Gilbert Sapaly

Monodimensional tubular medium pore molecular sieves for selective hydroisomerisation of long chain alkanes: n-octane reaction on ZSM and SAPO type catalysts

Abstractn-octane has been hydroisomerised at 523 K on ZSM-12, 48 and 22, SAPO-5, 11, 31 and 41 containing Pt–Pd metal function. The materials were prepared with hydrothermal methods, and characterized. Selectivities to C8 isomers ranged from 99 to 50% maximum yield around 80% being reached on SAPO-11, 31 and 41, ZSM-22 and 48. Among the various C8 isomers 2-MeC7 was preferentially formed. Such selectivity was interpreted in terms of transition state shape selectivity at the pore mouths. To further corroborate these interpretations the reaction of 2-MeC7, 3-MeC7, 4-MeC7, 2,5-diMeC6, 2,2,4-TMP on the previous catalysts was also investigated. Determination of the respective reaction rates of these molecules, as well the product distribution analysis allowed to reinforce the concept of transition state shape selectivity at the pore mouths.

Revisiting Ga2O3/H-ZSM-5 propane aromatization catalysts

Oxidative or reducing treatments at 873 K of Ga2O3/H-ZSM-5 (Si/Al = 13 or 60) cause a change in H+ concentration as evidenced by IR spectroscopy of OH groups at 3610 cm−1; this change is nicely correlated to the variation ofm-xylene isomerisation rate.

On the Role of Ga, Pt, PtCu and PtGa in HZSM-5 for the Cyclisation of Propane into Aromatics

The reaction of propane and propene over HZSM-5, Ga HZSM-5, PtHZSM-5, PtCu HZSM-5 and PtGa HZSM-5 catalysts have been comparatively investigated. From the data obtained it is shown that the conversion of propane is favoured over Pt and Ga based zeolites, Ga HZSM-5 showing the highest selectivity towards aromatics. The aromatic formation proceeds through propene, oligomers, dienes, trienes intermediates over Ga based catalysts, while on Pt based catalyst the main path is probably through the formation of cycloalkanes following the dehydrogenation into aromatics. Furthermore Pt favours the hydrogenolysis reactions thus lowering the selectivity to aromatics. Alloying Pt with Cu or with Ga suppress the hydrogenolysis reaction with subsequent increase of the aromatic selectivity.

Aromatization of n-Octane over Pt Based Silicalites: The Influence of Pt Loading and of Added Indium on the Product Distribution in The C8 Aromatics

Abstract The cyclisation of n-octane has been studied over Pt/Silicalite and Pt/In-Silicalite catalysts. Small metallic or bimetallic particles located inside the pores are formed. The aromatic product distribution which would result from direct C 6 ring closure changed with Pt loading as well with the addition of indium. Direct C 6 ring closure over Pt/Silicalite favors ethylbenzene with respect to o-xylene, the selectivity to ethylbenzene increased with Pt loading and with added In. This phenomenon is attributed to the larger diffusion rate of ethylbenzene in the silicalite channels.

Dual Function Mechanism of Alkane Aromatization over H-HZSM-5 Supported Ga, Zn, Pt Catalysts: Respective Role of Acidity and Additive

The propane reaction over H-ZSM-5, Ga-HZSM-5, Zn-HZSM-5 and Pt-HZSM-5 catalysts was studied. The activity of these catalysts increased with the acidity and with the addition of Ga, Zn or Pt. The highest selectivity towards aromatics was found over Ga-HZSM-5 (or Zn) catalysts. It was demonstrated that the role of additives (Ga, Zn, Pt) was to increase the rate of propane dehydrogenation, thus favouring C 3 oligomerization. Aromatization resulted in parallel path formation of dienes, trienes over the additive component and cycloalkanes followed by hydrogen transfer over acid sites. The intrinsic dehydrogenating properties of Ga (or Zn) supported on ZSM-5 was investigated by studying the reaction of propane at low conversion. The activity of gallium (or zinc) for dehydrogenation apparently increased with increasing zeolite acidity. The results are interpreted with a mechanism where C 3 H 7 + alkyl species formed on gallium (or zinc) exchanges with H + , the simultaneous step intervenes in the propane dehydrogenation.