| The isothermal pyrolysis of 100 mg samples of cellulose (Whatman CF11), xylan (ex larch wood), lignin (lndulin AT), wood (Ponderosa pine sawdust), newsprint, 1% HCI washed newsprint and lignite (North Dakota) at pressures below 1 torr has been examined. Data are presented to describe the product yield as a function of time and temperature, for temperatures up to 465(DEGREES)C for cellulosic materials and up to 540(DEGREES)C for lignite. Pyrolysis occurs via an initial reaction followed by an isothermal reaction which can be modeled as first order in terms of remaining substrate, with tars and char forming by two competitive pseudo first order reactions. Cellulose was found to undergo an "incubation" period prior to rapid thermal degradation. For all other substrates, the initial reaction has been modeled as a zero order reaction.; At higher pressures (> 1 torr) tars undergo secondary decomposition. A one parameter model is developed to describe the effect of ambient pressure on tar yield for newsprint, wood and lignite.; Data are presented for tar enhancement due to dilute acid wash pretreatment for newsprint. Acid washing pretreatment removes inorganic impurities, reducing the catalytic effect favoring the dehyration reaction. Trace amounts of acid (up to 0.02 m eq/g) catalyze the depolymerization reaction, giving 40% more tars in low pressure pyrolysis than untreated newsprint. But, additional amounts of acid lead to lower tar yields. |
