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Salinity gradient power is a renewable, non-intermittent, and neutral carbon energy source. Reverse electrodialysis is one of the most efficient and mature techniques that can harvest this energy from natural estuaries produced by the mixture of seawater and river water. For this, the development of cheap and suitable ion-exchange membranes is crucial for a harvest profitability energy from salinity gradients. In this work, both anion-exchange membrane and cation-exchange membrane based on poly(epichlorohydrin) and polyvinyl chloride, respectively, were synthesized at a laboratory scale (255 cm2) by way of a solvent evaporation technique. Anion-exchange membrane was surface modified with poly(ethylenimine) and glutaraldehyde, while cellulose acetate was used for the cation exchange membrane structural modification. Modified cation-exchange membrane showed an increase in surface hydrophilicity, ion transportation and permselectivity. Structural modification on the cation-exchange membrane was evidenced by scanning electron microscopy. For the modified anion exchange membrane, a decrease in swelling degree and an increase in both the ion exchange capacity and the fixed charge density suggests an improved performance over the unmodified membrane. Finally, the results obtained in both modified membranes suggest that an enhanced performance in blue energy generation can be expected from these membranes using the reverse electrodialysis technique.

Biodiesel produced through catalytic transesterification of triglycerides from edible and non-edible oils and alcohol is considered an alternative to traditional petro-diesel. The interest in the use of alkaline earth metal oxides as heterogeneous basic catalysts has increased due to their availability, non-toxicity, the capacity to be reused, low cost, and high concentration of surface basic sites that provide the activity. This work is a compilation of the strategies to understand the effect of the source, synthesis, and thermal treatment of MgO, CaO, SrO, and BaO on the improvement of the surface basic sites density and strength, the morphology of the solid structure, stability during reaction and reusability. These parameters are commonly modified or enhanced by mixing these oxides or with alkaline metals. Also, the improvement of the acid-base properties and to avoid the lixiviation of catalysts can be achieved by supporting the alkaline earth metal oxides on another oxide. Additionally, the effect of the most relevant operation conditions in oil transesterification reactions such as methanol to oil ratio, temperature, agitation method, pressure, and catalysts concentration are reviewed. This review attempts to elucidate the optimum parameters of reaction and their application in different oils.

This work showed that the use of Al 2 O 3 -TiO 2 as carriers has a positive effect on the activity of supported NiW catalysts in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene carried out in a batch reactor at 320°C and total H 2 pressure of 5.5 MPa. Two Al 2 O 3 -TiO 2 mixed oxides with Al/Ti atomic ratios of 10 and 2 were synthesized by sol-gel method together with the pure Al 2 O 3 synthesized as reference support. For NiW/ Al 2 O 3 -TiO 2 and NiW/Al 2 O 3 catalysts, a metal load of 17 and 5.5 wt% of W and Ni were considered respectively. It was found that both Al 2 O 3 -TiO 2 -supported catalysts exhibited higher activity than alumina-supported one. The catalyst with a largest TiO 2 content (NiW/AT2) demonstrated to be 23 % more active with respect to NiW/Al 2 O 3 . Solids were characterized by temperature-programmed reduction (TPR), high resolution transmission electronic microscopy and X-ray photoelectronic spectroscopy (XPS) techniques. A decrease in support-metal interaction (from TPR) was observed when Ti content increased, which could lead to a higher amount of NiWS phase (from XPS). Besides, a slight increase in the slabs length in WS 2 was observed for titania-containing catalyst with respect to NiW/Al 2 O 3 , indicating that the dispersion can still be optimized. The atomic ratio Al/Ti = 2 of the NiW/Al 2 O 3 -TiO 2 catalyst proved to be a potential substitute for current catalysts for sulfur reduction in ultra-clean diesel.