화학공학소재연구정보센터
Applied Catalysis A: General, Vol.109, No.1, 147-165, 1994
Dehydration of Glucose to Organic-Acids in Microporous Pillared Clay Catalysts
Glucose is an abundant and renewable feedstock for chemicals production. The objective of this study was to determine if microporous pillared-clay catalysts could promote the shape-selective, partial dehydration of glucose to organic acids. Iron-, chromium-, and aluminum-pillared montmorillonite catalyst powders were prepared. The iron-pillared montmorillonite had the most open pore structure in the > 10 Angstrom range. Pore slit widths of at least 10 Angstrom allowed the 8.6 Angstrom glucose molecule to diffuse and react directly within the catalyst micro- and meso-pores. Each catalyst powder was reacted with 0.75 M glucose solution (4 g catalyst/150 ml) within a well-mixed Parr autoclave reactor for 0-24 h at temperatures ranging from 130-170 degrees C. All of the catalysts tested promoted four acid-catalyzed reactions : isomerization of glucose to fructose, partial dehydration of glucose to 5-hydroxy-methylfurfural (HMF), rehydration and cleavage of HMF to formic acid and 4-oxopentanoic acid, and coke formation. The Fe-pillared montmorillonite provided the highest glucose conversion rate, with 100% glucose conversion attained within 12 h at 150 degrees C. This catalyst also provided the lowest selectivity of the HMF (the reaction intermediate) and the highest selectivity of formic acid (the final product) in the bulk phase at an optimum temperature of 150 degrees C. Apparently, the fraction of pores in the 10-25 Angstrom range allowed glucose to diffuse into the microporous matrix, but also trapped the bulky HMF molecule within the micropores, thus directing the reaction scheme to the final organic acid products. However, 4-oxopentanoic acid selectivities were low ( < 20%), and coke formation was as high as 0.4 g coke/g catalyst, implying carbonization of final reaction products.