Catalysts leave

The stripped catalyst is picked up by a stream of air and carried into the regenerator where the carbon is burned at temperamres about 1100-1300°F. Entrained catalyst is again removed by cyclones and the flue gas goes out the stack. The hot, regenerated catalyst leaves the regenerator and takes with it much of the heat of combustion. This is carried over to the reactor to vaporize the feed and to balance the endothermic heat of cracking. Thus, the process is heat balanced. 

Catalyst stripping the introduction of steam at a point where spent catalyst leaves the reactor in order to strip (i.e., remove) deposits retained on the catalyst. 

The proportions of ZnCl f/NH3 and ZnCl2 j/NH4C1 depend on the ratio of nitrogen to sulfur in the feed. In addition to these inorganic compounds, the catalyst leaving the hydrocracker also contains residual carbon that cannot be distilled out of the melt. In the case of direct coal hydrocracking, the catalyst also contains the coal ash. 

A simultaneous countercurrent movement of solid and gaseous phases makes it possible to enhance the efficiency of an equilibrium limited reaction with only one product (Fig. 4(a)) [34]. A positive effect can be obtained for the reaction A B if the catalyst has a higher adsorption capacity for B than for A. In this case, the product B will be collected mainly in the upper part of the reactor, while some fraction of the reactant A will move down with the catalyst. Better performance is achieved when the reactants are fed at some side port of the column inert carrier gas comes to the bottom and the component B is stripped off the catalyst leaving the column (Fig 4(a)). The technique was verified experimentally for the hydrogenation of 1,3,5-trimethylbenzene to 1,3,5-trimethylcyclohexane over a supported platinum catalyst [34]. High purity product can be extracted after the catalytic reactor, and overequilibrium conversion can be obtained at certain operating conditions. 

The used catalyst is reacted with propylene to convert the acid to diisopropyl sulfate. The diisopropyl sulfate is extracted with isobutane, the extract treated with a small amount of used catalyst, leaving a weak acid containing the conjunct polymer and water. The isobutane extract free of conjunct polymer and water is charged to alkylation, along with additional olefin and fresh make-up acid. A discussion of the reaction conditions required and the variables Involved In the four steps of the process are given. 

After diffusion towards and adsorption on the surface-active sites, the reactants are converted to products. Those products then desorb and diffuse out of the catalyst, leaving the active centers available for new incoming reactants. That way, the catalytic cycle can be repeated many times on each active site. For this to work, however, the bond strength between the adsorbed siuface species and the active sites... 

This evidence suggests that not all Na species are mobile. Some Na species must in fact have reacted irreversibly with components on the catalyst, leaving it unavailable to poison the acid sites. It is likely that these reactions occur during the early stages of hydrothermal deactivation. The exact mechanism is unclear, but may involve reactions with extraffamework alumina. As the zeolite dealuminates from 24.55 to 24.25A unit cell size, approximately 65% of the initial framework alumina (about 15 wt% of the zeolite) comes out of the zeolite structure. Sodium, which also must leave the exchange sites as the zeolite dealuminates may react with this very reactive form of alumina. The other possibility is that as kaolin undergoes its transition to metakaolin at 800K... 

Kinetic effects of a different nature occur if the strong catalyst poisons diffuse so slowly that at first only the outer parts of the catalyst particles are poisoned (shrinking-core model, as discussed for dewaxing (10)) or that these poisons are converted in the outer layers of the catalyst, leaving a clean active core (11). 

The catalyst emerging from the bottom of the reactor passes through a depressuring pot, and the steam that escapes from the catalyst is removed by a small jet condenser. Completeness of the purge is checked by inspecting the steam condensate for traces of oil. The temperature of the catalyst leaving the reactor is of the order of 875 F. (with a catalyst inlet temperature of 1000°F.), and carbon content is of the order to 2 to 4 wt. %. 

An improved air distributor has been developed that consists of many pipes equally spaced in concentric circles in a dished head at the bottom of the upper burning zone (292). Each air pipe is covered with a cap containing louvers, and projects only slightly below the head. Catalyst leaves the burning zone through other pipes in the dished head, which are open at the top and project farther below the head to e.stablish the catalyst... 

The carbon is almost completely removed during regeneration in the Houdry fixed-bed process, but not in circulating-catalyst processes. Thus, the carbon content of catalyst leaving the regenerator has been reported to be less than 0.5% in TCC units (158,241), and in the range from 0.3 to 1.0% (usually 0.3 to 0.7%) in fluid-catalyst units (305). 

The simultaneous reaction and catalyst extraction shown in Figure 6 (a) is not favorable, due to the fact that the catalyst leaves the reaction medium during the reaction. The successive reaction and catalyst extraction shown in Figure 6 (b), where reaction and extraction are carried out in two different units, is however much... 

Reduction of nitro compounds to amines is a synthetically important reaction (98) and is practiced since the birth of modern chemical industry—many aromatic amines are key intermediates in production of dyes and pesticides. However, the stoichiometric reductions using iron or alkali metal hydrogen sulfides or catalytic hydrogenations with heterogeneous catalysts leave room for improvements in selectivity, especially with reference to halonitro-derivatives. There are many homogeneous catalysts such as the rhodium carbonyls in the presence of amines or chelating diamines, or [Rus(CO)i2] in basic amine solutions that are... 

Moving-bed reactors are preferred when there is a need for continuous catalyst regeneration. In this operation, fresh catalyst is fed from the top of the reactor, and it moves in the downflow direction by gravitational forces. Spent catalyst leaving the reactor at the bottom is usually replaced in the continuous mode. While the catalyst movement is downward, reactive mixture flow can be cocurrent or countercurrent to that of the catalyst flow. 

The term moving bed arises from the mode in which the spent catalyst is replaced. The catalyst bed is displaced periodically downward by gravitational forces. The fresh catalyst enters at the top of the reactor, and the deactivated catalyst leaves the reactor through the bottom. Liquid flow can be supplied either cocurrently or countercurrently with respect to the movement of the bed. The rate of deactivation determines how frequently the catalyst is replaced. Commonly, catalyst replacement is a batch operation and is done once or twice a week [68]. 

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