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The synthesis and characterization of a new solid acid, tungsten oxide/silica gel, is described and different procedures for its preparation compared. Characterization includes the combined calorimetric and adsorption isotherm analysis, cal-ad, providing equilibrium constants, enthalpies and amounts of the different acid sites on the solid. The solid acid is shown to catalyze the Beckmann rearrangement of cyclohexanone oxime to -caprolactam. Competing pathways that depend on strength and the industrial significance of this intermediate for Nylon 6, make this an ideal reaction to show the relationship between acid catalysis and solid acidity. The utility of the cal-ad procedure in probing catalytic reactivity is illustrated by comparing the acidity of the original catalyst, the regenerated catalyst and a catalyst prepared by conventional means. The strength and number of acid sites correlate to selectivity and activity. |
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