S.K. Maity

Alumina-silica binary mixed oxide used as support of catalysts for hydrotreating of Maya heavy crude

Abstract Three different methods are applied to prepare alumina–titania binary mixed oxide supports. These supports are used to prepare catalysts for hydrotreating of Maya heavy crude. Sequential incipient wetness and co-impregnation techniques were employed for preparation of catalysts. Ammonium heptamolybdenum was used as precursor for MoO 3 . Catalysts are characterized by XRD, TPR and pore size distribution. Hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp) reactions are studied on these catalysts. One reference catalyst is also taken for comparison. Coke and metals depositions on spent catalysts are measured. Catalyst deactivation rate is also studied. A combined method of urea hydrolysis and pH variation is suitable to prepare bigger size of pore diameter and more pore volume support. XRD results indicate that prepared alumina–titania oxides are amorphous or very poor crystalline in nature. Very complex nature of TPR profiles is observed. Two catalysts (C and D) show very high activities and also give very good stability compared to reference catalyst. We observe an average correlation between pore diameter of catalyst with HDM and HDAsp conversions. It indicates that bigger pore diameter catalyst is suitable for removal of metals and asphaltenes, but bigger pore size is not only criterion to show good HDM activity. Total pore volume is also an important parameter in this regard. Enhancement of activities is observed on P containing catalyst. Coke is deposited on the catalyst pore mouth and it caused a drastic reduction of specific surface area of spent catalyst. Coke deposition is more on the catalyst having bigger pore diameter. We also observe that rate of V removal is higher than rate of Ni removal.

Catalysts for hydroprocessing of Maya heavy crude

In this work the effect of active metals, promoters, phosphorous and lithium on hydroprocessing reactions of Maya heavy crude was studied. Four reactions (hydrodemetallization (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp)) were carried out on seven different catalysts. The support of these catalysts was prepared by urea hydrolysis method. Temperature programmed reduction (TPR) results showed that more reducible species were present on cobalt promoted catalyst compared with unpromoted one. We observed that active metal was more dispersed on P containing catalyst. The conversions, determined as Time Weighted Mean Conversion (TWMC), were very high for a PCoMo catalyst, however, it exhibited a rapid fall of activation. A linear correlation was found between the loss of specific surface area (SSA) and coke formation. The catalysts deactivation was mainly due to coke formation over catalyst surface. Cobalt promoted catalysts showed higher initial HDM conversion compared with Ni one. Mo active metal was better for HDM reaction. Even though lithium-doped catalyst showed slightly higher activities it had no effect on catalyst life.

Effect of Asphaltene Contained in Feed on Deactivation of Maya Crude Hydrotreating Catalyst

Abstract The effect of asphaltene contained in Maya heavy crude on the deactivation is studied. Different heavy feeds are prepared by the mixing of Maya with desulfurized diesel. A standard NiMo catalyst is used in a batch reactor to evaluate hydrodemetallation (HDM), hydrodesulphurization (HDS), and asphaltene (HDAsp) conversion. Textural properties of the spent catalysts are studied by pore size distribution and x-ray diffraction (XRD). Metals and coke deposition on the deactivated catalysts are also measured. It is found that HDM and HDAsp activities decrease with increasing concentration of asphaltene in feed, whereas the opposite trend is observed in the case of HDS. Both deposits of coke and vanadium on the catalysts surface increase with the concentration of asphaltene in feed. The presence of asphaltene is the main reason to decrease surface area and total pore volume and hence it causes deactivation.

Hydrotreating of Maya Crude Oil: I. Effect of Support Composition and Its Pore-diameter on Asphaltene Conversion

Abstract A systematic study for a concept governing support effect in heavy oil hydrotreating (HDT) catalysts is performed. Different Al2O3 and its mixed oxides supports were prepared and CoMo supported catalysts were tested for Maya heavy crude oil hydrotreating. Fresh and spent catalysts are characterized with N2 adsorption-desorption, element analysis, and scanning electron microscopy-energy dispersion analysis by x-ray (SEM-EDAX), which confirms that coke and metals deposition on the surface of catalyst is most probably near the pore mouth. It is also demonstrated from these results that asphaltene conversion depends on the pore diameter of the catalyst, while other hydrotreating conversions (hydrodesulfurization (HDS), hydrodenitogenation (HDN), and in some extent hydrodemetallization (HDM)) are more likely affected by the nature of active metal distribution. The evaluation of alumina mixed oxide (TiO2, ZrO2, B2O3, and MgO) supported catalysts indicates that supports with basic nature have better stability than the acid ones.

Hydrotreating of maya crude oil: II. Generalized relationship between hydrogenolysis and HDAs

Abstract Studies of hydrodeasphaltenization (HDAs) and hydrodemetallization (HDM) of Maya heavy crude oil at temperature of 380°C and pressure of 5.4 MPa have been carried out in a high pressure microreactor. Different pore diameter alumina CoMo-supported catalysts were prepared and their catalytic effect is estimated. The fresh and spent catalysts were characterized by textural properties; and the average pore diameter of a fresh catalyst was found to be proportional to the HDM and HDA conversions. The hydrogen elemental analysis of reactant and products indicated that asphaltene conversion is a combination of cracking and hydrogenation (HYD), since HDM correlated well with HDAs, which is due to the complex nature of both molecules (asphaltene and metals).

Comparison between refinery processes for heavy oil upgrading: a future fuel demand

Petroleum refining industry is entering into the significant era of reformation due to the depletion of light petroleum and an increase in heavy or extra heavy crude oil production. There is a strong need to revise the processes that are commercially available for heavy crude oil refining. Upgrading of heavy and extra heavy oil by means of catalytic processes requires new generation catalyst along with several modifications of process conditions. This review focuses on the description of different ways to convert heavy crude oils into synthetic crude oil. Specific illustrative examples of hydroprocessing indicated how such studies may open up new routes in the search of suitable catalyst and process for upgrading heavy petroleum. [Received: October 10, 2007; Accepted: January 12, 2008]