Abstract
Sulfonic organosilica nanotubes with different acidity densities could be synthesized through the co-condensation of ethenyl- or phenylene-bridged organosilane and 3-mercaptopropyltrimethoxysilane followed by sulfhydryl (–SH) oxidation. Transmission electron microscopy (TEM) analysis and nitrogen adsorption-desorption experiment clearly exhibit the hollow nanotube structures with the diameters of about 5 nm. The compositions of the nanotube frameworks are confirmed by solid state 13C nuclear magnetic resonance (NMR) while X-ray photoelectron spectroscopy (XPS) shows that about 60–80% of SH groups were oxidized to sulfonic acid (SO3H). The acid contents were measured by both elemental analysis (CHNS mode) and acid-base titration experiment, which revealed that the acid density was in the range of 0.74 to 4.37 μmol·m−2 on the solid. These nanotube-based acid catalysts exhibited excellent performances in the hydrolysis of cellobiose with the highest conversion of 92% and glucose selectivity of 96%. In addition, the catalysts could maintain high activity (65% conversion with 92% selectivity) even after six recycles.
Highlights
The preparation of fuels and chemical products derived from biomass is one of the most attractive approaches of the sustainable development for our society [1]
Considerable efforts have been dedicated to the design and synthesis of effective solid acid catalysts as alternatives
Results and Sulfhydryl-functionalized organosilica organosilica nanotubes or or phenylene groups in the Sulfhydryl-functionalized nanotubeswith withethenyl ethenyl phenylene groups in the frameworks were synthesized through the co-condensation of ethenylor phenylene-bridged frameworks were synthesized through the co-condensation of ethenyl- or phenylene-bridged organosilane and 3-mercaptopropyltrimethoxysilane (MPTMS) using self-assembly methods, which organosilane and 3-mercaptopropyltrimethoxysilane (MPTMS) using self-assembly methods, which were denoted as SHX-Et-SNT or SHX-Ph-SNT (x means the ratio of MPTMS amounts in the total were denoted as SHx -Et-SNT or SHx -Ph-SNT (x means the ratio of MPTMS amounts in the total precursors), respectively
Summary
The preparation of fuels and chemical products derived from biomass is one of the most attractive approaches of the sustainable development for our society [1]. Most widely existing in nature as one of the renewable biomass resources, has drawn much attention regarding its efficient utilization [2]. Among the strategies for cellulose utilization, hydrolysis reaction is one of the most important steps. Due to the strong intermolecular and intramolecular hydrogen bonds, traditional acid catalysts including concentrate and diluted sulfuric acids are usually used to realize the cleavage of cellulose [3]. Such liquid acids are difficult to recycle and reuse, which may cause serious environmental pollution and high production costs [4]. Considerable efforts have been dedicated to the design and synthesis of effective solid acid catalysts as alternatives
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