Biodiesel Production by Methanolysis of Rapeseed Oil-Influence of SiO2/Al2O3 Ratio in BEA Zeolite Structure on Physicochemical and Catalytic Properties of Zeolite Systems with Alkaline Earth Oxides (MgO, CaO, SrO)

Alkaline earth metal oxide (MgO, CaO, SrO) catalysts supported on BEA zeolite were prepared by a wet impregnation method and tested in the transesterification reaction of rapeseed oil with methanol towards the formation of biodiesel (FAMEs-fatty acid methyl esters). To assess the influence of the SiO2/Al2O3 ratio on the catalytic activity in the tested reaction, a BEA zeolite carrier material with different Si/Al ratios was used. The prepared catalysts were tested in the transesterification reaction at temperatures of 180 °C and 220 °C using a molar ratio of methanol/oil reagents of 9:1. The transesterification process was carried out for 2 h with the catalyst mass of 0.5 g. The oil conversion value and efficiency towards FAME formation were determined using the HPLC technique. The physicochemical properties of the catalysts were determined using the following research techniques: CO2-TPD, XRD, BET, FTIR, and SEM-EDS. The results of the catalytic activity showed that higher activity in the tested process was confirmed for the catalysts supported on the BEA zeolite characterized by the highest silica/alumina ratio for the reaction carried out at a temperature of 220 °C. The most active zeolite catalyst was the 10% CaO/BEA system (Si/Al = 300), which showed the highest triglyceride (TG) conversion of 90.5% and the second highest FAME yield of 94.6% in the transesterification reaction carried out at 220 °C. The high activity of this system is associated with its alkalinity, high value of the specific surface area, the size of the active phase crystallites, and its characteristic sorption properties in relation to methanol.

Structured clay minerals-based nanomaterials for sustainable photo/thermal carbon dioxide conversion to cleaner fuels: A critical review

In efforts to achieve a sustainable development goal, the utilization of CO₂ to generate renewable fuels is promising, as it is a sustainable technology that provides affordable and clean energy. To realize the production of renewable green fuels, a proficient and low-cost technology is required. Using photo/thermal catalytic process, the goal of sustainable CO₂ hydrogenation can be achieved. There have been several types of catalysts under exploration, however, they are expensive with limited availability. In the current development, green materials such as mineral clays are emerging as cocatalyst/supports for CO₂ hydrogenation. Clays are bestowed with various beneficial properties such as a large surface area, high porosity, abundant basic sites, excellent thermal stability and chemical corrosion resistance. Clays are promising materials that can drastically reduce the cost in catalyst preparation, partially fulfil the energy demand and reduce greenhouse gas emission. This review aims to focus on the various types of clays and their applications in the field of photo/thermal CO₂ hydrogenation to renewable fuels. Firstly, the classifications of clays are provided, whereby they can be differentiated based on their silicate layers, namely 1:1 and 2:1 type clay and their properties are thoroughly discussed to provide advantages and applications. The applications of various clays such as kaolinite, halloysite, montmorillonite, attapulgite, saponite and volkonskoite for CO₂ hydrogenation reactions are systematically discoursed. In addition, various approaches to improve the capability of raw clays as catalyst support are critically discussed, which include thermal treatment, exfoliation, acid-leaching and pillaring approaches. A critical discussion regarding the engineering aspects to further enhance clay-based catalyst for CO₂ hydrogenation are further disclosed. In short, clays are freely available materials that can be found in abundance. However, there are many more different types of natural green clays that have not been studied and explored in various energy applications.