期刊
MATERIALS
卷 14, 期 4, 页码 -出版社
MDPI
DOI: 10.3390/ma14040968
关键词
commercial silica; modified silica; iridium catalysts; hydrogenation reaction
类别
资金
- National Science Center (Poland) [2017/27/N/ST5/02042]
- European Union through the European Social Fund under the Operational Program Knowledge Education Development [POWR.03.02.00-00-I023/17]
- French government through the Programme Investissement d'Avenir [ULNE/ANR-16-IDEX-0004 ULNE]
Commercial silica modified with NH4F or NH4Cl salts and thermally treated can generate acidic sites and alter structural properties, along with additional porosity. NH4F solution leads to decreased specific surface area, increased pore diameter, and higher total acidity. The resulting acid sites' number and strength depend on the anion in the ammonium salt and concentration of the solution. The NH4F-modified silica supported iridium catalyst exhibits higher activity in toluene hydrogenation due to the generation of adsorption centers for toluene.
The modification of commercial silica with solutions of NH4F or NH4Cl salts, followed by thermal treatment, enabled generation of the acidic sites in SiO2 and changed its textural properties. The use of ammonium salts solution also caused the generation of additional porosity. Using NH4F solution caused significant decrease in the specific surface area and the increase in the average pore diameter. The number and strength of resulting acid sites depend on the nature of anion in the applied ammonium salt and the concentration of salt solution. It has been found that the sample treated with NH4F presented higher total acidity (TPD-NH3) and the amount as well as the strength of acid sites increased with the concentration of the used modifier. As modified amorphous SiO2 materials used as a support for iridium (1 wt %, Ir(acac)(3)) nanoparticles permitted to obtain highly active catalysts for toluene hydrogenation under atmospheric pressure. The highest activity (expressed as the apparent rate and TOF) was obtained for iridium catalysts supported on silica modified by NH4F with the highest acidity. The modification of silica with NH4F favors the generation of centers able to adsorb toluene, which results in higher activity of this catalyst.
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