Chemical synthesis, flow reactor

The development of ammonia synthesis represents a landmark in chemical engineering, as it was the start of large-scale, continuous high-pressure operation in flow reactors, and in catalysis, because the numerous tests of Mittasch provided a systematic overview of the catalytic activity of many substances. 

A system has been constructed which allows combined studies of reaction kinetics and catalyst surface properties. Key elements of the system are a computer-controlled pilot plant with a plug flow reactor coupled In series to a minireactor which Is connected, via a high vacuum sample transfer system, to a surface analysis Instrument equipped with XFS, AES, SAM, and SIMS. When Interesting kinetic data are observed, the reaction Is stopped and the test sample Is transferred from the mlnlreactor to the surface analysis chamber. Unique features and problem areas of this new approach will be discussed. The power of the system will be Illustrated with a study of surface chemical changes of a Cu0/Zn0/Al203 catalyst during activation and methanol synthesis. Metallic Cu was Identified by XFS as the only Cu surface site during methanol synthesis. 

Miniaturization and parallelization key approaches for drug development apparatus for combinatorial chemistry UHTS 1536 titer-plate format modular construction of apparatus applications of UHTS fine-chemical synthesis by micro reactors numbering-up nature as model general advantages of micro flow vision of plants-on-a-desk [233]. 

D-Pantolactone and L-pantolactone are used as chiral intermediates in chemical synthesis, whereas pantoic acid is used as a vitamin B2 complex. All can be obtained from racemic mixtures by consecutive enzymatic hydrolysis and extraction. Subsequently, the desired hydrolysed enantiomer is lactonized, extracted and crystallized (Figure 4.6). The nondesired enantiomer is reracemized and recycled into the plug-flow reactor [33,34]. Herewith, a conversion of 90-95% is reached, meaning that the resolution of racemic mixtures is an alternative to a possible chiral synthesis. The applied y-lactonase from Fusarium oxysporum in the form of resting whole cells immobilized in calcium alginate beads retains more than 90% of its initial activity even after 180 days of continuous use. The biotransformation yielding D-pantolactone in a fixed-bed reactor skips several steps here that are necessary in the chemical resolution. Hence, the illustrated process carried out by Fuji Chemical Industries Co., Ltd is an elegant way for resolution of racemic mixtures. 

Microreactors (flow reactors with micrometer scale) were first employed in organic synthesis to perform chemical reactions in flow processes. The small dimensions of microreactors allow the use of minimal amounts of reagent under precisely controlled conditions, and the rapid screening of reaction conditions with improved overall safety of the process. To obtain synthetically useful amounts of material, either the microreactors are simply allowed to run for a longer period of time ( scale-out ), or several reactors are placed in parallel ( numbering up ) [29],... 

As indicated in the introduction of Section 2.2.2, continuous flow reactors (generally fixed bed reactors) are not frequently used in the investigation of the liquid phase zeolite catalysed synthesis of Fine Chemicals. However, fixed bed reactors present some significant advantages on batch reactors ... 

Explorations of new electrochemical routes to traditional as well as specialty chemicals via electro-organic synthesis have given rise to a search for more efficient electrochemical reactors. The radial flow reactors or cells show promise compared to the conventional parallel plate configurations. A typical radial flow reactor is schematically shown in Fig. 39, which includes the... 

Supercritical fluids, particularly supercritical C02, scC02, are attractive solvents for cleaner chemical synthesis. However, optimisation of chemical reactions in supercritical fluids is more complicated than in conventional solvents because the high compressibility of the fluids means that solvent density is an additional degree of freedom in the optimisation process. Our overall aim is to combine spectroscopy with chemistry so that processes as varied as analytical separations and chemical reactions can be monitored and optimised in real time. The approach is illustrated by a brief discussion of three examples (i) polymerisation in scC02 (ii) hydrogen and hydrogenation and (iii) miniature flow reactors for synthetic chemistry. 

Jonczyk, A. and Meienhofer, J. (1983) Automated flow reactor synthesizer for fast synthesis of peptides using Emoc protection. In Peptides Structure and Function, Proc.S.APS (Hruby, V. J. and Rich, D. H., eds.). Pierce Chemical Company, Rockford, IL, pp. 15-11. 

There has been eonsiderable recent interest in partial oxidation of alkanes for new routes to chemical synthesis from light alkanes, and this research has been summarized extensively[l-3]. While much of this research uses dilution and low flow rates to attain temperatures between 200 and 600°C, another mode of operation involves very short contact times with no dilution to increase the temperature to -1000°C and decrease the catalyst contact time to 1 milUsecond. Recent research with millisecond adiabatic reactors have been carried out by Green et al[4], Lunsford et al[5], Choudhary et al[6], and many other research groups. 

Kuczynski, M., The synthesis of methanol in a gas-solid-solid trickle flow reactor. Ph.D. Thesis in Chemical Engineering, University of Twente, Enschede, The Netherlands, 1986. 

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