Comparison of the Performance of Upflow and Downflow Small-Reactors in Hydrodesulfurization Reactions

Abstract

An experimental study for comparing the behavior of a small-reactor in the hydrodesulfurization of straight-run gas oil with two modes of operation, upflow and downflow, is presented. The reactor has 525 mm length and 14.3 mm internal diameter. Experiments were conducted at commercial HDS operating conditions (5.3 MPa total pressure, 356.2 mL/mL hydrogen-to-oil ratio, reaction temperature of 613−653 K, and LHSV of 1.0−2.5 h-1). All tests were carried out over a commercial NiMo/γ-Al2O3 catalyst. The effect of different catalyst-to-diluent ratios on the sulfur removal was also studied. The results of SRGO hydrodesulfurization showed that upflow with a 50/50 vol % catalyst-to-diluent ratio is the best system to avoid external gradients and other effects such as poor wetting of catalyst, axial dispersion, wall effects, and flow maldistribution. Apparent activation energies were determined for upflow and downflow modes of operation with and without diluent.

A batch reactor study to determine effectiveness factors of commercial HDS catalyst

“…S0 1=ð1ÀnÞ (2) In this equation k ap represents the ''apparent'' kinetic constant, which may be influenced by intraparticle gradients depending on the catalyst particle size.…”

“…[2]. The selection of the experimental setup is related to the reacting system more than the type of industrial reactor, even when this latter is already defined.…”

CoMo/Al2O3 catalysts prepared on the basis of Co2Mo10-heteropolyacid and cobalt citrate: Effect of Co/Mo ratio

“…The tests were performed under the following conditions: temperatures of 330-355°C; pressure of 4.0 MPa; liquid hourly space velocity (LHSV) of 2.0 h À1 ; hydrogen: feedstock ratio of 600 NL/L. 10 cm 3 of catalyst sample (pellet size of 0.25-0.55 mm) was diluted with low surface area carborundum (0.04-0.06 mm) in a 1:1 ratio (catalyst:SiC) for minimizing heat and mass transfer limitations [32,33]. Before the testing, the catalysts were activated by sulfidation with a mixture of 15% H 2 S in H 2 (50 ml/min) at 400°C and 1 MPa for 2 h. A series of preliminary experiments, consisting in varying parameters such as the size of the sieved fractions and both the catalyst mass and the feedstock flow rate at constant space velocity, ruled out the existence of diffusional limitations under the used experimental conditions.…”

Recent Trends in the Cleaning of Diesel Fuels via Desulfurization Processes

“…Industrial reactor configuration for deep HDS of gas oils in terms of reaction order and effect of H 2 S has been discussed (78,(81)(82)(83)(84)(85)(86)(87) . The reactor design and configuration involve one-stage and two-stage desulfurization as shown in Fig.…”