Influence of Brønsted and Lewis acidity of the modified Al-MCM-41 solid acid on cellulose conversion and 5-hydroxylmethylfurfuran selectivity.

Affiliation

Pham ST(1), Nguyen MB(2), Le GH(3), Nguyen TD(4), Pham CD(5), Le TS(6), Vu TA(7).
Author information:
(1)Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay, Ha Noi City, Viet Nam; Hanoi University of Science
(HUS), Vietnam National University
(VNU), 334 Nguyen Trai, Hanoi, Viet Nam.
(2)Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay, Ha Noi City, Viet Nam; Hanoi University of Science and Technology
(HUST), 01 Dai Co Viet Road, Ha Noi City, Viet Nam. Electronic address: [Email]
(3)Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay, Ha Noi City, Viet Nam.
(4)Center of Excellence for Green Energy and Environmental Nanomaterials
(CE@ GrEEN), Nguyen Tat Thanh University, Ho Chi Minh City, Viet Nam. Electronic address: [Email]
(5)Hanoi University of Science and Technology
(HUST), 01 Dai Co Viet Road, Ha Noi City, Viet Nam.
(6)Hanoi University of Science
(HUS), Vietnam National University
(VNU), 334 Nguyen Trai, Hanoi, Viet Nam.
(7)Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay, Ha Noi City, Viet Nam; Graduate University of Science and Technology, Vietnam Academy of Science and Technology. 18 Hoang Quoc Viet Street, Cau Giay, Ha Noi City, Viet Nam. Electronic address: [Email]

Abstract

The modified Al-MCM-41 solid acids with turning Si/Al molar ratio were successfully fabricated through a hydrothermal route and utilized as a suitable catalyst in the cellulose conversion into 5-hydroxylmethylfurfural (5-HMF). The crystal structure, composition, morphologies and porosity of as-synthesized acids were characterized by XRD, FT-IR, N2 adsorption-desorption, TEM and EDS. The 27Al MAS NMR and 29Si-MAS NMR results revealed the existence of both Al framework and Al extra framework. Besides, the existence of medium-weak and strong acid sites, according to Brønsted and Lewis acidity, in Al-MCM-41 acids was confirmed by NH3-TPD and FTIR-pyridine adsorption. The 30Al-MCM-41 solid acid (Si/Al molar ratio = 30) exhibited excellent activity with the highest 5-HMF yield of 40.56% compared to other samples. We also discovered that 5-HMF production, as well as cellulose conversion, strongly depended on the total acid, strong/medium-weak acid ratio, as well as Brønsted/Lewis acid ratio. Therefore, these parameters have been considered as essential factors for the design of solid acid for 5-HMF production.