Eco-friendly Method for Efficient Conversion of Cellulose into Levulinic Acid in Pure Water with Cellulase-Mimetic Solid Acid Catalyst

Abstract

Microcrystalline cellulose could be effectively converted into levulinic acid in pure water at 180 °C in 12 h without additives in a maximum yield of 51.5% with a cellulase-mimetic solid acid catalyst prepared without the use of sulfuric acid. Ball-milling pretreatment of cellulose improved levulinic acid yields by only a few percent, showing that the cellulose binding sites (−Cl) and catalytic sites (−SO3H) of the catalyst are key to the activity of the catalyst. The spent catalyst could be regenerated with H2O2 solution after recycling for 5 times to maintain more than 95% of its catalytic activity. Glucose used as starting material under the same reaction conditions and with the same cellulase-mimetic solid acid gave a yield of 61.5% levulinic acid. The conversion route for carbohydrates to levulinic acid in pure water with the biomimetic catalyst prepared with a H2SO4-free method provides an environmentally friendly method for producing biobased-platform chemicals from renewable resources.

Catalytic Transformation of Cellulose and Its Derivatives into Functionalized Organic Acids

“…Various solid acids, such as Amberlyst, zeolites, acidic TiO 2 , niobium phosphate, polymers containing SO 3 H groups, and polyoxometalates, have received increasing attention for the conversion of cellulose into levulinic acid because of their easy recovery and repeated uses. Because of the strong acidity of SO 3 H, solid acids containing SO 3 H groups are highly active in the conversion of cellulose.…”

“…The presence of high densities of −SO 3 H groups and −Cl groups, which could function as bonding sites to cellulose, was demonstrated to contribute to the high performance. Recently, a silica/carbon mesoporous composite with −Cl and −SO 3 H groups (SA‐SO 3 H) was synthesized for the catalytic transformation of cellulose into levulinic acid in water . Compared with the solid acid without −Cl groups, SA‐SO 3 H, which contained −Cl groups, displayed a higher levulinic acid yield (46 versus 11 %) after reaction at 453 K for 15 h. If a silica/carbon mesoporous solid with −Cl groups, but without −SO 3 H groups, was used for the conversion of cellulose, negligible products were obtained.…”

“…The SA‐SO 3 H catalyst can be recovered for recycling; however, the yield of levulinic acid decreases from 41 to 30 % after five repeated uses . ICP‐OES analysis of the reaction solution showed negligible amounts of Cl and S, which suggested that the leaching of active species was not the main reason for catalyst deactivation.…”

Versatile design and synthesis of mesoporous sulfonic acid catalysts

“…Further regeneration of used CP-SO 3 H was performed with activation of 28.5 wt% H 2 O 2 at 35°C overnight with high efficiency, and the recovered catalysts restored the original catalytic activity. This strategy can also be utilized in other mesoporous supports, and Qi's group [94] used an evaporation-induced tri-constituent coassembly method to obtain mesoporous cellulase-mimetic carbon/silica hybrid catalyst: (3-mercaptopropyl)-trimethoxysilane as the -SO 3 H precursor, sucralose as the -Cl precursor and tetraethyl orthosilicate as the cross-linker. With inorganic robust frameworks, negligible Cl and S losses occurred during conversion of cellulose into levulinic acid in pure water.…”

Dual‐Functional Templated Methodology for the Synthesis of Hierarchical Porous Carbon for Supercapacitor

“…Porous carbon materials, which can be synthesized from a variety of biomass resources, have been widely used in many fields such as adsorption, catalysis, drug delivery, sensors, and especially energy storage devices . For example, porous carbons are the most common and promising electrode materials for supercapacitors which is a new kind of energy storage devices .…”