The reactive processes that occur during the laser initiation of aluminum/iron(III) oxide metastable intermolecular composites (MIC) have been studied by laser-induced desorption ionization time-of-flight mass spectrometry. The ions observed in the plume from the aluminum show fragments from the ablation of the oxide coating and from the metal core. Ablation of the iron oxide component consists primarily of pure iron species such as [Fe] + and [Fe 2 ] + and small oxides such as [FeO] + and [Fe 2 O] + ions. In smaller quantities, metal oxide clusters that are either oxygen deficient, [Fe(FeO) x ] + , or oxygen equivalent, [(FeO) x ] + , are observed. When the thermite composite is initiated, mixed metal species are observed in the plume, which correspond to the aluminum substitution analogues of the iron oxide clusters, specifically, [FeAl 2 O 3 ] + , [AlFe 2 O 3 ] + , and [AlFe 2 O 2 ] + . Notably, the amounts of these mixed metal products that form are inversely proportional to the size of the aluminum particles. This suggests that the decrease in ignition time observed in MIC materials is due to the more facile liberation of reactive metallic aluminum when the particle size is small.
Efforts are conducted worldwide to accelerate conversion of biomass into coal by chemical means in view of environmental, technological and socio-economie issues. With respect to the challenge of climate change, dehydration of carbohydrates can contribute to a negative atmospheric carbon dioxide balance by transferring carbon from the atmospheric cycle to the geologica! cycle. Besides conventional charcoaf formation by partiaf oxidation of dry wood at temperatures above 600 °C, the rediscovered solvo-thermal process of high pressure hydrothermal carbonization (HTC) and the thermo-catalytic low temperature conversion (LTC) process at atmospheric pressure are potential techniques for enhanced carbonization. The present investigation at laboratory stage compares three different experimental arrangements: Thermogravimetry (TG) simulating a LTC process at micro scale, vertical tube reactor (LTC) and a micro high pressure autoclave (HTC) using hemicellulose, cellulose, lignin and spent grains tor production of carbon-enriched substances at temperatures between 180 °C and 400 °C. Results of mass balance and concentration of carbon in the solid products are compared at the same operating temperature. Below T = 260 °C materials produced by HTC treatment show a higher degree of carbonization. However, a temperature increase of 40 •e in LTC reactors compared to HTC gives rise to the same amount of carbonization. Up to 240 °C little difference in functional groups of substrates and corresponding conversion products is shown in infrared spectra. Solid-state 13 C-NMR analysis reveals that increased sp 2 -hybridization of C-atoms can only be seen in LTC-treatment at 400 °C. Consequences may be drawn in view of fertilizing soil additive and green coal tor incineration.
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