(583co) Investigating Various Catalysts for Slurry Phase Hydrocracking of Iranian Heavy Oil Resid and Its Asphaltenes

Investigating Various Catalysts for Slurry Phase Hydrocracking of Iranian Heavy Oil Resid and Its Asphaltenes 

Mert Haktanir^a*, ^, Kadir Yilmaz^b, Savas Gurdal^b, Solmaz Akmaz^b , Muzaffer  Yasar^b

^aTUPRAS Refineries, Kocaeli, TURKEY

^bDepartment of Chemical Engineering, Istanbul University, Avcilar, 34320, Istanbul, TURKEY

*Corresponding author: mert.haktanir@tupras.com.tr; Tel: +90-262 316 3693

Iranian heavy is a major crude oil blend that finds significant demand in oil refineries around the globe. In a typical refinery setting, crude oil is sent to atmospheric distillation, followed by a vacuum distillation which results in considerable amount of vacuum residue stream, around one fourth of a barrel. This stream consists of non-boiling components which can be sold as either bitumen or fuel oil, both having a diminishing market. Another option is to send this part of petroleum, known as bottom-of-the-barrel, into conversion units that converts heavy petroleum resid into more valuable products such as gas oil, diesel, kerosene, naphtha and LPG. Historically refiners mainly use different coking processes for upgrading vacuum residue; however although coking technology has been improved since the invention of delayed coking, these processes produce significant amount of pet-coke which is less valuable. On the other hand, resid hydrocracking process and reactor designs that use fixed bed catalysts suffer from frequent shut-downs and unreliable operations which decrease their profitability.

Slurry Phase Hydrocracking is a promising technology for minimizing the amount of coke product during resid conversion. Critical point is to find correct type of catalyst that gives high conversion to light products with minimum coke. Catalyst chosen should be relatively cheap and disposable which makes deactivation of catalyst is unimportant. Vacuum residue stream of heavy oils contains a lot of metals and coke precursors. Additional advantage of slurry phase design is that; catalysts act as metal heteroatom removers and coke inhibitors which extend the run length of the unit by minimizing maintenance expenses. Arabian, Venezuelan and Iranian heavy crude oil resids are frequently chosen as design basis of many resid conversion units; Iranian oil has been chosen for this study whose characteristics will be presented.

Our research covers characterization of Iranian oil resid and its asphaltenes part and their slurry phase hydrocracking reactions. Catalysts were chosen in order to maximize toluene-soluble products while minimizing coke produced. The catalyst precursor trial matrix consists of: FeSO4.H2O, the binary mixtures of FeSO4.H2O with metal oxides (Fe2O3, Al2O3, CaO, SiO2) and the mixtures Fe2O3, Al2O3 and SiO2 with elementary sulfur.

Iranian heavy oil resid and its asphaltenes were characterized using elemental analysis, vacuum distillation, SARA separations, gel permeation chromatography (GPC), and nuclear magnetic resonance (1H NMR).

Slurry Phase Hydrocracking experiments were carried out in a 10 ml stainless steel bomb-type reactor with up and down stirrer at 200 rpm. Experiments were conducted at 425 ^oC for 90 minutes with the initial pressure 100 bar H₂ for both resid and asphaltenes.

Heavy oil resid was obtained from vacuum distillation unit of TUPRAS refinery while processing Iranian heavy crude originated atmospheric straight run fuel oil feed. Distillate cut of the unit (ASTM D1160 T95 % cut) was 550 ^oC. Heavy Oil Resid has a specific gravity of 1045.0 Kg/m3 (at 15 °C) which corresponds to 3.9 API (EN-ISO-3675). SARA analysis was performed by dissolving Iranian heavy oil vacuum residue with n-heptane; asphaltene part separated out, and maltenes part was recollected by removing n-heptane from the filtrate. This portion separated into saturates, aromatics, and resins parts according to the SARA protocol. Separation of maltenes was carried out by column chromatography. Average asphaltene content of Iranian heavy oil resid is found to be 13,3 percent.

After performing each reaction for the resid and asphaltene, the reactor was weighed, the gas yield was determined after the high pressure needle valve opened and weighed again. Soxhlet extraction was performed with cellulose cartridges with toluene. Remaining solid part is regarded as coke plus catalyst and weighed. Toluene soluble part is calculated by extracting weight of gas and solid part from initial weight of reactive mixture.

Reactants mass and product percentages stated for both resid and asphaltene reactions. In Table 1 products and reactants of asphaltene reactions were stated.

Table 1:  Products from Iranian Asphaltene Slurry Phase Hydrocracking Reactions

The minimum coke yield for asphaltene was achieved when FeSO₄.H₂O+SiO₂ mixture was used as catalyst precursor with 10 % coke yield. For asphaltene Fe₂O₃+Al₂O₃₊SiO₂+S gave the best results for coke. Toluene soluble fraction was maximized for resid while reacting with Fe₂O₃+Al₂O₃+S; while for asphaltene fraction minimum coke producing Fe₂O₃+Al₂O₃₊SiO₂+S also gave the most toluene soluble fraction.