Catalytically stabilized thermal

Hung, S. L. and Pfefferle, L. D., ES T research Methyl chloride and methylene chloride incineration in a catalytically stabilized thermal combustor. Environ. Sci. Technol., 23(9) 1085-1091 (1989). 

Halogenated hydrocarbons may be destroyed by incineration, hydrolysis with caustic alkalies, and biodegradation. Ultrahigh destruction of volatile organic compounds to sub-ppt level in fumes or air stream has been reported using catalytically stabilized thermal incineration process (Pfefferle 1992). Methylene... 

In the conventional catalytically stabilized thermal (CSX) combustion approach (Beebe et al., 2000 Carroni and Griffin, 2010 Carroni et al., 2003) shown in Fig. 3.1 A, fractional fuel conversion is achieved in a catalytic honeycomb reactor operated at fuel-lean stoichiometries, while the remaining fuel is combusted in a follow-up gaseous combustion zone, again at fuel-lean stoichiometries. Nonetheless, for diffusionally imbalanced limiting reactants with Lewis numbers (Le) less than unity (such as H2 whereby Lch2 0.3 at fuel-lean stoichiometries in air), CSX is compounded by the... 

Figure 3.1 Hetero-Zhomogeneous combustion methodologies in power generation (A) catalytically stabilized thermal combustion (CST) and (B) fuel-rich catalytic/gaseous-lean combustion.

During coal conversion, the coal structure influences both thermal and catalytic reactions. Thermal reactions of solid coals initiate the breakage of weak bonds at rates proportional to their bond dissociation energies. The radicals thus produced require stabilization by hydrogenation or addition of small molecules otherwise the radicals couple to produce much more thermally stable bonds, which eventually leads finally to the formation of infusible and insoluble coke. 

The crystalline structure of modified zeolites determine a number of properties which are specific and favorable for catalytic reactions. The complete or partial loss of crystalline structure during catalytic reactions or regeneration is in most cases accompanied by decreased catalytic activity. Thermal stability or structural stability characteristics are therefore suitable for evaluating such catalysts or supported catalysts. 

Important properties of zeolite adsorbents for a fixed-bed application are adsorptive capacity and selectivity, adsorption-desorption rate, physical strength and attrition resistance, low catalytic activity, thermal-hydrothermal stability, chemical stability, and particle size and shape. Apparent bulk density of zeolite adsorbents is important because it is related to the adsorptive capacity per unit volume and also somewhat to rate of adsorption and desorption. However, more important properties related to the rates and therefore to the actual useful capacity would be the zeolite crystal size and the macropore size distribution. Although the ultimate basis in selecting a zeolite adsorbent for a specific application would be the performance, the price, and the projected service life of a product, these factors depend largely upon the above properties. 

A catalytic combustor is basically a lean-prenux combustor, in which the combustion is stabilized by a catalytic surface Hence, the expression catalytically ignited thermal combustion or catathermal combustion is also used [15] The catalyst stabilizes the combustion at low temperatures, which broadens the window in which both CO and NO are sufficiently low cf. Fig. 3. The next section briefly discusses the prominent features of catalytic combustion. 

In this work Micro Activity Tests with an aluminosilicate MCM-41 and a silica-containing VPI-5 were carried out using n-hexadecane as the model feed. Special emphasis was given to the catalytic activity, thermal stability and selectivity of the different materials studied in comparison with a commercial equilibrium FCC catalyst. Additionally, the possible structural and textural changes during the above-mentioned catalytic process were characterized. 

Catalytic combustion was originally discovered in the early 1970 s [23]. The concept is based on the observation that catalysts can be used to light off combustion reactions and to sustain gas-phase oxidation reactions after the catalyst. Peak temperatures obtained via catalytic combustion are significantly lower than those achieved in admixed or premixed flames consequently, NOx emissions are lower. Catalyst requirements include low light-off temperature, low reactor backpressure at high volumetric flow rates, high temperature stability, thermal shock resistance and durability. 

In recent years there has been tremendous interest in porous ceramics because of their applications as filters, membranes, catalytic substrates, thermal insulation, gas-burner media and refractory materials. These are due to their superior properties, such as low bulk density, high permeability, high temperature stability, erosion/corrosion resistance and excellent catalytic activity. One branch of this field is porous SiC ceramics, owing to their low thermal expansion coefficient, high thermal conductivity and excellent mechanical properties. However, it is difficult to sinter SiC ceramics at moderate temperatures due to their covalent nature. In order to realize the low temperature fabrication of porous SiC ceramics, secondary phases may be added to bond SiC. Oxidation bonded porous SiC ceramics have been found to exhibit good thermal shock resistance owing to the microstructure with connected open pores. 

CPO catalytic partial oxidation CST catalyticaUy stabilized thermal combustion i-CST inverse catalyticaUy stabilized thermal combustion IGCC integrated gasification combined cycle... 

SSA Particle size Crystallinity Catalytic activity Thermal stability... 

It should induce no change in sample composition. It should not exhibit discrimination based on differences in boiling point, polarity, concentration or thermal/catalytic stability. 

There are at least two mechanisms available for aziridine cis-trans isomerism. The first is base-catalyzed and proceeds via an intermediate carbanion (235). The second mechanism can be either thermally or photochemically initiated and proceeds by way of an intermediate azomethine ylide. The absence of a catalytic effect and interception of the 1,3-dipole intermediate provide support for this route. A variety of aziridinyl ketones have been found to undergo equilibration when subjected to base-catalyzed conditions (65JA1050). In most of these cases the cis isomer is more stable than the trans. Base-catalyzed isotope exchange has also been observed in at least one molecule which lacks a stabilizing carbonyl group (72TL3591). 

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