Periodic activity catalytic reactions

Periodic activity catalytic reactions, 27 59-94 experimental observation, 27 64-73, 75-77, 87, 88... 

Table IV and Fig. 3 provide a comparison of the effectiveness of some of the activators. These comparisons are based on the amounts of C6 dienes produced within a given period of time after the addition of the organic chloride to a totally inactive Rh1 complex. As can be seen from Fig. 3, the very best activator triggers the catalytic reaction with almost unnoticeable induction period, while a substantial induction period is apparent with the least efficient activator.

Hysteresis and Periodic Activity Behavior in Catalytic Chemical Reaction Systems VladimIr HlavaCek and Jaroslav VOTRUBA... 

Studies regarding the nature of the catalytically active species for NHC complexes in Heck-type reactions have focused on the Mizorvki—Heck reaction and have consistently revealed a palladium(O) species as the active catalyst. The induction period is shortened upon addition of a reducing agent,and postulated intermediates of the reaction were isolated and characterized as well as employed in stoichiometric and catalytic reactions. Theoretical studies using DPT calculations showed the mechanism for NHC complexes to most likely he in agreement with phosphine chemistry. ... 

Figure 2.11 shows the corresponding reaction profile. It begins with an induction period (the small plateau at low t values), and then proceeds as a first-order reaction. Once the system reaches the equilibrium between the precursor D and the active catalytic intermediate Q, the overall reaction rate reflects the first-order rate-... 

Catalytic conversions were experimentally studied in Russia toward the end of the nineteenth century, and especially in the twentieth century, and regularities were empirically established in a number of cases. The work of A. M. Butlerov (1878) on polymerization of olefins with sulfuric acid and boron trifluoride, hydration of acetylene to acetaldehyde over mercury salts by M. G. Kucherov (1881) and a number of catalytic reactions described by V. N. Ipatieff beginning with the turn of the century (139b) are widely known examples. S. V. Lebedev studied hydrogenation of olefins and polymerization of diolefins during the period 1908-13. Soon after World War I he developed a process for the conversion of ethanol to butadiene which is commercially used in Russia. This process has been cited as the first example of commercial application of a double catalyst. Lebedev also developed a method for the polymerization of butadiene to synthetic rubber over sodium as a catalyst. Other Russian chemists (I. A. Kondakov I. Ostromyslenskif) were previously or simultaneously active in rubber synthesis. Lebedev s students are now continuing research on catalytic formation of dienes. 

Pre-activation of the catalyst, heat-up, pressurization, and a period of thermal reaction are accomplished after the reactor is sealed, but before there is contact between catalyst and slurry. The catalytic period starts when the basket is dropped into the liquid and stops when the heater is removed from the autoclave. 

Similarly, Hsp is found to inhibit catalytic reaction on spillover-activated surfaces this gives rise to an induction period for hydrogenation (shown in Fig. 11) (134). 

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