Quantitative Extraction of p-Coumaric Acid and Ferulic Acid in Different Gramineous Materials and Structural Changes of Residual Alkali Lignin

Ferulic acid(FA)and p-coumaric acid(pCA)in bagasse,wheat straw,corn straw,and corncob were extracted by alkaline hydrolysis and characterized by gas chromatography(GC)and gas chromatography-mass spectrometry(GC-MS).It was found that the FA and most of the pCA in gramineous biomass could be dissociated and released after being treated with 1 M NaOH at 100℃for 4 h.The yields of pCA/FA in bagasse,wheat straw,corn straw,and corncob determined by GC-FID are 39.8/11.5,13.7/11.0,28.0/11.0,and 35.1/14.5 mg/g,respectively.The raw materials and the treated solid residues were characterized by gel-state 2D Heteronuclear Single Quantum Coherence Nuclear Magnetic Resonance(2D HSQC NMR).It was found that only a small amount of lignin was detected in the residue after alkali treatment,indicating that the alkali treatment conditions can effectively cleave the FA and pCA.Additionally,the lignin in the alkali solution was recovered and characterized by 2D HSQC NMR.The FA was not able to be detected by NMR,whereas a small amount of pCA remained in the alkali lignin.This study reveals the structural change of residual lignins during the quantitative isolation of FA and pCA,which is essential for the selective isolation of pCA/FA and valorization of residual alkali lignin.

Synthesis of Amphiphilic Starch Derivatives Using One-pot Synthesis Procedure

Amphiphilic starch derivatives with high content of functional groups were prepared from potato starch using a one-pot synthesis method with a single reaction medium for the entire procedure. Potato starch was benzylated, followed by the introduction of hydroxypropyltrimethylammonium(HPMA) moieties without the purification of intermediates. The synthesis was performed under heterogeneous conditions, leading to the formation of benzyl 2-hydroxypropyltri methylammonium starch chloride(BnHPMAS) with a total degree of substitution(DS) of up to 1.4. This process improved the efficiency of the preparation of amphiphilic starch derivatives and reduced the time and resources consumed by avoiding a separation process and purification of the intermediate compounds.The DS of BnHPMAS was in the range of 0.36 to 1.4, which could be tuned by varying the molar ratio of the reagents to repeating unit or by changing the reaction temperature, time, and medium. The structure of the amphiphilic starches was characterized using elemental analysis, size exclusion chromatography,fourier transform infrared spectroscopy(FT-IR), and nuclear magnetic resonance(NMR) spectroscopy. Moreover, the surface tension and turbidity of the solutions of the products were measured for their potential application in the removal of dissolved and colloidal substances in paper cycling water.

Efficient oxidation of monosaccharides to sugar acids under neutral condition in flow reactors with gold-supported activated carbon catalysts

A significant reaction in the synthesis of biomass-based chemicals is the catalyst-based and targeted oxidation of monosaccharides into valuable sugar acids.In this study,an activated carbon supported gold catalyst was used to oxidize glucose and xylose to gluconic acid and xylonic acid under neutral condition.Optimization of reaction conditions for the catalysts was performed using both a batch reactor and a flow-through reactor.In a batch reactor,the yields of gluconic and xylonic acid reached 93%and 92%,respectively,at 90°C within 180 min.In a flow reactor,both reactions reached a similar yield at 80°C with the weight hourly space velocity of 47.1 h^(-1).The reaction kinetics were explored in the flow reactor.The oxidation of glucose and xylose to gluconic and xylonic acid followed a first-order kinetics and the turnover frequency was 0.195 and 0.161 s^(-1),respectively.The activation energy was evaluated to be 60.58 and 59.30 kJ·mol^(-1),respectively.This study presents an environmentally friendly and feasible method for the selective oxidation of monosaccharides using an activated carbon supported gold catalyst,benefiting the high-value application of carbohydrates.