Understanding the thermochemical conversion of biomass to overcome biomass recalcitrance

Kim, Kwang Ho

doi:10.31274/etd-180810-3934

Cited by 1 publication

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References 161 publications

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“…Radicals generated from the primary pyrolysis reactions can be trapped in the polyaromatic matrix of lignin [56], and stabilized by the delocalized unpaired electrons [57,58]. The major products from cellulose pyrolysis (levoglucosan and other light oxygenates) do not have unpaired electrons [59], and therefore, the radical concentrations in the char from the decay stage are low. The char prepared from softwood lignin at 1000 C with 1 s holding time showed a higher concentration of radicals than the wheat straw lignin char.…”

Section: Spin Radical Concentrationmentioning

confidence: 99%

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

Trubetskaya

Jensen

et al. 2016

Biomass and Bioenergy

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a b s t r a c tThe concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000 C) in biomass char have been studied. A roomtemperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7$10 16 and 1.5$10 18 spins g À1. The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 10 3 e10 4 K s À1. The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g ¼ 2.0026e2.0028) and PAH radicals (g ¼ 2.0027e2.0031) were formed.

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