DEHYDRATION OF FRUCTOSE TO 5-HYDROXYMETHYLFURFURAL OVER H-MORDENITES

Dehydration of fructose to 5-hydroxymethylfurfural was performed in a batch mode in the presence of a series of dealuminated H-form mordenit es as catalysts, at 165 degrees C, and in a solvent mixture consisting of water and methyl isobutyl ketone (1:5 by volume). Under the operat ing conditions used, the reaction was not controlled by external or in ternal diffusional limitations. Fructose conversion and selectivity to 5-hydroxymethylfurfural were found to depend on acidic and structural properties of the catalysts used as well as on the micropore vs. meso pore volume distribution of those catalysts. A maximum in the rate of conversion of fructose was observed for the H-mordenite with a Si/Al r atio of 11. A maximum in the selectivity to 5-hydroxymethylfurfural wa s observed only for H-mordenites with a low mesoporous volume. The hig h selectivity obtained (> 90%) was correlated with the shape selectivi ty properties of H-mordenites (bidimensional structure), and particula rly with the absence of cavities within the structure allowing further formation of secondary products. The influence of the microporosity v s, mesoporosity on the selectivity to 5-hydroxymethylfurfural was also studied, the formation of mesopores upon dealumination procedures bei ng damaging to obtain a high selectivity. A significant increase in th e selectivity (10%) was also obtained by simultaneous extraction of 5- hydroxymethylfurfural with methyl isobutyl ketone circulating in a cou ntercurrent manner in a continuous catalytic heterogeneous pulsed colu mn reactor.