Reactions byproduct

Multiple reactions also can occur with impurities that enter with the feed and undergo reaction. Again, such reactions should be minimized, but the most efiective means of dealing with byproduct reactions caused by feed impurities is not to alter reactor conditions but to introduce feed purification. 

In general terms, if the reaction to the desired product has a higher order than the byproduct reaction, use a batch or plug-flow reactor. If the reaction to the desired product has a lower order than the byproduct reaction, use a continuous well-mixed reactor. 

As far as the parallel byproduct reaction is concerned, for high selectivity, if... 

The series byproduct reaction requires a plug-flow reactor. Thus, for the mixed parallel and series system above, if... 

But what is the correct choice a well-mixed reactor. On the other hand, the byproduct series reaction calls for a plug-flow reactor. It would seem that, given this situation, some level of mixing between a plug-flow and a continuous well-mixed reactor will give the best... 

Increase the concentration of inerts if the BYPRODUCT reaction involves a decrease in the number of moles. 

Removal of the product as the reaction progresses is also effective in suppressing the series element of the byproduct reactions, providing the separation is straightforward. 

If the byproduct reaction is reversible and inerts are present, then changing the concentration of inerts if there is a change in the number of moles should be considered, as discussed above. Whether or not there is a change in the number of moles, recycling byproducts can suppress their formation if the bj iroduct-forming reaction is reversible. An example is in the production of ethylbenzene from benzene and ethylene ... 

To make an initial guess for the reactor conversion is again diflicult. The series nature of the byproduct reactions suggests that a value of 50 percent is probably as good as csm be suggested at this stage. 

Multiple reactions. For multiple reactions in which the byproduct is formed in parallel, the selectivity may increase or decrease as conversion increases. If the byproduct reaction is a higher order than the primary reaction, selectivity increases for increasing reactor conversion. In this case, the same initial setting as single reactions should be used. If the byproduct reaction of the parallel system is a... 

Although the flowsheet shown in Fig. 4.7a is very attractive, it is not practical. This would require careful control of the stoichiometric ratio of decane to chlorine, taking into account both the requirements of the primary and byproduct reactions. Even if it was possible to balance out the... 

Recycle waste byproducts to the reactor if byproduct reactions are reversible. 

Reactor temperature and pressure. If there is a significant difierence between the effect of temperature or pressure on primary and byproduct reactions, then temperature and pressure should be manipulated to improve selectivity and minimize the waste generated by byproduct formation. d. Catalysts. Catalysts cam have a major influence on selectivity. Changing the catalyst can change the relative influence on the primary and byproduct reactions. 

The crude phthalic anhydride is heated and held at 260 C to allow some byproduct reactions to go to completion. Purification is by continuous distillation in two columns. In the first column, maleic anhydride and benzoic and toluic acids are removed overhead. In the second column, pure phthalic anhydride is removed overhead. High boiling residues are removed from the bottom of the second column. 

Solution The byproduct reactions to avoid are all series in nature. This suggests that a mixed-flow reactor should not be used, rather either a batch or plug-flow reactor should be used. 

Although the flowsheet shown in Figure 13.7a is very attractive, it is not practical. This would require careful control of the stoichiometric ratio of decane to chlorine, taking into account both the requirements of the primary and byproduct reactions. Even if it were possible to balance out the reactants exactly, a small upset in process conditions would create an excess of either decane or chlorine and these would then appear as components in the reactor effluent. If these components appear in the reactor effluent of the flowsheet in Figure 13.7a, there are no separators to deal with their presence and no means of recycling unconverted raw materials. 

Decrease the concentration of inert material if the byproduct reaction is reversible and involves an increase in the number of moles. 

As well as characterizing complexes involved in the main catalyst cycles, spectroscopy has contributed to the measurement of the kinetics of these cycles and to byproduct reactions. The major catalyst species present under working conditions of the catalyst systems have been identified for all the systems. Individual reaction steps involving interconversion of catalyst complexes have been isolated and studied in model reactions. IR has been very important in these studies with metal carbonyl species, including the identification of Ru promoter species in MeOH carbonylation. 

A nucleophilic attack by 4.7 on CH3I produces 4.8 and I. Conversion of 4.8 to 4.9 is an example of a carbonyl insertion into a metal alkyl bond. Another CO group adds onto the 16-electron species 4.9 to give 4.10, which in turn reacts with I to eliminate acetyl iodide. Formation of acetic acid and recycling of water occur by reactions already discussed for the rhodium cycle. Apart from these basic reactions there are a few other reactions that lead to product and by-product formations. As shown in Fig. 4.4, both 4.9 and 4.10 react with water to give acetic acid. The hydrido cobalt carbonyl 4.11 produced in these reactions catalyzes Fischer-Tropsch-type reactions and the formation of byproducts. Reactions 4.6 and 4.7 ensure that there is equilibrium between 4.7 and 4.11. 

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