Solid catalyst (Na 2 CO 3 @EFD) was prepared by wet impregnation of electric furnace dust (EFD) in aqueous Na 2 CO 3 solution. It had high basicity and acidity of 0.34 and 0.16 mmol/g for biodiesel production. High biodiesel yield of 99.8 wt% from soybean oil was obtained under the optimized reaction conditions (by Central Composite Design) of 71 °C in 111.36 min with 5.4 wt% catalyst and methanol/oil molar ratio of 11.8/1. After 11 cycles, biodiesel yield still maintained at 90.8 wt% with catalyst recovery rate >90 wt% by magnetic separation of catalyst EFD powders (containing Fe 3 O 4 with magnetism of 59.1 Am 2 /kg). Pure Na 2 CO 3 particles presented poorer recyclability with lower biodiesel yield of 89.5 wt% even at the eighth cycle by centrifugal separation . Na 2 CO 3 @EFD catalyst had high activity and recyclability because: (i) EFD as support hosted nanoparticles of Na 2 CO 3 (30.3 nm) as main base site for transesterification ; (ii) porous EFD support provided acidic sites from metal oxides (e.g., ZnO and Al 2 O 3 ) for esterification; (iii) EFD adsorbed active components into its micropores to maintain high recyclability; and (iv) EFD magnetism from magnetic Fe 3 O 4 kept high efficient magnetic separation. Total metals in the blended biodiesel met the National Standard of China and heavy metals were lower than typical petrochemical diesel . The study gave a practical use of industrial solid waste for the green production of biodiesel.
Highly stable heterogeneous catalysts were prepared by impregnating carbonates suspension solutions onto electric furnace dust (EFD) and being calcined at high-temperature for the production of biodiesel from soybean oil. Process of impregnating with CaCO 3 , BaCO 3 , SrCO 3 and CdCO 3 suspension solutions and being calcined at high-temperature did not promote improvement of catalytic activity of EFD powder, while the single impregnating with K 2 CO 3 suspension solution can only improve its catalytic activity in the first use. Na 2 CO 3 @EFD catalyst synthesized by impregnating with only Na 2 CO 3 suspension solution owned considerable catalytic activity from nano Na 2 CO 3 (37.0 nm) and good recyclability from nano Fe 3 O 4 (size of 30.0 nm & Ms of 26.77 Am 2 /kg) with biodiesel yield of 99.13 wt% at 65 °C in 2 h with 15/1 methanol/oil molar ratio and 7 wt% catalyst dosage in the first use (93.50 wt% in the eleventh use). The kinetic study with Na 2 CO 3 @EFD was carried out, and it was found that the activation energy was 32.81 kJ/mol and the frequency factor was 3760.85 /min, lower than reported solid base catalysts, which suggested synthesized Na 2 CO 3 @EFD catalyst owned remarkable potential for industrial application in biomass energy conversion.
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