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%.
H2SO4-Catalyzed Pyrolysis of Corncobs
Branca C;
2011
Abstract
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%.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.