Pre-oxidation

Process development on fluidized-bed pyrolysis was also carried out by the ConsoHdation Coal Co., culminating in operation of a 32 t/d pilot plant (35). The CONSOL pyrolysis process incorporated a novel stirred carbonizer as the pyrolysis reactor, which made operation of the system feasible even using strongly agglomerating eastern U.S. biturninous coals. This allowed the process to bypass the normal pre-oxidation step that is often used with caking coals, and resulted in a nearly 50% increase in tar yield. Use of a sweep gas to rapidly remove volatiles from the pyrolysis reactor gave overall tar yields of nearly 25% for a coal that had Eischer assay tar yields of only 15%. 

A multilayer-type structure probably due to cords in the molten zone between single arc sprayed (0.25 MPa) Ni droplets and steel substrate were found in AES point depth profiles [2.158]. That particular arc spraying condition turned out to yield the best adhesion. Plasma-sprayed AI2O3 layers separated from pre-oxidized Ni Substrate had a micrometer-thick NiO layer on the substrate-sided face and micrometer-deep oxide interdiffusion [2.159]. In this work also, AES point depth profiling substantiated technological assumptions about adhesion mechanisms. 

In order to have more infoimation on the nature of the oxygen species active in partial and total oxidation we investigated the interaction of the hydrocarbons with the pre-oxidized surfaces of oxides where different types of surface oxygen species are formed. In particular we investigated p-type semiconductors like chromia, chromites and cobalt oxide C03O4. Moreover, we studied n-type metal oxides like FezOs, metal ferrites and CuObased catalysts. 

Figure 12.4 A series of SFG spectra in the CO stretch region of chemisorbed CO on polycrystalline Pt in a CO-free 0.1 M H2SO4 electrolyte. The atop spectra were fit to (12.5) (see text) to extract the amplitude, frequency, and width [Lu et al., 2005 Lagutchev et al, 2006] (each displayed data point is the average of three or five spectra). The electrode potential was swept at a rate of 5 mV/s, and SFG spectra were obtained every 200 ms. Spectra were obtained at 1 mV intervals, but, to avoid congestion in the plot, averaged spectra are displayed at 10 mV intervals in the pre-oxidation region (V < 0.43 V) and at 3.3 mV intervals in the oxidation region (V > 0.43 V) [Lu et al., 2005].

Figure 1 IR spectra of products from gas reactions with pre-oxidized LLDPE...

SCR for heavy-duty vehicles reduces NOx emissions by 80%, HC emissions by 90% and PM emissions by 40% in the EU test cycles, using current diesel fuel (<350 ppm sulphur) [27], Fleet tests with SCR technology show excellent NOx reduction performance for more than 500000 km of truck operation. This experience is based on over 6 000 000 km of accumulated commercial fleet operation [82], The combination of SCR with a pre-oxidation catalyst, a hydrolysis catalyst and an oxidation catalyst enables higher NOx reduction under low-load and low-temperature conditions [83],... 

Figure 8.1. General procedure for OSC measurements over TWC catalysts. CO and C02 are separated over a small Porapak column inserted between the sample and the TC detector. The first CO pulse is injected over pre-oxidized sample. CO can be replaced by H2.

Figure 8.4. The FTIR spectra of adsorbed superoxide species during exchange of pre-oxidized Ceo63 ro 3702 with 1802 [14].

Figure 8.8. Temperature-programmed reaction of CO (l%) + NO (1%) over a pre-oxidized 0.2% Rh/Ce02—A1203 catalyst (Pirault and Marecot, unpublished results).

The main reactions, which have to be considered on SCR catalysts, are the standard-SCR, fast-SCR, and the N02-SCR reactions, beside the ammonia oxidation and the formation of N20. The fast-SCR reaction is promoted by N02 in the feed that can be generated from NO in a pre-oxidation catalyst. However, the right dimensioning of the oxidation catalyst is critical in order to prevent the production of an excess of hazardous N02. This problem is further aggravated if a continuous regenerating DPF is installed in front of the SCR system, as part of the N02 produced by the oxidation catalyst is always consumed in the filter for soot oxidation. 

Polyquaternary compound Shrink-resist effect after pre-oxidation Exceptional improvement in fastness All processing stages suitable Improves shrink-resist effect of polyether and polysiloxane types No improvement in handle Shrink-resist effect weaker than with other types Odour possible on chlorinated wool... 

Krishnamurty, K. V. et al., At. Abs. Newslett., 1976, 15, 68-70 When preparing soil and sediment samples for atomic absorption spectral analysis for trace metals, pre-oxidation with nitric acid before addition of hydrogen peroxide eliminates the danger of explosion. 

Determinations of iodate without pre-oxidation in Pacific seawater by the previous method gave a mean result of 583 ig/l with a standard deviation of 0.23 xg/l. For samples containing between 40 and 60 xg/l, standard deviations of 0.19 xg/l (iodate method with pre-oxidation), 0.12 xg/l (iodate method without pre-oxidation), and 0.43 ig/l (total iodine method) were obtained. 

A set of Pacific open-ocean samples were analysed for iodate-iodine using both the procedure which incorporates pre-oxidation with iodine water and that which does not. Also, in a similar exercise total iodine was determined using both the method that incorporates pre-oxidation with bromine water and the catalytic method using the reaction between Ce(IV) and As(III) [81]. Variance tests showed that differences between either replicates or methods was not significant. 

Truesdale and Smith [80] also carried out a comparative study of the determination of iodate in open ocean, inshore Irish seawaters and waters from the Menai Straits, using the spectrophotometric method (with and without pre-oxidation using iodine water) and also by a polarographic method [82]. 

S.-F. Kang, C.-H. Liao and M.-C. Chen, Pre-oxidation and coagulation of textile wastewater by the Fenton process. Chemosphere, 46 (2002) 923-928. 

Hydrodesulphurisation of coke, however, may be economically feasible (12). While this technique requires a source of hydrogen this, as will be discussed shortly, may be possible without a large net consumption of the hydrogen. Of particular interest is the observation that pre-treatment of the coke with caustic (13) and pre-oxidation (14) can significantly improve hydrodesulphurisation yields. 

Rosenwald (19) attributed the acceleration of the reactions involved in inhibitor sweetening to the reaction of an unidentified oxidation product of the amine with thiol to produce mercaptyl radicals. However, the oxidation of neat DSBPD is slow at 20°C. (3.3 X 10"5 mole of 02 per mole of amine per second) and partial pre-oxidation of the DSBPD until 0.26 mole of 0> was absorbed per mole of amine did not enhance the activity of the amine (compare curves B and C in Figure 3). Furthermore, allowing the co-oxidation to proceed for a time before adding the... 

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