Radical−Molecule Reactions for Aromatic Growth: A Case Study for Cyclopentadienyl and Acenaphthylene

Diels–Alder reaction of tetraarylcyclopentadienones with benzo[b]thiophene S,S-dioxides: an unprecedented de-oxygenation vs. sulfur dioxide extrusion

The Diels–Alder adduct, dihydrodibenzothiophene S,S-dioxides underwent aromatization either through de-oxygenation or extrusion of sulfur dioxide to furnish substituted dibenzothiophenes or benzenes.

Pressurized entrained-flow pyrolysis of microalgae: Enhanced production of hydrogen and nitrogen-containing compounds

Pressurized entrained-flow pyrolysis of Chlorella vulgaris microalgae was investigated. The impact of pressure on the yield and composition of pyrolysis products were studied. The results showed that the concentration of H₂ in bio-gas increased sharply with increasing pyrolysis pressure, while those of CO, CO₂, CH₄, and C₂H₆ were dramatically decreased. The concentration of H₂ reached 88.01 vol% in bio-gas at 900 °C and 4 MPa. Higher pressures promoted the hydrogen transfer to bio-gas. The bio-oils derived from pressurized pyrolysis were rich in nitrogen-containing compounds and PAHs. The highest concentration of nitrogen-containing compounds in bio-oil was achieved at 800 °C and 1 MPa. Increasing pyrolysis pressure promoted the formation of nitrogen-containing compounds such as indole, quinoline, isoquinoline and phenanthridine. Higher pyrolysis pressures led to increased sphericity, enhanced swelling, and higher carbon order of bio-chars. Pressurized pyrolysis of biomass has a great potential for poly-generation of H₂, nitrogen containing compounds and bio-char.

Fates of Chemical Elements in Biomass during Its Pyrolysis

Biomass is increasingly perceived as a renewable resource rather than as an organic solid waste today, as it can be converted to various chemicals, biofuels, and solid biochar using modern processes. In the past few years, pyrolysis has attracted growing interest as a promising versatile platform to convert biomass into valuable resources. However, an efficient and selective conversion process is still difficult to be realized due to the complex nature of biomass, which usually makes the products complicated. Furthermore, various contaminants and inorganic elements (e.g., heavy metals, nitrogen, phosphorus, sulfur, and chlorine) embodied in biomass may be transferred into pyrolysis products or released into the environment, arousing environmental pollution concerns. Understanding their behaviors in biomass pyrolysis is essential to optimizing the pyrolysis process for efficient resource recovery and less environmental pollution. However, there is no comprehensive review so far about the fates of chemical elements in biomass during its pyrolysis. Here, we provide a critical review about the fates of main chemical elements (C, H, O, N, P, Cl, S, and metals) in biomass during its pyrolysis. We overview the research advances about the emission, transformation, and distribution of elements in biomass pyrolysis, discuss the present challenges for resource-oriented conversion and pollution abatement, highlight the importance and significance of understanding the fate of elements during pyrolysis, and outlook the future development directions for process control. The review provides useful information for developing sustainable biomass pyrolysis processes with an improved efficiency and selectivity as well as minimized environmental impacts, and encourages more research efforts from the scientific communities of chemistry, the environment, and energy.

The atmospheric oxidation mechanism and kinetics of 1,3,5-trimethylbenzene initiated by OH radicals – a theoretical study

The atmospheric fate of 1,3,5-trimethylbenzene is determined by OH-radical addition, and subsequent bicyclic peroxy radical ring closure and ring breaking pathways.

Polycyclic aromatic hydrocarbons (PAH) formation from the pyrolysis of different municipal solid waste fractions

The formation of 2-4 ring polycyclic aromatic hydrocarbons (PAH) from the pyrolysis of nine different municipal solid waste fractions (xylan, cellulose, lignin, pectin, starch, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET)) were investigated in a fixed bed furnace at 800 °C. The mass distribution of pyrolysis was also reported. The results showed that PS generated the most total PAH, followed by PVC, PET, and lignin. More PAH were detected from the pyrolysis of plastics than the pyrolysis of biomass. In the biomass group, lignin generated more PAH than others. Naphthalene was the most abundant PAH, and the amount of 1-methynaphthalene and 2-methynaphthalene was also notable. Phenanthrene and fluorene were the most abundant 3-ring PAH, while benzo[a]anthracene and chrysene were notable in the tar of PS, PVC, and PET. 2-ring PAH dominated all tar samples, and varied from 40 wt.% to 70 wt.%. For PS, PET and lignin, PAH may be generated directly from the aromatic structure of the feedstock.