FUELS AND CHEMICALS FROM SEWAGE-SLUDGE .3. HYDROCARBON LIQUIDS FROM THE CATALYTIC PYROLYSIS OF SEWAGE-SLUDGE LIPIDS OVER ACTIVATED ALUMINA

Toluene-extracted lipids (obtained by extraction with boiling toluene) from a dried raw Atlanta sewage sludge were pyrolysed over activated alumina at 450-degrees-C and atmospheric pressure. Pyrolysis yielded low-viscosity liquids (10.7-67.5 wt%), non-condensable gases (12.1-15.6 wt%), semi-solids (only at higher weight-hourly space velocity) and water. The liquid products were hydrocarbon mixtures which contained predominantly alkanes. Infrared spectra, as well as proton-decoupled C-13 nuclear magnetic resonance, confirmed the absence of carbonyl groups in the pyrolysed liquid products; showing that even the carboxylic acids, the major component of the separated lipid fraction, did not survive the pyrolysis reaction. Gas chromatography of the liquid products showed a uniform hydrocarbon distribution across the C6-C20 mass range. Non-condensable gases consisted of carbon dioxide, carbon monoxide, methane, ethane, ethene and C3-C5 compounds. This process resulted in rejection of both nitrogen and sulfur. The lipid extract only contained 1 wt% of the nitrogen and 16 wt% of the sulfur in the sludge. But these elements were reduced by a further 84% in the liquid product with respect to the lipid. The pyrolysed liquid contained 0.08 wt% nitrogen and 0.22 wt% sulfur. This liquid has a great potential to be used as diesel fuel, heating fuel and chemical feedstocks.