DIFFUSION OF GLUCOSE AND GLUCITOL IN MICROPOROUS AND MESOPOROUS SILICATE ALUMINOSILICATE CATALYSTS

The effective diffusivities of glucose and its linear analog glucitol were measured by a liquid chromatographic technique at 30 degrees C wi thin water-filled silica and aluminosilicate catalysts of mean pore si ze ranging from 7.4 to 116 Angstrom. For glucose, the effective diffus ivity decreased from 1.08 x 10(-6) to 1.77 x 10(-9) cm(2)/s as the mea n pore size decreased from 116 to 7.4 Angstrom. All values were signif icantly lower than the molecular diffusivity of 7.02 x 10(-6) cm(2)/s. The effective diffusivities for glucitol were three times lower than those for glucose over the same pore size range due to differences in solute size, structure, and solute-adsorbent interactions. The 8.6 Ang strom glucose molecule-was able to diffuse into the 7.4 Angstrom Y-zeo lite pore, possibly as its acyclic form. However, the 9.7 Angstrom glu citol molecule could not diffuse into the Y-zeolite pore. The reduced diffusivity was correlated to the reduced pore diameter using the Tern an model.