Synthesis of Propyl-Sulfonic Acid-Functionalized Nanoparticles as Catalysts for Cellobiose Hydrolysis

Abstract

Functionalization of silica surfaces using organo-silanes is highly sensitive to reaction conditions. Silica-coated nanoparticles were functionalized with propyl-sulfonic acid groups (PS) under different synthesis conditions including, various solvents (Ethanol, methanol, acetonitrile, and toluene), water content in the reaction media (0% to 50%), 3-mercaptopropyl-trimethoxysilane concentration (MPTMS) (0.5% to 10%), and reaction time (6 to 16 h). Size of the PS-nanoparticles was determined by TEM and varied from 3.5 to 20.3 nm with sulfur load. Elemental analysis revealed sulfur contents from 0.8% to 22%. FTIR analysis showed increased C-H band intensities with increasing sulfur content of PS-nanoparticles. Although PS-nanoparticles with sulfur loads under 3% did not improve the hydrolysis of cellobiose, PS acid-functionalized nanoparticles with about 6% S achieved 96.0% cellobiose conversion. The control experiment, without catalyst, converted 32.8% of the initial cellobiose. PS-nanoparticles with (6%-8% S) were obtained using (0.5%) silane concentration and 15-16 h reaction time in ethanol.

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“…However, the disadvantage of the dispersion from some nanoparticles is the difficulty to disperse in the aqueous solution where the hydronium ions were ineffective in the solution due to the wettability of the sample. The results showed that the acid-functionalized MNPs with 6% of sulfur content achieved cellobiose conversion up to 96.0% more than the conventional conversion (32.8%) without catalyst [25]. The presence of these acid-functionalized MNPs could enhance the hydrolysis reaction by their nanobiocatalyst properties for the immobilization of different enzymes.…”

“…A study has shown the capabilities of nanotechnology where acid-functionalized magnetic nanoparticles (MNPs) are used as catalysts to hydrolyze the cellobiose (β-glucose) from lignocellulose biomass [25]. However, the disadvantage of the dispersion from some nanoparticles is the difficulty to disperse in the aqueous solution where the hydronium ions were ineffective in the solution due to the wettability of the sample.…”

“…The presence of the silica-coated on the MNPs accelerates the mass transport in the acidic reaction due to its relatively porous structure and higher stability of the magnetic core. On the other hand, propyl-sulfonic acid-functionalized MNPs were subject to pretreatment and hydrolysis of wheat straw lignocellulose biomass, however the efficiency was not as promising compared to the above studies [25]. Recent technologies using microwaves-, ultrasonication-and electricity-assisted approaches are also recommended to be explored in the field of nanotechnology.…”

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“…Mbaraka et al demonstrated sulfonic acid immobilization in HMS and SBA-15 by oxidation of a pre-anchored thiol functionality [3]. As illustrated in Figure 2, [4] the accessibility of the SH is critical to obtaining a uniform distribution of acid catalytic sites and further improve reaction kinetics. Recently, the Fukuoka group fabricated a Ru/CMK-3 catalyst by a conventional impregnation method using Ruthenium salts.…”

“…Schematic representation of the Sulfonic Acid Synthesis for any silica-supported thiol (Adapted from ref [4]…”