Autocatalysis and aryl-alkyl bond cleavage in 1-dodecylpyrene pyrolysis

Abstract

1-Dodecylpyrene (DDP) pyrolysis at 375-425 °C for 10-180 min led to 1-methylpyrene, 1-undecene, 1-ethylpyrene, and n-decane as the major products at low conversions. At higher conversions, pyrene and n-dodecane were the major products. Minor products included a series of n-alkanes, a-olefins, and alkyl-substituted pyrenes. The variations of the products' molar yields with substrate conversion suggested that the reaction pathways operative at low DDP conversions were analogous to those observed in alkylbenzene pyrolysis. However, a different pathway involving facile and apparently autocatalytic cleavage of the strong aryl-alkyl C-C bond was dominant at moderate and high DDP conversions. The kinetics of DDP disappearance were also consistent with autocatalytic decomposition. The present results suggest that thermal cleavage of aryl-alkyl C-C bonds in heavy hydrocarbon resources such as petroleum residua, asphaltenes, and coal might be more prevalent than previously thought.The majority of processes for converting and upgrading heavy hydrocarbon resources such as petroleum residua, asphaltenes, and coal, though nominally catalytic, operate at elevated temperatures where purely thermal reactions can contribute to the observed product spectra and kinetics. In fact, recent kinetics studies of direct coal liquefaction (Gollakota et al., 1985) and asphaltene hydroprocessing (Savage et al., 1988

Reactions of polycyclic alkylaromatics: Structure and reactivity

“…The reactors were routinely cleaned between experiments by soaking them in a 10% HNO, solution and then rinsing them with water and then acetone. Previous work (Savage et al, 1989) established that neither the cleaning procedure nor the reactor material altered the experimental results.…”

“…Two other reasons that the comparison of the neat pyrolysis kinetics remains equivocal are that the initial concentrations of the compounds were likely different at reaction conditions 'Savage and Klein (1987b) " Savage et al (1989) and that the compounds possessed alkyl chains with different lengths (4 to 12 carbon atoms). The concentrations differed because the compounds had different vapor pressures and liquid densities.…”

“…Discrimination between primary and secondary products was achieved by examining the variation of: 1. products' molar yields with reactant conversion and 2. products' selectivities with reactant conversion. We used the former approach in our previous alkylarene pyrolysis studies (Smith and Savage, 1991a,b;Savage et al, 1989), and the application of the latter method is illustrated here. This method, termed the Delplot Technique (Bhore et al, 1990), has been used successfully to resolve the reaction pathways for the pyrolysis of pentadecylbenzene (Savage and Klein, 1987a) and phenethyl phenyl ether (Klein and Virk, 1983), and the oxidation of noctane (Garcia-Ochoa et al, 1989).…”

“…These rates were calculated as the initial slope of the molar yield vs. time curve for both the arene and, when possible, for the corresponding n-alkane. Figure 11 displays the natural logarithm of the initial rate of aryl-alkyl bond cleavage as a function of the Dewar reactivity number of the alkylarenes used in this study and for compounds pyrolyzed previously (Savage et al, 1989;Savage and Klein, 1987b). The open symbols represent those rates calculated from the alkane, and the filled symbols represent rates calculated from the arene.…”

Slurry-Phase Batch Microreactor for Hydroconversion Studies

“…Furthermore, the reduced dimensions make flow micro-reactors unsuitable for residue or pyrolysis oil slurryphase reactions as solids (whether the catalyst particles or precipitates such as coke 24,31 ) rapidly foul the micro-channels and necessitate frequent shut down and cleaning 22,29,32 . For this reason, micro-reactors used for residue and pyrolysis oil upgrading are almost exclusively batch systems 21,23,24,31,[33][34][35][36] .…”