Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures
| Autor: | Mogens L. Andersen, Anna Trubetskaya, Peter Glarborg, Peter Arendt Jensen, Anker Degn Jensen, Flemming Hofmann Larsen |
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| Přispěvatelé: | Danish Strategic Research Council |
| Rok vydání: | 2016 |
| Předmět: |
Alkali
020209 energy Radical Biomass Energy Engineering 02 engineering and technology Photochemistry Char law.invention Kemiska processer law Electron spin resonance spectroscopy 0202 electrical engineering electronic engineering information engineering Organic chemistry Physics::Chemical Physics Spectroscopy Electron paramagnetic resonance Waste Management and Disposal Renewable Energy Sustainability and the Environment Chemistry Forestry 021001 nanoscience & nanotechnology Alkali metal Characterization (materials science) Energiteknik Chemical Process Engineering 0210 nano-technology Fast pyrolysis Agronomy and Crop Science Pyrolysis |
| Zdroj: | Biomass and Bioenergy. 94:117-129 |
| ISSN: | 0961-9534 |
| DOI: | 10.1016/j.biombioe.2016.08.020 |
| Popis: | The 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 room-temperature 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 7·1016 and 1.5·1018 spins g−1. 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 103–104 K s−1. 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 = 2.0026–2.0028) and PAH radicals (g = 2.0027–2.0031) were formed. The authors would like to acknowledge the financial support that they received for this project from Danish Strategic Research Council (Grant Nr. DSF-10-093956), DONG Energy and Vattenfall. We also thank Professor Spliethoff and Markus Steibel (TU Munich) for the support with the entrained flow reactor experiments, Jesper Harholt (Carlsberg Laboratory) and Søren Talbro Barsberg (University of Copenhagen, Department of Geosciences and Natural Resource Management) for assisting with the biomass compositional analysis and for the fruitful discussions. peer-reviewed 2018-09-06 |
| Databáze: | OpenAIRE |
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