Investigation of Pyrolysis of Hydrocarbons and Biomass Model Compounds Using a Micropyrolysis Flow Cell

Abstract

Hydrocarbon growth mechanisms based on a combination of small hydrocarbon fragments, such as C 2 /C 4 , have been postulated in high-temperature flames. However, there is considerable evidence of alternative pathways, especially in lower temperature regimes, in particular, the importance of resonance-stabilized radicals based on cyclopentadienyl (CPDyl) moieties. Further evidence of polycyclic aromatic hydrocarbon (PAH) growth mechanisms can be provided by analytical pyrolysis experiments using high-temperature flow cells. An analytical micropyrolysis flow cell method has been developed, enabling reactive pyrolysis of solid and liquid samples. This uses a SGE microflow cell pyrojector interfaced to a CDS 5200 series pyrolyzer in adsorbent mode for the product concentration, followed by gas chromatographyÀmass spectrometry (GCÀMS) or Fourier transform infrared (FTIR) analysis. The flow cell system enables residence time and stoichiometry to be varied. The benefits of the system over a filament pyrolyzer are demonstrated. A number of applications of this technique are presented to illustrate the potential of this system to investigate biofuel decomposition, PAH growth mechanisms, and soot formation from different hydrocarbon and oxygenated fuels. Evidence is obtained indicating that resonance-stabilized intermediates, especially CPDyl, are important in PAH growth mechanisms for a wide range of fuel types.

Effect of Temperature and Vapor Residence Time on the Micropyrolysis Products of Waste High Density Polyethylene

“…The product distribution at severe conditions is shifted predominantly to compounds with less than six carbons. The displayed results agree with previous studies reporting that at lower temperatures and VRTs there is a wide range of aliphatic hydrocarbons formed, mostly in the medium and high C number range. ,, Also, the aromatic compounds observed at 675 °C and 5.6 s, have been reported as indicators of extreme conditions during the pyrolysis process . The observed triplet of alkadiene, alkene, and alkane, in that ordered sequence, for each C number has also been reported before ,, from studies conducted at larger scale than micropyrolysis.…”

“…In addition to flow rate of inert gas in the TSMR, VRT can also be adjusted by modifying the length of the reactor surface covered by the heating tape or adjusting the inside diameter. Pyrolysis systems with a subsequent vapor degradation have been used to study PE thermal cracking ,,, and standard compounds degradation . These systems have demonstrated a promising scenario for the two-stage thermal cracking, as an alternative to catalytic degradation, with increasing gases and aromatics generation with raising temperature and VRT.…”

“…Temperature increase also reduces the frequency of radical transfer leading to β-scission occurring at the chain end, which produces gaseous alkenes. High temperatures also form MAHs by Diels–Alder reaction ,, or cyclization , followed by dehydrogenation, and PAHs through aryl–aryl coupling …”

Combustion and pyrolysis reactions of alkylated polycyclic aromatic compounds: The decomposition of 13C methylarenes in relation to diesel engine emissions

“…Methylated PAH are also found in the products of pyrolysis and combustion of pure hydrocarbon liquid fuels [4] and biofuels [5,6].…”

“…In the present study measurements were made using both engine as well as laboratory flow tube pyrolysis experiments [4,25]. The products of pyrolysis of 2-[ 13 C] methylnaphthalene and 9-[ 13 C] methylphenanthrene were studied with a flow cell reactor [24] with on-line analysis by GC-MS.…”