Preparation of biodiesel from soybean oil using La/Mn oxide catalyst

• Biodiesel was obtained over La/Mn oxide in a yield of 99% from soybean oil.
• LaMnO3.15 is the dominant compound in the catalyst.
• Catalyst exhibits high activity and can be easily recovered and regenerated.
• The La/Mn oxide is reusable even after 15 cycles.

The solid catalyst La/Mn oxide was prepared using co-precipitation method. The catalytic behavior for catalyzing transesterification of soybean oil with methanol under subcritical conditions was investigated in a batch reactor; optimization of several parameters for catalyst preparation and transesterification reaction was also performed. The triglyceride (TG) conversion of above 99% was obtained using La/Mn oxide catalyst prepared with La:Mn molar ratio of 2:1 and calcined at 600 °C for 90 min, under such reaction conditions as 3 wt.% of catalyst, methanol/oil molar ratio of 12:1, reaction temperature and time of 180 °C and 60 min, respectively. The catalyst shows good reusability, and can resist FFA to some extent. However, it is sensitive to water. The mechanisms of catalytic activity and deactivation were discussed according to the characterization of the fresh and used catalysts using basic strength, BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS), and X-ray diffraction (XRD). Results demonstrated that the complex oxide LaMnO3.15 was the dominant component. The crystalline structure of the catalyst after use changed remarkably and the active sites might be occupied by organics, which led to the deactivation or diminished activity of the catalyst in the repeated use process.

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