Hydrogen-Transferring Pyrolysis of Long-Chain Alkanes and Thermal Stability Improvement of Jet Fuels by Hydrogen Donors

• Published in: Industrial & engineering chemistry research 1994-03, Vol.33 (3), p.548-557
• Main Authors: Song, Chunshan, Lai, Wei Chuan, Schobert, Harold H
• Format: Article
• Language: English
• Subjects: 02 PETROLEUM; 023000 - Petroleum- Properties & Composition; ALKANES; Applied sciences; CHEMICAL REACTION KINETICS; CHEMICAL REACTION YIELD; CHEMICAL REACTIONS; Crude oil, natural gas and petroleum products; DECOMPOSITION; Energy; Exact sciences and technology; FUELS; HYDROCARBONS; HYDROGEN TRANSFER; JET ENGINE FUELS; KINETICS; ORGANIC COMPOUNDS; Petroleum products, gas and fuels. Motor fuels, lubricants and asphalts; PYROLYSIS; REACTION KINETICS; STABILITY; THERMAL DEGRADATION; THERMOCHEMICAL PROCESSES; YIELDS
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie00027a011

Hydrogen-transferring pyrolysis refers to the thermal decomposition of hydrocarbons in the presence of hydrogen donors. Relative to the pyrolysis of pure n-tetradecane (C[sub 14]H[sub 28]) at 450 C, adding 10 vol % of H-donor tetralin suppressed n-C[sub 14] conversion by 68 % after 12 min of residence time, by about 66% after 21 min, and by 37% after 30 min. The presence of tetralin not only inhibited the n-C[sub 14] decomposition, but also altered the product distribution. The decomposition and isomerization of primary radicals are strongly suppressed, leading to a much higher ratio of the 1-alkene to n-alkane with 12 carbon atoms and slightly higher alkene/alkane ratio for the other product groups. The overall reaction mechanism for the initial stage of hydrogen-transferring pyrolysis is characterized by a one-step [beta]-scission of secondary radical followed by H-abstraction of the resulting primary radical. Moreover, desirable effects of the H-donor are also observed even after 240 min at 450 C, especially for inhibiting solid deposition. The authors also examined the effect of tetralin addition on the deposit formation from a paraffinic jet fuel JP-8 which is rich in C[sub 9]-C[sub 16] long-chain alkanes, and an aromatic compound, n-butylbenzene. Adding 10 vol % tetralin to a JP-8 jet fuel, n-C[sub 14], and n-butylbenzene reduced the formation of deposits by 90% (from 3.1 to 0.3 wt %), 77 % (from 3.0 to 0.7 wt %), and 54 % (from 5.6 to 2.6 wt %), respectively. These results suggest that, by taking advantage of H-transferring pyrolysis, hydrocarbon jet fuels may be used at high operating temperatures with little or no solid deposition.