Aromatization over platinum/zeolite L catalysts : the effect of oxygenates

In 1980, Bernard reported that platinum dispersed on zeolite LTL (Pt/KU had exceptionally high selectivity for the aromatization of n-hexane to benzene. The selectivity was ca. 95 at 99 conversion of n-hexane. This Pt/KL catalyst has been extensively studied to determine the reasons for the exceptional stability and benzene yields relative to platinum supported on silica (Pt/Si0₂ ) and alumina (Pt/Al₂0₃). The Pt/KL catalyst was found to be monofunctional with all the activity occurring on platinum metal clusters inside the pores of zeolite L. The catalyst exhibits excellent stability and the Aromax Process developed by Chevron Ltd., using I a barium doped Pt/KL catalyst, PtBa/KL, has been reported to operate continually for the equivalent of one year during accelerated deactivation testing at 450°C and a hydrogen partial pressure of 6 bar. However, sulphur-containing I compounds such as thiophene, result in rapid and irreversible deactivation of the catalyist due to sintering of platinum clusters. Thus the level of sulphur-containing I compounds, especially thiophene, must be kept below 50 ppb of the feed to avoid deactivation by sintering. SASOL Ltd. may be in a unique position to use Pt/KL as a catalyst for the aromatization of hexanes and heptanes to benzene and toluene respectively, as their products which are produced by the Fischer-Tropsch process are sulphur free. However, a substantial amount of oxygenates are formed in the Fischdr-Tropsch process and as yet no study has been undertaken to determine the effect of these compounds on the activity and selectivity of the catalyst.

Grantor dc:publisher.institution

Department of Chemical Engineering

Year dc:date.issued

1997

Author dc:creator

• Nash, Robin John

Advisor dc:contributor.advisor

• Dry, Mark

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/9492

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/9492