Cation-Exchange Resins
In the earliest studies on cellulose hydrolysis with acidic resins, Hartler et al. [82] found that little hydrolysis occurred at glycosidic bonds but the resins themselves underwent degradation. In a more recent work, improved and more stable ion-exchange resins were used in hydrolysis. Later Onda and coworkers tested a cation — exchange resin material (Amberlyst 15) with H-form zeolite materials, as H-P (12) (Si/Al= 12), H-P (75) (Si/Al= 75), H-mordenite (10) (Si/Al= 10), and HZSM5(45) (Si/Al= 45), sulfonated zirconia (JRC-SZ-1), and y-alumina (JRC-ALO-2) sulfonated activated-carbon (AC-SO3H). In this experiment sulfonated activated carbon produced the highest water soluble products and glucose yields. Amberlyst 15 ion exchange resin produced only a moderate 25% glucose yield [72]. However, the sulfated zirconia and Amberlyst 15 catalysts showed higher activity than the H-form zeolite catalysts. Furthermore, Onda and coworkers observed that there were large amounts of SO42- ions and byproducts in the resultant solution. The sulfonated activated-carbon catalyst showed high activity and remarkably high selectivity for glucose production from cellulose.