Short contact time reactors

In addition to the disk reactor, short contact times can also be achieved in monolith reactors (Section 1.2.2) and in microchan-nel reactors (Section 1.2.5), the latter involving fluid mechanical 

In addition to their advantages stated earlier, compact dimensions of the microchannel reactors allow inherently safe productions, as the risks associated with reactions (e.g., thermal runaway) are not significant due to the small quantities in the 

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It must be noted that short contact time reactors are typically operated under adiabatic conditions with outlet temperatures of the order of 700-1000 °C. Under such conditions, with respect to other noble metals, Rh is believed to be especially stable due to a low vapor pressure and an increased resistance to carbon formation even under severe operating conditions. The use of low surface area oxides such as (Z-AbO j and ZrO2 as support materials has been reported to improve the catalyst stability by limiting the coarsening of Rh particles while avoiding incorporation of Rh within the oxide structure [148]. 

This new technique incorporates a catalyzed short contact time (SCT) substrate into a shock tube. Fig. 13. These SCT reactors are currently used in industry for a variety of applications, including fuel cell reformers and chemical synthesis.The combination of a single pulse shock tube with the short contact time reactor enables the study of complex heterogeneous reactions over a catalyst for very well defined regimes in the absence of transport effects. These conditions initiate reaction in a real environment then abruptly terminate or freeze the reaction sequence. This enables detection of intermediate chemical species that give insight into the reaction mechanism occurring in the presence of the chosen catalyst. There is no limitation in terms of the catalyst formulations the technique can study. 

O. Deutschmann and L.D. Schmidt. Modeling the Partial Oxidation of Methane in a Short-Contact-Time Reactor. AIChE J., 44 2465-2477,1998. 

D.K. Zerkle, M.D. Allendorf, M. Wolf, and O. Deutschmann. Understanding Homogeneous and Heterogeneous Contributions to the Partial Oxidation of Ethane in a Short Contact Time Reactor. J. Catalysis, 196 18-39,2000. 

Chloroprene is of high industrial importance for manufacture of synthetic rubbers. For a long time the synthesis was based on acetylene. More recent processes are based on butadiene as a feedstock, which is substantially cheaper [29]. The initial step is a gas-phase free-radical chlorination at 250 °C and temperature control is ensured by use of excess butadiene (molar ratio of Cl2 to butadiene 1 5 to 1 50) [44]. To limit side reactions, short contact time reactors operating at higher temperatures and residence times below one second are also known [45], Good mix-... 

L. D. Schmidt, Steam Reforming of Methane and Water Gas Shift in Short Contact Time Reactors. AIChEf, 2003, 49,1277-1284. 

Short-contact-time reactor Catalytic and noncatalytic operations Useful for kinetic measurements when solid is a reactant. Leakage can be problem Representative product sampling and parameter... 

Several types of FCC testing equipment are described in literature, varying from the more traditional standardized micro activity test (MAT) and fluidised bed reactors to complete riser-regenerator combinations. Also other designs such as a pulse reactor, or a very short contact time reactor have been reported in literature (7-9). 

Until recently only a few papers were available on moving beds in cross flow [11-18]. This type of reactor is sometimes a favorable process solution for a selective catalytic process with a moderate catalyst rcsidence time and with a short gas residence time, especially when the process is accompanied by a continuous catalyst regeneration. The use of conventional short-contact-time reactors like fluidized-bed reactors, risers, and fixed-bed reactors does not always yield satisfactory results. This may be explained by problems connected with gas back-mixing, channeling of gas, low catalyst holdup, attrition of the solid catalyst, or difficulties in temperature control. 

Deutschmann, O. and Schmidt, L.D. Two-dimensional modeling of partial oxidation of methane on rhodium in a short contact time reactor. Proceedings of the International Symposium on Combustion, 1998, 2, 2283. 

Deutschmann, O., Schmidt, L.D., and Warnatz, J. Detailed modelling of short-contact-time reactors. Recents Progres en Genie des Precedes, 1999, 13, 213. 

Beretta A, Forzatti P (2004) Partial oxidation of light paraffins to synthesis gas in short contact-time reactors. Chem Eng J 99 219-226... 

To see how the program runs we will try it out for a radius of 100 units. This makes zmax only 10 units. Such a reactor would be odd to find because it would have an aspect ratio of L D 1 200. Run at very high volume flow rates, that is, high Uj, units of this kind are called short contact time reactors because the gases are within the reactor volume for so little time. In the present case that time is not short—it is on the order of 100 =... 

High yield of olefins and hydrogen from decane in short contact time reactors rhodium versus platinum. /. Catal, 222, 429 38. 

Schneider A, Mantzaras J, Jansohn P Experimental and numerical investigation of the catalytic partial oxidation of mixtures diluted with and in a short contact time reactor, Chem Eng Sci 61 4634-4649, 2006. 

As mentioned above, in recent years several other authors have studied and made contributions to the better comprehension of the oxidative dehydrogenation of Ught paraffins in short contact time reactors. 

Beretta, Forzatti and co-workers also studied the oxidative dehydrogenation of ethane and propane in short contact time reactors. Experiments were first performed in an isothermal, single channel reactor with an annular configuration (wherein the fluodynamics were simple, mass transfer coefficients were known and catalyst temperature was well controlled and easily measured, as illustrated in the following) the comparison between the results obtained in the absence of the catalyst with those obtained with increasing amounts of catalyst confirmed that olefins were uniquely produced via gas-phase reactions, while the Pt/Al203 catalyst was a non-selective oxidation catalyst (producing only COx, H2 and H2O). 

It was thus proposed that in autothermal short contact time reactors, once the fuel-rich feed stream is fed, heterogeneous deep oxidation reactions are initially aetivated they, in turn, heat up the gas-phase volume which surrounds the catal3hic surface and induce the thermal activation of a homogeneous process. 

Zwerkle, D., Allendorf, M., Wolf, M., et al. (2000). Understanding Homogeneons and Hetero-geneons Contribntions to the Platinum-Catalyzed Partial Oxidation of Ethane in Short-Contact-Time Reactors, J. Catal., 196, pp. 18-32. 

Beretta, A. and Forzatti, P. (2001), Catalyst-Assisted Oxidative Dehydrogenation of Light Paraffins in Short Contact Time Reactors, in J. Spivey, E. IglesiaandT.Fleisch(eds), Aafara/ Gas Conversion VI (Smdies in Surface Science and Catalysis 136), Elsevier, Amsterdam, pp. 191-196. 

Donsi, R, Pirone, R. and Russo, G. (2004). Catalyst Investigation for Apphcations of Oxidative Dehydrogenation of Ethane in Short Contact Time Reactors, Catal. Today, 91-92, pp. 285-288. 

Kraemer, D.W., Larocca, M. and de Lasa, H.L, "Deactivation of Cracking Catalysts in Short Contact Time Reactors Alternative Models", Can. J. of Chem. Eng., accepted for publication (1990b). 

Marschall K-J, Mleczko L. Short-contact time reactor for catalytic partial oxidation of methane. Ind Eng Chem Res 1999 38 1813-21. 

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