Towards a New Oxidation Process Using Ozone to Regenerate Coked Catalysts

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. ABSTRACTThis work focuses on the regeneration of a zeolite catalyst from industry deactivated by fouling with coke. To replace high temperature combustion, a common and energy intensive process, an oxidation process under milder conditions (50°C-200°C) has been investigated using ozone. Coked zeolite has been oxidized by an ozone stream in a fixed bed reactor, and regeneration kinetics was followed by analyzing carbon content of the particles and ozone concentration at the outlet. The effects of temperature, time on stream and ozone inlet concentration on carbon removal efficiency were studied. Moreover, elemental analysis showed that a maximum of 74.3% of carbon could be removed from the coked catalyst after 6.5 h. Moreover, the total specific surface area, the pore size distribution and the total pore volume (mainly mesopores) have been evaluated on coked and regenerated samples.

Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

“…The most common technique used for this measure is the N 2 adsorption and desorption experiment. Comparison of results for a fresh and deactivated catalyst emphasizes the direct impact of carbon deposition on the catalyst surface area and pore characteristics [149]. During the catalytic pyrolysis of PE in a conical-spouted bed reactor carried out by Elordi et al with different zeolites, coke deposition led to the reduction of the BET surface area, 19% and 39% for HZSM-5 and HY zeolites, respectively, as well as the micropore area [71].…”

“…Khangkham et al reported the apparition of a plateau after 2 h, suggesting that coke removal is not complete [148]. Richard et al also found that a maximum of 74.3% of coke could be removed from deactivated catalyst after 6.5 h [149]. This observation is explained by the diffusion limitations due to the instability of the created oxidizing species, causing their rapid degradation before they reach the unreacted coke surface.…”

“…The most common technique used for this measure is the N2 adsorption and desorption experiment. Comparison of results for a fresh and deactivated catalyst emphasizes the direct impact of carbon deposition on the catalyst surface area and pore characteristics [149]. During the catalytic pyrolysis of PE in a conical-spouted bed reactor carried out by Elordi et al with different zeolites, coke deposition led to the reduction of the BET In spite of the overall structure and composition of the catalyst, the determination of the surface area and volume of pores is very important for the characterization of solid catalysts since these parameters have been proved to be correlated with catalytic activity [77,79].…”

“…Elemental analysis is also used to determine regeneration process efficiency via calculating carbon removal proportion. Richard et al used this criterion to evaluate the influence of ozonation operating parameters for the regeneration of industrial coked zeolites and achieved a maximum of 74.3% carbon removal [149]. The main limitation to this analysis is the potential presence of hydroxyl groups or water molecules within the catalyst that may distort the actual coke composition [183].…”

Regeneration of catalysts deactivated by coke deposition: A review

“…Moreover, they observed that coke removal with O2 starts on the metal sites, while that with O3 starts on the alumina support [63]. Furthermore, temperatures higher than 150 °C were not beneficial due to the strong diffusion constraints of O3 inside the zeolite particles, decomposing O3 rapidly [64]. Khangkham et al [65] investigated the regeneration of coked ZSM-5 after polymethyl methacrylate cracking, using O3 at low temperature.…”