Does toxicity of aromatic pollutants increase under remote atmospheric conditions

Aromatic compounds contribute significantly to the budget of atmospheric pollutants and represent considerable hazard to living organisms. However, they are only rarely included into atmospheric models which deviate substantially from field measurements. A powerful experimental-simulation tool for the assessment of the impact of low- and semi-volatile aromatic pollutants on the environment due to their atmospheric aqueous phase aging has been developed and introduced for the first time. The case study herein reveals that remote biotopes might be the most damaged by wet urban guaiacol-containing biomass burning aerosols. It is shown that only after the primary pollutant guaiacol has been consumed, its probably most toxic nitroaromatic product is largely formed. Revising the recent understanding of atmospheric aqueous phase chemistry, which is mostly concerned with the radical nitration mechanisms, the observed phenomenon is mainly attributed to the electrophilic nitrogen-containing reactive species. Here, their intriguing role is closely inspected and discussed from the ecological perspective

Effect of Textural Properties and Presence of Co-Cation on NH3-SCR Activity of Cu-Exchanged ZSM-5

Comparative studies over micro-/mesoporous Cu-containing zeolites ZSM-5 prepared by top-down treatment involving NaOH, TPAOH or mixture of NaOH/TPAOH (tetrapropylammonium hydroxide) were conducted. The results of the catalytic data revealed the highest activity of the Cu-ZSM-5 catalyst both in the absence and presence of water vapor. The physico-chemical characterization (diffuse reflectance UV-Vis (DR UV-Vis), Fourier transform infrared (FT-IR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, temperature-programmed desorption of NOx (TPD-NOx), and microkinetic modeling) results indicated that the microporous structure of ZSM-5 effectively stabilized isolated Cu ion monomers. Besides the attempts targeted to the modification of the textural properties of the parent ZSM-5, in the next approach, we studied the effect of the co-presence of sodium and copper cations in the microporous H-ZSM-5. The presence of co-cation promoted the evolution of [Cu–O–Cu]2+ dimers that bind NOx strongly with the desorption energy barrier of least 80 kJ mol−1. Water presence in the gas phase significantly decreases the rate of ammonia oxidation, while the reaction rates and activation energies of NH3-SCR remain unaffected

Biorefining Twin Transition: Digitalisation for Bio-based Chemicals/Materials - Discovery, Design and Optimisation

The article discusses the production of platform chemicals from various biological sources, including glycerol, lignin, cellulose, bio-oils, and sea products. It presents the results of catalytic and downstream processes involved in the conversion of these biomass-derived feedstocks. The experimental approaches are complemented by numerical descriptions, ranging from density functional theory (DFT) calculations to kinetic modellingof the experimental data. This multi-scale modelling approach helps to understand the underlying mechanisms and optimize the production of platform chemicals from renewable resources

Catalytic cracking of biomass-derived hydrocarbon tars or model compounds to form biobased benzene, toluene, and xylene isomer mixtures

The gasification of biomass is one of the most prominent technologies for the conversion of the raw material feedstock to polymers, useful chemical substances, and energy. The main engineering challenge during the processing of wastes is the presence of tars in gaseous reaction products, which could make this operation methodology unsuccessfully due to the blockage of separating particle filters, fuel line flow, and substantial transfer losses. Catalytic hydrocarbon cracking appears to be a promising developing approach for their optimal removal. However, it is still highly desirable to enhance the catalysts’ activity kinetics, selectivity, stability, resistance to (ir)­reversible coke deposition, and regeneration solutions. The purpose of this Review is to provide a comparative systematic evaluation of the various natural, synthetic, and hybrid ways to convert the model molecular compounds into benzene, toluene, xylene, (poly)­aromatics, syngas, and others. The recent scientific progress, including calcite, dolomite, lime, magnesite, olivine, char, nonmetallic activated carbons, supported alkali, noble, and transition metals, and (metal-promoted) zeolites, is presented. A special concentrated attention is paid to effectiveness, related to hydrogenation, peculiar pore structure, and formulations’ suitable acidity. The role of catalysis is described, recommendations for prospective catalyzed mechanisms are provided, and future technical feasibility is discussed as well

Mechanistic reaction micro-kinetics-based structure–activity relationships for palmitic acid hydrodeoxygenation over ▫NiMoSx/Al2O3NiMoS_x/Al_2O_3▫ catalysts

The kinetics of palmitic acid hydro-deoxygenation over sulfided NiMo/γ-Al$_2$O$_3$ have been described, including the gas–liquid–solid mass transport/surface chemistry in a magnetically-stirred batch reactor via temperature (225–275 °C), hydrogen pressure (30–70 bar) and catalyst loading (0.1–0.4 g) variation. Intermediates, the hexadecanol and palmityl palmitate, have been probed for a deeper physical understanding of mechanisms. Rates were used to show the impact of the continuum H$_2$ thermodynamic phenomena, availability and coverages on the selectivity among the direct hydrogenation, hydrogenolysis and decarbonylation reactions through the role of H$^•$ formation dependent and independent changes. The system was reduced to 11 catalytic transformation steps, including 8 different molecular species, present in medium. Sequence is simulated to happen on the calculated functional number of active site structures, the activity of which was averaged, while the activation of H$_2$ was supposed to initiate independently. The results of model integrate parameters, such as energies, constants and performance. Process was highly temperature-related, while H$_2$ presence expressed linearly. Phases were characterized with temperature-programmed desorption analysis, coupled with mass spectrometry (TPD–MS) technique, transmission- (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD)