ACS Sustainable Chemistry & Engineering最新文献

Background and objective

Methods

Key findings and limitations

Conclusions and clinical implications

Sustainable biochar can sequester carbon and therefore, mitigate climate change. However, only a small fraction of biomass carbon is retained during biochar synthesis, greatly restricting its carbon-sequestration capacity. A significant boost of the carbon-sequestration potential of biochar has so far been a challenge. This study reveals that when biochar is modified by FeCl₃, its carbon-sequestration capacity is boosted to 247.73% of that of pristine biochar derived at 500 °C. Meanwhile, pristine biochar retains only 43.18% of its biomass carbon, while FeCl₃-modified biochar retains 75.20% of its carbon by forming complexes between the iron salts and the carboxyl- and hydroxyl-rich organic compounds derived from biomass pyrolysis. As react proceeds, the complexes are further converted into ferrites and organic carbon. The resulting minerals provide physical barriers against carbon decomposition, further enhancing the long-term stability of biochar. Life cycle assessment results further show that ferric salt can markedly enhance the greenhouse gas─reduction potential of biomass-to-biochar-to-soil systems. The more cycles from biomass to upgraded biochar, the more potent the carbon-negative effect is. Undoubtedly, such discoveries hold significant implications for accelerating carbon neutrality.

Upcycling spent polyesters into useful chemicals is of great significance for achieving a circular carbon economy. Herein, we report the valorization of polycaprolactone (PCL) to γ-caprolactone over binary ionic liquid systems derived from 1-butyl-3-methylimidazolium bromide ([BMIm]Br) and CuBr₂ under mild conditions (e.g., 160 °C). It was found that the in situ formed Lewis acidic [CuBr₄]^2– anion could activate the ester group of PCL via coordination with carbonyl O, while [Br]⁻ anion could attack the C atom of alkyl C–O to achieve the decomposition of PCL, forming the key ionic intermediate, 6-bromohexanoate. This intermediate subsequently undergoes β-elimination reaction and isomerization–lactonization transformation facilitated by the synergistic effect of cation and anion of the ionic liquids, thus producing γ-caprolactone in high yield and selectivity. This simple, green, and efficient protocol to valorize PCL into γ-caprolactone holds great promise for application in industry.

Dehydration of sorbitol catalyzed by inorganic acids has been regarded as an efficient way to produce isosorbide, which shows application in the manufacture of various high value-added compounds. However, these catalysts can cause equipment corrosion and are not recyclable. As a cheap and environmentally friendly catalyst with special tunability and stability, a deep eutectic solvent (DES) composed of p-toluenesulfonic acid (p-TSA) and choline chloride (ChCl) has emerged to meet the demand for “green production” of isosorbide. The conditions for the dehydration of sorbitol catalyzed by DESs were systematically investigated. The differences in catalytic efficiency stemming from the structural diversity of DESs were explored by FT-IR characterization and molecular dynamics simulation. The results showed that isosorbide exhibited notable selectivity (88%) within the DESs (p-TSA:ChCl = 1.2), and achieved a high extraction rate (83%) under the synergistic effect of ethyl acetate and acetone (4:1). MD simulations indicated that hydrogen bonding was the dominant factor influencing the catalytic activity. The theoretical understanding of the p-TSA/ChCl structure may provide a reference for the tunability of novel DESs to meet the requirements of catalysis, absorption, and extraction.