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Chemicals from Olefin Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Much like the oxidation of propylene, which produces acrolein and acrylic acid, the direct oxidation of isobutylene produces methacrolein and methacrylic acid. The catalyzed oxidation reaction occurs in two steps due to the different oxidation characteristics of isobutylene (an olefin) and methacrolein (an unsaturated aldehyde). In the first step, isobutylene is oxidized to methacrolein [CH2=C(CH3)CHO] over a molybdenum oxide-based catalyst in a temperature range of 350°C–400°C (650°F–750°F). The process pressures are a little above atmospheric pressure (on the order of 15–25 psi). In the second step, methacrolein is oxidized to methacrylic acid at a relatively lower temperature range of 250°C–350°C (480°F–650°F). A molybdenumsupported compound with specific promoters catalyzes the oxidation.
Air pollution control and mitigation
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
One can argue that application of natural vegetation to control air pollution may not be effective as plants, particularly tree species, release substantial amounts of non-methane BVOCs including isoprene (C5H8), monoterpenes (C10H18), sesquiterpenes (C15H28) and oxygenated compounds (CnH2n–2O). These compounds can accentuate air pollution through production of secondary organic aerosols (SOAs). Results from recent laboratory studies suggest that acid-catalysed multiphase reactions of isoprene produce oligomeric humic-like material resulting in substantial aerosol formation. Recent research also suggests possible enhancement in the generation of aerosols from isoprene and its oxidation derivatives (e.g. methacrolein and methyl vinyl ketone) via condensed phase reactions with hydrogen peroxide. In addition, some of the BVOCs (e.g. isoprene), because of their alkene chemical structure, play important roles in suppressing concentrations of the hydroxy (OH) radical, enhancing the production of peroxy (HO2 and RO2) radicals, enhancing tropospheric CO concentrations, generating organic nitrates that can sequester NOx and allowing long-range transport of reactive N. The latter plays a vital role in atmospheric chemistry as it leads to photochemical production of tropospheric ozone.
Mitigation of air pollution
Published in Abhishek Tiwary, Jeremy Colls, Air Pollution, 2017
One can argue that application of natural vegetation to control air pollution may not be effective since plants, particularly tree species, release substantial amounts of non-methane biogenic volatile organic compounds (BVOCs) including isoprene (C5H8), monoterpenes (C10H18), sesquiterpenes (C15H28) and oxygenated compounds (CnH2n–2O). These compounds can accentuate air pollution through production of secondary organic aerosols (SOAs). Results from recent laboratory studies suggest that acid-catalysed multiphase reactions of isoprene produce oligomeric humic-like material resulting in substantial aerosol formation. Recent research also suggests possible enhancement in the generation of aerosols from isoprene and its oxidation derivatives (e.g. methacrolein and methyl vinyl ketone) via condensed phase reactions with hydrogen peroxide. In addition, some of the BVOCs (e.g. isoprene), owing to their alkene chemical structure, play important roles in suppressing concentrations of the hydroxy (OH) radical, enhancing the production of peroxy (HO2 and RO2) radicals, enhancing tropospheric CO concentrations, generating organic nitrates that can sequester NOx and allowing long-range transport of reactive N. The latter plays a vital role in atmospheric chemistry as it leads to photochemical production of tropospheric ozone.
Volatile organic compound and particulate emissions from the production and use of thermoplastic biocomposite 3D printing filaments
Published in Journal of Occupational and Environmental Hygiene, 2022
Antti Väisänen, Lauri Alonen, Sampsa Ylönen, Marko Hyttinen
The concentrations of carbonyl compounds were notably affected by the higher extrusion temperature of the 3D printer in comparison to the lower processing temperature used during filament production. The measured carbonyl concentrations are presented in Table 3. 2-Butanone, acetaldehyde, acetone, and formaldehyde were the most abundantly encountered carbonyls which together contributed for 84–98% of the cumulative carbonyl concentrations which ranged between 60–91 µg/m3 during filament extrusion and 190–253 µg/m3 during 3D printing. Acetone was detected in the highest concentration, at 83 µg/m3 level during 3D printing of pure PLA. Peak concentrations for 2-butanone, acetaldehyde and formaldehyde were 73, 32, and 41 µg/m3, respectively, measured while printing different BC feedstocks. Several other carbonyls (acrolein, methacrolein and benzaldehyde) were detected at low (below 5 µg/m3) concentrations as well. The following carbonyls were detected at below 5 µg/m3 levels in the background: 2-butanone, acetaldehyde, acetone, acrolein, formaldehyde, hexaldehyde, and propionaldehyde. The used analysis method was selective and only the compounds in the reference material were able to be identified, and other carbonyls evaded the method. However, no distinct phantom peaks representing unidentified compounds were found in the chromatograms.
Chemical characterization of nanoparticles and volatiles present in mainstream hookah smoke
Published in Aerosol Science and Technology, 2019
Véronique Perraud, Michael J. Lawler, Kurtis T. Malecha, Rebecca M. Johnson, David A. Herman, Norbert Staimer, Michael T. Kleinman, Sergey A. Nizkorodov, James N. Smith
Two exceptions exist when comparing experiments ran with and without water in the waterpipe bowl, which are the ions observed at m/z 33.034 and 47.049 (attributed to methanol and ethanol respectively). Those ions appear to be particularly sensitive to the presence of water, for which a strong filtration effect is observed as illustrated in the expanded mass spectra in SI Figure S11. This observation is consistent with their respective Henry’s law constant (KH), which are 2.03 and 1.7 mol m−3 Pa−1 respectively (Sander 2015). It is not surprising to observe no filtration effect for carbonyls compounds measured in this study as their KH values by comparison is much smaller with average values of, for example, 0.14 mol m−3 Pa−1 for acetaldehyde and 0.10 mol m−2 Pa−1 for acrolein (Sander 2015). Following a similar analysis, Al Rashidi, Shihadeh, and Saliba (2008) previously demonstrated that acetaldehyde, acrolein, propionaldehyde and methacrolein all remained in the gas phase, while formaldehyde, the most soluble of the carbonyl compounds measured, was found in the particle phase due to its much higher solubility, KH ∼ 43 mol m−3 Pa−1 (Sander 2015).
A perspective on the development of gas-phase chemical mechanisms for Eulerian air quality models
Published in Journal of the Air & Waste Management Association, 2020
William R. Stockwell, Emily Saunders, Wendy S. Goliff, Rosa M. Fitzgerald
Early versions of the GEOS-Chem included inorganic chemistry to simulate H2O2 and other products that are produced at low NOx concentrations. It also included inorganic species for NOx, HNO3, three peroxyacyl nitrates, and two different organic nitrate compounds were included because of their importance in simulating O3 formation and the long-range transport of nitrogen oxides (Horowitz et al. 1998). GEOS-Chem treated less reactive alkanes, methane, ethane, and propane while extensive use was made of surrogate species to represent other alkane chemistry (Horowitz et al. 1998). Propene represented all alkenes with three or more carbon atoms while butane was used to represent all VOCs with four or more carbon atoms. VOCs were summed into butane or propene according to class and the number of carbon atoms of the aggregated VOC species. Many of VOCs emitted in highly polluted urban areas, such as aromatic hydrocarbons, were ignored because the mechanism developers’ focus was on the simulation of global ozone concentrations. The version of GEOS-Chem developed by Horowitz et al. (1998) includes isoprene but not terpenes to represent biologically emitted compounds. The isoprene scheme is rather extensive. There are some emissions of aldehydes and ketones which are also oxidation products of hydrocarbons. These compounds are represented in the GEOS-Chem mechanism by formaldehyde, acetaldehyde, methacrolein, higher aldehydes (RCHO), acetone, methyl vinyl ketone and higher ketones (MEK). GEOS-Chem includes an extensive scheme for the reactions of HO2 and organic peroxy radicals which is necessary for modeling low NOx conditions.