Surface reactivity of non-hydrolytic silicophosphate xerogels: a simple method to create Bronsted or Lewis acid sites on porous supports
| Authors | |
|---|---|
| Year of publication | 2016 |
| Type | Article in Periodical |
| Magazine / Source | New Journal of Chemistry |
| MU Faculty or unit | |
| Citation | |
| Web | http://pubs.rsc.org/en/Content/ArticleLanding/2016/NJ/C5NJ02928G#!divAbstract |
| Doi | http://dx.doi.org/10.1039/c5nj02928g |
| Field | Inorganic chemistry |
| Keywords | Non-hydrolytic; sol-gel; silicon acetate; silicophosphate; xerogel; heterogeneous; catalysis; Lewis acid; Bronsted acid |
| Description | Non-hydrolytic sol-gel reactions of silicon acetates with trimethylsilyl (TMS) esters of phosphoric and phosphonic acids produce cross-linked matrices containing homogeneous dispersions of silicate and phosphoryl groups connected together by networks of Si-O-P(QO) linkages. The condensation degrees reach 80 to 90%. Residual organic groups (10 to 20%) were reacted with a variety of compounds (H2O, Me3SiOSiMe3, POCl3, SiCl4, AlMe3, Al(NMe2)(3), and AlCl3) in order to enrich the surface of these porous matrices with Bronsted (RP-OH) and Lewis (tetracoordinated Al) acid functional groups. The differences in the reactivity of RSi-OAc and RP-OSiMe3 groups were utilized for the selective modification at the silicon and phosphorus atoms. The reaction procedures were optimized and significantly porous silicophosphate materials with a high content of either hydroxyl groups or four-coordinated aluminium species were obtained. The activity and selectivity of prepared samples as catalysts for the dimerization of a-methylstyrene were tested. Excellent activities and moderate to very high selectivities were achieved suggesting the potential use of silicophosphate xerogels in heterogeneous catalysis. |
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