Page 265 - Biofuels Refining and Performance

244 Chapter Eight

sewage sludge AS [61]. Peaks assigned by numbers correspond to the
aliphatic, unbranched saturated hydrocarbons. The peak appearing before
the n-alkane corresponds to the n-alkenes.
The predominant aliphatic nature of oils produced is readily ascer-
1
tained by NMR spectroscopy. Figure 8.21 depicts the H-NMR spectro-
gram of oil from DS with about 5% of aromatic protons.
Infrared spectroscopy (see Fig. 8.22) reveals the presence of C-H-
1
stretching frequencies at 2850–3000 cm . In addition, the spectrum
provides clear evidence of hydrogen bonding due to a broad absorption
1
band of 3350 cm . Thus, decarboxylation of lipids in the presence of
in situ catalysts is not complete. This is consistent with the higher vis-
cosities in comparison to diesel. A special loop reactor for recycling
catalytic activity to overcome these problems has been designed [62].
Hydrocarbons are derived from both lipids and proteins in the sewage
sludge in the presence of in situ catalysts. However, oil produced from
proteins under anaerobic LTC conditions is high in nitrogen and sulfur:
Amines, purins, and mercaptanes are trace contaminants that are
formed. Consequently, this oil smells and is a nuisance, and upgrad-
ing (e.g., over H-ZSM-5 as catalyst) is essential [64]. The useful oil is

2.26216 1.58385 1.24420 1.17452 1.12234 1.01315 1.00514 0.99071 0.08420 0.96417 0.92519 0.90611 0.83640 0.87784 0.85917 0.82083 0.79726 0.76995 0.75050

~95% alkanes
& alkenes

~5% arenes

4.582 95.418
9 8 7 6 5 4 3 2 1 0
ppm

1
Figure 8.21 H-NMR of oil from LTC of DS at T 400 C.