Coke oxidation conditions

The reactor impregnated with nickel showed inferior performance again. Deactivation was observed, which was assumed to originate from coking, sintering, oxidation of the nickel or even losses of volatile nickel species. With increasing temperature, enhanced formation of by-products, namely methane and ethane, was observed in the reformate both under partial oxidation conditions and in the autothermal mode, which was attributed to thermal cracking. 

Catalysts behaviour in the reduction reaction of NOx with methane under distinctly oxidizing conditions supports the literature data showing that the reducing agent for NOx could be represented by certain species deposited on catalyst siuface (probably coke) which make possible NOx reduction even after the complete oxidation of the methane fi om the reaction medium [8]. 

There is one exception in these results using propane relative to those obtained when propylene was used to represent the hydrocarbon in extremely lean conditions, the HC activity was enhanced by the presence of SO2 this effect has been reported in previous laboratory studies of propane oxidation [26], We suggested previously that SO2 promotes acid catalysis of propane dehydrogenation, only in this case, the carbonaceous material may be more easily removed from Pt-Rh than from Pd under oxidizing conditions, thus complete oxidation of propane dominates over coking. Other factors, however, may also be... 

Thermal Plasma Conversion of CoaL Compare production of CO and CO2 by oxidation of coke in reactions (10-32) and (10-33) in thermal plasma conditions. Taking into accormt relation (10-34) between the coke oxidation rate coefficients, calculate temperatures at which CO and CO2 production becomes equal at relatively low and relatively high pressures. 

Regeneration is generally carried out through removal of coke under oxidative conditions. Coke oxidation like coking and deactivation is a... 

Whatever the operating conditions, in the presence or absence of NH3, the CO yield increased with the reaction temperature and a 100% yield was obtained at 400°C (Fig. 5.13b). However, at 300°C, while 1-MN was fully transformed in the presence of NH3, only 10% carbon dioxide was produced, mainly because of the formation of oxygenated compounds retained in the zeolite pores ( coke )7 which was favoured by NH3 as revealed by elemental analysis showing a larger amount of carbon after the reaction. As for the coke oxidation reaction, it was shown that 1-MN oxidation into carbon dioxide required strong Brpnsted acid sites. In our case, the basic character of NH3 favours its adsorption at low temperatures on strong acid sites, which are able to transform 1-MN into carbon dioxide. Indeed, at 300°C the carbon dioxide yield was close to 20% in the absence of NH3 as opposed to 10% in the presence of NH3. When the reaction was carried out with NH3, only the weaker sites were able to work, but these sites seemed to be active only in the conversion of 1-MN into intermediate oxygenated compounds that remained adsorbed on the solid surface. 

Sulfur oxide transfer additives work more effectively if a combustion promoter such as platinum is used to oxidize sulfur dioxide to sulfur trioxide more efficiently. More additive is required when a unit is operating under less oxidizing conditions and the coke is only partially converted to carbon dioxide. 

Titanium slag and synthetic mtile are also used as raw materials in the production of titanium whites. Titanium slag results from a metaHurgical process during which iron (qv) is removed from ilmenite by reduction with coke in an electric arc furnace at 1200—1600°C. Under these conditions, iron oxide is reduced to metal, melts, and separates from the formed titanium slag. Titanium slag contains 70—75% Ti02 and only 5—8% iron. 

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

Reaction of coke with calcium oxide gives calcium carbide, which on treatment with water produces acetylene. This was for many years an important starting point for the production of acrylonitrile, vinyl chloride, vinyl acetate and other vinyl monomers. Furthermore, during World War II, Reppe developed routes for many other monomers although these were not viable under normal economic conditions. 

Last but not least, one should check the inertness of the auxiliary electrodes in single-pellet arrangements, both under open and closed circuit conditions and, also, via the closure of the carbon balance, the appearance of coke deposition. This is especially important in systems with a variety of products (e.g. selective oxidations), where the exact value of selectivity towards specific products is of key interest. This in turn points out the importance of the use of a good analytical system and of its careful calibration. 

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