Transesterification of Rice Bran Oil with Methanol Catalyzed by Mg(Al)La Hydrotalcites and Metal/MgAl Oxides

Abstract

Both MgAl and Mg(Al)La hydrotalcites were synthesized by an alkali-free coprecipitation method and calcined to their corresponding oxides. MgAl oxide was impregnated with different kinds of metals (M ) Cs, Sr, Ba, and La). All materials were characterized by the XRD, FT-IR, BET, NH 3 TPD, and SEM techniques. The catalytic activity order of the M/MgAl oxides in the transesterification of glyceryl tributyrate (a model triglyceride) with methanol was found to be Cs > Ba ≈ Sr > La. The Mg(Al)La hydrotalcite that was calcined and then rehydrated contains Brønsted base sites, exhibiting higher activity than the calcined sample with Lewis base sites. In the preparation of biodiesel from rice bran oil via a two-step catalyzed process, crude rice bran oil (11.14% FFAs) was first dewaxed/degummed and then esterified using silica-supported heteropolyacid H 3 PW 12 O 40 . FFAs were decreased to 0.98% at 70°C in 4 h. This oil was then transesterified with methanol using the rehydrated Mg(Al)La hydrotalcites. At a temperature of 100°C, a reaction time of 9 h, a methanol/oil molar ratio of 30:1, and a catalyst content of 7.5 wt %, biodiesel with 97% ester content and 78% product yield was obtained.

Dry reforming of methane to syngas over La-promoted hydrotalcite clay-derived catalysts

“…The same applies to (Mg þ Ni)/Al, especially in LaHT3 and LaHT3.5. This fact may be ascribed to favoured precipitation of aluminium hydroxide because of its higher pK a value [22]. Ni and La contents matched expected values.…”

Hydrotalcite: recyclable, novel heterogeneous catalyst for facile, environmentally benign and high yielding multi-component synthesis and mechanistic study under solvent free conditions

“…However, the Mg-Al mixed oxide was found to be thermally and mechanically stable and no significant difference was observed in the particle size and morphology of the used catalyst, as evidenced by SEM. 21,22 The XRD data of the recovered hydrotalcite showed a similar profile to the fresh catalyst, which confirmed the layered structure of hydrotalcite was maintained after the reaction.…”

Elucidating the Crystal Face- and Hydration-Dependent Catalytic Activity of Hydrotalcites in Biodiesel Production

“…A variety of heterogeneously catalyzed pathways have been explored in the literature, involving both solid acids and solid bases, and many of these have been addressed in recent reviews. − Among these methods, hydrotalcites have received considerable attention as heterogeneous catalysts for a wide variety of traditionally base-catalyzed organic transformations, including the transesterification reactions utilized in biodiesel production. − Hydrotalcites are a family of structural analogues to the mineral hydrotalcite, Mg 6 Al 2 (OH) 16 CO 3 ·4H 2 O, a layered double hydroxide (LDH) consisting of layers of divalent Mg 2+ ions coordinated in an octahedral fashion by structural hydroxyl groups. These metal−hydroxyl complexes form layers via edge sharing in the ab crystallographic plane, which then stack in the c plane to form three-dimensional structures; the structure is shown schematically in Figure .…”