Enhancement of the catalytic activity of Mg/Al layered double hydroxide for glycerol oligomers production.

In this study, the impact of rehydration on the catalytic properties of Mg/Al layered double hydroxides (LDH) for glycerol oligomerization was assesed. Although previous works have employed other LDH derived materials in this reaction, little information on recyclability is published. After observing the initial results on how basicity and surface area were related to the catalytic activty, an LDH modification strategy was developed with the addition of acetic acid. Changes on the basic site distribution were noticed and consequently, selectivity to diglycerol was improved. The best catalytic performance (reaction with 4 wt% cat., at 240 °C for 8 hours) led to 64% of glycerol conversion (XGly) and 37% of diglycerol selectivity (Sdi). Aditionally, reciclying of modified LDH was better than the non acid treated material, presenting higher yield of diglycerol. Catalyst deactivation was related to the harsh reaction conditions and to the blockage of active species by impurities. Loss of metallic species by leaching to the reaction products was not oberseved, an advantage in comparison with previous works.

Natural and Modified Montmorillonite Clays as Catalysts for Synthesis of Biolubricants.

In this study, natural and modified clays were evaluated as catalysts in an esterification reaction to obtain bio-based lubricants. The biolubricants are environmentally preferred to petroleum-based lubricants because they are biodegradable and non-toxic. Other advantages include very low volatility due to the high molecular weight and excellent viscosity properties with temperature variations. Modifications in natural clay were performed intending to obtain materials with different textural properties that could improve the reaction under study. The modified clays were obtained in two ways: by pillarization using Al13 Keggin polyoxocations or by acid treatments with H2SO4, HCl and HNO3. All samples were evaluated for the esterification reaction of fatty acids from castor oil (FACO) using 2-ethyl-hexanol. During the reaction step, a zeolite-based adsorbent was used for water removal to increase the reaction equilibrium conversion. Gas chromatography and nuclear magnetic resonance were performed to ensure the formation of the products. The highest conversion of fatty acids to esters was obtained using pillared clays. Adding adsorbent in the reaction medium (10 g of 3A zeolite to 100 g of FACO), the conversion improved from 74⁻88 wt % after 6 h at 50 °C.