Microwave irradiation has attracted a great deal of attention when it comes to synthesis of organic and inorganic materials. In the present study, a microwave heating system was utilized to prepare KOH/Ca 12 Al 14 O 33 nanocatalysts via combustion method, so as to produce biodiesel from canola oil. More- over, the effect of carbon content of fuels such as urea, ammonium acetate, glycerol and diethylene glycol used in the combustion reaction on the properties of the synthesized nanocatalysts was evaluated. The samples were analyzed by XRD, FTIR, TGA, BET-BJH, FESEM, and EDX techniques, with their basicity levels evaluated by Hammett indicator. The results showed that the combustion temperature tends to decrease with an increase in carbon content of fuel. Accordingly, the supports synthesized by urea and ammonium acetate exhibited the best crystalline structures. However, all samples showed Ca 12 Al 14 O 33 structure dur- ing impregnation by KOH and calcination step. The samples prepared by urea and ammonium acetate, as fuel, presented appropriate percentages of material-to-parent solution ratio, bringing about higher ac- tivities. Among them, the KOH/Ca 12 Al 14 O 33 synthesized by urea had the largest surface area and activity, so that it succeeded to convert 83.5% of canola oil to biodiesel via microwave irradiation at microwave power of 450 W, methanol-to-oil molar ratio of 12, catalyst concentration of 4 wt. %, and reaction time of 60 min. The sample showed high reusability when it was calcined at 700 °C after each round of reaction.

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