Understanding zeolite deactivation by sulfur poisoning during direct olefin upgrading

Abstract

The presence of sulfur contaminants in bitumen derived crude oils can lead to rapid catalyst deactivation and is a major problem faced by downstream refiners. Whilst expensive hydrotreating steps may remove much of the sulfur content, it is important to understand how catalyst deactivation by sulfur poisoning occurs and how it may be mitigated. Here we report a mechanistic study of sulfur poisoning over a zeolite catalyst promoted with silver and gallium Lewis acids. Olefin upgrading, an essential process in the refinement of heavy oils, is used as a model reaction. Access to the zeolite inner pores is blocked by bulky, weakly adsorbed sulfur species. Pore access and thus catalyst activity is restored by increasing the reaction temperature. We also show that a simple alkaline treatment greatly improves both the sulfur tolerance and performance of the catalyst. These findings may enhance the rational design of heterogenous catalysts for olefin upgrading.

Inhibiting the Dealkylation of Basic Arenes during n-Alkane Direct Aromatization Reactions and Understanding the C6 Ring Closure Mechanism

“…The surface reaction mechanism involved will be of great interest in the next investigation. On the basis of previous works 41 and the knowledge that alkenes are undoubtedly intermediates on moving from n-alkanes to aromatic hydrocarbons under nonoxidative conditions, we move to study varying alkene species under the same reaction conditions as before. Straightchain monoalkenes, straight-chain dienes, and cyclic monoalkenes at different chain lengths (C 6 −C 8 ) are examined to elucidate the possible reactive intermediates.…”

“…Despite the user often employing multiple exchanges, it is unlikely that all the hydrogen occupied acid sites are replaced by K, leaving the catalyst slightly acidic and aromatization reactions likely to see by-products resulting from cracking, oligomerization, and C5 ring closure. [39][40][41] In order to make further improvement, we optimise the catalyst by loading K in excess of the IE limit by the application during synthesis (K was added to precursor mixture prior to hydrothrermal synthesis of MFI support to achieve desired mgK/gcatalyst). KCl was the neutral salt used to avoid desilication of the support during synthesis.…”

Catalytic co-pyrolysis of LDPE and PET with HZSM-5, H-beta, and HY: experiments and kinetic modelling

“…The presence of carbonium ions leads to isomerization and cracking reactions for the formation of branched paraffins and olefins. 68,69 During the catalytic copyrolysis of LDPE and PET, interactions were quite evident that resulted in a decrease in selectivity to benzene and C 4 -C 10 paraffins and olefins with a concomitant increase in selectivity to alkylated benzenes and polyaromatics. It can be speculated that the paraffins and olefins react with either benzene or phenyl radicals via condensation and alkylation reactions, thereby increasing the selectivity to alkylated benzenes and polyaromatics.…”

Optimizing temperature and introducing new process arrangements for elevating clay's longevity based on the known poisons in the separation process of trace olefins from aromatics

“…Production of these components is accompanied by the production of unsaturated aliphatic components that can be harmful to downstream units and poison their catalysts 1‐4 . Clays and hydrotreating catalysts have been widely used for removing these trace aliphatic components from aromatics 5‐8 . Clay treatment is simple but the particular clay used has a limited lifetime.…”

“…[1][2][3][4] Clays and hydrotreating catalysts have been widely used for removing these trace aliphatic components from aromatics. [5][6][7][8] Clay treatment is simple but the particular clay used has a limited lifetime. Hydrotreating catalysts could remove olefins and have a longer service life, but hydrogenation is costly and may lead to loss of aromatics.…”