Reactors packed catalytic

Design of Packed Catalytic Reactors John Beek... 

Fig. 6. Examples of types of meshes developed to resolve laminar flow around particles (a) Chimera grid. Reprinted, with permission, from the Annual Review of Fluid Mechanics, Volume 31 1999 by Annual Reviews www.annualreviews.org (b) Unstructured grid with layers of prismatic cells on particle surfaces. Reprinted from Chemical Engineering Science, Vol. 56, Calis et al., CFD Modeling and Experimental Validation of Pressure Drop and Flow Profile in a Novel Structured Catalytic Reactor Packing, pp. 1713-1720, Copyright (2001), with permission from Elsevier.

See also Packed catalytic tubular reactors Ca,surface evaluation, 25 276-279 methodology for, 25 270-309 nomenclature related to, 25 316-321 species concentrations in the bulk gas phase, 25 272-273... 

Ideal isothermal packed catalytic tubular reactors, 25 286-287 Ideal isothermal tubular reactors,... 

Packed-bed reactors, 21 333, 352, 354 Packed beds, 25 718 Packed catalytic tubular reactor design with external mass transfer resistance, 25 293-298 nonideal, 25 295... 

Tubular reactor, 14 722, 20 216-217, 25 269. See also Packed catalytic tubular reactors... 

Nondek et al. (46) reported an innovative approach to the analysis of N-methylcarbamates in river water using postcolumn reaction detection. Separation of the underivatized N-methylcarbamates was carried out on a reversed-phase column hooked directly to a bed reactor packed with Aminex A-28, a tetraalkylammonium anion-exchange resin. The packed bed catalytically base-hydrolyzed the carbamates and... 

The catalytic activities for pyridine hydrogenation (HDN) were evaluated at 4.5MPa in a fixed bed reactor packed with 30ml of catalyst. The catalyst first were sulfided with a H2S/H2 (92/8) mixture gas at flow rate of 60 ml/min at 300°C for 3 hr at 4.5Mpa. After cooling down to 270 °C, the mixture of pyridine and Hexane was introduced into reactor, at constant pressure (4.5MPa). The reaction products were analyzed by gas chromatography. 

The starting point of a number of theoretical studies of packed catalytic reactors, where an exothermic reaction is carried out, is an analysis of heat and mass transfer in a single porous catalyst since such system is obviously more conductive to reasonable, analytical or numerical treatment. As can be expected the mutual interaction of transport effects and chemical kinetics may give rise to multiple steady states and oscillatory behavior as well. Research on multiplicity in catalysis has been strongly influenced by the classic paper by Weisz and Hicks (5) predicting occurrence of multiple steady states caused by intrapellet heat and mass intrusions alone. The literature abounds with theoretical analysis of various aspects of this phenomenon however, there is a dearth of reported experiments in this area. Later the possiblity of oscillatory activity has been reported (6). 

In a chemical packed-bed reactor in which a highly exothermic reaction is taking place conditions may be encountered under which, for a given set of input conditions (feed rate, temperature, concentration), the exit conversion is either high or low. To the experimental study of conditions connected with the existence of multiple steady states in packed catalytic reactors has not been paid as much attention in the past as to the study of... 

In this paragraph, based on experimental observations, we are going to review a number of observed facts which may help to elucidate the lows governing the occurrence of multiple steady states in tubular packed catalytic reactors. 

Fixed-bed catalytic reactors and reactive distillation columns are widely used in many industrial processes. Recently, structured packing (e.g., monoliths, katapak, mella-pak etc.) has been suggested for various chemical processes [1-4,14].One of the major challenges in the design and operation of reactors with structured packing is the prevention of liquid flow maldistribution, which could cause portions of the bed to be incompletely wetted. Such maldistribution, when it occurs, causes severe under-performance of reactors or catalytic distillation columns. It also can lead to hot spot formation, reactor runaway in exothermic reactions, decreased selectivity to desired products, in addition to the general underutilization of the catalyst bed. 

Attempts were therefore made to catalytically destroy H 0 by incorporating a small packed bed reactor immediately after the D.S. ana before the introduction of SOD. We have previously used microsized reactors packed with granular MnO (18.21.231 for the catalytic decomposition of H2O2. Experiments in the flow injection mode showed that using a large amount of MnO (ca. 25 mg) in the reactor resulted in not only decomposition of H 02 but also the oxidation of more than half of the collected S(IV). Reducing the... 

The packed bed reactor is used to contact fluids with solids. It is one of the most widely used industrial reactors and may or may not be catalytic. The bed is usually a column with the actual dimensions influenced by temperature and pressure drop in addition to the reaction kinetics. Heat limitations may require a small diameter tube, in which case total through-put requirements are maintained by the use of multiple tubes. This reduces the effect of hot spots in the reactor. For catalytic packed beds, regeneration is a problem for continuous operation. If a catalyst with a short life is required, then shifting between two columns may be necessary to maintain continuous operation. 

Industrial reactors for catalytic incineration of VOCs contain ceramic or another inert packing material on the boundaries of the catalyst bed [9, 26]. In such reactors, the temperature after the inert ceramic packing can be estimated by the almost linear expression... 

More complex reactors, like packed-bed reactors or catalytic monoliths, consist of many physically separated scales, with complex nonlinear interactions between the processes occurring at these scales. Figure 3 illustrates scale separation in a packed-bed reactor. The four length (and time) scales present in the system are the reactor, catalyst particle, pore scale, and molecular scale. The typical orders of magnitude of these four length scales are as follows reactor, lm catalyst particle, 10 2m (1cm) macropore scale, 1pm (10 6m) micro-pore/molecular scale, 10 A (10 9m). The corresponding time scales also vary widely. While the residence time in the reactor varies between 1 and 1000 s, the intraparticle diffusion time is of the order of 0.1s and is 10 5s inside the pores. The time scale associated with molecular phenomenon like adsorption is typically less than a microsecond and could be as small as a nanosecond. 

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