Investigation of n-pentane pyrolysis at elevated temperatures and pressures in a variable pressure flow reactor

Abstract

Thermally cracking fuel in a fuel processing facility or undergoing pyrolysis in the anode channel of a fuel cell can lead to coke deposition. The formation of coke occurs via chemical kinetic pathways that are largely dependent on poly aromatic hydrocarbons (PAHs). The formation of PAH's largely depends on species which include ethylene, acetylene, butadiene, benzene and toluene. Pentane is a relatively simple structure for modeling purposes, yet large enough that it produces some of the relevant chemistry of real fuels. Experiments were conducted in a newly designed variable pressure flow reactor (VPFR) built to process both liquid and gaseous reactants at pressures to 4.0 MPa and temperatures to 1373 K. The VPFR was initially validated via ethane pyrolysis experiments and comparing the results with existing literature data. Pentane experiments were done over a range of temperatures (923 K -1073 K), pressures (1 -2.0 MPa) and residence times (30 ms -40 s). The product selectivity appeared to be greatest influenced by pressure and level of fuel conversion. Pressure increases ethylene production but has an inverse effect on ethane production. Soot precursors appeared at higher levels of conversion. The results of the experiments were compared to an existing chemical kinetic mechanism with good agreement.

Heat-Flow Measurements for n-Hexane Reactions on H-ZSM-5 and H(Zn)-ZSM-5: Implications for Endothermic Reforming in Hypersonic Aircraft

“…It is important to reconcile the above conclusions with other reports which have found acid-catalyzed cracking reactions to be endothermic. One possibility is that the endothermic reactions in previous work were actually the result of homogeneous pyrolysis . Pyrolysis of alkanes can produce significant quantities of ethylene, which would be highly desirable for this application.…”

“…The homogeneous reactions will only be important at higher temperatures, a primary reason we chose to work at temperatures below 800 K. In the work of Huang et al, homogeneous, endothermic reactions with n -octane as fuel became significant above ∼873 K, even at high fuel flow rates. In another example, Saldana and Bogin reported that 10% of n -pentane is converted in 0.6 s at 923 K …”

“…One possibility is that the endothermic reactions in previous work were actually the result of homogeneous pyrolysis. 18 Pyrolysis of alkanes can produce significant quantities of ethylene, which would be highly desirable for this application. The homogeneous reactions will only be important at higher temperatures, a primary reason we chose to work at temperatures below 800 K. In the work of Huang et al, 1 homogeneous, endothermic reactions with n-octane as fuel became significant above ∼873 K, even at high fuel flow rates.…”

“…The homogeneous reactions will only be important at higher temperatures, a primary reason we chose to work at temperatures below 800 K. In the work of Huang et al, 1 homogeneous, endothermic reactions with n-octane as fuel became significant above ∼873 K, even at high fuel flow rates. In another example, Saldana and Bogin reported that 10% of npentane is converted in 0.6 s at 923 K. 18 It is interesting to compare H(Zn)-ZSM-5-catalyzed, endothermic reforming to homogeneous endothermic reforming. The catalyzed reactions occur at lower temperatures, implying that heat from fuel reactions can be removed at lower temperatures.…”

Higher Activity Leading to Higher Disorder: A Case of Four Light Hydrocarbons to Variable Morphological Carbonaceous Materials by Pyrolysis

“…Usually, the temperature for manufacturing carbonaceous materials ranges from 1000 to 4000 K, in the cases of arc discharge, CVD, laser ablation, pyrolysis, , and combustion. , The high temperature contributes to the atomic C formation from initial reactants. Thus, the nucleation and growth mechanisms of carbonaceous materials at high temperature can simply be seen as the self-assembly of atomic C. For this, many kinetic models have been developed to describe the pyrolysis of hydrocarbons. − Nevertheless, these models were employed to compare and fit the elementary reactions with experimental observations to determine dominant reactions in the total conversions alone and cannot provide any dynamic detail at the atomic level. Using reactive molecular dynamics (RMD), our recent work indicated that the pyrolysis product of CH 4 is an orderly cavity-like carbonaceous material as a possible precursor of CNTs, while that of acetylene (C 2 H 2 ) is a disorderly C black .…”