Continuous reactors advantages

Reactors may be operated batchwise or continuously, e.g. in tubular, tubes in shell (with or without internal catalyst beds), continuous stirred tank or fluidized bed reactors. Continuous reactors generally offer the advantage of low materials inventory and reduced variation of operating parameters. Recycle of reactants, products or of diluent is often used with continuous reactors, possibly in conjunction with an external heat exchanger. 

Figure 4-8 shows a continuous reactor used for bubbling gaseous reactants through a liquid catalyst. This reactor allows for close temperature control. The fixed-bed (packed-bed) reactor is a tubular reactor that is packed with solid catalyst particles. The catalyst of the reactor may be placed in one or more fixed beds (i.e., layers across the reactor) or may be distributed in a series of parallel long tubes. The latter type of fixed-bed reactor is widely used in industry (e.g., ammonia synthesis) and offers several advantages over other forms of fixed beds. 

Although batch reactors offer some advantages that make them particularly attractive in some industry sectors, most bulk chemical production utilizes some form of continuous reactor, owing to their overall greater efficiency. 

Thermomorphic solvent mixtures have been tested for hydroformylation of 1-octene and 1-dodecene to determine the ease of product recovery and catalyst recycling. Using both batch and continuous reactors, we demonstrated the efficacy of a biphasic, thermomorphic, system that had the following advantages ... 

Batch operation requires a larger inventory than the corresponding continuous reactor. Thus, there may be a safety incentive to change from batch to continuous operation. Alternatively, the batch operation can be changed to semibatch in which one (or more) of the reactants is added over a period. The advantage of semibatch operation is that the feed can be switched off in the event of a temperature (or pressure) excursion. This minimizes the chemical energy stored up for a subsequent exotherm. 

The advantages provided by the continuous reactor prompted us to explore CCTP in a reactor with two CSTRs connected in series [11]. This reaction scheme depicted in Scheme 6 provides a highly flexible process for production of a wide range of diblock OBC compositions. The block composition can easily be varied by changing the production rate in either reactor. The comonomer content of either block can also be independently tailored by varying the feed compositions because the process operates in two independent reactors. This CCTP scheme also produces multiple chains per catalyst, an advantage over stoichiometric living polymerization systems, but is necessarily stoichiometric in CSA. The reaction produces... 

This preparation and oleoyl chloride (p. 66) illustrate the use of the general form of a laboratory-sized continuous reactor.6 This device has many advantages over the commonly used flasks (batch procedure). In particular, the short time of exposure to heat results in a better quality of product, as shown by less color, fewer side reactions, and better melting point, often unchanged by recrystallization. Furthermore, the unlimited capacity, very short reaction time, and use of concentrated solutions permit a larger output with no increase in size of apparatus and less delay required for removal of solvents. 

We focus mainly on the advantages and disadvantages of semibatch reactors. A semicontinuous reactor may be treated in many cases as either a batch reactor or a continuous reactor, depending on the overall kinetics and/or the phase of interest. 

Corma and Renz6 developed an effective heterogeneous catalyst system. Incorporation of tin into a beta zeolite network (Sn-Beta) gave a catalyst that was used to convert citronellal 5 to racemic isopulegol (6, Equation (3)) with 85% diastereoselectivity. It was calculated that each metal site performed 11,500 reaction cycles. No leaching of the tin was detected. This catalyst system is advantageous over normal Lewis acids, since precautions against humidity are not required, and it is suitable for use in a fixed bed continuous reactor. 

The two catalyst components are rhodium and iodide, which can be added in many forms. A large excess of iodide may be present. Rhodium is present as the anionic species RhI2(CO)2. Typically the rhodium concentration is 10 mM and the iodide concentration is 1.5 M, of which 20% occurs in the form of salts. The temperature is about 180 °C and the pressure is 50 bar. The methyl iodide formation from methanol is almost complete, which makes the reaction rate also practically independent of the methanol concentration. In other words, at any conversion level (except for very low methanol levels) the production rate is the same. For a continuous reactor this has the advantage that it can be operated at a high conversion level. As a result the required separation of methanol, methyl acetate, methyl iodide, and rhodium iodide from the product acetic acid is much easier. 

In general, the fixed D-glucose isomerase systems have many advantages with respect to enzyme use, efficiency, ease of handling, and adaptability to continuous-reactor operation. Methods have been described that employ a continuously stirred tank-reactor provided with a semipermeable membrane through which the isomerized liquor, having the steady-state composition, is removed from the reaction medium at the same rate as fresh substrate is introduced into the reactor.47 The soluble enzyme is retained in the reaction zone, because it is held back by the semipermeable membrane, and fresh enzyme may be added as needed, to compensate for enzyme inactivation, to the reaction zone with the fresh substrate. 

Continuous emulsion polymerization processes are industrially important for the large-scale production of synthetic polymer latexes, and have been used particularly where the solid polymer is to be recovered by coagulating the polymer latex. St-Bu rubber latex was one of the earliest latex products manufactured using continuous emulsion polymerization processes consisting of a number of stirred-tank reactors in series (CSTRs). Since the 1940s, continuous emulsion polymerization processes have been developed for a variety of products and with different reactor configurations [328]. This is because these continuous reactor systems have several advantages, such as [329] ... 

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