Biomass pyrolysis: thermal decomposition mechanisms of furfural and benzaldehyde.
The thermal decompositions of furfural and benzaldehyde have been studied in a heated microtubular flow reactor. The pyrolysis experiments were carried out by passing a dilute mixture of the aromatic aldehydes (roughly 0.1%-1%) entrained in a stream of buffer gas (either He or Ar) through a pulsed, heated SiC reactor that is 2-3 cm long and 1 mm in diameter. Typical pressures in the reactor are 75-150 Torr with the SiC tube wall temperature in the range of 1200-1800 K. Characteristic residence times in the reactor are 100-200 μsec after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 μTorr. Products were detected using matrix infrared absorption spectroscopy, 118.2 nm (10.487 eV) photoionization mass spectroscopy and resonance enhanced multiphoton ionization. The initial steps in the thermal decomposition of furfural and benzaldehyde have been identified. Furfural undergoes unimolecular decomposition to furan + CO: C4H3O-CHO (+ M) → CO + C4H4O. Sequential decomposition of furan leads to the production of HC≡CH, CH2CO, CH3C≡CH, CO, HCCCH2, and H atoms. In contrast, benzaldehyde resists decomposition until higher temperatures when it fragments to phenyl radical plus H atoms and CO: C6H5CHO (+ M) → C6H5CO + H → C6H5 + CO + H. The H atoms trigger a chain reaction by attacking C6H5CHO: H + C6H5CHO → [C6H6CHO]* → C6H6 + CO + H. The net result is the decomposition of benzaldehyde to produce benzene and CO.
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
AnGayle K
AK
Vasiliou
Jong Hyun
JH
Kim
Thomas K
TK
Ormond
Krzysztof M
KM
Piech
Kimberly N
KN
Urness
Adam M
AM
Scheer
David J
DJ
Robichaud
Calvin
C
Mukarakate
Mark R
MR
Nimlos
John W
JW
Daily
Qi
Q
Guan
Hans-Heinrich
HH
Carstensen
G Barney
GB
Ellison
D001547:Benzaldehydes / Q000737:chemistry*; D018533:Biomass; D005662:Furaldehyde / Q000737:chemistry*; D006358:Hot Temperature; D013058:Mass Spectrometry / Q000379:methods; D013055:Spectrophotometry, Infrared / Q000379:methods
D001547:Benzaldehydes; D005662:Furaldehyde; C032175:benzaldehyde