H₂SO₄-Catalyzed Pyrolysis of Corncobs

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. A decay 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-β-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-α-d-glucopyranose (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%.

Effects of four types of dilute acid washing on moso bamboo pyrolysis using Py–GC/MS

“…In comparison to R-bamboo, The absolute peak areas of furfurals obtained from R-bamboo and acid washed samples are presented in Fig 3B. It can be seen that the absolute peak areas of furfural from acid washed bamboo increased, whereas those of 2(3H)-furanone, 5-methyl-and 2,3-dihydrobenzofuran showed a contrary tendency. Previous study has demonstrated that furfural could be primarily formed by the dehydrations of pentosyl residues contained in hemicellulose and D-glucosyl residues presented in cellulose, and both of the two dehydration reactions were promoted by the residual hydrion from acids after acid washings (Branca et al, 2010). The absolute peak area of furfural from HF-bamboo was only slightly higher than that from R-bamboo probably due to its mild acidity.…”

Effects of the Torrefaction Conditions on the Fixed-Bed Pyrolysis of Norway Spruce

“…In particular, hexoses (galactoglucomannan), the major softwood hemicelluloses, give 5-HMF as one of the main degradation products, while pentoses (xylose, arabinose), constituting the main components of hardwood and hemicellulose residues, mainly degrade to FF. 33,35 Moreover, FF is also a secondary degradation product of other furanics, such as 5-MF and 5-HMF. 33,35 It is possible that the initial zone of constant yield observed in some cases is attributable to the increase in the percentage of cellulose in the sample following the disappearance of the hemicellulose during the pretreatment.…”

Selective Production of Levoglucosenone from Catalytic Fast Pyrolysis of Biomass Mechanically Mixed with Solid Phosphoric Acid Catalysts

“…H 3 PO 4 has been confirmed to be a promising catalyst for selective production of LGO [33,42]. In addition, H 2 SO 4 [32,43] and ionic liquid [31] have also been found to be capable for LGO production. Nevertheless, many problems will be encountered during the utilization of these liquid catalysts.…”