Article pubs.acs.org/EF
Experimental Study on Co-hydroprocessing Canola Oil and Heavy Vacuum Gas Oil Blends Jinwen Chen,* Hena Farooqi, and Craig Fairbridge CanmetENERGY, Natural Resources Canada, One Oil Patch Drive, Devon, AB T9G 1A8, Canada ABSTRACT: Experimental studies have been conducted on the co-hydroprocessing of canola oil−heavy vacuum gas oil (HVGO) blends with different blending ratios under typical hydroprocessing conditions. It was found that the HVGO−canola oil blend feeds had higher conversion to light product than the pure HVGO feed at similar operating conditions. However, the hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) were not affected by the addition of canola oil into the HVGO. Under similar conversion or light product yield, coprocessing HVGO−canola oil blends required lower temperature and/or pressure than hydroprocessing the pure HVGO, an implication of potential energy saving. It was also found that at the same conversion, the HVGO−canola oil blends generated more diesel but less gasoline than pure HVGO, an effective way to meet the fast increasing diesel demand.
1. INTRODUCTION The worldwide increasing energy demand, especially from those emerging countries such as China, India, Brazil, and the decline in light/medium crude oils have sparked the fast development and exploitation of heavy and extra heavy oil reserves, such as those in Mexico, Venezuela, and Canada. For example, the production of Canadian bitumen is expected to increase significantly in the near future, from the current 1.6 million barrels per day (MBPD) to 3.2 MBPD by 2020 and 4.2 MBPD by 2025.1 It is known that the carbon footprint, or greenhouse gas (GHG) emission, related to heavy oil and bitumen production, upgrading, and refining to produce clean transportation fuels are higher than those related to light/ medium crudes.2−4 Meanwhile, biomass derived fuels from renewable sources are considered sustainable and have the potential to help reducing GHG emission and other environmental impacts,3−5 provided that they are produced in a sustainable way (based on their life cycle assessment). Many developed countries require a certain percentage of biofuels or renewable fuels in the total fuel product, which is mainly derived from petroleum. For example, currently, renewable biofuel makes up about 8% of total fuels consumed in the U.S.6 In European Union (EU) countries, the requirement for renewable fuels in the total transportation fuel is 5.75% in 2010 and will be raised to 10% by 2020 according to the “Directive on the Promotion of the Use of Biofuels and Other Renewable Fuels for Transport”.7 Coprocessing petroleum with biomass derived feedstocks, while meeting government regulations and engine fuel standards, is one of the most attractive and practical options for petroleum refiners, and heavy oil and bitumen upgraders.8 It has a great potential to reduce the carbon footprint, or GHG emission, in the whole processing chain of producing clean transportation fuels from light/medium and heavy/extra-heavy petroleum resources. Processing blends of petroleum and biomass derived feedstocks, or coprocessing, with existing refining configuration, catalysts, processes, and technologies offers a wide range of advantages from both technological and economical points of © 2013 American Chemical Society
view. By using the existing refining infrastructure and major process units, little or no extra capital investment is required. In addition, the technologies and catalysts need not change either. Another advantage with coprocessing is the potential synergy between aromatic petroleum feedstocks (especially Canadian oil sands derived crudes) and paraffinic biomass feedstocks and improved fuel quality (octane and cetane numbers). Biomass feedstocks have their unique characteristics (high contents of oxygen, difficulty in analysis and characterization) and potentially create additional operational problems, such as compatibility with petroleum and water separation. Therefore, great technical challenges are expected and need to be addressed in actual implementation and operation of coprocessing in order to improve or even maintain process efficiency and product quality. Optimizing the blending amount of biomass derived feedstocks, while retaining catalyst activity and stability, and avoiding potential reactor plugging are also essential. There are two major refining processes that are considered to be suitable for coprocessing: hydroprocessing (hydrotreating and hydrocracking) and fluid catalytic cracking. The focus of this study is on co-hydroprocessing of oil sand crude oils and modern-day biomass derived feedstocks. There have been a number of studies published on coprocessing petroleum and biomass feedstocks through hydroprocessing with commercial catalysts and under typical industrial operating conditions. A detailed review of these studies has been conducted by Al-Sabawi and Chen.9 In the majority of these studies, two different types of biomass feedstocks have been used: pyrolysis oils and vegetable oils. Mercader et al.10 examined co-hydroprocessing a petroleum gasoil with a hydrodeoxygenated pyrolysis oil derived from wood residue using a commercial Co−Mo/Al2O3 catalysts. They observed inhibition effects on hydrodesulfurization (HDS) by hydrodeoxygenation (HDO) reactions of the Received: April 2, 2013 Revised: May 28, 2013 Published: May 29, 2013 3306
dx.doi.org/10.1021/ef4005835 | Energy Fuels 2013, 27, 3306−3315
Energy & Fuels
Article
Figure 1. Reactor unit schematic diagram.
Tóth et al.20 and Bezergianni et al.21 performed mild hydrocracking studies using blends of sunflower oil (SFO) and vacuum gas oil and concluded that higher content of SFO in the blends increased hydrocracking conversion. They also observed inhibition effect during HDS and hydrodenitrogenation (HDN) by HDO of SFO. However, Lappas et al.22 had an opposite observation that SFO inhibited vacuum gas oil (VGO) hydrocracking but had no impact on HDN. However, they found that the presence of sulfur in the VGO inhibited HDO of SFO. Huber et al.23 did not observe inhibition effect during HDS of heavy vacuum oil (HVO) by HDO of SFO on Ni− Mo/Al2O3 catalysts. In a recent study, Templis et al.8 investigated the effect of palm oil on hydrotreating of gasoil over a commercial Co−Mo/ Al2O3 catalyst. They observed a decrease in HDS rate with the increase in palm oil content from 0 to 5 wt % in the feed blend. Further increase in palm oil content did not further affect HDS rate. Watkins et al.16 also studied hydrotreating blends of palm oil and soybean oil (SBO) with straight-run diesel. They concluded that palm oil and SBO did not affect HDS at ultra low sulfur level (
