A Highly Effective Pt and H3PW12O40 Modified Zirconium Oxide Metal–Acid Bifunctional Catalyst for Skeletal Isomerization: Preparation, Characterization and Catalytic Behavior Study

Abstract

A series of metal-acid bifunctional catalysts with varying quantities of platinum and tungstophosphoric acid (TPA) supported on zirconium oxide were prepared by co-impregnation method. In skeletal isomerization of n-pentane using catalyst with 1% Pt and 30% TPA loadings the conversion of the reactant which was close to the equilibrium conversion reached ca. 65% and the selectivity towards the product was as high as ca. 97% at atmospheric pressure and relatively low reaction temperature (200°C). The phase structure, chemical structure, surface physicochemical properties, surface element oxidation states and hydrogen reduction behavior of the catalysts were wellcharacterized via XRD, FT-IR, N 2 adsorption-desorption determination (BET), XPS and TPR. The effects of Pt and TPA loadings, calcination temperature, reaction temperature and weight hourly space velocity (WHSV) on the catalytic performance were investigated. In addition, a long period catalytic stability test of the catalyst with optimal Pt and TPA loadings was carried out, which indicated that the bifunctional catalyst was in possession of good stability in skeletal isomerization along with high catalytic activity under the experimental conditions.

The Support Effect over Pt–H3PW12O40 Based Metal-Acid Bifunctional Catalysts on the Catalytic Performance in n-Pentane Isomerization

“…c-Al 2 O 3 showed two characteristic diffraction peaks centered at 37.5°and 45.9° [18]. A wide diffraction structure peaked at 22°for SiO 2 , which is typical of amorphous nature of the material, was observed, There are two crystal phase corresponding to ZrO 2 , which are located at 28.1°and 31.4°f or the monoclinic phase and at 30.1 for the tetragonal phase [16]. When Pt and TPA were loaded new diffraction peaks, which could be attributed to TPA, emerged on the three supports except the characteristic peaks for the support themselves.…”

“…5b. At 350°C, the crystal phase of ZrO 2 was mainly tetragonal (2h = 30.1°) [16]. The monoclinic crystal phase appeared when the calcination temperature was improved to 450°C (2h = 28.4 and 31.4°) [16].…”

“…After impregnation for 70 min at room temperature, the solvent was evaporated and the solids obtained were dried at 110°C overnight and calcined at 300°C for 5 h. The Pt and TPA loadings were constant of 1% and 30% according to our previously reported paper [16].…”

“…Moreover the benefit of Pt addition was also observed in the absence of hydrogen. Recently, we evaluated the catalytic performance of MCM-41 [15] and zirconia [16] supported Pt-TPA catalysts in hydroisomerization of n-pentane and observed high catalytic activity and iso-pentane selectivity.…”

The comparison of two classes of bifunctional SBA-15 supported platinum–heteropolyacid catalysts for the isomerization of n-hexane

“…The metal phase, in the presence of hydrogen, allows for a better stabilization of the catalytic activity as well as significant enhancement of the selectivity for isomerization by disfavoring the bimolecular mechanism pathway responsible for coke formation. ‡ 4 Nowadays, the industrial catalysts consist of platinum supported on chlorinated alumina or acidic zeolites such as H-mordenite. 5,6 Although the former can operate at temperatures as low as 120-180 1C, it is highly sensitive to contaminants in the feed (i.e.…”