Page 266 - Biofuels Refining and Performance

Cracking of Lipids for Fuels and Chemicals 245

100
Air peak
96
3344
1707
Transmission (%) 88
92

84 2853

80 2923
4000 3200 2400 1800 1400 1000 540
Wave number, cm −1
Figure 8.22 Infrared spectrum of oil from DS shows associated –OH and –NH
1
bonds (3350 cm ) from the remaining carboxylic acids R-COOH or amides
R-CONH 2 [63].

produced from lipids. When sewage sludge was spiked with triolein,
representative of unsaturated triglycerides, the compound did not sur-
vive the LTC [65]. As a result, sludge was extracted with toluene using
a Soxleth extraction method to yield 12 wt.% lipids. Pyrolysis of sewage
sludge lipids over activated alumina produced liquid hydrocarbons
containing mostly alkanes [65]. Even the carboxylic acid fractions of
the lipids that were separated were completely converted. This is in
contrast to direct sewage sludge LTC, where long-chain carboxylic
acids are detectable in the IR spectrum (see Fig. 8.22). The reason is
the lower content of catalytically active in situ material. Pyrolyzed
liquid products from sewage sludge lipids contain virtually no nitro-
gen or sulfur (see Table 8.10). Only this liquid has a potential for use
as a base for commercial fuels [65].

TABLE 8.10 Elemental Composition of Original Dried Sludge, Extracted
Lipids, and Pyrolyzed Liquid Product
Component C, % H, % O, % N, % S, % Ash, %
Original sludge 39.5 6.0 26.1 6.00 0.7 20.5
Extracted lipids 72.2 10.7 14.2 0.35 0.85 0.6
Liquid product 86.6 13.5 0.0* 0.08 0.22 0.0*
*
By difference.