Global Kinetic Rate Parameters for the Formation of Polycyclic Aromatic Hydrocarbons from the Pyrolyis of Catechol, A Model Compound Representative of Solid Fuel Moieties

Abstract

To obtain kinetic parameters on PAH formation relevant to solid fuels combustion, pyrolysis experiments have been conducted with catechol, a model fuel representing entities in coal and biomass. Catechol pyrolysis experiments were performed in a tubular-flow reactor at temperatures of 500−1000 °C and at a residence time of 0.4 s. PAH products were identified and quantified by high-pressure liquid chromatography with ultraviolet−visible diode-array detection and by gas chromatography with flame ionization and mass spectrometric detection. A pseudo-unimolecular reaction kinetic model was used to model the experimental yield/temperature data of 15 individual aromatics and of combinations of PAH grouped by structural class and ring-number. The modeling of the individual species' yields showed that the pseudo-unimolecular model agreed very well with the experimental data. E a values ranged from 50 to 110 kcal mol-1, generally increasing as the size of the aromatic product increased from one to five aromatic rings. The pseudo-unimolecular model also performed well in modeling the experimental yields of PAH grouped by structural class and ring number. The global kinetic analysis results for PAH grouped by ring number revealed that E a values increased in the following order: 2-ring < 3-ring < 4-ring < 5-ring < 6-ring. Their yields followed the reverse order: 2-ring > 3-ring > 4-ring > 5-ring > 6-ring. These trends of increasing E a and decreasing yield, as ring number is increased, are consistent with a mechanism for PAH growth involving successive ring buildup reactions.

Lignin pyrolysis reactions

“…These compounds are key intermediates for ring-growth reactions that produce PAHs. Ledesma et al [104] measured E a values for the formation of PAHs from catechol in the range of 50-110 kcal mol − 1 . The values increased for structures with different numbers of rings in the order, 2-rings <3-rings <4-rings <5-rings <6-rings.…”

An Innovative Agro-Forestry Supply Chain for Residual Biomass: Physicochemical Characterisation of Biochar from Olive and Hazelnut Pellets

“…The chemical structure of PAHs makes them highly resistant to biodegradation and oxidation [41]. The presence of PAHs in pyrolytic reactions above 700˝C is well established [42], although they can be produced in pyrolysis reactions of less than 700˝C at low concentration [43]. It is, therefore, critical to ensure PAH concentrations remain below the limits established by the EBC.…”

Effects of Driving Conditions on Diesel Exhaust Particulates

“…53,54 Despite different fuels, four studies examining combustion of catechol fuel, tobacco, and cellulose char pyrolysis consistently observed that concentrations of aromatic-structured, persistent free radicals peaked at a threshold temperature and then decreased with increasing combustion temperatures. [53][54][55][56] Figure 4 shows that under the full engine load, because the DEPs from the engine speed of 3000 rpm along with an exhaust temperature of 569°C (secondary x-axis) contained less persistent free radicals than that from the engine speed of 1800 rpm with an exhaust temperature of 497°C, the threshold temperature corresponding to the most abundant persistent free radicals would be lower than 569°C, resulting in the decreasing concentration of persistent free radicals with an increase in the exhaust temperature. Figure 5 shows that TPM was emitted from the individual driving conditions in a decreasing order of 3000 rpm/100% Ͼ 1800 rpm/100% Ͼ 3000 rpm/60% Ͼ 1800 rpm/60%.…”