XOS production from lignocellulose using organic carboxylic acids and alkyd acids has been widely reported. However, it still faces harsh challenges such as high energy consumption, high cost, and low purity. Pyruvic acid (PYA), a carbonyl acid with carbonyl and carboxyl groups, was used to produce XOS due to its stronger catalytic activity. In this work, XOS was efficiently prepared from COS in an autoclave under the condition of 0.21 M PYA-121 °C-35 min. The total yield of XOS reached 68.72 % without producing any toxic by-products, including furfural (FF) and 5-hydroxymethylfurfural (5-HMF). The yield of xylobiose (X 2 ), xylotriose (X 3 ), xylotetraose (X 4 ), and xylopentaose (X 5 ) were 20.58 %, 12.47 %, 15.74 %, and 10.05 %, respectively. Meanwhile, 89.05 % of lignin was retained in the solid residue, which provides a crucial functional group for synthesizing layered carbon materials (SRG-a). It achieves excellent electromagnetic shielding (EMS) performance through graphitization, reaching −30 dB at a thickness of 2.0 mm. The use of a PYA catalyst in the production of XOS has proven to be an efficient method due to lower temperature, lower acid consumption, and straightforward operation.
Peilan Luo,Menglin Ye,Wenli Zhou,Pingping Wan,Zhongyun Ma,Zhongxian Qiu,Jilin Zhang,Ru-Shi Liu,Shixun Lian
The traditional strategy to improve material stability is to cover the surface with a shell to resist adverse environmental factors. For the red-emitting fluoride materials with easily hydrolyzed Mn 4+ on the surface, many strategies have been reported with limited effectiveness. In this work, simultaneous construction of an impermeable dual-shell on Mn 4+ -doped fluoride is proposed to solve the instability problem by a simple pyruvic acid (PA) treatment. The internal quantum efficiency of the K 2 SiF 6 :Mn 4+ with dual-shell can be optimized up to 99.71%, the photoluminescence intensity can maintain 88.5% of the original intensity after soaking in water for 360 h, and the body color is not changed even in boiling. The reduction effect of the PA solution builds a hard fluoride shell by removal of the surface Mn 4+ , and the hydrogen bonding effect of PA molecular leads to the formation of a soft organic shell. The dual-shell can effectively block the damage of fluoride by external water molecules and achieve a significant improvement in water stability. The dual effect of PA is derived from its special molecular structure containing α -ketone carbonyl and carboxyl groups. This hypothesis is supported by the results of the moisture resistance of fluoride-treated with a variety of solvents similar in molecular structure to PA. In addition, DFT calculations simulated various hydrogen bond structures that may be formed between PA molecules and fluoride surface atoms.
α-Ketoglutaric acid (KGA) and methanetriacetic acid (MTA) are important multi-functional carboxylic acids with versatile applications. However, their synthetic processes are still not green and efficient. Herein, we report a novel one-pot approach for sustainable synthesis of KGA and MTA from biomass-derived pyruvic and glyoxylic acids under mild conditions. KGA is synthesized via cross-aldol condensation of pyruvic and glyoxylic acids to 2-hydroxy-4-oxopentanedioic acid, followed by its sequential dehydration and hydrogenation on Pd/TiO 2 , affording a high yield of 85.4% on a molar basis of glyoxylic acid at 110 °C and 1.0 MPa H 2 . The synthesis of MTA involves cross-aldol condensation of KGA and glyoxylic acid to 3-(carboxymethyl)-2-hydroxy-4-oxopentanedioic acid and its subsequent hydrodeoxygenation on Pd/TiO 2 and MoO x /TiO 2 in a high yield of 86.2% at 200 °C and 2.0 MPa H 2 . This novel approach provides a rationale for the sustainable production of various multi-functional carboxylic acids that are still not easily available.
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