Establishing the Maximum Carbon Number for Reliable Quantitative Gas Chromatographic Analysis of Heavy Ends Hydrocarbons. Part 3. Coupled Pyrolysis-GC Modeling

Diana M. Hernandez-Baez, Alastair Reid, Antonin Chapoy, Bahman Tohidi, Roda Bounaceur

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Abstract

The purpose of this research work is to determine the maximum single carbon number (SCN) which can be reliably quantified using High Temperature Gas Chromatography (HTGC) analysis of heavy oil hydrocarbons, accounting for (i) thermal cracking risk and (ii) the non/incomplete elution. To that end, an in-house coupled numerical Pyrolysis-GC model has been developed, capable of calculating the degree of elution and of simulating the migration, partitioning, and pyrolysis conversion of a mixture of 11 heavy n-alkanes spanning the range from nC14H30 to nC80H16 throughout the GC column. On the basis of this model and using a commonly used column configuration and temperature program, two conclusions have been made: (i) half of the mass injected of nC80 thermally decomposed before nC70 has eluted, suggesting a possible coelution of both nC70 and the pyrolysis products of nC80 and therefore making the HTGC analysis of nC70 and heavier n-alkanes no longer reliable, and (ii) alkanes heavier than nC70 take progressively longer to elute completely from the column, compromising the resolution of the peaks, i.e., nC70 takes 2.5 min and nC80 takes 8.5 min. Moreover, nC80 remained 12.9 min in the isothermal plateau before complete elution, implying that the nC80 peak will be overlooked and masked by the FID plateau signal, in combination with column bleed products. Therefore, in the case study the maximum reliable SCN which can be quantitatively analyzed with HTGC will be the lighter components than nC70.
Original languageEnglish
Pages (from-to)2045–2056
Number of pages12
JournalEnergy and Fuels
Volume33
Issue number3
Early online date26 Feb 2019
DOIs
Publication statusPublished - 21 Mar 2019

Keywords

  • HTGC
  • heavy ends hydrocarbons characterization
  • pyrolysis
  • thermal cracking

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology

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