K_2SiO_3_C颗粒催化大豆油酯交换制备生物柴油_英文(5)

1596 催 化 学 报 Chin. J. Catal., 2011, 32: 1592–1596

In order to study the stability of the K2SiO3/C catalyst, the samples were recovered by simple decantation. The remaining catalyst in the reactor was used to catalyze the next batch of soybean oil. A decline was observed in the conversion to methyl esters from 96.6% to 57.9%, indicat-ing the decrease of catalytic activity. This lowered activity may be explained by the dissolution of K species in the het-erogeneous K2SiO3/C catalyst. Glycerol covering of the surface of catalyst was also considered as the reason for the activity loss. The stability of the K2SiO3/C catalyst was bet-ter than that of a KOH/NaX [18] catalyst and KOH/MgO catalyst [19]. After a recycling experiment, it was found that the catalytic activity of the KOH/NaX catalyst and KOH/MgO catalyst decreased to 48.7% biodiesel conver-sion and 26.45% biodiesel yield, respectively.

The solubility of the catalyst was also a very important factor that should be taken into account to correctly interpret the performance and assess its practical use. This was a very important issue since neutralization and washing steps of the biodiesel produced would be necessary if any metal was found in it. Then, the possible advantage of using the het-erogeneous catalyst for this process would be nullified. The results showed that only small quantities (free K+ concen-tration was 3.1 ppm) existed in the biodiesel. The results obtained proved that the K2SiO3/C catalyst prepared has good potential for the biodiesel production from soybean oil.

high energy efficiency to give a faster reaction rate to shorten the reaction time.

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3 Conclusions

The K2SiO3/C catalyst was prepared by an impregnation method. K2SiO3 was well distributed on the surface of the carbon particle and it was an effective base for the transesteri cation reaction. Furthermore, the K2SiO3/C catalyst has good microwave absorption ability and showed