Study of Catalysts Comprising Heteropoly Acid H3PW12O40 Supported on MCM-41 Molecular Sieve and Amorphous Silica
Full article
| Общее |
Language:
Английский,
Genre:
Full article,
Status:
Published,
Source type:
Original
|
| Journal |
Journal of Molecular Catalysis A: Chemical
ISSN: 1381-1169
|
| Output data |
Year: 1996,
Volume: 114,
Number: 1-3,
Pages: 287-298
Pages count
: 12
DOI:
10.1016/S1381-1169(96)00328-7
|
| Tags |
31P NMR, Heteropoly acid H3PW12O40, MCM-41 molecular sieve, Silica, TEM, Trans-de-t-butylation of 2,6-di-t-butyl-4-methylphenol, XRD |
| Authors |
Kozhevnikov I.V.
1,2
,
Kloetstra K.R.
2
,
Sinnema A.
2
,
Zandbergen H.W.
3
,
van Bekkum H.
2
|
| Affiliations |
| 1 |
Boreskov Institute of Catalysis, 630090 Novosibirsk, Russia
|
| 2 |
Laboratory of Organic Chemistry and Catalysis, Delft University of Technology
|
| 3 |
Laboratory of Materials Science, Delft University of Technology, Rotterdamsewq 137, 2628 AL Delft, Netherlands
|
|
With the aim of obtaining pure Keggin-type heteropoly acid (HPA) species on siliceous surfaces, the preparation of HPA catalysts, comprising of 10 to 50 wt.% H3PW12O40 (PW) supported on an amorphous silica or a mesoporous all-silica molecular sieve MCM-41, was studied. The state of HPA on the siliceous surface was characterized by 31P NMR, XRD and TEM. Impregnating MCM-41 or amorphous SiO2 with an aqueous solution of PW gave catalysts with, in general, two HPA species: one with intact Keggin structure (A) and the other with a different structure (B), supposedly, H6P2W18O62 (P2W18) and/or H6P2W21O71 (P2W21). The relative amount of species A and B depends on HPA loading, with A dominating. At higher loadings, 30–50 wt.%, A is practically the only one present on the surface; at lower loadings, both species exist, the amount of B increasing as the HPA loading decreases. In contrast, catalysts prepared by impregnation with a methanol solution of HPA contained exclusively Keggin-type A over the whole range of PW loading. In the PWMCM-41 catalysts, as shown by TEM, the PW species are mainly located inside the MCM-41 pores. The B species was about 8 times as active as A in the liquid-phase trans-de-t-butylation of 2,6-di-t-butyl-4-methylphenol.