Combustion activities

Water vapor is generated indoors due to human metabolism, cooking and taking showers, unvented combustion activities and by humidifiers water and moisture leaks through roof or building envelope improperly maintained HVAC equipment... 

VOCs are emitted indoors by building materials (e.g., paints, pressed wood products, adhesives, etc.), equipment (photocopying machines, printers, etc.), cleaning products, stored fuels and automotive products, hobby supplies, and combustion activities (cooking, unvented space heating, tobacco smoking, indoor vehicle use). 

In the case of H2 oxidation the two investigated classes of catalysts show different behaviors. Again perovskite type catalysts calcined at 973 K show higher combustion activity than hexaaluminates calcined at 1573 K, but characteristic values of parent activation energy (5-7 Kcal/mole) have been calculated for perovskite catalysts that are markedly lower than... 

Recently revised test methods have revealed that nonluminous or barely luminous combustion reactions are occurring where previously it was reported that no combustion activity was occurring based on flame observance. 

Such key features are strongly interconnected via the complex behavior of supported palladium. It is well known that CH4 combustion activity depends markedly on the oxidation state of palladium. In Figure 12.8, a typical conversion curve obtained in temperature-programmed combustion (TPC) experiments during heating/cooling cycles is plotted. 

The variations of CH4 combustion activity associated with the PdO-Pd reversible transformation are responsible for the unique thermostating ability of palladium-supported catalysts. Indeed, in the adiabatic combustion of CH4, the... 

It is worth noting that, in order to match the combined requirements of high combustion activity and durability under harsh operating conditions, catalysts with a high Pd loading (about 10% w/w) must be adopted [16, 98]... 

Rh, Ru, Pd) and oxides (<4wt% Fe jO4/Cr2O3, La2O3, SnO2, K2O) was recently performed by Lodeng et al. [134]. A comparison with Ni- and Fe-based catalysts was also addressed. It was found that addition of metal promoters, particularly Rh and Pt, enhanced the catalyst activity at low temperatures (which resulted in delayed extinction of the reaction during ramping at —1 Tmin ). However, addition of Ni promoted carbon formation. Addition of surface oxides typically promoted instability, deactivation and combustion (hence the formation of a stable Co metallic phase was hindered). It was found that Ni performed better than Co-based catalysts at all temperatures. However, Fe-based catalysts showed high combustion activity. 

Characterization studies of the final materials are also examined in order to clarify the relevant properties for high-temperature combustion, including detailed structural features and their relation to sintering behavior and combustion activity and role and nature of transition metal ion in the structure. 

Catalytic Combustion Properties of M-substituted Hexaaluminates - Most of the catalytic studies performed over hexaaluminate materials deal with the combustion of CH4 as the main component of natural gas, i.e., the typical fuel of gas turbines. Arai and co-workers were the first to investigate the CH4 combustion activity of BaMAlnOjg with M=Cr, Mn, Fe, Co, Ni prepared via the alkoxide route.5 Activity tests were performed over powder catalysts using a conventional quartz microreactor fed with a diluted CH4-air mixture (1% CH4) at high-space velocity (GHSV=48000 h 1). The results are summarized in Table 3 in terms of T10% (i.e., the temperature required to achieve 10% conversion). 

However, the extent of the activity enhancement cannot be related to the higher surface area of this material. Two possible explanations were proposed to account for the effect of mirror plane composition on combustion activity one is related to the different oxidation state of the cation in the mirror plane the other is associated with the crystal structure of layered-alumina materials (i.e., magne-toplumbite and (3-Al203) which have different population and co-ordination of the ions in the mirror planes. Both these electronic and structural factors can, in principle, affect the redox properties. 

No limits on the content of transition metal ion were found for Fe-substituted systems. As mentioned above, and in line with crystallographic literature,45 a monophasic sample with magnetoplumbite structure was obtained for the completely substituted BaFe O. This sample showed excellent CH4 combustion activity upon calcination at 700 °C, but it markedly deactivated either upon increasing the calcination temperature or upon treatment at high tempera-... 

The crystal structure and the sintering behavior of hexaaluminates was widely investigated. The relation of sintering resistance to anisotropic ion diffusion in the layered alumina phase was clarified to a large extent. Other evidence suggests that combustion activity is obtained through a redox mechanism associated with reversible variation of oxidation state of the transition metal ions in the structure. Mn was the best and most stable active component. However, fundamental and applied studies are needed to better clarify the redox mechanism of the reaction and how it is related to the chemical and structural features of the Mn-containing layered-alumina phase. This could also provide useful information for the development of an optimum catalyst composition,... 

A successful correlation is obtained for the combustion reaction. For the first period tansition metal oxides, it is found that the combustion activity increases with decreasing heat of reduction (per atom of O) of the oxide to the next lower oxidation state (40). This correlation implies that lattice oxygen participates in the combustion reaction. Similar successful correlations have been observed for the combustion of CO, H2, CH4, and propene (47). 

Nanoparticles produced from anthropogenic sources can either be formed inadvertently as a by-product of combustion activities (i.e. emissions from road vehicles and industries) or produced intentionally (e.g. ENPs) due to their particular characteristics [15]. The following section describes the ENPs in detail and provides only a brief overview of other anthropogenic sources. 

In the pure form, CDDs are colorless solids or crystals. CDDs enter the environment as mixtures containing a variety of individual components and impurities. In the environment they tend to be associated with ash, soil, or any surface with a high organic content, such as plant leaves. In air and water, a portion of the CDDs may be found in the vapor or dissolved state, depending on the amount of particulate matter, temperature, and other environmental factors. 2,3,7,8-TCDD is odorless. The odors of the other CDDs are not known. CDDs are known to occur naturally, and are also produced by human activities. They are naturally produced from the incomplete combustion of organic material by forest fires or volcanic activity. CDDs are not intentionally manufactured by industry, except in small amounts for research purposes. They are unintentionally produced by industrial, municipal, and domestic incineration and combustion processes. Currently, it is believed that CDD emissions associated with human incineration and combustion activities are the predominant environmental source. 

Coal dust, coal fly ash Dusts generated by coal mining, processing, and combustion activities. Inhalation. Black lung — includes CWP, progressive massive fibrosis, chronic airway obstruction or bronchitis, emphysema possible silicosis due to intermixed crystalline silica. 

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