Deactivation and regeneration

Catalyst deactivation is the gradual loss of the catalyst s ability to convert the feed into useful products. Catalyst activity is a measure of the relative rate of feedstock conversion. In practical terms it is the temperature required obtaining a fixed conversion. As the run progresses, the catalyst loses activity. Catalyst will lose activity in several ways described below. 

The decay of catalytic performance in the Beckmann rearrangement with time on stream is a major and common problem associated with all types of catalyst. Two main reasons are suggested for the deterioration in activity-coke formation and irreversible adsorption of basic products. 

The irreversible adsorption of basic products is reported to be common with zeolites. Aucejo et al. reported that the decay of the catalyst was because of the poisoning of the acid sites by basic compounds, rather than deposition of coke 

The deactivation of B-MFI catalyst was not attributed to carbon deposition but to pore-blocking caused by an enrichment of nitrogen-containing species inside the pore system [27]. It was assumed that these species were formed by oligomerization or polymerization of alkene nitriles. If this is so the reaction before deae-tivation occurs mainly inside the pores of the MFI zeolite. 

For B2O3-based catalysts, in addition to the mechanism already described for the loss of selectivity, evidence has been reported of an additional process whereby the selective sites are converted to amorphous boron species [59] or glassy melt [5]. 

Discordant results are also reported on rates of deactivation and on means of reactivation again, in view of the variety of catalysts and conditions used, this should not be a surprise. However, it is necessary to explore the origins of these differing results, and of the explanations applied to them. 

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Aiello, R. et al., Hydrogen production via direct cracking of methane over Ni/Si02 Catalyst deactivation and regeneration, Appl. Catal. A General, 192, 227, 2000. 

Chen et al,33 studied the deactivation of Zr02-promoted cobalt on silica in the FTS using a fixed bed reactor at realistic reaction conditions and high conversions (65-90%). A fraction of the lost activity was regained by a re-reduction, and the selectivity was reported to be unaffected by deactivation and regeneration. The authors identified hydrated cobalt silicates using IR and XRD analyses, and suggested that these species caused the permanent deactivation. 

D.Y. (2006) Isomerization of n-butane to isobutane over Pt-modified beta and ZSM-5 zeolite catalyst catalyst deactivation and regeneration. Chem. Eng. ]., 120, 83-89. 

The deactivation and regeneration of the catalyst are also important processes in the industrial production of the caprolactam by the Beckmann rearrangement and have been... 

Esr investigations were done of catalysts samples with reactants adsorbed at room and at reaction temperature. Also the preparations of deactivated and regenerated catalyst were studied. From all studied nitro compounds only the following nitrobenzene (parameters of esr signal g = 2.0031 , a H v = 7 Gs inten-... 

Fig. 1. Esr of paramagnetic species on deactivated and regenerated catalyst surface, higher than the one measured for the ion radical (B on Fig. 1). Most probably...

Fundamental description of deactivation and regeneration of acid zeolites... 

The fundamental description of coking, deactivation and regeneration of zeolite catalysts will be mainly based on results obtained on acid zeolites, coke being formed during gas phase transformation of hydrocarbons. 

A study of the deactivation and regeneration behaviour and related catalytic properties of modified zeolite catalysts... 

Moulijn JA, van Diepen AE, Kapteijn F. Deactivation and regeneration. In Ertl G, Knozinger H, Weitkamp J, editors. Handbook of heterogeneous catalysis. 2nd ed. Weinheim Wiley-VCH Verlag GmbH Co. KGaA 2008. p. 1-18. 

Saib AM, Moodley DJ, Ciobica IM, et al. Fundamental understanding of deactivation and regeneration of cobalt Fischer-Tropsch synthesis catalysts. Catal Today. 2010 154 (3-4) 271-82. 

The nature of many high-temperature hydrocarbon reactions which potentially can benefit from inorganic membrane reactors (particularly catalytic membrane reactors) is such that the catalysts or the catalytic membranes are subject to poisoning over time. Deactivation and regeneration of many catalysts in the form of pellets are well known, but the same issues related to either catalyst-impregnated membranes or inherently catalytic membranes are new to industrial practitioners. They are addressed in this section. 

Development of catalytic wood fired boiler Integration, deactivation and regeneration of net-based catalysts... 

Figure 4 Change in the incremental specific surface between deactivated and regenerated net-catalyst (same sample).

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