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Frontiers of Environmental Science & Engineering

Front. Environ. Sci. Eng.    2017, Vol. 11 Issue (2) : 3
Challenge of biodiesel production from sewage sludge catalyzed by KOH, KOH/activated carbon, and KOH/CaO
Xuemin Wu1,Fenfen Zhu1(),Juanjuan Qi1,Luyao Zhao2,Fawei Yan1,Chenghui Li1
1. School of Environment and Natural Resources, Renmin University of China, Beijing 100872, China
2. Shougang Research Institute of Technology, Beijing 100043, China
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The preparation reactions were catalyzed by base solid catalysts.

The preparation reactions were catalyzed by two loaded catalysts and KOH.

KOH/activated carbon was a better catalyst for biodiesel production.

The considerable compounds content, abundance, and low costs involved has led to the proposal to use sewage sludge as raw material for biodiesel production. The transesterification reaction is catalyzed using an acid catalyst instead of base catalysts because of the high free fatty acid concentration. However, the use of a base catalyst, particularly a solid base catalyst, has certain advantages, including faster reaction speed and easier separation. In this study, we utilize in situ transesterification by base catalyst (KOH, KOH/activated carbon (AC) and KOH/CaO) with sewage sludge as raw material. Many conditions have been tested to increase biodiesel yield through single-factor tests, including mass fraction and catalyst dosage. Preliminary experiments have optimized reaction time and temperature. However, the three catalysts did not work better than H2SO4, which had a maximum yield of 4.6% (dry sewage sludge base) considering the purity by KOH, KOH/CaO, and KOH/AC. The features of the catalyst were analyzed using XRD, BET and SEM. As to BET of KOH/AC and the good spiculate formation of KOH crystal appears to be essential to its function. As for KOH/CaO, the formation of K2O and absorption points is likely essential.

Keywords Biodiesel      Sewage sludge      Base catalyst      In situ transesterification     
Corresponding Authors: Fenfen Zhu   
Issue Date: 23 March 2017
 Cite this article:   
Xuemin Wu,Fenfen Zhu,Juanjuan Qi, et al. Challenge of biodiesel production from sewage sludge catalyzed by KOH, KOH/activated carbon, and KOH/CaO[J]. Front. Environ. Sci. Eng., 2017, 11(2): 3.
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Xuemin Wu
Fenfen Zhu
Juanjuan Qi
Luyao Zhao
Fawei Yan
Chenghui Li
Fig.1  Diagram of experimental set-up

1. water bath, 2. Thermometer, 3. mechanical agitator, 4. condenser pipe,

5. circulating water channel, 6. water pump, 7. separating funnel, 8. vacuum pump, 9. rotary evaporator

items/% BET/(m2·g1) aperture/nm pore volume/(mL·g1)
42.8 7.60 7.45 0.0101
50 0.94 9.91 0.0055
55.5 0.58 9.88 0.0042
63.6 0.51 10.08 0.0033
69.2 0.89 25.99 0.0115
Tab.1  Table 1(a) Surface areas of KOH/AC
items/% BET/(m2·g1) aperture/nm pore volume/(mL·g1)
5.1 1.02 12.85 0.0062
6.0 0.05 15.60 0.0062
11.1 0.78 15.25 0.0061
12.3 0.93 11.15 0.0046
12.6 1.11 19.24 0.0127
15 1.05 15.43 0.0071
Tab.2  Table 1(b)Surface areas of KOH/CaO
Fig.2  XRD spectra of KOH/CaO with different amount of KOH
Fig.3  SEM image of catalysts of KOH/CaO and KOH/AC: (a) SEM image of 6.0% KOH/CaO, (b) SEM image of 15% KOH/CaO, (c) SEM image of 12.6% KOH/CaO, (d) SEM image of 12.3% KOH/CaO, (e) SEM image of CaO, (f) SEM image of 42.8% KOH/AC, (g) SEM image of 55.5% KOH/AC, (h) SEM image of 63.6% KOH/AC, (i) SEM image of AC, (j) SEM image of AC
Fig.4  EDS images of catalysts of 15% KOH/CaO (a) and 11.1% KOH/CaO (b)
Fig.5  CO2-TPD experiments results: (a) CO2-TPD profiles of 6% KOH/CaO, (b) CO2-TPD profiles of 11.1% KOH/CaO, (c) CO2-TPD profiles of 15% KOH/CaO, (d) CO2-TPD profiles of 55.5% KOH/AC, (e) CO2-TPD profiles of 69.2% KOH/AC
Fig.6  Biodiesel yield from sewage sludge by different loading amount and dosage of catalysts using KOH/AC (a), KOH/CaO (b) and KOH (c)
Fig.7  FAMEs composition obtained from in situ transesterification catalyzed by KOH/AC (a), KOH/CaO (b) and KOH (c)
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