In tube reactor

Fig. 22. Schematics of chemical vapor deposition epitaxial reactors (a) horizontal reactor, (b) vertical pedestal reactor, (c) multisubstrate rotating disk reactor, (d) barrel reactor, (e) pancake reactor, and multiple wafer-in-tube reactor (38).

Table IX lists the substances included in this study. The general conditions are given in Table X. Each impurity was added separately to the gas mixture and passed over C150-1-03 in order to determine its effect on catalyst activity. These tests were run under the primary methanation conditions, but in a small 3/8-in. tube reactor on sized, 10 X 12 mesh, catalyst.

In the following we present a detailed model of the commercial, multiple-wafer-in-tube reactor illustrated in Figure 2. We have selected the LPCVD as an example because of its central role in the microelectronics industry and because it nicely demonstrates the analogies to heterogeneous catalytic reactors, in particular the fixed bed reactor. 

The safety technical assessment of continuous CSTR processes and discontinuous processes performed in batch or semibatch reactors is of special importance. In the case of reactions conducted in tube reactors the amoimt of substance is comparatively smaller. On the other hand, reactions performed in such tube reactors are often very complex catalytic equilibrium processes, which need an individual evaluation for an adequate safety assessment. Generalizations are hardly possible. 

The abihties of the tube-in-tube design was further expanded by Buba et al. (2013EJOC4509). For the synthesis of the oxazolidinone 36, formaldehyde was used in the gaseous state by heating paraformaldehyde to 80 °C. The tube-in-tube reactor needs to be kept at a temperature higher than 80 °C to prevent polymerization and subsequent precipitation of paraformaldehyde onto the membrane surface. Formaldehyde reacted with Fmoc-protected alanine 35 in the presence of a catalytic amount ofp-tolue-nesulfonic acid in acetonitrile to achieve N-Fmoc-L-4-methyl-oxazohdin-5-one 36 in excellent yield (91% Scheme 9) (2013EJOC4509). 

However, the tube-in-tube reactor is not only used for gas—hquid reactions. The group of Kappe used the gas-permeable membrane to prepare the highly toxic and explosive diazomethane (CH2N2) in a safe manner. The diazomethane was formed from N-methyl-JV-nitroso-p-toluenesulfona-mide (Diazald) and KOH in the inner channel of the microreactor and subsequently diffused through the hydrophobic membrane where it formed the desired products 38, 40, and 42 in the outer chamber. The potential... 

Scheme 9 Flow tube-in-tube reactor used for the synthesis of oxazolidinones.

In tube reactors with laminar flow profiles, the axial dispersion coefficient (D) is related to the molecular diffusion coefficient (Dm), the average flow velocity, and the tube diameter (d) ... 

Figure 7. By-product formation (1 — if) in sulfonation of 30 vol % benzene in 1,2-dichloroethane at 20°C, as a function of ki, as measured with the system Ot-CO -hydroxide. (O) in cyclone reactor, (A) in tube reactor.

Gonzales, M. A., Ciszewski, J. T. (2009). High conversion, solvent Free, continuous synthesis of imidazolium ionic liquids in spinning tube-in-tube reactors. Org. Process Res. Dev., 13,1, (December 2008) 64-66, ISSN 1083-6160... 

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