High-temperature vapor detection of polycyclic aromatic
, Brian M. Cullum
, David L. Stokes
, Joel Mobley
, Gordon H. Miller
Mohammad R. Hajaligol
, Tuan Vo-Dinh
Advanced Monitoring Development Group, Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6101, USA
Philip Morris Research Center, Richmond, VA 23261-6583, USA
Received 15 June 2000; revised 25 January 2001; accepted 29 January 2001
Polycyclic aromatic hydrocarbons (PAHs) are generated from the incomplete combustion of organic matters in a wide variety of natural
and man-made materials, such as fuels. It is important to develop an analytical technique for rapidly monitoring PAH generation at high
temperatures during pyrolysis processes. This work describes a real-time and in situ technique using laser-induced ¯uorescence to detect
PAH vapors at elevated temperatures. We report ¯uorescence spectra of several typical PAH model compounds, such as pyrene, phenan-
threne and chrysene. We have also examined the temperature effects on PAH ¯uorescence spectra such as spectral shift, intensity and band
width. q 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Laser-induced ¯uorescence; PAHs; High temperature; Vapor; Pyrene; Phenanthrene; Chrysene
Polycyclic aromatic hydrocarbons (PAHs) are usually
generated from the incomplete combustion or pyrolysis of
organic matter in complex materials such as fossil fuels [1±
4]. The formation processes for PAHs also include catalytic
cracking of petroleum products and coal coking [2,4±7].
These processes usually occur at elevated temperatures
and under various environmental conditions, therefore lead-
ing to the formation of different PAHs . Better under-
standing of these pyrolysis processes will lead to a cleaner
combustion technology and thus reduce the PAH levels in
the atmosphere. Therefore, it is important to develop analy-
tical techniques capable of monitoring real-time and in situ
PAH generation in high-temperature combustion processes.
One such technique which is very sensitive is ¯uorescence
spectroscopy since most PAHs have very large absorption
cross-sections and high ¯uorescence quantum yields [9,10].
Although ¯uorescence spectroscopy could be very valuable
in the analysis of combustion and pyrolysis processes, little
data at present has been reported regarding vapor-phase
PAH ¯uorescence [11,12].
We have developed a nitrogen laser-induced ¯uorescence
system coupled with a temperature-controlled quartz
furnace system to measure PAH vapor ¯uorescence spectra
at temperatures ranging from 130 to 6508C. The ¯uores-
cence spectra of pyrene, phenanthrene, and chrysene at
elevated temperatures have been measured in this study,
since three and four ring structures represent basic building
blocks of PAHs of larger sizes. We describe the development
and application of instrumentation for the measurement of
high temperature vapor-phase PAHs in order to gain basic
knowledge of the changes in the ¯uorescence properties of
these PAHs over the temperature range of 130±6508CWe
have examined temperature effects on the ¯uorescence spectra
of PAHs. In addition, a comparison between the ¯uorescence
spectra of the three PAHs in the vapor phase and those same
PAHs in cyclohexane solutions is made.
2.1. High-temperature ¯uorescence spectrum measurement
To detect ¯uorescence spectra of PAHs at elevated
Fuel 80 (2001) 1819±1824
0016-2361/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
The submitted manuscript has been authored by a contractor of the US
Government under contract No. DE-AC05-00OR22725. Accordingly, the
USGovernment retains a nonexclusive, royalty-free license to publish or
reproduce the published form of this contribution, or allow others to do so,
for USGovernment purposes.
* Corresponding author. Tel.: 11-865-574-6249; fax: 11-865-576-7651.
E-mail address: firstname.lastname@example.org (T. Vo-Dinh).