To develop an efficient Ni-based steam reforming catalyst
for tar
removal from the products of biomass gasification, Ni/Ce0.8Zr0.2O2 nanorods were designed. The Ni/Ce0.8Zr0.2O2 nanorod was used as a catalyst
in steam reforming of toluene, which was regarded as a model compound
of biomass gasification tar. At gas hourly space velocity (GHSV) of
24,000 h–1 and Ni loading of 5 wt %, the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst achieved
100% of toluene conversion at 600 °C. After 10 h of operation,
toluene conversion still reached 87.6%, and the carbon deposition
rate was only 1.9 mg/gcat h–1. The experimental
results demonstrated that the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst showed much higher catalytic activity
and coking resistance than other Ni-based catalysts reported in the
literature. Through different characterization technologies and density
functional theory calculations, it was confirmed that the excellent
catalytic performance was attributed to the strong metal-support interaction
(SMSI) between Ni and the {100} facet of Ce0.8Zr0.2O2. The special surface structure of {100} allowed Ni
atoms to anchor to the surface oxygen vacancies and maintained its
reduced state by electron transport between surface atoms. The anchored
Ni facilitated oxygen vacancies formation and H2O dissociation
on the support, while the support modulated the electronic structure
of Ni, which promoted its ability to toluene activation.
The catalytic behavior of Bi‐impregnated HZSM‐5 zeolites in propylene aromatization and the surface properties of the zeolites were determined by microreactor, XRD, XPS, NH3‐TPD and IR‐TPD. The mechanism of the reaction and the effect of surface properties of the zeolites on the reaction were also investigated. Experimental data showed that Bi‐impregnation made the strength of B‐acid sites decrease, the strength of L‐acid sites and the concentration of both strong B‐acid sites and strong L‐acid sites increase. Bi‐impregnation also induced sub‐strong acid sites. These were the factors that made the aromatic products of the reaction increase. The strong interaction between the impregnant and zeolite surface reached maximum at Bi2O3 = 3.5 wt%. Above this value, covering effect of impregnant caused a decrease of aromatic products.
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