Hydrodenitrogenation Kinetics of Diesel Oil and Catalyst Stacking Simulation

Abstract

The kinetics of hydrodenitrogenation (HDN) were systematically studied in an isothermally high-throughput reactor over three kinds of catalysts (CoMo, NiMo, and NiMoW) to produce clean diesel meeting the latest national standard of China. The influences of reaction temperature, reaction pressure, volume ratio of H2 to oil, and space time on hydrodenitrogenation were investigated to obtain kinetic parameters. Two kinetic models considering the influence of self-inhibition were proposed for the HDN reaction of diesel oil. The results of both models are satisfactory. Taking the two-lump model as an example, it could well predict the evolution of nitrogen-containing compounds’ concentration along the axial length of the reactor, and the simulation on the HDN activity of various catalyst stacking schemes is close to the experimental data, which proves that the model is applicable for the simulation of a catalyst stacking system. In addition, the concentration of nitrogen-containing compounds was predicted for the catalyst gradation model of different loading sequences.

Kinetic Models of Deep Hydrotreating Reactions to Produce Ultralow Sulfur Diesel

“…The heterocyclic organonitrogen compounds present in hydrocarbon feeds have the highest inhibition effect for the HDS and HDA reactions as well as a strong HDN self-inhibition among all hydrotreating inhibitors, such as polyaromatics, O-containing compounds, H 2 S, and monoaromatics; which can lead to poisoning effect, especially for acid catalysts used in subsequent refining steps. , In addition, N-containing compounds present in fossil fuels can lead to the production of harmful and polluting gases such as nitrogen oxides (NO x ) upon combustion. Organonitrogen compounds in diesel fuel also reduce stability and can cause unwanted color, odor, and gumming. , …”

“…Organonitrogen compounds in diesel fuel also reduce stability and can cause unwanted color, odor, and gumming. 58,59 The concentration of nitrogen-based compounds depends on the source of the feedstock and increases with the boiling temperature of the fraction. However, there is an increasing need to refine alternative feedstocks to produce diesel fuel in addition to conventional crude oil distillates.…”

Catalyst Stacking Technology as a Viable Solution to Ultralow Sulfur Diesel Production

“…Heat exchangers can be implemented in the reactor to control the temperature as well. After exiting the reactor, fluid products are separated (liquid and gas), liquid products are distilled to the desired fuels, and the hydrogen in the gas product is sweetened and recycled. , Catalyst stacking technology can be employed to take advantage of the differences between catalysts to find an optimum system where each catalyst can reach its maximum performance because as the hydrocarbon effluent flows down the reactor, its composition and the local reaction conditions are constantly changing …”

“…These types of compounds are found in the middle distillate fraction and can be classified into two broad categories: basic and nonbasic nitrogen compounds. Both groups affect the TMS catalyst activity, the basic N compounds mainly block the acid sites, and nonbasic N compounds primarily affect the sulfided active phase . Nonheterocyclic nitrogen compounds do not pose a problem in HDS because the removal of their respective N atom occurs rapidly under operating conditions; six-membered nitrides, such as quinoline and acridine fall into the basic category; and five-membered ring nitrides are considered nonbasic, that is, the case for carbazole and indole molecules .…”

“…Jiang et al studied and obtained the HDN kinetics parameters to propose a one-lump and a two-lump kinetic model for the HDN reaction in the production of ULSD . The said kinetic models take into account the self-inhibitions effect of N-containing compounds and can accurately estimate the content of organonitrogen compounds in the feedstock as it flows down through the vertical axis of the fixed-bed reactor.…”