Equilibrium catalyst degradation

All available laboratory and pilot plant data on reaction and phase equilibrium behaviors, catalyst degradation, and life and corrosion of equipment. 

Fig. 12.7. Equilibrium curves, heatup paths and intercepts for 12 volume% S02 feed gas. 690 K feed gas gives a 915 K intercept temperature, in the catalyst degradation range. 660 K feed gas gives a 900 K intercept temperature, avoiding degradation.

Fig. 12.8. Heatup path, equilibrium curve and intercept for 660 K, 13 volume% S02 feed gas. With 13 volume% S02 and higher, catalyst degradation is likely even with 660 K feed gas. 660 K is about the lowest temperature at which V, alkali metal, S, 0, Si02 catalyst is fully active.

It is not exactly understood how the mixed ligand Rh/dppb/PPh3 catalyst system functions. Matsumoto proposed that the arm-on, arm-off equilibrium shown in Scheme 12 is operational. A species such as (5) would function much like a normal HRh(CO)(PPh3)2 catalyst, but the ability to reform the chelate to form a slightly more electron-rich complex (6) would tend to inhibit alkene isomerization and/or degradation reactions which require 16e unsaturated species. P NMR studies of Rh/chelating phosphine complexes indicate that a variety of species can form, the most dominant of which are... 

Indeed using (V)-Mo(Vl) rather than (lII)-Mo(VI) leads to a lower equilibrium constant of the catalyst-hydroperoxide complex K3. Since once again no degradation occurs, the decomposition of the catalyst is apparently inhibited when Kj is sensibly lower than Kt,ep-... 

Wallace and Morrow used halogenated alcohols, such as 2,2,2-trichloroethyl, to activate the acyl donor and thereby improve the polymerization kinetics [53, 56], They also removed by-products periodically during reactions to further shift the equilibrium toward chain growth instead of chain degradation. They copolymerized bis(2,2,2-trichloroethyl) tmns-3,4-epoxyadipate and 1,4-butanediol using porcine pancreatic lipase as the catalyst. After 5 days, an enantioenriched polyester with Mw = 7900 g mol-1 and an optical purity in excess of 95% was formed (Scheme 4.6). 

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