Laboratory microreactors

Figure 1. Comparison of a laboratory microreactor and envisioned industrial reactor for ammonia synthesis.

The catalysts were tested for CO oxidation using a fixed-bed laboratory microreactor (3 mm id), operated at atmospheric pressure. Typically CO (0.5% CO in synthetic air) were fed to the reactor at controlled rates of 22.5 ml min using mass flow controllers and passed over the catalyst of 50 mg (GHSV =... 

In a typical bench scale experiment a first generation Bi PMo 2 52 catalyst produces 65.2% per pass propylene conversion to acrylonitrile with 4.1% HCN, 4.0% acetonitrile, 0.1% acrolein, and 16 8% CO2 (Table 3). Yields of useful products have been greatly improved with newer generation catalyst systems. Advancement of new catalyst systems progresses in several stages, eventually resulting in a 30 million-fold scale-up from a 5-gram laboratory microreactor to a 26 ft. diameter commercial reactor (Table 4). 

Upon reflection, one concludes that it is rather unlikely that individual laboratory microreactors will be coimected in this way in industrial designs. More likely is that large-scale macro-devices will be created with internal microstructuring and it is not evident that such devices will truly operate under identical conditions at all points in the intercoimected structure. Numbering-up is therefore not the complete answer to the scale-up problem, but it does provide a stimulating model for a totally new way to design and construct reactor devices. 

A differential PFR is a laboratory microreactor operated at very low fractional conversions of reactant(s), preferably not... 

Figure 9.29 Reduction of reaction times by as given in Ref. [119]) as compared to standard several orders of magnitude using a falling film organic laborato processing with a laboratory microreactor (FFMR) or micro bubble columns bubble column (LBC). x residence time. Source (MBC I and II, denoting different dimensions, By courtesy of I MM.

Microwave technology has now matured into an established technique in laboratory-scale organic synthesis. In addition, the application of microwave heating in microreactors is currently being investigated in organic synthesis reactions [9-11] and heterogeneous catalysis [12, 13]. However, most examples of microwave-assisted chemistry published until now have been performed on a... 

In this way, the operational range of the Kolbe-Schmitt synthesis using resorcinol with water as solvent to give 2,4-dihydroxy benzoic acid was extended by about 120°C to 220°C, as compared to a standard batch protocol under reflux conditions (100°C) [18], The yields were at best close to 40% (160°C 40 bar 500 ml h 56 s) at full conversion, which approaches good practice in a laboratory-scale flask. Compared to the latter, the 120°C-higher microreactor operation results in a 130-fold decrease in reaction time and a 440-fold increase in space-time yield. The use of still higher temperatures, however, is limited by the increasing decarboxylation of the product, which was monitored at various residence times (t). 

Taghavi-Moghadam, S., Golbig, K., Microreactors application of CYTOS -technology from laboratory to production scale, MST News 3 (2002) 36-38. 

Stainless steel is the material of choice for process chemistry. Consequently, stainless steel microreactors have been developed that include complete reactor process plants and modular systems. Reactor configurations have been tailored from a set of micromixers, heat exchangers, and tube reactors. The dimensions of these reactor systems are generally larger than those of glass and silicon reactors. These meso-scale reactors are primarily of interest for pilot-plant and fine-chemical applications, but are rather large for synthetic laboratories interested in reaction screening. The commercially available CYTOS Lab system (CPC 2007), offers reactor sizes with an internal volume of 1.1 ml and 0.1 ml, and modular microreactor systems (internal reactor volumes 0.5 ml to... 

Multiphase catalytic reactions, such as catalytic hydrogenations and oxidations are important in academic research laboratories and chemical and pharmaceutical industries alike. The reaction times are often long because of poor mixing and interactions between the different phases. The use of gaseous reagents itself may cause various additional problems (see above). As mentioned previously, continuous-flow microreactors ensure higher reaction rates due to an increased surface-to-volume ratio and allow for the careful control of temperature and residence time. 

Hessel V, Hofmann C, Lob P, Lohndorf J, Lowe H, Ziogas A (2005) Aqueous Kolbe-Schmitt synthesis using resorcinol in a microreactor laboratory rig under high-P,T conditions. Org Process Res Dev 9 479-489 Inoue T, Schmidt MA, Jensen KF (2007) Microfabricated multiphase reactors for the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Ind Eng Chem Res 46 1153-1160... 

Fig. 12. Cylindrical falling film microreactor for pilot operation at tenfold capacity increase as compared to the laboratory falling film microreactor...

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