Primary screening reactor

Primary Screening Massively Parallel Microfluidic Reactor... 

Although the direct oxidation of ethane to acetic acid is of increasing interest as an alternative route to acetic acid synthesis because of low-cost feedstock, this process has not been commercialized because state-of-the-art catalyst systems do not have sufficient activity and/or selectivity to acetic acid. A two-week high-throughput scoping effort (primary screening only) was run on this chemistry. The workflow for this effort consisted of a wafer-based automated evaporative synthesis station and parallel microfluidic reactor primary screen. If this were to be continued further, secondary scale hardware, an evaporative synthesis workflow as described above and a 48-channel fixed-bed reactor for screening, would be used. 

Acrylonitrile is commercially produced from propylene by a molybdate-based catalyst that has been optimized to produce a yield of around 80% acrylonitrile. Utilizing a less-expensive feedstock, the selective ammoxidation of propane to acrylonitrile has significant potential in reducing acrylonitrile production cost. The work-flow for this chemistry consisted of a primary scale evaporative synthesis station and 256-channel parallel screening reactor using a proprietary optical-based detection method. For the initial work shown here, secondary screening was done on a six-channel fixed-bed reactor. 

At a reactor temperature of 300 °C the temperature gradient between reactor centre and edge was about 40 °C and thus not acceptable. Different heat sources had been studied. The best solution proved to be a commercial heating plate used in Ceran top stoves. For libraries of 10 cm diameter a heating plate of 1,2 kW and outer diameter of 17 cm has been used. This heat source heats an air pad, which in turn heats the reactor bottom mounted above the heater (see Fig. 7.9 below). With this setup the temperature gradient has been reduced to <4°C at 300 °C (Fig. 7.3), which was found acceptable for a primary screening technique. 

Cons Some technical limitations still exist, such as (1) the small amount of materials generally prepared for primary screenings may lead to difficulties in reproducing exactly a formula and (2) the lack of efficient solid handling from the preparation vessels to the parallel reactors, which may involve manual steps within the iterative loop. The main issue related to the automated synthesis lies... 

Figure 3.12 High-throughput batch reactor used as primary screen for the discovery of aniline cataloreactants. The reactor consists of a circular block with an array of 15 x 10 catalysts [45] (by courtesy of Elsevier Ltd ).

Micro structured wells (2 mm x 2 mm x 0.2 mm) on the catalyst quartz wafer were manufactured by sandblasting with alumina powder through steel masks [7]. Each well was filled with mg catalyst. This 16 x 16 array of micro reactors was supplied with reagents by a micro fabricated gas distribution wafer, which also acted as a pressure restriction. The products were trapped on an absorbent plate by chemical reaction, condensation or absorption. The absorbent array was removed from the reactor and sprayed with dye solution to obtain a color reaction, which was then used for the detection of active catalysts by a CCD camera. Alternatively, the analysis was also carried out with a scanning mass spectrometer. The above-described reactor configuration was used for the primary screening of the oxidative dehydrogenation of ethane to ethylene, the selective oxidation of ethane to acetic acid, and the selective ammonoxidation of propane to acrylonitrile. 

Ni-Ta-Nb oxide catalysts also show high activity for the conversion of ethane to ethylene in primary screening tests. For further optimization bulk catalysts were prepared to perform secondary screening in an 48-channel fixed-bed reactor at 300 °C (see Table 3.4).The highest selectivity (86%) for ethylene was achieved with an Nio.62Tao.ioNbo.28°x catalyst [7]. 

Men, Y, Kolh, G, Zapf, R, Hessel, V, Lowe, H. Selective methanation of carbon oxides in a microchannel reactor—Primary screening and impact of additives. Catal. Today 2007 125 81-87. 

Zech, T., Klein, J., Schunk, S.A., lohann, T., Schiith, R, Kleditzsch, S., and Deutschmann, O. Miniaturized reactor concepts and advanced analytics for primary screening in high-throughput experimentation, la High Throughput Analysis A Toolfor Combinatorial Materials Science, PotyraUo, R.A. and Amis, E.J., Eds. Kluwer Academic/Plenum Publishers Dordrecht, 2003. 

Reactor up-scaling during the screening process, for example from primary leads to secondary process parameter screening, is facilitated if a flexible combination of meso- and micro-scale reactors could be used in the same experimental set-up. 

Wastewater treatment systems can be classified, in addition to pretreatment, as preliminary, primary, secondary, and tertiary (advanced) treatments. Pretreatment of industrial wastewater is required to prevent adverse effects on the municipal wastewater treatment plants. Preliminary treatment is considered as any physical or chemical process that precedes primary treatment. The preliminary treatment processes may consist of influent screening and grit removal. Its function is mainly to protect subsequent treatment units and to minimize operational problems. Primary treatment is defined as the physical or chemical treatment for the removal of settleable and floatable materials. The screened, degritted raw wastewater from preliminary treatment flows to the primary clarification tanks, which are part of the primary treatment facilities. Secondary wastewater treatment is the process that uses biological and chemical treatment to accomplish substantial removal of dissolved organics and colloidal materials. The secondary treatment facilities may be comprised of biological reactor and secondary clarification basins. Tertiary (advanced) wastewater treatment is used to achieve pollutant reductions by methods other than those used in primary and secondary treatments. The objective of tertiary wastewater treatment is to improve the overall removal of suspended solids, organic matter, dissolved solids, toxic substances, and nutrients. 

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