Reaction tube wall catalyzed

On the contrary, when 87a was reacted with ethyl propynoate, isocoumarins 262 were obtained. In this case the Diels-Alder cycloadduct 261 reacted as diene with another ethyl propynoate molecule. Tricyclic pyran underwent oxygen bridge opening followed by ethanol elimination presumably catalyzed by acidic Pyrex reaction tube walls [75, 78, 151]. Reaction of 110 with ethyl propynoate yielded complex mixture of unidentified products [78]. 

This study was carried out to simulate the 3D temperature field in and around the large steam reforming catalyst particles at the wall of a reformer tube, under various conditions (Dixon et al., 2003). We wanted to use this study with spherical catalyst particles to find an approach to incorporate thermal effects into the pellets, within reasonable constraints of computational effort and realism. This was our first look at the problem of bringing together CFD and heterogeneously catalyzed reactions. To have included species transport in the particles would have required a 3D diffusion-reaction model for each particle to be included in the flow simulation. The computational burden of this approach would have been very large. For the purposes of this first study, therefore, species transport was not incorporated in the model, and diffusion and mass transfer limitations were not directly represented. 

Any detectable effect on the reaction or behavior of a particular system by the interior wall of the container or reaction vessel. Because proteins can form high-affinity complexes with glass and plastic surfaces, one must exercise caution in the choice of reaction kinetic conditions. Wall effects can be discerned if one determines catalytic activity under different conditions that minimize or maximize contact of the solution with the container. In principle, an enzyme-catalyzed reaction should proceed at the same rate if placed in a capillary or a culture tube however, contact with the wall is maximized in a capillary, and wall effects should be more prominent. Some investigators add bovine serum albumin to prevent adsorption of their enzyme onto the container s walls. 

We may first divide tubular reactors into those designed for homogeneous reactions, and therefore basically just an empty tube, and those designed for a heterogeneously catalyzed reaction, and hence to be packed with a catalyst. Both types can of course be operated adiabatically, and it was the simplest model of these that we discussed in the last chapter. If the temperature of the reactor is to be controlled this is through the wall, and the associated problems of heat transfer now arise. These include transfer at the wall and subsequent radial diffusion across the flowing reactants. In the empty tubular reactor there may be considerable variations in flow rate across the tube. For example, in the slow laminar flow the fluid... 

S. Katz, Chemical Reactions Catalyzed on a Tube Wall, Chem. Eng. 

The Tube Wall Catalyzed Reaction Assuming incompressible flow of a Newtonian fluid and no contributions in the azimuthal direction a mass balance for a differential element in the entrance region of the tube yields the following steady state dimensionless differential equation ... 

A sample that contains H2S and O2 in concentrations of interest to us should never be obtained in a steel sample bomb. The Ff2S and O2 will react to form water and solid sulfur. The metal walls of the steel bomb will catalyze the reaction. I use a mountain-bike tire inner tube which is pumped up with a small rubber handpump to catch such samples. The sample must still be analyzed promptly to minimize the disappearance of H S and Oi. 

The tests described under (i) and (2), which are based on the production of alkali sulfide, cannot be applied successfully to volatile organic compounds. If, however, sulfur-bearing materials are pyrolysed in small capillary tubes, whose inner walls have been silvered, the action of the hot decomposition products yields silver sulfide. Since the latter catalyzes the iodine-azide reaction just as soluble sulfides do, an extremely sensitive test for sulfur in easily volatile organic compounds becomes possible. 

Results When we assume that the catalyzed wall reaction takes place homogeneously and can be described as being first order in the hydrocarbon concentration, while the gas flow through the tubes is supposed to be ideal plug flow, an impression of the magnitude of the rate constant can be obtained by using the relation c... 

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