Relationship between Acidity and Activity on Propane Conversion over Metal-Modified HZSM-5 Catalysts

Abstract

A systematic study of the comparative performances of different metal-impregnated HZSM-5 catalysts (Zn, Ga, Mo, Co, and Zr) for propane conversion is presented. The physicochemical properties of catalysts were characterized by means of XRD, BET, SEM, TEM, FTIR, XPS, 27Al MAS NMR, NH3-TPD and Py-FTIR. It was found that the acidities of the catalysts were significantly influenced by loading metal. More specifically, Mo-, Co- or Zr-modified catalysts showed a large metal size and low acidic density, resulting high olefin selectivity, while Zn- or Ga-modified catalysts maintained their small metal size and acidic density, and mainly reduced B/L due to the Lewis acid sites created by Zn or Ga species, resulting in high aromatics selectivity. Experimental results also showed that there is a balance between metals size and medium and strong acidity on propane conversion. Moreover, based on the different acidity of metal-modified HZSM-5 catalysts, the mechanism of propane conversion was also discussed.

Mitigating Concentration Polarization through Acid–Base Interaction Effects for Long-Cycling Lithium Metal Anodes

“… , As shown in Figure e, three bands were observed at wavenumbers of 1450, 1545, and 1490 cm –1 , which could be assigned to pyridine adsorption onto the Bro̷nsted acid site (B), Lewis acid site (L), and a common peak for both Bro̷nsted acid site and Lewis acid site, respectively (Figure S4). This result verified the existence of the surface acid sites of the ZSM-5 zeolite. To explore the regulatory roles of acid sites on the ion transport property, the molecular interaction between ZSM-5 zeolite and the electrolyte was investigated by solid state nuclear magnetic resonance (SSNMR) spectroscopy.…”

One-Step Synthesized Solid Acid Catalyst with High Zr Content for Efficient and Green PET Degradation in Supercritical CO2

“…The simulation calculations of the proton affinity of BAS and LAS on zeolite revealed that BAS exhibits a higher proton affinity, thereby playing a more positive role during the reaction process. Due to the facile adjustment of the acidic strength and acid distribution through doping other elements into zeolite, − the incorporation of metal dopants at framework sites in zeolites holds significant implications for designing novel catalysts with tailored activity. − Zhou et al prepared zeolite catalysts loaded with different metals (Zr, Ga, Mo, Co) using impregnation method for propane dehydrogenation reaction. It was found that the total acid content and B/L ratio of the catalyst exhibited varying degrees of decrease after metal loading.…”