Experimental study on catalytic hydroprocessing of oxi-solubilized asphaltenes in water

Parsa Haghighat and Pedro Pereira-Almao

Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada

Abstract

Heavy oils are more and more produced due to declination of conventional oil resources. Asphaltenes are the heaviest portion of heavy oil, causing dramatic deficiencies during transportations and reactions. Current commercial processes of asphaltenes such as Delayed Coking are not efficient in terms of distillate products and create major environmental issues. Finding the new pathways for processing asphaltenes is crucially demanding for future. This research group in search of alternative pathways for asphalthenes processing has pioneered the solubilisation of asphalthenes in water via wet air oxidation. This path could facilitate the solution of crucial problems created by Asphaltenes. The main objective of current research is focused on converting solubilized asphaltenes to more valuable products.
For this purpose, catalytic hydroprocessing of oxi-solubilized asphaltenes in water was investigated. It was intended to optimize the catalysts amount and operation parameters and develop the kinetic model for hydroprocessing reaction. Experiments were conducted in 100 ml Parr batch reactor below the critical condition of water. Several deoxygenation reactions such as hydrodeoxygenation and decarboxylation occur during this reaction. Hydroprocessing of asphaltenes in aqueous phase improves mass transfer limitation and diminishes coke formation compared to pure asphaltenes hydroprocessing. Analysis of gas phase revealed the CO2 is the major product while low amount of CO, methane and other refinery gases are also formed which could be result of decarboxylation, aqueous phase reforming and water-gas shift reactions.
The comparison of thermal and catalytic hydroprocessing shows the conversion to liquid products increases significantly from 10% to around 20% by using the proper catalyst. Among the tested catalysts, sulfide form of NiMo/É£ -Alumina presents the best activity. The effect of reaction temperature was investigated for the range of 280â?¦C to 320â?¦C. Increasing the temperature increases conversion of solubilized asphaltenes. At more severe temperatures, the quality of liquid distillates improves and the boiling point distribution of liquid products shifts to lighter materials. To establish the kinetic model, the residence time of reaction was varied from 1
h to 6 h and effect of initial concentration of solubilized asphaltene in water was evaluated. Experimental results indicate that first order reaction could be applied to hydroprocessing reaction of solubilized asphaltene in water.