Segmented bed reactors

The segmented-bed reactor allows better flexibility of liquid-to-solid (catalyst) ratio, thus allowing better variations in homogeneous and heterogeneous reaction rates when both are possible. High liquid holdup will, however, offer more resistance to the transfer of gaseous reactant to the catalyst surface. 

Reactor. The reactor used in this study was a pilot plant version of the Gulf patented (15) segmented bed reactor. The catalyst was held in tubes of 17 mm I.D. by 114 cm length constructed of 10-mesh (U.S.) stainless steel screen. In many of the runs, the catalyst charge was placed in four of the above tubes which typically held 750 g of the catalyst. Some runs were made using only one or two catalyst tubes by blocking off a portion of the reactor cross section. 

Fig. 2.4p shows three types of post-column reactor. In the open tubular reactor, after the solutes have been separated on the column, reagent is pumped into the column effluent via a suitable mixing tee. The reactor, which may be a coil of stainless steel or ptfe tube, provides the desired holdup time for the reaction. Finally, the combined streams are passed through the detector. This type of reactor is commonly used in cases where the derivatisation reaction is fairly fast. For slower reactions, segmented stream tubular reactors can be used. With this type, gas bubbles are introduced into the stream at fixed time intervals. The object of this is to reduce axial diffusion of solute zones, and thus to reduce extra-column dispersion. For intermediate reactions, packed bed reactors have been used, in which the reactor may be a column packed with small glass beads. 

Open tubular reactor ( ) Segmented reactor Hi) Packed bed reactor... 

However, the most complex analysis is that in which heat transfer through the reactor walls is taken into account. This type of operation must be employed when it is necessary to supply or remove energy from the system so as to moderate the temperature excursions that would otherwise follow. It is frequently employed in industrial reactors and, to model such systems, one must often resort to two-dimensional models of the reactor that allow the concentration and temperature to vary in both the radial and axial directions. In the analysis of such systems, we make incremental calculations across the diameter of a given longitudinal segment of the packed bed reactor, and then proceed to repeat the process for successive longitudinal increments. 

Two segments of the some fixed bed reactor were used, with dehydration of the reactional medium on molecular sieve between each of them. With oleic acid, and an excess of 3 moles of glycerol per mole of acid, the yield was 44.7 % (molar) of monoolein after 2 hours. At the same time, only 2 % of di-olein were obtained (Fig. 6.). 

B. Postcolumn Derivatization Three types of reactors for postcolumn derivatization are used, depending on reaction kinetics. Straight, coiled, and knitted open-tubular reactors are used for fast reactions, whereas packed-bed reactors are used for intermediate kinetics. Segmented-stream reactors are used for slow reactions. The simplest reactors are the open-tubular reactors a T connector is the most common. Pickering44 has described the performance requirements for instrumental components of HPLC postcolumn systems. 

The approximately 40% of the world s ethylbenzene capacity that still uses A1C13 is testimony to the efficiency and economy of this process. To capture this segment of the industry, zeolite catalysts that operate at close to the same very low benzene to ethylene ratios that make the A1C13 process economically attractive will have to be developed. Heat management in fixed bed reactors becomes a design concern at the low benzene to ethylene ratios that characterize the A1C13 process. Hence, process and catalyst innovations will have to evolve concurrently to achieve the goal of low benzene to ethylene ratios. 

In a vertically-segmented bed, the three phases can be transported without plugging the reactor. 

The cracking catalyst was selected as a bed material due to its ideal fluidizing properties and not for its catalytic properties. The nitrogen gas was preheated to furnace temperature and was fed to the reactor through an inlet on the bottom segment. The reactor was heated by a tubular Lindberg furnace and the temperature was controlled by a thermocouple feedback mechanism connected to the oven control unit. 

Recently, Tadepalli et al. [124] investigated the catalytic hydrogenation of o-nitroanisole in a microstructured packed-bed reactor. The reactor had an inner diameter of 0.775 mm and was filled with a Pd/zeolite catalyst with a particle diameter in the range of 45-75 and 75-150 pm. The length of the catalyst bed could be varied between 60 and 80 mm. The authors observed segmented gas-liquid flow. Further details of the hydrodynamics were not provided. 

Three-phase reactions comprise gas-liquid-solid and gas-liquid-liquid reactions. Gas-liquid reactions using solid catalysts represent a very important class of reactions. Conventionally, they are carried out in slurry reactors, (bubble columns, stirred tanks), fluidized beds, fixed bed reactors (trickle beds with cocurrent downflow or cocurrent upflow, segmented bed, and countercurrent gas-liquid arrangements) and structured (catalytic wall) reactors. 

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