Abstract
Fixed bed tubular plug flow reactor is used to investigate model catalysts performance during the hydrodesulphurization of Heavy Arabian Oil atmospheric residuum. The effects of temperature (300-380℃), pressure (30-80 atm) and particle size with characteristic lengths (Lpo = 0.0059cm), Lp1 = 0.0327cm) on the rate of the Hydrodesulphurization reaction are investigated. Supported Co-Mo/ γ-AL2O3 catalysts, CAT-1 with Co= 3wt.% and Mo= 10.6wt.% and 0.5wt.% MS 13X and CAT-2 with the same composition but without the addition of MS 13X loadings were prepared using the double impregnation method. All prepared catalysts were characterized for their porous structure and composition. A Kinetic equation was developed for pulverized CAT-1 particles, RHDS= 9.9696*1010 exp (-17058/T) * PH2 *CS2.2 / (1+0.00802 * PH2). Effectiveness factors and effective diffusivity coefficients were estimated for both catalyst particle sizes. CAT-1 catalyst sample showing slightly higher activity lost approximately 20% of its initial activity after 450 hours of operation compared to 11% lost for CAT-2 sample. The presence of MS 13X in CAT-1 is accompanied with lighter HC products (C1-C4 up to 210℃) giving rise to more hydrocracking orientations especially at high temperatures with higher API degrees of the treated products.
Highlights
The last century had been marked by major developments in deep understanding of catalyzed reactions theory and catalyst performance
The analysis is based on the performance equation of the plug flow reactor with large recycle ratio R (100% back mixing), τ= VR/υt0 = CS0*Xf/ RHDS, where τ is the space time min, VR is the catalyst bed volume cm3, υt0 is the volumetric flow rate of the feed plus Hydrogen entering the reactor cm3mix./h, [at reactor operating conditions], CS0 is the initial concentration of sulfur in the feed stocks g-mole S/cm3oil, Xf is the final chemical conversion of sulfur attained at steady state conditions and RHDS is the reaction rate of sulfur removal g-mol S/cm3cat.s
The prepared catalyst showed some comparable performance with some other industrial catalysts used for hydro-treating heavy oil residuum
Summary
The last century had been marked by major developments in deep understanding of catalyzed reactions theory and catalyst performance. Various possibilities of reaction paths for HDS of model sulfur compounds have been proposed by Lipsch and Schuit [10], who investigated the kinetics of Thiophene HDS and reported that the thiophene HDS occurs via direct C-S bond cleavage to form Butadiene intermediate, tetrahydro-thiophene (THT) or dihydro-thiophene(DHT) These intermediates are very difficult to observe under standard reaction conditions [11]. Van Parijs and Froment [13] reported the existence of two types of active sites on HDS catalysts, i.e. one for Hydrogenolysis and one for hydrogenation This is in agreement with the Rim Edge model of Daage and Chianelli [14]. Another debate concerns the adsorption mode of hydrogen being either molecularly or dissociative adsorbed
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