Microchannels processing

Medium- to large-scale microchannel processes offer tremendous economically promising advantages in the chemical and energy process industries, and many such demonstrations are underway. Moving from one charuiel to tens of thousands... 

The reaction requires the formation of enolates that by themselves are one of the most profound spedes enabling C—C bond formation [15]. Reducing processing time is a driver for microchannel processing of aldol readions [15] that can be accomplished using reactive readants such as silyl enol ethers. For example, the reaction between 4-bromobenzaldehyde and the silyl enol ether of acetophenone was performed in a microreactor [15]. 

Tonkovich, A.Y., Perry, S., Wang, Y., Qiu, D., LaPlante, T., and Rogers, W.A. MicroChannel process technology for compact methane steam reforming. Chemical Engineering Science, 2004, 59 (22-23), 4819. 

This chapter overviews ongoing activities in microchannel process technology development, from single-channel laboratory experiments to industrially-driven, multi-channel and multi-unit development at or near the prototype and pilot level. The non-reactive unit operations covered include heat transfer, mixing, emulsification, phase separation, phase transfer, biological processes, and body force applications. 

Given the two microporous processing options, their comparison can be summarized as in Fig. 7.9 [109]. Generally speaking, membrane emulsification provides higher flux and smaller droplet sizes than the microchannel process. Microchannels, however, are less susceptible to fouling, require little or no... 

G. N. fovanovic. Industrial applications of microchannel process tehnology in the United States, in Advanced Micro and Nanosystems. Vd. 5. Micro Proems Engineering, ed. N. Kockmann, Wiley-VCH Verlag GmbH, Weinheim, 2006, Chapter 13. 

Process development was accomplished in single-run reactions [31]. The conversion of the microchannel processing typically amounted to about 50-75%, depending on the nature of cycloadduct and the residence time chosen, and was comparable to batch syntheses results [31], By combinations of aldehydes and 1,3-diketones, different cycloadducts were generated simultaneously in one run on one chip, that is, an undesired transfer of solutions from one channel to another by imperfect sealing between these channels. The conversions were comparable to the single runs, with one exception. Also, cross-contamination was observed. It ranged from a few percent to about 50%. 

While the manifolds were fabricated by a plain molding process, the microchannels substrate fabrication was quite complicated and was achieved by a multistage process. The following main stages were used in the process (1) double side oxidation of a 525 pm (1 0 0) silicon substrate to 1,000 A, (2) single side 1,200 A silicon nitride deposition, (3) silicon nitride channels template opening by reactive... 

Microstructures on Macroscale MicroChannel Reactors for Medium- and Large-Size Processes... 

Background on Medium-to Large-Scale Processes in Microchannels... 

Figure 11.1 Scale-up versus numbering up for microchannels. All critical channel dimensions remain constant in a microchannel system independent of the overall process capacity.

Heat transfer in laminar single-phase, two-stream microchannels has been well described in the literature [33, 39-41]. The challenge for medium- to large-scale processes is an added complexity if more than two fluids are required and also the micromanifold region. 

Multiple fluid streams in medium- to large-scale processes become important for many oxidation reactions. MicroChannel operation allows safe operation in the explosive regions [42, 43], but this advantage ceases as the dimensions become... 

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