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Electrochemical catalysis emerges as a promising method for lignin depolymerization due to its environmental friendliness and mild reaction condition. Metal oxyhydroxides have displayed appealing electrochemical activity for the oxidation for various biomass substrates. In this study, we prepared different metal (Ni, Co, Mn, Fe, and Cu) oxyhydroxides on nickel foam electrodes through electrodeposition. Their electrochemical properties were characterized and the reactivity towards lignin oxidative cleavage was investigated using lignin model compounds. NiOOH exhibited significantly higher activity for oxidative cleavage of the β-O-4 linkage compared to other metal oxyhydroxides, resulting in a 93% yield of aromatic monomers with 99% selectivity towards benzoic acids. Furthermore, the reconstruction process of the active site NiOOH was revealed by in-situ testing, and the reaction mechanism was explored. The non-phenolic structure underwent Cβ–Cγ/Cβ–O or Cα–Cβ cleavage, predominantly producing benzoic acids, while the phenolic structure was rapidly oxidized into dicarboxylic acids over NiOOH. [ABSTRACT FROM AUTHOR]

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°C 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. [ABSTRACT FROM AUTHOR]

Wood shortages, environmental pollution and high energy consumption remain major obstacles hindering the development of today's pulp and paper industry. Energy-saving and environmental friendly pulping processes are still needed, especially for non-woody materials. In this study, soda-oxygen pulping of bagasse was investigated and a successful soda-oxygen pulping process for bagasse at 100 °C was established. The pulping parameters of choice were under active alkali charge of 23%, maximum cooking temperature 100 °C, time hold at maximum temperature 180 min, initial pressure of oxygen 0.6 MPa, MgSO4 charge 0.5%, and de-pithed bagasse consistency 12%. Properties of the resultant pulp were screened yield 60.9%, Kappa number 14, viscosity 766 dm³/kg, and brightness 63.7% ISO. Similar pulps were also obtained at 110 °C or 105 °C with a cooking time of 90 min. Compared with pulps obtained at higher temperatures (115-125 °C), this pulp had higher screened yield, brightness, and acceptable viscosity, while the delignification degree was moderate. These results indicated that soda-oxygen pulping at 100 °C, the lowest cooking temperature reported so far for soda-oxygen pulping, is a suitable process for making chemical pulp from bagasse. Pulping at lower temperature and using oxygen make it an environmental friendly and energy-saving pulping process. [ABSTRACT FROM AUTHOR]

One of the most promising technologies for lignocellulosic biomass utilization employs ionic liquids for the conversion of isolated components into fuels, pharmaceuticals, chemicals, and composites after fractionation of lignocellulose. However, the time required for dissolution of the whole cell wall has been excessive. To explore a possible dissolution and fractionation pathway of lignocelluloses, the dissolution of holocellulose isolated from bagasse was investigated in 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) assisted with ball-milling pretreatment and ultrasound irradiation. Ball milling pretreatment, ultrasonic irradiation assistance, and their combination were found to effectively improve the holocellulose dissolution in [C4mim]Cl. The effects of ultrasound power and irradiation duration on the dissolution time of ball-milled holocelluloses in [C4mim]Cl were studied. The regenerated holocelluloses were characterized with FT4-IR, X-Ray, and CP/MAS 13CNMR. It was found that there were no obvious changes of chemical structure after dissolution and regeneration of the holocellulose. The crystalline structure of cellulose was converted from cellulose I in native holocellulose to cellulose II in the regenerated holocellulose. The crystallinity decreased after the process of dissolution and regeneration assisted by ball-milling pretreatment and ultrasound irradiation. [ABSTRACT FROM AUTHOR]