Homogeneously Synchronous Degradation of Chitin into Carbon Dots and Organic Acids in Aqueous Solution

Abstract

Biomass polysaccharides are natural biopolymers and are considered as energy storage structural materials and suppliers in animals and plants. Among various biomass polysaccharides, chitin is the second most important biomass resource, which can be regarded as an alternative raw material for fine chemicals, especially in its homogeneous solution. Herein, a homogeneous aqueous solution of potassium hydroxide/urea was used as the solvent to dissolve chitin at first under a low-temperature pretreatment, which was then degraded by a hydrothermal process. Both small molecular organic acids and carbon dots (CDs) can be formed simultaneously. The maximum yield of organic compounds (oxalic acid, malonic acid, formic acid, lactic acid, acetic acid, and pyrrole) is 68.45%, while the main product is acetic acid with yield of 31.02%. Synchronously, up to 6% CDs can be obtained, which showed excellent fluorescent properties and promising applications in the detection of iron ions. This work provides an overview of the homogeneous conversion of chitin into an aqueous solution, from which both CDs and organic compounds can be obtained in a simple and green method.

Progress in Catalytic Conversion of Renewable Chitin Biomass to Furan-Derived Platform Compounds

“…Under optimized conditions, the combination of H-β zeolite and dilute acetic acid aqueous solution gave the highest HMF yield of 15 mol% to 28 mol% depending on the molecular weight of the parent chitosan. Acetic acid as a "green" organic acid can be produced from biomass-based feedstock [38,39]. Unfortunately, the obvious activity loss of recovered H-β zeolite was observed, and only half the HMF yield compared to fresh H-β zeolite was obtained.…”

Base-Free, Vanadium-Catalyzed Conversion of Chitin into Acetic Acid under Low Oxygen Pressure

“…Later on, a noncatalytic process was established by Su et al in which the chitin was first dissolved in a KOH/urea solvent system (3.5 M KOH) under a lowtemperature pretreatment and then transformed by a hydrothermal process at 200−320 °C. 69 The highest AA yield of 31.0% was obtained at beyond 240 °C with a reaction time of 12 h. These works showcased the superiority of chitin as a feedstock for efficient renewable AA production. However, the approaches employed extremely concentrated basic solutions under a high temperature.…”

“…The facile cleavage of the acetamido side chain would directly lead to a theoretical 25% yield of AA, which was ascribed as one major reason for the much-boosted AA yield from chitin compared to that from cellulose. Later on, a noncatalytic process was established by Su et al in which the chitin was first dissolved in a KOH/urea solvent system (3.5 M KOH) under a low-temperature pretreatment and then transformed by a hydrothermal process at 200–320 °C . The highest AA yield of 31.0% was obtained at beyond 240 °C with a reaction time of 12 h.…”

Biomass‐derived Carbon Quantum Dots – A Review. Part 1: Preparation and Characterization

“…The role of different reaction temperatures (200, 220, 240, 280, and 320 °C) for an exposure of 12 h was studied. At higher reaction temperature (320 °C), the quantum yield and productivity increased due to rapid degradation and carbonization of chitin 251.…”