Density functional theory and experimental study of cellulose initial degradation stage under inert and oxidative atmosphere

In-situ DRIFTS insights into the evolution of surface functionality of biochar upon thermal air oxidation

Biochar surface functionality is crucial for its application. Herein, the evolution of biochar surface functionality upon thermal air oxidation (TAO) was investigated in-situ by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and thermogravimetric analysis (TGA). The results show that, although the surface functionality of biochar is remarkably changed during TAO at the initial low temperature range, the biochar weight is still stable in the initial low temperature range, suggesting the chemisorption of O2 as intermediate oxygenated functional groups (OFGs) on biochar surface. Moreover, the evolution of biochar surface functionality upon TAO is highly affected on its preparation temperature and intrinsic minerals. Specifically, biochar produced at a high temperature is more resistant to TAO, and more favorable for the formation of ketone groups during TAO. While the biochars prepared at low or medium temperatures show a remarkable formation of carboxyl/lactone groups upon TAO, and the maximum temperature for the formation of carboxyl/lactone groups can be achieved at 400 °C. It's worth noting that the intrinsic minerals in biochar catalyze the TAO reaction, resulting in a much higher mass loss of biochar upon TAO. Furthermore, with the catalysis of intrinsic minerals, TAO is more suitable for enhancing the performance of biochar with intrinsic minerals. These results facilitate the design of engineered biochar via TAO for enhanced applications.

On-Line Thermally Induced Evolved Gas Analysis: An Update-Part 2: EGA-FTIR

The on-line thermally induced evolved gas analysis (OLTI-EGA) is widely applied in many different fields. Aimed to update the applications, our group has systematically collected and published examples of EGA characterizations. Following the recently published review on EGA-MS applications, this second part reviews the latest applications of Evolved Gas Analysis performed by on-line coupling heating devices to infrared spectrometers (EGA-FTIR). The selected 2019, 2020, 2021 and early 2022 references are collected and briefly described in this review; these are useful to help researchers to easily find applications that are sometimes difficult to locate.

Pyrolysis Mechanism of Wheat Straw Based on ReaxFF Molecular Dynamics Simulations

Biomass has played an increasingly important role in the consumption of energy worldwide because of its renewability and carbon-neutral property. In this work, the pyrolysis mechanism of wheat straw is explored using reactive force field molecular dynamics simulations. A large-scale wheat straw model composed of cellulose, hemicellulose, and lignin is built. After model validation, the temporal evolutions of the main pyrolysis products under different temperatures are analyzed. As the temperature rises, the gas production increases and the tar yield can decrease after peaking. Relatively high temperatures accelerate the generation rates of the main gas and tar species. CO and CO₂ molecules mainly come from the cleavage of CHO₂ radicals, and numerous H₂O molecules are generated on account of dehydration. Moreover, the evolution of six functional groups and pyran and phenyl rings as well as three types of bonds is also presented. It is observed that the phenyl rings reflect improved thermostability. Finally, the pyrolytic kinetics analysis is conducted, and the estimated activation energy of wheat straw pyrolysis is found to be 56.19 kJ/mol. All these observations can help deeply understand the pyrolytic mechanism of wheat straw biomass.