Alumina, activated regeneration

Allyl alcohol, 26, 4 Allyl bromide, 25, 49 Allyl chloride, 24, 97 27, 7 Allyl cyanide, 24, 96, 97 Allyl ether, 26, 5 Allyl lactate, 26, 4 Alumina, activated, 23, 25 regeneration of, 23, 25 Aluminum, commercially pure (2S), 21, 9... 

Adsorption regeneration (desoiption) (Continued) pressure-swing temp erature- sw ing cooling considerations heating considerations Alumina, activated Amines, tertiary Antoine equation Association reactions Atomic volumes Axial mixing Azeotropic distillation calculations selection of entrainer... 

The alumina or sodium alurninosiHcate catalysts used to regenerate degraded working solutions lose activity with time as active soda sites are neutralized, but these too can be regenerated. 

Usually best choice for desiccation of gases (<3% water) such as argon, helium, hydrogen, chlorine, hydrogen chloride, sulfur dioxide, ammonia, air, and chemical classes such as aliphatics, aromatics, halogenated compounds, oxygenated compounds (siUca gel, zeoHtes, activated alumina all alternatives some regenerable, some not). 

Complete removal of water from the pyrolysis gas is achieved with molecular sieve dryers. Typically, there are two dryers one is in normal operation while the other is being regenerated. The dryers are designed for 24 to 48 hours between successive regenerations and high pressure methane heated with steam at 225°C is the preferred regeneration medium. Activated alumina was used in older plants, but it is less selective than molecular sieves (qv). 

Catalytic Pyrolysis. This should not be confused with fluid catalytic cracking, which is used in petroleum refining (see Catalysts, regeneration). Catalytic pyrolysis is aimed at producing primarily ethylene. There are many patents and research articles covering the last 20 years (84—89). Catalytic research until 1988 has been summarized (86). Almost all catalysts produce higher amounts of CO and CO2 than normally obtained with conventional pyrolysis. This indicates that the water gas reaction is also very active with these catalysts, and usually this leads to some deterioration of the olefin yield. Significant amounts of coke have been found in these catalysts, and thus there is a further reduction in olefin yield with on-stream time. Most of these catalysts are based on low surface area alumina catalysts (86). A notable exception is the catalyst developed in the former USSR (89). This catalyst primarily contains vanadium as the active material on pumice (89), and is claimed to produce low levels of carbon oxides. 

Used alumina can be regenerated by repeated extraction, first with boiling methanol, then with boiling water, followed by drying and heating. The degree of activity of the material can be expressed conveniently in terms of the scale due to Brockmann and Schodder (Chem Ber B 74 73 1941). 

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