Batch compounders, small-scale

Continuous processing is useful for reactions that need rapid heat transfer [4], for preparing unstable compounds, and for reactions in which physical effects are localized. When safety or stability is a major concern, continuous processing has advantages over batch processing in that only a small portion of the batch is subjected to reaction conditions at any moment. Following is a discussion of some large-scale and small-scale applications. 

Enantiomerically pure compounds will be used above all as pharmaceuticals and vitamins [4], as agrochemicals [5], and as flavors and fragrances [6]. Pharmaceuticals and agrochemicals usually are multifunctional molecules that are produced via multistep syntheses. Compared to basic chemicals, they are relatively small scale products with short product lives, produced in multipurpose batch equipment. The time for development of the production process is often very short since time to market affects the profitability of the product. 

Small-scale batch compounders are particularly suitable for fundamental research as good mixing results can be obtained with small material amounts. Furthermore, the simple systems are easy to clean. Altogether, a broad screening of mixtures and processing... 

Based on an evaluation of the physicochemical properties of the active compound, several initial formulations (generally, four to six) are selected and screened in this step (Dobry et al. 2009). A small-scale spray dryer designed for maximizing yields from SDD batches of less than 100 mg is used. This dryer is not designed to replicate optimized bulk powder properties (e.g., particle size, density) of larger scale spray dryers, but rather is used to guide formulation decisions based on physicochemical properties and fast, efficient formulation-screening studies. 

Reduction of nitro compounds is accomplished by (1) catalytic hydrogenation, (2) iron reduction (Bechamp), (3) sulfide reduction, or (4) zinc reduction in an alkaline medium. Generally, when the reaction is carried out on a large scale, the catalytic procedure is best. For small-scale batch operations, chemical reduction is preferred. 

Commercial-scale batch reactors are generally used for small-lot or specialty items. This includes chemicals such as paints, dyes, and pharmaceuticals. Batch reactors are very simple and flexible. Vessels used to make one compound can be washed and reused to make other products. The ease of cleaning and maintaining batch reactors along with low capital investment and low instrumental costs... 

The vessel used for the compounding may be different during development simply because of batch size. Compatibility with these different materials is important to consider in preparation for scale-up. Bench-scale studies and small clinical batches may be compounded in glass Erlenmeyer flasks or glass carboys. Commercial-scale manufacturing would typically use larger stainless steel tanks. Compatibility with the different materials that the product comes into contact... 

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