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A comprehensive transport model (conductive, convective and radiative heat transfer, convective mass transport) is applied to simulate the thermal decomposition of thermoplastic polymer/carbon nanotube nanocomposites and corresponding neat polymers (poly(methylmethacrylatye) (PMMA), polypropylene (PP), polystyrene (PS)). The flame retardant effectiveness of nanocomposites is confirmed and good quantitative agreement with measurements is shown.

The pyrolysis of particles of glucomannan, the main component of softwood hemicelluloses, is investigated in a fluidized-bed reactor. A first set of experiments is carried out for temperatures in the range 530-690K to determine yields and composition of products. The most abundant are char, water and carbon dioxide. The condensable organic fraction mainly consists of acetic acid, formic acid, hydroxypropanone, hydroxyacetaldehyde and furfuryl alcohol.

The acid catalyzed pyrolysis of corncobs is investigated for the production of furfural. The selected acidic catalysts are sulfuric acid (H2SO4), zinc chloride (ZnCl2) and ferric sulphate (Fe2(SO4)3). Experiments have been made at a heating temperature of 800K, by varying the amount of catalyst impregnated in the substrate. The maximum yields of FF are around 5¬6% for the three catalytic treatments (versus yields of 0.6% for un¬catalyzed pyrolysis), with potential further increase, following secondary degradation of the main anhydrosugars, up to 8.5% (H2SO4), 10% (Fe2(SO4)3) or 6.5% (ZnCl2)., Proceedings of the 20th European Biomass Conference and Exhibition, 18-22 June 2012, Milan, Italy, pp. 982-987

Thermogravimetric measurements in air of fir wood impregnated with diammonium phosphate in the concentration range 2-20% and heating rates between 5 and 20 K/minshowthe existence of three sequential stages: wood decomposition, induction and char oxidation. The additive causes an anticipation in the decomposition stage up to about 100 K, a reduction in the maximum rate up to a factor of three and an increase in the charred solid residue from about 30 to 60%. The total duration of the induction and oxidation stages is also increased. The experimental curves are interpreted by either a three-step mechanism (one reaction for each stage) or a seven-step mechanism (three reactions for decomposition and two reactions for the induction and oxidation stages). The estimated kinetic parameters are independent from the heating rate but vary with the diammonium phosphate concentration. However, for both mechanisms, the activation energies of the various steps remain practically constant except for the decomposition of the cellulose component or the decomposition step, depending on the complexity of the mechanism.

The acid-catalyzed pyrolysis of corncobs is investigated for the production of chemicals (in particular furfural) and bioproducts. Particles, preimpregnated with H2SO4 concentrations up to about 4% (dry sample mass basis) and predried at 343 K, are exposed in the form of a packed-bed at a heating temperature of 800 K. The gas release rate remains approximately constant, at a value about half with respect to the maximum detected for acid-free samples, for a large part of the process transients. Conversion times are roughly increased by 50% while reaction temperatures, on the average, become lower by about 20-40 K. Dehydrating and charring reactions become successively more favored suppressing the formation of condensable organic compounds.Adecay is observed in the yields of both some carbohydrates (hydroxyacetaldehyde, hydroxypropanone, furfuryl alcohol, etc.) and phenolics (phenol, guiacol, 4-methyguaicol, 4-ethylguaicol, syringol) although less steep for the latter. However, catalyst concentrations below 0.5% lead to maxima in the yields of levoglucosan, 5-hydroxymethylfurfural, and 1,6-anhydro-?-D-glucofuranose. Moreover, the production is significantly enhanced of levoglucosenone (from trace amounts up to 4.5%) and furfural (from 0.65% up to 5%) at catalyst concentrations around 1-2% and 2-3%, with 1,4:3,6-dianhydro-R-Dglucopyranose (maximum yield 0.65%) acting as a reaction intermediate. The yield of acetic acid remains constant at 4% up to catalyst concentration around 3%. Higher catalyst concentrations are associated with a rapid decline in the yields of all these organic compounds with the total amount of char, carbon dioxide, and water reaching 70%.

In this study, the oxidation of secondary biomass chars, generated from evaporation/decomposition of four bio-oil samples (BTG, Dynamotive, Ensyn, Pyrovac), is investigated under a kinetic control. Weight loss characteristics, consisting of the sequential stages of char devolatilization and oxidation, are qualitatively similar with those of chars produced from wood pyrolysis. However, reactivities are generally quantitatively lower, owing to the highly different morphological properties and the lower inorganic content. A four-step parallel mechanism (versus the two-step mechanism of wood char) describes well the integral and differential measurements for variable heating rates. The devolatilization stage includes three first-order rate reactions with activation energies of 84, 100, and 118 kJ/mol accounting for the release of volatile species amounting to 27-40% of the initial mass (versus about 15% of wood chars). An additional nonlinear step simulates the oxidation stage but requires sample-dependent activation energies (211, 174, 169, and 163 kJ/mol versus 183 kJ/mol of wood char).

The pyrolysis of a packed bed of fir wood particles, after impregnation with KOH, is investigated. For a heating temperature of 800 K, maximum variations in the pyrolysis characteristics are observed for KOH concentrations in wood below 1%. Decomposition temperatures become lower (35-70 K), and conversion times are rapidly more than halved. Also, the char, water, and gas yields increase (factors of 1.4, 1.6, and 1.7, respectively) at the expense of liquid-phase organic products. Levoglucosan presents a very steep decay, whereas the diminution in hydroxyacetaldehyde and acid acetic is much slower, and a wide zone of approximately constant values appears for hydroxypropanone. However, small quantities of KOH in wood (about 0.2-0.6%) are apt to increase the yields of furfuryl alcohol up to a factor 15 and some carbohydrates (3-ethyl-2-hydroxy- 2-cyclopentenone, 3-methyl-2-cyclopentenone, 1-hydroxy-2-butanone) and phenols (phenol, cresols, hydroquinone, guaiacol, isoeugenol-trans, isoeugenol-cis, 4-acetonguaiacol, 4-ethylguaiacol) up to factors of 2-6. Higher KOH concentrations cause a further increase in the yields of char and CO2 associated with a decay to very small yields of all of the organic compounds. Finally, increasing the heating temperature from 600 to 900 K (KOH concentration in wood of about 0.6%) essentially favors devolatilization and cracking of vapor-phase organic products with conversion times roughly reduced by a factor of 6.