| Research Abstract |
Heterogenization of the Keggin-type heteropoly compounds was investigated to transform into insoluble, readily recoverable solid acid catalysts.
The possibility of heteropolyacid salt as solid acid catalyst for liquid-phase Friedel-Crafts reactions was studied. Among different kinds of insoluble acidic salt, K,Rb, Cs, and ammonium salts were mesoporous materials with large surface area (50-170 m2 g-1), strong acidity (H_0<-8.2), and large pore volume (0.3-0.5 mlg^<-1>). Particularly, K_<2.5>H_<0.5>PW_<12>O_<40>, Rb_<2.5>H_<0.5>PW_<12>O_<40>, Cs_<2.5>H_<0.5>PW_<12>O_<40>, Cs_<2.5>H_<0.5>PMo_<12>O_<40>, K_2H_2SiW_<12>O_<40>, CS_2H_2SiW_<12>O_<40> and (NH_4) _2HPW_<12>O_<40> worked as efficient solid acid catalysts for the liquid-phase Friedel-Crafts alkylation of benzene with benzyl chloride, and some of them could also effectively be applied to the acylation of p-xylene with benzoyl chloride or benzoic anhydride. The salt catalysts were much more active than HY,LaY,Nafion-H and Zn-promoted montmorillonite.
12-Tungstophosphoric acid (H_3PW_<12>O_<40>) and its acidic cesium salt (Cs_<2.5>H_<0.5>PW_<12>O_<40>) could be immobilized into silica matrix by means of sol-gel technique. This involves the hydrolysis of ethyl orthosilicate to afford insoluble and easily separable solid acid catalysts. The silica-included heteropoly compounds thus obtained were porous materials with mesopores and large surface areas, and were thermally more stable than an acidic ion-exchange resin, Amberlyst-15. They effectively catalyzed the hydrolysis of ethyl acetate in the liquid-phase, owing to their strong acidity. The values of thier turnover frequency were larger than those of Amberlyst-15 and H-ZSM-5. H_3PW_<12>O_<40>, when included in the silica matrix, showed higher catalytic activity than in the state of an aqueous solution.
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