NIRE Annual Report 1999

NIRE Annual Report

1999

Thermal Cracking Property of Marlim Vacuum Residue

Objectives: Upgrading of heavy oils is generally very difficult because of serious problems such as coke formation and catalyst deactivation. These problems are mainly caused by asphaltene in heavier oil. The purpose of this study is to clarify thermal cracking behavior of Brazilian Marlim vacuum residue. Marlim crude is Brazilian off-shore of large scale reservoir and a typical heavy oil. The vacuum residue in Marlim crude is as many as 30-33% and has high asphaltene contents.

Results: Thermal cracking of MLVR-AS(Asphaltene from Marlim Vacuum Residue) were carried out at the various temperatures. When cracking temperature was 410°C, coke formation was not observed until 30 min of the reaction time and seemed to have an induction period. On the other hand, at higher temperature (430 and 440°C), coke was formed rapidly at high rate without an induction period. Fig. 1 shows the conceptual model structure of original asphaltene and reacted asphaltene at 400, 430 and 440°C of the cracking temperature.; As shown, at low cracking temperature (400°C), asphaltene decomposition occurs through the cleavage of bridge chain which connects the cluster unit structure in asphaltene molecule. At higher temperature, in addition to the cleavage of bridge chain, dealkylation of alkyl substitutes connected to fused ring and dehydrogenation of naphthenic ring are found to be occurred. The reacted asphaltene obtained at 440°C was almost composed of fused aromatic ring.

Fig. 1. Strudtual change of marim asphaltene in thermal cracking

1)	Effect of Solvents and oil soluble catalysts on the coke formation in the cracking of asphaltenes, Proceeding of JECAT' 97, 335(1997).
2)	Thermal Cracking Property of Marlim Vacuum Residue, Preprints of ACS Div. of Fuel Chemistry, 44(1), 182(1999).

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