Secondary emission decomposition

Secondary emission is any process that releases new airborne contaminants from existing sources, changes the total emittable mass of existing contaminants, or results in chemical reactions between compounds on surfaces and in the air. Secondary emission may be based on sorption, oxidation, hydrolysis, decomposition or other chemical reactions in or on a source or the indoor air. A secondary emission process is often highly influenced by past and present environmental conditions. It is not always possible to tell if a compound found in the air is there because of a primary or secondary emission process since a source may emit the same compound by both primary and secondary processes. Purposely added materials such as cleaning products may be a primary emission source, but reactions between constituents of new and existing products may cause a secondary emission process. 

On the other hand, considering the practical application, slip catalysts are generally required at the outlet of the SCR reactor in order to remove secondary emissions which typically include a certain concentration of ammonia, isocyanic acid (originating from incomplete urea decomposition), nitrous oxide, and nitrohy-drocarbons. ... 

The decompositions of these compounds are of interest since they are used as binders in electron-emissive coatings [1023]. The initial stage of the endothermic reaction in vacuum or nitrogen (520—820 K) yields residual carbonate and a small quantity of carbon. Changes in surface area during reactions have been measured. The main volatile product is HCHO, but secondary, exothermic reactions occur on the surface of the product carbonate so that the overall reaction is... 

The concept of intact emission of adsorbed molecular species for identifying reaction intermediates is also well illustrated in several recent studies. Benninghoven and coworkers (2-4,12) used SIMS to study the reactions of H2 with O2, C2H4 an< 2H2 on P°ly polycrystalline Ni. For the C2H /Ni interaction, for example, direct relationships could be established between characteristic secondary ions and the presence of specific surface complexes (12). In another study, Drechsler et al. (13) used SIMS to identify NH(ads) as the active intermediate during temperature-programmed decomposition of NH3 on Fe(110). 

The decomposition of the catalyst beads can cause a secondary air pollution emission consisting of the particulate dust generated by abrasion of the surface of the catalyst. Operating cost for catalyst replacement varies directly with catalyst attrition rate. The system can process waste streams with VOC concentrations of up to 25% of the lower explosive limit (LEL). The proprietary catalyst contains up to 10% chromium, including 4% hexavalent chromium. This could lead to the emission of hexavalent chromium in some applications of the technology. 

The plasma ionic liquid interface is interesting from both the fundamental and the practical point of view. From the more fundamental point of view, this interface allows direct reactions between free electrons from the gas phase without side reactions - once inert gases are used for the plasma generation. From the practical point of view, ionic liquids are vacuum-stable electrolytes that can favorably be used as solvents for compounds to be reduced or oxidised by plasmas. Plasma cathodic reduction may be used as a novel method for the generation of metal or semiconductor particles, if degradation reactions of the ionic liquid can be suppressed sufficiently. Plasma anodic oxidation with ionic liquids has yet to be explored. In this case the ionic liquid is cathodically polarized causing an enhanced plasma ion bombardment, that leads to secondary electron emission and fast decomposition of the ionic liquid. 

Table 7 lists the results of estimation of secondary electron emission coefficients for binaiy lead silicate glasses implemented by decomposition of Pb 4f and 0 1s spectra. The relative content of modifying lead is substantially overestimated, i.e. the coefficient x in the calculation formula for Nx is overestimated, which is the main reason for the elevated values of Oest. The values of secondary electron emission coefficients calculated by us agree well with experimental data. 

Several techniques have been used to follow explosive reactions on a shorter time scale, such as mass spectrometry [6,7,31,46] and emission spectroscopy [11-14]. Mass spectrometry seems more universal as it can identify many species relatively easily. But due to the inherent instability of especially explosive molecules and some of the decomposition intermediates, the ionisation process can generate secondary species. This influence of the ionisation process is difficult to avoid. Also, the time resolution achieved in mass spectrometric techniques is not high enough, unless sophisticated and expensive techniques are used. On the other hand, emission spectroscopy is a fast, non-intrusive, sensitive detection technique. Furthermore, there is little spectroscopic information about the decomposition reactions of explosives. It is this technique (emission spectroscopy) that has been used in the experiments described below to investigate fast (explosive) decomposition reactions induced by a nanosecond laser light pulse. 

The emission spectra of irradiated secondary explosives reveal the immediate presence of the decomposition products which remain present at later times. This suggests for HMX and RDX that the N-N bond is broken upon decomposition rather than the C-N bond. The spectra very closely resemble the emission spectra and its characteristics which have been observed during and after irradiation of polymers and biological tissues such as vascular tissues, the myocardium etc. This ablation process induced by UV laser light has been explained by the promotion of an electron into a dissociative state through intersystem crossing or internal conversion. Similar mechanisms are probably also operative in explosives. To obtain more insight into the decomposition reactions of explosives, more experimental results are needed. 

In the thermal decomposition of N2H4 in shock waves, NH(X) is formed in secondary reactions [20]. In shock-heated NH3-noble gas mixtures at high temperatures (T>3000 K) [37 to 39] and in a high-temperature plasma (T = 3200 K), emission from NH(A) was observed [40]. At lower temperatures in shock waves NH(X) was observed [41]. HN3 and HNCO can be pyrolyzed at significantly lower temperatures (T> 1200 K) under these conditions mainly NH(X) is formed [44, 45]. 

Based on the analysis, it can be concluded that 4-octoxy-4 -cyanobiphenyl was mainly decomposed into simple and environment-friendly products under the hydro-thermal condition. To avoid secondary environmental pollution, the decomposition products still need to be treated as waste water before emission. By further treatment, the environmental threats of 4-octoxy-4 -cyanobiphenyl could be completely relieved. 

---