Catalytic plug flow reactors

After the rates have been determined at a series of reactant concentrations, the differential method of testing rate equations is applied. Smith [3] and Carberry [4] have adequately reviewed the designs of heterogeneous catalytic reactors. The following examples review design problems in a plug flow reactor with a homogeneous phase. 

It is not practical to stir all reaction systems, for example, bulk polymerizations, postpolymerization reactions, fixed-bed catalytic reactors, and plug-flow reactors. Although multipoint temperature sensing is often used as a key solution to determine a runaway in nonagitated vessels, the occurrence of hot spots may not always be detected. 

A plug flow reactor is packed with catalyst granules where the rate equation is r = kcCn per unit volume. The wall also is catalytic with rate equation rw = kwCn per unit area. Diffusion is appreciable only in the radial direction. Explain how to find the concentration axially and radially. 

Stoichacmetry and reaction equilibria. Homogeneous reactions kinetics. Mole balances batch, continuous-shn-ed tank and plug flow reactors. Collection and analysis of rate data. Catalytic reaction kinetics and isothermal catalytic radar desttpi. Diffusion effects. 

The trickle bed reactor allows for plug flow reactor assumptions even at extremely low liquid-flow rates. The trickle bed is classified as a continuous heterogeneous catalytic reactor. 

Plug flow reactors are often used to investigate heterogeneously catalysed reactions. Typically 0.1-10 g of catalyst with a pellet diameter smaller than 1 mm is loaded into a tube of 1 cm diameter and a few dm long. A central thermocouple well allows the measurement of the temperature inside the catalytic bed. 

The fluidized-bed reactor involves a rapid movement of the solid catalytic particles throughout the bed so that the operation can come close to one of uniform temperature throughout the reactor. The actual flow pattern for the operation of a fluidized bed is very complex and is between that for the ideal back-mix reactor and the ideal plug-flow reactor so that special methods for design may be required to approximate the real situation. 

Enzyme Assay Procedure. The catalytic potency of the immobilized g-galactosidase was determined in a plug flow reactor ( 9). Glucose liberated by the catalytic activity of 3-galactosi-dase on lactose was determined by the glucose oxidase-chromogen method (21 ) with some modifications. 

Figure 4.29 shows a block diagram of a reactor with manipulated inputs U. other measured inputs W, and unknowm or unmeasured inputs N. We may assume that this reactor is more complicated than a simple plug-flow reactor or a CSTR. It may be more along the lines of the fluidized catalytic cracker that we showed in Fig. 4.4. The reactor can be described by a set of nonlinear differential equations as we have previously demonstrated. This results in a set of dynamic state variables X The state vector is often of high dimension and we normally only measure a subset of all the states. Y is the vector of all measurements made on the system.

The simplicity and general utility of the Madon-Boudart criterion make it one of the most important experimental tests to confirm that kinetic data are free from artifacts. It can be used for heterogeneous catalytic reactions carried out in batch, continuous stirred tank, and tubular plug flow reactors. 

The use of monoliths as catalytic reactors focuses mainly on applications where low pressure drop is an important item. When compared to fixed beds, which seem a natural first choice for catalytic reactors, monoliths consist of straight channels in parallel with a rather small diameter, because of the requirement of a comparably large surface area. The resulting laminar flow, which is encountered under normal practical circumstances, does not show the kinetic energy losses that occur in fixed beds due to inertia forces at comparable fluid velocities. Despite the laminar flow, monolith reactors still may be approached as plug-flow reactors because of the considerable radial diffusion in the narrow channels [1]. 

The differences between the TBR and the MR originate from the differences in catalyst geometry, which affect catalyst load, internal and external mass transfer resistance, contact areas, as well as pressure drop. These effects have been analyzed by Edvinsson and Cybulski [ 14,26] via computer simulations based on relatively simple mathematical models of the MR and TBR. They considered catalytic consecutive hydrogenation reactions carried out in a plug-flow reactor with cocurrent downflow of both phases, operated isothermally in a pseudo-steady state all fluctuations were modeled by a corresponding time average ... 

Discuss the consequences of the nonstandard boundary conditions arising in the description of mass transfer in a plug-flow reactor with catalytically active walls. 

Catalytic reactions were carried out in an isothermal plug flow reactor at 673K. Products were collected during the run and the average conversion measured. Reaction times varied between 1 and 30 minutes. 99.45% pure 2M obtained froia Aldrich was used without further purification. The principal impurity was 3-Methylpentane (0.55%). Experimental procedures and analytical techniques were outlined elsewhere (7 8). 

Fig. 11.5. Formaldehyde yields in various reactors under similar experimental conditions. V, conventional plug-flow reactor , a PBMR using a Pd/AljCb dense composite membrane A, a PBMR using a mesoporous AI2O3 membrane , a CMR using a mesoporous AI2O3 membrane catalytically impregnated by a sol-gel technique. Reproduced from Deng and Wu [61] with permission.

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