The Microstructure and Properties of Framework Zirconium Phosphates Based Nanocomposites-Catalysts of Alkane Isomerizati
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ABSTRACT The structure and surface properties of composites based upon high-surface-area framework zirconium phosphates with supported W0 3, MoO3 and Pt nanoparticles were studied by using combination of structural and spectral methods. The effect of these promoters on performance of zirconium phosphates in the reaction of pentane and hexane isomerization is considered. INTRODUCTION Recently [1-3], the procedures for synthesis of highly dispersed mesoporous framework zirconium phosphates via hydrothermal treatment (HTT) in the presence of polyethylene oxide of amorphous sols or products of mechanical activation of the mixture of solid salts were elaborated. Genesis of samples real structure as a function of the preparation procedure and nature of modifying cations (La, Si) as well as its impact on the surface acidic properties and catalytic performance in the reactions of hexane isomerization and dehydroaromatization have been studied. This work aims at synthesis of composite systems based upon those zirconium phosphates with supported WO 3, MoO 3 and Pt nanoparticles known as promoters in the reactions of paraffins isomerization, elucidation their microstructural features and surface properties as related to catalysis of the reactions of interest. EXPERIMENTAL Table 1 lists starting materials and some details of preparation procedures similar to those described earlier [1-3]. When organometallic precursors were used, I M (NHI4)2HPO4 water solution was added under stirring to 80% solution of zirconium butoxide in n-butanol or to its mixture with tetraethylorthosilicate (Si/Zr- 0.3). PEO was then added, and this mixture was stirred at room temperature for 18 hours. Suspensions of sols or activated mechanical mixtures in distilled water with addition of polyethylene oxide were kept in bombs at 175-200 315 Mat. Res. Soc. Symp. Proc. Vol. 581 ©2000 Materials Research Society
TC for 5-7 days. After HTT, the solids were separated by centrifugation, washed with ethanol and distilled water, dried at 120 'C and calcined at 400 'C. Platinum, WO3, and MoO 3 were usually supported by the incipient wetness impregnation methods from solutions of H 2 PtCl6, ammonium tungstate and molybdate, respectively, followed by drying and air calcination. For comparison, in one sample (K-8), W was added through the mechanical co-activation of crystalline cubic zirconium phosphate with solid ammonium tungstate followed by air calcination. Table 1. Parameters of synthesis and some properties of samples calcined at 400 'C. Sample'
Starting compounds 2
Specific surface m2/g
I Zr-OH, arb. un.
[Zr4÷] lamolCO/ m2
Phase Pt-CO ýtmolCO/m 2 composit ion (XRD)3
C+O 0.27 0 60 LN + ZrCI+N3P C+O 0.44 50 2%Pt/MA-2 C+O 0 30 11.2%W/MA-2 C+O 0.23 0 30 2%Pt/K-4 C+O 0.17 0 40 3.6%W+9.6%Mo/ MA-2 C+O 0.15 0 40 2%Pt/K-5 K-5* C+O K-6 0.3%Pt/K-4 C+O 0 0.63 35 0.3%Pt/K-5 K-7 C+O 20 10%W/MA-2 K-8 4) A 0.37 160 187 SiSG-32 ZrPr+TES+N2P A 0.27 66 180 0.3%Pt/SiSG-32 K-19 A 140 10%W/SiSG-32 K-32 A 110 0.3%Pt/K-32 K-33 A 0.1 100 2%Pt/K-32 K-33* 'SG and MA-- samples
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