Stability-related tests on visbreaking residues obtained at increasing severity

• Published in: Fuel (Guildford) 1993-08, Vol.72 (8), p.1109-1114
• Main Authors: Zerlia, Tiziana, Pinelli, Giacomo
• Format: Article
• Language: English
• Subjects: Applied sciences; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fuels; specific gravity; Storage of liquid petroleum products and other liquids. Tanks. Metering. Underground storage. Problems of losses in storage; visbreaking; viscosity
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(93)90317-U

Xylene-equivalent (XE) and sediment by hot filtration (‘Sediment’) are often used to characterize instability of petroleum thermal residues. Nine visbreaking (VB) residues obtained at increasing severity from the same feedstock were studied to explain the significance of these characteristics in the light of the chemical changes induced by the VB process. The results indicate two different severity-related relations between XE (and Sediment) and chemical composition, at low and high severity: under mild process conditions the instability (XE) increases as the asphaltene content decreases, whereas the opposite trend is found at high severity. These opposing trends can be explained in the light of the VB chemistry and shed light on the different mechanisms governing the peptization state of asphaltenes under mild and severe process conditions. Sediment, constant at low severity, starts to increase only when condensation reactions involving asphaltenes occur. Thus Sediment, which unlike XE cannot be adjusted with a suitable diluent fuel, plays a key role in evaluation of the stability of thermal residues: high Sediment, in the absence of inorganic or coke-like material, would be concomitant with storage problems, whatever the XE level.