Elimination of Coke in an Aged Hydrotreating Catalyst via a Non-Thermal Plasma Process: Comparison with a Coked Zeolite

Srour Srour,Pinard Pinard,Batiot-Dupeyrat Batiot-Dupeyrat,Alnaboulsi Alnaboulsi,Hamieh Hamieh,Astafan Astafan,Devers Devers,Toufaily Toufaily

doi:10.3390/catal9090783

Abstract

The removal of coke from an aged industrial hydrodesulfurization catalyst, using dielectric barrier discharge (DBD) non-thermal plasma with a pin to plate geometry, was investigated. The aged catalyst was introduced into the plasma reactor as a thin wafer. After 130 minutes of plasma treatment, with P = 30 W, 70% of the coke was removed while more than 40% of the sulfur was still present. Characterization of catalyst at different locations of the wafer showed that the coke was more easily removed at the center, close to the pin electrode where the electric field was more intense. The formation of an unexpected phase, under the plasma discharge, was highlighted, it corresponded to the family of Keggin HPA PMo12O40 3−, which could be an interesting precursor of catalyst for the hydrodesulfurization (HDS) process. Compared with a coked zeolite, the rate of regeneration is lower for the HDS catalyst under plasma discharge, while a lower temperature is required under conventional thermal oxidation. This is explained by the presence of metal particles, which could be responsible for the limitation in O-atom formation under plasma.

Highlights

The hydrodesulfurization (HDS) process is one of the most important processes used in a refinery to remove sulfur-containing compounds due to worldwide environmental policies and the requirement to limit the sulfur content in gasoline and diesel fuels at 10 ppm [1,2]
The regeneration of a coked HDS catalyst was investigated using a dielectric barrier discharge (DBD) plasma reactor with a pin to plate geometry, the catalyst being used as a wafer and deposited at the surface of the dielectric material
We show in this study that 70% of coke was eliminated after 130 min of plasma treatment under a mixture of helium and oxygen (He–O2 : 80–20 mL/min) and a deposited power of 30 W

Summary

Introduction

The hydrodesulfurization (HDS) process is one of the most important processes used in a refinery to remove sulfur-containing compounds due to worldwide environmental policies and the requirement to limit the sulfur content in gasoline and diesel fuels at 10 ppm [1,2]. HDS reaction is carried out in fixed bed reactors at a temperature range from 300 to 400 ◦ C and hydrogen pressure from 3 to 13 MPa. The most widely employed catalyst for the hydrodesulfurization process is cobalt-molybdenum supported on alumina [3,4]. The catalyst active in hydrotreating is obtained after a sulfidation step leading to the formation of MoS2 slabs [5] and the so-called “CoMoS active phase”. Where cobalt decorates the edges of MoS2 slabs [6]. The hydrotreating catalyst deactivation is mainly due to coke accumulation in the pores of the catalyst [7,8], necessitating a replacement of the catalyst and, if possible, its regeneration, generally performed in a separate zone

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