Syed Ahmed Ali

Impact of gasoline and diesel specifications on the refining industry

Future gasoline specifications demand reduction in aromatics, benzene, sulfur, volatility, and boiling point. In response, refiners must modify their processing conditions, catalysts, and mode of operation of catalytic reformers and isomerization units. Diesel fuel is also facing tighter specifications for cetane number, aromatic content, sulfur, and color. To meet these specifications, operational modifications include use of higher activity catalysts, higher hydrotreating seventy, and two-stage processing. This paper reviews fuel legislation adopted recently worldwide, and refining technology solutions practiced and / or planned to meet the new specifications.

Temperature-programmed desorption and reduction of sulfided alumina-pillared montmorillonite

Abstract As a part of our fundamental studies on the acid function of catalysts for hydrocracking, alumina-pillared montmorillonite catalysts were prepared and characterized by means of temperature-programmed desorption with NH 3 from sulfided catalysts (TPD-S) and temperature-programmed reduction of sulfided catalysts (TPR-S). The TPD-S and TPR-S characteristics of catalysts thus obtained have been compared with the activities of cumene cracking in a pulse-type micro reactor. Commercial hydrocracking catalysts were also characterized with similar methods and the performance of cumene cracking was tested. TPD, TPR profiles and cumene cracking activity changed after sulfiding of alumina-pillared montmorillonite. Both the chemical property changes by the heat treatment and the sulfur species adsorbed on the surface allow us to alter its acid property and cumene cracking activity as well.

A novel catalyst for heavy oil hydrocracking

Abstract This paper reports the development of novel hydrocracking catalysts supported on high-surface area saponite clay and pillared with either cobalt or nickel oxide. The catalysts were prepared by aging the Co or Ni nitrate solution, followed by addition of saponite, washing, drying and calcination. The catalysts were evaluated for HDS, HDN and hydrocracking activities in a batch autoclave reactor using vacuum gas oil as feedstock. The results show that the HDS, HDN and cracking activities of the novel catalysts are comparable to that of a conventional NiW/SiO2-Al2O3 catalyst. The Co catalyst gave better HDS activity while the Ni catalyst showed higher HDN and cracking activity. Calcination before metal loading does not seem to effect the overall performance of the Co catalysts. It should be noted these activities are achieved despite the use only one metal as the active ingredient. The results of this study clearly indicate that the saponite clay based catalysts are a potential alternative to the conventional hydrocracking catalysts.

Development of improved catalysts for deep HDS of diesel fuels

Abstract Deep hydrodesulfurization (HDS) of gas oils continues to attract research interest due to environmental-driven regulations which limit its sulfur content to 10–15xa0ppm in several countries. This paper highlights some of the recent studies conducted at King Fahd University of Petroleum and Minerals to develop improved HDS catalysts. The first study was focused on the effect of Co/(Coxa0+xa0Mo) ratio in CoMo/Al2O3 catalysts on HDS pathways of benzothiophene (BT) and dibenzothiophene (DBT). Co/Coxa0+xa0Mo ratio exhibited significant influence on the direct desulfurization (DDS) pathway, but showed no influence on the hydrogenation pathway. A Co/Coxa0+xa0Mo ratio of 0.4 exhibited optimum promotion effect of Co for HDS by DDS route and hence overall HDS. The second study investigated the effect of phosphorus addition on simultaneous HDS reactions and their pathways. The results indicate that phosphorus modification of CoMo/γ-Al2O3 catalysts resulted in enhancement of HDS due to increased dispersion of MoO3 and the maximum enhancement was achieved with 1.0 wtxa0% P2O5. Enhancement of HDS rates was in the following order: 4,6-DMDBT (51xa0%)xa0>xa04-MDBT (38xa0%)xa0>xa0DBT (26xa0%). In the third approach, a series of NiMo catalysts supported on Al2O3-ZrO2 composites containing 0–10 wtxa0% ZrO2 was synthesized, characterized and evaluated for deep desulfurization of gas oil. An increase of 1.3–2.5 times increase in HDS activity at 320–360xa0°C was observed due to reduced interaction between Al2O3 and the active metals. A correlation was found between the enhancement of hydrogenation activity of sulfided catalysts and the reducibility of their oxide precursors.

Simultaneous HDS of DBT and 4,6-DMDBT over single-pot Ti-SBA-15-NiMo catalysts: influence of Si/Ti ratio on the structural properties, dispersion and catalytic activity

A series of Ti-SBA-15-NiMo catalysts with Si/Ti ratios of 1, 2.5, 5, and 10 were prepared by a single-pot method. The dispersion and performance of the catalysts were characterized by N2 adsorption, temperature programmed techniques (NH3-TPD and H2-TPR), X-ray diffraction (XRD), and X-ray fluorescence (XRF) as well as by Raman and Fourier transform infrared (FTIR) spectroscopy. The catalytic activity was determined by simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a batch autoclave reactor. Variations in the Si/Ti ratio resulted in noticeable differences in the characteristics of the catalysts. XRD diffractograms show that Ti is well incorporated into the SBA-15 support at Si/Ti ratios of 10 and 5. However, at Si/Ti ratios below 5, the Ti phases predominate and peaks corresponding to MoO3 phases were not observed. As the Ti incorporation is increased, the moderate surface acidity decreases while the contribution from strong acidity becomes evident. TPR results indicate that a higher amount of Ti increases the metal-support interaction. The HDS rates for DBT and 4,6-DMDBT over a catalyst with an Si/Ti ratio of 10 increased by 33% and 49%, respectively. The enhancement in HDS can be attributed to a lower metal-support interaction. However, a further increase in the Si/Ti ratio removed the enhancement in the HDS rates. A regenerated catalyst with an Si/Ti ratio of 10 exhibited 91% and 86% HDS compared to the fresh catalyst for DBT and DMDBT, respectively. Direct desulfurization was the preferred route for both DBT and 4,6-DMDBT. The HDS rate for DDS is enhanced by the addition of Ti while the HDS rate for the hydrogenation route remains almost constant. The divergent effects on the DDS and HYD pathways indicate that the active sites for hydrogenolysis and hydrogenation are different and are influenced differently by titania addition.