Asphaltene Characterization during Hydroprocessing by Ultrahigh-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Abstract

Asphaltenes have a significant impact on the hydroprocessing of residues because they adversely affect the overall rate of hydroprocessing reactions. They also act as coke precursors, leading to catalyst deactivation. Understanding the changes of asphaltenes upon conversion can provide essential clues to the development and optimization of residue conversion processes. In this work, we use ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (positive-ion mode atmospheric pressure photoionization) to follow asphaltene changes during the hydroprocessing of a residue. Asphaltenes were extracted from the feed and from two different products sampled at various times during the run. Results indicate that intensities for hydrocarbon classes and N-containing classes increase for the processed asphaltenes, while the abundance of S classes decreases. Similar results are found when the number of peak assignments is compared. The average double-bond equivalent (DBE) increases as a function of time on stream, which is usually associated with cyclization and aromatization reactions. However, the disappearance of molecules with low DBE as well as molecules with large DBE points to preferential cracking/ hydrogenation of molecules in both regions. A small decrease in average molecular sizes is observed as a function of time on stream. In general, molecular size distributions for different DBEs are narrower for the products than for the feed. The distributions also point to the disappearance of the largest molecules from the products in accordance with the preferential cracking previously reported for large molecules under hydroprocessing conditions. Analyses of the more abundant classes revealed trends that vary depending upon the type of heteroatoms as well as their relative amount within the molecules.

Asphaltenes: Separations, structural analysis and applications

“…The reduction of asphaltene molecular weight, molecular size and H/C atomic ratio was caused by the rupture of C-C bonds in the molecules and alkyl chains during the hydroprocess [190] . A series of reactions of cycloalkane aromatization, hydrocracking, and heteroatom elimination happened simultaneously under hydroprocessing [174,191] . Changing temperature was thought to be the most cost-effective way to control the process.…”

“…XRD and NMR founded that, with the temperature increase, L α , d m , total http://engine.scichina.com/doi/10.1016/j.jechem.2018.10.004 carbon number and average alkyl chain length decreased, while f α and aromatic carbon number increased [190] . The heteroatom removal usually contains hydrodesulfurization (HDS) [29,191,192] , hydrodenitrogenation (HDN) [12,191,193] , and hydrodemetallization (HDM) [24,192] , which is not as easy as desirable since the nucleus system remained with and/or without heteroatoms. Singlelump model was more adequate than Langmuir-Hinshelwood (L-H) models for specific asphaltenes [193] .…”

Thermal Transformations of Asphaltenes at a Temperature of 120 °C

“…При этом базовые для переработки тяжелого углеводородного сырья термические процессы не теряют своей актуальности и продолжают развиваться [13][14][15]. Поведение асфальтенов при облагораживании тяжелого углеводородного сырья во многом определяет эффективность процесса в целом, а также состав образующихся продуктов, в связи с чем изучение данных аспектов представляет огромный интерес [16][17][18][19][20][21]. Зачастую проводится термическая или термокаталитическая обработка собственно асфальтенов для оценки их реакционной способности и направленности превращений без влияния прочих компонентов нефти.…”

Izuchenie termicheskoy stabilnosti neftyanykh asfaltenov metodom differentsialnoy skaniruyushchey kalorimetrii

“…[1]. В связи с этим, широкое распространение получили исследования структуры, состава и свойств асфальтеновых веществ [2], а также их превращений в процессах переработки тяжелых нефтей [3]. Очевидно, что поведение асфальтенов в термических и термокаталитических процессах зависит от их стабильности и реакционной способности, детальное изучение которых представляется актуальной задачей.…”