Effect of the Preparation of Pt-Modified Zeolite Beta-Bentonite Extrudates on Their Catalytic Behavior in n-Hexane Hydroisomerization

Abstract

Four different types of shaped catalysts with controlled deposition of platinum and the same composition were prepared by extrusion of beta zeolite agglomerated with bentonite as an aluminosilicate clay binder. The catalysts were characterized using mechanical strength tests; scanning electron microscopy for morphology; transmission electron microscopy for porosity and periodicity; nitrogen physisorption for surface area, pore volume, and pore size distribution; and Fourier transform infrared spectroscopy using pyridine as a probe molecule to elucidate the presence, strength, and amount of Brønsted and Lewis acid sites. Elemental analysis was carried out using energydispersive X-ray microanalysis. Activity and selectivity of catalysts in the isomerization of n-hexane were evaluated using a fixed bed reactor at 200−350 °C. At low temperature, the performance of metal/acid bifunctional shaped catalysis was strongly affected by the metal-to-acid site ratio. This ratio and the total acidity were strongly influenced by the preparation method of the shaped catalysts, while the textural properties were comparable. The highest conversion of n-hexane and selectivity to C 6 isomers (comprising all branched isomers, such as methyl pentane and dimethylbutane) was obtained with extrudates prepared via in situ synthesis with platinum located on the zeolite. The extrudates prepared in this way have the highest metal-to-acid site ratio and their closest proximity, albeit the lowest mechanical strength.

Synthesis of menthol from citronellal over supported Ru- and Pt-catalysts in continuous flow

“…). 24 A slightly lower specific surface area was obtained for 2 wt% [Pt/ (bentonite) + H-beta-25] extrudates than that for the corresponding powder mixture, 18 which can be explained by compaction during extrusion. The specific surface areas of the catalysts used in the batch reactor are shown in Table S3.…”

“…The highest Brønsted acidity was found in 2 wt% [Pt/(H-beta-25 + bentonite) post synthesis] when Pt was introduced on the shaped body, while the lowest was found in Pt/H-beta-25 which was extruded with bentonite (2 wt% [Pt/(H-beta-25) + bentonite]), clearly showing that the preparation method has a pronounced effect on acidity. 18 It is also interesting that the concentration of Brønsted acid sites in 2 wt% [Pt/ (bentonite) + H-beta-25] and 2 wt% [Pt/(H-beta-25) + (Table 3), while the other catalysts exhibited a metal loading close to the nominal loading with Pt more equally distributed across extrudates. 18 For Ru and Pt catalysts used in the batch reactor for comparison with continuous operation, the metal loadings were slightly different than the nominal loadings and the SiO 2 / Al 2 O 3 ratios as expected (Table S5 †).…”

“…18 It is also interesting that the concentration of Brønsted acid sites in 2 wt% [Pt/ (bentonite) + H-beta-25] and 2 wt% [Pt/(H-beta-25) + (Table 3), while the other catalysts exhibited a metal loading close to the nominal loading with Pt more equally distributed across extrudates. 18 For Ru and Pt catalysts used in the batch reactor for comparison with continuous operation, the metal loadings were slightly different than the nominal loadings and the SiO 2 / Al 2 O 3 ratios as expected (Table S5 †).…”

“…The synthesis of shaped Pt-and Ru-extrudates containing 30 wt% aluminosilicate clay bentonite from VWR International as a binder was the same as the previously published procedure. 18 Based on the previous studies, [18][19][20] the zeolite/ binder weight ratio of 70/30 has been found suitable for easy shaping of the catalyst by extrusion to achieve strong and stable extrudates. All materials were crushed and sieved into a fraction <63 μm in a vibratory micro mill (Fritsch).…”

“…A similar study was already conducted for n-hexane hydroisomerization over a Pt-catalyst. 18 In other publications of the authors, citronellal cyclization was carried out in a continuous mode over extrudates based on proton forms of beta and Y zeolites with different types of binders. 19,20 In this work, the previous studies were extended to also include hydrogenation of isopulegol.…”