The usage of high metal feedstock for the determination of metal capacity of ARDS catalyst system by accelerated aging tests

For residue hydrotreating catalysts that are deactivated mainly by pore blockage due to deposition of metals, the capacity for accommodation of the deposited metals is an important parameter in determining its stability and life. The primary objective of the present work is to determine the maximum metal capacity of different catalysts that are used in different reactors of atmospheric residue desulfurization (ARDS) units by accelerated aging tests in a short duration. A feedstock with high metals content, namely, Boscan crude, was used for the tests in a multireactor pilot plant to cause complete deactivation of the catalysts by metal accumulation in a shorter period. The influence of operating temperature and LHSV on the rate of catalyst deactivation was also examined for the high metal feed. Catalyst deactivation rate was found to be more than five times faster for the high metal Boscan feed compared to the conventional atmospheric residue from Kuwait export crude. It was possible to determine MMOC of an ARDS catalyst system within 45–50 days by accelerated deactivation test using a high metal feed (e.g., Boscan crude).     

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. The remaining 40% was composed of mercaptanes and alkyl sulfides. In the gas oil boiling range (210-340) two groups of sulfur compounds, namely, alkyl benzothiophenes and alkyl dibenzothiophenes were present. A major portion of the alkyl benzothiophenes was found in the fraction boiling in the narrow range 235-257°C. Among the alkyl dibenzothiophenes, the concentration of C, and C₂ DBTs decreased while that of higher alkyl DBTs (< C₃-DBTs) increased with increasing temperature. The C₁ and C₂ alkyl DBTs were highly concentrated in a fraction boiling between 280-325°C and these sulfur compounds were absent in the fraction boiling above 330°C. The industrial implications of these results are discussed.     

Aromatic Hydrogenation Catalysis: A Review

High aromatic content in diesel fuel has been recognized both to lower the fuel quality and to contribute significantly to the formation of undesired emissions in exhaust gases [1, 2]. Because of the health hazards associated with these emissions, environmental regulations governing the composition of diesel fuels are being tightened in both Europe and the United States, leading to limitations on aromatics [3, 4].     

Preparation of heavy oil hydrotreating catalyst from spent residue hydroprocessing catalysts

In recent years, increasing emphasis has been placed on recycling spent hydroprocessing catalysts due to environmental regulations which list them as hazardous waste materials. In the present work, the recycling of spent residue hydroprocessing catalysts that contained high levels of vanadium was investigated by using them in the preparation of active new hydrotreating catalyst after subjecting them to different treatments such as decoking, acid-leaching and hydrothermal treatment. Catalyst extrudates containing different levels of V, Mo and Ni on Al₂O₃ were prepared by mixing the spent catalyst powder with boehmite in different proportions followed by peptization, kneading and extrusion. The prepared catalyst extrudates were characterized by chemical analysis and surface area and porosity measurements. The HDS and HDM activities of the catalysts were tested using Kuwait atmospheric residue as feed and compared with that of a reference HDM catalyst. Partial leaching of vanadium from the spent catalyst opened up the pores, and the catalyst prepared by mixing the metal-leached spent catalyst (MLSC) with boehmite had higher surface area and pore volume and showed higher hydrotreating activity than that prepared from unleached spent catalyst. Hydrothermal treatment of the spent catalyst increased its porosity and surface area. Catalysts prepared from hydrothermally treated spent catalyst (HTSC) had higher surface area and pore volume and showed higher HDM and HDS activities than that prepared from the spent catalyst without hydrothermal treatment. The catalysts prepared from the treated spent catalysts also exhibited substantially higher HDM and HDS activities than the reference commercial HDM catalyst. The results indicate that spent catalysts containing high levels of vanadium together with Mo and Ni on Al₂O₃ can be used in the preparation of active HDM/HDS catalysts, and thereby, their environmental problem can be reduced.     

Robocasting of alumina hollow filament lattice structures

Robotic controlled deposition (robocasting) of an aqueous colloidal α-Al₂O₃ gel for manufacturing of cellular ceramics with periodical lattice structure was investigated. The colloidal gel was loaded with 50 vol% α-Al₂O₃ and exhibits shear-thinning behavior, a shear modulus of 288 kPa and a yield-stress of ～700 Pa. Tubular filaments of circular and rectangular cross section having an outer diameter of 1.5 mm and a capillary diameter of 0.75 mm were deposited in an oil bath to fabricate lattice truss structures with free spanning filaments. After freeze drying the robocast grids were sintered in air at 1550 °C. X-ray μ-CT revealed continuity of the tubular filaments for long distances (～650 mm). Critical conditions to avoid capillary collapse were discussed by considering bulging stress and pressure distribution within the hollow filament. At short filament length oil infiltration into the capillary driven by capillary suction supports the tubular filament whereas oil flow driven by movement of the tool nozzle causes pressure difference to increase linearly with increasing filament length.