Over the last decades a depletion of the conventional crudes combined with an increase in oil prices has resulted in an increase in the processing of heavier crudes. These heavier crudes are characterized by a high carbon/hydrogen (C/H) ratio, a high viscosity, large amounts of asphaltenes, and a high amount of heteroatoms (sulfur, nitrogen, oxygen, vanadium, nickel, arsenic, iron and others).
One of the main purposes of hydroprocessing of heavy crudes is to remove these heteroatoms, since sulfur and nitrogen constitute an environmental hazard. The metals present in the feed will deactivate the hydrotreating catalyst, and it is therefore crucial initially to remove these to obtain a product of as high a quality as possible.
The goal of this project was to develop an understanding of the hydrodemetallization reaction (HDM) in vacuum gas oils (VGO) in order to reduce the deactivation and thus achieve more valuable products.
The metal components and the HDM reactions are well documented for heavier oil fractions (resid) but are less understood for VGO as the concentration of metals is significantly lower in this type of feed.
The theory used for this project was mainly based on resid fractions and then applied to VGO. To develop a kinetic expression for the HDM mechanism, an experiment was conducted at Topsoe at several different conditions. The kinetic expression arrived at was then used in the interpretation of the results obtained from testing of different experimental catalysts. By use of computer programming, a simple model for the deposition of metals was also developed.
Julie Jannerup, DTU, Department of Chemical Engineering
Master thesis in the R&D Division, Refinery Process
Currently working as Technical Service Engineer in the Catalyst Division