Impacts of the hydroxyls crosslinking on lignin softening and pyrolysis via in situ 1H NMR, rheology, DRIFT and SPI-MS

The softening and foaming of lignin during pyrolysis are the main obstacles to scale-up systems. In this study, mechanism borate crosslinking on process was investigated by combining in-situ physical chemical techniques. First, mobile protons visco-elastic modulus were quantitatively analyzed high temperature 1H NMR rheology. It found that maximum content raw is around 90%. Hydroxyl greatly inhibits formation protons. produces a soft material from about 150 °C starts form more rigid 200 °C. At 210 ~ 330 °C, liquid-like intermediates entrapped in char, forming “cavities”. With addition boron, viscoelasticity tends be stable mainly elastic. Then, diffuse reflectance infrared Fourier transform spectroscopy single photoionization time-of-flight mass spectrometry used characterize evolution functional groups volatiles. shielding hydroxyl decomposition but improves selectivity phenols, oxygenated remain char.