PtZn intermetallic nanoalloy encapsulated in silicalite‐1 for propane dehydrogenation

Abstract

Propane dehydrogenation (PDH) is one of the most effective methods to produce propylene. But the industrial Pt‐based catalysts often suffer from short‐term stability under the high temperature reaction environment (500–700°C) via sintering and coke deposition. Herein, stable PDH reaction in high propylene yield has been achieved by the confinement of Pt–Zn intermetallic alloys (IMAs) in the channels of silicalite‐1. Single‐site Zn in the MFI framework was found to play a key role on assisting and stabilizing the PtZn IMAs for efficient PDH. By the cooperative action of the spatial confined PtZn IMAs and the lattice confined framework Zn, high propylene selectivity (>99%) without obvious deactivation was realized on the as‐developed catalyst (PtZn@S‐1) under 600°C even after 90 h. The low deactivation constant (0.003 h−1) was 6 times lower than that of the industrial PtSn catalyst.

Dehydrogenation of Propane and n-Butane Catalyzed by Isolated PtZn4 Sites Supported on Self-Pillared Zeolite Pentasil Nanosheets

“…This suggestion is based on the smaller Pt–Zn CN for the SPP-supported than for the DeAlBEA catalyst, as indicated by the EXAFS data. We further note that the literature shows that the value of CN for Pt–Zn decreases from 7 to 8 for a Pt 1 Zn 1 intermetallic alloy ,, to 4–6 for (Si-O-Zn) 4‑6 Pt-DeAlBEA and to about 4 for the (Si-O-Zn) 4‑5 Pt-SPP, consistent with the increase in the specific activity of these catalysts. It is also possible that differences in the Pt–Zn–O bond angles for Pt supported on SPP vs DeAlBEA alter the electron density on Pt in a manner that contributes to the superior activity of Pt anchored by Zn on SPP.…”

Framework Zr Stabilized PtSn/Zr‐MCM‐41 as a Promising Catalyst for Non‐oxidative Ethane Dehydrogenation

“…[ 43 ] Propylene is a good indicator of alkene's chemisorption property on catalyst. [ 14 ] C 3 H 6 ‐TPD curves in Figure 3c directly indicate that the best PtSn/ZrM catalyst shows the weakest adsorption capacity of alkene. The easier removal of ethene product from active sites for PtSn/ZrM is therefore identified, which is important for the alleviation of ethene's deep dehydrogenation and polymerization to coke, and the following coverage of active sites.…”

“…[ 11 ] Aggregated particles with less active sites exposed on the surface and phases like PtSn 3 that are low‐active for dehydrogenation of alkanes may generate during reduction and reaction, due to the high operation temperature and different mobility of Pt and Sn. [ 12‐13 ] To maintain dehydrogenation efficiency, PtSn phase segregation and metal sintering must be minimized, [ 14‐17 ] in which the supports play an important role by regulating the geometric and electronic structure of PtSn.…”

Advances in zeolite-supported metal catalysts for propane dehydrogenation

“…Liu and co-workers prepared Pt–Zn IMA nanoparticles in silicalite-1 zeolites by introducing Pt(NH 3 ) 4 (NO 3 ) 2 and Zn(NO 3 ) 2 in the initial synthesis gel of the zeolites. 87 XANES and EXAFS measurements revealed that each Pt atom was surrounded by about seven Zn atoms, which was very close to that in Pt1Zn1 IMA with eight Zn atoms surrounding the isolated Pt atoms. The TEM measurements showed that the mean size of the Pt–Zn nanoparticles was approximately 2.4 nm and the lattice spacing of the Pt–Zn nanoparticles was 0.221 nm, which matched the interplanar distance of the (111) plane of Pt1Zn1 IMA ( P 4/ mmm ).…”