New Nanoparticle Formation under UV Impact on Acetaldehyde Vapor in Nitrogen and Air Flow

Abstract

This paper deals with the study of the kinetics of photolysis and photonucleation of acetaldehyde (AA) vapor in air and in nitrogen along with physical and chemical characteristics of the formed aerosol particles. Free radicals accompanying photonucleation were identified using the electron spin resonance spin-trapping technique. Numerical modeling of the photonucleation kinetics of AA, based on experimental results, was carried out. Rate of generation of primary products, leading to the nanoparticles, and the aerosol yield were evaluated. Chemical mechanism of stages leading to photonucleation in this system was proposed.

Water as a Clustering Agent in Photolysis and Photonucleation of Benzaldehyde Vapor

“…Because the calculation showed that the formation of a cluster with the participation of the carbonyl group of one BA molecule and the aromatic ring of another BA molecule is advantageous from the viewpoint of energy, it was interesting to check how the association of other aldehyde molecules (including those having no aromatic groups) could be predicted by the above-described calculation procedure. A detailed chemical analysis of the gaseous and aerosol products of the photolysis of CH 3 CHO carried out previously exhibited no dependence of glyoxal yield on water-vapor content. To test the adequacy of the theoretical approach proposed here, we calculated the energy of a similar clustering process in acetaldehyde.…”

Investigation of Aerosol Formation During Benzaldehyde Photolysis

“…This process leads directly to the formation of phenoxyl radical PhCO • and further to aerosol products. If the transformation really takes place in such a way, it becomes clear why the aerosol formation efficiency for BA photolysis in air is not so much different from that in inert gas as it was observed for acetaldehyde and formaldehyde photolysis 14,24 The most active radicals produced during photolysis in air and in nitrogen in the latter two systems sharply differ from each other in reactivity.…”

“…The aerosol formation kinetics was studied with the setup similar to that described elsewhere. , Figure shows the schematic of the setup. It consists of the flow reactor (5) (22 mm inner diameter, ca.…”

“…300 mm length), low-pressure Hg lamp DRT-240 (6), and a Novosibirsk-type automated diffusion battery (NADB). The NADB consists of an eight-stage screen-type diffusion battery (7), a turbulent mixing condensation enlarger with dibutyl phthalate as a working liquid (8), photoelectrical particle counter (9), and microprocessor controller (10), which was used to run the NADB and to transfer the data to the PC (11). , The NADB allows measuring aerosol particle concentration from 10 1 to 10 7 cm -3 with ±10% accuracy 17 and size distribution from 2 to 200 nm, using a multiple solution averaging inversion procedure . This inversion procedure was shown to reconstruct correctly multimodal size distributions and to resolve aerosol fraction with different size as separate peaks when the ratio of the mean diameters of fractions R = / is larger than 2.5 .…”

“…A decrease in φ aer value with an increase in water concentration is opposite to that observed for the photochemical aerosol formation in acetaldehyde vapor. 14 This can be explained by the fact that aerosol particles formed from acetaldehyde photolysis exhibit hydrophilic properties, while those formed from BA photolysis are hydrophobic.…”