Continuous flow reactors advantages

Continuous flow reactors are almost invariably preferred to batch reactors when the processing capacity required is large. Although the capital investment requirements will be higher, the operating costs per unit of product will be lower for continuous operation than for batch reaction. The advantages of continuous operation are that it ... 

The reactor has facilitated a diverse range of synthetic reactions at temperatures up to 200 °C and 1.4 Pa. The temperature measurements taken at the microwave zone exit indicate that the maximum temperature is attained, but they give insufficient information about thermal gradients within the coil. Accurate kinetic data for studied reactions are thus difficult to obtain. This problem has recently been avoided by using fiber optic thermometer. The advantage of continuous-flow reactor is the possibility to process large amounts of starting material in a small volume reactor (50 mL, flow rate 1 L hr1). A similar reactor, but of smaller volume (10 mL), has been described by Chen et al. [117]. 

Other methods involve the use of continuous-flow reactors, and in certain cases, the rate is measured directly rather than indirectly. One advantage of a flow method is that a steady-state can usually be established, and this is an advantage for relatively fast reactions, and for continuous monitoring of properties. A disadvantage is that it may require relatively large quantities of materials. Furthermore, the flow rate must be accurately measured, and the flow pattern properly characterized. 

In this chapter, we first consider uses of batch reactors, and their advantages and disadvantages compared with continuous-flow reactors. After considering what the essential features of process design are, we then develop design or performance equations for both isothermal and nonisothermal operation. The latter requires the energy balance, in addition to the material balance. We continue with an example of optimal performance of a batch reactor, and conclude with a discussion of semibatch and semi-continuous operation. We restrict attention to simple systems, deferring treatment of complex systems to Chapter 18. 

One of the major advantages of flow reaetors is the short residence time of reaetions in the reaetor. This allows seleetive reaetions to pass through the system and out again before any side reaetion ean take plaee. This is very well illustrated in the synthesis of dithioketal and -aeetals, where the seleetive reaetion resulted in superior conversion using eontinuous flow when eompared to bateh synthesis. A dramatic increase of yield was noted in the hydrogenation reaetion performed by Kobayashi et al. when a residence time of less than 1 min was used. The yield inereased from 1% to 97% using the continuous-flow reactor. 

With numerous researchers investigating the advantages associated with thermally or biocatalytically controlled asymmetric syntheses, some of which have been performed in continuous flow reactors, few have considered the prospects of photochemical asymmetric synthesis, an idea... 

As indicated in the introduction of Section 2.2.2, continuous flow reactors (generally fixed bed reactors) are not frequently used in the investigation of the liquid phase zeolite catalysed synthesis of Fine Chemicals. However, fixed bed reactors present some significant advantages on batch reactors ... 

Along with the inclusion of heterogeneous metal catalysts in continuous flow reactors, numerous authors have evaluated the advantages associated with the incorporation of acid and base catalysts in these reaction systems, using a range of packed beds, monoliths, and wall-coated reactors. 

With numerous researchers investigating the advantages associated with the thermal or biocatalytic control of asymmetric reactions, Ichimura and co-workers [89] considered the potential of photochemical asymmetric syntheses performed in continuous flow reactors. To investigate the hypothesis, the authors employed the asymmetric photochemical addition of MeOH to (R)-( + )-(Z)-limonene (159) as a model reaction, comparing three quartz micro reactors, with a standard laboratory cell as a means of highlighting the synthetic potential of this approach. 

Since the 1940s, fluidized beds have provided a means of carrying out solid-catalyzed gas-phase reactions based on some significant features and advantages relative to competing packed-bed continuous flow reactors. In particular,... 

In 2011, Goossen, Underwood, and coworkers [36] developed a practical protocol that allowed performing the decarboxylative cross-coupling reactions in continuous flow reactors. The advantage of this method was that the reaction time was reduced and the formation of side products was minimized. 

The majority of thermal polymerizations are carried out as a batch process, which requires a heat-up and a cool down stage. Typical conditions are 250—300°C for 0.5—4 h in an oxygen-free atmosphere (typically nitrogen) at approximately 1.4 MPa (200 psi). A continuous thermal polymerization has been reported which utilizes a tubular flow reactor having three temperature zones and recycle capabiHty (62). The advantages of this process are reduced residence time, increased production, and improved molecular weight control. Molecular weight may be controlled with temperature, residence time, feed composition, and polymerizate recycle. 

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