Dehydrogenation reactor conditions

The vapor-phase catalytic dehydrogenation of ethanol to acetaldehyde involves the diffusion of ethanol to the catalyst surface where it reacts to produce acetaldehyde and hydrogen. Under typical reactor conditions (temperature = 548 K, pressure = 101.3 kPa) the binary diffusivities of the three binary pairs encountered are... 

Suppose it were possible to operate an ethyl benzene-dehydrogenation reactor under approximately isothermal conditions. If the temperature is 650°C, prepare a curve for conversion vs catalyst-bed depth which extends to the... 

Gas-phase reactions are usually performed with a series of fixed bed adiabatic reactors with re-heating between each catalytic bed. Liquid-phase reactions are usually performed in a slurry reactor with a circulating inert gas. The new trends in dehydrogenation reactors and conditions are membrane reactors [12], wall reactors [13], reactions performed in supercritical water [14], and oxidative dehydrogenation [11],... 

In the Monsanto/Lummus Crest process (Figure 10-3), fresh ethylbenzene with recycled unconverted ethylbenzene are mixed with superheated steam. The steam acts as a heating medium and as a diluent. The endothermic reaction is carried out in multiple radial bed reactors filled with proprietary catalysts. Radial beds minimize pressure drops across the reactor. A simulation and optimization of styrene plant based on the Lummus Monsanto process has been done by Sundaram et al. Yields could be predicted, and with the help of an optimizer, the best operating conditions can be found. Figure 10-4 shows the effect of steam-to-EB ratio, temperature, and pressure on the equilibrium conversion of ethylbenzene. Alternative routes for producing styrene have been sought. One approach is to dimerize butadiene to 4-vinyl-1-cyclohexene, followed by catalytic dehydrogenation to styrene ... 

According to this scheme, the catalyst serves primarily to promote dehydrogenation. Cyclization of the hexatriene was shown years ago (JJ.) to occur thermally in the gas phase at temperatures well below these dehydrocyclization conditions. Thus, the overall reaction is projected to be the combination of several catalytic dehydrogenation steps and a non-catalytic cyclization step. This projection implies that the design of the catalytic reactor may be important in order to optimize the ratio of void space for cyclization and catalyst space for dehydrogenation. 

One of the most studied applications of Catalytic Membrane Reactors (CMRs) is the dehydrogenation of alkanes. For this reaction, in conventional reactors and under classical conditions, the conversion is controlled by thermodynamics and high temperatures are required leading to a rapid catalyst deactivation and expensive operative costs In a CMR, the selective removal of hydrogen from the reaction zone through a permselective membrane will favour the conversion and then allow higher olefin yields when compared to conventional (nonmembrane) reactors [1-3]... 

In the isobutane dehydrogenation the catalytic membrane reactor allows a conversion which is twice the one observed in a conventional reactor operating under similar feed, catalyst and temperature conditions (and for which the performance corresponds to the one calculated from thermodynamics) [9]. 

A piston-flow-type reactor for dehydrogenation in continuous mode under superheated liquid-film conditions. 

The dehydrogenation of ethane (A) to ethene (B) is conducted in a 0.5-m3 PFR. The reaction is first-order with respect to A, with a rate constant of 15.2 min-1 at 725°C. The feed contains pure ethane at 725°C, 400 kPa, and a flow rate of 1. 0 kmol min-1. Compare the conversion predicted if isothermal, isobaric conditions are assumed with that if the pressure drop is accounted for with isothermal flow. The diameter of the reactor tube is 0.076 m, and the viscosity of the gas is 2.5 X 10-5 Pa s. 

Figure 1. Propane oxidative dehydrogenation to propylene on VSil545. Exp. conditions flow reactor tests with 2.8% C3, 8.4% O2 in helium. 4.2 g of catalyst with a total flow rate of 3.1 L/h (STP conditions).

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