Abstract
Heavy oil and bitumen resources will need to be exploited to supplement depleting conventional oils worldwide as they gradually approach their peak production in the forthcoming decades. However, the physico-chemical characteristics of heavy oil and bitumen include high density, low distillates fraction, high viscosity, and high hetero-atom content which make extraction difficult and relatively expensive. The Toe-to-Heel Air Injection (THAI) and ‘add-on’ Catalytic upgrading process in situ (CAPRI) were specifically developed for the recovery and upgrading of heavy oil and bitumen. In this study, the effects of reaction gas media used in THAI–CAPRI were investigated, in particular the effects of using hydrogen, methane, nitrogen, and a blended gas mixture to simulate THAI combustion gases with Co–Mo/γ-Al2O3 catalyst at a reaction temperature of 425°C, pressure 10bar, and gas-to-oil ratio 50mLmL−1. Ex situ regeneration of the spent catalyst by thermal oxidation of the asphaltenes and coke deposits was also investigated. It was found that the average changes in API gravity of the produced oil were 4° using hydrogen, 3° with methane, 2.9° with THAI gas, and 2.7° with nitrogen above the value of 14° API gravity for the feed oil. The viscosity reduction and conversion of hydrocarbons with boiling point 343°C+ into lower boiling distillable fractions followed the same trend as the API gravity. The percentage loss in specific surface areas as a result of coke deposition in the different reaction gases were as follows: 57.2% for hydrogen, 68% for methane, and 96% for nitrogen relative to the surface area of the fresh catalyst of 214.4m2g−1. It was found that the spent catalyst contained 6 and 3wt.% less coke after six hours operation when using hydrogen and methane reaction gases respectively compared to 23.5wt.% coke content in a nitrogen atmosphere. Also, 48.5% of the catalyst specific surface area was recovered after oxidative regeneration.
Highlights
The International Energy Agency (IEA) [1] has forecast 40% growth in worldwide primary energy resources demand by 2035
The spent catalyst from upgrading reaction with nitrogen atmosphere was regenerated at high temperature using 14.4 g of the spent catalyst in a CarboliteÒ furnace (Keison Products, UK) under air atmosphere, thereafter reduction was performed in the Catalytic upgrading process in situ (CAPRI) reactor using hydrogen gas at a flow rate of 50 mL minÀ1 for 45 min, before been retested for catalytic activity
The change in API gravity of the produced upgraded oils as a function of time-on-stream are respectively shown in Fig. 1 for hydrogen, methane, to-Heel Air Injection (THAI) gas, and nitrogen reaction gas
Summary
The International Energy Agency (IEA) [1] has forecast 40% growth in worldwide primary energy resources demand by 2035. The CAPRI process has been previously investigated by the authors using a set of micro-reactors to replicate underground upgrading conditions and to optimise the selection of catalyst type, oil and gas flowrate, reaction temperature and pressure [17]. They concluded that the potential of the technology can be limited by the deposition of asphaltenes, coke and metal, which drastically deactivates the catalyst. THAI gas mixture were studied over a Co–Mo/c-Al2O3 catalyst at a previously determined optimum process reaction temperature of 425 °C, pressure 20 bar, oil flow 1 mL minÀ1, and gas-to-oil ratio 500 mL mLÀ1
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