Dehydrogenation reactions reactors

Membrane Reactor. Another area of current activity uses membranes in ethane dehydrogenation to shift the ethane to ethylene equiUbrium. The use of membranes is not new, and has been used in many separation processes. However, these membranes, which are mostly biomembranes, are not suitable for dehydrogenation reactions that require high temperatures. Technology has improved to produce ceramic and other inorganic (90) membranes that can be used at high temperatures (600°C and above). In addition, the suitable catalysts can be coated without blocking the pores of the membrane. Therefore, catalyst-coated membranes can be used for reaction and separation. 

The HVCH ratio is an indicator of dehydrogenation reactions. However, the ratio is sensitive to the reactor temperature and the type of catalyst. A better indicator of nickel activity is the volume of... 

Besser, R. S., Ouyang, X., Suranga-LiKAR, H., Hydrocarbon hydrogenation and dehydrogenation reactions in micro-fabricated catalytic reactors, Chem. Eng. Sci. 58 (2003) 19-26. 

This overview is organized into several major sections. The first is a description of the cluster source, reactor, and the general mechanisms used to describe the reaction kinetics that will be studied. The next two sections describe the relatively simple reactions of hydrogen, nitrogen, methane, carbon monoxide, and oxygen reactions with a variety of metal clusters, followed by the more complicated dehydrogenation reactions of hydrocarbons with platinum clusters. The last section develops a model to rationalize the observed chemical behavior and describes several predictions that can be made from the model. 

Senkan et al. [34] introduced REMPI analysis technique as a Stage I tool and exemplified its applicability with the example of a dehydrogenation reaction. The principle of this analysis method is based on sample ionization via laser light and subsequent detection of the ionized reactor effluent at dedicated electrodes at the reactor exit. Owing to a number of limitations connected with the analysis technique, it has to be considered of restricted applicability. 

There are certainly quite significant advantages that membrane reactor processes provide as compared to conventional reaction processes. The reactor can be divided by the membrane into two individual compartments. The bulk phases of the various components or process streams are separated. This is of importance for partial oxidation or oxidative dehydrogenation reactions, where undesirable consecutive gas phase reactions leading to total oxidation occur very often. By separating the process stream and the oxidant. 

INORGANIC MEMBRANE REACTORS TO ENHANCE PRODUCTIVITY 187 Table 7.3. Membrane Reactor Studies on Dehydrogenation Reactions... 

Table 7A Summarized Results on Inorganic Membrane Reactors Used for Dehydrogenation Reactions... 

Dehydrogenation reaction of ethylbenzene was chosen as a test reaction for V205/AIP04-5. The reaction was carried out on a flow reactor equipped syringe pump, and gas feeding system. The reactant was diluted with nitrogen. The products were analyzed by on-lined gaschromatograph (HP 5890) with 10% Carbowax 20M, 3m X 1.8" SS column. 

The use of steam has a number of other advantages in the styrene process. The most important of these is that it acts as a source of internal heat supply so that the reactor can be operated adiabatic-ally. The dehydrogenation reaction is strongly endothermic, the heat of reaction at 560°C being (- AH) - 125,000 kJ/kmoL It is instructive to look closely at the conditions which were originally worked out for this process (Fig. 1.7). Most of the.steam, 90 per cent of the total used, is heated separately from the ethylbenzene stream, and to a higher temperature (7I0SC) than is required at the inlet to the... 

The dehydrogenation of iso-butane was carried out in a recirculating batch reactor.12 Reaction products were analyzed by gas chromatography using flame ionization. The vanadium and vanadium carbide powder materials were purchased from Aldrich Chemical Co. Their bulk compositions were confirmed by the X-ray diffraction measurements. Prior to the dehydrogenation reactions, these powder materials were heated for 1 h at 900 K in pure H2 at a flow rate of 200 cm3 per minute. 

In the process, ethylbenzene is dehydrogenated to styrene in a fixed-bed catalytic reactor. The feed stream is preheated and mixed with superheated steam before being injected into the reactor at a temperature above 490°C. The steam serves as a dilutant and decokes the catalyst, thereby extending its life. The steam also supplies the necessary heat for the endothermic dehydrogenation reaction. For our model we have chosen six reactions to represent the plant data. 

The second type of membrane reactor, illustrated in Figure 13.16(b), uses the separative properties of a membrane. In this example, the membrane shifts the equilibrium of a chemical reaction by selectively removing one of the components of the reaction. The example illustrated is the important dehydrogenation reaction converting n-butane to butadiene and hydrogen... 

Currently, several types of membrane reactors are under investigation for dehydrogenation reactions, for example, the dehydrogenation of propane to propene [122,123], or of ethylbenzene to styrene [124], In addition, the dehydrogenation of H2S has been studied in membrane reactors [125],... 

A comprehensive study on coke deposition in trickle-bed reactors during severe hydroprocessing of vacuum gas oil has been carried out. On the basis of results obtained with different catalysts on the one hand, and analytical and catalytic characterisation of the coke deposits on the other, it is argued that coke is formed via two parallel routes, viz. (i) thermal condensation reactions of aromatic moieties and (ii) catalytic dehydrogenation reactions. The catalyst composition has a large impact on the amount of catalytic coke whilst physical effects (vapour-liquid equilibria, VLE) predominate in determining the extent of thermal coke formation. The effect of VLE is related to the concentration of heavy coke precursors in the liquid phase under conditions which promote oil evaporation such as elevated temperatures. A quantitative model which describes inter alinea the distinct maximum of coke deposited as a function of temperature is presented. 

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