Nitrogen resistance

Schcr/cr, J., and McArthur, D. R, Nitrogen Resistance of FCC Catalysts, presented at Katalistiks 8th Annual FCC. Symposium, Venice, Italy, 1986,... 

High nitrogen resistant catalysts and/or nitrogen traps are available nowadays unfortunately, no real breakthroughs have been made in reducing the effect of polycyclic aromatics (Conradson Carbon Catchers ). At present super low delta coke catalysts are produced to allow for the additional coke produced by these polycyclic aromatics. 

For the first type of poisons, we can either try to apply the same approach as with vanadium meaning specific catchers or offer a sufficient excess of acid sites sacrificial sites in order to reduce the relative impact of the poisoning. For instance, in the case of a nitrogen resistant catalyst, usually the catalyst design will involve a relatively high rare-earth and high zeolite content catalyst with the option of additional sacrificial sites in the form of active alumina (12). 

In nitrogen, resistance to pure thermal degradation decreases depending on the type of the side groups R and R" (when R = R = CH3) in the following order ... 

Nitrogen Resistant Resistant 300 °C (7 >300°C embrittlement owing to dissolved nitrogen) 400°C (r>400°c embrittlement owing to dissolved nitrogen)... 

Titanium, when pure, is a lustrous, white metal. It has a low density, good strength, is easily fabricated, and has excellent corrosion resistance. It is ductile only when it is free of oxygen. The metal, which burns in air, is the only element that burns in nitrogen. 

Hafnium is resistant to concentrated alkalis, but at elevated temperatures reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Halogens react directly to form tetrahalides. 

Rhenium catalysts are exceptionally resistant to poisoning from nitrogen, sulfur, and phosphorus, and are used for hydrogenation of fine chemicals. 

Despite its V excessive character (340), thiazole, just as pyridine, is resistant to electrophilic substitution. In both cases the ring nitrogen deactivates the heterocyclic nucleus toward electrophilic attack. Moreover, most electrophilic substitutions, which are performed in acidic medium, involve the protonated form of thiazole or some quaternary thiazolium derivatives, whose reactivity toward electrophiles is still lower than that of the free base. 

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

The XeF+ cation forms Lewis acid—base adduct cations containing N—Xe—F linkages with nitrogen bases that are resistant to oxidation by the strongly oxidizing XeF+ cation having an estimated electron affinity of the XeF+ cation of 10.9 eV (12). The thermally unstable colorless salt,... 

Process. Any standard precursor material can be used, but the preferred material is wet spun Courtaulds special acrylic fiber (SAF), oxidized by RK Carbon Fibers Co. to form 6K Panox B oxidized polyacrylonitrile (PAN) fiber (OPF). This OPF is treated ia a nitrogen atmosphere at 450—750°C, preferably 525—595°C, to give fibers having between 69—70% C, 19% N density less than 2.5 g/mL and a specific resistivity under 10 ° ohm-cm. If crimp is desired, the fibers are first knit iato a sock before heat treating and then de-knit. Controlled carbonization of precursor filaments results ia a linear Dow fiber (LDF), whereas controlled carbonization of knit precursor fibers results ia a curly carbonaceous fiber (EDF). At higher carbonizing temperatures of 1000—1400°C the fibers become electrically conductive (22). 

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