Anthony Stanislaus

Hydroprocessing of vacuum residues: relation between catalyst activity, deactivation and pore size distribution

Abstract Four catalysts with different unimodal and bimodal pore size distributions having different proportions of meso- and macropores were studied. The performance of the catalysts in terms of activity and selectivity as well as deactivation in selected hydrotreating reactions was examined using Kuwait vacuum residue as feedstock. The effect of catalyst pore size was significantly different for different reactions. For sulfur removal (HDS), a unimodal pore catalyst with maximum pore volume in the medium mesopore range (10–25 nm diameter) showed the highest activity. For hydrodemetallation (HDM) and hydrodenitrogenation (HDN) reactions, large-pore catalysts, having a major proportion of their pore volume in 100–300 nm diameter pores, were more effective. Bimodal pore catalysts having large amounts of narrow pores showed a higher rate of deactivation than unimodal pore catalysts with a maximum amount of medium mesopores.

Kinetics of individual sulfur compounds in deep hydrodesulfurization of Kuwait diesel oil

This paper deals with the factors influencing deep desulfurization of Kuwait diesel oil. Systematic experiments were conducted to optimize the process conditions for deep desulfurization of gas oil to low-sulfur (500 ppmw max.) diesel fuel. Particular attention was paid to the effect of operating conditions on the conversion of various types of individual sulfur compounds present in the gas oil feed. Overall kinetics of gas oil desulfurization and the HDS kinetics of some important individual sulfur compounds present in the gas oil, such as dibenzothiophene and its alkyl derivatives, were also determined.

INFLUENCE OF CATALYST ACIDITY AND FEEDSTOCK QUALITY ON HYDROTREATING CATALYST DEACTIVATION BY COKE DEPOSITION

Influence of catalyst acidity and feedstock quality on the extent of initial coke formation and its role in hydrotreating catalyst deactivation were investigated. A series of Ni–Mo/Al2O3 catalysts with varying acidities were prepared by using sodium and fluoride ions as acidity modifying additives. Acidities of the catalysts decreased in the sequence: Ni-Mo-F(5%) > Ni-Mo-F(2%) > Ni-Mo > Ni-Mo-Na(1%) > Ni-Mo-Na (5%). The amount of coke formed on the catalyst did not show any direct relation to catalysts acidity but was found to depend strongly on the type of additive used for modifying acidity. In the case of sodium addition, although, the catalysts strong acidity decreased, coke deposition increased probably due to the suppression of catalysts hydrogenation function by interaction between sodium and molybdenum. Fluoride addition at low concentration levels (e.g. 2wt%) increased both HDS and HDN activities of the catalyst, but at high concentration levels of fluoride (e.g. 5 wt%), the catalyst showed a sharp decrease in HDS and HDN activity. Sodium addition at all levels decreased catalysts activity for both HDS and HDN. In the feed quality effect studies, a feedstock with a higher concentration of nitrogen and asphaltenes led to rapid coke build up during the initial period. Solid state carbon-13 NMR analysis of the coke on various spent catalyst samples showed that the coke formed from residual oil feed was more aromatic in character than that from VGO, and the initial coke changed its aromatic character with processing time.

Sulfur compound type distribution in naphtha and gas oil fractions of Kuwaiti crude

ABSTRACT The need for detailed information on the types of sulfur compounds present in various petroleum cuts has been well recognized by refiners and environmentalists worldwide. This need is growing in recent years in view of the current environmental regulations that limit the sulfur content of transportation fuels to very low levels. In the present work we have studied the distribution of different kinds of sulfur compounds present in light and middle distillates of Kuwait crude oil. A representative sample of Kuwait crude oil was fractionated into naphtha (15-160°C) and 10-15°C cuts in the gas oil boiling range (210-340°C) using an 80L capacity autodistillation unit “AUTODEST-800” according to ASTM 2892. The distribution of various types of sulfur compounds in each of these cuts was quantitatively estimated by capillary gas chromatography equipped with a sulfur chemiluminescence detector. Thiophene and its alkyl derivatives constituted about 60% of the total sulfur compounds in the naphtha fraction. ...

COMPARISON BETWEEN THE PERFORMANCE OF CONVENTIONAL AND HIGH-METAL Co-Mo AND Ni-Mo CATALYSTS IN DEEP DESULFURIZATION OF KUWAIT ATMOSPHERIC GAS OIL

ABSTRACT Due to environmental constraints, sulfur content of diesel fuel has been restricted to very low levels (500 ppm maximum) in many countries. As a result, a greater emphasis has been placed in recent years on the development of catalysts and processes for deep desulfurization of diesel blending streams to produce low sulfur diesel fuel. In the present work we have compared the performance of a conventional Co-Mo catalyst with that of high metal loading Co-Mo and Ni-Mo catalysts in deep desulfurization of Kuwait atmospheric gas oil. The tests were carried out in a fixed bed reactor unit using 75 ml of catalyst under the conditions: P=32 bar; LHSV = 4h−1; H2/oil ratio = 100 ml/ml; temperature range = 330 − 390°C. HDS activity of the high molybdenum Co-Mo catalyst was superior to that of the conventional Co-Mo hydrotreating catalyst. High metal loading Co-Mo/Al2O3 catalyst also showed a substantially higher HDS activity than the Ni-Mo/Al2O3 catalyst containing a similar high metal loading. The unreact...