proper pre‐treatment with methanol. The effect of catalyst concentration was evaluated and included in a previous kinetic model. Simulated results were found to be suitably fitted to the experimental ones. Conclusions The high activity value of Amberlyst 15 is related to its high acidity and better textural properties. Reuse of this catalyst was possible with an appropriate previous treatment. A kinetic model was validated including the effect of catalyst concentration and temperature on reactants conversion and products distribution. © 2013 Society of Chemical Industry

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New iron-oxide-based anodes are prepared by an environmentally-friendly and low-cost route. The analysis of the composition, structure, and microstructure of the samples reveals the presence of a major hematite phase, which is accompanied by a certain concentration of an oxyhydroxide phase, which can act as a “lithium-reservoir”. By using sodium alginate as a binder, the synthesized anodes display superior electrochemical response, i.e., high specific capacity values and high stability, not only versus Li but also versus a high voltage cathode in a full cell. From these bare materials, clay-supported anodes are further obtained using sepiolite and bentonite natural silicates. The electrochemical performance of such composites is improved, especially for the sepiolite-containing one treated at 400 °C. The thermal treatment at this temperature provides the optimal conditions for a synergic nano-architecture to develop between the clay and the hematite nanoparticles. High capacity values of ~2500 mA h g−1 after 30 cycles at 1 A g−1 and retentions close to 92% are obtained. Moreover, after 450 cycles at 2 A g−1 current rate, this composite electrode displays values as high as ~700 mA h g−1. These results are interpreted taking into account the interactions between the iron oxide nanoparticles and the sepiolite surface through hydrogen bonds. The electrochemical performance is not only dependent on the oxidation state and particle morphology, but the composition is revealed as a key feature.

Spinel oxides with composition LiMn2-xMxO4 (M, a transition metal) are intensively studied due to their remarkable electrochemical properties. This study deals with cathode materials based on the lithium iron manganese oxide LiFe0.5Mn1.5O4 synthesized by different methods (sol-gel, in solution and hydrothermal) in order to obtain samples with various morphologies. SEM results show microspheres, composed of nanosized/submicrometer-sized subunits, microrods with a less porous surface, and finally nanoparticles that form micro-sized aggregates. The samples obtained by both solution and hydrothermal methods provided the best electrochemical behavior. In all cases, the coulombic efficiency is around 90%, and it remains constant during the tested cycles. Specific capacities remain stable between 95% and 98% of capacity retention after series of cycles in samples formed by microspheres or micro-size aggregates. These values are notably higher than those obtained for the samples with particles of heterogeneous size (49%). A LiMn1.5Fe0.5O4/Li2MnO3 composite has been prepared by the solvothermal technique in order to increase its capacity and energy density. These cells show a good cyclability at different current densities. All cells based on these LiFe0.5Mn1.5O4 cathodes recover their discharge capacity when the current density returns to C/10.