Design of Multifunctional Solid Superacid for Clean Chemical Processes

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A huge number of acid catalyzed reactions such as Friedel-Crafts reactions, esterification, hydration and hydrolysis are currently performed using liquid acids such as H_2SO_4 and A1C1_3, having several problems of high toxicity, corrosion, catalyst waste, use of large amount of catalyst, difficult of separation and recovery. The replacement of the liquid acids with the solid acids is becoming even more important in chemical and life science, since the solid acids are green with respect to corrosiveness, safety, less waste, separability, and recoverability. Water-tolerancy is a novel function of an acidic Cs salt, Cs_<2.5>H_<0.5>P_<12>O_<40> (abbreviated as Cs2.5). Comparison of adsorption amounts of water and benzene led to the following order of hydrophobicity; HZSM-5 (Si/Al = 628) > silica > Cs3 > H-ZSM-5 (Si/Al = 40) 【similar or equal】Cs2.5 > silica-alumina > alumina. Owing to the hydrophobicity, Cs2.5 was highly active for organic reactions like hydration of alkene and hydrolysis of esters and oligosugars in water. Also, Cs2.5 was efficient for the reaction of nitrile with alcohol to AT-alkylamide even in excess water. In a bi-phasic reaction system, H_3PW_<12>O_<40> (in liquid state) was exceptionally active for synthesis of diphenylmethane from formalin (aqueous formaldehyde) and benzene.