Reactivity Enhancement of Lignin Extracted from Preconditioning Refiner Chemical-Recycle Bleached Mechanized Pulp (PRC-RBMP) Black Liquor by Phenolation

Despite black liquor’s (BL) renown as a difficult-to-manage contaminant in the pulp and paper industry, BL has been found as a viable alternative material for adhesive formulation due to its high lignin content. Nevertheless, modification is required to enhance lignin’s reactivity, and there is currently a lack of study focusing on this aspect for BL-lignin. This study aims to increase the phenolic hydroxyl content of BL-lignin by phenolation. After being phenolated at lignin to phenol ratio of 1:1, at a temperature of 100°C for 110 minutes, and with the addition of 8% sulfuric acid (H2SO4) as a catalyst, the phenolic hydroxyl content improved by 51.5%. The results of Fourier transform infrared spectroscopy (FTIR), UV/Vis spectrophotometry, proton nuclear magnetic resonance (1H-NMR), thermogravimetry-differential scanning calorimetry (TG-DSC), and its differential curve showed that the structural change in phenolated lignin opened up more active sites, implying that this lignin could be a good substitute for phenol in phenol-formaldehyde resin manufacturing.