M. Kimura, T. Nakato, T. Okuhara
Dec 31, 1997
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Quality indicators
Journal
Applied Catalysis A-general
Abstract
Abstract Hydrolysis reactions of esters, ethyl acetate, cyclohexyl acetate, 2-methylphenyl acetate, and 2-nitrophenyl acetate in the presence of a large excess of water were investigated by using various solid acids. Inorganic solid acids such as an acidic cesium salt of 12-tungstophosphoric acid Cs 2.5 H 0.5 PW 12 O 40 , H-ZSM-5, SO 4 2− /ZrO 2 , and Nb 2 O 5 , and polymer resins, Amberlyst-15, Amberlite-200C, and Nafion-H catalyzed the reactions, whereas H-Y, H-mordenite, SiO 2 —Al 2 O 3 , and γ-Al 2 O 3 were inactive. Among inorganic solid acids, Cs 2.5 H 0.5 PW 12 O 40 was most active for all reactions in the unit of the activity per catalyst weight. Cs 2.5 H 0.5 PW 12 O 40 was comparable to Nafion-H in the catalytic activity per unit acid amount of catalysts, and much more active than H-ZSM-5, SO 4 2− /ZrO 2 , and Amberlyst-15. The activities of liquid acid catalysts, such as H 2 SO 4 , H 3 PW 12 O 40 , and p-toluenesulfonic acid, per unit acid amount were less than that of Cs 2.5 H 0.5 PW 12 O 40 , although the relative activities per catalyst weight of the liquid acids were higher than that of Cs 2.5 H 0.5 PW 12 O 40 . The activity of Cs 2.5 H 0.5 PW 12 O 40 relative to the other catalysts became higher for hydrolysis of bulky esters like 2-methylphenyl acetate and 2-nitrophenyl acetate for which H-ZSM-5 was inactive, demonstrating that Cs 2.5 H 0.5 PW 12 O 40 is a widely applicable water-tolerant solid acid. When Cs 2.5 H 0.5 PW 12 O 40 was separated from the reactant solution and reused for the hydrolysis of ethyl acetate repeatedly, the reaction rate of the 5th run was more than 90% that of the 1st run, whereas the rate on SO 4 2− /ZrO 2 decreased by repeating once to become less than half that of the 1st run.