Effect of autohydrolysis on hemicellulose extraction and pyrolytic hydrogen production from Eucalyptus urograndis

Abstract

Ensuring environmental and social-economic sustainability in the use of materials from lignocellulosic biomass requires their fractionation and valorization of their main components. In this work, we used Eucalyptus urograndis wood to obtain chemicals and energy. The raw material was characterized in chemical terms and then subjected to autohydrolysis under variable operating conditions to optimize the extraction of hemicellulose derivatives relative to cellulose. The kinetics of the pyrolysis process was modeled in terms of activation energy and hydrogen production. Using temperatures in the range of 180-190°C and treatment times in the range of 15-30 min allowed more than 74.5% of all hemicellulosic components in the raw material to be selectively extracted into the liquid post-hydrolysis phase, more than 90% of all glucan to remain in the solid phase and up to 27.8% of lignin to be removed. The thermal behavior of solid fraction was examined by thermogravimetric analysis, using variable heating rates under a nitrogen atmosphere, and the activation energy can be estimated by using the Flynn-Wall-Ozawa method. Based on the results, the pyrolysis of E. urograndis can be modeled as a first-order reaction. The activation energy (E a) at a fractional conversion α between 0.3 and 0.7 was 183 to 199 KJ mol −1 for the raw material, whereas that for the solid residue from autohydrolysis ranged from 179 to 186 kJ mol −1 at same fractional conversion when operational temperature in autohydrolysis was upper 185°C. Based on the results, using temperatures above 180°C and times of 15 min or longer [i.e., operating at the (0,0) experimental point for the autohydrolysis process] in combination with degrees of conversion from 0.3 to 0.8 reduced the activation energy of the pyrolysis process in relation to the raw material by up to 12% and removed hemicellulose by more 74.5% from it. In parallel, the comparative analysis of the E a values and the composition of the pyrolysis gas obtained showed a negative relationship between E a and the amount of hydrogen produced.

Kinetic and hydrogen production analysis in the sequential valorization of a Populus clone by cold alkaline extraction and pyrolysis

“…The maximum proportion of hydrogen obtained, in volume, from the post-CAE solid phases ranged from 9.15 to 19.51%, so it was up to 15.57% greater than that provided by the raw material. These results are consistent with previously reported values for species such as Eucalyptus urograndis , where authohydrolysis provided amounts of hydrogen up to 8% greater than the raw material 33 . Similary, the application of acid hydrolysis to Leucaena leucocephala resulted in increased hydrogen production 53 .…”

“…In this work, we examined the potential of the process for obtaining energy and a high added value product: hydrogen. Removing most of the hemicellulose fraction and part of the polyphenol fraction decreased the activation energy of the pyrolysis process 16 , 33 , thereby presumably facilitating it. It should be noted that, as shown for treatments other than CAE, the operating conditions —or rather, their combination—influence the activation energy and kinetics of the thermal treatment 54 .…”

“…Ligneous biomass has been found to provide more hydrogen than agricultural residues 32 . Thus, Loaiza et al 33 found extracting hemicelluloses from Eucalytpus urograndis by pyrolysis to provide solids whose pyrolysis led to a decreased activation energy and increased hydrogen production (6–8%) relative to the untreated, raw material.…”

Lignocellulosic Biomass for the Fabrication of Triboelectric Nano-Generators (TENGs)—A Review

“…There are many methods of hemicellulose extraction [27] that have been used and which do not have a significant environmental impact. These methods include hydrothermal extraction [55,56] and steam explosion [57,58]. Each treatment shows an extraction rate (ER) of 40-80% and 50-80%, respectively.…”