| 摘要： |
The catalytic behavior of a series of MFI catalysts with different Si/Al ratio (25-300) in the direct aqueous-phase hydrolysis of alpha-cellulose was studied. The effects ultrasonic pretreatment time, ZnCl2 content, zeolite pore structure and acid-basic properties on catalyst activity and products distribution were systematically investigated. The results indicated that HZSM-5 with lower Si/AI ratio was beneficial for production of glucose and LA from alpha-cellulose. Ultrasonic pretreatment could decrease the degree of crystallinity and polymerization of alpha-cellulose, enhance the accessibility of acid sites and ZnCl2 to the loosened amorphous regions of alpha-cellulose in water, and improve the hydrolysis efficiency of alpha-cellulose. The desilicated ZSM-5 (HZSM-5-DS(0.2)) showed much higher catalytic activities as compared to commercial ZSM-5 and alpha-cellulose conversion reached 76.5% over HZSM-5-DS(0.2) at 200 degrees C. Catalytic conversion of alpha-cellulose consisted of at least three important parallel reactions under the present hydrothermal conditions and a plausible pathway was proposed. Effective control of these reactions would be helpful to further maximize the target product yield during the catalytic conversion of alpha-cellulose. (C) 2017 Elsevier B.V. All rights reserved. |
