Yongzheng Duan

Effect of aluminum modification on catalytic properties of PtSn-based catalysts supported on SBA-15 for propane dehydrogenation

Abstract The catalytic properties of PtSn-based catalysts supported on siliceous SBA-15 and Al-modified SBA-15, such as Al-incorporated SBA-15 (A1SBA-15) and alumina-modified SBA-15 (AI2O3/SBA-15), for propane dehydrogenation were investigated. AI2O3/SBA-15 was prepared either by an impregnation method using aluminum nitrate aqueous solution, or by the treatment of SBA-15 with a Al(OC3H7)3 solution in anhydrous toluene. N2-physisorption, FT-IR spectroscopy, solid-state 27Al MAS NMR spectroscopy, hydrogen chemisorption, XRF, NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy and TPO were used to characterize these samples. Among these catalysts, the PtSn-based catalyst supported on AI2O3/SBA-15, which was grafted with Al(OC3H7)3, exhibited the best catalytic performance in terms of activity and stability The possible reason was due to the high Pt metal dispersion and/or the strong interactions among Pt, Sn, and the support.

Synergistic effect between Sn and K promoters on supported platinum catalyst for isobutane dehydrogenation

Abstract Catalytic dehydrogenation of isobutane has recently received considerable attention because of the increasing demand for isobutene. In this study, the synergistic effect between Sn and K on PtSnK/γ-Al 2 O 3 catalysts has been investigated by changing the content of Sn. It was found that with the presence of potassium, suitable addition of Sn could not only increase the metal dispersion, but also reduce the catalyst acidity. In these cases, the synergistic effect could also strengthen the interactions between the metal and support, which resulted in an increase in both catalytic activity and stability. In our experiments, Pt-0.6SnK/A1 catalyst exhibited the lowest deactivation rate (12.4%) and showed a selectivity to isobutene higher than 94% at the isobutane conversion of about 45.3% after running the reaction for 6 h. However, with the excessive loading of Sn, surface property of active sites and the interactions between metal and support were changed. As a result, the initial optimal ratio between the metallic function and acid function would be destroyed, which was disadvantageous to the reaction.

Effect of cerium addition on catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation

PtSnNaGa/ZSM-5 catalysts with different contents of Ga were prepared and characterized by X-ray diffraction (XRD), nitrogen adsorption, hydrogen chemisorption, ammonia temperature-programmed desorption (NH3-TPD), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed oxidation (TPO) techniques. The performances of these catalysts for propane dehydrogenation were investigated. The test results indicated that the addition of Ga not only could improve the catalytic stability and propene selectivity, but also could effectively prevent the catalysts from coking. It was found that the PtSnNaGa(0.5 m%)/ZSM-5 catalyst exhibited the best performance in terms of propene selectivity and propane conversion. The high catalytic performance was most probably attributed to the presence of Ga that could strength- en the interaction between metals and the support to stabilize the catalytic active sites.

Highly Active and Green Aminopropyl-Immobilized Phosphotungstic Acid on Mesoporous LaSBA-15 for Alkylation of O-xylene with Styrene

The Keggin phosphotungstic acid, H3PW12O40 (HPW), was successfully immobilized on the surface of mesostructured LaSBA-15 by means of chemical bonding to aminosilane groups. The catalysts were characterized by elemental analysis, N2 adsoption, TEM, DRS-UV, and FTIR spectroscopy. Characterization results suggest that the surface area decreased after grafting amino groups to silica and the structures of heteropolyanions on amine-modified LaSBA-15 was maintained. Their catalytic behaviors were investigated in the alkylation of o-xylene with styrene. Among the functionalized catalysts, when the content of amino-groups was suitable, it had the best catalytic performances in terms of yield and stability. It is worth mentioning that the catalysts could be used repeatedly without loss of the activity and selectivity during several catalytic cycles. The good stability can be attributed to the strong interaction between the amino groups on the surface of LaSBA-15 and HPW anions.Graphical AbstractThe Keggin phosphotungstic acid, H3PW12O40 (HPW), was successfully immobilized on the surface of mesostructured LaSBA-15 by means of chemical bonding to aminosilane groups. The obtained catalysts were highly effective for alkylation of o-xylene with styrene in terms of yield and stability. Compared with the HPW/LaSBA-15 catalyst, both the catalytic stability and reusability were greatly enhanced.