Intermediate-scale chemicals

Switching from Batch to Continuous Processing for Fine and Intermediate-Scale Chemicals Manufacture... 

The former may be considered the true fine chemical while the latter may conveniently be termed intermediate-scale chemicals commodity chemicals produced at a relatively small scale. This crude division starts to indicate the complexity of the economic drivers for B2C that is discussed later. First, however, progress in making the switch is reviewed and the essential elements of plant design structures and costs are briefly introduced. 

Cost of Fine and Intermediate-Scale Chemical Plants... 

Scale- Up of Electrochemical Reactors. The intermediate scale of the pilot plant is frequendy used in the scale-up of an electrochemical reactor or process to full scale. Dimensional analysis (qv) has been used in chemical engineering scale-up to simplify and generalize a multivariant system, and may be appHed to electrochemical systems, but has shown limitations. It is best used in conjunction with mathematical models. Scale-up often involves seeking a few critical parameters. Eor electrochemical cells, these parameters are generally current distribution and cell resistance. The characteristics of electrolytic process scale-up have been described (63—65). 

C-3 synthons are important in the manufacture of a number of products. These intermediates include (R) and f -glycidyl derivatives. Small scale chemical synthesis from D or L-serines and other raw materials has been carried out, but all these routes have problems, such as the use of expensive substrates or production of polluting wastes. Therefore various biocatalytic methods for producing enantiopure glycidyl butanoate have been attempted (EUerink et al, 1991). 

The next example originates from our own laboratory Two potential intermediates for the angiotensin-converting enzyme inhibitor benazepril can be synthesized using cinchona modified noble metal catalysts (3). While the hydrogenation of the a-ketoester has been developed and scaled-up into a production process (10-200 kg scale, chemical yield >98%, ee 79-82%), the novel enantioselective hydrodechlorination reaction (see Section in) could be a potential alternative to the established synthesis where the racemic a-bromobenzazepinon is used [75]. At the moment both selectivity and productivity of the catalyst are too low and substitution reactions occur less readily with the chloro analog. 

Vaughan, L. M. R. W. McMullen "Intermediate-scale aerosol cloud travel and diffusion from low-level aerial line releases." Technical Report No. 97, U. S. Army Chemical Corps Contract No. DA-42-007-CML-543, 1963. 

The use of silicon-based antifoams is common in industry (van Bonarius et al., 1993). Flowever, they should be used with care, since these substances can be toxic to the cell above certain concentrations. Furthermore, chemical antifoams can pose problems for the chromatographic purification of the product. Foam traps, which are devices mounted in the upper part of bioreactors to break the foam, have been used successfully at small and intermediate scales, but are not widely used on a large scale. On the other hand, low aeration rates using pure oxygen effectively lead to a significant decrease or even complete elimination of foam, but may result in CO2 accumulation in the medium, which is harmful to the cells (Gray et al., 1996). 

Generally, it is rarely possible to satisfy all of the various similarity criteria in scale-up, especially those related to chemical and thermal dimensionless groups. An alternative solution is to determine the effect of each group and perform intermediate scale experiments to determine the effect of the critical groups. 

Figure 1.1.17 The solar refinery as the conceptual contribution of chemistry by chemical energy conversion to the sustainable use of renewable energy. The upstream part (hydrogen generation) and the downstream parts need not to be colocalized in a practical realization. CSP stands for concentrated solar power. Green boxes indicate solar fuel products blue boxes stand for intermediate platform chemicals. The red arrows indicate flows of solar hydrogen to a storage and transport system for large-scale applications. The blue arrows show the major application lines for chemical production of solar fuels. The scheme also indicates the role of fertilizers from ammonia required in sustained use of biomass for energetic applications.

On an industrial scale, resolution of racemates is still in many cases the preferred way of producing enantiomerically pure compounds. If chiral-pool compounds are not available as optically active starting materials, a cost comparison of asymmetric and resolution processes often attributes advantages to the latter. Among the top 15 optically active pharmaceutical drugs and their intermediates, a chemical asymmetric process could be established only in the case of naproxen. For all others, diastereomeric and biocatalytic resolution are the methods, apart from fermentation, of creating optically pure compounds. 

The epoxidation of olefins plays an important role in the industrial production of several commodity compounds, as well as in the synthesis of many intermediates, fine chemicals, and pharmaceuticals. The scale of production ranges from millions of tons per year to a few grams per year. The diversity of catalysts is large and encompasses all the known categories of catalyst type homogeneous, heterogeneous, and biological. 

There are areas of chemistry where it is difficult or impossible to obtain experimental results. A good example of this is the determination of the nature of reaction intermediates in chemical kinetics. In favourable cases, reaction intermediates can be studied spectroscopically using specialized techniques that allow observations on a very short time-scale of the order 10 9-10 15 seconds. 

Safety is a very important component of scale-up activities, especially at intermediate scale such as kilo-laboratory. This critical topic is covered in numerous textbooks and publications for example, Crowl, D. A. and Louvar, J. F. Chemical Process Safety Fundamentals and Applications, Prentice Hall, Upper Saddle River, NJ, 1990. 

However, transport capacities of ships and barges are generally larger than train capacities. Hence, transport cost rates per volume and distance unit are typically higher for rail transports. Since most large-scaled chemical production sites have waterway access, raw materials are typically supphed via ship transports, but intermediate and minor basic chemicals are often transported via rail e.g. because the distribution structure is disperse and/or not all customers/suppliers have waterway access. 

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