Reactions supercritical fluid

In the last few years, an increasing trend towards new high pressure applications could be observed in R D, all of them in a certain way taking advantage of the remarkable properties of fluids at near critical or supercritical conditions. At the same time the demand for high pressure pilot units for these new" applications like Supercritical Fluid Reactions, HP-Micronization, HP-Spray Drying and HP-Sterilization increased. In order to also supply customized... 

Phase and Reaction Equilibria Considerations in the Evaluation and Operation of Supercritical Fluid Reaction Processes... 

In the following sections some aspects of (potential) applications of sc-fluids in the fine chemical industry with respect to product separation/purification and catalytic reactions are discussed. Earlier industrial applications of supercritical fluid reactions, for example the Haber-Bosch process for the synthesis of ammonia, synthesis of methanol from hydrogen and carbon monoxide, or the polymerization of ethene will not be discussed. An extensive overview on the use of sc-fluids in the synthesis of bulk chemicals is given in the book edited by fessop and Leitner [12],... 

As mentioned in the Introduction, sc-fluids find increasing use as reaction media. By exploiting the solvent properties of sc-fluids, it is possible to enhance reaction rates or improve selectivity. Especially in cases, where mass transfer problems are limiting, for example reaction rates or selectivities, the special properties of the supercritical state may circumvent these difficulties. To use the advantages of sc-fluids in reaction mediiun, it is necessary to have information on the phase behavior that is exhibited by the reaction mixture. Supercritical fluids have been used as solvents for various inorganic/organic reactions [35]. However, only a few examples (see Introduction) of the application of sc-fluids in supercritical fluid reactions (SFR) have been described. From an industrial point of view, the potential of many of the described reactions could not be realized, because there are not enough details for the development and transformation of the reaction to a tech-... 

Several other chemists were active in the field of supercritical fluid reactions at the beginning of the twentieth century. For example, Briner studied the decomposition and reactivity of supercritical fluids such as scNO and scCO (e.g., eq 1.1-6) [119-122]. He also investigated the system N2-H2 and reported that N2 and H2 do not combine at room temperature and 900 bar [122]. At the Chemical Institute of the University of Berlin, Arthur Stabler studied the reactions of alkyl halides such as chloroethane with SCNH3 (eq 1.1-7) [123]. One of the earliest attempts to utilize SCFs for the selective synAesis of low molecular weight organic products dates to the early 1940s, when Patat at the University of Innsbruck studied the hydrolysis of aniline under supercritical conditions (eq 1.1-8) [124]. 

These alternative reactor technologies can be combined with Green Chemistry methods including, for example, catalytic membrane reactions and continuous flow supercritical fluid reactions. 

In this chapter, we shall explore why several unit operations using critical fluids, separately or coupled, are frequently needed to produce a desired end product. Figure 1 depicts several process sequence possibilities that could use supercritical fluids for isolating or synthesizing the desired end products. SFE can be used to directly produce extracts or products. For example, the SFE of coffee beans results in a product that has been decaffeinated [1] for consumer use, while alternatively SFE can produce an extract from hops [2] that has commercial utility. However, such ideal scenarios are the exception to the rule, and more recently other applications of supercritical fluids have been explored which utilize supercritical fluid fractionation (SFF) or supercritical fluid reactions (SFR) to affect the desired end result. 

To provide some examples of utilizing supercritical fluid reactions (SFR) for the conversion of agrimaterials, we shall cite studies on the conversion of lipid-based materials of agricultural origin. Parameters which impact on converting lipid-based substrates in critical fluid media are tabulated below ... 

Elbashir NO, Bukur DB, Durham E, Roberts CB. Advancement of Fischer-Tropsch synthesis via utilization of supercritical fluid reaction media. AIChE J. 2010 56 997-1015. 

R 637 M. Nakahara, Roles of Supercritical-Fluid Reactions for 2F Century Energy Problems. Synthesis of Dimethyl Ether and Hydrogen , Chor-inkai Saishin Gijutsu, 2004,8,30... 

Supercritical fluids as phase homogenisers. Applications of supercritical fluid reaction media which arise from the superior solvation of some species in this phase in comparison to either liquids or gases are considered in this section. Cases in which the concentration of key reagents or catalysts is boosted or controlled at a specified level are discussed, as is the removal of unwanted by-products, which would otherwise poison or foul a reaction catalyst. 

The breadth and quantity of papers presented in this chapter illustrate the rapidly increasing level of active research and development in this exciting field of supercritical fluid reactions. The now successM commercialization of SCF reaction processes and the ongoing construction of others will further reduce technical and financial uncertainties about investment in this technology. Thus, SCF media for conducting chemical transformations will Ukely achieve greater acceptance for manufacturing operations in future applications. 

S Saim, DM Ginosar, B Subramaniam. Phase and reaction equilibria considerations in the evaluation and operation of supercritical fluid reaction processes. In KP Johnston, JML Penninger, eds. Supercritical Fluid Science and Technology. ACS Symposium Series No. 406. Washington, D.C. American Chemical Society, 1989, pp 301-316. 

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