76 Int. J. Oil, Gas and Coal Technology, Vol. 21, No. 1, 2019 Copyright © 2019 Inderscience Enterprises Ltd. Colloidal stability tests on vacuum residue hydrocracked products obtained at increasing severity Kirtika Kohli, Ravindra Prajapati, Nivedita Singh and Samir K. Maity* Residue Conversion Area, CSIR-Indian Institute of Petroleum, Dehradun-248005, India Email: kkohli@iip.res.in Email: ravindrap@iip.res.in Email: niveditasingh0504@gmail.com Email: skmaity@iip.res.in *Corresponding author Abstract: Stability of the thermally hydrocracked products has been investigated by measuring different parameters such as colloidal instability index (CII), Stankiewicz plot (SP), qualitative-quantitative analysis (QQA), stability cross plots (SCP), spot tests, merit number and separability number (SN). Each parameter is measured in the products obtained from two vacuum residues having different asphaltene content. The stability of the hydrocracked product is different for the different parameters. But in general, the products obtained at lower and higher temperature are stable by most of the parameters. Spot test and separability number gives the similar results. Interestingly, it is found that the product obtained at 420°C from low asphaltene content feed is unstable by all above said stability parameters whereas the product (at 420°C) from high asphaltene content feed is stable, indicating that the stability of a hydrocracked product depends not only on the asphaltene content of a feed but also the nature of other components such as aromatic and resin. It is also observed that CII and SP parameters which are calculated from SARA fractions also predict colloidal stability with good agreement. [Received: November 24, 2016; Accepted: April 2, 2017] Keywords: colloidal instability index; stability cross plot; separability number; asphaltene. Reference to this paper should be made as follows: Kohli, K., Prajapati, R., Singh, N. and Maity, S.K. (2019) ‘Colloidal stability tests on vacuum residue hydrocracked products obtained at increasing severity’, Int. J. Oil, Gas and Coal Technology, Vol. 21, No. 1, pp.76–90. Biographical notes: Kirtika Kohli is a Research Scholar working in the Residue Conversion Area, CSIR-IIP. She is doing her PhD research on the deactivation study of residue hydrotreating catalysts. Ravindra Prajapati is a Research Scholar working in the Residue Conversion Area, CSIR-IIP. He is doing his PhD research on the development of slurry phase catalysts for residue upgradation.