Catalytic Microreactors

We have studied the steady-state kinetics and selectivity of this reaction on clean, well-characterized sinxle-crystal surfaces of silver by usinx a special apparatus which allows rapid ( 20 s) transfer between a hixh-pressure catalytic microreactor and an ultra-hixh vacuum surface analysis (AES, XPS, LEED, TDS) chamber. The results of some of our recent studies of this reaction will be reviewed. These sinxle-crystal studies have provided considerable new insixht into the reaction pathway throuxh molecularly adsorbed O2 and C2H4, the structural sensitivity of real silver catalysts, and the role of chlorine adatoms in pro-motinx catalyst selectivity via an ensemble effect. 

Veser G., Experimental and theoretical investigation cf H2 oxidation in a high-temperature catalytic microreactor, Chem. Eng. Sd. 56 (2001) 1265-1273. 

Ehreeld, W., Gebauer, K., Lowe, H., Richter, T., Synthesis of ethylene oxide in a catalytic microreactor system. Stud. 

The point is also made [134] that the very high surface areas and the richly interconnected three-dimensional networks of these micron-sized spaces, coupled with periods of desiccation, could together have produced microenvironments rich in cat-alytically produced complex chemicals and possibly membrane-endosed vesides of bacterial size. These processes would provide the proximate concatenation of lipid vesicular precursors with the complex chemicals that would ultimately produce the autocatalytic and self-replicating chiral systems. A 2.5 km2 granite reef is estimated to contain possibly 1018 catalytic microreactors, open by diffusion to the dynamic reservoir of organic molecules. .. but protected from the dispersive effects of flow and convection [134] as well as protected from the high flux of ultraviolet radiation impinging on the early Earth. [123,137]... 

Yube, K. and Furuta, M. and Mae, K. (2007). Selective oxidation of phenol with hydrogen peroxide using two types of catalytic microreactor, Catalysis Today, 125, 56-63. 

In addition to the harmonization of the underlying physical and chemical processes, the catalytic-plate heat exchanger offers a cost-effective alternative to both conventional multitubular reactors and catalytic microreactors for industrial... 

Kusakabe, K., Miyagawa, D., Gu, Y., Maeda, H., Morooka, S., Development of a self-heating catalytic microreactor, in Matlosz, M., Ehrfeld, W., Baselt, J. P. (Eds.), Microreaction Technology -IMRET 5 Proc. of the 5th International Conference on Microreaction Technology, Springer-Verlag, Berlin, 2001, 70-77. 

Grunwaldt J-D, Hannemann S, Schroer CG, Baiker A. 2D-Mapping of the catalyst structure inside a catalytic microreactor at work partial oxidation of methane over RI1/AI2O3. J Phys Chem B. 2006 110 8674. 

A conventional pulse catalytic microreactor was used with 15-65 mg of the catalyst for the cumene runs and 65 mg for the 2,3-dimethylbutane runs. The catalyst was held between 2 small plugs of borosilicate glass wool in a 5-mm ID diameter borosilicate reactor. In some experiments, the catalyst was diluted with 96% silica porous glass powder. The helium gas was purified by passage through alumina kept at liquid nitrogen temperature. The reaction temperature was measured by a thermocouple located adjacent to the reactor. The catalyst was pretreated at the desired temperature for 16 hours in a stream of helium. The products were analyzed with a dioctyl phthalate gas chromatography column at llO C. 

If no commercial catalyst is available, it may still be advantageous to separate catalyst optimization from development of a coating procedure. Such an approach was pursued by Schwarz et al. [178] in the development of a catalytic microreactor for the partial oxidation of propane. In a first step, a VOY/ A1203 catalyst was developed. A commercially available Y-AI2O3 powder consisting of particles 3 pm in diameter was chosen as the support material, mixed with various amounts of vanadyl acetylace-tonate and suspended in methanol. After drying and calcination, the resultant material was characterized and its catalytic activity and selectivity for the partial oxidation of propane was determined. The optimized catalyst was resuspended in an alcoholic solution, mixed with binders, and coated onto a stainless steel MSR. 

Figure 11.2 Schematic of the fixed-bed catalytic microreactor. The gaseous effluent is continuously analyzed using an FTIR spectrometer equipped with a gas cell...

Catalytic activity studies were carried out using a typical catalytic microreactor. Catalyst sample sizes were 0.5g for CO oxidation studies and 2.0g for n-propane oxidation studies. Flow rates of tlie gas mixtures, which varied from stiochiometric to oxygen-rieh, were in the range 90-100 ml min T Table 3 summarises the activity of selected Sn-Cu-0, Sn-... 

Detailed investigation of the reaction mechanism was performed using a TAP reactor (Autoclave Engineers). Both the TAP apparatus and technique have been described in detail by the inventors [7,8], and otdy those aspects most relevant to this study will be included here. The system comprises four main features (i) a valve assembly which permits the introduction of either a very narrow gas pulse or a continuous flow, (ii) a catalytic microreactor, (iii) a high vacuum system, (iv) a quadrupole mass spectrometer. 

T. Eukuda, T. Maid, K. Mae, Design of a plate-type catalytic microreactor with CO2 permeation membrane for water-gas shift reaction, Chem. Eng. Technol. 35 (2012) 1205-1213. 

The small dimensions in microreactors imply the presence of laminar flow. This type of flow makes it easier to extract chemical kinetic parameters and fully characterize phenomena. The correct incorporation of the active catalyst onto the surface of the membrane is one of the important aspects of catalytic microreactors. Drott et al. (1997) investigated the use of porous silicon as a carrier matrix in microstructured enzyme reactors. The matrix was created by anodization and the fabrication of the microreactor used flow-through silicon cell comprising 32 channels of 50 pm wide, 250 pm deep and separated by 50 pm. The aim was to increase the surface area on which the enzymes (glucose oxidase) could be coupled. Comparisons were made with the classical non-porous reference device and the glucose turnover rates. The results showed that when compared with the reference reactor the enzyme activity increased 100-fold. 

Levent M, Gunn D J and El-Bousiffl M A (2003) Production of hydrogen-rich gases from steam reforming of methane in an automatic catalytic microreactor , Int J Hydrogen Energy, 28,945-959. 

Figure 2.14 Flow distributor arrangement for catalytic microreactor according to Rebrov et al. [29], The header consists of a cone diffuser and a thick-walled screen positioned in front of the microreactor.

The organization of this chapter is as follows. First, the existence of spatial gradients is discussed, then the effect of radiation is addressed. Transverse transport correlations are elucidated and subsequently applications from gas-phase micro-bumers and catalytic microreactors are presented. Finally, conclusions are drawn. 

S. Karagiannidis, J. Mantzaras, G. Jackson, K. Boulouchos, Hetero-/homogeneous combustion and stability maps in methane-fueled catalytic microreactors, Proc. Combust. Inst., 2007, 33, 1973-1981. 

T. Kim, S. Kwon, Design, fabrication and testing of a catalytic microreactor for hydrogen production, /. Micromech. Microeng. 2006, 16, 1760-1768. 

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