Li Xinao,Xu Yuanyuan,Wu Jianning,Liu Zhiyong,Meng Guihua,Yang Shengchao,Guo Xuhong
Pretreatment of cellulosic materials with a Lewis acid is used to remove hemicelluloses and lower the reaction temperature of pretreatment systems. Adding Lewis acid in the pretreatment process of lignin extraction can form competitive hydrogen bonds to improve the pretreatment efficiency and the extraction rate of lignin. In this experiment, a Lewis acid (AlCl 3 ) was introduced to promote the separation of lignin by using the choline chloride/formic acid DES system. The dissolution rate of lignin was studied, as well as the effects of the molar ratio of Lewis acid/choline chloride/formic acid, reaction temperature, and reaction time on lignin structure, extraction rate, and solid residue recovery ratio. The experimental results showed that the optimal ratio of formic acid:choline chloride:AlCl 3 was 1:1:0.05. When the reaction temperature was 100 °C and the reaction time was 6 h, the solid residue recovery ratio was 33%, the extraction rate of lignin was 95.6%, and the purity was 95.0%. 2D HSQC NMR, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy were used to confirm the effect of Lewis acid on the extraction efficiency and structure of lignocellulose. The extracted lignin and commercial lignin showed similar structures, and the main structural units were G units and S units. In short, the addition of a Lewis acid improved the separation of lignin.
The detection of hydrazine (N 2 H 4 ), a highly toxic and explosive compound, is of paramount importance for ensuring environmental and industrial safety. However, research on chemoresistive gas sensors for N 2 H 4 detection, particularly the underlying mechanisms, remains limited. To address this gap, we have prepared carbon materials with a unique morphology and trace K doping through a simple carbonization process, utilizing raw cotton straw (RCS) as the starting material. The CS-400 sensor obtained under calcination at 400 °C exhibited high sensitivity and selectivity for N 2 H 4 , with a response of 30.6 k% and a detection limit of 0.55 ppm for 500 ppm N 2 H 4 at room temperature. Subsequently, the gas sensing mechanism of the straw-based biochar material was focused on, and the roles of cellulose, hemicellulose and lignin in the RCS were analyzed. The interaction between defects and carrier concentration during pyrolysis was elucidated. First-principles calculations confirmed that trace K doping and surface adsorbed oxygen enhance the adsorption of target gases, thereby improving the sensor performance.
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