Production of fine chemicals

Batchwise operated multipurpose plants are per defmitionem the vehicle for the production of fine chemicals. There are, however, a few examples of fine chemicals produced ia dedicated, coatiauous plants. These can be advantageous if the raw materials or products are gaseous or Hquid rather than soHd, if the reaction is strongly exothermic or endothermic or otherwise hazardous, and if the requirement for the product warrants a continued capacity utilization. Some fine chemicals produced by continuous processes are methyl 4-chloroacetoacetate [32807-28-6] C H CIO [32807-28-6], and malononittile [109-77-3] C2H2N2, made by Lonza dimethyl acetonedicarboxylate [1830-54-2] made by Ube and L-2-chloropropionic acid [107-94-8] C2H C102, produced by Zeneca. 

Growth appHcations for amyl alcohols appear to be shifting toward higher boiling esters as plasticizers, perfumes, fragrances, and production of fine chemicals. 

Benzaldehyde. Annual production of ben2aldehyde requires ca 6,500—10,000 t (2-3 x 10 gal) of toluene. It is produced mainly as by-product during oxidation of toluene to benzoic acid, but some is produced by hydrolysis of ben2al chloride. The main use of ben2aldehyde is as a chemical intermediate for production of fine chemicals used for food flavoring, pharmaceuticals, herbicides, and dyestuffs. 

The batch reactor is generally used in the production of fine chemicals. At the start of the process the reactor is filled with reactants, which gradually convert into products. As a consequence, the rate of reaction and the concentrations of all participants in the reaction vary with time. We will first discuss the kinetics of coupled reactions in the steady state regime. 

Here we shall consider a different concept, which has an interesting potential, particularly in liquid phase reactions used for the production of fine chemicals. The concept is schematically illustrated in Fig. 3. The modification of the metal catalysts is achieved by very small quantities (usually a sub-monolayer) of adsorbed auxiliaries (modifiers), which are either simply added to the reaction mixture (in-situ), or brought onto the catalyst surface in a... 

In recent years research of possible utility in the production of fine chemicals has increased substantially and in part consequent to government policy. This work has been too variegated to summarize briefly. A flurry of work in the hydrogenation of CO also originated in government policy. It led to the elaboration of our imderstanding of these reactions, but it is not clear that it led to major developments. 

In this chapter the potential of nanostructured metal systems in catalysis and the production of fine chemicals has been underlined. The crucial role of particle size in determining the activity and selectivity of the catalytic systems has been pointed out several examples of important reactions have been presented and the reaction conditions also described. Metal Vapor Synthesis has proved to be a powerful tool for the generation of catalytically active microclusters SMA and nanoparticles. SMA are unique homogeneous catalytic precursors and they can be very convenient starting materials for the gentle deposition of catalytically active metal nanoparticles of controlled size. 

Many standard reactions that are widely applied in the production of fine chemicals employ. strong mineral or Lewis acids, such as sulphuric acid and aluminium chloride, often in stoichiometric quantities. This generates waste streams containing large amounts of spent acid, which cannot easily be recovered and recycled. Replacement of these soluble mineral and Lewis acids by recyclable. solid acids, such as zeolites, acid clays, and related materials, would represent a major breakthrough, especially if they functioned in truly catalytic quantities. Consequently, the application of solid acids in fine chemicals synthesis is currently the focus of much attention (Downing et al., 1997). 

As mentioned earlier, a major cause of high costs in fine chemicals manufacturing is the complexity of the processes. Hence, the key to more economical processes is reduction of the number of unit operations by judicious process integration. This pertains to the successful integration of, for example, chemical and biocatalytic steps, or of reaction steps with (catalyst) separations. A recurring problem in the batch-wise production of fine chemicals is the (perceived) necessity for solvent switches from one reaction step to another or from the reaction to the product separation. Process simplification, e.g. by integration of reaction and separation steps into a single unit operation, will provide obvious economic and environmental benefits. Examples include catalytic distillation, and the use of (catalytic) membranes to facilitate separation of products from catalysts. 

This chapter focuses on heterogeneous catalysis, which is most important in fine chemicals production. Table 3.1 presents a number of examples of catalysis in fine chemistry. These examples are divided in heterogeneously catalysed processes and homogeneously catalysed processes. A detailed treatment of heterogeneously catalysed processes for the production of fine chemicals is also given in the book edited by Sheldon and van Bekkum (2001). 

Onken, U., Schmidt, E. and Weissenrieder, T. (1996) Enzymatic H202 decomposition in a three phase suspension, Ciba Geigy. International Conference on Biotechnology for Industrial Production of fine Chemicals, 93rd event of the EFB, Zermatt, Switzerland, 29.09.1996. 

Straathof AJ, Panke S, Schmid A (2002) The production of fine chemicals by biotransformations. Curr Opin Biotechnol 13 548-556... 

When examining more closely the impact that this technology had on the production of fine chemicals, the picture is even bleaker [4, 5], Even today, the majority of enantiopure chemicals (most of which are intermediates for drugs) is produced either by fermentation or by classical resolution - that is, the separation of diastereomeric salts. There are a number of reasons for this, which can be summarized as follows [6] ... 

The use of combinatorial and HTE methods in homogeneous hydrogenation has blossomed over the past five years. This has been fuelled first by the urgent need to identify useful catalysts for the production of fine chemicals, in particular enantiopure pharma intermediates. The second impetus came from academia, where many investigators realized that, with regard to enantioselective cat-... 

The various isomeric hexenoic acids are useful starting materials for the production of fine chemicals, and the stereoselective hydrogenation of sorbic acid has attracted considerable interest. It was shown recently that this reaction could be catalyzed by [Ru(CO)(Cp )(mtppts)] [CF3SO3] (Cp =//5-C5Me5) in a water -heptane biphasic mixture to yield tra s-3-hexenoic acid with up to 85% selectivity [39] (Scheme 38.3). Conversely, the use of [ RuC12(PR3)2 2] (R=CH2CH2CH2OH) as catalyst precursor led to the selective formation of 4-hexenoic acid [40]. 

The cost of the catalysts represents a major hurdle on the road to the industrial application of homogeneous catalysis, and in particular for the production of fine chemicals [1, 2], This is particularly true for chiral catalysts that are based on expensive metals, such as rhodium, iridium, ruthenium and palladium, and on chiral ligands that are prepared by lengthy total syntheses, which often makes them more expensive than the metals. In spite of this, the number of large-scale applications for these catalysts is growing. Clearly, these can only be economic if the substrate catalyst ratio (SCR) can be very high, often between 103 and 105. 

Preparative chromatographic processes are of increasing importance particularly in the production of fine chemicals. A mixture of compounds is introduced into the liquid mobile phase, and this then flows through a packed column containing the stationary solid phase. The contacting scheme is thus differential, but since the adsorption characteristics of the compounds in the mixture are similar, many equivalent theoretical stages are required for their separation. Chromatographic processes are mostly ran under transient conditions, such that... 

Numerous applications of GAs within science and other fields have appeared in the literature references to a few of them are given at the end of this chapter. The method has been used for computer learning, modeling of epidemics, the scheduling of the production of fine chemicals, the prediction of the properties of polymers, spectral analysis, and a wide variety of other investigations. In this section we consider a few examples of recent applications in chemistry. 

For application in flow reactors the nanocarbons need to be immobilized to ensure ideal flow conditions and to prevent material discharge. Similar to activated carbon, the material can be pelletized or extruded into millimeter-sized mechanically stable and abrasion-resistant particles. Such a material based on CNTs or CNFs is already commercially available [17]. Adversely, besides a substantial loss of macroporosity, the use of an (organic) binder is often required. This material inevitably leaves an amorphous carbon overlayer on the outer nanocarbon surface after calcination, which can block the intended nanocarbon surface properties from being fully exploited. Here, the more elegant strategy is the growth of nanocarbon structures on a mechanically stable porous support such as carbon felt [15] or directly within the channels of a microreactor [14,18] (Fig. 15.3(a),(b)), which could find application in the continuous production of fine chemicals. Pre-shaped bodies and surfaces can be... 

The greenhouse gas CO2 is a valuable and renewable carbon source for the production of fine chemicals and fuels because it is readily... 

Figure 1.4 Number of biotransformations used catagorised by industrial sector (based on 134 processes). (Reprinted from Straathof Panke, S. and Schmid, A. The production of fine chemicals by biotransformations. Curr. Opin. Biotechnol. 2002, 13, 548-556 with permission from Elsevier.)...

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