Effects of In-Process Hydrogenation on Mesophase Development during the Thermal Condensation of Petroleum Aromatic-Rich Fraction

Abstract

In this work, the mesophase pitch was generated from the thermal condensation of the petroleum aromatic-rich fraction. Tetrahydronaphthalene as a hydrogen donor was selected to treat the condensation intermediate using the in-process hydrogenation method. The objective of this work was to investigate the effects of in-process hydrogenation on the formation and development of mesophase structures. Results showed that the intermediate after in-process hydrogenation possessed a more-uniform molecular structure and narrower molecular-weight distribution, compared to the blank intermediate without in-process hydrogenation, which was attributed to the increasing content of naphthenic structures in the intermediate. From the characterization analysis of carbonized products, it can be found that the in-process hydrogenation of the condensation intermediate was conducive to the generation of mesophase pitch with a large domain structure, narrow molecular-weight distribution, low softening point, and carbon residue.

Hydrogen Transfer in Asphaltenes and Bitumen at 250 °C

“…Hydrogen transfer reactions are very important during thermal conversion of heavy oils, bitumen, and coals. In the literature, much emphasis was placed on hydrogen donors and hydrogen donor solvents. − The use of hydrogen donor solvents gave rise to the development of aptly named processes such as the Donor Refined Bitumen process, and the Exxon Donor Solvent process . A common feature of these liquefaction-type processes was the use of hydrogen donor solvents, which could be regenerated in situ or ex situ by hydrogenation.…”

Preparation and characterization of petroleum-based mesophase pitch by thermal condensation with in-process hydrogenation

“…This indicated that the contents of alkyl chains and methylene bridges in the three intermediates were similar, but the contents of naphthenic structures increased signicantly with the rising degree of the in-process hydrogenation. 30,35 To sum up, the in-process hydrogenation was conductive to the decrease of intermediates' condensation degrees and the increase of intermediates' naphthenic structures. Given the solubility and hydrogen distribution analyses of intermediates, the increase of the naphthenic structures in intermediate was the reason for the change of the intermediates' molecular structures and extracted component distributions.…”

“…It implied that the molecules of the intermediates were increasingly concentrated in the two middle components with rising degree of the in-process hydrogenation. Furthermore, according to similarity-intermiscibility theory, 30,34 the molecules which were concentrated in components HI-TS or TI-QS possessed similar molecular structures. Therefore, the molecular structure of hydrogenated intermediate was more uniform, and the uniform degree of molecular structure increased with rising degree of the in-process hydrogenation.…”

“…This could prevent the excessive reaction and prolong the coking-induction period. 26,30 So the soening points of N 2 -MP and N 3 -MP were lower than that of N 1 -MP. The above demonstrated that in-process hydrogenation method contributed to the preparation of mesophase product with concentrated extracted component distribution and low soening point.…”

“…As reported in our previous work, 30 the in-process hydrogenation was first used in the preparation of mesophase pitch. Tetrahydronaphthalene was selected as hydrogen donor to treat the intermediates generated during the thermal reaction.…”