Issue 6, 2012
From the journal:

Catalysis Science & Technology

Role of internal coke for deactivation of ZSM-5 catalysts after low temperature removal of coke with NO2

Katia Barbera,a   Søren Sørensen,b   Silvia Bordiga,a   Jørgen Skibsted,b   Henrik Fordsmand,c   Pablo Beatoc  and  Ton V. W. Janssens*c  

* Corresponding authors

a Department of Inorganic, Physical and Materials Chemistry, INSTM Centro di Riferimento and NIS Centre of Excellence Università di Torino, via Quarello 11A, 10125 Torino, Italy

b Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C, Denmark

c Haldor Topsøe A/S, Nymøllevej 55, DK-2800 Lyngby, Denmark
E-mail: tvj@topsoe.dk
Tel: +45 22754622

Abstract

By treating a deactivated ZSM-5 catalyst for the conversion of methanol to hydrocarbons with NO2, coke deposits can be removed at around 350 °C, which potentially enables catalyst regeneration at 350–400 °C, which is about 200 °C lower compared to a conventional regeneration in oxygen. To evaluate the regeneration with NO2 at 350 °C, the activity of a used ZSM-5 catalyst was measured after treatment with 1% NO2/He and 0.7% NO2/7% O2/He at 350 °C, and 2% O2/He at 550 °C. After the treatments with NO2 at 350 °C, some activity was restored, but the catalysts showed a fast deactivation. Temperature programmed desorption of ammonia and 27Al MAS NMR measurements indicate that the amount of framework aluminium in the regenerated catalysts is about 60% of that in the fresh catalysts, and some redistribution of the aluminium takes place. Gravimetric temperature programmed oxidation showed that the catalysts still contain 0.3–0.6 wt% coke. GC-MS analysis of the retained species and very high-speed 1H MAS NMR revealed that the remaining coke species are methyl benzenes, which are located inside the micropores of the ZSM-5 zeolite. It is concluded that the deactivation not only depends on the amount of coke, but also on the location of the coke in the catalyst.

Graphical abstract: Role of internal coke for deactivation of ZSM-5 catalysts after low temperature removal of coke with NO2

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Article information

DOI
https://doi.org/10.1039/C2CY00529H
Article type
Paper
Submitted
19 Dec 2011
Accepted
19 Feb 2012
First published
22 Feb 2012

Catal. Sci. Technol., 2012,2, 1196-1206

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Role of internal coke for deactivation of ZSM-5 catalysts after low temperature removal of coke with NO2

K. Barbera, S. Sørensen, S. Bordiga, J. Skibsted, H. Fordsmand, P. Beato and T. V. W. Janssens, Catal. Sci. Technol., 2012, 2, 1196 DOI: 10.1039/C2CY00529H

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