FUELS AND CHEMICALS FROM SEWAGE-SLUDGE .2. THE PRODUCTION OF ALKANES AND ALKENES BY THE PYROLYSIS OF TRIGLYCERIDES OVER ACTIVATED ALUMINA

Triolein, canola oil, trilaurin and coconut oil were pyrolysed over activated alumina at 450-degrees-C and atmospheric pressure. The liquid products were hydrocarbon mixtures which contained both alkanes and alkenes. I.r. spectra confirmed the absence of carbonyl groups in all the pyrolysed products. Decoupled C-13 n.m.r. supported this as well as showing the presence of thermodynamically unfavourable terminal double bonds. These were probably formed by a gamma hydrogen transfer mechanism in which the glycerol moiety together with the ester carbonyl group was lost. There were 14.3, 17.1, 10.1 and 13.4 carbon atoms per double bond, respectively in the liquid products of tiolein, canola oil, trilaurin and coconut oil pyrolysis. Gas chromatography showed some cracking of the hydrocarbon chains with a preference for C6 and C7 products from triolein and canola oil pyrolysis and C9 and C11 products from trilaurin and coconut oil pyrolysis, but otherwise a uniform distribution across the C6 to C16 mass range. These results are significant for the pyrolysis of the lipid fraction which can be isolated by the solvent extraction of sewage sludge, as well as to the pyrolysis of wastes from food processing industries.